POINT MUTATIONS AFFECTING THE TYROSINE KINASE DOMAIN OF THE RET PROTOONCOGENE IN HIRSCHPRUNGS DISEASE

HIRSCHSPRUNG'S disease is a genetic disorder of neural crest developme nt affecting 1 in 5,000 births. It is characterized by the absence of intramural ganglion cells in the hindgut, which often results in parti al to complete intestinal obstruction during the first years of life. An autosomal dominant gene causing this disease was recently mapped to chromosome 10q11.2 (refs 1, 2), using an interstitial deletion of thi s region isolated in a cell hybrid3,4. It was subsequently localized t o a 250-kilobase interval which contains the RET proto-oncogene5. Usin g flanking intronic sequences as primers6 to amplify 12 of the 20 exon s of RET from genomic DNA of 27 Hirschsprung's disease patients, we ha ve now identified four mutations (one frameshift and three missense) t hat totally disrupt or partially change the structure of the tyrosine kinase domain of the RET protein (Ret). Mutations in the extracellular cysteine-rich domain of Ret have been identified previously7,8 in pat ients with multiple endocrine neoplasia type 2A, and a targeted mutati on in the tyrosine kinase domain of the same gene produces intestinal aganglionosis and kidney agenesis in homozygous transgenic mice9. Our results support the hypothesis that RET, in addition to its potential role in tumorigenesis, plays a critical role in the embryogenesis of t he mammalian enteric nervous system.