title: The evolutionary relationship of the transcriptionally active fabp11a (intronless) and fabp11b genes of medaka with fabp11 genes of other teleost fishes.
abstract: Here we describe the structure of the fatty acid-binding protein 11a and 11b genes (fabp11a and fabp11b) in medaka, and their evolutionary relationship to fabp11 genes from other teleost fishes. Initial studies indicated that the medaka fabp11a gene is intronless, but the fabp11b gene consists of four exons separated by three introns, a genomic organization that is characteristic of most members of the intracellular lipid-binding protein family. Based on genomic sequence, we conclude that the intronless fabp11a gene most likely arose as a result of reverse transcription of its mRNA transcript into cDNA followed by integration into chromosomal DNA. The ancestral intron-containing fabp11a gene was presumably lost from the medaka genome. The duplicated fabp11 genes extant in medaka encode polypeptides of 134 amino acids, which share highest sequence identity and similarity, and cluster in a distinct phylogenetic clade, with their orthologs in other teleost fishes. The fabp11a and fabp11b genes in medaka are therefore orthologs of the fabp11a and fabp11b genes, respectively, of other teleost fishes. No conserved gene synteny was found between medaka fabp11a and fabp11a genes from other teleost fishes, supporting our suggestion as to how this intronless gene arose. However, conserved gene synteny was evident between medaka fabp11b and fabp11b genes from other teleost fishes. The tissue-specific distribution of transcripts for medaka and zebrafish fabp11a and fabp11b genes revealed acquisition of a new function(s) in various tissues by the medaka fabp11b gene, which may explain the retention of sister duplicates of fabp11 in the medaka genome.
authors.affiliation: Department of Biology, Dalhousie University, Halifax, NS, Canada.
authors.forename: Manoj B
authors.initials: MB
authors.lastname: Parmar
authors.forename: Ananda B
authors.initials: AB
authors.lastname: Venkatachalam
authors.forename: Jonathan M
authors.initials: JM
authors.lastname: Wright
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D018076:DNA, Complementary / Q000235:genetics; D019143:Evolution, Molecular; D050556:Fatty Acid-Binding Proteins / Q000235:genetics*; D005399:Fishes / Q000235:genetics*; D023281:Genomics; D007438:Introns / Q000235:genetics; D008969:Molecular Sequence Data; D009928:Organ Specificity; D009990:Oryzias / Q000235:genetics*; D010802:Phylogeny; D012333:RNA, Messenger / Q000235:genetics; D060888:Real-Time Polymerase Chain Reaction; D020133:Reverse Transcriptase Polymerase Chain Reaction; D017386:Sequence Homology, Amino Acid; D026801:Synteny; D014158:Transcription, Genetic
chemical_list: D018076:DNA, Complementary; D050556:Fatty Acid-Binding Proteins; D012333:RNA, Messenger