PUBLICATION

Zebrafish midblastula transition: the onset of zygotic control during development

Authors
Kane, D.A.
ID
ZDB-PUB-010131-24
Date
1991
Source
Ph.D. Thesis : (Thesis)
Registered Authors
Kane, Donald A.
Keywords
none
MeSH Terms
none
PubMed
none
Abstract
In developing embryos, control of the early period following fertilization is maternal; this is first supplemented, and eventually replaced by zygotic control. In studies of the zebrafish embryo, I have characterized this major developmental transition, the midblastula transition (MBT). To contrast the maternal and zygotic types of control that are separated by the MBT, I have characterized developmental events that are proximate to MBT. Fish MBT is similar to Xenopus MBT: During cycle-10, the mitotic cycle lengthens, and shortly afterwards transcription is activated, cell synchrony is lost, and motility is aquired. The cycle at which MBT occurs is dependent on the ploidy of the embryos, indicating that the nucleocytoplasmic ratio governs the onset of MBT. During and shortly after MBT, three mitotic domains become evident in the zebrafish. The first domain is the yolk syncytial layer, which undergoes 3 to 4 synchronous nuclear divisions and then stops dividing completely before the beginning of epiboly, the first morphogenetic movement in the embryo. The second domain is the blastoderm enveloping layer, which generates embryonic periderm. The third, and largest, domain consists of the blastoderm deep cells that later generate the embryo proper. About 1.5 hours after these three domains are first apparent, epiboly begins, and each domain assumes a different function. After the beginning of epiboly, cell movements can be dissected into several components. Embryos homozygous for the zygotically expressed mutation spt-1 have modified one of these movements, convergence, in precursors that normally give rise to trunk somitic mesoderm. Genetic mosaic analysis shows that the mutation autonomously affects only those mesodermal precursors located along the lateral margin of the blastoderm. Other mesodermal cells and all ectodermal precursors do not require spt-1$sp+$ function. These findings reveal an unexpectedly delicate zygotic control of cell movements during early development.
Errata / Notes
Ph.D. Thesis, University of Oregon
Genes / Markers
Figures
Expression
Phenotype
Mutations / Transgenics
Human Disease / Model
Sequence Targeting Reagents
Fish
Antibodies
Orthology
Engineered Foreign Genes
Mapping