Background: We identified a family with early onset X-linked osteoporosis and fractures
Methods: We performed whole exome sequencing of the X chromosome in three affected members. After discovering a putative pathogenic variant we performed Sanger sequencing of all exons of this gene in other members of this family and in 95 unrelated men suspected of OI type I without COL1A1/2 mutations. We also genotyped a SNP in this gene (minor allele frequency 0.02) in elderly subjects in three cohorts of a prospective population-based study for association analyses with BMD and incident fractures. We performed functional studies in zebrafish after pls3 knock-down and expression analysis of PLS3 in human differentiating mesenchymal stem cells (MSCs) and in differentiating human osteoclasts.
Results: We discovered five pathogenic variants in PLS3 in five families with osteoporosis and osteoporotic fractures. Furthermore, a rare SNP in PLS3 (rs140121121) was associated with a twofold increased fracture risk in heterozygous postmenopausal women in a population-based study and with decreased BMD, although increased fracture risk was not fully explained by BMD. PLS3 is expressed during osteogenic and decreased during adipogenic differentiation of MSCs and its expression increased during differentiation and activation of osteoclasts. Knock-down experiments in zebrafish showed malformations of the developing craniofacial bone structure, body axis and tail that could be rescued dose-dependently by human PLS3 mRNA, supporting the concept that PLS3 is a bone regulatory protein.
Conclusion: We identified loss-of-function variants in PLS3 as a monogenetic cause of X-linked osteoporosis and osteoporotic fractures and found a rare SNP in this gene associated with a twofold increased fracture risk and decreased BMD in heterozygous women in a population-based study, indicating genetic variation in PLS3 as a novel factor involved in common, multifactorial osteoporosis.
17 - 20 May 2014
European Calcified Tissue Society