Functional effects of genetic variants in the 11β-hydroxylase (CYP11B1) gene

Marianne Barr, Scott M. MacKenzie, Donna M. Wilkinson, Christine D. Holloway, Elaine C. Friel, Stephen Miller, Tom MacDonald, Robert Fraser, John M.C. Connell, Eleanor Davies

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    16 Citations (Scopus)

    Abstract

    Objective: We previously described an association between the -344C/T 5′-untranslated region (UTR) polymorphism in the CYP11B2 (aldosterone synthase) gene and hypertension with a raised aldosterone to renin ratio (ARR); the same genetic variant is also associated with impaired adrenal 11β-hydroxylase efficiency. The -344 polymorphism does not seem to be functional, so is likely to be in linkage with variants in CYP11B1 that determine the associated variation in 11β-hydroxylase efficiency. We therefore aimed to determine whether there is an association between CYP11B1 variants and hypertension and/or an altered ARR. Design and measurements: We screened 160 subjects divided into four groups, normotensive controls, unselected hypertensive subjects, and hypertensive subjects with either a high (≥ 750) or low ARR (≤ 200), for variants in the coding region of CYP11B1 by single-stranded conformation polymorphism (SSCP) and direct sequencing. The effects of these variants on enzyme function were assessed by conversion of 11-deoxycortisol to cortisol and 11-deoxycorticosterone (DOC) to corticosterone. Results: Eight novel missense mutations were identified in the CYP11B1 gene that alter the encoded amino acids: R43Q, L83S, H125R, P135S, F139L, L158P, L186V and T196A. In each case they were heterozygous changes. However, no mutations were identified that could account for hypertension and/or a raised ARR. The variants L158P and L83S severely impaired enzyme function while R43Q, F139L, P135S and T196A enzymes resulted in product levels that were approximately 30-50% that of wild-type levels. The variant enzymes H125R and L186V resulted in substrate-specific alterations in enzyme function. H125R decreased conversion of 11-deoxycortisol to cortisol and L186V increased 11-deoxycortisol conversion. Neither had an effect on the conversion of DOC to corticosterone. Conclusion: No variants were identified in the coding region of CYP11B1 that could account for hypertension and/or a raised ARR. However, this in vitro study identifies the importance of these affected residues to enzyme function and will inform subsequent studies of structure-function relationships.

    Original languageEnglish
    Pages (from-to)816-825
    Number of pages10
    JournalClinical Endocrinology
    Volume65
    Issue number6
    DOIs
    Publication statusPublished - Dec 2006

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  • Cite this

    Barr, M., MacKenzie, S. M., Wilkinson, D. M., Holloway, C. D., Friel, E. C., Miller, S., MacDonald, T., Fraser, R., Connell, J. M. C., & Davies, E. (2006). Functional effects of genetic variants in the 11β-hydroxylase (CYP11B1) gene. Clinical Endocrinology, 65(6), 816-825. https://doi.org/10.1111/j.1365-2265.2006.02673.x