Isolation, characterization, and expression analysis of zebrafish large Mafs

Large Maf proteins, which are members of the basic leucine zipper (b-Zip) s uperfamily, are involved in the determination and control of cellular diffe rentiation. The expression patterns of various vertebrate large Maf mRNAs w ere described previously. Here, we report the cloning of a novel zebrafish large Maf cDNA, SMaf1 (Somite Maf1), and other zebrafish large Mafs, the N- terminus domains of which possess transactivational activity. We also analy zed the expression patterns of SMaf1 and SMaf2 (Somite Maf2)/Krml2 as well as MafB/Val and c-Maf during zebrafish embryogenesis, In particular, the ro bust expression of the novel SMaf1 mRNA, which overlapped that of MyoD, in semitic cells during somitogenesis was noteworthy. In addition, the express ion patterns of SMaf2 and MafB in the blood-forming regions, and those of c -Maf and MafB in the lens cells showed spatial redundancy, although the tem poral appearance of these genes at these sites differed. These data indicat e that SMafs may play important roles in somitogenesis, and that Maf protei ns may have overlapping and yet specific functions as to the determination and differentiation of cell lineages.