Familial form of Hirschsprung disease: Nucleotide sequence studies reveal point mutations in the RET proto-oncogene in two of six families but not inother candidate genes

Hirschsprung disease (HSCR; McKusick 142623) or aganglionic megacolon is a frequent (1 in 5,000 live births) heritable disorder of the enteric nervous system. By haplotyping with a variety of microsatellite markers, by amplif ying all 20 exons of the RET proto-oncogene and by applying a direct DNA se quencing protocol, we have analyzed the DNA from HSCR patients in 6 differe nt families. In one family with a joint occurrence of HSCR and FMTC (follic ular medullary thyroid carcinoma), we have identified a mutation in codon 6 09 in one out of 6 cysteine residues encoded in exon 10 of the RET gene. Th is C609R point mutation has not previously been reported to cause HSCR. In 2 of the HSCR patients described here from different families, we have foun d a mutation in exon 2 (R77C) and a silent mutation in exon 3 (Y204Y), resp ectively, in the extracellular part of the RET proto-oncogene. In introns 2 and 17 of the RET proto-oncogene in 2 families, we have detected single nu cleotide exchanges that are probably polymorphisms with unknown, if any, re lations to HSCR. The DNA sequences of 5 further genes (GDNF, GDNFR alpha, E DN3, EDNRB, and NTN), that may contribute to the development of HSCR, have not shown mutations in the patients analyzed so far. In 2 of the reported f amilies with several affected children and one grandchild, sequence analyse s revealed no mutations in the coding regions of any of the candidate genes analyzed. (C) 2000 Wiley-Liss, Inc.