ABSTRACT
Notch signaling is an evolutionarily conserved juxtacrine pathway in different species. The pathway is activated by ligand engagement to the receptor in opposite cells, which initiates proteolytic cleavage of the receptor followed by the release of the active Notch intracellular domain, which translocates into the nucleus to form a transcriptionally active complex with the aid of deoxyribonucleic acid (DNA )binding protein and coactivators. It regulates the basic cellular events like self-renewal of stem cells, proliferation, differentiation, cell fate, pattern formation and apoptosis. Functional versatility observed in Notch is due to spatiotemporal distribution and various permutations-combinations of ligands and receptors. Notch signaling is reported to be a key regulator in stem cell maintenance and proliferation in germline cells during spermatogenesis. Its importance is registered from worms to humans. In Caenorhabditis elegans, it regulates germ cell maintenance and differentiation, whereas in Drosophila it helps in niche cells formation, along with cross talk with other main pathways like janus kinase/signal transducers and activators of transcription(JAK-STAT), Bone Morphogenetic proteins( BMP), Hedgehog and Wnt. Hypo- and hyperactivation of any of the components in the Notch pathway are reported to cause male infertility, due to disruption of stem cell niche in testes, which indirectly affect germ cell proliferation and differentiation. In most cases, premature arrest of the germ cell is observed along with reduced testes size and sperm count. This chapter expounds the Notch signaling pathway with special emphasis on its role in regulating the spermatogenesis events and its multifactorial effects brought by cross talk with other pathways.
