Molecular genetic analysis of abruptio placentae
Thesis (MSc (Genetics))--University of Stellenbosch, 2009.
Abruptio placentae is the premature separation of the normally implanted placenta from the uterine wall, resulting in haemorrhage before delivery of the fetus. This has serious maternal and neonatal implications, and is one of the leading causes of perinatal and maternal mortality and morbidity in South Africa. Placental vasculopathies, such as abruptio placentae, are believed to result from faults occurring in early placental development. Placental protein 13 (PP13) is a member of the pregnancy-related protein family, and is believed to function in a number of important physiological processes such as trophoblast invasion, placentation and implantation. The aim of this study was to investigate whether DNA sequence variants in the LGALS13 gene (encoding PP13), underlie and/or confer susceptibility to abruptio placentae. The gene was screened and genotyped in a cohort of patients whose pregnancies were complicated by abruptio placentae, as well as an ethnically matched control cohort. Statistical and in silico analyses were performed in order to identify potential susceptibility factors in this South African cohort and to predict whether the identified variants may impact on gene expression or the structure and function of PP13. In addition, the luciferase reporter gene assay was employed to investigate the functionality of the -98A/C variant identified in the 5’ untranslated region of the LGALS13 gene. Statistically significant differences were observed between patient and control groups at the following loci in the Coloured population: -98A/C, IVS2 -36G/A, IVS2 -22A/G and the hotspot variant in exon 3 (p<0.05). These variants could represent a susceptibility profile of this population or alternatively have implications in the pathogenesis of abruptio placentae. The deletion of a single thymine in exon 3 was shown to result in truncation of PP13 and subsequent disruption of a number of cysteine residues and putative phosphorylation sites, which could impact on dimerization and ultimately, the function of the protein. The reporter gene assay revealed a significant reduction (p=0.004) in luciferase activity by the -98 C allele. iii In silico analysis suggests that this reduction could be due the disruption of a NF1 or GR transcription factor binding site. This study provides evidence that variants in the LGALS13 gene may underlie and/or confer susceptibility to abruptio placentae by impacting on gene regulation or resulting in the expression of an aberrant form of the PP13 which could affect functionality and thereby result in the disruption of normal implantation and placentation.