title: Male-biased aganglionic megacolon in the TashT mouse line due to perturbation of silencer elements in a large gene desert of chromosome 10.
abstract: Neural crest cells (NCC) are a transient migratory cell population that generates diverse cell types such as neurons and glia of the enteric nervous system (ENS). Via an insertional mutation screen for loci affecting NCC development in mice, we identified one line-named TashT-that displays a partially penetrant aganglionic megacolon phenotype in a strong male-biased manner. Interestingly, this phenotype is highly reminiscent of human Hirschsprung's disease, a neurocristopathy with a still unexplained male sex bias. In contrast to the megacolon phenotype, colonic aganglionosis is almost fully penetrant in homozygous TashT animals. The sex bias in megacolon expressivity can be explained by the fact that the male ENS ends, on average, around a "tipping point" of minimal colonic ganglionosis while the female ENS ends, on average, just beyond it. Detailed analysis of embryonic intestines revealed that aganglionosis in homozygous TashT animals is due to slower migration of enteric NCC. The TashT insertional mutation is localized in a gene desert containing multiple highly conserved elements that exhibit repressive activity in reporter assays. RNAseq analyses and 3C assays revealed that the TashT insertion results, at least in part, in NCC-specific relief of repression of the uncharacterized gene Fam162b; an outcome independently confirmed via transient transgenesis. The transcriptional signature of enteric NCC from homozygous TashT embryos is also characterized by the deregulation of genes encoding members of the most important signaling pathways for ENS formation-Gdnf/Ret and Edn3/Ednrb-and, intriguingly, the downregulation of specific subsets of X-linked genes. In conclusion, this study not only allowed the identification of Fam162b coding and regulatory sequences as novel candidate loci for Hirschsprung's disease but also provides important new insights into its male sex bias.
authors.affiliation: Molecular Genetics of Development Laboratory, Department of Biological Sciences and BioMed Research Center, University of Quebec at Montreal (UQAM), Quebec, Canada.
authors.forename: Karl-F
authors.initials: KF
authors.lastname: Bergeron
authors.affiliation: Molecular Genetics of Development Laboratory, Department of Biological Sciences and BioMed Research Center, University of Quebec at Montreal (UQAM), Quebec, Canada.
authors.forename: Tatiana
authors.initials: T
authors.lastname: Cardinal
authors.affiliation: Molecular Genetics of Development Laboratory, Department of Biological Sciences and BioMed Research Center, University of Quebec at Montreal (UQAM), Quebec, Canada.
authors.forename: Aboubacrine M
authors.initials: AM
authors.lastname: Touré
authors.affiliation: Molecular Genetics of Development Laboratory, Department of Biological Sciences and BioMed Research Center, University of Quebec at Montreal (UQAM), Quebec, Canada.
authors.forename: Mélanie
authors.initials: M
authors.lastname: Béland
authors.affiliation: Veterinary Genetics Laboratory, Faculty of Veterinary Medicine, University of Montreal, Quebec, Canada.
authors.forename: Diana L
authors.initials: DL
authors.lastname: Raiwet
authors.affiliation: Veterinary Genetics Laboratory, Faculty of Veterinary Medicine, University of Montreal, Quebec, Canada.
authors.forename: David W
authors.initials: DW
authors.lastname: Silversides
authors.affiliation: Molecular Genetics of Development Laboratory, Department of Biological Sciences and BioMed Research Center, University of Quebec at Montreal (UQAM), Quebec, Canada.
authors.forename: Nicolas
authors.initials: N
authors.lastname: Pilon
mesh_terms: D000818:Animals; D033481:Chromosomes, Mammalian; D004195:Disease Models, Animal; D017615:Enteric Nervous System / Q000002:abnormalities; D006627:Hirschsprung Disease / Q000196:embryology / Q000235:genetics* / Q000473:pathology*; D008297:Male; D051379:Mice; D016254:Mutagenesis, Insertional; D009419:Nerve Tissue Proteins / Q000235:genetics / Q000378:metabolism; D009432:Neural Crest / Q000378:metabolism; D037941:Silencer Elements, Transcriptional; D059467:Transcriptome
chemical_list: C000603420:Fam162b protein, mouse; D009419:Nerve Tissue Proteins