Multiple functional polymorphisms in the G6PC2 gene contribute to the association with higher fasting plasma glucose levels

• Published in: Diabetologia Vol. 56; no. 6; pp. 1306 - 1316
• Main Authors: Baerenwald, D. A., Bonnefond, A., Bouatia-Naji, N., Flemming, B. P., Umunakwe, O. C., Oeser, J. K., Pound, L. D., Conley, N. L., Cauchi, S., Lobbens, S., Eury, E., Balkau, B., Lantieri, O., Dadi, P. K., Jacobson, D. A., Froguel, P., O’Brien, R. M.
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer-Verlag 01.06.2013; Springer; Springer Nature B.V
• Subjects: Alleles; Biological and medical sciences; Blood Glucose - metabolism; Diabetes Mellitus - blood; Diabetes Mellitus - genetics; Diabetes. Impaired glucose tolerance; Endocrine pancreas. Apud cells (diseases); Endocrinopathies; Epidemiology; Etiopathogenesis. Screening. Investigations. Target tissue resistance; Fasting; Female; Gene expression; Gene Expression Regulation; Genomes; Genotype; Glucose; Glucose-6-Phosphatase - genetics; HeLa Cells; Human Physiology; Humans; Hypotheses; Insulin resistance; Internal Medicine; Male; Medical sciences; Medicine; Medicine & Public Health; Metabolic Diseases; Plasma; Polymorphism; Polymorphism, Single Nucleotide; Promoter Regions, Genetic; RNA Splicing; RNA, Messenger - metabolism; Transcription factors; France; Paris France; Fasting plasma glucose; Splicing; Transcription; Pancreatic islet; Beta cell; /; Endocrinopathy; Fasting; G6PC2/IGRP; Diabetes mellitus; Langerhans islet; Glucose; Association; Gene; β Cell; Endocrine pancreas; Polymorphism
• ISSN: 0012-186X; 1432-0428
• DOI: 10.1007/s00125-013-2875-3

Aims/hypothesis We previously identified the G6PC2 locus as a strong determinant of fasting plasma glucose (FPG) and showed that a common G6PC2 intronic single nucleotide polymorphism (SNP) (rs560887) and two common G6PC2 promoter SNPs (rs573225 and rs13431652) are highly associated with FPG. However, these promoter SNPs have complex effects on G6PC2 fusion gene expression, and our data suggested that only rs13431652 is a potentially causative SNP. Here we examine the effect of rs560887 on G6PC2 pre-mRNA splicing and the contribution of an additional common G6PC2 promoter SNP, rs2232316, to the association signal. Methods Minigene analyses were used to characterise the effect of rs560887 on G6PC2 pre-mRNA splicing. Fusion gene and gel retardation analyses characterised the effect of rs2232316 on G6PC2 promoter activity and transcription factor binding. The genetic association of rs2232316 with FPG variation was assessed using regression adjusted for age, sex and BMI in 4,220 Europeans with normal FPG. Results The rs560887-G allele was shown to enhance G6PC2 pre-mRNA splicing, whereas the rs2232316-A allele enhanced G6PC2 transcription by promoting Foxa2 binding. Genetic analyses provide evidence for association of the rs2232316-A allele with increased FPG ( β  = 0.04 mmol/l; p  = 4.3 × 10 −3 ) as part of the same signal as rs560887, rs573225 and rs13431652. Conclusions/interpretation As with rs13431652, the in situ functional data with rs560887 and rs2232316 are in accord with the putative function of G6PC2 in pancreatic islets, and suggest that all three are potentially causative SNPs that contribute to the association between G6PC2 and FPG.