Single-cell transcriptional analysis of lens placode development in Mab21l1 knockout mice

In mouse early organogenic stages, a Mab21l1-null mutation causes severe defects in invagination of the lens placode toward optic cup due to its severe defects in both cell proliferation and survival, which subsequently results in severe microphthalmia after birth. In human, loss of function variants in MAB21L1 have recently been described in Cerebello-Oculo-Facio-Genital syndrome (COFG syndrome). The close similarity between mouse and human phenotypes including microphthalmia indicates the importance of Mab21l1 function in human lens placode. To approach the molecular function of MAB21L1 in eye morphogenesis, we examined single cell transcriptomes in lens placode and its surrounding surface ectoderm at 26 somite stage (E9.25), just prior to the onset of lens defects in Mab21l1-null embryos. Here we demonstrate the identification of several key genes immediately downstream of Mab21l1 function, together with the early lens placode-/surface ectoderm-specific single cell transcriptomes during murine lens placode specification. Ocular area scRNA-seq profiles of 26 somite stages wild type (WT) and Mab21l1-null (KO) mice were generated using a 10× Chromium system.在小鼠早期器官发生阶段，Mab21l1无效突变（Mab21l1-null）会因细胞增殖与存活能力严重受损，导致晶状体基板向视杯内陷出现显著缺陷，最终使小鼠出生后出现严重小眼畸形。在人类中，近期研究报道MAB21L1功能缺失变异可引发小脑-眼-面-生殖器综合征（Cerebello-Oculo-Facio-Genital syndrome，简称COFG综合征）。小鼠与人类的表型（包括小眼畸形）高度相似，这提示Mab21l1在人类晶状体基板发育过程中发挥关键作用。为解析MAB21L1在眼形态发生中的分子功能，我们对26体节阶段（胚胎期9.25，E9.25）的晶状体基板及其周围表面外胚层的单细胞转录组进行了分析，该时间点恰好处于Mab21l1-null胚胎晶状体缺陷发作之前。本研究成功鉴定出数个直接受Mab21l1调控的关键下游基因，并获得了小鼠晶状体基板特化过程中早期晶状体基板/表面外胚层特异性的单细胞转录组数据。本研究利用10× Chromium系统，构建了26体节阶段野生型（wild type，简称WT）与Mab21l1-null（KO）小鼠的眼区单细胞RNA测序（single cell RNA-seq，简称scRNA-seq）谱式。