Division of Allergy, Pulmonary, and Critical Care Medicine, Department of Medicine, University of Wisconsin, Madison, Wisconsin, United States.
Division of Pulmonary, Critical Care, and Sleep Medicine, Department of Medicine, University of Washington, Seattle, Washington, United States.
Am J Physiol Lung Cell Mol Physiol. 2023 Mar 1;324(3):L335-L344. doi: 10.1152/ajplung.00505.2021. Epub 2023 Jan 31.
Nephronectin (NPNT) is a basement membrane (BM) protein and high-affinity ligand of integrin α8β1 that is required for kidney morphogenesis in mice. In the lung, NPNT also localizes to BMs, but its potential role in pulmonary development has not been investigated. Mice with a floxed allele were used to generate global knockouts (KOs). Staged embryos were obtained by timed matings of heterozygotes and lungs were isolated for analysis. Although primary and secondary lung bud formation was normal in KO embryos, fusion of right lung lobes, primarily the medial and caudal, was first detected at and persisted into adulthood. The lung parenchyma of KO mice was indistinguishable from wild-type (WT) and lobe fusion did not alter respiratory mechanics in adult KO mice. Interrogation of an existing single-cell RNA-seq atlas of embryonic and adult mouse lungs identified transcripts in mesothelial cells at and into the early postnatal period, but not in adult lungs. KO embryonic lungs exhibited increased expression of laminin α5 and deposition of collagen IV in the mesothelial BM, accompanied by abnormalities in collagen fibrils in the adjacent stroma. Cranial and accessory lobes extracted from KO embryonic lungs fused ex vivo when cultured in juxtaposition, with the area of fusion showing loss of the mesothelial marker Wilms tumor 1. Because a similar pattern of lobe fusion was previously observed in integrin α8 KO embryos, our results suggest that NPNT signaling through integrin α8, likely in the visceral pleura, maintains right lung lobe separation during embryogenesis.
纤连蛋白（NPNT）是一种基底膜（BM）蛋白，是整合素 α8β1 的高亲和力配体，对于小鼠肾脏形态发生是必需的。在肺部，NPNT 也定位于 BM，但它在肺发育中的潜在作用尚未被研究。使用带有 floxed 等位基因的小鼠产生了全局敲除（KO）。通过杂合子的定时交配获得阶段胚胎，并分离肺进行分析。尽管 KO 胚胎中的初级和次级肺芽形成正常，但右肺叶（主要是内侧和尾侧）的融合最早在 时被检测到，并持续到成年。KO 小鼠的肺实质与野生型（WT）无异，并且叶融合不会改变成年 KO 小鼠的呼吸力学。对现有的胚胎和成年小鼠肺部单细胞 RNA-seq 图谱的分析鉴定了间皮细胞中的 个转录本在 时以及出生后的早期，但不在成年肺中。KO 胚胎肺中的层粘连蛋白 α5 的表达增加，并且在间皮 BM 中沉积了胶原 IV，同时相邻基质中的胶原纤维出现异常。从 KO 胚胎肺中提取的颅侧和副侧叶在体外培养时融合在一起，融合区域的间皮标志物 Wilms 肿瘤 1 丢失。因为以前在整合素 α8 KO 胚胎中观察到类似的叶融合模式，我们的结果表明 NPNT 通过整合素 α8 （可能在脏层胸膜）信号传导在胚胎发生过程中维持右肺叶分离。
