
%0 Journal Article
%A Day, Margot L. 
%A Winston, Nicola 
%A McConnell, Josie L. 
%A Cook, David 
%A Johnson, Martin H. 
%T tiK<emph type="7">+</emph> toK<emph type="7">+</emph>: an embryonic clock?
%J Reproduction, Fertility and Development
%D 2001/07/04
%V 13
%N 1
%P 69-79
%K cyclins, developmental timer, EAG, ERG, K+ channel, mouse embryo.
%R https://doi.org/10.1071/RD00048
%U https://www.publish.csiro.au/paper/RD00048 
%X During embryogenesis cells make appropriately timed developmental decisions. Both &#8216;hourglass-like&#8217; and &#8216;clock-like&#8217; mechanisms have been demonstrated to act as timers in early development. The cell cycle rhythm, using feedback circuits to drive cells unidirectionally through checkpoints, is an example of a clock-like timer, but how it operates to time developmental events is unclear. In other cell types, cyclic oscillations in K+ channel activity, which parallel cell cycle and circadian rhythms, may be part of the timing mechanism. Changes in K+ oscillations accompany key developmental transitions and oncogenic transformation. Channel blockade interferes pharmaco-logically with cell cycle initiation or progression, whereas channel over-expression can be oncogenic. K+ channel activity also exists in early mouse oocytes through to at least the blastocyst stage, and it oscillates in phase with the developmental cell cycles, being high in M/G1 and low in S/G2. It resembles physiologically the activity of the K+ channels of the eag- or erg-like families. Reverse transcriptase&#8211;polymerase chain reaction of mouse oocytes has revealed the presence of transcripts encoding both EAG- and ERG-like proteins throughout preimplantation devel-opment. Channel activity continues to oscillate with a cell cycle periodicity in embryos from which the nucleus has been removed, or after inhibition by puromycin of the cyclin B&#8211;cyclin-dependent kinase 1 driven component of the chromosomal cycle. Channel oscillatory activity thus appears to be able to function autonomously of the chromo-somal cycle and may represent a distinct oscillatory timing activity with possible developmental significance. 
