Lee J-M, Jung H, Tang Q, Li L, Lee S-K, Lee J W, Park Y, Kwon H-J E
Department of Oral Biology, School of Dental Medicine, University at Buffalo, The State University of New York, Buffalo, NY, USA.
Department of Biological Sciences, College of Arts and Sciences, FOXG1 Research Center, University at Buffalo, The State University of New York, Buffalo, NY, USA.
J Dent Res. 2025 Mar 18:220345251320922. doi: 10.1177/00220345251320922.
Amelogenesis, the process of enamel formation, is tightly regulated and essential for producing the tooth enamel that protects teeth from decay and wear. Disruptions in amelogenesis can result in amelogenesis imperfecta, a group of genetic conditions characterized by defective enamel, including enamel hypoplasia, marked by thin or underdeveloped enamel. Mutations in the () gene, which encodes histone H3 lysine 4 methyltransferase, are associated with Kabuki syndrome, a developmental disorder that can involve dental anomalies such as enamel hypoplasia. However, the specific role of KMT2D in amelogenesis remains poorly understood. To address this gap, we generated a conditional knockout (cKO) mouse model with ectoderm-specific deletion of (, or -cKO) and characterized the resulting enamel defects using gross, radiographic, histologic, cellular, and molecular analyses. Micro-computed tomography and scanning electron microscopy revealed that adult -cKO mice exhibited 100% penetrant amelogenesis imperfecta, characterized by hypoplastic and hypomineralized enamel, partially phenocopying human Kabuki syndrome. Additionally, -cKO neonates developed molar tooth germs with subtle cusp shape alterations and mild delays in ameloblast differentiation at birth. RNA sequencing analysis of the first molar tooth germ at birth revealed that 33.7% of known amelogenesis-related genes were significantly downregulated in the -cKO teeth. Integration with KMT2D CUT&RUN sequencing results identified 8 overlapping genes directly targeted by KMT2D. Reanalysis of a single-cell RNA sequencing data set in the developing mouse incisors revealed distinct roles for these genes in KMT2D-regulated differentiation across various cell subtypes within the dental epithelium. Among these genes, and are likely direct targets involved in the differentiation of preameloblasts into ameloblasts. Taken together, we propose that KMT2D plays a crucial role in amelogenesis by directly activating key genes involved in ameloblast differentiation, offering insights into the molecular basis of enamel development and related dental pathologies.
釉质形成是牙釉质形成的过程，受到严格调控，对于产生保护牙齿免受龋齿和磨损的牙釉质至关重要。釉质形成过程的中断会导致釉质发育不全，这是一组以牙釉质缺陷为特征的遗传疾病，包括釉质发育不全，其特征是牙釉质薄或发育不全。编码组蛋白H3赖氨酸4甲基转移酶的（）基因突变与歌舞伎综合征有关，这是一种发育障碍，可能涉及牙釉质发育不全等牙齿异常。然而，KMT2D在釉质形成中的具体作用仍知之甚少。为了填补这一空白，我们构建了一个条件性敲除（cKO）小鼠模型，在外胚层特异性缺失（，或-cKO），并使用大体、影像学、组织学、细胞和分子分析对由此产生的牙釉质缺陷进行了表征。显微计算机断层扫描和扫描电子显微镜显示，成年-cKO小鼠表现出100%的釉质发育不全，其特征是牙釉质发育不全和矿化不足，部分模拟了人类歌舞伎综合征。此外，-cKO新生小鼠的磨牙牙胚在出生时出现了微妙的牙尖形状改变和成釉细胞分化轻度延迟。对出生时第一磨牙牙胚的RNA测序分析表明，在-cKO牙齿中，33.7%的已知釉质形成相关基因显著下调。与KMT2D CUT&RUN测序结果整合，鉴定出8个被KMT2D直接靶向的重叠基因。对发育中的小鼠切牙单细胞RNA测序数据集的重新分析揭示了这些基因在牙上皮内各种细胞亚型的KMT2D调控分化中的不同作用。在这些基因中，和可能是参与成釉细胞前体细胞分化为成釉细胞的直接靶点。综上所述，我们认为KMT2D通过直接激活参与成釉细胞分化的关键基因在釉质形成中起关键作用，为牙釉质发育和相关牙齿病理的分子基础提供了见解。
