AB087. Synergistic genetic effects of RET and NRG1 susceptibility variants in Hirschsprung disease

Abstract
Background
Hirschsprung disease (HSCR) is a complex genetic disorder, which characterized by absence of ganglion cells along variable lengths of the intestines in neonates, with the RET and NRG1 are reported as the most common susceptible genes for HSCR development. Here, we investigated three common genetic markers: RET rs2506030 and NRG1 rs7835688 and rs16879552, to determine their potential interactions to the susceptibility of HSCR in Indonesian population.

Methods
We ascertained 60 HSCR subjects and 118 non-HSCR controls. Three genetic markers of the RET and NRG1 were examined using TaqMan assay. Case-control association tests between three genetic markers and HSCR were performed using the χ2 (chi square) statistic and 2×2 contingency tables. We analyzed the family based association in duos and trios using the transmission disequilibrium test (TDT) for the variants using PLINK.

Results
There was association between NRG1 rs7835688 (4.3×10−3) variant and HSCR, but not RET rs2506030 (P=0.042) and NRG1 rs16879552 (P=0.097). TDT of 33 HSCR families demonstrates no genetic effect either at RET rs2506030 (P=0.034) or NRG1 rs7835688 (P=0.18) and rs16879552 (P=0.28). Two locus analyses of polymorphisms demonstrated that RET rs2506030 (GG), in combination with NRG1 rs7835688 (CC) or rs16879552 (CC), were associated with the increased disease risks of HSCR (OR =6.22, P=0.028 and OR =3.34, P=6.0×10−4, respectively) compared with a single variant of either RET or NRG1.

Conclusions
Our study shows that RET and NRG1 polymorphisms are common genetic risk factors for Indonesian HSCR. These results also imply that synergistic effects of RET and NRG1 is necessary for normal ganglionosis.

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