Mutation of RET gene in Chinese patients with Hirschsprung’s disease

RET gene is a major risk factor for Hirschsprung's disease: a meta-analysis

PURPOSE

During the past two decades several genes have been identified that control morphogenesis and differentiation of the enteric neuron system (ENS). These genes, when mutated or deleted, interfere with ENS development. RET gene is the major gene causing Hirschsprung's disease (HD). Mutations in RET gene are responsible for 50% of familial HD cases and 15-20% of sporadic cases. The aim of this meta-analysis was to determine the incidence of RET gene mutations in patients with HD and to correlate RET mutations with the extent of aganglionosis.

METHODS

A systematic literature-based search for relevant cohorts was performed using the terms "Hirschsprung's disease AND RET Proto-oncogene", "Hirschsprung's disease AND genetic polymorphism" and "RET Gene". The relevant cohorts of HD were systematically searched for reported mutations in the RET gene (RET+). Data on mutation site, phenotype, and familial or sporadic cases were extracted. Combined odds ratio (OR) with 95% CI was calculated to estimate the strength of the different associations.

RESULTS

In total, 23 studies concerning RET with 1270 individuals affected with HD were included in this study. 228 (18%) of these HDs were RET+. Of these 228, 96 (42%) presented as rectosigmoid, 81 (36%) long segment, 18 (8%) as TCA, 16 (7%) as total intestinal aganglionosis and 17 (7%) individuals were RET+ but no extent of aganglionosis was not reported. In the rectosigmoid group, no significant association between phenotype and RET mutation could be shown (P = 0.006), whereas a clear association could be shown between long-segment disease, total colonic- and total intestinal aganglionosis and RET mutations (P = 0.0002). Mutations most often occurred in Exon 13 (24) and showed significant association with rectosigmoid disease (P = 0.004). No significance could be shown between RET+ and sporadic cases (P = 0.53), albeit a trend towards RET+ and Familial cases could be observed (P = 0.38).

CONCLUSIONS

The association with the RET gene and HD is well recognized. This study showed a clear association between RET+ mutations and the long-segment, total colonic- and total intestinal aganglionosis. Exon 13 appears to be a mutational "hot spot" in rectosigmoid disease.

Genetic basis of Hirschsprung's disease

Hirschsprung's disease (HSCR) is a developmental disorder characterized by the absence of ganglion cells in the lower digestive tract. Aganglionosis is attributed to a disorder of the enteric nervous system (ENS) whereby ganglion cells fail to innervate the lower gastrointestinal tract during embryonic development. HSCR is a complex disease that results from the interaction of several genes and manifests with low, sex-dependent penetrance and variability in the length of the aganglionic segment. The genetic complexity observed in HSCR can be conceptually understood in light of the molecular and cellular events that take place during the ENS development. DNA alterations in any of the genes involved in the ENS development may interfere with the colonization process, and represent a primary etiology for HSCR. This review will focus on the genes known to be involved in HSCR pathology, how they interact, and on how technology advances are being employed to uncover the pathological processes underlying this disease.

Mutation of RET oncogene and endo-thelin B receptor gene in Hirschpru-ng's disease

AIM: To clarify the relationship between the mutation of RET and EDNRB genes and Chinese patients with Hirschspr-ung's disease (HD), and to investigate whether the two genes mutation concurred in the disease.

METHODS: Patients with HD were divided into RET/EDNRB group (group A, 56 cases) and ENDRB group (group B, 40 cases) at random. Healthy children were use as controls (group C, 56 and 40 cases). Genomic DNA was obtained from peripheral blood, then the exons 6, 13, 15 and 17 of RET gene and the exons 4, 5 and 6 of EDNRB gene were analyzed for gene mutation. The mutation products were automatically sequenced.

RESULTS: In group A, two heterozygous mutations at exons 17 and 13 were discovered in 2 sporadic HD patients. Direct DNA sequence analysis identified gene polymorphisms, which showed CTG→CTT, and Leu769→Leu. The sporadic mutation rate was 4% (2/48). Two heterozygous mutations were discovered in 2 familial HD patients at exon 15. DNA sequence analysis displayed a missense mutation Lys889→Thr in one patient and two silent mutation at codons V906 and S909 in another (GTGAAGAGGAGCCA→GTTAAGAGGAGTCA). The familial mutation rate was 25% (2/8). One heterozygous mutation of EDNRB gene at exon 5 in a sporadic short segmental patient failed to sequence. In group B, one heterozygous mutation was discovered in a sporadic short segmental patient. DNA sequence showed a G to A transversion at nucleotide 831, which resulted in a silent mutation Leu 277→Leu. The mutation rate was 2.7%(1/37). No mutation was detected in three familial HD patients. In group C, RET and EDNRB genes were identified no mutation. The difference of the RET gene mutation between the familial and sporadic patients by statistical analysis was x² = 4.95 (P < 0.05), odds ratio (OR) = 8; 95%CI = 1.28-49.87.

CONCLUSION: The mutation of RET and EDNRB genes reliably has correlated with the pathogenesis of HD. The RET gene mutation rate in familial HD patients is 25% and majority of sporadic cases have mutation in EDNRB gene. No HD patient has the two genes mutation at the same time. The risk of familial patients to get HD is 8 times higher than that of sporadic patients, and the confidence interval is 95%.