title: Highly asynchronous and asymmetric cleavage divisions accompany early transcriptional activity in pre-blastula medaka embryos.
abstract: In the initial phase of development of fish embryos, a prominent and critical event is the midblastula transition (MBT). Before MBT cell cycle is rapid, highly synchronous and zygotic gene transcription is turned off. Only during MBT the cell cycle desynchronizes and transcription is activated. Multiple mechanisms, primarily the nucleocytoplasmic ratio, are supposed to control MBT activation. Unexpectedly, we find in the small teleost fish medaka (Oryzias latipes) that at very early stages, well before midblastula, cell division becomes asynchronous and cell volumes diverge. Furthermore, zygotic transcription is extensively activated already after the 64-cell stage. Thus, at least in medaka, the transition from maternal to zygotic transcription is uncoupled from the midblastula stage and not solely controlled by the nucleocytoplasmic ratio.
authors.forename: Michael
authors.initials: M
authors.lastname: Kraeussling
authors.forename: Toni Ulrich
authors.initials: TU
authors.lastname: Wagner
authors.forename: Manfred
authors.initials: M
authors.lastname: Schartl
mesh_terms: D000818:Animals; D036703:Blastula / Q000166:cytology / Q000196:embryology / Q000378:metabolism*; D002453:Cell Cycle / Q000235:genetics; D002455:Cell Division / Q000235:genetics*; D056744:Cyclin B1 / Q000235:genetics; D004625:Embryo, Nonmammalian / Q000166:cytology / Q000196:embryology / Q000378:metabolism*; D029941:Fish Proteins / Q000235:genetics; D018507:Gene Expression Regulation, Developmental; D018613:Microscopy, Confocal; D024101:Mitochondrial Proteins / Q000235:genetics; D009990:Oryzias / Q000196:embryology / Q000235:genetics* / Q000378:metabolism; D010766:Phosphorylation; D012319:RNA Polymerase II / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012269:Ribosomal Proteins / Q000235:genetics; D013997:Time Factors; D014158:Transcription, Genetic
chemical_list: D056744:Cyclin B1; D029941:Fish Proteins; D024101:Mitochondrial Proteins; D012269:Ribosomal Proteins; C112310:mitochondrial ribosomal protein S12; D012319:RNA Polymerase II