Sex determination in mammals is governed by antagonistic interactions of two genetic
pathways, imbalance in which may lead to disorders/differences of sex development
(DSD) in human. Among 46,XX individuals with testicular DSD (TDSD) or ovotesticular
DSD (OTDSD), testicular tissue is present in the gonad. Although the testis-determining
gene SRY is present in many cases, the etiology is unknown in most SRY-negative patients.
We performed exome sequencing on 78 individuals with 46,XX TDSD/OTDSD of unknown genetic
etiology and identified seven (8.97%) with heterozygous variants affecting the fourth
zinc finger (ZF4) of Wilms' tumor 1 (WT1) (p.Ser478Thrfs*17, p.Pro481Leufs*15, p.Lys491Glu,
p.Arg495Gln [x3], p.Arg495Gly). The variants were de novo in six families (P = 4.4
x 10(-6)), and the incidence of WT1 variants in 46,XX DSD is enriched compared to
control populations (P < 1.8 x 10(-4)). The introduction of ZF4 mutants into a human
granulosa cell line resulted in up-regulation of endogenous Sertoli cell transcripts
and Wt1(Arg495Gly/Arg495Gly) XX mice display masculinization of the fetal gonads.
The phenotype could be explained by the ability of the mutated proteins to physically
interact with and sequester a key pro-ovary factor beta-CATENIN, which may lead to
up-regulation of testis-specific pathway. Our data show that unlike previous association
of WT1 and 46,XY DSD, ZF4 variants of WT1 are a relatively common cause of 46,XX TDSD/OTDSD.
This expands the spectrum of phenotypes associated with WT1 variants and shows that
the WT1 protein affecting ZF4 can function as a protestis factor in an XX chromosomal
context.
