RESUMO
How animals adaptively respond to a cold or hot environment has been questioned for a long time. Recently, with the aid of microarray analysis, various temperature-sensitive genes have been identified in several species. However, a definitive hypothesis regarding the mechanism of adaptation has not been proposed. In the present study, we surveyed, in medaka (Oryzias latipes), genes for which the level of expression changes depending on the surrounding temperature. A messenger RNA differential display of medaka muscle total RNA revealed one such gene encoding transcription enhancer factor-1 (TEF-1). In medaka muscle, the TEF-1 gene produces two splicing variants, TEF-1A and TEF-1B mRNAs. During cold acclimation, the mRNA level of TEF-1A decreased, whereas that of TEF-1B increased. We also found that three putative downstream genes of TEF-1, two for myosin heavy chain (MyHC) and one for troponin T (TnT), a specific group of muscle proteins, were transcribed in a temperature-dependent manner. These results suggest that the transcription of MyHC and/or TnT is regulated by TEF-1 and that these molecules participate in muscle reconstruction during temperature adaptation in fish.
Assuntos
Aclimatação/genética , Temperatura Baixa , Proteínas de Ligação a DNA/genética , Proteínas de Peixes/genética , Regulação da Expressão Gênica , Oryzias/genética , Fatores de Transcrição/genética , Aclimatação/fisiologia , Sequência de Aminoácidos , Animais , Dados de Sequência Molecular , Oryzias/fisiologia , Fatores de TempoRESUMO
Polycomb group (PcG) genes are required for stable inheritance of epigenetic states throughout development, a phenomenon termed cellular memory. In Drosophila and mice, the product of the E(z) gene, one of the PcG genes, constitutes the ESC-E(Z) complex and specifically methylates histone H3. It has been argued that this methylation sets the stage for appropriate repression of certain genes. Here, we report the isolation of a well-conserved homolog of E(z), olezh2, in medaka. Hypomorphic knock-down of olezh2 resulted in a cyclopia phenotype and markedly perturbed hedgehog signaling, consistent with our previous report on oleed, a medaka esc. We also found cyclopia in embryos treated with trichostatin A, an inhibitor of histone deacetylase, which is a transient component of the ESC-E(Z) complex. The level of tri-methylation at lysine 27 of histone H3 was substantially decreased in both olezh2 and oleed knock-down embryos, and in embryos with hedgehog signaling perturbed by forskolin. We conclude that the ESC-E(Z) complex per se participates in hedgehog signaling.