Objective: To investigate whether the polymorphisms of insulin-like growth factor-1 (IGF-1) gene and its regulatory regions are associated with extreme high myopia.
Methods: A case-control analysis of 302 subjects with extreme high myopia and 401 controls was undertaken. Genomic DNA was obtained from peripheral blood. Seven tag single nucleotide polymorphisms (tSNP) across the IGF-1 gene region were selected to capture the majority of genetic variation. All tSNP were genotyped using the MassArray platform and MALDI-TOF analysis. Genotypic distribution was tested for Hardy-Weinberg equilibrium. Statistical analyses were performed using the SPSS (version 13.0: SPSS Science, Chicago, IL) software. The genotype and allele frequencies were evaluated using the χ(2) tests and performed by Bonferroni corrections for multiple comparisons. The significance of the differences in the estimated haplotype frequencies between the myopia and control groups was examined on Haploview 4.2 using χ(2) tests, and haplotypes were corrected by using permutation test after running 50 000 times.
Results: Among seven different IGF-1 tSNP tested, the allele frequencies of four tSNP-rs5742629(A/G), rs12423791(G/C), rs35766 (G/A) and rs1457601(T/A) in the myopia and the control groups were A(56.5%, 62.3%)/G(43.5%, 27.7%), G(70.4%, 77.1%)/C(29.6%, 22.9%), G(33.9%, 28.8%)/A(66.1%, 71.2%), T(72.5%, 77.3%)/A(27.5%, 22.7%), respectively. And they showed significant differences (χ(2) = 4.968, 8.059, 4.250, 4.245, P < 0.05) between the two groups. However, only rs12423791 remained significance after Bonferroni correction. The haplotype GC of rs5742629-rs12423791 was associated with extreme high myopia (P = 0.033) after 50 000 permutations for multiple comparisons as well.
Conclusions: The polymorphism of rs12423791 in IGF-1 may be associated with extreme high myopia in the Chinese population.