A common haplotype at the 5' end of the RET proto-oncogene, overrepresented in Hirschsprung patients, is associated with reduced gene expression

Hum Mutat. 2005 Feb;25(2):189-95. doi: 10.1002/humu.20135.

Abstract

Hirschsprung disease (HSCR) is a complex genetic defect of intestinal innervation mainly ascribed to loss of function mutations of the RET gene. Although RETcoding mutations account for only 15% of HSCR sporadic cases, several linkage and association studies still indicate RET as a major HSCR gene, suggesting the existence of noncoding RET variants or common polymorphisms which can act in HSCR pathogenesis. We previously described a predisposing RET haplotype (A-C-A) composed of alleles at three SNPs (-1 bp and -5 bp from the RET transcription start site, NT_033985.6:g.975824G>A and NT_033985.6:g.975820C>A, respectively, and silent polymorphism c.135G>A), which was present in 62% of chromosomes from HSCR patients but only in 22% of control chromosomes. Here we address the question of how this 5' ACA haplotype may functionally act as a predisposing factor in HSCR pathogenesis by performing functional analysis of the same three SNPs. We demonstrate that neither the two promoter variants nor the exon 2 SNP interfere with reporter gene transcription or RET mRNA splicing, respectively. However, real-time RT-PCR, performed in RNA obtained from lymphoblasts of selected individuals, has shown that homozygosity for the whole ACA haplotype is associated with reduced RET gene expression. We propose that a yet unidentified variant in linkage disequilibrium with the ACA haplotype, rather than the single characterizing SNPs, acts as a HSCR susceptibility allele by affecting the normal amount of RET receptor on the cell surface.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • 5' Flanking Region
  • Cells, Cultured
  • Exons
  • Female
  • Gene Expression
  • Genetic Predisposition to Disease
  • Haplotypes
  • Hirschsprung Disease / genetics*
  • Hirschsprung Disease / metabolism
  • Homozygote
  • Humans
  • Male
  • Polymorphism, Single Nucleotide*
  • Promoter Regions, Genetic
  • Proto-Oncogene Proteins c-ret / genetics*
  • Proto-Oncogene Proteins c-ret / metabolism
  • RNA Splicing
  • RNA, Messenger / metabolism

Substances

  • RNA, Messenger
  • Proto-Oncogene Proteins c-ret
  • RET protein, human

Associated data

  • OMIM/142623
  • OMIM/164761