Frequent 4-bp deletion in exon 9 of the SMAD4/MADH4 gene in familial juvenile polyposis patients

Abstract

Familial juvenile polyposis (FJP) is a hamartomatous polyposis syndrome characterized by the appearance of juvenile polyps in the gastrointestinal tract. Patients with this syndrome are at an increased risk for cancer of the colon, stomach, and pancreas. Recently, germline mutations in the SMAD4/DPC4 gene (official symbol MADH4) have been found in the majority of patients suffering from FJP. We have examined 11 unrelated patients with FJP for MADH4 germline mutations by direct sequencing of genomic DNA encompassing all 11 exons of the gene. Besides a novel mutation (959-960delAC at codon 277, exon 6) in one patient, we observed a 4-bp deletion (1372-1375delACAG) in exon 9 in two unrelated patients. Examination with microsatellite markers flanking MADH4 supports an independent origin of the mutation in these two families. The same 4-bp deletion in exon 9 has previously been described in three out of nine patients examined for MADH4 mutations. Our results combined with these previous data demonstrate that a unique 4-bp deletion in exon 9 of MADH4 accounts for about 25% of all FJP cases and that other MADH4 mutations occur in an additional 15% of patients. Genes Chromosomes Cancer 25:403-406, 1999.