Generation of pattern and diversity in Central Nervous System

Central nervous system (CNS) is composed of brain and the spinal cord. Neurons constitute a major part of the developing CNS. An axon is an extension of a neuron. The brain grows as a swelling at the front (rostal) end of the neural tube and later leads to become a spinal cord (1,2). Development of the CNS involves many complex mechanisms beginning at the onset of transformation of a single layer of ectodermal cells, the neuroectoderm until the end of the differentiation process resulting into highly complex structure involving variety of neural cell types (1,2). A large number of cell types need to be arranged spatially and temporally to form a complex structure during an …show more content…

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To decide on the interneural segment specification/ Specification of neural progenitor cells-

Drosophila has been considered as a suitable model for maximum number of studies dealing with CNS development. The CNS is made of a Ventral nerve cord (VNC) and the brain proper. Early patterning gene products help in deciding the neurogenic and non- neurogenic regions of the ectoderm. Fate mapping studies had shown that the ventral neurogenic region (VNR) forms the VNC while the procephalic neurogenic region (PNR) grows into the brain. Most of the cells at VNR form the epidermoblasts. So it is a decision by the neuroectoderm to choose between neurogenesis and epidermogenesis. Two groups of genes – proneural genes that encode transcriptional regulators of bHLH family and neurogenic genes coding for Notch signal cascade, together control the distribution of neural and epidermal progenitor cells. (2)

At the neurogenic region of the ectoderm (neuroectoderm) cells differentiate as CNS progenitor cells i.e, neuroblasts (NBs). Each of the NBs has been documented as to have aquired a unique fate determined by its position and time of formation in the neuroectoderm in each of the hemisegments. Two sets of genes (anterior – posterior and dorso –ventral) decide the positional information in each of these hemisegments. A small number of CNS progenitor cells derived from one row of