Cellular communication network factor 2 (CCN2) is a secreted extracellular matrix-associated protein, and its aberrantly increased expression has been implicated in a diversity of diseases involving pathological processes of fibrosis, chronic inflammation, or tissue injury, which has promoted the evaluation of CCN2 as therapeutic targets for multiple disorders. However, human phenotypes associated with CCN2 deficiency have remained enigmatic; variants in CCN2 have not yet been associated with a human phenotype. Here, we collected families diagnosed with spondyloepimetaphyseal dysplasia (SEMD), and screened candidate pathogenic genes for families without known genetic causes using next-generation sequencing. We identified a monoallelic variant in signal peptide of CCN2 (NM_001901.2: c.65 G > C [p.Arg22Pro]) as the cause of SEMD in 14 subjects presenting with different degree of short stature, premature osteoarthritis, and osteoporosis. Affected subjects showed decreased serum CCN2 levels. Cell lines harboring the variant displayed decreased amount of CCN2 proteins in culture medium and an increased intracellular retention, indicating impaired protein secretion. And the variant weakened the stimulation effect of CCN2 on osteogenesis of bone marrow mesenchymal stem cells. Zebrafish ccn2a knockout model and osteoblast lineage-specific Ccn2-deficient mice (Ccn2^fl/fl;Prx1^Cre) partially recapitulated the phenotypes including low bone mass observed in affected subjects. Pathological mechanism implicated in the skeletal abnormality in Ccn2^fl/fl;Prx1^Cre mice involved decreased bone formation, increased bone resorption, and abnormal growth plate formation. Collectively, our study indicate that monoallelic variants in CCN2 lead to a human inherited skeletal dysplasia, and highlight the critical role of CCN2 in osteogenesis in human.

细胞通讯网络因子 2 （CCN2） 是一种分泌的细胞外基质相关蛋白，其异常增加的表达与涉及纤维化、慢性炎症或组织损伤等病理过程的多种疾病有关，这促进了 CCN2 作为多种疾病治疗靶点的评价。然而，与 CCN2 缺陷相关的人类表型仍然是个谜;CCN2 中的变体尚未与人类表型相关。在这里，我们收集了诊断为脊椎骨干骺端发育不良 （SEMD） 的家庭，并使用下一代测序为没有已知遗传原因的家庭筛选候选致病基因。我们确定了 CCN2 信号肽中的单等位基因变异 （NM_001901.2： c.65 G > C [p.Arg22Pro]） 是 14 名表现为不同程度身材矮小、早发性骨关节炎和骨质疏松症的受试者 SEMD 的原因。受影响的受试者表现出血清 CCN2 水平降低。携带该变体的细胞系在培养基中显示 CCN2 蛋白量减少，细胞内保留增加，表明蛋白质分泌受损。该变体减弱了 CCN2 对骨髓间充质干细胞成骨的刺激作用。斑马鱼 ccn2a 敲除模型和成骨细胞谱系特异性 Ccn2 缺陷小鼠 （Ccn2^fl/fl;Prx1^Cre） 部分概括了表型，包括在受影响受试者中观察到的低骨量。 与 Ccn2^fl/fl 骨骼异常有关的病理机制;Prx1^Cre 小鼠涉及骨形成减少、骨吸收增加和生长板形成异常。总的来说，我们的研究表明，CCN2 中的单等位基因变异会导致人类遗传性骨骼发育不良，并强调了 CCN2 在人类成骨中的关键作用。