Simpson-Golabi-Behmel syndrome (SGBS) is an X-linked condition characterized by pre- and postnatal overgrowth with visceral and skeletal anomalies. To identify the causative gene, breakpoints in two female patients with X;autosome translocations were identified. The breakpoints occur near the 5' and 3' ends of a gene, GPC3, that spans more than 500 kilobases in Xq26; in three families, different microdeletions encompassing exons cosegregate with SGBS. GPC3 encodes a putative extracellular proteoglycan, glypican 3, that is inferred to play an important role in growth control in embryonic mesodermal tissues in which it is selectively expressed. Initial western- and ligand-blotting experiments suggest that glypican 3 forms a complex with insulin-like growth factor 2 (IGF2), and might thereby modulate IGF2 action.

FOXL2 mutations cause gonadal dysgenesis or premature ovarian failure (POF) in women, as well as eyelid/forehead dysmorphology in both sexes (the 'blepharophimosis-ptosis-epicanthus inversus syndrome', BPES). Here we report that mice lacking Foxl2 recapitulate relevant features of human BPES: males and females are small and show distinctive craniofacial morphology with upper eyelids absent. Furthermore, in mice as in humans, sterility is confined to females. Features of Foxl2 null animals point toward a new mechanism of POF, with all major somatic cell lineages failing to develop around growing oocytes from the time of primordial follicle formation. Foxl2 disruption thus provides a model for histogenesis and reproductive competence of the ovary.

The discovery that the SRY gene induces male sex in humans and other mammals led to speculation about a possible equivalent for female sex. However, only partial effects have been reported for candidate genes experimentally tested so far. Here we demonstrate that inactivation of two ovarian somatic factors, Wnt4 and Foxl2, produces testis differentiation in XX mice, resulting in the formation of testis tubules and spermatogonia. These genes are thus required to initiate or maintain all major aspects of female sex determination in mammals. The two genes are independently expressed and show complementary roles in ovary morphogenesis. In addition, forced expression of Foxl2 impairs testis tubule differentiation in XY transgenic mice, and germ cell-depleted XX mice lacking Foxl2 and harboring a Kit mutation undergo partial female-to-male sex reversal. The results are all consistent with an anti-testis role for Foxl2. The data suggest that the relative autonomy of the action of Foxl2, Wnt4 and additional ovarian factor(s) in the mouse should facilitate the dissection of their respective contributions to female sex determination.

Genetic control of female sex differentiation from a bipotential gonad in mammals is poorly understood. We find that mouse XX gonads lacking the forkhead transcription factor Foxl2 form meiotic prophase oocytes, but then activate the genetic program for somatic testis determination. Pivotal Foxl2 action thus represses the male gene pathway at several stages of female gonadal differentiation. This suggests the possible continued involvement of sex-determining genes in maintaining ovarian function throughout female reproductive life.

Background: Partial loss of function of the transcription factor FOXL2 leads to premature ovarian failure in women. In animal models, Foxl2 is required for maintenance, and possibly induction, of female sex determination independently of other critical genes, e.g., Rspo1. Here we report expression profiling of mouse ovaries that lack Foxl2 alone or in combination with Wnt4 or Kit/c-Kit.