DataSheet1_Cdon is essential for organ left-right patterning by regulating dorsal forerunner cells clustering and Kupffer’s vesicle morphogenesis.pdf

Cdon and boc are members of the cell adhesion molecule subfamily III Ig/fibronectin. Although they have been reported to be involved in muscle and neural development at late developmental stage, their early roles in embryonic development remain unknown. Here, we discovered that in zebrafish, cdon, but not boc, is expressed in dorsal forerunner cells (DFCs) and the epithelium of Kupffer’s vesicle (KV), suggesting a potential role for cdon in organ left-right (LR) patterning. Further data showed that liver and heart LR patterning were disrupted in cdon morphants and cdon mutants. Mechanistically, we found that loss of cdon function led to defect in DFCs clustering, reduced KV lumen, and defective cilia, resulting in randomized Nodal/spaw signaling and subsequent organ LR patterning defects. Additionally, predominant distribution of a cdon morpholino (MO) in DFCs caused defects in DFC clustering, KV morphogenesis, cilia number/length, Nodal/spaw signaling, and organ LR asymmetry, similar to those observed in cdon morphants and cdon−/− embryos, indicating a cell-autonomous role for cdon in regulating KV formation during LR patterning. In conclusion, our data demonstrate that during gastrulation and early somitogenesis, cdon is essential for proper DFC clustering, KV formation, and normal cilia, thereby playing a critical role in establishing organ LR asymmetry.

Cdon与boc均属于免疫球蛋白（Ig）/纤连蛋白III型亚家族细胞黏附分子（cell adhesion molecule subfamily III Ig/fibronectin）。既往研究表明二者可参与发育后期的肌肉与神经发育过程，但其在胚胎发育早期的功能仍未明确。本研究在斑马鱼（zebrafish）中发现，cdon而非boc可在背侧前驱细胞（dorsal forerunner cells, DFCs）以及库普弗囊泡（Kupffer’s vesicle, KV）的上皮组织中表达，提示cdon可能在器官左右（LR）模式形成中发挥潜在作用。进一步实验数据显示，cdon吗啉代敲低胚胎与cdon突变体的肝脏与心脏左右模式形成均出现紊乱。机制研究表明，cdon功能缺失会导致背侧前驱细胞聚集异常、库普弗囊泡腔室缩小以及纤毛结构缺陷，进而引发Nodal/Spaw信号通路随机化，最终造成器官左右模式形成缺陷。此外，靶向背侧前驱细胞的cdon吗啉代寡核苷酸（morpholino, MO）可诱导背侧前驱细胞聚集异常、库普弗囊泡形态发生缺陷、纤毛数量与长度异常、Nodal/Spaw信号通路紊乱以及器官左右不对称缺陷，该表型与cdon吗啉代敲低胚胎及cdon纯合突变（cdon−/−）胚胎的表型一致，证实cdon在调控左右模式形成过程中的库普弗囊泡形成时发挥细胞自主性功能。综上，本研究结果证实，在原肠胚形成与早期体节发生期，cdon对于正常的背侧前驱细胞聚集、库普弗囊泡形成以及完整纤毛结构的维持至关重要，从而在建立器官左右不对称过程中发挥关键作用。