This End Up

Science's STKE  05 Sep 2006:
Vol. 2006, Issue 351, pp. tw309
DOI: 10.1126/stke.3512006tw309


In early embryo development, polarity is established as early as the one-cell stage, when sperm entry triggers the asymmetric distribution of proteins and generation of an anteroposterior axis. Jenkins et al. now report the identity of a sperm-donated factor that affects protein polarity and the actomyosin cytoskeleton within the early nematode embryo. At fertilization, the sperm contributes CYK-4 protein to the egg. Proteins that participate with CYK-4 for polarity initiation include RHO-1, a member of the RhoA family of guanosine triphosphatases (GTPases), and ECT-2, a guanine nucleotide exchange factor. CYK-4 is a GTPase activating protein. ECT-2 and RHO-1 proteins promote, but CYK-4 inhibits, activated myosin light chain and actomyosin contractility. Because CYK-4 is expressed in sperm of other species, it will be of interest to know whether this polarity mechanism is conserved among other species that display actomyosin contraction.

N. Jenkins, J. R. Saam, S. E. Mango, CYK-4/GAP provides a localized cue to initiate anteroposterior polarity upon fertilization. Science 313, 1298-1301 (2006). [Abstract] [Full Text]