Regulatory constraint and selection during human knee evolution drive modern osteoarthritis risk

The evolution of human bipedalism exposed the knee to unique biomechanical challenges, requiring changes in knee anatomy giving rise to the modern-day configuration. In order to better understand the relationship between derived knee morphology and the genetic factors associated with osteoarthritis risk, we performed epigenetic profiling of murine forelimb/hindlimb growth plates to identify regulatory elements shaping formation of specific knee structures, identifying signals of ancient positive selection upon which more recent genetic drift overlaps risk-associated loci. Our functional analyses of an osteoarthritis-risk variant within a reproducibly-associated locus establishes a novel model for studying this degenerative disease. Overall design: Examination of open chromatin regions in multiple different growth plates (proximal vs distal femur, tibia, humerus, radius) at E15.5