The molecular characterisation of the annexin II gene in pre-eclampsia

[摘要] ENGLISH ABSTRACT: The hypertensive conditions of pregnancy (including pre-eclampsia (PE)) is the leading cause of primary obstetric death in South Africa and affects at least five percent of pregnancies in the Western Cape province. Reduced levels of placental protein 13 (PP13) early in pregnancy are associated with a higher incidence of PE in later gestation. PP13 and annexin II have been co-localised to the brush border membrane of syncytiotrophoblasts, and form a complex that is transported to the maternal circulation. It is speculated that genetic variation in the gene encoding annexin II (ANXA2) could underlie the reduced PP13 levels.The aim of this study was to screen the ANXA2 gene, including the proximal promoter region, in two South African population groups, (Mixed Ancestry and Black) from the Western Cape, to identify whether variants in the ANXA2 gene confer susceptibility to PE. The study cohort comprised of 120 pre-eclamptic maternal, 94 pre-eclamptic fetal and 54 healthy control individuals. Genomic DNA of patient and control individuals was extracted for PCR amplification of ANXA2 and Multiphor SSCP/HD analysis was performed for mutation detection. The conformational variants identified were subjected to automated DNA sequencing and subsequently to RFLP analysis, to confirm the genotypes in the remainder of the cohort. Nine previously identified variants (c.-31 T>C, c.292 G>T; p.Val98Leu, c.975 C>T;p.Gly325Gly, c.-12+75 C>A, c.-11-43 G>A, c.-11-13 A>T, c.48+67 C>T, c.449-17 G>A, c.683-56 G>A) and 16 novel variants (c.-442 C>G, c.-191 G>C, c.-189_-188insGCCGG, c.-135 C>G, c.-92 A>T, c.222 C>T; p.Ala74Ala, c.600 C>T; p.Asp110Asp, c.934 G>A; p.Gly312Ser, c.244-42 G>C, c.244-76 C>G, c.528+38 C>T, c.589-5 C>T, c.682+49 C>T, c.961-30 A>G, c.961-24 C>G, c.*1057 A>G) were identified upon screening the ANXA2 gene. Statistical analysis identified significant association at five loci: SNP c.-92 A>T located within the ANXA2 5‟UTR, exonic SNP c.222 C>T; p.Ala74Ala and three intronic SNPs c.244-76 C>G, c.449-17 G>A and c.589-5 C>T. Three of the five variants (c.-92 A>T, c.244-76 C>G, c.589-5 C>T) were significantly associated with PE (P<0.05) and could contribute to PE susceptibility in these two SA ivpopulations, whereas the other two variants (c.222 C>T; p.Ala74Ala, c.449-17 G>A) revealed a possible protective effect, suggesting a reduced risk of developing PE. In silico analysis predicted the disruption and creation of several putative transcription factor binding sites by three SNPs in the ANXA2 gene, which could subsequently affect ANXA2 functioning.This study provides evidence for genetic variation in the ANXA2 gene, which warrants functional experimental validation in an attempt to investigate the function of these SNPs in molecular, cellular and physiological processes underlying PE. Identifying an association between variants in the ANXA2 gene and PE could contribute to the development of an additional early biomarker. The early identification of PE would promote the South African health system by providing the appropriate health care support and monitoring of high risk pregnancies, which could ultimately result in improved pregnancy outcome.

[发布机构] Stellenbosch University