An intronic nucleotide variant of the RET proto-oncogene causes Hirschsprung disease by interfering with RNA splicing

Abstract

The RET proto-oncogene is expressed during embryogenesis in neural-crest derived cells and is involved in different human neurocristopathies such as Multiple Endocrine Neoplasia type 2 (MEN2) syndromes and Hirschsprung disease (HSCR or congenital megacolon). While MEN2 are inherited cancer syndromes due to constitutive activation of the Ret receptor, HSCR pathogenesis is caused by loss of function of the RET product. We have analyzed the RET proto-oncogene in a family showing a peculiar recurrence of neurocristopathies: a mother with ganglioneuroblastoma and a daughter with long segment aganglionosis. In the HSCR patient no mutation in the RET gene was detected, except for a C>T substitution in intron 12. Functional evidences that such an intronic mutation introduces a novel splice donor site which is recognized and actively used during RNA splicing are provided. Moreover, a polymorphic RET variant, found overrepresented in sporadic medullary carcinomas, was detected in the mother. The association of HSCR with ganglioneuroblastoma in close relatives could be more than coincidental and further investigation into genes driving neural crest differentiation will help to explain the occurrence of different neurocristopathies within the same pedigree.