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.

Thesis (MSc (Genetics))--University of Stellenbosch, 2009. / Pre-eclampsia is one of the most common hypertensive disorders of pregnancy in South Africa. Presently, the only cure for pre-eclampsia is delivery, which brings with it, additional complications. As an alternative, clinical management of this disorder relies on timely diagnosis. The predictive biomarker, Placental Protein 13 (PP13), is currently used for the early diagnosis of pre-eclampsia, in an ELISA-based diagnostic kit, developed by Diagnostic Technologies Limited (DTL)1. A decrease in serum PP13 levels has been reported during the first trimester of pregnancy in women who later develop pre-eclampsia. The function of PP13 has not been fully elucidated and it is also not known whether the reduction in PP13 levels is a cause or an effect of the disease. The use of PP13 as a predictive biomarker for pre-eclampsia therefore warrants a comprehensive study of this peptide and the encoding gene, LGALS13. The aim of this study was firstly to characterise LGALS13 using a range of in silico tools. PP13 was found to be most homologous to the predicted protein product of a neighbouring “putative” gene, LOC148003. A gene conversion event between these two genes most likely underlies the so-called “hotspot mutation” in LGALS13. Data also demonstrates that the DelT mutation disrupts functionally and structurally important features of the gene and peptide sequences. Through the analysis of the putative promoter region of LGALS13, the presence of a Stimulatory protein-1 (Sp1) binding sequence element was predicted, which has implications for regulation of LGALS13. Secondly, the study aimed to establish a study cohort for the investigation of the effect that the LGALS13 genotype has on the expression of its mRNA and protein products. Serum, plasma and whole blood samples were collected and prepared from 316 pregnant women. Placental tissue samples were obtained from a selected group of these subjects for RNA extraction. Once the sampling on the two remaining targeted deliveries has occurred, the collection of samples will be batched and sent to DTL in Israel, for PP13 measurement. DNA was extracted from the whole blood samples obtained, and all study participants were genotyped for seven sequence variants within the LGALS13 gene using (i) Multiphor Single Stranded Conformational Polymorphism and Heteroduplex (SSCP/HD) analysis, (ii) restriction enzyme analysis and (iii) DNA sequencing. The genotype data sets will be compared with PP13 levels when they become available, and also with clinical parameters, once the deliveries have all occurred and the database is complete. This study demonstrated the power of an in silico approach to direct the focus of future experimental work. The newly established study cohort will be used for prospective studies aiming at a better understanding of the role which LGALS13 and PP13 play in the early prediction of preeclampsia.