In-frame missense 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,XY disorder of sex development. These MAP3K1 mutations mediate this balance by enhancing WNT/β-catenin/FOXL2 expression and β-catenin activity and by reducing SOX9/FGF9/FGFR2/SRY expression. 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-type or mutant 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 MAP3K1 is not usually required for testis determination, mutations in this gene can disrupt normal development through the gains of function demonstrated in this study.
Mutations in MAP3K1 tilt the balance from SOX9/FGF9 to WNT/β-catenin signaling. / J. Loke;A. Pearlman;O. Radi;O. Zuffardi;U. Giussani;R. Pallotta;G. Camerino;H. Ostrer. - In: HUMAN MOLECULAR GENETICS. - ISSN 0964-6906. - STAMPA. - 23:4(2013), pp. 1073-1083.