Single cell RNA sequencing reveals differential cell cycle activity in key cell populations during nephrogenesis

The kidney is a complex organ composed of more than 30 terminally differentiated cell types that all are required to perform its numerous homeostatic functions. Defects in kidney development are a significant cause of chronic kidney disease in children, which can lead to kidney failure that can only be treated by transplant or dialysis. A better understanding of molecular mechanisms that drive kidney development is important for designing strategies to enhance renal repair and regeneration. In this study, we profiled gene expression in the developing mouse kidney at embryonic day 14.5 at single cell resolution. Consistent with previous studies, clusters with distinct transcriptional signatures clearly identify major compartments and cell types of the developing kidney. Cell cycle activity distinguishes between the "primed" and "self-renewing" sub-populations of nephron progenitors, with increased expression of the cell cycle related genes Birc5, Cdca3, Smc2 and Smc4 in "primed" nephron progenitors. Augmented Birc5 expression was also detected in immature distal tubules and a sub-set of ureteric bud cells, suggesting that Birc5 might be a novel key molecule required for early events of nephron patterning and tubular fusion between the distal nephron and the collecting duct epithelia. Single cell RNA sequencing pooled cells from two kidneys from a single E14.5 female mouse CD1 embryo.肾脏是一种复杂器官，由超过30种终末分化细胞类型构成，所有细胞类型均需协同执行肾脏的多项稳态功能。肾脏发育缺陷是儿童慢性肾脏病的重要致病诱因，该疾病可进展为肾衰竭，仅能通过肾移植或透析进行治疗。深入解析驱动肾脏发育的分子机制，对于研发优化肾脏修复与再生的治疗策略具有重要价值。本研究针对胚胎发育第14.5天（E14.5）的小鼠肾脏，以单细胞分辨率开展基因表达谱分析。与既往研究结果一致，具有独特转录特征的细胞簇可清晰鉴定出发育中肾脏的主要结构区域与细胞类型。细胞周期活性可区分肾单位祖细胞（nephron progenitors）的“预激活（primed）”与“自我更新（self-renewing）”亚群，其中“预激活”肾单位祖细胞内，细胞周期相关基因Birc5、Cdca3、Smc2及Smc4的表达水平显著升高。此外，在未成熟远端小管与部分输尿管芽细胞（ureteric bud cells）亚群中，同样检测到Birc5表达的上调，这提示Birc5可能是介导肾单位模式构建早期事件，以及远端肾单位与集合管上皮细胞（collecting duct epithelia）管状融合过程的新型关键分子。本研究采用单细胞RNA测序（single cell RNA sequencing）技术，对单只CD1品系雌性E14.5小鼠胚胎的双侧肾脏混合细胞进行了分析。