The paired-type homeodomain transcription factor Uncx is involved in multiple processes of embryogenesis in vertebrates. Reasoning that zebrafish genes uncx4.1 and uncx are orthologs of mouse Uncx, we studied their genomic environment and developmental expression. Evolutionary analyses indicate the zebrafish uncx genes as being paralogs deriving from teleost-specific whole-genome duplication. Whole-mount in situ mRNA hybridization of uncx transcripts in zebrafish embryos reveals novel expression domains, confirms those previously known, and suggests sub-functionalization of paralogs. Using genetic mutants and pharmacological inhibitors, we investigate the role of signaling pathways on the expression of zebrafish uncx genes in developing somites. In identifying putative functional role(s) of zebrafish uncx genes, we hypothesized that they encode transcription factors that coordinate growth and innervation of somitic muscles.
Keywords: AP, antero-posterior; Ace, acerebellar; CAMP, conserved ancestral microsyntenic pairs; CNE, conserved non-coding elements; CRM, cis-regulatory module; CS, Corpuscle of Stannius; CaP, caudal primary motor neuron axons; Ce, cerebellum; Development; Di, diencephalon; Elfn1, Extracellular Leucine Rich Repeat And Fibronectin Type III Domain Containing 1; Ey, eye; FB, forebrain; FGF, fibroblast growth factor; Flh, floating head; HB, hindbrain; HM, hybridization mix; Hy, hypothalamus; MO, morpholino; Mical, molecule interacting with CasL; No, notochord; OP, olfactory placode; OT, optic tectum; PA, pharyngeal arches; PSM, presomitic mesoderm; SC, spinal cord; Shh, sonic hedgehog; Signaling pathway; So, somites; Synteny; TSGD; TSGD, teleost-specific genome duplication; Te, telencephalon; Th, thalamus; Uncx; VLP, ventro-lateral-posterior; WIHC, whole-mount immunohistochemistry; WISH, whole-mount in situ hybridization; YE, yolk extension; Yo, yolk; Zebrafish; cyc, cyclops; fss, fused-somites; hpf, hours post fertilization; ptc, patched; smu, slow-muscle-omitted; syu, sonic-you; yot, you-too.