Calmodulin genes in zebrafish (revisited).

Calmodulin (CaM), a ubiquitous protein, ancestral in early eukaryotes, regulates a large number of physiologically important functions by activating other proteins, some of them enzymes, usually in response to changes in the local concentration of calcium ions. Invertebrates possess one gene that codes for CaM. Among vertebrates, mammals display three genes that code for a 100% identical CaM molecule, while for zebra fishes etc., a non-mammalian vertebrate, we reported earlier the existence of four such genes. The number of multiple genes coding for a 100% identical CaM molecule present in the zebra fish genome, however, is corrected here, from the four, as previously suggested, to six (alpha, alpha2, beta, beta2, gamma and gamma 2). Identification of each of these genes is readily achieved upon examination of the characteristic 5' and 3' UTRs within their respective mRNAs even though we do not know at present what role these UTRs might play. A scanning of the 3' UTRs for short homology elements among the six genes (and a comparison with the human type I, II, and III CaM 3' UTRs) also suggests that duplication processes for three genes resulted in the formation of six such genes. As they become available, the promoter regions for these six genes should be scanned for possible identification of putative regulatory elements if we are to understand the need for the uniquely rigid evolutionary maintenance of these six genes. A comparison of the promoter regions for the beta and beta 2 genes is presented in this paper. A few common short homologous elements appear to be retained in these generally highly variant two regions, but conclusions about differential expression controls must be delayed until the promoter regions for all the other CaM genes have been examined.