Correct dosage of Fog2 and Gata4 transcription factors is critical for fetal testis development in mice

Abstract

Previous reports suggested that humans and mice differ in their sensitivity to the genetic dosage of transcription factors that play a role in early testicular development. This difference implies that testis determination might be somewhat different in these two species. We report that the Fog2 and Gata4 transcription factors are haploinsufficient for testis determination in mice. Whether gonadal sex reversal occurs depends on genetic background (i.e., modifier genes). gonadal sex reversal ͉ haploinsufficiency ͉ sex determination ͉ Sry ͉ Sox9 D uring human fetal development, differentiation of the bipotential gonads into ovaries or testes depends on the proper dosage of transcription factors. For example, the presence of only a single functional copy of the autosomal transcription factor-encoding genes SF1, SOX9, or WT1 can result in the development of XY females, and duplication of a chromosomal region containing SOX9 can lead to the development of XX males (1-5). In contrast, the proper dosage of the transcription factors Sf1, Sox9, and Wt1 appears not to affect testicular development in mice because XY mice containing only a single copy of these genes develop testes (6-9). This apparent species difference suggested that the correct dosage of gonadal sexdetermining transcription factors is necessary for normal testis development in humans, whereas mice are less sensitive to these gene dosage effects (10-12).Studies in our laboratory indicate that genetic background plays an essential role in the process of gonadal sex determination in mice. Specifically, mice of the C57BL/6J (B6) inbred strain are exceptionally sensitive to disturbances in the early events of gonad development and thus provide a genetic ''litmus test'' for identifying genes that cause sex reversal. For example, the Sry POS gene carried on the Mus domesticus poschiavinus Y chromosome causes ovarian tissue development when present in C57BL/6J (B6) mice but not in DBA/2J (D2) or (B6 ϫ D2)F1 mice (13,14), and a mutant allele of the X-linked transcription factor Dax1 (Nr0b1) causes gonadal sex reversal in B6 but not D2 or (B6 ϫ D2)F1 XY mice (15). This ''B6 sensitivity'' is even stronger if the AKR/J Y chromosome (Y AKR ) is present. For example, if B6 mice are heterozygous for the T Orl mutation, they develop testes. If the Y AKR chromosome is present, however, they develop ovaries (16,17). These findings suggest that genetic background, not species differences, could explain apparent differences in transcription factor dosage sensitivity for gonad development in XY humans and mice. The fact that not all XY humans are sex-reversed if only a single copy of a normal SF1 or WT1 allele is present (18-20) supports this possibility, as does the fact that XY males carrying a mutant SRY gene can pass this allele on to XY daughters (for review, see ref. 21).To test the hypothesis that testis determination in XY mice is sensitive to levels of transcription factor gene dosage in a genetic background-dependent manner, we conducted experiments to determine wh...

A large-scale analysis of tissue-specific pathology and gene expression of human disease genes and complexes

“…DAX1, which leads to XY sex reversal both when overexpressed, by inhibiting SF1 (26), and when inactivated, as it is required for testis differentiation by regulating expression of SOX9 (30). Although the activity of SF1, DAX1, and SOX9 is required for testis differentiation, development, and maintenance, none of these genes are essential for ovarian development and maintenence (30)(31)(32)(33). Here, we identify a transcriptional regulation complex (GO:0006355: P ϭ 1.9E-8) containing DAX1, SF1, and SOX9, all of which are known to be associated with sex reversal (P ϭ 6.9E-6).…”

Loss-of-function mutation in GATA4 causes anomalies of human testicular development

“…The critical role for GATA4 in gonadal development is highlighted by Gata4 ki mice that have a p.Val217Gly mutation in the N-terminal zinc finger domain (14). This knock-in mutation abrogates the interaction of GATA4 with the cofactor FOG2, and these animals display severe anomalies of testis development (15,16).…”

“…In vitro FOG2 represses GATA4-dependent transcription of AMH in primary Sertoli cell cultures (18). Although the mechanism of FOG-2 and GATA4 interaction in the gonad is not well defined, it is essential that a direct physical interaction between GATA4 and FOG2 be maintained, because abrogation of the same results in abnormal testis development in mice (14)(15)(16). NR5A1, also termed Ad4 binding protein (Ad4BP) or steroidogenic factor 1 (SF-1), is a key transcriptional regulator of genes involved in sexual development, many of which are also regulated by GATA4 (19)(20)(21).…”

The effect of human GATA4 gene mutations on the activity of target gonadal promoters

“…Initial in vitro work characterizing GATA4 target genes in gonadal cells (LaVoie 2003, Tremblay & Viger 2003b, Viger et al 2004, along with subsequent genetic studies in the mouse (Tevosian et al 2002, Bouma et al 2007, Manuylov et al 2007, has provided strong evidence that the GATA4 transcription factor plays a central role in reproductive function. Despite the lack of direct genetic evidence, the expectation is that this critical role extends to human reproductive function.…”

“…The impact of these mutations on GATA4 function outside of the cardiac system has not been investigated. This includes the reproductive tract where GATA4 has been shown to play a critical role in early gonadal morphogenesis, at least in the mouse (Tevosian et al 2002, Bouma et al 2007, Manuylov et al 2007. In the present study, we have recreated five human GATA4 mutations (listed in Table 1), known to affect heart function, in the rodent protein and tested their functional properties -DNA-binding capacity, transactivation potential, physical and functional interaction with known regulatory partners -on a variety of GATA4-dependent gonadal promoters.…”