Molecular-genetic analysis of Hirschsprung's disease in South Africa

[摘要] ENGLISH ABSTRACT:Hirschsprung's disease, or aganglionic megacolon, is a common cause of intestinalobstruction in neonates and is associated with the congenital absence of intrinsicganglion cells in the myenteric and submucosal plexuses of the gastrointestinal tract.The affected area is usually restricted to the distal part of the colon (short segmentdisease), but total colonic or intestinal involvement occurs in some patients (longsegment disease).DNA analysis was performed on samples from 53 unrelated sporadic HSCR patientsto search for mutations in RET proto-oncogene, endothelin-B receptor (EDNRB) andendothelin-3 (EDN3) genes. The patients were from different ethnic groups in SouthAfrica, including 29 coloured, 14 white (Caucasian) and 9 black individuals. Theorigin of 1 patient was unknown. PCR HEX-SSCP analysis of the RET protooncogenerevealed one previously described (P973L) and five novel mutations(V202M, E480K, IVS10-2A1G, D771N, IVS19-9Crr), likely to cause or contribute tothe HSCR phenotype. Nine polymorphisms were also identified in the RET protooncogene,of which four were novel (IVS6+56deIG, IVS13-29Crr, IVS16-38deIG,X1159) and five previously described (A45, A432, L769, S904, R982). All the mobilityshifts detected in the EDNRB gene represented polymorph isms (A60T, S184, 1187,V234, L277, IVS3-6Crr, IVS4+3A1G). No sequence variants were identified in theEDN3 gene. The majority of mutations in the RET proto-oncogene (28.6%) wereidentified in coloured patients while no mutations were identified in black patients. Amutation in RET was identified in two of 14 patients (14%) presenting with HSCR andDown's syndrome compared to 6 mutations identified in 9 of 39 patients (23%) with only HSCR. The fact that Down's syndrome patients have a high chance ofdeveloping HSCR, implies the involvement of modifier gene(s) in a HSCR/Oown'ssyndrome phenotype.This study demonstrated that, within the South African HSCR patient population, theRET proto-oncogene is the major susceptibility gene, whereas EDNRB and EDN3may contribute only to a minority of cases. In 81% of patients no disease-causingmutation could be identified, which is in keeping with the heterogeneous nature ofHSCR. The identification of mutations in HSCR patients would in future lead toimproved and accurate counselling of South African HSCR patients and theirfamilies.

[发布机构] Stellenbosch University