Epithelial tissues are fundamental for the establishment and maintenance of different body compartments in multicellular animals. To achieve this specific task epithelial sheets secrete an apical extracellular matrix for tissue strength and protection and they organize a transepithelial barrier function, which is mediated by tight junctions in vertebrates or septate junctions in invertebrates. Here, we show that the bicistronic gene würmchen is functionally expressed in epithelial tissues. CRISPR/Cas9-mediated mutations in both coding sequences reveal two essential polypeptides, Würmchen1 and Würmchen2, which are both necessary for normal epithelial tissue development. Würmchen1 represents a genuine septate junction core component. It is required during embryogenesis for septate junction organization, the establishment of a transepithelial barrier function, distinct cellular transport processes and tracheal system morphogenesis. Würmchen2 is localized in the apical membrane region of epithelial tissues and in a central core of the tracheal lumen during embryogenesis. It is essential during the later larval development.

中文翻译：

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双顺反子基因würmchen编码果蝇上皮发育的两个基本成分。

上皮组织对于在多细胞动物中建立和维持不同的体腔至关重要。为了完成这一特定任务，上皮细胞层分泌了顶端的细胞外基质以增强组织强度和保护细胞，并组织了跨上皮屏障功能，该功能由脊椎动物的紧密连接或无脊椎动物的分隔连接介导。在这里，我们显示双顺反子基因würmchen在上皮组织中功能性表达。CRISPR / Cas9介导的两个编码序列中的突变揭示了两种必需多肽，Würmchen1和Würmchen2，这对于正常的上皮组织发育都是必需的。Würmchen1代表真正的分隔连接核心组件。在胚胎发生过程中需要进行分隔连接组织，跨上皮屏障功能的建立，独特的细胞转运过程和气管系统形态发生。Würmchen2在胚胎发生过程中位于上皮组织的顶膜区域和气管腔的中央。这在后期的幼体发育过程中至关重要。