Molecular determinants of nephron vascular specialization in the kidney

The kidney vasculature is specialized to filter waste products from the blood, regulate blood pressure, and balance electrolytes. Although recent advances in stem cell studies have enabled the partial generation of kidney tissues in vitro, recapitulating the complex vascular structures of the kidney remains a daunting task. The molecular pathways that specify and sustain kidney vascular heterogeneity to perform these diverse tasks are not well characterized. Here, we have employed high throughput bulk and single-cell RNA sequencing of the non-lymphatic vasculature of the kidney to uncover the progression of pathways that dictate the developmental transition of nephrogenesis and vascular zonation from embryos to adulthood. We show that glomeruli and its associated vessels, manifest vascular-specific signatures expressing defined transcription factors, ion channels, solute transporters, and paracrine factors choreographing kidney functions. Notably, the ontology of the glomerulus coincides with induction of several unique transcription factors, including Tbx3, Gata5, Prdm1, and Pbx1. Selective deletion of Tbx3 in endothelial cells result in glomerular hypoplasia, microaneurysms and regressed fenestrations leading to fibrosis. Unraveling the molecular determinants of kidney vascular signatures will lay the foundation for rebuilding nephrons and understanding the pathogenesis of kidney diseases. Expression profiling by high throughput sequencing data of transgenic Tbx3 mutant mice, transduced HUVEC cell lines, and human kidney ECs; GPL21103 Illumina HiSeq 4000 (Mus musculus); GPL20301 Illumina HiSeq 4000 (Homo sapiens).肾脏血管系统具备独特的功能特化属性，能够过滤血液中的代谢废物、调节血压并维持电解质稳态。尽管近年来干细胞研究的进展使得体外部分重建肾脏组织成为可能，但重现肾脏复杂的血管结构仍是一项极具挑战性的任务。目前，对于界定并维持肾脏血管异质性以执行上述多样功能的分子通路，尚缺乏充分的特征解析。本研究针对肾脏非淋巴血管开展高通量批量转录组测序与单细胞RNA测序（single-cell RNA sequencing），以揭示调控胚胎发育至成年阶段肾发生与血管分区的分子通路动态变化。研究发现，肾小球及其关联血管呈现血管特异性的分子特征，表达特定的转录因子、离子通道、溶质转运蛋白以及协调肾脏功能的旁分泌因子。值得注意的是，肾小球的发育谱系与多个独特转录因子的诱导表达相契合，其中包括Tbx3、Gata5、Prdm1与Pbx1。在内皮细胞中选择性敲除Tbx3，会导致肾小球发育不全、微动脉瘤形成以及窗孔结构退化，最终引发纤维化。解析肾脏血管特征的分子决定因素，将为重建肾单位以及阐明肾脏疾病的发病机制奠定重要基础。本研究的表达谱测序数据来源于转基因Tbx3突变小鼠、转导的人脐静脉内皮细胞（HUVEC, Human Umbilical Vein Endothelial Cells）系以及人类肾脏内皮细胞（ECs, Endothelial Cells）；所用测序平台包括GPL21103 Illumina HiSeq 4000（小家鼠，Mus musculus）与GPL20301 Illumina HiSeq 4000（智人，Homo sapiens）。