Bi-allelic EPHA2 mutations cause dysosteosclerosis by inhibiting osteoclastogenesis and enhancing osteoblastogenesis

Erythropoietin-producing hepatocellular (EPH) receptors, the largest receptor tyrosine kinase family, have been shown to play a crucial role in normal physiological processes and pathologies. EPHA2, encoded by EPHA2 gene, a member of the EPH receptor family, has been implicated in cataracts and various bone tumors, including osteosarcoma, chondrosarcoma, and bone metastases of breast cancer. However, no association between the EPHA2 gene and genetic skeletal disorders has been reported to date. Here, we identified a Chinese family with a diagnosis of dysosteosclerosis, presenting with significant increase in lumbar spine bone mineral density, multifocal sclerotic lesions throughout the body, sclerotic skull, platyspondyly and sandwich vertebrae, and demonstrated compound heterozygous mutations in EPHA2 gene (c.890 C > T, p.Thr297Met; c.988dupT, p.Ser330PhefsX51). We observed a reduction in numerous sclerotic lesions in patients during the five-year follow-up. To systematically investigate the molecular mechanisms of pathogenesis, we employed a range of methodologies, including in vitro cellular assays, genome-wide association studies analysis, induced pluripotent stem cells models and Epha2 knockout mice models. We have determined that loss-of-function mutations in EPHA2 gene lead to dysosteosclerosis through enhancing mesenchymal stem cells osteogenic differentiation and downregulating the p38-MAPK pathway, leading to decreased osteoclast differentiation. Consequently, we proposed and validated EPHA2 as a viable therapeutic target for osteoporosis by constructing femoral fracture mice models and ovariectomized mice models. In summary, this study identifies bi-allelic loss-of-function mutations in EPHA2 gene lead to dysosteosclerosis and its underlying mechanisms, and suggests EPHA2 as a potential therapeutic target for osteoporosis.