Tandem duplication of the fabp1b gene and subsequent divergence of the tissue-specific distribution of fabp1b.1 and fabp1b.2 transcripts in zebrafish (Danio rerio).

We describe a fatty acid-binding protein 1 (fabp1b.2) gene and its tissue-specific expression in zebrafish embryos and adults. The 3.5 kb zebrafish fabp1b.2 gene is the paralog of the previously described zebrafish fabp1a and fabp1b genes. Using the LN54 radiation hybrid mapping panel, we assigned the zebrafish fabp1b.2 gene to linkage group 8, the same linkage group to which fabp1b.1 was mapped. fabp1b.1 and fabp1b.2 appear to have arisen by a tandem duplication event. Whole-mount in situ hybridization of a riboprobe to embryos and larvae detected fabp1b.2 transcripts in the diencephalon and as spots in the periphery of the yolk sac. In adult zebrafish, in situ hybridization revealed fabp1b.2 transcripts in the anterior intestine and skin, and reverse transcription PCR (RT-PCR) detected fabp1b.2 transcripts in the intestine, brain, heart, ovary, skin, and eye. By contrast, fabp1b.1 transcripts were detected by RT-PCR in the liver, intestine, heart, testis, ovary, and gills. The tissue-specific distribution of transcripts for the tandemly duplicated fabp1b.1 and fabp1b.2 genes in adult tissues and during development suggests that the duplicated fabp1b genes of zebrafish have acquired additional functions compared with the ancestral fabp1 gene, i.e., by neofunctionalization. Furthermore, these functions were subsequently divided between fabp1b.1 and fabp1b.2 owing to subfunctionalization.