The International Complex Trait Consortium

Evaluation of Candidate Modifiers in the Sox10Dom Mouse Model of Hirschsprung Disease

Ron Chandler, Ashley Cantrell, Sarah Owens, Michelle Southard-Smith

Vanderbilt University, Division of Genetic Medicine, Nashville, TN 37232-6304 USA

ABSTRACT
 
The Dominant megacolon mouse (Sox10Dom) is a model of aganglionic megacolon that arises from mutation of the neural crest transcription factor Sox10. Alterations in Sox10 cause deficiencies of NC derivatives including melanoblasts and enteric neurons that cause hypopigmentation (spotting) and absence of enteric ganglia in the distal gastrointestinal tract respectively. Sox10Dom mutants exhibit variability in survival due to megacolon when maintained on a mixed genetic background (C57BL/6J x C3FeLe.B6-a F1). We have used whole-mount acetylcholinesterase staining to document that differences in survival correspond to variation in the degree of intestinal aganglionosis. Our analysis of Sox10Dom congenic lines on the C57BL/6J and C3HeB/FeJ backgrounds show distinct differences in survival due to megacolon and aganglionosis indicating that genetic background influences the severity of NC phenotypes in this mouse model of Hirschsprung (HSCR) disease.

Mutations in SOX10 have also been described in patients with hypopigmentation and deficiencies of enteric neurons classified as Waardenburg-Shah-Hirschsprung (WS-HSCR) disease. Interestingly variation of aganglionosis penetrance and severity has been described between human family member that carry identical mutations in the SOX10 locus (Pingault et al., 1998; Southard-Smith et al., 1999). This variation in human families and in the Sox10Dom mouse model suggests modifier genes influence development of neural crest derivatives in both man and mouse.

We are using extended pedigrees of Sox10Dom mice on a B6C3F F1 genetic background to evaluate potential interactions between Sox10 and candidate modifier loci for their impact on aganglionosis. Candidate modifier loci have been selected based on either their known involvement in HSCR or their role in neural crest development. Simple Tandem Repeat (STR) markers closely flanking each candidate locus have been generated from mouse genomic sequence and tested for polymorphism between the B6 and C3F strains. Our candidate locus markers are being applied in genotyping the extreme phenotypes from our B6C3F.Sox10Dom pedigree. Our initial cohort of animals from this pedigree have been stratified based on whether they exhibit little or no megacolon and thus survive to old age or die secondary to severe megacolon in the early postnatal period. Genotype information from our candidate STR markers is being used to evaluate associations between alleles at each candidate locus and severity of megacolon. We will present our initial findings of gene interactions that modulate the severity of aganglionosis between Sox10, other NC transcription factors and signaling pathways that are relevant to HSCR. These analyses are designed to identify the genetic interactions that contribute to variation in neural crest phenotypes.

[This work has been supported by a Research Scholar Award from the Howard Hughes Medical Institute Research Resources Program for Medical Schools (HHMI/76296-525802), a Foundation for Digestive Health and Nutrition Research Scholar Award, and by the National Institutes of Diabetes, Digestive and Kidney Diseases (1 RO1 DK60047-01)]