© Springer International Publishing Switzerland 2017 441
F. Pelegri et al. (eds.), Vertebrate Development, Advances in Experimental
Medicine and Biology 953, DOI 10.1007/978-3-319-46095-6_9
Chapter 9
Cell Cycle Remodeling and Zygotic Gene
Activation at the Midblastula Transition
Maomao Zhang, Jennifer Skirkanich, Michael A. Lampson,
and Peter S. Klein
Abstract Following fertilization, vertebrate embryos delay large-scale activation of
the zygotic genome from several hours in fish and amphibians to several days in mam-
mals. Externally developing embryos also undergo synchronous and extraordinarily
rapid cell divisions that are accelerated by promiscuous licensing of DNA replication
origins, absence of gap phases and cell cycle checkpoints, and preloading of the egg
with maternal RNAs and proteins needed to drive early development. After a species-
specific number of cell divisions, the cell cycle slows and becomes asynchronous,
gap phases appear, checkpoint functions are acquired, and large- scale zygotic gene
M. Zhang
Department of Biology, University of Pennsylvania, Philadelphia, PA, USA
Cell and Molecular Biology Graduate Group, Perelman School of Medicine at the University
of Pennsylvania, Philadelphia, PA, USA
Department of Cancer Biology and Genetics, Memorial Sloan Kettering Cancer Center,
New York, NY, USA
J. Skirkanich
Cell and Molecular Biology Graduate Group, Perelman School of Medicine at the University
of Pennsylvania, Philadelphia, PA, USA
Department of Biology, Bryn Mawr College, Bryn Mawr, PA, USA
M.A. Lampson (*)
Department of Biology, University of Pennsylvania, Philadelphia, PA, USA
Cell and Molecular Biology Graduate Group, Perelman School of Medicine at the University
of Pennsylvania, Philadelphia, PA, USA
e-mail: [email protected]
P.S. Klein (*)
Cell and Molecular Biology Graduate Group, Perelman School of Medicine at the University
of Pennsylvania, Philadelphia, PA, USA
Department of Medicine (Hematology-Oncology), Perelman School of Medicine at the
University of Pennsylvania, Philadelphia, PA, USA
e-mail: [email protected]
*Author contributed equally with all other contributors.