Genetic regulatory mechanisms in human osteoclasts suggest a role for the STMP1 and DCSTAMP genes in Paget's disease of bone

Abstract

Paget's disease of bone (PDB) is characterised by focal abnormalities of bone remodelling, with increased osteoclastic resorption the primary feature of the disease. Genetic factors have been shown to play an important role in PDB, and genome-wide association studies (GWAS) have identified 7 genetic loci as associated with PDB at the genome-wide level. Expression quantitative trait locus (eQTL) studies using cell types that are directly relevant to the disease of interest are increasingly being used to identify putative effector genes for GWAS loci. We have recently constructed a unique osteoclast-specific eQTL resource using cells differentiated in vitro from 158 subjects for study of the genetics of bone disease. Considering the major role osteoclasts have in PDB, we used this resource to investigate potential genetic regulatory effects for the 7 PDB genome-wide significant loci on genes located within 500 kb of each locus. After correction for multiple testing, we observed statistically significant associations for rs4294134 with expression of the gene STMP1, and rs2458413 with expression of the genes DPYS and DCSTAMP. The eQTL associations observed for rs4294134 with STMP1, and rs2458413 with DCSTAMP were further supported by eQTL data from other tissue types. The product of the STMP1 gene has not been extensively studied, however the DCSTAMP gene has an established role in osteoclast differentiation and the associations seen between rs2458413 and PDB are likely mediated through regulatory effects on this gene. This study highlights the value of eQTL data in determining which genes are relevant to GWAS loci.

Figure 1

Regional association plots generated using the eQTL association results for (A) STMP1, (B) DPYS and (C) DCSTAMP from the osteoclast-specific dataset. Genetic variants within 400 kb of rs4294134 or rs2458413 are depicted (x axis) along with their eQTL P value (−log10). For DPYS and DCSTAMP, the maximally associated eQTL variant from the region is also indicated (rs12674899 and rs2458418, respectively). Variants are colour coded according to their LD (r²) with PDB GWAS loci rs4294134 or rs2458413 (1000GP Nov 2014 EUR population). The red arrows indicate significant associations between rs4294134 or rs2458413 and expression of nearby genes, with the allelic effects on normalised gene expression presented in the box-and-whisker plots. The recombination rate (blue line) and position of genes, their exons and direction of transcription is also indicated.