|Cell Cycle Research|
Syncytial embryo in anaphase
Early embryogenesis is characterized by several exceedingly rapid cell cycles, which are thought to set the stage for the patterning events that will follow. This phenomenon is conserved to all metazoan phyla. As gastrulation approaches, there is a remodeling of fundamental cell behaviors collectively referred to as the mid-blastula transition (MBT): the cycles slow and eventually arrest, cells undergo cellularization and gross rearrangement, and there is a major turnover of the mRNA population as the embryo goes through the maternal-zygotic transition (MZT).
Interphase progressively lengthens over cycles 11-14 as origins of replication no longer fire simultaneously. Satellite 356 is among the late replicating sequences (DNA in blue; satellite 356 in pink)Taken by Tony Shermoen
We have shown that S phase duration is the major timer of the early embryonic cycle (McCleland et al., 2009), that S phase length increases because of delays in the replication of heterochromatic satellite sequences (Shermoen et al., 2011), that high “mitotic” cyclin:Cdk1 drives early replication of satellite sequences during the fast early cycles, and that the abrupt slowing of cell cycle 14 begins with a much longer S phase (~60 min) that requires the downregulation of Cdc25 and secondarily cyclin:Cdk1 (Farrell et al, 2012).
From the seminal paper: cdc25stg expression (pink) just prior to gastrulation (see Edgar, 1989)
|· Cell Cycle · Mitochondria|