Mutational analysis of RET/GDNF/NTN genes in children with total colonic aganglionosis with small bowel involvement

Hirschsprung disease (HSCR) is characterized by the absence of intramural g anglion cells in the distal gut, resulting in bowel obstruction shortly aft er birth. Aganglionosis usually affects the distal colon, but may also exte nsively involve the entire colon and, rarefy, the more proximal bowel. Rece ntly, germline mutations of RET, GDNF, and NTN genes have been reported in HSCR, Here we describe the results of mutational analysis of these genes in 15 Japanese child patients with total colonic aganglionosis with small bow el involvement, DNA sequences of all the RET/GDNF/NTN coding regions were d etermined by the direct dyedeoxy terminator cycle method, Eight different R ET mutations were identified in exons 1, 7, 10, 12, 15, and 17 in 10 of the 15 patients, Of these eight mutations, five were found in the tyrosine kin ase domain. No GDNF or NTN mutation was found. Compared with typical HSCR, this patient group appeared to exhibit a higher percentage of RET mutations and accumulation of mutations in the tyrosine kinase domain, A homozygous (or hemizygous) RET mutation was found in a male baby with total intestinal aganglionosis, while the heterozygosity of the same mutation resulted in a less severe type of aganglionosis, In familial cases, all heterozygous for the same mutation, aganglionosis was more severe in male than in female si blings. These results also urge us to examine if the RET germline mutation may cause critical alteration of the GDNF/NTN-Ret signal transduction more severely in homo(hemi)-zygosity and in male fetuses during organogenesis, ( C) 2000 Wiley-Liss, Inc.