title: Conserved co-regulation and promoter sharing of hoxb3a and hoxb4a in zebrafish.
abstract: The expression of zebrafish hoxb3a and hoxb4a has been found to be mediated through five transcripts, hoxb3a transcripts I-III and hoxb4a transcripts I-II, driven by four promoters. A "master" promoter, located about 2 kb downstream of hoxb5a, controls transcription of a pre-mRNA comprising exon sequences of both genes. This unique gene structure is proposed to provide a novel mechanism to ensure overlapping, tissue-specific expression of both genes in the posterior hindbrain and spinal cord. Transgenic approaches were used to analyze the functions of zebrafish hoxb3a/hoxb4a promoters and enhancer sequences containing regions of homology that were previously identified by comparative genomics. Two neural enhancers were shown to establish specific anterior expression borders within the hindbrain and mediate expression in defined neuronal populations derived from hindbrain rhombomeres (r) 5 to 8, suggesting a late role of the genes in neuronal cell lineage specification. Species comparison showed that the zebrafish hoxb3a r5 and r6 enhancer corresponded to a sequence within the mouse HoxA cluster controlling activity of Hoxa3 in r5 and r6, whereas a homologous region within the HoxB cluster activated Hoxb3 expression but limited to r5. We conclude that the similarity of hoxb3a/Hoxa3 regulatory mechanisms reflect the shared descent of both genes from a single ancestral paralog group 3 gene.
authors.affiliation: Department of Physiology and Neuroscience, NYU Medical School, New York, NY 10016, USA.
authors.forename: Thorsten
authors.initials: T
authors.lastname: Hadrys
authors.forename: Beena
authors.initials: B
authors.lastname: Punnamoottil
authors.forename: Mareike
authors.initials: M
authors.lastname: Pieper
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Kikuta
authors.forename: Guillaume
authors.initials: G
authors.lastname: Pezeron
authors.forename: Thomas S
authors.initials: TS
authors.lastname: Becker
authors.forename: Victoria
authors.initials: V
authors.lastname: Prince
authors.forename: Robert
authors.initials: R
authors.lastname: Baker
authors.forename: Silke
authors.initials: S
authors.lastname: Rinkwitz
mesh_terms: D000818:Animals; D030801:Animals, Genetically Modified; D002454:Cell Differentiation / Q000235:genetics; D004625:Embryo, Nonmammalian; D004742:Enhancer Elements, Genetic / Q000235:genetics; D005091:Exons; D005260:Female; D018507:Gene Expression Regulation, Developmental; D018398:Homeodomain Proteins / Q000235:genetics* / Q000378:metabolism; D008297:Male; D051379:Mice; D008969:Molecular Sequence Data; D011401:Promoter Regions, Genetic / Q000235:genetics*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012249:Rhombencephalon / Q000166:cytology / Q000196:embryology; D012689:Sequence Homology, Nucleic Acid; D029867:Xenopus Proteins / Q000235:genetics; D015027:Zebrafish / Q000196:embryology / Q000235:genetics*; D029961:Zebrafish Proteins / Q000235:genetics* / Q000378:metabolism
chemical_list: D018398:Homeodomain Proteins; C514261:Hoxb3a protein, zebrafish; C514262:Hoxb4a protein, zebrafish; D029867:Xenopus Proteins; D029961:Zebrafish Proteins