LAUSR

Hirschsprung disease (HSCR) is a complex developmental disorder characterised by the lack of enteric neurons in distal portions of the gut. Importantly, HSCR presents a dramatic sex bias with at least 4 times more males affected than females for reasons that are unknown. Genome-wide mapping studies of patients have failed to identify sex-linked genes associated with HSCR while experimental studies have largely overlooked the effects of sex. Here, we exploit several mouse models of HSCR, including Sox10LacZ/+, Ret 51/51 and Ret S697a/S697a, to investigate the sex bias. We identify a difference in phenotype severity at early postnatal stages in all the models, with males exhibiting greater extents of hypoganglionosis or aberrant ENS in the colon compared to females. At embryonic stage E14.5, Sox10LacZ/+ and Ret 51/51 guts showed no obvious differences in phenotype severity. This defines the critical period during which the sex bias may operate. To identify sex-specific differences in gene expression we performed RNAseq analyses on populations of normal neural crest cell derivatives and mesenchymal cells isolated from Wnt1-cre;R26YFP E15.5 embryonic guts. Preliminary analyses suggest that males have higher levels of apoptosis in enteric neural crest cells, while females have increased levels of proliferation. Further transcriptomic analyses performed at additional embryonic stages as well as in our HSCR models will allow us to identify candidate genes and specific pathways that are upregulated or downregulated in males and females, causing males to be more affected. To investigate whether these sex differences are due to sex-linked genes or sex hormones, we will also exploit the “four-core genotype model” to study our mutations of interest in XX and XY males and XX and XY females. In combination with our transcriptomic analyses, this provides groundwork to understand the sex-linked disease mechanisms leading to the sex bias of HSCR.