[
Development,
2007]
The symmetry-breaking event during polarization of C. elegans embryos is an asymmetric rearrangement of the acto-myosin network, which dictates cell polarity through the differential recruitment of PAR proteins. The sperm-supplied centrosomes are required to initiate this cortical reorganization. Several questions about this event remain unanswered: how is the acto-myosin network regulated during polarization and how does acto-myosin reorganization lead to asymmetric PAR protein distribution? As we discuss, recent studies show that C. elegans embryos use two GTPases, RHO-1 and CDC-42, to regulate these two steps in polarity establishment. Although RHO-1 and CDC-42 control distinct aspects of polarization, they function interdependently to regulate polarity establishment in C. elegans embryos.
[
Oncogene,
2005]
The nematode Caenorhabditis elegans offers a powerful model system to study cell division control during animal development. Progress from the one-cell zygote to adult stage follows a nearly invariant pattern of divisions. This, combined with a transparent body and efficient genetics, allows for sensitive identification and quantitative analysis of cell-cycle mutants. Nearly all G1 control genes identified in C. elegans have mammalian homologs. Examples include a D-type cyclin and CDK4/6-related kinase, a member of the retinoblastoma protein family and CDK inhibitors of the Cip/Kip family. Genetic studies have placed the currently known G1 regulators into pathways similar to those in mammals. Together, this validates the use of C. elegans in identifying additional regulators of cell-cycle entry and exit. For instance, we recently found that the CDC-14 phosphatase promotes maintenance of the quiescent state. Here, we describe cell-cycle control as an integral part of C. elegans development, summarize current knowledge of G1 control genes in the worm, compare the results with those obtained in other species, and discuss the possible implications of cell-cycle studies in C. elegans for higher organisms, including humans.