Meta-Biol

• Pathways

Despite high-affinity multimeric interaction between EPHs and ephrins (EFNs), the cellular response to EPH-EFN engagement is usually repulsion between the two cells and signal termination. These repulsive responses induce an EPH receptor-expressing cell to retract from an ephrin-expressing cell after establishing initial contact. The repulsive responses mediated by EPH receptors in the growth cone at the leading edge of extending axons and in axonal collateral branches contribute to the formation of selective neuronal connections. It is unclear how high affinity trans-cellular interactions between EPHs and ephrins are broken to convert adhesion into repulsion. Two possible mechanisms have been proposed for the repulsion of EPH-EFN bearing cells: the first one involves regulated cleavage of ephrin ligands or EPH receptors by transmembrane proteases following cell-cell contact, while the second one is rapid endocytosis of whole EPH:EFN complexes during the retraction of the interacting cells or neuronal growth cones (Egea & Klein 2007, Janes et al. 2005). RAC also plays an essential role during growth cone collapse by promoting actin polymerization that drives membrane internalization by endocytosis (Marston et al. 2003).

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.