The intestine of zebrafish consists of mucosa, muscularis and serosa. Intestinal epithelial cells (IECs) act as a physical and biochemical barrier to protect against invasion by external commensal bacteria. Cell junction is one of the crucial basis of the barrier function. When cell junctions were disrupted, intestinal permeability would be naturally impeded. Extracellular signal-regulated kinase 5 (ERK5), belonging to the Mitogen-activated protein kinase (MAPK) family, is involved in the normal physiological development of the cardiovascular system and nervous system. But the role of erk5 in intestinal morphogenesis and intestinal function is yet to know. Here, we showed that knockout of the erk5 in zebrafish larvae resulted in intestinal wall hypoplasia, including the thinned intestinal wall, reduced intestinal folds, and disrupted cell junctions. In addition, the intestinal permeability assay demonstrated that knockout of erk5 resulted in increased intestinal permeability. All of these showed that erk5 plays an essential role in the maintenance of intestinal barrier function. Thus, our data indicate that erk5 is a critical effector in intestinal morphogenesis and intestinal function, and dysfunction of erk5 would lead to intestinal diseases.

斑马鱼的肠道由粘膜、肌层和浆膜组成。肠上皮细胞（IEC）充当物理和生化屏障，防止外部共生细菌的入侵。细胞连接是屏障功能的重要基础之一。当细胞连接被破坏时，肠道通透性自然就会受到阻碍。细胞外信号调节激酶5（ERK5）属于丝裂原激活蛋白激酶（MAPK）家族，参与心血管系统和神经系统的正常生理发育。但erk5在肠道形态发生和肠道功能中的作用尚不清楚。在这里，我们发现敲除斑马鱼幼虫中的erk5会导致肠壁发育不全，包括肠壁变薄、肠褶皱减少和细胞连接破坏。此外，肠道通透性测定表明，erk5敲除会导致肠道通透性增加。这些都表明erk5在维持肠道屏障功能中发挥着重要作用。因此，我们的数据表明erk5是肠道形态发生和肠道功能的关键效应子，erk5的功能障碍会导致肠道疾病。