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Abstract
In mammals, multiple genes encode for calmodulin (CaM), a calcium-binding protein that is involved in numerous cellular pathways regulating signal transduction and cell division. Six CaM genes designated α-CaM, α2-CaM, β-CaM, β2-CaM, γ-CaM, and γ2-CaM are expressed by the zebrafish genome. The spatiotemporal expression patterns of the mRNA transcripts for these genes were investigated during zebrafish embryogenesis and in the adult zebrafish brain. Bioinformatic analyses suggest that all six zebrafish CaM genes diverged from a common ancestral gene. The genomic structure, exon size, and amino acid sequence for each distinct zebrafish CaM gene is evolutionarily conserved, as is true for other vertebrates. During embryonic development, zebrafish CaM genes appear particularly important to the temporal and spatial development of the nervous system. The genes for CaM demonstrate a wide range of spatial expression with frequent overlapping in gene expression. However, α2-CaM and γ-CaM were uniquely expressed in the otic vesicle and somites, respectively. These data suggest that, unlike the fate of many duplicate genes that arise during evolution, the zebrafish CaM genes appear to maintain primarily overlapping functions with some limited subfunctionalization. Multiple CaM genes producing identical proteins both spatially and temporally may have been preserved in vertebrates to provide an essential supply of CaM necessary for sustaining protein-protein interactions associated with the broad and diverse spectrum of calmodulin targets, particularly during the orchestration of embryogenesis. Utilizing the zebrafish model, this study provides a valuable foundation for future functional studies that elucidate the developmental role of CaM genes in vertebrates.
