Neurulation and Neural Tube Formation
Neurulation and neural tube formation are critical processes in vertebrate embryonic development that lay the foundation for the creation of the central nervous system (CNS). These processes intricately shape and transform the embryonic tissue, setting the stage for the formation of the brain and spinal cord.
Neurulation
Neurulation is the initial step in the formation of the CNS. It begins with the transformation of the neural plate, a flat sheet of ectodermal tissue, into the neural tube. This transformative process involves several key stages:
Elevation of Neural Folds: As the embryo develops, the neural plate undergoes a process of elevation, forming neural folds on both sides. These folds gradually approach each other along the midline.
Fusion of Neural Folds: The neural folds eventually fuse at the midline, creating a neural tube. This tube becomes the precursor to the brain and spinal cord.
Formation of Neural Crest Cells: Alongside the neural tube formation, a population of cells known as neural crest cells emerge at the borders of the neural plate. These cells play a crucial role in forming various structures, including peripheral nerves, ganglia, and some skeletal elements.
Neural Tube Formation
The neural tube, formed through neurulation, is the rudimentary structure that gives rise to the brain and spinal cord. It undergoes further specialization to create distinct regions of the CNS:
Primary Vesicle Formation: The neural tube initially differentiates into three primary vesicles: the prosencephalon (forebrain), mesencephalon (midbrain), and rhombencephalon (hindbrain).
Secondary Vesicle Formation: These primary vesicles subsequently undergo further differentiation into five secondary vesicles: telencephalon and diencephalon from the prosencephalon, mesencephalon remains unchanged, and metencephalon and myelencephalon from the rhombencephalon.
Cavities and Structure Formation: These vesicles expand and develop specific cavities that become the ventricles of the brain and central canal of the spinal cord. The walls of these vesicles differentiate into the various regions of the CNS.
Neurulation and neural tube formation are critical because they set the foundation for the complex structures and functions of the CNS. These processes ensure the proper development of the brain and spinal cord, which are essential for sensory perception, motor control, cognition, and a myriad of other neurological functions.
How does the neural tube differentiate into distinct regions, such as the brain and spinal cord?
The neural tube, formed through the process of neurulation, gives rise to both the brain and the spinal cord in vertebrate embryos. This remarkable differentiation involves complex molecular signaling and patterning mechanisms that lead to the formation of distinct regions with specific functions.
Formation of Primary Vesicles
After the initial fusion of the neural folds, the neural tube differentiates into three primary vesicles along the anterior-posterior axis: the prosencephalon (forebrain), mesencephalon (midbrain), and rhombencephalon (hindbrain). Each primary vesicle serves as the basis for further differentiation.
Secondary Vesicle Formation and Patterning
These primary vesicles then undergo further differentiation into five secondary vesicles through a process called regionalization:
Telencephalon and Diencephalon (Forebrain): The prosencephalon gives rise to the telencephalon (which develops into the cerebral hemispheres) and the diencephalon (which forms structures like the thalamus and hypothalamus).
Mesencephalon (Midbrain): The mesencephalon remains relatively unchanged and develops into the midbrain structures, including the tectum and tegmentum.
Metencephalon and Myelencephalon (Hindbrain): The rhombencephalon differentiates into the metencephalon (developing into the pons and cerebellum) and the myelencephalon (forming the medulla oblongata).
Patterning Signals and Genetic Regulation
The differentiation of the neural tube into these distinct regions is governed by intricate molecular signaling pathways, including the actions of morphogens such as Sonic Hedgehog (Shh), Fibroblast Growth Factors (FGFs), and Bone Morphogenetic Proteins (BMPs). These signaling molecules establish concentration gradients along the neural tube, instructing cells to adopt specific identities based on their location.
Hox Genes
Hox genes, which play a pivotal role in determining regional identities along the anterior-posterior axis of the body, are also crucial for neural tube differentiation. The expression patterns of Hox genes guide the formation of different segments within the neural tube.
Cellular Migration and Differentiation
As cells within the neural tube receive specific signaling cues, they migrate to their designated regions and differentiate into the diverse cell types that make up the brain and spinal cord.
Patterning and Function
This complex differentiation process ultimately gives rise to the various brain structures and spinal cord segments, each with specialized functions that contribute to sensory perception, motor control, cognition, and other essential neurological processes.
Transverse sections that show the progression of the neural plate to the neural groove from bottom to top 1
At what juncture in the evolutionary timeline are neurulation and neural tube formation postulated to have made their first appearance?
Neurulation and neural tube formation are fundamental embryological processes that lead to the development of the central nervous system (CNS), including the brain and spinal cord. These events are critical for the formation of complex nervous systems and have been conserved across a broad range of vertebrates. Here's a look into their possible evolutionary origins:
Origins of the Nervous System
Simple Nervous Systems: The earliest multicellular organisms would have had rudimentary nervous systems, consisting of simple nerve nets or basic nerve cords. These basic nervous structures wouldn't have required specialized processes like neurulation.
Bilateria and CNS Development: The appearance of bilaterally symmetrical animals, or Bilateria, is a key event in the evolution of the CNS. It is hypothesized that the ancestors of modern bilaterians possessed a centralized nerve cord, which served as a precursor to more advanced nervous systems.
Neurulation and Neural Tube Formation: Neurulation and the formation of a neural tube would have emerged with the need for a more centralized and organized nervous system. This process would have been critical for the development of a dorsal nerve cord in early chordates, which is an ancestral feature of all vertebrates.
Vertebrate Evolution and Neural Tube Specialization
Primitive Chordates: In early chordates like amphioxus, a simple notochord and nerve cord were present. These organisms would have exhibited basic neurulation processes, leading to the formation of a dorsal nerve cord.
Early Vertebrates: With the emergence of early vertebrates, the neural tube would have become more specialized, giving rise to distinct regions such as the forebrain, midbrain, and hindbrain. This differentiation is crucial for the diverse functions and capabilities seen in modern vertebrates.
Neural Crest Cells: Along with the neural tube, the evolution of neural crest cells would have played a pivotal role in vertebrate diversification. These cells originate from the borders of the neural tube and migrate to various parts of the embryo, contributing to structures like cranial bones, peripheral nerves, and more.
The processes of neurulation and neural tube formation are thought to have made their appearance during the evolution of early chordates, setting the stage for the complex nervous systems seen in today's vertebrates. These developmental events would have provided the architectural foundation for advanced neural structures, facilitating sophisticated behaviors and adaptations in vertebrate lineages.
De novo genetic information would to instantiate the processes of neurulation and neural tube formation
Neurulation and neural tube formation are critical stages in the development of the vertebrate central nervous system. They rely on intricate molecular and cellular processes that are guided by various genes and their corresponding proteins. While numerous genes are involved in this complex developmental process, certain genes are recognized as core players in driving neurulation and establishing the neural tube. Here's an overview of some of these crucial genetic components:
Key Genetic Components
Notochord Induction Genes: The notochord, a midline embryonic structure, secretes signaling molecules that instruct the overlying ectoderm to become neural tissue. Genes like Noggin, Chordin, and Follistatin are crucial for this induction, as they inhibit proteins that would otherwise prevent neural differentiation.
Neural Plate Border Specifiers: Genes such as Pax3, Pax7, Msx1, and Zic1 play roles in specifying cells at the border of the neural plate. These border cells can give rise to both neural crest cells and neural tissue.
Neural Fold Elevation and Convergence: As the neural plate forms, it starts to fold, with its edges (neural folds) elevating and moving towards each other. Genes like Shh (Sonic hedgehog) and BMP4 (Bone Morphogenetic Protein 4) play roles in guiding this morphogenesis.
Neural Tube Closure: The eventual fusion of the neural folds to form a closed neural tube is a critical step. Genes such as Celsr1, Vangl2, and Fzd3 are vital components of the planar cell polarity pathway and are instrumental in coordinating the movements of cells during tube closure.
Neural Differentiation and Patterning: Once the neural tube is formed, it undergoes further differentiation and patterning. Genes like Shh and Wnt are involved in ventral and dorsal patterning of the neural tube, respectively, establishing regions that will later give rise to different structures in the CNS.
The process of neurulation and neural tube formation is orchestrated by a myriad of genes working in concert. These genes provide the de novo genetic information necessary for the successful development of the central nervous system. Any disruptions in the function of these genes can lead to neural tube defects, highlighting their critical importance in embryonic development.
Manufacturing codes and languages that would have to emerge and be operational for neurulation and the formation of the neural tube
Neurulation and the formation of the neural tube are intricate processes in embryonic development, driven by a series of tightly regulated molecular and cellular instructions. To understand these "manufacturing codes and languages," one must delve into the complex world of genetic regulation, signaling pathways, and cell-to-cell communications that drive these developmental processes. Here's a glimpse into some of these genetic "codes" and "languages":
Genetic Codes and Regulation
Gene Expression and Transcription Factors: Specific genes are turned on or off during different stages of neurulation. Transcription factors like Sox1, Sox2, and Sox3 are expressed in the early neural plate and are crucial for neural differentiation.
Epigenetic Regulation: Modifications to DNA and its associated proteins can alter gene expression without changing the underlying DNA sequence. Epigenetic changes, such as DNA methylation or histone modifications, are pivotal in determining cell fate during neural tube formation.
Signaling Pathways
Bone Morphogenetic Proteins (BMPs) and Their Antagonists: BMP signaling tends to promote epidermal fates, while its inhibition by molecules like Noggin, Chordin, and Follistatin promotes neural fates.
Sonic Hedgehog (Shh) Signaling: The notochord produces Shh, which plays a crucial role in ventral patterning of the neural tube, determining different neuronal subtypes based on concentration gradients.
Wnt Signaling: Important for dorsal patterning of the neural tube and interacts with other signaling pathways to ensure the right balance of cell types.
Cellular Communication and Interaction
Planar Cell Polarity (PCP) Pathway: This pathway controls the convergent extension movements during neurulation, where cells intercalate and the neural plate narrows and lengthens. Key components include Vangl2, Celsr1, and Fzd3.
Cell Adhesion Molecules: Molecules such as cadherins and integrins play roles in ensuring that cells stick together and move collectively during the bending and folding processes of neurulation.
Neurulation and neural tube formation are orchestrated by a myriad of "manufacturing codes and languages" at the genetic, molecular, and cellular levels. These intricate processes ensure the proper development and functionality of the central nervous system. Any disruptions in these instructions can lead to neural tube defects, emphasizing their vital importance in embryonic development.
Epigenetic regulatory mechanisms pivotal in guiding the processes of neurulation and neural tube formation
Neurulation and neural tube formation are intricate events during embryonic development. These processes are not solely governed by the genomic DNA sequence but also by epigenetic modifications that influence gene expression. Epigenetics, meaning "above genetics," involves chemical modifications to DNA and histones, non-coding RNAs, and chromatin remodeling, which collectively shape the way genes are expressed. Here's a look into some of the epigenetic regulatory mechanisms crucial for neurulation and neural tube formation:
DNA Methylation
DNA Methyltransferases (DNMTs): These enzymes add methyl groups to the cytosine residues in DNA, typically leading to gene silencing. DNMTs play vital roles in neural differentiation and neural tube formation. Anomalous methylation patterns can disrupt the expression of genes essential for these processes.
Histone Modifications
Histone Acetylation and Deacetylation: Acetylation, typically associated with gene activation, is governed by histone acetyltransferases (HATs). In contrast, deacetylation, linked with gene repression, is controlled by histone deacetylases (HDACs). These modifications are crucial in determining the transcriptional activity of genes involved in neurulation.
Histone Methylation: Depending on the specific lysine residue modified and the number of added methyl groups, histone methylation can either activate or repress gene expression. Enzymes like histone methyltransferases and demethylases regulate these modifications, ensuring proper gene expression during neural development.
Chromatin Remodeling
SWI/SNF Complex: This multi-protein complex changes the position of nucleosomes on DNA, allowing or hindering the binding of transcriptional machinery to DNA. This remodeling is essential for the timely activation and repression of genes during neural tube formation.
Non-Coding RNAs
MicroRNAs (miRNAs): These short RNA molecules do not code for proteins but play significant roles in post-transcriptional gene regulation. By targeting specific messenger RNAs (mRNAs), miRNAs can inhibit their translation or lead to their degradation, thus controlling the levels of proteins essential for neurulation.
Long Non-Coding RNAs (lncRNAs): These RNA molecules, longer than miRNAs, can interact with DNA, RNA, or proteins. They play roles in various cellular processes, including the regulation of gene expression at both transcriptional and post-transcriptional levels during neural development.
The orchestration of neurulation and neural tube formation is an intricate ballet of gene expression, with epigenetic regulatory mechanisms serving as the choreographers. Proper epigenetic modifications ensure that the right genes are expressed at the right time, facilitating the harmonious development of the neural tube and, subsequently, the central nervous system.
Distinct signaling pathways that are essential for the seamless orchestration of neurulation and neural tube formation
Neurulation and neural tube formation are complex processes that require precise coordination of cellular behavior. For this to occur, multiple signaling pathways operate in tandem, dictating cell fate, proliferation, migration, and morphogenesis. The following pathways have been recognized as pivotal in guiding the processes of neurulation and neural tube formation:
Sonic Hedgehog (Shh) Signaling
Dorsal-Ventral Patterning: Shh, secreted by the notochord and floor plate, is instrumental in the ventral patterning of the neural tube. It specifies the identity of ventral neural cell types by inducing various transcription factors.
Bone Morphogenetic Protein (BMP) Signaling
Neural Induction: BMPs, members of the TGF-β superfamily, play a critical role in ectodermal patterning. BMP antagonists, secreted by the organizer tissues, such as noggin, chordin, and follistatin, promote neural induction by inhibiting BMP activity.
Wnt Signaling
Neural Plate Border and Neural Crest Specification: Wnt signaling pathways, particularly canonical Wnt/β-catenin signaling, have pivotal roles in specifying the neural plate border and inducing the neural crest, a population of cells that gives rise to a plethora of derivatives, including peripheral neurons and glial cells.
Retinoic Acid (RA) Signaling
Anterior-Posterior Patterning: RA, a derivative of Vitamin A, produced in the posterior neural tissue, helps in establishing anterior-posterior identities within the neural tube. It operates in gradient fashion, with higher concentrations leading to more posterior neural fates.
Fibroblast Growth Factor (FGF) Signaling
Neural Induction and Patterning: FGFs have diverse roles during neurulation, including promoting neural induction and aiding in patterning the neural plate by working alongside other signaling pathways.
Planar Cell Polarity (PCP) Signaling
Convergent Extension Movements: PCP signaling is crucial for the cellular movements that shape the neural plate and tube. Convergent extension movements, driven by this pathway, elongate the neural plate along the anterior-posterior axis and narrow it mediolaterally.
The orchestration of neurulation and neural tube formation hinges on a symphony of signaling pathways that work in harmony. These pathways, sensitive to gradients and timing, collectively guide the cellular behaviors and fate decisions necessary for the construction of a well-formed neural tube, the precursor to the central nervous system.
Regulatory codes that underpin and oversee the mechanisms of neurulation and neural tube formation
Neurulation and the formation of the neural tube are foundational processes during vertebrate embryogenesis that give rise to the central nervous system. These processes are underpinned by a complex interplay of molecular, cellular, and mechanical codes that ensure their proper execution. The following regulatory codes are central to the oversight and execution of these processes:
Gene Regulatory Networks (GRNs)
Master Regulators: Transcription factors such as Sox2, Pax3, and Pax7 are pivotal in initiating and maintaining neural identity during the early stages of neural plate formation. These regulators initiate gene cascades crucial for successive phases of neurulation.
Coordinating Morphogenesis: Certain genes ensure the proper bending, folding, and closure of the neural plate. For instance, genes coding for cell-adhesion molecules like N-cadherin help in maintaining tissue integrity during these morphogenetic movements.
MicroRNAs (miRNAs)
Post-transcriptional Regulation: miRNAs, small non-coding RNAs, modulate gene expression post-transcriptionally. They're involved in fine-tuning the dynamics of protein production necessary for neural tube formation. For example, miR-34 and miR-449 have been implicated in regulating neural crest cell migration and differentiation.
Epigenetic Modifications
Histone Modifications and DNA Methylation: Chemical modifications to DNA and histones, like methylation and acetylation, modulate the accessibility of genes to the transcriptional machinery, thus influencing gene expression patterns during neurulation.
Feedback Loops
Ensuring Robustness: Many of the signaling pathways, such as Shh and BMP, involved in neural tube formation have built-in feedback loops. These loops help ensure that the processes are robust against perturbations and are carried out with fidelity.
Mechanical Forces
Cell Shape and Tissue Morphogenesis: Cellular behaviors, such as apical constriction and cell intercalation, are driven by mechanical forces. These behaviors, in turn, drive the neural plate's bending and folding. Regulatory codes, often in the form of mechanotransduction pathways, ensure that these forces are generated and applied correctly.
The precise orchestration of neurulation and neural tube formation relies on a comprehensive set of regulatory codes, ranging from gene expression and post-transcriptional modifications to mechanical forces. Together, these codes ensure that the embryo develops a well-formed neural tube, setting the stage for the later development of the brain and spinal cord.
Does current scientific literature provide evidence to suggest that neurulation and neural tube formation were evolutionary processes?
Neurulation and neural tube formation are foundational processes during vertebrate embryogenesis that give rise to the central nervous system. These processes involve a myriad of intricate and interdependent molecular, cellular, and mechanical mechanisms, suggesting the complexity of the design and the challenges of evolutionary explanations.
Complexity and Interdependence
Integrated Gene Regulatory Networks (GRNs): Neurulation is driven by a complex set of GRNs that not only need to be present but also intricately tuned to ensure proper timing and patterning of neural development. The coordinated action of master regulators, like Sox2, Pax3, and Pax7, is pivotal. Any disruption or incomplete integration of these GRNs would likely result in non-functional or adverse outcomes.
Signaling Pathways: Key pathways such as Sonic Hedgehog (Shh) and Bone Morphogenic Protein (BMP) have tightly integrated feedback loops ensuring that neural plate cells receive the right signals at the right time. Without the full signaling pathway present and functional, the entire process could be derailed.
Epigenetic Controls: DNA methylation, histone modifications, and other epigenetic controls are necessary for precise temporal and spatial gene expression during neurulation. These controls are not just add-ons but essential layers of regulation.
Challenges for Stepwise Evolution
Coordinated Cellular Behaviors: The physical act of neurulation, where the neural plate bends, folds, and eventually fuses to form the neural tube, requires a multitude of cells to act in concert. These behaviors, driven by mechanical forces and cellular signaling, seem to necessitate a pre-existing set of instructions rather than a gradual, stepwise accumulation.
Symbiotic Protein Interactions: Many proteins involved in neurulation interact in ways that seem symbiotic. For instance, cell adhesion molecules ensure tissue integrity during the folding of the neural plate. The presence of one protein without its partner or counterpart might not only be non-functional but could be detrimental.
The Problem of Intermediates
Functionality of Partial Systems: For evolution to favor a particular trait or mechanism, it generally needs to confer some advantage. However, with neurulation, it's challenging to envision how partial or intermediate stages could offer any functional advantage. Incomplete neural tube formation results in severe abnormalities.
Requirement for Simultaneous Systems: The codes, languages, signaling, and proteins involved in neurulation seem to be so interdependent that they must all be in place for the process to work. The idea of them evolving simultaneously, yet independently, stretches the imagination.
While the scientific community continues to explore the mechanisms and origins of complex processes like neurulation, the sheer intricacy, and interdependence of the involved systems raise profound questions about the feasibility of stepwise evolutionary explanations. The presence of such a well-coordinated and integrated system suggests a design of profound intelligence.
Could the mechanisms and components involved in neurulation and neural tube formation be characterized as irreducibly complex or interdependent?
Neurulation and neural tube formation represent quintessential processes that give rise to the central nervous system in vertebrate embryogenesis. The assembly and function of the structures and pathways within this framework seem to present a deeply interdependent and potentially irreducibly complex system.
Irreducible Complexity and Interdependence
Gene Regulatory Networks (GRNs): Neurulation is underpinned by an intricate set of GRNs, where master regulatory genes like Sox2, Pax3, and Pax7 are pivotal. A failure in one aspect of this network could compromise the entire process. These genes and their networks function collectively, with one component being non-functional in the absence of the others.
Signaling Pathways: Key pathways, including Sonic Hedgehog (Shh) and Bone Morphogenic Protein (BMP), are not just sequences of events, but possess tightly integrated feedback mechanisms. If one part of these pathways was missing or non-functional, it could jeopardize the entire process of neural differentiation.
Cellular Mechanisms and Dynamics: The cellular behaviors during neurulation, from cell migration to changes in cell shape and polarity, hinge on a balance of forces and cellular communications. The mechanisms driving these behaviors seem interdependent, as a malfunction in one would impair the entire physical process of neurulation.
Epigenetic Regulation: DNA methylation, histone modifications, and non-coding RNAs contribute to precise gene expression during neurulation. These components form an interconnected regulatory system, where the absence or malfunction of one aspect could lead to catastrophic developmental errors.
The Cross-Talk and Communication Systems
Intercellular Communication: Cells during neurulation do not operate in isolation. They communicate using signaling molecules, such as growth factors, to ensure synchronized behavior. This communication is vital for the seamless orchestration of cell movements and differentiation.
Intracellular Communication: Within each cell, multiple pathways and molecular processes, from protein synthesis to cellular metabolism, are interconnected. Proteins, metabolites, and ions continually communicate, ensuring the cell's function and survival.
The Evolutionary Implications
Challenge of Stepwise Evolution: Given the myriad of codes, languages, signaling pathways, and proteins involved in neurulation, the evolutionary progression of such an intricate system in a stepwise manner becomes daunting. Intermediate stages might not provide any functional advantage, making natural selection of such stages implausible.
Requirement for Simultaneous Systems: The sheer interdependence means that for one system to function properly, others must already be in place. It challenges the notion of gradual addition, as adding one component without the others could result in a non-functional or even detrimental system.
The profound complexity and interdependence observed in neurulation and neural tube formation are awe-inspiring. Such intricately connected systems, where the absence of one component could lead to the collapse of the entire process, suggest a sophisticated design that goes beyond the capabilities of random, stepwise evolutionary processes.
Once neurulation and neural tube formation are fully operational, what other intra and extracellular systems might they be intricately interconnected with or dependent upon?
Once neurulation and neural tube formation processes are fully realized, they don't act in isolation. The neural tube and its constituent cells become an active hub, intricately connected to various other cellular systems and external influences. These connections and dependencies ensure the proper functioning, differentiation, and survival of the neural tissue.
Intracellular Systems
Cellular Metabolism: Neurons, and the glial cells supporting them, have high metabolic demands. The mitochondria, often referred to as the cellular powerhouses, must supply this demand by producing ATP, and their health and function are vital for neural cell survival.
Protein Synthesis and Degradation: Neural cells constantly produce proteins necessary for synaptic function, neurotransmitter synthesis, and cell maintenance. Ribosomes synthesize these proteins, while proteasomes and lysosomes degrade misfolded or old proteins.
Calcium Signaling: Intracellular calcium levels in neurons are critical for processes like neurotransmitter release, gene expression, and synaptic plasticity. The endoplasmic reticulum, mitochondria, and various ion channels coordinate to manage these levels.
Extracellular Systems and Influences
Neurotrophic Factors: These are molecules that support neuronal survival, differentiation, and growth. Molecules such as nerve growth factor (NGF) or brain-derived neurotrophic factor (BDNF) are essential for the health and function of neurons.
Glial Support: Astrocytes, oligodendrocytes, and microglia provide nutritional, structural, and immune support to neurons. They are not merely passive support cells but play active roles in synaptic function, myelination, and neural defense.
Synaptic Communication: Neurons communicate with each other via synapses, where neurotransmitters like glutamate, GABA, or dopamine are released. This neurotransmitter system is paramount for neural communication and information processing.
Vascular Supply: Blood vessels provide essential nutrients and oxygen to the neural tissue. Moreover, the blood-brain barrier, formed by the interaction of endothelial cells, astrocytes, and pericytes, protects the brain from harmful substances while ensuring the supply of necessary nutrients.
Extracellular Matrix (ECM): The ECM provides structural support and plays a role in guiding cell migration during development. It also influences cell behavior, synaptic stability, and plasticity in the mature nervous system.
The completion of neurulation and neural tube formation is just the beginning of a series of intricate relationships and dependencies that neural cells will establish with both internal cellular systems and external influences. This highly integrated network ensures the optimal functionality and adaptability of the central nervous system throughout an organism's life.
1. If complex systems exhibit properties of interdependence, semiotic coding, and synchronization, implying that their elements had to emerge simultaneously and harmoniously to function properly, then such systems show traits commonly attributed to designed mechanisms.
2. The neurulation and neural tube formation processes, along with their associated intracellular and extracellular systems, exhibit these very properties of interdependence, semiotic coding, and synchronization.
3. Therefore, the neurulation and neural tube formation processes, along with their connected systems, indicate traits commonly attributed to designed mechanisms.
1. Wikipedia: Neurulation
Neurulation and neural tube formation are critical processes in vertebrate embryonic development that lay the foundation for the creation of the central nervous system (CNS). These processes intricately shape and transform the embryonic tissue, setting the stage for the formation of the brain and spinal cord.
Neurulation
Neurulation is the initial step in the formation of the CNS. It begins with the transformation of the neural plate, a flat sheet of ectodermal tissue, into the neural tube. This transformative process involves several key stages:
Elevation of Neural Folds: As the embryo develops, the neural plate undergoes a process of elevation, forming neural folds on both sides. These folds gradually approach each other along the midline.
Fusion of Neural Folds: The neural folds eventually fuse at the midline, creating a neural tube. This tube becomes the precursor to the brain and spinal cord.
Formation of Neural Crest Cells: Alongside the neural tube formation, a population of cells known as neural crest cells emerge at the borders of the neural plate. These cells play a crucial role in forming various structures, including peripheral nerves, ganglia, and some skeletal elements.
Neural Tube Formation
The neural tube, formed through neurulation, is the rudimentary structure that gives rise to the brain and spinal cord. It undergoes further specialization to create distinct regions of the CNS:
Primary Vesicle Formation: The neural tube initially differentiates into three primary vesicles: the prosencephalon (forebrain), mesencephalon (midbrain), and rhombencephalon (hindbrain).
Secondary Vesicle Formation: These primary vesicles subsequently undergo further differentiation into five secondary vesicles: telencephalon and diencephalon from the prosencephalon, mesencephalon remains unchanged, and metencephalon and myelencephalon from the rhombencephalon.
Cavities and Structure Formation: These vesicles expand and develop specific cavities that become the ventricles of the brain and central canal of the spinal cord. The walls of these vesicles differentiate into the various regions of the CNS.
Neurulation and neural tube formation are critical because they set the foundation for the complex structures and functions of the CNS. These processes ensure the proper development of the brain and spinal cord, which are essential for sensory perception, motor control, cognition, and a myriad of other neurological functions.
How does the neural tube differentiate into distinct regions, such as the brain and spinal cord?
The neural tube, formed through the process of neurulation, gives rise to both the brain and the spinal cord in vertebrate embryos. This remarkable differentiation involves complex molecular signaling and patterning mechanisms that lead to the formation of distinct regions with specific functions.
Formation of Primary Vesicles
After the initial fusion of the neural folds, the neural tube differentiates into three primary vesicles along the anterior-posterior axis: the prosencephalon (forebrain), mesencephalon (midbrain), and rhombencephalon (hindbrain). Each primary vesicle serves as the basis for further differentiation.
Secondary Vesicle Formation and Patterning
These primary vesicles then undergo further differentiation into five secondary vesicles through a process called regionalization:
Telencephalon and Diencephalon (Forebrain): The prosencephalon gives rise to the telencephalon (which develops into the cerebral hemispheres) and the diencephalon (which forms structures like the thalamus and hypothalamus).
Mesencephalon (Midbrain): The mesencephalon remains relatively unchanged and develops into the midbrain structures, including the tectum and tegmentum.
Metencephalon and Myelencephalon (Hindbrain): The rhombencephalon differentiates into the metencephalon (developing into the pons and cerebellum) and the myelencephalon (forming the medulla oblongata).
Patterning Signals and Genetic Regulation
The differentiation of the neural tube into these distinct regions is governed by intricate molecular signaling pathways, including the actions of morphogens such as Sonic Hedgehog (Shh), Fibroblast Growth Factors (FGFs), and Bone Morphogenetic Proteins (BMPs). These signaling molecules establish concentration gradients along the neural tube, instructing cells to adopt specific identities based on their location.
Hox Genes
Hox genes, which play a pivotal role in determining regional identities along the anterior-posterior axis of the body, are also crucial for neural tube differentiation. The expression patterns of Hox genes guide the formation of different segments within the neural tube.
Cellular Migration and Differentiation
As cells within the neural tube receive specific signaling cues, they migrate to their designated regions and differentiate into the diverse cell types that make up the brain and spinal cord.
Patterning and Function
This complex differentiation process ultimately gives rise to the various brain structures and spinal cord segments, each with specialized functions that contribute to sensory perception, motor control, cognition, and other essential neurological processes.
Transverse sections that show the progression of the neural plate to the neural groove from bottom to top 1
At what juncture in the evolutionary timeline are neurulation and neural tube formation postulated to have made their first appearance?
Neurulation and neural tube formation are fundamental embryological processes that lead to the development of the central nervous system (CNS), including the brain and spinal cord. These events are critical for the formation of complex nervous systems and have been conserved across a broad range of vertebrates. Here's a look into their possible evolutionary origins:
Origins of the Nervous System
Simple Nervous Systems: The earliest multicellular organisms would have had rudimentary nervous systems, consisting of simple nerve nets or basic nerve cords. These basic nervous structures wouldn't have required specialized processes like neurulation.
Bilateria and CNS Development: The appearance of bilaterally symmetrical animals, or Bilateria, is a key event in the evolution of the CNS. It is hypothesized that the ancestors of modern bilaterians possessed a centralized nerve cord, which served as a precursor to more advanced nervous systems.
Neurulation and Neural Tube Formation: Neurulation and the formation of a neural tube would have emerged with the need for a more centralized and organized nervous system. This process would have been critical for the development of a dorsal nerve cord in early chordates, which is an ancestral feature of all vertebrates.
Vertebrate Evolution and Neural Tube Specialization
Primitive Chordates: In early chordates like amphioxus, a simple notochord and nerve cord were present. These organisms would have exhibited basic neurulation processes, leading to the formation of a dorsal nerve cord.
Early Vertebrates: With the emergence of early vertebrates, the neural tube would have become more specialized, giving rise to distinct regions such as the forebrain, midbrain, and hindbrain. This differentiation is crucial for the diverse functions and capabilities seen in modern vertebrates.
Neural Crest Cells: Along with the neural tube, the evolution of neural crest cells would have played a pivotal role in vertebrate diversification. These cells originate from the borders of the neural tube and migrate to various parts of the embryo, contributing to structures like cranial bones, peripheral nerves, and more.
The processes of neurulation and neural tube formation are thought to have made their appearance during the evolution of early chordates, setting the stage for the complex nervous systems seen in today's vertebrates. These developmental events would have provided the architectural foundation for advanced neural structures, facilitating sophisticated behaviors and adaptations in vertebrate lineages.
De novo genetic information would to instantiate the processes of neurulation and neural tube formation
Neurulation and neural tube formation are critical stages in the development of the vertebrate central nervous system. They rely on intricate molecular and cellular processes that are guided by various genes and their corresponding proteins. While numerous genes are involved in this complex developmental process, certain genes are recognized as core players in driving neurulation and establishing the neural tube. Here's an overview of some of these crucial genetic components:
Key Genetic Components
Notochord Induction Genes: The notochord, a midline embryonic structure, secretes signaling molecules that instruct the overlying ectoderm to become neural tissue. Genes like Noggin, Chordin, and Follistatin are crucial for this induction, as they inhibit proteins that would otherwise prevent neural differentiation.
Neural Plate Border Specifiers: Genes such as Pax3, Pax7, Msx1, and Zic1 play roles in specifying cells at the border of the neural plate. These border cells can give rise to both neural crest cells and neural tissue.
Neural Fold Elevation and Convergence: As the neural plate forms, it starts to fold, with its edges (neural folds) elevating and moving towards each other. Genes like Shh (Sonic hedgehog) and BMP4 (Bone Morphogenetic Protein 4) play roles in guiding this morphogenesis.
Neural Tube Closure: The eventual fusion of the neural folds to form a closed neural tube is a critical step. Genes such as Celsr1, Vangl2, and Fzd3 are vital components of the planar cell polarity pathway and are instrumental in coordinating the movements of cells during tube closure.
Neural Differentiation and Patterning: Once the neural tube is formed, it undergoes further differentiation and patterning. Genes like Shh and Wnt are involved in ventral and dorsal patterning of the neural tube, respectively, establishing regions that will later give rise to different structures in the CNS.
The process of neurulation and neural tube formation is orchestrated by a myriad of genes working in concert. These genes provide the de novo genetic information necessary for the successful development of the central nervous system. Any disruptions in the function of these genes can lead to neural tube defects, highlighting their critical importance in embryonic development.
Manufacturing codes and languages that would have to emerge and be operational for neurulation and the formation of the neural tube
Neurulation and the formation of the neural tube are intricate processes in embryonic development, driven by a series of tightly regulated molecular and cellular instructions. To understand these "manufacturing codes and languages," one must delve into the complex world of genetic regulation, signaling pathways, and cell-to-cell communications that drive these developmental processes. Here's a glimpse into some of these genetic "codes" and "languages":
Genetic Codes and Regulation
Gene Expression and Transcription Factors: Specific genes are turned on or off during different stages of neurulation. Transcription factors like Sox1, Sox2, and Sox3 are expressed in the early neural plate and are crucial for neural differentiation.
Epigenetic Regulation: Modifications to DNA and its associated proteins can alter gene expression without changing the underlying DNA sequence. Epigenetic changes, such as DNA methylation or histone modifications, are pivotal in determining cell fate during neural tube formation.
Signaling Pathways
Bone Morphogenetic Proteins (BMPs) and Their Antagonists: BMP signaling tends to promote epidermal fates, while its inhibition by molecules like Noggin, Chordin, and Follistatin promotes neural fates.
Sonic Hedgehog (Shh) Signaling: The notochord produces Shh, which plays a crucial role in ventral patterning of the neural tube, determining different neuronal subtypes based on concentration gradients.
Wnt Signaling: Important for dorsal patterning of the neural tube and interacts with other signaling pathways to ensure the right balance of cell types.
Cellular Communication and Interaction
Planar Cell Polarity (PCP) Pathway: This pathway controls the convergent extension movements during neurulation, where cells intercalate and the neural plate narrows and lengthens. Key components include Vangl2, Celsr1, and Fzd3.
Cell Adhesion Molecules: Molecules such as cadherins and integrins play roles in ensuring that cells stick together and move collectively during the bending and folding processes of neurulation.
Neurulation and neural tube formation are orchestrated by a myriad of "manufacturing codes and languages" at the genetic, molecular, and cellular levels. These intricate processes ensure the proper development and functionality of the central nervous system. Any disruptions in these instructions can lead to neural tube defects, emphasizing their vital importance in embryonic development.
Epigenetic regulatory mechanisms pivotal in guiding the processes of neurulation and neural tube formation
Neurulation and neural tube formation are intricate events during embryonic development. These processes are not solely governed by the genomic DNA sequence but also by epigenetic modifications that influence gene expression. Epigenetics, meaning "above genetics," involves chemical modifications to DNA and histones, non-coding RNAs, and chromatin remodeling, which collectively shape the way genes are expressed. Here's a look into some of the epigenetic regulatory mechanisms crucial for neurulation and neural tube formation:
DNA Methylation
DNA Methyltransferases (DNMTs): These enzymes add methyl groups to the cytosine residues in DNA, typically leading to gene silencing. DNMTs play vital roles in neural differentiation and neural tube formation. Anomalous methylation patterns can disrupt the expression of genes essential for these processes.
Histone Modifications
Histone Acetylation and Deacetylation: Acetylation, typically associated with gene activation, is governed by histone acetyltransferases (HATs). In contrast, deacetylation, linked with gene repression, is controlled by histone deacetylases (HDACs). These modifications are crucial in determining the transcriptional activity of genes involved in neurulation.
Histone Methylation: Depending on the specific lysine residue modified and the number of added methyl groups, histone methylation can either activate or repress gene expression. Enzymes like histone methyltransferases and demethylases regulate these modifications, ensuring proper gene expression during neural development.
Chromatin Remodeling
SWI/SNF Complex: This multi-protein complex changes the position of nucleosomes on DNA, allowing or hindering the binding of transcriptional machinery to DNA. This remodeling is essential for the timely activation and repression of genes during neural tube formation.
Non-Coding RNAs
MicroRNAs (miRNAs): These short RNA molecules do not code for proteins but play significant roles in post-transcriptional gene regulation. By targeting specific messenger RNAs (mRNAs), miRNAs can inhibit their translation or lead to their degradation, thus controlling the levels of proteins essential for neurulation.
Long Non-Coding RNAs (lncRNAs): These RNA molecules, longer than miRNAs, can interact with DNA, RNA, or proteins. They play roles in various cellular processes, including the regulation of gene expression at both transcriptional and post-transcriptional levels during neural development.
The orchestration of neurulation and neural tube formation is an intricate ballet of gene expression, with epigenetic regulatory mechanisms serving as the choreographers. Proper epigenetic modifications ensure that the right genes are expressed at the right time, facilitating the harmonious development of the neural tube and, subsequently, the central nervous system.
Distinct signaling pathways that are essential for the seamless orchestration of neurulation and neural tube formation
Neurulation and neural tube formation are complex processes that require precise coordination of cellular behavior. For this to occur, multiple signaling pathways operate in tandem, dictating cell fate, proliferation, migration, and morphogenesis. The following pathways have been recognized as pivotal in guiding the processes of neurulation and neural tube formation:
Sonic Hedgehog (Shh) Signaling
Dorsal-Ventral Patterning: Shh, secreted by the notochord and floor plate, is instrumental in the ventral patterning of the neural tube. It specifies the identity of ventral neural cell types by inducing various transcription factors.
Bone Morphogenetic Protein (BMP) Signaling
Neural Induction: BMPs, members of the TGF-β superfamily, play a critical role in ectodermal patterning. BMP antagonists, secreted by the organizer tissues, such as noggin, chordin, and follistatin, promote neural induction by inhibiting BMP activity.
Wnt Signaling
Neural Plate Border and Neural Crest Specification: Wnt signaling pathways, particularly canonical Wnt/β-catenin signaling, have pivotal roles in specifying the neural plate border and inducing the neural crest, a population of cells that gives rise to a plethora of derivatives, including peripheral neurons and glial cells.
Retinoic Acid (RA) Signaling
Anterior-Posterior Patterning: RA, a derivative of Vitamin A, produced in the posterior neural tissue, helps in establishing anterior-posterior identities within the neural tube. It operates in gradient fashion, with higher concentrations leading to more posterior neural fates.
Fibroblast Growth Factor (FGF) Signaling
Neural Induction and Patterning: FGFs have diverse roles during neurulation, including promoting neural induction and aiding in patterning the neural plate by working alongside other signaling pathways.
Planar Cell Polarity (PCP) Signaling
Convergent Extension Movements: PCP signaling is crucial for the cellular movements that shape the neural plate and tube. Convergent extension movements, driven by this pathway, elongate the neural plate along the anterior-posterior axis and narrow it mediolaterally.
The orchestration of neurulation and neural tube formation hinges on a symphony of signaling pathways that work in harmony. These pathways, sensitive to gradients and timing, collectively guide the cellular behaviors and fate decisions necessary for the construction of a well-formed neural tube, the precursor to the central nervous system.
Regulatory codes that underpin and oversee the mechanisms of neurulation and neural tube formation
Neurulation and the formation of the neural tube are foundational processes during vertebrate embryogenesis that give rise to the central nervous system. These processes are underpinned by a complex interplay of molecular, cellular, and mechanical codes that ensure their proper execution. The following regulatory codes are central to the oversight and execution of these processes:
Gene Regulatory Networks (GRNs)
Master Regulators: Transcription factors such as Sox2, Pax3, and Pax7 are pivotal in initiating and maintaining neural identity during the early stages of neural plate formation. These regulators initiate gene cascades crucial for successive phases of neurulation.
Coordinating Morphogenesis: Certain genes ensure the proper bending, folding, and closure of the neural plate. For instance, genes coding for cell-adhesion molecules like N-cadherin help in maintaining tissue integrity during these morphogenetic movements.
MicroRNAs (miRNAs)
Post-transcriptional Regulation: miRNAs, small non-coding RNAs, modulate gene expression post-transcriptionally. They're involved in fine-tuning the dynamics of protein production necessary for neural tube formation. For example, miR-34 and miR-449 have been implicated in regulating neural crest cell migration and differentiation.
Epigenetic Modifications
Histone Modifications and DNA Methylation: Chemical modifications to DNA and histones, like methylation and acetylation, modulate the accessibility of genes to the transcriptional machinery, thus influencing gene expression patterns during neurulation.
Feedback Loops
Ensuring Robustness: Many of the signaling pathways, such as Shh and BMP, involved in neural tube formation have built-in feedback loops. These loops help ensure that the processes are robust against perturbations and are carried out with fidelity.
Mechanical Forces
Cell Shape and Tissue Morphogenesis: Cellular behaviors, such as apical constriction and cell intercalation, are driven by mechanical forces. These behaviors, in turn, drive the neural plate's bending and folding. Regulatory codes, often in the form of mechanotransduction pathways, ensure that these forces are generated and applied correctly.
The precise orchestration of neurulation and neural tube formation relies on a comprehensive set of regulatory codes, ranging from gene expression and post-transcriptional modifications to mechanical forces. Together, these codes ensure that the embryo develops a well-formed neural tube, setting the stage for the later development of the brain and spinal cord.
Does current scientific literature provide evidence to suggest that neurulation and neural tube formation were evolutionary processes?
Neurulation and neural tube formation are foundational processes during vertebrate embryogenesis that give rise to the central nervous system. These processes involve a myriad of intricate and interdependent molecular, cellular, and mechanical mechanisms, suggesting the complexity of the design and the challenges of evolutionary explanations.
Complexity and Interdependence
Integrated Gene Regulatory Networks (GRNs): Neurulation is driven by a complex set of GRNs that not only need to be present but also intricately tuned to ensure proper timing and patterning of neural development. The coordinated action of master regulators, like Sox2, Pax3, and Pax7, is pivotal. Any disruption or incomplete integration of these GRNs would likely result in non-functional or adverse outcomes.
Signaling Pathways: Key pathways such as Sonic Hedgehog (Shh) and Bone Morphogenic Protein (BMP) have tightly integrated feedback loops ensuring that neural plate cells receive the right signals at the right time. Without the full signaling pathway present and functional, the entire process could be derailed.
Epigenetic Controls: DNA methylation, histone modifications, and other epigenetic controls are necessary for precise temporal and spatial gene expression during neurulation. These controls are not just add-ons but essential layers of regulation.
Challenges for Stepwise Evolution
Coordinated Cellular Behaviors: The physical act of neurulation, where the neural plate bends, folds, and eventually fuses to form the neural tube, requires a multitude of cells to act in concert. These behaviors, driven by mechanical forces and cellular signaling, seem to necessitate a pre-existing set of instructions rather than a gradual, stepwise accumulation.
Symbiotic Protein Interactions: Many proteins involved in neurulation interact in ways that seem symbiotic. For instance, cell adhesion molecules ensure tissue integrity during the folding of the neural plate. The presence of one protein without its partner or counterpart might not only be non-functional but could be detrimental.
The Problem of Intermediates
Functionality of Partial Systems: For evolution to favor a particular trait or mechanism, it generally needs to confer some advantage. However, with neurulation, it's challenging to envision how partial or intermediate stages could offer any functional advantage. Incomplete neural tube formation results in severe abnormalities.
Requirement for Simultaneous Systems: The codes, languages, signaling, and proteins involved in neurulation seem to be so interdependent that they must all be in place for the process to work. The idea of them evolving simultaneously, yet independently, stretches the imagination.
While the scientific community continues to explore the mechanisms and origins of complex processes like neurulation, the sheer intricacy, and interdependence of the involved systems raise profound questions about the feasibility of stepwise evolutionary explanations. The presence of such a well-coordinated and integrated system suggests a design of profound intelligence.
Could the mechanisms and components involved in neurulation and neural tube formation be characterized as irreducibly complex or interdependent?
Neurulation and neural tube formation represent quintessential processes that give rise to the central nervous system in vertebrate embryogenesis. The assembly and function of the structures and pathways within this framework seem to present a deeply interdependent and potentially irreducibly complex system.
Irreducible Complexity and Interdependence
Gene Regulatory Networks (GRNs): Neurulation is underpinned by an intricate set of GRNs, where master regulatory genes like Sox2, Pax3, and Pax7 are pivotal. A failure in one aspect of this network could compromise the entire process. These genes and their networks function collectively, with one component being non-functional in the absence of the others.
Signaling Pathways: Key pathways, including Sonic Hedgehog (Shh) and Bone Morphogenic Protein (BMP), are not just sequences of events, but possess tightly integrated feedback mechanisms. If one part of these pathways was missing or non-functional, it could jeopardize the entire process of neural differentiation.
Cellular Mechanisms and Dynamics: The cellular behaviors during neurulation, from cell migration to changes in cell shape and polarity, hinge on a balance of forces and cellular communications. The mechanisms driving these behaviors seem interdependent, as a malfunction in one would impair the entire physical process of neurulation.
Epigenetic Regulation: DNA methylation, histone modifications, and non-coding RNAs contribute to precise gene expression during neurulation. These components form an interconnected regulatory system, where the absence or malfunction of one aspect could lead to catastrophic developmental errors.
The Cross-Talk and Communication Systems
Intercellular Communication: Cells during neurulation do not operate in isolation. They communicate using signaling molecules, such as growth factors, to ensure synchronized behavior. This communication is vital for the seamless orchestration of cell movements and differentiation.
Intracellular Communication: Within each cell, multiple pathways and molecular processes, from protein synthesis to cellular metabolism, are interconnected. Proteins, metabolites, and ions continually communicate, ensuring the cell's function and survival.
The Evolutionary Implications
Challenge of Stepwise Evolution: Given the myriad of codes, languages, signaling pathways, and proteins involved in neurulation, the evolutionary progression of such an intricate system in a stepwise manner becomes daunting. Intermediate stages might not provide any functional advantage, making natural selection of such stages implausible.
Requirement for Simultaneous Systems: The sheer interdependence means that for one system to function properly, others must already be in place. It challenges the notion of gradual addition, as adding one component without the others could result in a non-functional or even detrimental system.
The profound complexity and interdependence observed in neurulation and neural tube formation are awe-inspiring. Such intricately connected systems, where the absence of one component could lead to the collapse of the entire process, suggest a sophisticated design that goes beyond the capabilities of random, stepwise evolutionary processes.
Once neurulation and neural tube formation are fully operational, what other intra and extracellular systems might they be intricately interconnected with or dependent upon?
Once neurulation and neural tube formation processes are fully realized, they don't act in isolation. The neural tube and its constituent cells become an active hub, intricately connected to various other cellular systems and external influences. These connections and dependencies ensure the proper functioning, differentiation, and survival of the neural tissue.
Intracellular Systems
Cellular Metabolism: Neurons, and the glial cells supporting them, have high metabolic demands. The mitochondria, often referred to as the cellular powerhouses, must supply this demand by producing ATP, and their health and function are vital for neural cell survival.
Protein Synthesis and Degradation: Neural cells constantly produce proteins necessary for synaptic function, neurotransmitter synthesis, and cell maintenance. Ribosomes synthesize these proteins, while proteasomes and lysosomes degrade misfolded or old proteins.
Calcium Signaling: Intracellular calcium levels in neurons are critical for processes like neurotransmitter release, gene expression, and synaptic plasticity. The endoplasmic reticulum, mitochondria, and various ion channels coordinate to manage these levels.
Extracellular Systems and Influences
Neurotrophic Factors: These are molecules that support neuronal survival, differentiation, and growth. Molecules such as nerve growth factor (NGF) or brain-derived neurotrophic factor (BDNF) are essential for the health and function of neurons.
Glial Support: Astrocytes, oligodendrocytes, and microglia provide nutritional, structural, and immune support to neurons. They are not merely passive support cells but play active roles in synaptic function, myelination, and neural defense.
Synaptic Communication: Neurons communicate with each other via synapses, where neurotransmitters like glutamate, GABA, or dopamine are released. This neurotransmitter system is paramount for neural communication and information processing.
Vascular Supply: Blood vessels provide essential nutrients and oxygen to the neural tissue. Moreover, the blood-brain barrier, formed by the interaction of endothelial cells, astrocytes, and pericytes, protects the brain from harmful substances while ensuring the supply of necessary nutrients.
Extracellular Matrix (ECM): The ECM provides structural support and plays a role in guiding cell migration during development. It also influences cell behavior, synaptic stability, and plasticity in the mature nervous system.
The completion of neurulation and neural tube formation is just the beginning of a series of intricate relationships and dependencies that neural cells will establish with both internal cellular systems and external influences. This highly integrated network ensures the optimal functionality and adaptability of the central nervous system throughout an organism's life.
1. If complex systems exhibit properties of interdependence, semiotic coding, and synchronization, implying that their elements had to emerge simultaneously and harmoniously to function properly, then such systems show traits commonly attributed to designed mechanisms.
2. The neurulation and neural tube formation processes, along with their associated intracellular and extracellular systems, exhibit these very properties of interdependence, semiotic coding, and synchronization.
3. Therefore, the neurulation and neural tube formation processes, along with their connected systems, indicate traits commonly attributed to designed mechanisms.
1. Wikipedia: Neurulation
Last edited by Otangelo on Wed Sep 13, 2023 2:06 pm; edited 1 time in total
