Neurons are the cells specialized to receive, conduct, and transmit signal to the nervous system. The development of neurons starts early during the embryogenesis. After the fusion of sperm and egg, zygote is formed which is further divided to form blastula eventually leading to gastrula stage of development. Gastrulation begins as invagination of cells in the embryo leading to the formation of three germ layers. Formation of notochord from the mesodermal layer marks the beginning of neurulation. The ectodermal layer above the notochord gives rise to the vertebral nervous system as the tissue thickens and flattens to become the neural plate which folds to form the neural groove ultimately this folding leads to the formation of neural tube.
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The polarization of these neurons occurs in several different stages. The lamellipodia, spherical neurons, starts to get extension of cytoskeleton to send out projections. Immature neurites are formed which eventually leads to physical projection of arms/branches forming axon and dendrites. The axon terminal increases in surface area and leads to maturation of the neuron. Par-3 is important factor for the extension of neurons as they tend to turn everything to axons so regulation of Par-3 and restriction to one end of the neuron is vital process in the formation of the neuron. At the leading edge of the elongating axon is the highly motile growth cone, which possesses cell-surface receptors for extracellular signals. The neurites move towards or away from the source depending on the guidance cues (attractive/repulsive). The growth cone is comprised of cytoskeletal element (microtubules and actin): Lamellipodia is the base of the cone which is comprised of actin mesh work stabilized by microtubule whereas Filopodia is the finger-like projection entirely comprised of actin. The movement of growth cone is regulated by polymerization/depolymerization of actin and tubulin. Polymerization is defined as the addition of strands in G-actin (monomeric Globular actin) to form F-actin (polymeric Fibrous actin). Various Rho family GTPases like RAC1 and CDC 42 activates ARP 2/3 and inhibits cofilin and promote polymerization of F-actin. Also, Rho A inhibits cofilin and promotes prolifin and polymerization. On the other hand, RHO V promotes cofilin aiding to depolymerization by protecting them from being inhibited. Different molecules like neural cell adhesion molecules (N-CAMs), L1 CAMs and N-Cadherin are major proteins that mediates correct axonal navigation by eliciting intracellular signaling within the
The polarization of these neurons occurs in several different stages. The lamellipodia, spherical neurons, starts to get extension of cytoskeleton to send out projections. Immature neurites are formed which eventually leads to physical projection of arms/branches forming axon and dendrites. The axon terminal increases in surface area and leads to maturation of the neuron. Par-3 is important factor for the extension of neurons as they tend to turn everything to axons so regulation of Par-3 and restriction to one end of the neuron is vital process in the formation of the neuron. At the leading edge of the elongating axon is the highly motile growth cone, which possesses cell-surface receptors for extracellular signals. The neurites move towards or away from the source depending on the guidance cues (attractive/repulsive). The growth cone is comprised of cytoskeletal element (microtubules and actin): Lamellipodia is the base of the cone which is comprised of actin mesh work stabilized by microtubule whereas Filopodia is the finger-like projection entirely comprised of actin. The movement of growth cone is regulated by polymerization/depolymerization of actin and tubulin. Polymerization is defined as the addition of strands in G-actin (monomeric Globular actin) to form F-actin (polymeric Fibrous actin). Various Rho family GTPases like RAC1 and CDC 42 activates ARP 2/3 and inhibits cofilin and promote polymerization of F-actin. Also, Rho A inhibits cofilin and promotes prolifin and polymerization. On the other hand, RHO V promotes cofilin aiding to depolymerization by protecting them from being inhibited. Different molecules like neural cell adhesion molecules (N-CAMs), L1 CAMs and N-Cadherin are major proteins that mediates correct axonal navigation by eliciting intracellular signaling within the