Characterization of hey bHLH genes in teleost fish.
Hairy-related basic helix-loop-helix (bHLH) transcription factors are targets of Delta-Notch signaling and represent essential components for a number of cell fate decisions during vertebrate embryogenesis. Hey genes encode a subfamily of hairy-related proteins that have been implicated in processes like somitogenesis, blood vessel and heart development. We have identified and characterized hey genes in three teleost fish lineages using degenerate PCR and database searches. Phylogenetic analysis of Hey proteins suggests a complex pattern of evolution with high divergence of hey2 in Takifugu rubripes (Fugu, Japanese pufferfish) and possibly loss in the related Tetraodon nigroviridis (the freshwater pufferfish). In addition, duplication of hey1 in both pufferfishes, Fugu and Tetraodon, was observed. Conversely, zebrafish (Danio rerio) has the same complement of three hey genes as known from mammals. All three hey genes show much more restricted gene expression profiles in zebrafish when compared to mouse. Importantly, while all three murine Hey genes are expressed in overlapping patterns in the presomitic mesoderm (PSM) and somites, in zebrafish only hey1 shows PSM and somite expression in a highly dynamic fashion. Therefore, while overlapping expression might account for redundancy of hey function in higher vertebrates, this is unlikely to be the case in zebrafish. In deltaD (dlD) deficient after-eight zebrafish mutants, the dynamic expression of hey1 in the PSM is impaired and completely lost in newly formed somitomeres. Overexpression of dlD on the other hand results in the ectopic expression of hey1 in the axial mesoderm. Hence, hey1 represents a target of Delta-Notch signaling dynamically expressed during somite formation in zebrafish.
Winkler
Christoph
C
Department of Physiological Chemistry I, Biocenter, University of Wuerzburg, Am Hubland, 97074 Wuerzburg, Germany. winkler@biozentrum.uni-wuerzburg.de
Elmasri
Harun
H
Klamt
Barbara
B
Volff
Jean-Nicolas
JN
Gessler
Manfred
M
D000595:Amino Acid Sequence; D000818:Animals; D051792:Basic Helix-Loop-Helix Proteins; D005075:Biological Evolution; D015870:Gene Expression; D020869:Gene Expression Profiling; D018257:Helix-Loop-Helix Motifs; D017403:In Situ Hybridization; D008648:Mesoderm / Q000378:metabolism; D008969:Molecular Sequence Data; D009419:Nerve Tissue Proteins / Q000378:metabolism; D012097:Repressor Proteins / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction; D019170:Somites / Q000166:cytology; D023741:Takifugu / Q000235:genetics* / Q000378:metabolism; D023721:Tetraodontiformes / Q000196:embryology / Q000235:genetics*; D014157:Transcription Factors / Q000737:chemistry / Q000235:genetics*; D015027:Zebrafish / Q000196:embryology / Q000235:genetics* / Q000378:metabolism; D029961:Zebrafish Proteins / Q000378:metabolism
D051792:Basic Helix-Loop-Helix Proteins; D009419:Nerve Tissue Proteins; D012097:Repressor Proteins; D014157:Transcription Factors; D029961:Zebrafish Proteins; C405694:Hairy, HRT1 protein; C468126:dld protein, zebrafish