xCdc4α and xCdc4β protein are expressed throughout development, and transcripts accumulate in the neural crest and neural crest derived tissues. Expression of (A) xCdc4α and (B) xCdc4β in staged embryo lysates was determined by immunoblotting (IB) using anti-Cdc4 antibodies. In vitro translated (IVT) protein was used as a control. Equal loading was verified by IB for tubulin, with the equivalent of one embryo per lane loaded. (C-K) Developmental expression of xCdc4 was determined by whole mount ISH. At stage 15 (C), xCdc4 expression is detected broadly at the preplacodal ectoderm (ppe), in particular in the presumptive optic placode (pop) as well as in the prospective trunk neural crest (TNc). At late neurula stages (D,E), while xCdc4 transcripts continue accumulating in the trunk neural crest and optic placode (Opt P), xCdc4 is also detected in the cranial neural crest, particularly within the branchial aggregates (b). At stage 21 (F), xCdc4 is broadly detected in migrating cranial neural crest (Cc) and placodal regions. At stage 23 (G,H), xCdc4 is expressed in cranial neural crest that populates the branchial arches (Ba) and additionally in the myotome (My). At stage 26 (I), xCdc4 continues to be expressed in the myotome and branchial arches, as well as in several anterior placodes (arrowheads). xCdc4 is additionally expressed in the posterior fin mesenchyme (Fin). From stage 28 to 32 (J,K), xCdc4 expression is downregulated in the branchial arches, while persisting in the anterior placodal region (arrowheads), dorsal somites (s) and dorsal and ventral fin mesenchyme (Fin). Whole mount ISH at the indicated stages using xCdc4β sense probe confirms the specificity of the probe (L-N). Views in (C-N) are indicated bottom right after the stage (St): a, anterior view; d, dorsal view; l, lateral view.