Identification of TEKTIN1‐expressing multiciliated cells during spontaneous differentiation of non‐human primate embryonic stem cells

Tektins are a group of microtubule‐stabilizing proteins necessary for cilia and flagella assembly. TEKTIN1 (TEKT1) is used as a sperm marker for monitoring germ cell differentiation in embryonic stem (ES) and induced pluripotent stem (iPS) cells. Although upregulation of TEKT1 has been reported during spontaneous differentiation of ES and iPS cells, it is unclear which cells express TEKT1. To identify TEKT1‐expressing cells, we established an ES cell line derived from cynomolgus monkeys (Macaca fascicularis), which expresses Venus controlled by the TEKT1 promoter. Venus expression was detected at 5 weeks of differentiation on the surface of the embryoid body (EB), and it gradually increased with the concomitant formation of a leash‐like structure at the EB periphery. Motile cilia were observed on the surface of the Venus‐positive leash‐like structure after 8 weeks of differentiation. The expression of cilia markers as well as TEKT1–5 and 9 + 2 microtubule structures, which are characteristic of motile cilia, were detected in Venus‐positive cells. These results demonstrated that TEKT1‐expressing cells are multiciliated epithelial‐like cells that form a leash‐like structure during the spontaneous differentiation of ES and iPS cells. These findings will provide a new research strategy for studying cilia biology, including ciliogenesis and ciliopathies. We identified TEKT1‐expressing cells using monkey ES cell line, which expresses Venus controlled by the TEKT1 promoter. Venus‐positive cells spontaneously formed a leash‐like structure and many motile cilia were observed on the surface. These findings will provide a new research strategy for studying cilia biology, including ciliogenesis and ciliopathies.