8.A.40.1.20
Tetraspanin-12, Tspan12, of 305 aas and 4 TMSs.  Regulator of cell surface receptor signal transduction. Plays a central role in retinal vascularization by regulating norrin (NDP) signal transduction. Acts in concert with norrin (NDP) to promote FZD4 multimerization and subsequent activation of FZD4, leading to accumulation of beta-catenin (CTNNB1) and stimulation of LEF/TCF-mediated transcriptional programs (Lafleur et al. 2009). It activates ADAM10-dependent cleavage activity of amyloid precursor protein (APP) (Xu et al. 2009).  The biology of tetraspanins and how they interact with APP processing pathways have been reviewed (Seipold and Saftig 2016).