Mutations in MAP3K1 tilt the balance from SOX9/FGF9 to WNT/β-catenin signaling

摘要

In-framemissense and splicing mutations (resulting in a 2 amino acid insertion or a 34 amino acid deletion) dispersed through the MAP3K1 gene tilt the balance from the male to female sex-determining pathway, resulting in 46,XYdisorder of sex development. TheseMAP3K1mutationsmediate this balance by enhancing WNT/β-catenin/ FOXL2expressionandb-catenin activityandbyreducingSOX9/FGF9/FGFR2/SRYexpression.These effects are mediated at multiple levels involving MAP3K1 interaction with protein co-factors and phosphorylation of downstream targets. In transformed B-lymphoblastoid cell lines and NT2/D1 cells transfected with wild-typeormutant MAP3K1 cDNAs under control of the constitutive CMV promoter, these mutations increased binding of RHOA, MAP3K4, FRAT1 and AXIN1 and increased phosphorylation of p38 and ERK1/2. Overexpressing RHOA or reducing expression of MAP3K4 in NT2/D1 cells produced phenocopies of the MAP3K1 mutations. Using siRNA knockdown of RHOA or overexpressing MAP3K4 in NT2/D1 cells produced anti-phenocopies. Interestingly, the effects of the MAP3K1 mutations were rescued by co-transfection with wild-type MAP3K4. Although MAP3K1is not usually required for testis determination, mutations in this gene can disrupt normal development through the gains of function demonstrated in this study.