Bonnielin Sceurman et al. (2004) West Coast Worm Meeting "The Myt1 ortholog in C. elegans is essential for oocyte maturation."

Andy Golden, Anna Burrows, Bonnielin Sceurman

[West Coast Worm Meeting, 2004]

Myt1, a member of the WEE1 kinase family, is an essential negative regulator of the CDK/cyclin complex that acts during the G2/M transition of the meiotic cell cycle in Xenopus oocytes. Using RNA interference (RNAi), we have shown C. elegans oocytes depleted of the Myt1 homolog, WEE-1.3, fail to develop and mature normally within the oviduct of the hermaphrodite. Visual observation and antibody staining suggest that these RNAi oocytes mature precociously. The oocytes ovulate normally, but are not fertilized even though they are exposed to wildtype sperm in the spermatheca. Oocytes accumulate in the uterus, clogging the uterus and oviduct - this causes sterility of the treated mother. Eventually, the ability of the hermaphrodite germline to produce normal oocytes becomes greatly compromised. CDK-1 is an abundant maternal protein that needs to be kept inactive during critical phases of oocyte development. WEE-1.3 presumably phosphorylates CDK-1 to inhibit its activity during this developmental time. Interestingly, CDK-1 depletion suppresses the WEE-1.3 RNAi maturation and fertilization defects. This data suggests that WEE-1.3 acts through CDK-1 in the proper regulation of C.elegans oocyte development and maturation.

Christopher T Richie et al. (2004) West Coast Worm Meeting "Identification and Characterization of Separase Cofactors in C. elegans"

Andy Golden, Barry Chestnut, Bonnielin Sceurman, Christopher T Richie

[West Coast Worm Meeting, 2004]

Accurate chromosome segregation requires separation of the sister chromatids during the metaphase-to-anaphase transition. This is achieved when the anaphase-promoting complex (APC/cyclosome) brings about the destruction of securin, an inhibitor of the cysteine protease known as separase. Once activated, separase can then cleave the SCC-1 protein, a member of the cohesion complex that holds the sister chromatids together. In C. elegans, the sep-1(e2406) temperature-sensitive mutant allele of separase causes a pleiotropic phenotype when worms are grown at 20degC (Siomos et al, 2001). In addition to complete sterility and embryonic lethality, sep-1(e2406) also causes developmental abnormalities in the germ line, somatic gonad, and the vulva. In an effort to identify novel regulators and substrates of separase, we have performed a suppressor screen to select for mutations that can rescue the sterility and embryonic lethality associated with the sep-1(e2406) allele when grown at the restrictive temperature. Mutant alleles representing three different loci were recovered and we are currently mapping their position using molecular and classical genetic techniques. We are also using a proteomics approach to identify separase cofactors and substrates by both coimmunoprecipitation with anti-separase antibodies, and affinity-tag pull-down of complexes containing ectopically expressed separase derived from transgenic worms. Mass spectroscopy will be used to characterize any co-purifying proteins.