Marcela Kokes et al. (2007) International Worm Meeting "Genetic analysis of C. elegans gut granule biogenesis."

Andrea L. Lawrenson, Natalie Miller, Emily Scavarda, Marcela Kokes, Maxwell J. Kramer, Greg J. Hermann, Beverley M. Rabbitts

[International Worm Meeting, 2007]

Caenorhabditis elegans intestinal cells are characterized by the presence of gut granules, lysosome-related organelles that contain autofluorescent and birefringent material. Gut granule formation requires the activity of AP-3 subunits, HOPS, and GLO-1/Rab38, genes whose homologues function in trafficking to lysosomes and lysosome-related organelles. To define the molecular and cellular pathways that function in gut granule biogenesis, we have isolated a collection of mutants that lack and/or mislocalize birefringent material into the embryonic intestinal lumen. The glo (gut granule loss) mutants define at least eight different genes. Here we present our phenotypic and molecular analysis of glo-3 and the gene(s) defined by two lethal glo alleles kx42 and kx76. glo-1 and glo-4 encode a Rab38 homologue and its predicted guanine nucleotide exchange factor, respectively, that function in gut granule biogenesis. The phenotype and genetic interactions exhibited by glo-3 suggest that it might function with glo-1 and glo-4 in gut granule biogenesis. glo-3(-) embryonic intestinal cells lack organelles with lysosomal characteristics while other endocytic compartments appear to be unaltered. We have cloned glo-3 and find that it encodes a novel predicted membrane protein that is associated with gut granules. During embryogenesis when gut granules are generated, glo-3, like glo-1, is only expressed in intestinal cells. Interestingly, the expression of these genes coincides with the specification of the intestinal cell fate providing a system by which the mechanisms involved in the initial formation of lysosome-related organelles during embryonic development can be investigated. In our Glo screens we identified 22 embryonic lethal mutants that arrest development prior to hatching and where birefringent material normally present in the gut granule is mislocalized into the intestinal lumen. We will present our phenotypic and genetic analyses of two alleles, kx42 and kx76, which strongly suggest that these mutations are located in a gene(s) not currently known or predicted to function in lysosomal biogenesis in C. elegans.

Marcela Kokes et al. (2008) Development & Evolution Meeting "GLO-3, a Novel Gut Granule Associated Protein, Regulates Gut Granule Formation in C. elegans"

Greg Hermann, Beverley Rabbitts, Steven Levitte, Marcela Kokes

[Development & Evolution Meeting, 2008]

Caenorhabditis elegans intestinal cells are characterized by the presence of gut granules, lysosome-related organelles that contain autofluorescent and birefringent material. Gut granule formation requires the activity of AP-3 subunits, HOPS, and GLO-1/Rab38, genes whose homologues function in trafficking to lysosomes and lysosome-related organelles. To define the molecular and cellular pathways that function in gut granule biogenesis, we have isolated a collection of mutants that lack and/or mislocalize birefringent material into the embryonic intestinal lumen. The glo (gut granule loss) mutants define at least eight different genes. Here we present our phenotypic and molecular analysis of glo-3. We have cloned glo-3 and find that it encodes a novel predicted membrane protein that is associated with gut granules. Interestingly, glo-3(-) alleles fall into three different phenotypic classes based upon the number of birefringent gut granules present within embryonic intestinal cells. "Strong" glo-3(-) alleles completely lack the compartment while "weak" glo-3(-) alleles contain a reduced number of enlarged gut granules. All glo-3(-) alleles contain a reduced number of gut granules at the adult stage. We are using this characteristic of glo-3(-) alleles to identify other pathways that function in gut granule formation.

Liang, Xing et al. (2021) International Worm Meeting "Growth Cone-Localized Microtubule Organizing Center Establishes Microtubule Orientation in Dendrites"

Feldman, Jessica, Fetter, Richard, Kokes, Marcela, Liang, Xing, Shen, Kang, Sallee, Maria, Moore, Adrian

[International Worm Meeting, 2021]

A polarized arrangement of neuronal microtubule arrays is the foundation of membrane trafficking and subcellular compartmentalization. Conserved among both invertebrates and vertebrates, axons contain exclusively "plus-end-out" microtubules while dendrites contain a high percentage of "minus-end-out" microtubules, the origins of which have been a mystery. Here we show that in Caenorhabditis elegans the dendritic growth cone contains a non-centrosomal microtubule organizing center, which generates minus-end-out microtubules along outgrowing dendrites and plus-end-out microtubules in the growth cone. RAB-11-positive endosomes accumulate in this region and co-migrate with the microtubule nucleation complex gamma-TuRC. The MTOC tracks the extending growth cone by kinesin-1/UNC-116-mediated endosome movements on distal plus-end-out microtubules and dynein clusters this advancing MTOC. Critically, perturbation of the function or localization of the MTOC causes reversed microtubule polarity in dendrites. These findings unveil the endosome-localized dendritic MTOC as a critical organelle for establishing axon-dendrite polarity.