Fig. 4

Zebrafish TJP expression pattern during the end of somitogenesis. Expression of tjp1.1 (A,F,K), tjp1.2 (B,G,L), tjp2.1 (C,H,M), tjp2.2 (D,I,N) and tjp3 (E,J,O) was detected by whole mount in situ hybridization of embryos at the 18 somite stage (18 hpf) (A–E) and the Prim-5 stage (24 hpf) (F–O). Towards the end of somitogenesis, all TJP genes are expressed in six major domains, including the epidermis, somites, pronephric ducts (A–J) as well as the neural tube, eyes, and otic placodes (asterisk) (K–O). However, there is a selective expression pattern in the posterior part of the embryo, where tjp1.1 is expressed transiently in the hypochord (A, arrow), the blood island (A,F, arrowhead) and the notochord (A,F, open arrowhead). As observed during early somitogenesis, tjp1.2 is expressed both in the notochord (B, G, open arrowheads) as well as in the somites (B,G). Interestingly, the posterior part of the ventral spinal cord is transiently positive for tjp2.1 (C,H, arrowhead). Tjp3 expression is high in the pronephric ducts (E, arrow) and weak in the epidermis (E, arrowheads).