Bone Abstracts

Introduction: The etiology of Paget’s disease of bone (PDB) is not fully understood, but genetic factors play a clearly important role. Single nucleotide polymorphisms (SNPs) of OPTN gene within PDB6 locus have been highly associated with PDB, but no PDB causal mutation or functional effect on PDB development were reported to date. We aimed to identify functional SNPs associated with this bone disease.

Methods: Relevant candidate genes from PDB6 locus were selected based on their known biological function in bone. For each gene the coding region, splice sites, 5′ and 3′ UTRs and promoter were amplified, using an initial discovery sample of French–Canadian PDB patients from 38 different families. For each variant identified, we performed in silico analysis to determine its predicted functional effect.

Results: Sequence analysis of our sample allowed us to identify sixty SNPs already reported in the NCBI database and seven variants previously unknown in all our five candidate genes – OPTN, CAMK1D, PHYH, SEPHS1, and CCDC3. The in silico analysis showed that the majority of the SNPs could be related to alterations in gene expression possibly affecting bone cell function resulting in bone related diseases, as PDB. Furthermore, our in silico analysis performed on the variant rs3829923 found in the OPTN promoter, identified putative binding sites for NRF2, E74A and SAP1 transcription factors (TFs) overlapping the SNP containing the G, whereas it was absent in the sequence containing the A. We hypothesized that this polymorphism may alter the binding of these TFs to this promoter, affecting OPTN expression. This possibility is now being evaluated.

Conclusion: PBB6 appears to be a good locus containing several bone related genes that may be involved in PDB pathogenesis. Further functional analysis using in vitro transient transfection assays are required to investigate the effect of rs3829923 in OPTN promoter.