Abstract
During maturation of the brain, neurons and glia are formed sequentially. Neurogenesis occurs in the embryonic stage and astrogliogenesis in the postnatal stage. This orderly development is maintained partly by group of bHLH (basic Helix-Loop-Helix) transcription factors. Among the bHLH transcription factors, neurogenins (Ngns) play a significant role to regulate neurogenesis and astrogliogenesis. This review article is focused on understanding more about neurogenins and its influence on the formation of neurons and astroglia.
Keywords: Neurogenins, Ngn1, Ngn2, astrogliogenesis, neurogenesis, neural stem/progenitor cells (NSPCs), JAK-STAT.
Abbreviations: NSPC: Neural stem/progenitor cells Ngn: Neurogenins…show more content…
Ngns (class II bHLH transcription factors) are known as pro-neural factors as they are necessary to initiate differentiation of NSPCs and are important to specify a neuronal subtype[3]. Ngns activate downstream several pro-neural factors for the formation of neurons from NSPCs. Earlier studies showed that development of neurogenic machinery is mediated by cascade of transcriptional activation which begins by activation of Ngn1 and Ngn2. This then activates NeuroD1 and NeuroD6 (other bHLH factors). In turn NeuroD1 and NeuroD6 activates Nsc1 which then activated terminal transcription factors and triggers neurogenesis[4]. Thoma et al observed that Ngn2 alone is sufficient to induce neuronal differentiation in embryonic stem cells. In this study they used murine embryonic stem cells and transfected with Ngn2 expression and after five days post transfection they observed that cells expressed Tuj1 and MAP2 (both are neuronal markers). This indicates that presence of a single pro-neural factor as well could promote neurogenesis. Ectopic expression of Ngn2 was sufficient to form mature neurons from embryonic stem cells[5]. Ngn2 was also seen to have a vital role in the development of dentate gyrus (DG). Galichet et al observed that in Ngn2 knockout mice there was a strong reduction in the size of DG. They also showed a marked reduction in the number of neural stem progenitors in DG. These Ngn2 mutant
Ngns (class II bHLH transcription factors) are known as pro-neural factors as they are necessary to initiate differentiation of NSPCs and are important to specify a neuronal subtype[3]. Ngns activate downstream several pro-neural factors for the formation of neurons from NSPCs. Earlier studies showed that development of neurogenic machinery is mediated by cascade of transcriptional activation which begins by activation of Ngn1 and Ngn2. This then activates NeuroD1 and NeuroD6 (other bHLH factors). In turn NeuroD1 and NeuroD6 activates Nsc1 which then activated terminal transcription factors and triggers neurogenesis[4]. Thoma et al observed that Ngn2 alone is sufficient to induce neuronal differentiation in embryonic stem cells. In this study they used murine embryonic stem cells and transfected with Ngn2 expression and after five days post transfection they observed that cells expressed Tuj1 and MAP2 (both are neuronal markers). This indicates that presence of a single pro-neural factor as well could promote neurogenesis. Ectopic expression of Ngn2 was sufficient to form mature neurons from embryonic stem cells[5]. Ngn2 was also seen to have a vital role in the development of dentate gyrus (DG). Galichet et al observed that in Ngn2 knockout mice there was a strong reduction in the size of DG. They also showed a marked reduction in the number of neural stem progenitors in DG. These Ngn2 mutant
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