Characterization of two frizzled8 homologues expressed in the embryonic shield and prechordal plate of zebrafish embryos1The entire nucleotide sequences for Zfz8a and Zfz8b cDNA were deposited to the GenBank database under the Accession numbers AF060697 and AF060696, respectively.1

Abstract

We have isolated and characterized two complete cDNA clones, Zfz8a and Zfz8b, which encode zebrafish Frizzled (Fz) homologues. The predicted protein sequences, spanning 579 and 576 amino acid residues for ZFz8a and ZFz8b, respectively, were highly homologous (78%) to each other and contained an extracellular cysteine-rich domain and seven transmembrane domains that are well conserved in Fz receptor protein members. In comparison with other Fz family members, ZFz8a and ZFz8b showed the highest homology with mouse Fz8 (MFz8), sharing 84 and 76% amino acid identity, respectively. The presence of Zfz8a and Zfz8b transcripts was detected by in situ hybridization in zebrafish embryos from the 512 cell stage, and their appearance in the future dorsal region could be observed before embryos reached the 30% epiboly stage. At shield stage, Zfz8a transcripts were expressed in both epiblast and shield whereas expression of Zfz8b was only detected in the embryonic shield. During gastrula stages, both Zfz8a and Zfz8b transcripts were found in anterior dorsal regions of the involuting mesendoderm (future prechordal plate). By the 2- to 3-somite stage, expression of both Zfz8a and Zfz8b was restricted to the prechordal plate and prospective anterior neurectoderm, although expression of the Zfz8a gene was no longer present in the most anterior portion of the prechordal plate, the polster. In one-eyed pinhead mutant embryos, which lack prechordal plate, both Zfz8a and Zfz8b transcripts were reduced, confirming the prechordal plate specificity of Zfz8a and Zfz8b gene expression. These results provide an additional evidence supporting the role of Wnt signaling in organizer-mediated axial patterning.

Csrp1 regulates dynamic cell movements of the mesendoderm and cardiac mesoderm through interactions with Dishevelled and Diversin

“…Another marker, fzd8b, is expressed in a restricted portion of the ventral telencephalon at 14 hpf in the WT (Fig. 2F) (21). Similar to borders demarcated by other markers, the morphants display expanded and dispersed fzd8b expression in lateral and posterior regions of the telencephalon (red arrowheads in Fig.…”

Neurodevelopment Genes in Lampreys Reveal Trends for Forebrain Evolution in Craniates

“…Although the frizzled members in mouse [51] or zebrafish (ZFIN database) show less spectacular and more widespread patterns than those found here in lamprey embryos, they were reported absent from the Wnt-secreting, zli region (see summary figure). Likewise, the zebrafish prechordal plate also expresses Frizzled receptors [52]. In summary, these similarities suggest that the main source of Wnt ligand in the zli signals through Frizzled receptors both anteriorly and posteriorly in the diencephalon, in the lamprey as in other vertebrates.…”

Early Stages of Zebrafish Eye Formation Require the Coordinated Activity of Wnt11, Fz5, and the Wnt/β-Catenin Pathway

“…Nevertheless, we reasoned that looking for genetic interactions between ligands and receptors would be a good way to identify likely in vivo interactions. The only Fz gene with characterized expression in the ANP during late stages of gastrulation is fz8a (Kim et al, 1998; Kim et al, 2002); to analyze fz8a function, we abrogated its activity by injection of antisense morpholinos (Mo) (Nasevicius and Ekker, 2000).…”