09-P033 Expression of SOX3 in the urogenital ridge is associated with XX male sex reversal in mice

Abstract

In this study we have developed an exvivo lung explant system, where distal lung tissue from E18.5 Glucocorticoid Receptor (GR)-null mice have been exposed to at-RA. Whole genome microarrays and quantitative Real-time PCR have been utilized to identify and confirm GR-antagonised RA-responsive genes.Only the common rarb2/4 transcript and tcf15 (paraxis) were found to match this criteria. We propose that the antagonistic effects on alveolarisation by GC and RA are regulated by signaling through the rarb2/4-promoter. Furthermore, the transcriptional activation of some RA-responsive genes was dependent on the presence of GR. These genes include the RA-metabolising enzymes cyp1a1 and cyp7b1, the tight junction proteins cldn5 and cldn4 and the ECM-protein eln. These studies will provide a better understanding of the processes involved in alveolar development and the specific roles of GC-and RA-signaling.These findings may impact on the procedures used in the care of premature infants, and hence reduce the effects of respiratory distress syndrome.We have shown previously that Sox3 is expressed in the progenitor cells of the embryonic CNS and functions as a dosagedependent regulator of CNS development in mice and man. To further investigate the role of SOX3, we generated transgenic mice that contain multiple copies of a 36 kb Sox3 genomic fragment. Unexpectedly, progeny from one line (termed Sex reversed (Sr)) exhibited a markedly distorted sex ratio in favour of male offspring (77% (102/133) of Tg/+ XX adults were male). Analysis of the reproductive tract in adult sex-reversed animals indicated that all male-specific structures were present, indicating complete XX male sex reversal. Transgene expression analysis in Sr embryos demonstrated that Sox3 is ectopically upregulated in the primordium of XX and XY gonads during the sex determining window (approximately 11.0-11.25 dpc) and is expressed in the ertoli cell lineage until at least 15.5 dpc. Transgene expression in the gonad appears to be influenced by regulatory elements associated with genes that flank the integration site on chromosome 19, which may serve to reinforce testis fate determination.Importantly, morphological, gene expression and co-transfection studies indicate that SOX3 induces testis differentiation in Sr embryonic gonads by activation of Sox9 in a mechanism analo-gous to that used by the Y-linked sex determining gene Sry.Together, these data suggest that SOX3 and SRY proteins are functionally interchangeable in sex determination and provide support for the notion that Sry evolved from Sox3 via a regulatory mutation that led to its de novo expression in the early gonad. Bi-allelic mutations inWt1 combined with activating mutations in the b-catenin proto-oncogene are responsible for 15-20% of cases of Wilms' tumours. To understand the effect of Wt1 loss and b-catenin activation on kidney development and tumour development, we are currently analyzing a collection of mouse models using different Cre lines to inactivate Wt1 and/or activate mutant b-cateni...