Department of Cell Biology and Anatomy, Alberta Children's Hospital Research Institute and McCaig Institute for Bone and Joint Health, University of Calgary, Calgary, Alberta, Canada.
Faculty of Dentistry, University of British Columbia, Vancouver, British Columbia, Canada.
Dev Dyn. 2019 Dec;248(12):1232-1242. doi: 10.1002/dvdy.110. Epub 2019 Sep 14.
Cleft lip and palate is one of the most common human birth defects, but the underlying etiology is poorly understood. The A/WySn mouse is a spontaneously occurring model of multigenic clefting in which 20% to 30% of individuals develop an orofacial cleft. Recent work has shown altered methylation at a specific retrotransposon insertion downstream of the Wnt9b locus in clefting animals, which results in decreased Wnt9b expression.
Using a newly developed protocol that allows us to measure morphology, gene expression, and DNA methylation in the same embryo, we relate gene expression in an individual embryo directly to its three-dimensional morphology for the first time. We find that methylation at the retrotransposon relates to Wnt9b expression and morphology. IAP methylation relates to shape of the nasal process in a manner consistent with clefting. Embryos with low IAP methylation exhibit increased among-individual variance in facial shape.
Methylation and gene expression relate nonlinearly to nasal process morphology. Individuals at one end of a continuum of phenotypic states display a clinical phenotype and increased phenotypic variation. Variable penetrance and expressivity in this model is likely determined both by among-individual variation in methylation and changes in phenotypic robustness along the underlying liability distribution for orofacial clefting.
唇腭裂是最常见的人类出生缺陷之一，但发病机制尚不清楚。A/WySn 鼠是一种自发性多基因腭裂模型，其中 20%至 30%的个体发生口腔腭裂。最近的研究表明，在腭裂动物中，Wnt9b 基因座下游的特定逆转录转座子插入处的甲基化发生改变，导致 Wnt9b 表达减少。
我们使用一种新开发的方案，可以在同一个胚胎中测量形态、基因表达和 DNA 甲基化，这是我们首次将个体胚胎的基因表达与其三维形态直接相关联。我们发现逆转录转座子的甲基化与 Wnt9b 的表达和形态有关。IAP 甲基化与鼻突的形状有关，与腭裂的方式一致。IAP 甲基化水平低的胚胎在面部形状上表现出个体间变异性增加。
甲基化和基因表达与鼻突形态呈非线性相关。在表型状态连续体的一端的个体表现出临床表型和增加的表型变异性。在该模型中，可变外显率和表现度可能既取决于个体间甲基化的变化，也取决于口腔腭裂潜在易感性分布中表型稳健性的变化。
