Schwann cells wrap motor axons but delay mbp expression in the absence of pard3 function. A,B: Representative images of control pard3fh305/+ (A) and MZpard3fh305 mutant (B) embryos, focused on a single motor root. Schwann cells are marked by sox10:memRFP (red) and motor axons are marked by mnx1:GFP (green). Schwann cells ensheath motor axons similarly in both control and mutant. Boxes show orthogonal views of motor nerves at the level of the dashed line. Arrows indicate ensheathed motor axons. C-J: Representative images of mbp RNA expression in wild-type and MZpard3fh305 mutant larvae. Views are from lateral of the trunk with anterior to the left and dorsal up. At 4 dpf, mbp expression is evident at motor nerves (mn, asterisks) (C) and the posterior lateral line nerve (pLLn) (D) of a wild-type larva. By contrast, no motor nerve expression is evident at motor nerves of a MZpard3fh305 mutant larva (E) although pLLn expression appears normal (F). At 4.5 dpf, mbp expression is similar in wild-type and MZpard3fh305 mutant larvae at both motor nerves and the pLLn (G-J). Scale bar = 15 µM in A,B; 100 µM in C-J.