Nephronectin（NPNT）是一种基底膜（BM）蛋白，具有很高的与整合素a8b1亲和性，是小鼠肾形态发生所必需的。在肺部，NPNT也定位于BM上，但其在肺部发育中的潜在作用尚未得到研究。利用携带Floxed Npnt等位基因的小鼠进行全局敲除（KO）。通过杂交异质子的定时配对获得不同的胚胎发育时期，并分离肺进行分析。尽管KO胚胎的原始和次要肺芽形成正常，但右肺叶的融合，尤其是中央和尾部的融合，首次于E13.5检测到，并持续到成年。KO小鼠的肺实质与野生型（WT）相似，而叶叶融合不会改变成年KO小鼠的呼吸力学。对胚胎和成年小鼠肺部现有的单细胞RNA-seq图谱进行研究，发现Npnt转录本在E12.5时期的中皮细胞中出现，并延续到早期新生儿期，但在成年肺中没有发现。KO胚胎的肺部表现出laminin a5的表达增加和胚胎期BM中胶原IV的沉积增加，伴随着邻近基质中胶原纤维的异常。从KO胚胎肺中提取的头部和辅助叶在体外培养的时候会融合，融合区域显示出儿茶酚胶原瘤1（Wilms tumor 1）的中皮标记缺失。由于以前在整合素a8 KO胚胎中观察到了类似的叶融合模式，我们的研究结果表明，NPNT通过整合素a8信号传递，可能在内脏胸膜中维持右肺叶在胚胎发育期间的分离状态。

Nephronectin (NPNT) is a basement membrane (BM) protein and high-affinity ligand of integrin a8b1 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 Npnt 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 E13.5 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 Npnt transcripts in mesothelial cells at E12.5 and into the early postnatal period, but not in adult lungs. KO embryonic lungs exhibited increased expression of laminin a5 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 a8 KO embryos, our results suggest that NPNT signaling through integrin a8, likely in the visceral pleura, maintains right lung lobe separation during embryogenesis.