Schwann cells require dync1h1 function to express transcription factors necessary for myelination. sox10 expression is similar at the pLLn (arrowheads) in 52 hours post fertilization (hpf) wild-type (A) and dync1h1 (B) mutant embryos. Schwann cells associated with motor nerves (mn, asterisks) express erbb3b in both wild-type siblings (C) and dync1h1 mutant (D) embryos 52 hpf. Whereas 52 hpf wild-type embryos express pou3f1 at the pLLn (E), expression is absent or present in only a few cells in dync1h1 mutant embryos (F). At 72 hpf wild-type larva expresses egr2b at the pLLn (G), whereas comparably staged dync1h1 mutant larva expresses egr2b in few or no cells (H). Images show lateral views of whole embryos and larvae focused on the mid trunk, with anterior to the left and dorsal up. Scale bar equals 40 μm.