RET genotypes comprising specific haplotypes of polymorphic variants predispose to isolated Hirschsprung disease
- Salud Borregoa,
- Agustín Ruiza,
- María Eugenia Saeza,
- Oliver Gimmb,c,
- Xin Gaoc,
- Manuel López-Alonsod,
- Antonio Hernándezd,
- Fred A Wrightc,
- Guillermo Antiñoloa,
- Charis Engb,c,e
- aUnidad de Genética Médica y Diagnóstico Prenatal, Hospital Universitario “Virgen del Rocío”, Avda Manuel Suirot s/n, 41013 Sevilla, Spain, bClinical Cancer Genetics Program, Comprehensive Cancer Center and Division of Human Genetics, Department of Internal Medicine, Ohio State University, Columbus, OH, USA, cHuman Cancer Genetics Program, Ohio State University Comprehensive Cancer Center, 420 W 12th Avenue, Room 690 MRF, Columbus, OH 43210, USA, dCirugía Infantil, Hospital Universitario “Virgen del Rocío”, Sevilla, Spain, eCancer Research Campaign Human Cancer Genetics Research Group, University of Cambridge, Cambridge, UK
- Dr Borrego,gantinolog{at}sego.es
- Revised 11 April 2000
- Accepted 17 April 2000
Abstract
BACKGROUND Hirschsprung disease (HSCR), which may be sporadic or familial, occurs in 1:5000 live births and presents with functional intestinal obstruction secondary to aganglionosis of the hindgut. Germline mutations of theRET proto-oncogene are believed to account for up to 50% of familial cases and up to 30% of isolated cases in most series. However, these series are highly selected for the most obvious and severe cases and large familial aggregations. Population based studies indicate that germline RETmutations account for no more than 3% of isolated HSCR cases. Recently, we and others have noted that specific polymorphic sequence variants, notably A45A (exon 2), are over-represented in isolated HSCR.
PURPOSE In order to determine if it is the variant per se, a combination thereof, or another locus in linkage disequilibrium which predisposes to HSCR, we looked for association of RET haplotype(s) and disease in HSCR cases compared to region matched controls.
METHODS Seven loci acrossRET were typed and haplotypes formed for HSCR cases, their unaffected parents, and region matched controls. Haplotype and genotype frequencies and distributions were compared among these groups using the transmission disequilibrium test and standard case-control statistic.
RESULTS Twelve unique haplotypes, labelled A-L, were obtained. The distributions of haplotypes between cases and controls (χ11 2 =81.4, p<<0.0001) and between cases and non-transmitted parental haplotypes were significantly different (χ2 11=53.1, p<0.0001). Genotypes comprising pairs of haplotypes were formed for cases and controls. There were 38 different genotypes among cases and controls combined. Inspection of the genotypes in these two groups showed that the genotype distribution between cases and controls was distinct (χ37 2=93.8, p<<0.0001). For example, BB, BC, BD, and CD, all of which contain at least one allele with the polymorphic A45A, are prominently represented among HSCR cases, together accounting for >35% of the case genotypes, yet these four genotypes were not represented among the population matched normal controls. Conversely, AA, AG, DD, GG, and GJ, none of which contains A45A, are commonly represented in the controls, together accounting for 43% of the control genotypes, and yet they are never seen among the HSCR cases.
CONCLUSIONS Our data suggest that genotypes comprising specific pairs of REThaplotypes are associated with predisposition to HSCR either in a simple autosomal recessive manner or in an additive, dose dependent fashion.
