Biomedical subjects

Kenneth J Kemphues

Publications and source records attributed to Kenneth J Kemphues.

6 recordsLinked to original sources

PubMed2006

Interaction of PAR-6 with CDC-42 is required for maintenance but not establishment of PAR asymmetry in C. elegans.

Caenorhabditis elegans embryonic polarity requires the asymmetrically distributed proteins PAR-3, PAR-6 and PKC-3. The rho family GTPase CDC-42 regulates the activities of these proteins in mammals, flies and worms. To clarify its mode of action in C. elegans we disrupted the interaction between PAR-6 and CDC-42 in vivo, and also determined the distribution of GFP-tagged CDC-42 in the early embryo. Mutant PAR-6 proteins unable to interact with CDC-42 accumulated asymmetrically, at a reduced level, but this asymmetry was not maintained during the first division. We also determined that constitutively active GFP::CDC-42 becomes enriched in the anterior during the first cell cycle in a domain that overlaps with PAR-6. The asymmetry is dependent on PAR-2, PAR-5 and PAR-6. Furthermore, we found that overexpression of constitutively active GFP::CDC-42 increased the size of the anterior domain. We conclude that the CDC-42 interaction with PAR-6 is not required for the initial establishment of asymmetry but is required for maximal cortical accumulation of PAR-6 and to maintain its asymmetry.

14-3-3 Proteins↗

PubMed2004

PAR-3 is required for epithelial cell polarity in the distal spermatheca of C. elegans.

PAR-3 is localized asymmetrically in epithelial cells in a variety of animals from Caenorhabditis elegans to mammals. Although C. elegans PAR-3 is known to act in early blastomeres to polarize the embryo, a role for PAR-3 in epithelial cells of C. elegans has not been established. Using RNA interference to deplete PAR-3 in developing larvae, we discovered a requirement for PAR-3 in spermathecal development. Spermathecal precursor cells are born during larval development and differentiate into an epithelium that forms a tube for the storage of sperm. Eggs must enter the spermatheca to complete ovulation. PAR-3-depleted worms exhibit defects in ovulation. Consistent with this phenotype, PAR-3 is transiently expressed and localized asymmetrically in the developing somatic gonad, including the spermathecal precursor cells of L4 larvae. We found that the defect in ovulation can be partially suppressed by a mutation in IPP-5, an inositol polyphosphate 5-phosphatase, indicating that one effect of PAR-3 depletion is disruption of signaling between oocyte and spermatheca. Microscopy revealed that the distribution of AJM-1, an apical junction marker, and apical microfilaments are severely affected in the distal spermatheca of PAR-3-depleted worms. We propose that PAR-3 activity is required for the proper polarization of spermathecal cells and that defective ovulation results from defective distal spermathecal development.

Animals↗

PubMed2003

PAR-1 is required for morphogenesis of the Caenorhabditis elegans vulva.

The Caenorhabditis elegans vulva provides a simple model for the genetic analysis of pattern formation and organ morphogenesis during metazoan development. We have discovered an essential role for the polarity protein PAR-1 in the development of the vulva. Postembryonic RNA interference of PAR-1 causes a protruding vulva phenotype. We found that depleting PAR-1 during the development of the vulva has no detectable effect on fate specification or precursor proliferation, but instead seems to specifically alter morphogenesis. Using an apical junction-associated GFP marker, we discovered that PAR-1 depletion causes a failure of the two mirror-symmetric halves of the vulva to join into a single, coherent organ. The cells that normally form the ventral vulval rings fail to make contact or adhere and consequently form incomplete toroids, and dorsal rings adopt variably abnormal morphologies. We also found that PAR-1 undergoes a redistribution from apical junctions to basolateral domains during morphogenesis. Despite a known role for PAR-1 in cell polarity, we have observed no detectable differences in the distribution of various markers of epithelial cell polarity. We propose that PAR-1 activity at the cell cortex is critical for mediating cell shape changes, cell surface composition, or cell signaling during vulval morphogenesis.

Animals↗

PubMed2002

Integrating interactome, phenome, and transcriptome mapping data for the C. elegans germline.

By integrating functional genomic and proteomic mapping approaches, biological hypotheses should be formulated with increasing levels of confidence. For example, yeast interactome and transcriptome data can be correlated in biologically meaningful ways. Here, we combine interactome mapping data generated for a multicellular organism with data from both large-scale phenotypic analysis ("phenome mapping") and transcriptome profiling. First, we generated a two-hybrid interactome map of the Caenorhabditis elegans germline by using 600 transcripts enriched in this tissue. We compared this map to a phenome map of the germline obtained by RNA interference (RNAi) and to a transcriptome map obtained by clustering worm genes across 553 expression profiling experiments. In this dataset, we find that essential proteins have a tendency to interact with each other, that pairs of genes encoding interacting proteins tend to exhibit similar expression profiles, and that, for approximately 24% of germline interactions, both partners show overlapping embryonic lethal or high incidence of males RNAi phenotypes and similar expression profiles. We propose that these interactions are most likely to be relevant to germline biology. Similar integration of interactome, phenome, and transcriptome data should be possible for other biological processes in the nematode and for other organisms, including humans.

Animals↗

PubMed2002

Gene clustering based on RNAi phenotypes of ovary-enriched genes in C. elegans.

Recently, a set of 766 genes that are enriched in the ovary as compared to the soma was identified by microarray analysis [1]. Here, we report a functional analysis of 98% of these genes by RNA interference (RNAi). Over half the genes tested showed at least one detectable phenotype, most commonly embryonic lethality, consistent with the expectation that ovary transcripts would be enriched for genes that are essential in basic cellular and developmental processes. We find that essential genes are more likely to be conserved and to be highly expressed in the ovary. We extend previous observations and find that fewer than the expected number of ovary-expressed essential genes are present on the X chromosome. We characterized early embryonic defects for 161 genes and used time-lapse microscopy to systematically describe the defects for each gene in terms of 47 RNAi-associated phenotypes. In this paper, we discuss the use of these data to group genes into "phenoclusters"; in the accompanying paper, we use these data as one component in the integration of different types of large-scale functional analyses. We find that phenoclusters correlate well with sequence-based functional predictions and thus may be useful in predicting functions of uncharacterized genes.

Animals↗

PubMed2002

The Caenorhabditis elegans par-5 gene encodes a 14-3-3 protein required for cellular asymmetry in the early embryo.

The establishment of anterior-posterior polarity in the Caenorhabditis elegans embryo requires the activity of the maternally expressed par genes. We report the identification and analysis of a new par gene, par-5. We show that par-5 is required for asynchrony and asymmetry in the first embryonic cell divisions, normal pseudocleavage, normal cleavage spindle orientation at the two-cell stage, and localization of P granules and MEX-5 during the first and subsequent cell cycles. Furthermore, par-5 activity is required in the first cell cycle for the asymmetric cortical localization of PAR-1 and PAR-2 to the posterior, and PAR-3, PAR-6, and PKC-3 to the anterior. When PAR-5 is reduced by mutation or by RNA interference, these proteins spread around the cortex of the one-cell embryo and partially overlap. We have shown by sequence analysis of par-5 mutants and by RNA interference that the par-5 gene is the same as the ftt-1 gene, and encodes a 14-3-3 protein. The PAR-5 14-3-3 protein is present in gonads, oocytes, and early embryos, but is not asymmetrically distributed. Our analysis indicates that the par-5 14-3-3 gene plays a crucial role in the early events leading to polarization of the C. elegans zygote.

14-3-3 Proteins↗