What regulates the spatial limits of the cortical myosin patch?
Why is myosin recruitment limited to the epi-nuclear cortical regions and why is myosin not recruited to the cortex before cycle 4? We believe this reflects the localized activation and inactivation of Cdc2 associated with the expanding nuclear region. Edgar et al. (1994) found that cyclin B levels and Cdc2 activity remain globally high during the first eight mitotic cycles. The authors proposed that during precortical divisions, local degradation of cyclin B associated with each dividing nucleus is sufficient to drive mitotic exit of individual nuclei even though the cyclin B levels (and therefore Cdc2 activity) within the egg remain globally elevated. Su et al. (1998) demonstrated that during syncytial divisions, despite the constant global presence of cyclins and Cdc2 activity, proteolysis of cyclins is still essential for nuclei to exit mitosis. They proposed that there is a local change in Cdc2 activity through degradation of small local pools of cyclins associated with the mitoti
