6.1 Neural induction and neurogenesis
5 min read•august 14, 2024
and neurogenesis are key processes in brain development. They kick off the formation of the nervous system, turning basic cells into specialized neural tissue. This transformation sets the stage for the complex structures and functions of our brains.
These processes involve intricate molecular signals and cell interactions. Understanding them helps us grasp how the brain forms and grows, shedding light on neurodevelopmental disorders and potential treatments for brain injuries or diseases.
Neural induction and signaling molecules
Process of neural induction
Top images from around the web for Process of neural induction
Neural tube - Wikipedia View original
Is this image relevant?
Embryonic Development | Anatomy and Physiology II View original
Is this image relevant?
Anatomy of the Nervous System | Anatomy and Physiology I View original
Is this image relevant?
Neural tube - Wikipedia View original
Is this image relevant?
Embryonic Development | Anatomy and Physiology II View original
Is this image relevant?
1 of 3
Top images from around the web for Process of neural induction
Neural tube - Wikipedia View original
Is this image relevant?
Embryonic Development | Anatomy and Physiology II View original
Is this image relevant?
Anatomy of the Nervous System | Anatomy and Physiology I View original
Is this image relevant?
Neural tube - Wikipedia View original
Is this image relevant?
Embryonic Development | Anatomy and Physiology II View original
Is this image relevant?
1 of 3
- Neural induction is the process by which the ectoderm is induced to form the , which gives rise to the nervous system
- The is induced to form the neural plate by signals from the dorsal mesoderm, known as the in amphibians and the node in mammals
- The neural plate subsequently folds to form the neural tube, which gives rise to the central nervous system (brain and spinal cord)
Role of signaling molecules in neural induction
- The Spemann organizer and the node secrete signaling molecules, such as noggin, chordin, and follistatin, which inhibit BMP (bone morphogenetic protein) signaling in the dorsal ectoderm
- Inhibition of in the dorsal ectoderm leads to the activation of neural-specific genes and the formation of the neural plate
- Other signaling pathways involved in neural induction include Wnt, FGF (fibroblast growth factor), and , which work in concert with BMP inhibition to promote neural fate specification
Differentiation of neural progenitor cells
Neural progenitor cell characteristics and division
- , also known as , are multipotent cells that can differentiate into various cell types of the nervous system
- During neurogenesis, neural progenitor cells undergo symmetric and asymmetric cell divisions to generate more progenitor cells and differentiated neural cells, respectively
- Symmetric cell divisions expand the neural progenitor cell pool, while asymmetric cell divisions produce one progenitor cell and one differentiated cell (neuron or glial cell)
Differentiation into neurons, astrocytes, and oligodendrocytes
- Neural progenitor cells can differentiate into , , and , the three main cell types of the central nervous system
- Neurons are the primary functional units of the nervous system, responsible for transmitting and processing information through electrical and chemical signals
- Astrocytes provide structural and metabolic support to neurons, regulate synaptic transmission, and participate in the formation of the blood-brain barrier
- Oligodendrocytes produce myelin, which insulates axons and facilitates rapid signal transmission in the central nervous system
Regulation of neural progenitor cell differentiation
- The differentiation of neural progenitor cells is regulated by intrinsic factors, such as transcription factors, and extrinsic factors, such as signaling molecules in the local environment
- plays a crucial role in maintaining the balance between neural progenitor cell proliferation and differentiation by promoting progenitor cell maintenance and inhibiting neuronal differentiation
- (bHLH) transcription factors, such as and , promote neuronal differentiation by activating neuron-specific gene expression programs
- Other transcription factors, such as and , promote glial differentiation by regulating the expression of genes involved in astrocyte and oligodendrocyte development
Regulation of neurogenesis in development
Spatial regulation of neurogenesis in the developing brain
- In the developing brain, neurogenesis occurs in specific regions called the and , which are located adjacent to the ventricles
- The ventricular zone and subventricular zone contain neural progenitor cells that undergo proliferation and differentiation to generate neurons and glial cells
- Neurogenesis in the developing brain follows a general , with earlier-born neurons occupying deeper layers (layers V-VI in the cerebral cortex) and later-born neurons occupying more superficial layers (layers II-IV)
Spatial regulation of neurogenesis in the developing spinal cord
- In the developing spinal cord, neurogenesis occurs in a ventral-to-dorsal gradient, with different types of neurons generated at specific dorsal-ventral positions
- The ventral spinal cord gives rise to and interneurons, while the dorsal spinal cord generates and interneurons
- The spatial patterning of neurogenesis in the spinal cord is regulated by , such as (Shh) from the ventral floor plate and BMPs and Wnts from the dorsal roof plate
Temporal regulation of neurogenesis
- The temporal regulation of neurogenesis is controlled by a combination of cell-intrinsic mechanisms, such as the expression of specific transcription factors, and cell-extrinsic mechanisms, such as the availability of growth factors and signaling molecules
- Progenitor cells in the ventricular zone undergo temporal changes in their competence to generate different types of neurons and glial cells as development progresses
- The sequential generation of neurons and glial cells is orchestrated by the coordinated expression of transcription factors, such as , , and in the developing cerebral cortex
Neurogenesis in central nervous system formation
Importance of neurogenesis in establishing the central nervous system
- Neurogenesis is a critical process in the formation of the central nervous system, as it generates the diverse cell types that make up the brain and spinal cord
- Proper regulation of neurogenesis is essential for the establishment of the correct number and types of neurons and glial cells in the developing nervous system
- Neurogenesis contributes to the formation of the complex cytoarchitecture of the brain, including the layered structure of the cerebral cortex and the nuclei of the basal ganglia and thalamus
Consequences of disrupted neurogenesis
- Disruptions in neurogenesis can lead to neurodevelopmental disorders, such as (reduced brain size) and (smooth brain surface), highlighting the importance of this process in normal brain development
- Genetic mutations affecting key regulators of neurogenesis, such as the microcephaly-associated gene (abnormal spindle-like microcephaly-associated) or the lissencephaly-associated gene , can cause severe brain malformations and intellectual disability
- Environmental factors, such as maternal infections () or exposure to toxins (alcohol) during pregnancy, can also disrupt neurogenesis and lead to neurodevelopmental disorders
Neurogenesis in the adult brain and its implications
- Neurogenesis is not limited to embryonic development; it also occurs in specific regions of the adult brain, such as the and subventricular zone, and may contribute to learning, memory, and brain plasticity
- Adult neurogenesis in the hippocampus has been implicated in the formation of new memories and the maintenance of
- Understanding the mechanisms that regulate neurogenesis can provide insights into the development of stem cell-based therapies for neurological disorders and injuries, such as stroke, traumatic brain injury, and neurodegenerative diseases (Alzheimer's disease, Parkinson's disease)
Key Terms to Review (39)
Aspm: ASPM (abnormal spindle-like microcephaly associated protein) is a gene that plays a crucial role in neurogenesis, specifically in the regulation of neural progenitor cell proliferation and differentiation. This gene is essential for proper brain development, as mutations in ASPM have been linked to microcephaly, a condition characterized by reduced brain size and cognitive impairment. By influencing the balance between self-renewal and differentiation of neural stem cells, ASPM contributes to the overall architecture and functionality of the developing brain.
Astrocytes: Astrocytes are star-shaped glial cells in the central nervous system that support neurons and maintain homeostasis, providing structural and metabolic support. They play a critical role in neurotransmitter uptake, regulating blood flow, and forming the blood-brain barrier, linking them closely to neurogenesis and the cellular makeup of the nervous system.
Asymmetric cell division: Asymmetric cell division is a process where a parent cell divides to produce two daughter cells that are not identical, often resulting in one cell maintaining stem cell properties while the other differentiates into a specialized cell type. This mechanism is crucial during the early stages of neurogenesis, as it allows for the generation of diverse neuronal populations from a limited number of neural stem cells, enabling proper brain development and function.
Basic helix-loop-helix: Basic helix-loop-helix (bHLH) is a protein structural motif that plays a crucial role in the regulation of gene expression, particularly during the processes of neural induction and neurogenesis. This motif consists of two alpha-helices connected by a loop, and it is essential for dimerization and binding to DNA at specific E-box sequences, influencing the development and differentiation of neural tissues.
Bmp signaling: BMP signaling, or Bone Morphogenetic Protein signaling, is a crucial pathway in cellular communication that regulates various developmental processes, including neural induction and neurogenesis. This signaling pathway involves the binding of BMPs to specific receptors on target cells, activating downstream signaling cascades that influence cell fate decisions during early development. Through these processes, BMP signaling plays a vital role in determining whether progenitor cells will differentiate into neural or non-neural lineages.
Cognitive Flexibility: Cognitive flexibility is the mental ability to switch between thinking about different concepts, or to think about multiple concepts simultaneously. It allows individuals to adapt their thinking and behavior in response to changing environments, new information, or unexpected circumstances, playing a crucial role in learning and problem-solving. This flexibility is essential for various cognitive processes, influencing everything from emotional regulation to language development.
Dorsal ectoderm: Dorsal ectoderm is a region of the developing embryo that gives rise to the neural plate, which eventually forms the central nervous system. This area is crucial during early embryonic development, as it plays a significant role in neural induction and neurogenesis by responding to signaling molecules that instruct cells to become neural tissue.
Fgf signaling: Fibroblast growth factor (fgf) signaling refers to a complex network of interactions involving fibroblast growth factors, which are crucial for regulating various biological processes such as cell growth, development, and tissue repair. This signaling pathway is particularly important during early embryonic development, as it plays a significant role in neural induction and neurogenesis by influencing the differentiation of neural progenitor cells and the formation of the central nervous system.
Hippocampus: The hippocampus is a crucial brain structure located in the medial temporal lobe, primarily involved in the formation and consolidation of new memories and spatial navigation. Its role extends to various cognitive functions, linking it to emotional responses and learning processes.
Inside-out pattern: The inside-out pattern refers to the specific way in which neurons are generated and migrate during brain development, where younger neurons are formed and positioned on the inside layers of the developing cortex, while older neurons occupy the outer layers. This layered organization is critical for establishing the functional architecture of the brain, allowing for the proper integration of neural circuits. Understanding this pattern is key to comprehending how different types of neurons are spatially arranged and interact within the cerebral cortex.
Lis1: Lis1 is a protein that plays a crucial role in the regulation of neuronal migration and cytoskeletal dynamics during brain development. It is essential for proper neuronal placement and is linked to disorders such as lissencephaly, where the brain has an abnormal structure due to impaired migration of neurons.
Lissencephaly: Lissencephaly is a rare brain malformation characterized by the absence of normal brain folds (gyri) and grooves (sulci), resulting in a smooth cerebral surface. This condition arises due to disruptions in neural induction and neurogenesis during early brain development, affecting the formation and migration of neurons. Lissencephaly can lead to various neurological deficits, including developmental delays and seizures, as it impacts essential cognitive and motor functions.
Microcephaly: Microcephaly is a medical condition characterized by an unusually small head size, which often indicates abnormal brain development. This condition can arise due to genetic factors, environmental influences, or infections during pregnancy, affecting the process of neural induction and neurogenesis, which are critical for normal brain growth and function.
Morphogen gradients: Morphogen gradients are concentration gradients of signaling molecules that play a crucial role in cellular communication and the regulation of tissue patterning during embryonic development. These gradients help determine the fate of cells by providing positional information, influencing processes like neural induction and neurogenesis, where specific cell types emerge based on their location relative to the gradient's source.
Motor neurons: Motor neurons are specialized nerve cells responsible for transmitting signals from the central nervous system to muscles, enabling movement and coordination. These neurons play a crucial role in the motor system by connecting the brain and spinal cord to skeletal muscles, allowing for voluntary and reflexive movements.
Neural induction: Neural induction is the process by which specific regions of the embryo are instructed to develop into neural tissue, forming the basis for the central nervous system. This process involves signaling mechanisms that prompt precursor cells in the ectoderm to differentiate into neurons and glial cells, ultimately leading to neurogenesis. Neural induction is crucial for establishing the correct neural structures and functions during embryonic development.
Neural plate: The neural plate is a specialized region of ectodermal tissue that forms during early embryonic development and serves as the precursor to the nervous system. It undergoes a process called neurulation, where it folds to create the neural tube, which eventually differentiates into the brain and spinal cord. This structure is essential for proper neural induction and the subsequent formation of neurons and glial cells.
Neural progenitor cells: Neural progenitor cells are a type of stem cell that has the potential to differentiate into various types of neurons and glial cells within the nervous system. These cells are crucial during development, as they play a central role in neurogenesis, the process by which new neurons are generated from neural stem cells. Neural progenitor cells can also be found in the adult brain, where they contribute to ongoing neurogenesis and repair mechanisms.
Neural Stem Cells: Neural stem cells are unique, multipotent cells capable of differentiating into various types of neural cells, including neurons, astrocytes, and oligodendrocytes. They play a crucial role in the development and maintenance of the nervous system, particularly during processes like neural induction and neurogenesis, where they give rise to the diverse cell types that make up the brain and spinal cord.
Neural tube formation: Neural tube formation is the process during embryonic development in which the neural plate folds and fuses to create the neural tube, which eventually develops into the central nervous system, including the brain and spinal cord. This crucial event marks the beginning of neurogenesis and is influenced by various signaling pathways and cellular interactions, setting the foundation for proper nervous system development.
Neurod: Neurod is a transcription factor that plays a critical role in the regulation of neurogenesis, the process by which new neurons are generated from neural stem cells. It is involved in the specification and differentiation of neuronal progenitor cells into mature neurons, making it essential for the development of the nervous system during embryogenesis and beyond.
Neurogenin: Neurogenin is a class of basic helix-loop-helix (bHLH) transcription factors that play a crucial role in the process of neurogenesis, particularly in the development of neural progenitor cells into neurons. By activating specific genes, neurogenins regulate the differentiation of these progenitor cells, influencing the formation of the nervous system during embryonic development.
Neurons: Neurons are specialized cells in the nervous system that transmit information through electrical and chemical signals. They are the basic building blocks of the nervous system, playing a critical role in communication between different parts of the body, including the brain and spinal cord. The development and differentiation of neurons are crucial processes during early brain formation and function, impacting neurogenesis and overall neural connectivity.
Notch signaling: Notch signaling is a fundamental cell communication pathway that plays a crucial role in regulating cell fate decisions during development and in adult tissues. It involves the interaction between Notch receptors on one cell and their ligands on adjacent cells, leading to a cascade of intracellular events that determine whether a cell becomes a neuron or remains a progenitor cell, among other fates.
Olig2: Olig2 is a transcription factor that plays a crucial role in the development of oligodendrocytes, the myelinating cells of the central nervous system. It is essential for the specification and differentiation of oligodendrocyte progenitor cells during neural development, linking it closely to processes involved in neural induction and neurogenesis.
Oligodendrocytes: Oligodendrocytes are specialized glial cells in the central nervous system responsible for producing myelin, which insulates axons and enhances the speed of electrical signal transmission. These cells play a crucial role in maintaining neuronal health and function, contributing significantly to neural induction and neurogenesis by providing structural support and metabolic assistance to neurons.
Pax6: Pax6 is a critical transcription factor that plays an essential role in the development of the nervous system, particularly in neural induction and neurogenesis. It is involved in the formation of the eyes and forebrain, regulating gene expression that leads to the differentiation of neural precursor cells. Pax6's influence extends to various aspects of neuronal development, making it a key player in shaping brain structures and functions.
Retinoic acid signaling: Retinoic acid signaling refers to the process through which retinoic acid, a metabolite of vitamin A, regulates gene expression and plays a crucial role in the development of various tissues, including the nervous system. This signaling pathway is vital for neural induction and neurogenesis, influencing cell fate determination, proliferation, and differentiation of neural progenitor cells.
Sensory neurons: Sensory neurons are specialized nerve cells responsible for converting external stimuli from the environment into electrical impulses that are sent to the central nervous system. They play a critical role in enabling organisms to perceive and respond to sensory information, such as touch, taste, sight, sound, and smell, thus facilitating interaction with the surrounding world.
Sonic hedgehog: Sonic hedgehog (Shh) is a signaling molecule that plays a crucial role in embryonic development, particularly in neural induction and neurogenesis. It is part of the Hedgehog signaling pathway, which regulates cell growth, differentiation, and patterning during development. Sonic hedgehog is essential for the proper formation of structures in the brain and spinal cord, influencing the fate of neural precursor cells and promoting the development of various neural tissues.
Sox10: Sox10 is a transcription factor that plays a crucial role in the development of the nervous system and is particularly important for neural crest cell development. It helps regulate the expression of genes necessary for the differentiation and migration of these cells, which contribute to various structures in the peripheral nervous system, including neurons and glial cells. Sox10 also has implications in neurogenesis, impacting the formation and maturation of neural tissues.
Spemann organizer: The Spemann organizer is a critical region of cells located in the dorsal lip of the blastopore in amphibian embryos, particularly studied in frogs. It plays a crucial role in the early stages of development by inducing the formation of neural tissue and establishing body axis patterns. The organizer's ability to influence neighboring cells is fundamental to understanding neural induction and neurogenesis during embryonic development.
Subventricular zone: The subventricular zone (SVZ) is a region in the brain located along the lateral ventricles, known for its role in generating new neurons throughout life. This area is crucial for neurogenesis, particularly in the context of olfactory function and learning, as it contains neural stem cells that can differentiate into various types of neurons and glial cells. The SVZ plays a significant role in both development and adult brain plasticity, contributing to various cognitive processes.
Symmetric cell division: Symmetric cell division is a process in which a parent cell divides to produce two daughter cells that are genetically identical and share the same fate. This type of division is crucial during early development, particularly in the context of generating neural progenitor cells that can later differentiate into various types of neurons and glia.
Tbr1: tbr1 is a transcription factor that plays a crucial role in the development of the brain, particularly in the specification of certain neuronal populations. It is involved in neural induction and neurogenesis, guiding progenitor cells to differentiate into specific types of neurons during embryonic development. This factor is important for establishing the proper identity and function of neurons, especially in the cortex.
Tbr2: tbr2, or T-box brain gene 2, is a transcription factor that plays a vital role in neurogenesis, particularly during the development of the central nervous system. It is essential for the differentiation of neural progenitor cells into neurons and helps regulate the timing and type of neurons generated during brain development.
Ventricular zone: The ventricular zone is a region of the developing brain that lines the ventricles and is crucial for neurogenesis, the process of generating new neurons. This zone is where neural stem cells reside and proliferate, ultimately giving rise to the various types of neurons and glial cells that populate the brain. As development progresses, cells migrate away from this zone to form the brain's layered structures.
Wnt signaling: Wnt signaling is a complex cell communication pathway that plays a critical role in regulating cell fate, proliferation, and differentiation during development. This pathway is crucial for processes such as neural induction and neurogenesis, influencing how stem cells develop into neurons and other cell types in the nervous system. By modulating gene expression through β-catenin-dependent and β-catenin-independent mechanisms, Wnt signaling contributes to the formation of neural structures and the overall organization of the brain.
Zika virus: Zika virus is an arthropod-borne virus primarily transmitted to humans through the bite of infected Aedes mosquitoes. The virus gained significant attention due to its association with severe birth defects, particularly microcephaly, in babies born to mothers infected during pregnancy, impacting neural development and neurogenesis.