Structure of the zebrafish fasciclin I-related extracellular matrix protein (betaig-h3) and its characteristic...

betaig-h3, which is structurally related to the insect fasciclin I, is assumed to act as a cell adhesion molecule through binding to cell-surface integrins. In this study, we obtained cDNA clones for the zebrafish orthologue of betaig-h3 and examined the expression of the gene (betaig-h3) in zebrafish embryos using in situ hybridization. Expression is first seen at the bud stage in the presomitic mesoderm. Throughout the somitogenesis stage, betaig-h3 is expressed in all the segmented somites, as well as in the presomitic mesoderm (S0 and S-I). High expression is observed in the dorsolateral part of the somite until the mid-somitogenesis stage. At late somitogenesis stages, the betaig-h3 expression in the dorsolateral somite fades away, while expression is upregulated in the ventromedial part of the somite that corresponds to the sclerotome. In embryos after completion of somitogenesis and fry after hatching, betaig-h3 continues to be expressed in the sclerotome. In addition, new expression starts in the mesenchyme cells in the head, pharyngeal arches, and pectoral fins. In the embryonic brain, expression is observed along the anterior and postoptic commissures, as well as along the optic nerve.