Complex sentence: Semaphorin-Neuropilin repulsive signaling works synergistically with the forward EphB signaling to guide neural crest cells down the rostral half of somites in mice; in chick embryos, semaphorin acts in the cephalic region to guide neural crest cells through the pharyngeal arches.
Split into simpler sentences: Semaphorin-neuropilin repulsive signaling works synergistically with EphB signaling to guide neural crest cells down the rostral half of somites in mice. In chick embryos, semaphorin acts in the cephalic region to guide neural crest cells through the pharyngeal arches.