1) him-8, him-5 and him-1 asymmetrically affect recombination (pairing?) of the X chromosome. - 2) Transformation rescue of him-8. Sherryl Broverman and Philip Meneely, FHCRC, 1124 Columbia St., Seattle WA 98104, (206) 667-4523i FAX 206 667 4737
A conserved network of PAR polarity proteins is required for establishment of cellular polarity in a wide variety of systems. These proteins are typically segregated into mutually exclusive, functionally distinct membrane domains which define the axis of polarity. In the one-celled C. elegans embryo, discrete sets of PAR proteins are partitioned into roughly equal sized anterior and posterior domains, which are essential for the proper inheritance of cell fate determinants during the asymmetric first cell division. The formation of PAR domains has been shown to depend on a highly contractile cortical actomyosin network that is itself polarized and is required for establishing PAR polarity. PAR domains also depend on mutual antagonistic interactions between PAR proteins, which are essential for maintaining their stable, mutually exclusive distribution within discrete domains. However, despite progress in understanding the molecular activities involved in these processes, we lack a basic physical mechanism for explaining how the activities of the actomyosin cortex and the PAR proteins are coupled in order to give rise to the stable, reproducibly sized PAR domains that are observed in the embryo. In order to provide insight into the types of mechanisms that could underlie the formation of PAR domains, we undertook a quantitative description of the dynamics of PAR proteins in C. elegans embryos. The results of this analysis indicate that PAR proteins diffuse extensively on the membrane of embryos, exchange between membrane-associated and cytoplasmic states, and are subject to advection by actomyosin-dependent cortical flow. We find that these observed behaviors, when coupled to the documented antagonism between PAR proteins, are sufficient to generate a reaction-diffusion driven system for establishing PAR polarity. The theoretical model we propose provides a single, rather simple physical mechanism that explains the actomyosin-dependent polarization of the embryo, the maintenance of mutually exclusive PAR domains, and the reproducible determination of domain size. Importantly, in this model the stable partitioning of the embryo into domains is a function of intrinsic properties of the PAR proteins and does not appear to depend on an underlying scaffold function of the actomyosin cortex. Rather, this work suggests that the actomyosin cortex acts primarily through the generation of cortical flow which provides a robust trigger to ensure that polarization of the PAR system occurs with the proper timing and geometry.
Gary Williams1, Paul Davis1, Anthony Rogers1, Philip Ozersky2, John Spieth2, Tamberlyn Bieri2, Darin Blasiar2. WormBase is an international consortium of biologists and computer scientists from Caltech (USA), Cold Spring Harbor Laboratory (USA), Wellcome Trust Sanger Institute (UK) and the Genome Sequencing Center at Washington University (USA).. WormBase is dedicated to providing the research community with accurate, current, accessible information concerning the genetics, genomics and biology of C. elegans, and some related nematodes. WormBase can be freely accessed at www.wormbase.org, and is also available for download at ftp://ftp.wormbase.org/pub/wormbase A new data release is produced every three weeks. Recently some new datasets have been added to the database to aid curation.The protein products from automated gene prediction in C. remanei have been mapped to the C. elegans genome; InterPro motifs are no longer taken from SwissProt annotations, but are directly predicted from the C. elegans proteins; contigs of ESTs from other nematode species produced by the NEMBASE and Nematode.net projects have been mapped to the genome and a new set of TEC-REDs have been mapped to the genome resulting in 3,325 new trans-spliced sites which mark the 5'' ends of genes or isoforms. Work is underway to classify and curate transposons and we intend to add Mass-Spec data from several sources to improve coding sequence validation.. Over the last year the curated coding sequences have increased from 19,854 to 20,060 and alternately spliced isoforms have increased from 2,772 to 2,883. The number of genes where every base of every exon is confirmed by EST evidence has increased from 6,427 to 6,584. In the C. elegans proteins there have been 630 modified entries, 440 deleted entries, 709 new entries and 64 reappeared entries.. WormBase is supported by a grant from the National Human Genome Research Institute at the US National Institute of Health #P41 HG02223 and the British Medical Research Council.