Table 1.
Coding variants associated with FG and FI levels at exome-wide significance.
Table 2.
G6PC2 gene-based association with FG levels using SKAT and BURDEN test
Figure 1.
Haplotypes of the lead non-coding GWAS SNP rs560887 and the three coding variants.
rs138726309 (p.His177Tyr), rs2232323 (p.Tyr207Ser), and rs492594 (p.Val219Leu), obtained from 4,442 unrelated individuals from the Oxford Biobank. (A) Percentage minor allele frequency (MAF) and effect size estimates () of the four variants reported for the minor allele in mmol/L of FG after adjustment for age, sex, and BMI. (B) Haplotypes of the four associated variants in G6PC2 revealed that the glucose-lowering Leu219 allele was carried exclusively in cis with the glucose-raising allele at the GWAS SNP. Wild-type, glucose-raising alleles are circled in blue and the mutant, glucose-lowering alleles are circled in red. Diameter of the circle is proportional to the effect size estimates. Haplotype association was performed with FG derived residuals (after adjustment for age, sex, and BMI) using the most frequent haplotype as baseline.
Figure 2.
Functional characterization of wild type and variant G6PC2 proteins.
(A) Expression levels in HEK293 and (B) INS-1E cells were determined by western blot and densitometry analysis. The multiple bands on the western blot are likely to represent glycosylated G6PC2 protein products. Data are presented as mean ± standard error of the mean for at least three independent experiments. Significant differences are indicated as ** P<0.01; *** P<0.001; **** P<0.0001. EV, empty vector; WT, wild type. (C) Expression levels in HEK293 and INS-1E cells in the presence of proteasomal inhibitor MG-132 or lysosomal inhibitor chloroquine were determined by western blot. (D) Cellular localization in HEK293 cells was assessed by immunofluorescence microscopy. Cells were double immunostained for FLAG tag (green) and calnexin (red), and merged images with a DNA stain (blue) are shown. Images were taken with laser settings that were optimized separately for each sample. Scale bar, 10µm.