Molecular genetic analysis of the neurokinin B (TAC3) and neurokinin B receptor (TAC3) genes as candidates for pre-eclampsia

Carelse Tofa, Kashefa (2004-12)

Thesis (MSc)--Stellenbosch University, 2004.

Thesis

ENGLISH ABSTRACT: Hypertensive conditions of pregnancy, such as pre-eclampsia, are the principal direct cause of maternal morbidity and mortality and affect up to 10% of first pregnancies worldwide. The placenta is vital in the pathogenesis of pre-eclampsia since the condition only occurs in the presence of placental tissue and the only cure is delivery of the placenta and the fetus. It has been hypothesised that the placenta may be the source of a circulating factor(s), which transports freely in the maternal system, resulting in the multi-systemic and immunological responses that are characteristic of pre-eclampsia. Among the potential "circulating" candidates currently being investigated worldwide, is the tachykinin member, neurokinin B (NKB). The aim of this project was to use a novel approach and investigate the role of Neurokinin B in pre-eclampsia on a genetic level. This would be achieved by bioinformatie characterisation of the neurokinin B (TAC3) and neurokinin B receptor (TACR3) genes. Samples from thirty pre-eclampsia patients (of whom 10 also had abruptio placentae) and twenty control individuals were used for mutation detection analysis involving Multiphor gel electrophoresis and automated sequencing. Three sequence variants were identified in the TAC3 gene and include: (i) 5' UTR variant (-25 c-t); (ii) intronic variant IVS3-53 (t-g) and (iii) 3' UTR variant exon 7 (479, t-c). Only the -25 c-t variant had been reported before (SNP database). A further two variants were identified in the TACR3 gene: (i) exon 3 variant (nt 857, a-t) and (ii) 3' UTR variant, amplicon 5b (nt 1471, t-c), of which the latter had previously been reported in the SNP database. In the analysis of allele and genotype frequencies, only variant homozygosity for TAC3 -25 c-t could be associated with increased risk of pre-eclampsia (RR 3.33, p=0.03). Follow-up work will include extended genotyping in further stratified and larger patient cohorts and transfection studies to assess splicing potential and functional consequences of the mutant alleles. These data represent the first documented mutation screen of the TAC3 and TACR3 genes and report novel variants in patients with pre-eclampsia. This study contributes to the knowledge of neurokinin B as a circulatory molecule and confirms the heterogeneity of pre-eclampsia.

AFRIKAANSE OPSOMMING: Die belangrikste direkte oorsaak van moedersterftes is hipertensiewe toestande in swangerskap, insluitende pre-eklampsie. Hierdie toestande kompliseer wêreldwyd 10% van alle swangerskappe. Die plasenta is kardinaal in die ontwikkeling van die siekte aangesien dit slegs voorkom terwyl die plasenta in-situ is en die simptome opklaar na verlossing van die plasenta. 'n Moontlike hipotese is dat die plasenta 'n sirkulerende agens afskei wat in die moederlike sisteem beland en die uiteenlopende multi-sistemiese simptome en tekens van die siekte veroorsaak, asook aktivering van die immuunsisteem. Een van die moontlike kandidate wat tans wêreldwyd ondersoek word as moontlike sirkulerende agens, is Neurokinien B (NKB), 'n lid van die Tachikinien familie. Die unieke benadering van hierdie projek was om die rol van Neurokinien B in pre-eklampsie te ondersoek op 'n genetiese grondslag. Dit is bereik deur bio-informatiewe karakterisering van die neurokinien B (TAC3) en neurokinien B reseptor (TACR3) en deur mutasie sifting op DNA monsters van 30 pasiënte met pre-eklampsie (waarvan 10 ook abruptio placentae gehad het) en twintig kontrole individue met behulp van Multiphor gel elektroforese en ge-outomatiseerde volgorde bepaling. Drie volgorde variasies is geïdentifiseer in die TAC3 geen en sluit in: (i) 5' UTR variant (-25 c-t); (ii) introniese variant IVS3-53 (t-g) en (iii) 3' UTR variant in ekson 7 (479, t-e). Slegs die -25 c-t variasie is voorheen raporteer (SNP databasis). Nog twee variante is ook gevind in die TACR3 geen: (i) ekson 3 variant (nt 857, a-t) en (ii) 3' UTR variant, amplikon 5b (nt 1471, t-e); hierdie laaste een is al in die SNP databasis raporteer. In 'n analise van genotipe en allele frekwensies is slegs homosigositeit vir variant TAC3 -25 c-t geassosieër met 'n verhoogde risiko vir preeklampsie (RR 3.33, p=0.03). Verdere werk sal nou fokus op die genotipering van groter en gestratifiseerde pasiënt kohorte en transfeksie studies om splitsing potensiaal en funksionele gevolge van mutante allele te ondersoek. Hierdie data is die eerste gedokumenteerde mutasie sifting van die TAC3 en TACR3 gene en verslag word gelewer van unieke variasies in pasiënte met pre-eklampsie.

Please refer to this item in SUNScholar by using the following persistent URL: http://hdl.handle.net/10019.1/50029
This item appears in the following collections: