Browsing by Author "Gerber, Jaclyn"
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- ItemCytochrome P450 polymorphisms : relevance in two South African disease populations(Stellenbosch : Stellenbosch University, 2003-12) Gerber, Jaclyn; Warnich, L.; Kotze, Maritha J.; Stellenbosch University. Faculty of Science. Dept. of Microbiology.ENGLISH ABSTRACT: With knowledge of the human genome increasing constantly we are continually faced with new and potentially groundbreaking methods for managing, treating and/or identifying diseases and predisposition to diseases and conditions at a genetic level. The human cytochrome P450 (CYP) super-family of genes code for enzymes that can participate in metabolism of drugs and foreign chemicals and in steroid synthesis and metabolism. Mutations in these genes may contribute to clinically relevant diseases. In this study, the effects of mutations within four CYP genes were evaluated in two South African disease groups - variegate porphyria and breast cancer. Variegate porphyria (VP) has an unusually high incidence in South Africa due to the R59W founder mutation in the protoporphyrinogen oxidase (PPOX) gene that causes a disruption in the haem biosynthetic pathway. VP presents with variable clinical symptoms and has a relatively low penetrance. It is expected that environmental factors and modifier genes play a role in the clinical expression of VP. CYP genes are implicated as candidate modifier genes for the expression of VP due to the function they have in metabolising many drugs contraindicated in porphyria patients, and the necessity of haem binding to the apoprotein to produce a functional CYP enzyme. This is the first study to investigate CYPs as possible modifier genes for VP clinical expression. Six CYP polymorphisms (CYPIAlml, CYPIAlm2, CYPIA2 - 734 C>A, CYPIBI 8372 A>C, CYP2D6*3, CYP2D6*4), associated with four CYP loci, were genotyped in a VP population and a suitable control population. The results observed are suggestive of CYPIAlml and CYPIBI playing a role as modifiers for the clinical expression of VP as they were significantly associated (PA and CYPIBI 8372 A>C). This represents the first investigation of the potential role of CYPs as breast cancer risk modifiers in the two South African populations. Significant differences were observed (PC polymorphism in the population of mixed ancestry. Vast differences in allele frequencies were also observed between the two groups of breast cancer populations. These results emphasize the importance of population-based risk assessment when genetic testing and counselling for complex disease susceptibility is offered. The results of this study provide the first evidence suggesting a role for CYPs in modifying the clinical expression of VP and in acting as risk factors for developing breast cancer in a South African population.