Thesis (MScMedSc)--Stellenbosch University, 2012. / Bibliography / ENGLISH ABSTRACT: South Africa is ranked amongst the top tuberculosis (TB) burden countries in the world and
the Western Cape has a particularly high incidence of the disease. Previous studies have
showed that several genes may play crucial roles in susceptibility to TB. In this study, we
investigated the role of three genes previously associated with susceptibility to TB and
progression to disease. These genes were Surfactant protein D (SFTPD), Macrophage
receptor with collagenous structure (MARCO) and CD14. The proteins from these genes bind
M. tuberculosis and are involved in the uptake of the bacteria into macrophages.
The study investigated the role of ten polymorphisms from SFTPD and MARCO within a
South African Coloured (SAC) population, where tuberculosis is highly prevalent. A casecontrol
study design was used and polymorphisms were genotyped with Taqman®
genotyping assays and amplification refractory mutation system polymerase chain reaction
(ARMS-PCR). The results were analysed for association with disease, linkage disequilibrium,
haplotypes and gene-gene interactions. Allele and genotype frequencies were also determined
which allowed for comparisons to other populations.
Five SNPs were associated with TB: two in SFTPD (rs1923537; rs2255326) and three in
MARCO (rs1318645; rs3943679; rs2119112). The associated SNPs were located in regions
other than exons and the effects of polymorphisms in these regions are not well understood
but studies in other genes have shown them to play a functional role. Gene-gene interaction
analysis showed that polymorphisms interacted with each other within and between genes,
illustrating the importance of epistasis and the complexity of the genetic influences on TB.
In addition to the case-control association studies, the role of the rs2569190 promoter SNP in
CD14 was assessed. Gene-expression analysis was conducted with qPCR and a reporter gene
assay and results from both of these approaches showed that individuals with the TT
genotype had a twofold greater expression level than individuals with the CC genotype.
Previously, the TT genotype has been associated with stronger promoter activity and
expression of soluble CD14 in serum. Since the TT genotype was present at a higher
frequency in the control group, we speculate that greater expression of CD14 may contribute
to a more TB resistant phenotype. The work presented in this study illustrates the importance of the host genetic component of
TB. Genetic studies will eventually revolutionize the current treatment regime as the
identification of vulnerable individuals and populations will aid in the development of
personalised medicines. / AFRIKAANSE OPSOMMING: Suid-Afrika is een van die top tuberkulose (TB) lande in die wêreld en die Wes-Kaap het
veral ‘n hoë insidensie van die siekte. Vorige studies het gewys dat verskeie gene bydra to die
vatbaarheid vir tuberkulose. In hierdie studie het ons drie gene, wat voorheen vir vatbaarheid
vir tuberkulose en progressie na die siekte ondersoek is, bestudeer. Hierdie gene is Surfactant
protein D (SFTPD), Macrophage receptor with collagenous structure (MARCO) en CD14.
Die proteïene van hierdie gene bind M. tuberculosis en is betrokke in die opname van die
bakterieë in die makrofages.
Hierdie studie het tien polimorfismes van SFTPD en MARCO in die Suid-Afrikaanse
Kleurlingbevolking (SAK), wat ‘n hoë TB insidensie het, getoets. Pasiënt-kontrole assosiasie
studies is gedoen en polimorfismes is gegenotipeer met Taqman® genotiperingsisteem en die
amplifikasie refraktoriese mutasie sisteem polimerase ketting reaksie (ARMS-PCR). Die
resultate is geanaliseer vir assosiasies met TB, koppelings disekwilibrium, haplotipes en
geen-geen interaksies. Alleel en genotype frekwensies is ook bepaal en vergelyk met die van
ander bevolkings.
Vyf enkel nukleotied polimorfismes (ENPs) is met TB geassosieer: twee in SFTPD
(rs1923537; rs2255326) en drie in MARCO (rs1318645; rs3943679; rs2119112). Die
geassosieerde ENPs was nie in eksons nie. Die effek van polimorfismes in areas anders as
eksons word nie goed verstaan nie, maar studies het bewys dat hulle wel ‘n funksionele rol
kan hê. Geen-geen interaksie analise het gewys dat polimorfismes interaksies met mekaar
binne sowel as tussen gene gehad het, wat die belangrikheid van epistase en die kompleksiteit
van genetiese invloede op TB illustreer.
Tesame met die pasiënt-kontrole assosiasie studies is die rol van die rs2569190 promoter
ENP in CD14 ook ondersoek. Geenuitdrukkingsanalise is gedoen met qPKR en
rapporteerder geen toetse. Die resultate van beide hierdie benaderings het gewys dat
individue met die TT genotipe twee keer soveel uitdrukkingsvlakke gehad het as individue
met die CC genotipe. Die TT genotipe is voorheen geassosieer met sterk promoter aktiwiteit
en die uitdrukking van oplosbare CD14 in serum. Aangesien die TT genotipe meer in die kontrolegroep gevind is, spekuleer ons dat die hoër uitdrukking van CD14 kan bydra tot ‘n
meer TB weerstandbiedende fenotipe.
Hierdie werk illustreer die belangrikheid van die gasheer genetiese komponent in TB.
Genetiese studies sal in die toekoms die huidige behandeling regime revolusioneer, aangesien
die identifikasie van individue en bevolkings met ‘n hoë risiko om TB te ontwikkel sal bydra
tot die ontwikkeling van persoonlike medisynes. / The National Research Foundation (NRF); the South African Medical Research Council
(MRC); Stellenbosch University and the Harry Crossley Foundation.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/20409 |
| Date | 03 1900 |
| Creators | Wagman, Chandre K. |
| Contributors | Hoal, Eileen, Moller, Marlo, Stellenbosch University. Faculty of Medicine and Health Sciences. Dept. of Biomedical Science. Division of Molecular Biology and Human Genetics. |
| Publisher | Stellenbosch : Stellenbosch University |
| Source Sets | South African National ETD Portal |
| Language | en_ZA, English |
| Detected Language | English |
| Type | Thesis |
| Format | vii, 132 p. : col. ill. |
| Rights | Stellenbosch University |
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