The functionality of African-specific variants in the TGFB1 regulatory region and their potential role in HIVAN

• Published in: Clinical and experimental nephrology Vol. 22; no. 4; pp. 764 - 772
• Main Authors: Nel, M., Buys, J.-M., Botha, F. C. J., Wearne, N., Prince, S., Heckmann, J. M.
• Format: Journal Article
• Language: English
• Published: Singapore Springer Singapore 01.08.2018; Springer Nature B.V
• Subjects: Africa; AIDS-Associated Nephropathy - ethnology; AIDS-Associated Nephropathy - genetics; Biopsy; Cell Line; Cell lines; Fibroblasts; Gene expression; Gene silencing; Haplotypes; HIV; Human immunodeficiency virus; Humans; Image processing; Kidney; Medicine; Medicine & Public Health; Nephrology; Nephropathy; Optical density; Original Article; Polymorphism, Single Nucleotide; Regulatory Sequences, Nucleic Acid; Reporter gene; Single-nucleotide polymorphism; Tat protein; Transforming Growth Factor beta1 - genetics; Transforming growth factor-b1; Urology; Africa; Promoter; Transforming growth factor B1; HIVAN; Kidney; Africa; Polymorphism
• ISSN: 1342-1751; 1437-7799
• DOI: 10.1007/s10157-017-1516-4

Background Transcription of transforming growth factor beta-1 (TGF-β1) is regulated by a polymorphic promoter region containing African-specific single nucleotide polymorphisms (SNPs). Some of these SNPs have higher frequencies among Southern Africans compared to other African populations and their functionality has only been partially studied. Due to the high prevalence of HIV-associated nephropathy (HIVAN) in Africans we hypothesized that functional African TGFB1 -promoter SNPs may contribute to HIVAN pathogenesis. Methods The functionality of the TGFB1 -1347 C > T variant and African-specific variants ( -1287 G > A, -1154 C > T, -387 C > T and -14 G > A ) were examined by measuring reporter gene expression in kidney and fibroblast cell lines co-transfected with TGFB1 -promoter constructs and an HIV-Tat expression vector. TGF-β1 immunohistochemical staining was performed on kidney biopsies with HIVAN ( n  = 18) and compared to control biopsies without HIVAN or tubulointerstitial disease ( n  = 12) using semi-quantitative and digital image analysis. HIVAN cases were genotyped for TGFB1 -1347 and -387 SNP variants. Results TGFB1- promoter haplotypes containing the African -387 T -allele resulted in ~ five-fold repression of TGFB1- promoter activity compared to -387 C haplotypes ( p  ≤ 0.024). HIV-Tat upregulated TGFB1- promoter activity for haplotypes containing - 1347 T and - 387 T in transfected renal cells (≈ 1.6-fold; p  ≤ 0.030) and fibroblasts (≈ 1.3-fold; p  ≤ 0.016). The renal interstitium from HIVAN biopsies, compared to HIV-positive and -negative controls, differed in the semi-quantitative TGF-β1 staining and digital optical density analyses. The TGFB1 -1347 and - 387 genotypes in HIVAN cases were similar to population controls. Conclusion African-specific haplotypes lower TGFB1- promoter activity and expression levels and HIV-Tat upregulates TGFB1 promoter activity irrespective of the haplotype.