Department of Biology, Faculty of Science, The University of Western Ontario, 1151 Richmond St., London, ON N6A 5C1, Canada.
Department of Anatomy & Cell Biology, Schulich School of Medicine and Dentistry, The University of Western Ontario, 1151 Richmond St., London, ON N6A 5C1, Canada.
Bone. 2020 Jul;136:115365. doi: 10.1016/j.bone.2020.115365. Epub 2020 Apr 19.
Oculodentodigital dysplasia (ODDD) is a disease caused by mutations in the GJA1 gene that encodes the gap-junctional protein connexin43 (Cx43). ODDD affects multiple organs, but craniofacial anomalies are typical. However, details on the timing of phenotypic presentation of these abnormalities and their correspondence with potential cellular changes are incomplete. Here, we perform the first assessment of the development of the ODDD craniofacial phenotype in the Cx43 mouse model and show that the phenotypic features commonly found in patients with the disorder arise in mice between E17.5 and birth and become more profound with age. Using mice heterozygous for the I130T mutation of Gja1, we provide a detailed analysis of the craniofacial phenotype in this ODDD model using shape analyses based on micro-CT images. Results show that in addition to differences in facial bone morphology, there are significant shape differences in the cranial base. Mutant mice display delayed ossification at E17.5 and birth, particularly in bones of the face and cranial vault but ossification is normal at three months. Our immunohistochemical analyses of the palatine bone indicate that osteoblast differentiation is delayed in Cx43 mice compared to their wildtype littermates, which likely contributes to the phenotypic variations observed in the facial bones. Our histological and immunohistochemical analyses of the synchondroses of the cranial base show no differences in molecular indicators of chondrocyte differentiation in mutant mice, suggesting that the differences to cranial base morphology displayed by Cx43 mice are not due to differences in chondrocyte proliferation or differentiation. Together, our findings suggest that Cx43 mice represent a surrogate model to not only inform about the craniofacial anomalies found in ODDD patients but also to show that reduced Cx43 function leads to phenotypic changes that are largely due to osteoblast defects.
眼牙指发育不良症（ODDD）是由 GJA1 基因突变引起的疾病，该基因编码间隙连接蛋白connexin43（Cx43）。ODDD 影响多个器官，但颅面异常是典型的。然而，关于这些异常表型出现的时间以及它们与潜在细胞变化的对应关系的细节尚不完全清楚。在这里，我们首次评估了 Cx43 小鼠模型中 ODDD 颅面表型的发育情况，并表明该疾病患者中常见的表型特征出现在 E17.5 至出生期间的小鼠中，并随着年龄的增长而变得更加明显。我们使用 Gja1 基因 I130T 突变的杂合子小鼠，通过基于微 CT 图像的形状分析，对该 ODDD 模型的颅面表型进行了详细分析。结果表明，除了面部骨形态的差异外，颅底也存在显著的形状差异。突变小鼠在 E17.5 和出生时表现出骨化延迟，特别是在面部和颅盖骨，但在三个月时骨化正常。我们对腭骨的免疫组织化学分析表明，与野生型同窝仔鼠相比，Cx43 小鼠中的成骨细胞分化延迟，这可能导致面部骨骼中观察到的表型变异。我们对颅底骺软骨的组织学和免疫组织化学分析显示，突变小鼠中软骨细胞分化的分子标志物没有差异，这表明 Cx43 小鼠颅底形态的差异不是由于软骨细胞增殖或分化的差异所致。综上所述，我们的研究结果表明，Cx43 小鼠不仅可以作为一种替代模型，用于了解 ODDD 患者的颅面异常，还可以表明 Cx43 功能降低导致的表型变化主要是由于成骨细胞缺陷所致。
