Association of group-specific component exon 11 polymorphisms with bronchial asthma in children and adolescents

Several studies have investigated the association of Group-specific Component (GC) gene, also known as vitamin D-binding protein (VDBP), and various respiratory disorder susceptibility with conflicting results. In this sense, we aimed to investigate whether rs7041 and rs4588 variants confer susceptibility to bronchial asthma in a sample of an Egyptian population and to elucidate by in silico analysis the structural and functional impact of these variants. Group-specific Component polymorphisms rs7041 and rs4588 were genotyped in 192 Egyptian children and adolescents (96 with asthma and 96 healthy controls) by TaqMan single nucleotide polymorphism genotyping assay. The rs7041 GG genotype showed a significantly elevated frequency among patients under codominant, dominant, recessive and allelic models where the patient group had greater carriage rate of G allele [OR 2.15, CI 95% (1.32-3.50; P = 0.002)], while rs4588 CA and AA genotypes were found to be protective genotypes with controls showing a greater carriage rate of A allele [OR 0.52, CI 95% (0.30 - 0.90; P = 0.02)]. Three haplotype allele combinations were identified with frequencies of GC (44.3%), TC (31.3%) and TA (24.5%) in the total study population. GC haplotype was shown to be more frequent in controls, while TC and TA haplotypes were more predominant in the patient group. Only rs7041 variant showed a significant association with family history and pubertal status. In conclusion, both study GC variants could be implicated in childhood bronchial asthma pathogenesis; rs7041 GG genotype and G allele increased asthma risk while rs4588 AA genotype and A allele conferred protection in the study population.