Retention of the duplicated cellular retinoic acid-binding protein 1 genes (crabp1a and crabp1b) in the zebrafish genome by subfunctionalization of tissue-specific expression.
The cellular retinoic acid-binding protein type I (CRABPI) is encoded by a single gene in mammals. We have characterized two crabp1 genes in zebrafish, designated crabp1a and crabp1b. These two crabp1 genes share the same gene structure as the mammalian CRABP1 genes and encode proteins that show the highest amino acid sequence identity to mammalian CRABPIs. The zebrafish crabp1a and crabp1b were assigned to linkage groups 25 and 7, respectively. Both linkage groups show conserved syntenies to a segment of the human chromosome 15 harboring the CRABP1 locus. Phylogenetic analysis suggests that the zebrafish crabp1a and crabp1b are orthologs of the mammalian CRABP1 genes that likely arose from a teleost fish lineage-specific genome duplication. Embryonic whole mount in situ hybridization detected zebrafish crabp1b transcripts in the posterior hindbrain and spinal cord from early stages of embryogenesis. crabp1a mRNA was detected in the forebrain and midbrain at later developmental stages. In adult zebrafish, crabp1a mRNA was localized to the optic tectum, whereas crabp1b mRNA was detected in several tissues by RT-PCR but not by tissue section in situ hybridization. The differential and complementary expression patterns of the zebrafish crabp1a and crabp1b genes imply that subfunctionalization may be the mechanism for the retention of both crabp1 duplicated genes in the zebrafish genome.
Liu
Rong-Zong
RZ
Department of Biology, Dalhousie University, Halifax, Nova Scotia, Canada.
Sharma
Mukesh K
MK
Sun
Qian
Q
Thisse
Christine
C
Thisse
Bernard
B
Denovan-Wright
Eileen M
EM
Wright
Jonathan M
JM
D000595:Amino Acid Sequence; D000818:Animals; D002875:Chromosomes / Q000235:genetics; D018076:DNA, Complementary / Q000235:genetics; D020440:Gene Duplication; D018507:Gene Expression Regulation, Developmental / Q000235:genetics*; D020131:Genes, Duplicate / Q000235:genetics*; D016678:Genome; D006801:Humans; D007814:Larva / Q000235:genetics / Q000254:growth & development; D008969:Molecular Sequence Data; D009928:Organ Specificity; D010802:Phylogeny; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D018168:Receptors, Retinoic Acid / Q000737:chemistry / Q000235:genetics*; D016415:Sequence Alignment; D014158:Transcription, Genetic / Q000235:genetics; D015027:Zebrafish / Q000196:embryology / Q000235:genetics* / Q000254:growth & development; D029961:Zebrafish Proteins / Q000737:chemistry / Q000235:genetics*
D018076:DNA, Complementary; D012333:RNA, Messenger; D018168:Receptors, Retinoic Acid; D029961:Zebrafish Proteins; C503515:crabp1a protein, zebrafish