[Show abstract][Hide abstract] ABSTRACT: Teleost fishes differ from mammals in their fat deposition and distribution. The gene for adipocyte-type fatty acid-binding protein (A-FABP or FABP4) has not been identified thus far in fishes. We have determined the cDNA sequence and defined the structure of a fatty acid-binding protein gene (designated fabp4) from the zebrafish genome. The polypeptide sequence encoded by zebrafish fabp4 showed highest identity to the H(ad)-FABP or H6-FABP from Antarctic fishes and the putative orthologs from other teleost fishes (83-88%). Phylogenetic analysis clustered the zebrafish FABP4 with all Antarctic fish H6-FABPs and putative FABP4s from other fishes in a single clade, and then with the mammalian FABP4s in an extended clade. Zebrafish fabp4 was assigned to linkage group 19 at a distinct locus from fabp3. A number of closely linked syntenic genes surrounding the zebrafish fabp4 locus were found to be conserved with human FABP4. The zebrafish fabp4 transcripts showed sequential distribution in the developing eye, diencephalon and brain vascular system, from the middle somitogenesis stage to 48 h postfertilization, whereas fabp3 mRNA was located widely in the embryonic and/or larval central nervous system, retina, myotomes, pancreas and liver from middle somitogenesis to 5 days postfertilization. Differentiation in developmental regulation of zebrafish fabp4 and fabp3 gene transcription suggests distinct functions for these two paralogous genes in vertebrate development.
[Show abstract][Hide abstract] ABSTRACT: Fatty acid-binding protein type 1 (FABP1), commonly termed liver-type fatty acid-binding protein (L-FABP), is encoded by a single gene in mammals. We cloned and sequenced cDNAs for two distinct FABP1s in zebrafish coded by genes designated fabp1a and fabp1b. The zebrafish proteins, FABP1a and FABP1b, show highest sequence identity and similarity to the human protein FABP1. Zebrafish fabp1a and fabp1b genes were assigned to linkage groups 5 and 8, respectively. Both linkage groups show conserved syntenies to a segment of mouse chromosome 6, rat chromosome 4 and human chromosome 2 harboring the FABP1 locus. Phylogenetic analysis further suggests that zebrafish fabp1a and fabp1b genes are orthologs of mammalian FABP1 and most likely arose by a whole-genome duplication event in the ray-finned fish lineage, estimated to have occurred 200-450 million years ago. The paralogous fabp10 gene encoding basic L-FABP, found to date in only nonmammalian vertebrates, was assigned to zebrafish linkage group 16. RT-PCR amplification of mRNA in adults, and in situ hybridization to whole-mount embryos to fabp1a, fabp1b and fapb10 mRNAs, revealed a distinct and differential pattern of expression for the fabp1a, fabp1b and fabp10 genes in zebrafish, suggesting a division of function for these orthogolous and paralogous gene products following their duplication in the vertebrate genome. The differential and complementary expression patterns of the zebrafish fabp1a, fapb1b and fabp10 genes imply a hierarchical subfunctionalization that may account for the retention of both the duplicated fabp1a and fabp1b genes, and the fabp10 gene in the zebrafish genome.
[Show abstract][Hide abstract] ABSTRACT: 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.
[Show abstract][Hide abstract] ABSTRACT: The cellular retinoic acid-binding protein 2 (CRABP2) is believed to be involved in regulating access of retinoic acid to nuclear retinoic acid receptors. We have determined the cDNA sequence and the genomic organization of the duplicated crabp2 gene (crabp2b) in zebrafish. The crabp2b cDNA was 522bp in length and encodes a polypeptide consisting of 146 amino acids. Radiation hybrid mapping assigned the crabp2b gene to zebrafish linkage group 19. The comparison of the mapped human CRABP2 gene, zebrafish crabp2a and zebrafish crabp2b genes revealed that human chromosome 1 has a syntenic relationship to zebrafish linkage groups 16 and 19. Reverse transcription-polymerase chain reaction (RT-PCR) detected crabp2b mRNA in total RNA extracted from whole adult zebrafish, but not in any of the adult zebrafish tissues examined. The crabp2a mRNA was detected in total RNA extracted from whole adult zebrafish, adult zebrafish muscle, testes, and skin and to a lesser extent in heart, ovary and brain. No crabp2a mRNA-specific product was detected in kidney, liver or intestine of the adult zebrafish. Whole mount in situ hybridization detected crabp2b and crabp2a mRNA in a number of structures known to require retinoic acid signaling during embryonic development. The crabp2b mRNA was detected in the central nervous system, branchial arches, pectoral fins, retina (dorsal to the lens), epidermis and otic vesicle of the developing zebrafish. The crabp2a transcripts were detected by whole mount in situ hybridization in the central nervous system, epidermis, proliferative zone of the retina, intestinal bulb, oesophagus, pectoral fins and branchial arches during zebrafish embryonic development.
[Show abstract][Hide abstract] ABSTRACT: The intestinal fatty acid-binding protein (I-FABP) shows binding specificity for long-chain fatty acids and is proposed to be involved in uptake of dietary fatty acids and their intracellular transport. We have determined the sequence of the gene encoding I-FABP in zebrafish. The zebrafish I-FABP gene contains four exons interrupted by three introns. Radiation hybrid mapping assigned the I-FABP gene to linkage group 1. A 924 bp sequence 5' upstream of the initiation codon in the I-FABP gene contained several putative cis-acting regulatory elements. In adult zebrafish, reverse transcription-polymerase chain reaction (RT-PCR) detected I-FABP mRNA in intestine, brain, liver, muscle and testis. Quantitative RT-PCR demonstrated that I-FABP mRNA was most abundant in intestine, followed by brain. I-FABP mRNA levels were very low in muscle, testis, heart, liver, skin and ovary. RT-PCR using total RNA extracted from zebrafish embryos detected I-FABP mRNA as early as 12 h post-fertilization. Whole-mount in situ hybridization to zebrafish embryos detected I-FABP mRNA in the yolk syncytial layer (YSL) at early somitogenesis. Later during embryonic development the I-FABP mRNA was detected in the intestinal bulb, liver and pancreas primordium. Expression in YSL, liver or pancreas has not been previously reported for fish or mammalian I-FABP genes and may be related to specific physiological differences between fishes and mammals.
Comparative Biochemistry and Physiology Part B Biochemistry and Molecular Biology 09/2004; 138(4):391-8. DOI:10.1016/j.cbpc.2004.05.009 · 1.90 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: We report the sequence of a cDNA clone coding for a cellular retinoic acid-binding protein (CRABP) in zebrafish. The encoded polypeptide is 142 amino acids in length with an estimated molecular mass of 15.8 kDa and a calculated isoelectric point of 5.2. The zebrafish CRABP exhibits highest sequence identity to the pufferfish CRABPIIa (83%) and CRABPIIb (79%), and human CRABPII (74%) than to any other member of the intracellular lipid-binding protein (ILBP) family. A phylogenetic tree for different members of the ILBP multigene family including fatty acid-binding proteins (FABPs), cellular retinol-binding proteins (CRBPs) and CRABPs shows that the cloned zebrafish cDNA encodes a protein that clusters with CRABPs from other species and not with CRBPs and FABPs. Reverse-transcription polymerase chain reactions (RT-PCR), using oligonucleotide primers specific to the zebrafish CRABP cDNA made from total RNA of embryos collected at various developmental stages, did not detect the CRABP mRNA until 12 h post-fertilization. In adult zebrafish, CRABP mRNA was detected by RT-PCR in total RNA extracted from muscle, testes and skin, barely detectable in heart, ovary and brain and undetectable in liver, kidney and intestine. Quantitative RT-PCR (qRT-PCR) revealed a similar tissue-specific distribution for zebrafish CRABP mRNA with highest levels of CRABP mRNA in muscle followed by testes, skin, ovary and much lower levels in heart. Radiation hybrid mapping assigned the CRABP gene to linkage group 16 in the zebrafish genome. Comparison of the mapped zebrafish CRABP and human CRABPII genes revealed that zebrafish linkage group 16 has a syntenic relationship with human chromosome 1. Based on phylogenetic analysis and the syntenic relationship to the CRABPII gene in human, the zebrafish cDNA clone appears to code for a type II CRABP.
[Show abstract][Hide abstract] ABSTRACT: We have determined the nucleotide sequence of a zebrafish cDNA clone that codes for a cellular retinol-binding protein type II (CRBPII). Radiation hybrid mapping revealed that the zebrafish and human CRBPII genes are located in syntenic groups. In situ hybridization and emulsion autoradiography localized the CRBPII mRNA to the intestine and the liver of adult zebrafish. CRBPII and intestinal fatty acid binding protein (I-FABP) mRNA was colocalized to the same regions along the anterior-posterior gradient of the zebrafish intestine. Similarly, CRBPII and I-FABP mRNA are colocalized in mammalian and chicken intestine. CRBPII mRNA, but not I-FABP mRNA, was detected in adult zebrafish liver which is in contrast to mammals where liver CRBPII mRNA levels are high during development but rapidly decrease to very low or undetectable levels following birth. CRBPII and I-FABP gene expression appears therefore to be co-ordinately regulated in the zebrafish intestine as has been suggested for mammals and chicken, but CRBPII gene expression is markedly different in the liver of adult zebrafish compared to the livers of mammals. As such, retinol metabolism in zebrafish may differ from that of mammals and require continued production of CRBPII in adult liver. The primary sequence of the coding regions of fish and mammalian CRBPII genes, their relative chromosomal location in syntenic groups and possibly portions of the control regions involved in regulation of CRBPII gene expression in the intestine appear therefore to have been conserved for more than 400 million years.
European Journal of Biochemistry 10/2002; 269(18):4685-92. · 3.58 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: We have determined the nucleotide sequence for a cDNA clone derived from zebrafish (Danio rerio) that codes for a fatty acid binding protein (FABP). Amino acid sequence similarity of the zebrafish FABP was highest to FABPs isolated from the livers of catfish, chicken, salamander and iguana. The open-reading frame of the zebrafish FABP cDNA codes for a protein of 14.0 kDa with a calculated isoelectric point of 8.8. The zebrafish liver-type FABP (L-FABP) cDNA hybridized to single restriction fragments of total zebrafish genomic DNA digested with the restriction endonucleases HaeIII or EcoRI suggesting that a single copy of the L-FABP gene is present in the zebrafish genome. Northern blot analysis demonstrated that the zebrafish L-FABP cDNA hybridized to a transcript of 700 nucleotides in total zebrafish RNA. In situ hybridization and emulsion autoradiography revealed that the L-FABP was expressed exclusively in the liver of the adult zebrafish. Based on amino acid sequence similarity, the isoelectric point and its tissue-specific pattern of expression, we conclude that this zebrafish FABP belongs to the basic liver-type FABPs only found, thus far, in non-mammalian vertebrates.