title: Pou5f1/Oct4 promotes cell survival via direct activation of mych expression during zebrafish gastrulation.
abstract: Myc proteins control cell proliferation, cell cycle progression, and apoptosis, and play important roles in cancer as well in establishment of pluripotency. Here we investigated the control of myc gene expression by the Pou5f1/Oct4 pluripotency factor in the early zebrafish embryo. We analyzed the expression of all known zebrafish Myc family members, myca, mycb, mych, mycl1a, mycl1b, and mycn, by whole mount in situ hybridization during blastula and gastrula stages in wildtype and maternal plus zygotic pou5f1 mutant (MZspg) embryos, as well as by quantitative PCR and in time series microarray data. We found that the broad blastula and gastrula stage mych expression, as well as late gastrula stage mycl1b expression, both depend on Pou5f1 activity. We analyzed ChIP-Seq data and found that both Pou5f1 and Sox2 bind to mych and mycl1b control regions. The regulation of mych by Pou5f1 appears to be direct transcriptional activation, as overexpression of a Pou5f1 activator fusion protein in MZspg embryos induced strong mych expression even when translation of zygotically expressed mRNAs was suppressed. We further showed that MZspg embryos develop enhanced apoptosis already during early gastrula stages, when apoptosis was not be detected in wildtype embryos. However, Mych knockdown alone did not induce early apoptosis, suggesting potentially redundant action of several early expressed myc genes, or combination of several pathways affected in MZspg. Experimental mych overexpression in MZspg embryos did significantly, but not completely suppress the apoptosis phenotype. Similarly, p53 knockdown only partially suppressed apoptosis in MZspg gastrula embryos. However, combined knockdown of p53 and overexpression of Mych completely rescued the MZspg apoptosis phenotype. These results reveal that Mych has anti-apoptotic activity in the early zebrafish embryo, and that p53-dependent and Myc pathways are likely to act in parallel to control apoptosis at these stages.
authors.affiliation: Developmental Biology, Institute Biology I, Faculty of Biology, Albert-Ludwigs-University Freiburg, Freiburg, Germany.
authors.forename: Kay
authors.initials: K
authors.lastname: Kotkamp
authors.affiliation: Developmental Biology, Institute Biology I, Faculty of Biology, Albert-Ludwigs-University Freiburg, Freiburg, Germany.
authors.forename: Esther
authors.initials: E
authors.lastname: Kur
authors.affiliation: Developmental Biology, Institute Biology I, Faculty of Biology, Albert-Ludwigs-University Freiburg, Freiburg, Germany.
authors.forename: Björn
authors.initials: B
authors.lastname: Wendik
authors.affiliation: Developmental Biology, Institute Biology I, Faculty of Biology, Albert-Ludwigs-University Freiburg, Freiburg, Germany.
authors.forename: Bożena K
authors.initials: BK
authors.lastname: Polok
authors.affiliation: Biological Services, Weizmann Institute of Science, Rehovot, Israel.
authors.forename: Shifra
authors.initials: S
authors.lastname: Ben-Dor
authors.affiliation: Developmental Biology, Institute Biology I, Faculty of Biology, Albert-Ludwigs-University Freiburg, Freiburg, Germany; BIOSS - Centre for Biological Signalling Studies, Freiburg, Germany.
authors.forename: Daria
authors.initials: D
authors.lastname: Onichtchouk
authors.affiliation: Developmental Biology, Institute Biology I, Faculty of Biology, Albert-Ludwigs-University Freiburg, Freiburg, Germany; BIOSS - Centre for Biological Signalling Studies, Freiburg, Germany.
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Driever
mesh_terms: D000818:Animals; D017209:Apoptosis; D002470:Cell Survival; D004625:Embryo, Nonmammalian / Q000166:cytology / Q000378:metabolism*; D054262:Gastrulation; D015870:Gene Expression; D018507:Gene Expression Regulation, Developmental; D050814:Octamer Transcription Factor-3 / Q000502:physiology*; D009928:Organ Specificity; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D014157:Transcription Factors / Q000235:genetics* / Q000378:metabolism; D015533:Transcriptional Activation; D015027:Zebrafish / Q000196:embryology*; D029961:Zebrafish Proteins / Q000235:genetics* / Q000378:metabolism / Q000502:physiology*
chemical_list: C529127:Mych protein, zebrafish; D050814:Octamer Transcription Factor-3; C085437:Pou5f3 protein, zebrafish; D014157:Transcription Factors; D029961:Zebrafish Proteins