A GREM1 gene variant associates with diabetic nephropathy

Abstract

Gremlin, a cell growth and differentiation factor, promotes the development of diabetic nephropathy in animal models, but whether GREM1 gene variants associate with diabetic nephropathy is unknown. We comprehensively screened the 5' upstream region (including the predicted promoter), all exons, intron-exon boundaries, complete untranslated regions, and the 3' region downstream of the GREM1 gene. We identified 31 unique variants, including 24 with a minor allele frequency exceeding 5%, and 9 haplotype-tagging single nucleotide polymorphisms (htSNPs). We selected one additional variant that we predicted to alter transcription factor binding. We genotyped 709 individuals with type 1 diabetes of whom 267 had nephropathy (cases) and 442 had no evidence of kidney disease (controls). Three individual SNPs significantly associated with nephropathy at the 5% level, and two remained significant after adjustment for multiple testing. Subsequently, we genotyped a replicate population comprising 597 cases and 502 controls: this population supported an association with one of the SNPs (rs1129456; P = 0.0003). Combined analysis, adjusted for recruitment center (n = 8), suggested that the T allele conferred greater odds of nephropathy (OR 1.69; 95% CI 1.36 to 2.11). In summary, the GREM1 variant rs1129456 associates with diabetic nephropathy, perhaps explaining some of the genetic susceptibility to this condition.

Figure 1.

Linkage disequilibrium at the Grem1 locus. (a) Relationship between 23 biallelic SNPs resequenced in 48 control individuals from the Young Hearts collection. Pairwise comparisons where r² = 0 (no correlation) are highlighted in white through a gray spectrum to black, where r² = 1 (perfect correlation) for SNPs that are perfect proxies for each other. (b) Major haplotypes identified from snphap.

Figure 2.

Interrogation of miRBase highlighted a computationally predicted target site. The sequence of miRNA hsa-miR-574-3p is aligned to our resequenced data for the GREM1 gene with alignment across six species, demonstrating a high degree of conservation at this loci.

Figure 3.

In silico, multiple alignment of protein sequences encoded by the GREM1 gene in six species. The comparison reveals strong conservation across the amino acids comprising the H. sapiens GREM1 protein