Role of the HLA-G regulatory region polymorphisms in idiopathic recurrent spontaneous abortions (RSA)

Problem: HLA-G polymorphisms have a functional impact on its expression and may cause a breakdown of maternal tolerance towards the semi-allogenic fetus, resulting in recurrent spontaneous abortions (RSA). This study reports on the association of HLA-G regulatory region polymorphisms with idiopathic RSA. Methods: Seventy-five couples with =2 spontaneous abortions were recruited in comparison to 75 healthy couples who had normal pregnancies. About 5 mL of blood samples were collected from all the participants, and DNA was extracted. Screening of HLA-G 5'-upstream regulatory region (5'-URR) was done by direct sequencing in 50 each of RSA and healthy couples, respectively. The 14 bp deletion/insertion polymorphism in the 3'-untranslated region (3'-UTR) was genotyped in 75 each of RSA and healthy couples, respectively, by PCR amplification of HLA-G exon 8. MedCalc, Graph Pad Prism, Haploview, PLINK, and multifactor dimensionality reduction were used to analyze the data. Results: HLA-G screening revealed the presence of-762C/T,-725C/G,-716T/G, -689A/G, -486C/A, and-477C/G single nucleotide polymorphisms (SNPs) in the 5'-URR. At positions -762 and -477, the frequency of CC homozygotes was significantly higher in controls compared to the patients. The 14 bp deletion/insertion polymorphism in the 3'-UTR showed an association with RSA with the heterozygous genotype being significantly higher in RSA compared to controls.Conclusions: The study indicates a protective role of the CC genotypes of the two HLA-G 5'-URR polymorphisms,-762C/T and-477C/G, against RSA. It also suggests that women with the 14 bp deletion/insertion genotype have a significantly higher risk of RSA.