Pathway: EPHA-mediated growth cone collapse
Reactions in pathway: EPHA-mediated growth cone collapse :
EPHA-mediated growth cone collapse
EPH/Ephrin signaling is coupled to Rho family GTPases such as Rac, Rho and Cdc42 that connect bidirectional receptor-ligand interactions to changes in the actin cytoskeleton (Noren & Pasquale 2004, Groeger & Nobes 2007). RHOA regulates actin dynamics and is involved in EPHA-induced growth cone collapse. This is mediated by ephexins. Ephexin, a guanine nucleotide exchange factor for Rho GTPases, interacts with the EPHA kinase domain and its subsequent activation differentially affects Rho GTPases, such that RHOA is activated, whereas Cdc42 and Rac1 are inhibited. Activation of RHOA, and inhibition of Cdc42 and Rac, shifts actin cytoskeleton to increased contraction and reduced expansion leading to growth-cone collapse (Shamah et al. 2001, Sahin et al. 2005). The activation of EPH receptors in growing neurons typically, but not always, leads to a growth cone collapse response and retraction from an ephrin-expressing substrate (Poliakov et al. 2004, Pasquale 2005). EPHA-mediated repulsive responses prevent axons from growing into regions of excessive ephrin-A concentration, such as the posterior end of the superior colliculus (Pasquale 2005).
Neurogenesis is the process by which neural stem cells give rise to neurons, and occurs both during embryonic and perinatal development as well as in specific brain lineages during adult life (reviewed in Gotz and Huttner, 2005; Yao et al, 2016; Kriegstein and Alvarez-Buylla, 2009).
As early steps towards capturing the array of processes by which a fertilized egg gives rise to the diverse tissues of the body, examples of several processes have been annotated. Aspects of processes involved in most developmental processes, transcriptional regulation of pluripotent stem cells, gastrulation, and activation of HOX genes during differentiation are annotated. More specialized processes include nervous system development , aspects of the roles of cell adhesion molecules in axonal guidance and myogenesis, transcriptional regulation in pancreatic beta cell, cardiogenesis, transcriptional regulation of granulopoeisis, transcriptional regulation of testis differentiation, transcriptional regulation of white adipocyte differentiation, and molecular events of "nodal" signaling, LGI-ADAM interactions, and keratinization.