KDM6A-Mediated Regulation of Cranial Frontal Bone Suture Fusion in Mice Is Sex Dependent

The five flat bones of developing cranial plates are bounded by fibrous sutures, which remain open during development to accommodate for the growing brain. Kdm6A is a demethylase that removes the epigenetic repressive mark, trimethylated lysine 27 on histone 3 (H3K27me3), from the promoters of osteogenic genes, and has previously been reported to promote osteogenesis in cranial bone cells. This study generated a mesenchyme-specific deletion of a histone demethylase, Kdm6a, to assess the effects of Kdm6a loss, in cranial plate development and suture fusion. The results showed that the loss of Kdm6a in Prx1 cranial cells caused increased anterior width and length in the calvaria of both male and female mice. However, the posterior length was further decreased in female mice. Moreover, loss of Kdm6a resulted in suppression of late suture development and calvarial frontal bone formation predominantly in female mice. In vitro assessment of calvaria cultures isolated from female Kdm6a knockout mice found significantly suppressed calvarial osteogenic differentiation potential, associated with decreased gene expression levels of Runx2 and Alkaline Phosphatase and increased levels of the suppressive mark, H3K27me3, on the respective gene promoters. Conversely, cultured calvaria bone cultures isolated from male Kdm6a knockout mice exhibited an increased osteogenic differentiation potential. Interestingly, the milder effects on cranial suture development in Kdm6a knockout male mice, were associated with an overcompensation of the Kdm6a Y-homolog, Kdm6c, and increased expression levels of Kdm6b in calvarial bone cultures. Taken together, these data demonstrate a role for Kdm6a during calvarial development and patterning, predominantly in female mice, and highlight the potential role of Kdm6 family members in patients with unexplained craniofacial deformities.