Denipah-Cook Qootsvenma, Saxton Bryanna V, Artinger Kristin B, Shull Lomeli C
Department of Biology, University of New Mexico, Albuquerque, NM, USA.
Department of Diagnostic and Biological Sciences, University of Minnesota School of Dentistry, Minneapolis, MN, USA.
bioRxiv. 2025 Jul 22:2025.07.17.665392. doi: 10.1101/2025.07.17.665392.
Mandibular bone development utilizes both endochondral ossification, forming from the cartilaginous anlage Meckel's cartilage derived from neural crest cells (NCC) and intramembranous ossification with direct differentiation of NCCs toward osteoblasts. Wnt/β-catenin signaling drives osteogenic vs chondrogenic differentiation and must be tightly controlled during the differentiation of osteochondroprogenitors. Chromatin remodelers add hierarchal regulation to the activation and repression of crucially timed gene regulatory networks and signaling cascades. In this study, we investigated the function of two chromatin remodelers-histone methyltransferases, PRDM3 and PRDM16 during murine craniofacial development. Conditionally ablating both and in the neural crest lineage using the Wnt1-Cre driver resulted in dramatic craniofacial phenotypes, including a severely hypoplastic mandible with complete absence of Meckel's cartilage at E18.5. Focusing on the Meckel's cartilage and mandibular bone phenotype, histological analysis demonstrated a significant increase in RUNX2+ osteoblast precursors, and loss of SOX9+ chondrogenic cells, suggesting an increase in osteoblast progenitors at the expense of chondrocytes that would otherwise form the Meckel's cartilage. This was not due to alterations in proliferation or apoptosis, as we observed no significant changes in the number of phosphoH3+ or cleaved caspase3+ cells in the mandibular process at E11.5, suggesting lack of NCC-derived chondrocytes is due to a change in NCC osteochondroprogenitor fate decisions. mRNA transcripts and protein abundance of Wnt/β-catenin signaling components were elevated in the mandibular process during initial NCC osteochondroprogenitor condensation events, suggesting PRDM3 and PRDM16 normally restrict expression of Wnt/β-catenin signaling components during NCC-derived osteochondroprogenitor differentiation to promote chondrogenesis and Meckel's cartilage formation. Taken together, PRDM3 and PRDM16 are required for NCC differentiation toward chondrocytes during Meckel's cartilage formation by controlling proper spatiotemporal Wnt/β-catenin transcriptional activity and this process is necessary for morphogenesis of the developing mandible.
下颌骨发育利用软骨内成骨，由源自神经嵴细胞（NCC）的软骨原基梅克尔软骨形成，以及膜内成骨，即NCC直接向成骨细胞分化。Wnt/β-连环蛋白信号传导驱动成骨与软骨生成分化，并且在骨软骨祖细胞分化过程中必须受到严格控制。染色质重塑因子为关键时期的基因调控网络和信号级联的激活与抑制增添了层次调节。在本研究中，我们调查了两种染色质重塑因子——组蛋白甲基转移酶PRDM3和PRDM16在小鼠颅面发育过程中的功能。使用Wnt1-Cre驱动程序在神经嵴谱系中条件性敲除PRDM3和PRDM16，导致了显著的颅面表型，包括在E18.5时严重发育不全的下颌骨，且完全没有梅克尔软骨。聚焦于梅克尔软骨和下颌骨表型，组织学分析显示RUNX2+成骨细胞前体显著增加，而SOX9+软骨生成细胞减少，这表明成骨祖细胞增加，而以原本会形成梅克尔软骨的软骨细胞为代价。这并非由于增殖或凋亡的改变，因为我们在E11.5时观察到下颌突中磷酸化组蛋白H3+或裂解的半胱天冬酶3+细胞数量没有显著变化，这表明缺乏NCC衍生的软骨细胞是由于NCC骨软骨祖细胞命运决定的改变。在初始NCC骨软骨祖细胞凝聚事件期间，下颌突中Wnt/β-连环蛋白信号成分的mRNA转录本和蛋白质丰度升高，这表明PRDM3和PRDM16通常在NCC衍生的骨软骨祖细胞分化过程中限制Wnt/β-连环蛋白信号成分的表达，以促进软骨生成和梅克尔软骨形成。综上所述，PRDM3和PRDM16通过控制适当的时空Wnt/β-连环蛋白转录活性，在梅克尔软骨形成过程中是NCC向软骨细胞分化所必需的，并且这一过程对于发育中的下颌骨的形态发生是必要的。
