Characterisation of a functional intronic polymorphism in the human growth hormone (GH1) gene.
The +1169A allele of the A/T single nucleotide polymorphism (SNP; rs2665802), located within intron 4 of the human growth hormone 1 ( GH1 ) gene, has been associated with reduced levels of circulating GH and insulin-like growth factor 1, a reduced risk of colorectal cancer and a predisposition to osteoporosis. Whether this intronic SNP is itself the functional polymorphism responsible for exerting a direct effect on GH1 gene expression, however, or whether it is instead in linkage disequilibrium with the functional SNP, has been an open question. The evolutionary conservation of the +1169T allele (and the surrounding intronic sequence) in the bovine genome, as well as in primate genomes, is, however, suggestive of its functionality. Although a potential alternative splice site spans the location of the +1169 SNP, polymerase chain reaction-based assays failed to yield any evidence for alternative splicing associated with either allele. To determine whether the +1169 SNP, in different allelic combinations with SNPs at -278 (G/T), -57 (T/G) and +2103 (C/T), exerts a direct effect on gene expression and/or GH secretion, we performed a series of transfections of various GH1 haplotype-expressing constructs into rat GC (somatotroph) cells. The results obtained provided evidence to support the contention that the +1169A allele contributes directly to the observed reduction in both GH1 gene expression and GH secretion. Part of the apparent influence of the +1169A-bearing allele on GH1 gene expression and GH secretion may still, however, be attributable to alleles of additional SNPs in cis to +1169A and located within either the promoter or the 3'-flanking region.
Millar
David S
DS
Institute of Medical Genetics, Cardiff University, Heath Park, UK. millar@cardiff.ac.uk
Horan
Martin
M
Chuzhanova
Nadia A
NA
Cooper
David N
DN
D024509:3' Flanking Region / Q000235:genetics; D000483:Alleles; D017398:Alternative Splicing / Q000235:genetics; D000818:Animals; D001483:Base Sequence; D002460:Cell Line; D017124:Conserved Sequence / Q000235:genetics; D019143:Evolution, Molecular; D005786:Gene Expression Regulation; D006239:Haplotypes / Q000235:genetics; D019382:Human Growth Hormone / Q000235:genetics*; D006801:Humans; D007438:Introns / Q000235:genetics*; D015810:Linkage Disequilibrium / Q000235:genetics; D008969:Molecular Sequence Data; D020641:Polymorphism, Single Nucleotide / Q000235:genetics*; D011401:Promoter Regions, Genetic / Q000235:genetics; D022821:RNA Splice Sites / Q000235:genetics; D051381:Rats; D012689:Sequence Homology, Nucleic Acid; D052683:Somatotrophs / Q000378:metabolism; D044465:White People / Q000235:genetics
D022821:RNA Splice Sites; D019382:Human Growth Hormone