Kara Chin et al. (2005) International Worm Meeting "Who needs mitochondrial mtDNA anyway? Fitness effects of the 3.1kb UaDf-5 mtDNA deletion."

Cleonique Deshommes, Aidyl Gonzalez-Serricchio, Craig LaMunyon, Kara Chin

[International Worm Meeting, 2005]

Mitochondrial chromosomes have very little non-coding DNA, and non-mutated chromosomes are generally considered to be associated with increased metabolic fitness. In C. elegans, the UaDf5 mtDNA deletion removes 3.1kb encompassing 11 genes, and yet this deletion can be maternally transmitted for at least 100 generations in a stable heteroplasmic state at all developmental stages (Tsang and Lemire , 2002). Why should a mitochondrial deletion persist? We investigated this question by looking at several measures of metabolism and fitness in relation to the proportion of UaDf-5 deleted mtDNA. Our data support Tsang and Lemires (2002) findings of stable heteroplasmy between wild-type and deleted mtDNA, even though the proportion of deleted mtDNA can vary greatly among siblings and over the course of several generations. We also looked at individual tissues of worms and found no mosaicism among the gut, testes and other tissues for this deletion. We found a positive correlation between the proportion of deleted mtDNA and measures of metabolism (defecation, feeding, and egg-laying rates), indicating that worms bearing this deletion of the mitochondrial chromosome are more fit than wild-type, at least under laboratory conditions.Tsang WY, Lemire BD, 2002. Biochem Cell Biol 80:645-54.

Sailer A et al. (2015) Dev Cell "Dynamic Opposition of Clustered Proteins Stabilizes Cortical Polarity in the C.elegans Zygote."

Munro E, Li Y, Anneken A, Sailer A, Lee S

[Dev Cell, 2015]

Dynamic maintenance of cell polarity is essential for development and physiology. Here we combine experiments and modeling to elucidate mechanisms that maintain cortical polarity in the C.elegans zygote. We show that polarity is dynamically stabilized by two coupled cross-inhibitory feedback loops: one involves the oligomeric scaffold PAR-3 and the kinase PAR-1, and the other involves CDC-42 and its putative GAP CHIN-1. PAR-3 and CDC-42 are both required locally to recruit PAR-6/PKC-3, which inhibits PAR-1 (shown previously) and inhibits local growth/accumulation of CHIN-1 clusters. Conversely, PAR-1 inhibits local accumulation of PAR-3 oligomers, while CHIN-1 inhibits CDC-42 (shown previously), such that either PAR-1 or CHIN-1 can prevent recruitment of PAR-6/PKC-3, but loss of both causes complete loss of polarity. Ultrasensitive dependence of CHIN-1 cluster growth on PAR-6/PKC-3 endows this core circuit with bistable dynamics, while transport of CHIN-1 clusters by cortical flow can stabilize the AP boundary against diffusive spread of PAR-6/PKC-3.

Katewa SD et al. (2014) Cell Metab "Mitobolites: the elixir of life."

Katewa SD, Kapahi P, Khanna A

[Cell Metab, 2014]

One of the biggest challenges in biology is to understand how mitochondria influence aging and age-related diseases. Chin et al. (2014) reveal how a mitochondrial metabolite (mitobolite) inhibits mitochondrial ATPase and extends lifespan by mimicking dietary restriction in worms.

Kumfer KT et al. (2010) Mol Biol Cell "CGEF-1 and CHIN-1 regulate CDC-42 activity during asymmetric division in the Caenorhabditis elegans embryo."

Squirrell JM, O'Connell KF, Eliceiri KW, Peel N, Cook SJ, White JG, Kumfer KT

[Mol Biol Cell, 2010]

The anterior-posterior axis of the Caenorhabditis elegans embryo is elaborated at the one-cell stage by the polarization of the partitioning (PAR) proteins at the cell cortex. Polarization is established under the control of the Rho GTPase RHO-1 and is maintained by the Rho GTPase CDC-42. To understand more clearly the role of the Rho family GTPases in polarization and division of the early embryo, we constructed a fluorescent biosensor to determine the localization of CDC-42 activity in the living embryo. A genetic screen using this biosensor identified one positive (putative guanine nucleotide exchange factor [GEF]) and one negative (putative GTPase activating protein [GAP]) regulator of CDC-42 activity: CGEF-1 and CHIN-1. CGEF-1 was required for robust activation, whereas CHIN-1 restricted the spatial extent of CDC-42 activity. Genetic studies placed CHIN-1 in a novel regulatory loop, parallel to loop described previously, that maintains cortical PAR polarity. We found that polarized distributions of the nonmuscle myosin NMY-2 at the cell cortex are independently produced by the actions of RHO-1, and its effector kinase LET-502, during establishment phase and CDC-42, and its effector kinase MRCK-1, during maintenance phase. CHIN-1 restricted NMY-2 recruitment to the anterior during maintenance phase, consistent with its role in polarizing CDC-42 activity during this phase.

Rapti G et al. (2017) Nat Neurosci "Glia initiate brain assembly through noncanonical Chimaerin-Furin axon guidance in C. elegans."

Shan A, Shaham S, Li C, Lu Y, Rapti G

[Nat Neurosci, 2017]

Brain assembly is hypothesized to begin when pioneer axons extend over non-neuronal cells, forming tracts guiding follower axons. Yet pioneer-neuron identities, their guidance substrates, and their interactions are not well understood. Here, using time-lapse embryonic imaging, genetics, protein-interaction, and functional studies, we uncover the early events of C. elegans brain assembly. We demonstrate that C. elegans glia are key for assembly initiation, guiding pioneer and follower axons using distinct signals. Pioneer sublateral neurons, with unique growth properties, anatomy, and innervation, cooperate with glia to mediate follower-axon guidance. We further identify a Chimaerin (CHIN-1)- Furin (KPC-1) double-mutant that severely disrupts assembly. CHIN-1 and KPC-1 function noncanonically, in glia and pioneer neurons, for guidance-cue trafficking. We exploit this bottleneck to define roles for glial Netrin and Semaphorin in pioneer- and follower-axon guidance, respectively, and for glial and pioneer-neuron Flamingo (CELSR) in follower-axon navigation. Taken together, our studies reveal previously undescribed glial roles in pioneer-axon guidance, suggesting conserved principles of brain assembly.

Kaul, Samiksha et al. (2022) MicroPubl Biol

Chou, Han Ting, Charles, Seleipiri, Aubry, Guillaume, Lu, Hang, Kaul, Samiksha, Paaby, Annalise B.

[MicroPubl Biol, 2022]

Wild C. elegans strains harbor natural variation in developmental pathways, but investigating these differences requires precise and well-powered phenotyping methods. Here we employ a microfluidics platform for single-molecule FISH to simultaneously visualize the transcripts of three genes in embryos of two distinct strains. We capture transcripts at high resolution by developmental stage in over one hundred embryos of each strain and observe wide-scale conservation of expression, but subtle differences in par-2 and chin-1 abundance and rate of change. As both genes reside in a genomic interval of hyper-divergence, these results may reflect consequences of pathway evolution over long timescales.

Papp, Andy et al. (2009) International Worm Meeting "Investigation of Low-cost GFP Microscopy."

Papp, Andy, Aldrich, Chris, Bangalore, Srikanth, Perry, David

[International Worm Meeting, 2009]

The Green Fluorescent Protein (GFP) gene from the fluorescent jellyfish Aequorea victoria, and its variants (such as EGFP), are used extensively to study the location and timing of gene expression in transgenic animals and plants (Chalfie et al, 1994). Resultant GFP fusion proteins are especially well-suited to studying in vivo gene expression patterns in the transparent nematode, C. elegans and the transparent larva of the fly D. melanogaster. Perhaps one of the most significant limitations to its use in large-scale genetic screens is the high cost of equipment needed to observe GFP microscopically - namely the Fluorescence Dissecting Stereomicroscope for screening and picking mutants and upright and inverted epi-fluorescent compound microscopes for more detailed studies. Commercially available Fluorescence Dissecting Stereomicroscopes typically sell in the midrange between US$10,000 and US$20,000. They are offered by only the "high-end" microscope companies, based upon their most expensive dissecting scopes, and incorporate their premium-priced mercury arc-lamp illuminators, power supplies and epi-fluorescence modules. This leads us to wonder whether it is possible to cut corners without sacrificing utility, and which corners can be cut. Since the inception of GFP-based expression screens, a variety of researchers have produced custom-made and home-made GFP dissecting scopes. These include, for example, Welcome Bender (Harvard Medical School, pers. comm.) and Ian Chin-Sang (Chin-Sang, 2004). There are several possibilities to consider toward lowering the cost of a Fluorescence Dissecting Stereomicroscope. It may be possible to get sufficient light from relatively inexpensive, long-lived, lower-power-consuming Light Emitting Diodes (LEDs) vs. mercury arc lamps. Depending upon the spectral specificity of the LEDs, filters or dichroic mirrors might be omitted. Getting enough light intensity of the precise wavelengths that excite GFP fluorescence focused onto the sample is important. The exciting beam can be provided directly or focused backward through the microscope using "epi-illumination". We will explore these possibilities and report (and possibly demonstrate) the results. Chin-Sang, Ian. (2004) GFP Stereoscope Using LED light source. Queen''s University, Kingston, ON, Canada. http://130.15.90.245/gfp_stereoscope.htm.

Martin L Hudson et al. (2003) International Worm Meeting "Functions of ephrins in embryonic and post-embryonic development: exploring connections with Kallman syndrome protein and cadherins"

Andrew D Chisholm, Martin L Hudson

[International Worm Meeting, 2003]

During C. elegans gastrulation, embryonic cells rearrange to form tissue layers. Endodermal and mesodermal cells move into the interior of the embryo, leaving a transient ventral cleft that is sealed up by the short-range movements of ventral neuroblasts. These ventral neuroblasts and their progeny provide the substrate for the subsequent enclosure movements of the epidermis. Mutants with abnormal ventral neuroblast movements display enlarged ventral clefts that later result in epidermal enclosure defects. Previous work in our lab showed that signaling via the C. elegans Eph receptor VAB-1 and its ephrin ligand EFN-1/VAB-2 regulate neuroblast movements at the end of gastrulation (George et al. 1998; Chin-Sang et al. 1999). The divergent ephrin EFN-4 is also required for neuroblast movements but appears to function independently of the VAB-1 receptor (Chin-Sang et al. 2002). A third pathway is defined by the LAR-like receptor phosphotyrosine phosphatase PTP-3 (Harrington et al. 2002). These pathways appear to play related and partly redundant roles in ventral neuroblast movements.We have examined whether other mutants with epidermal morphogenesis phenotypes affect neuroblast movements and have used double mutant analysis to determine if these genes might define new pathways or can be placed in the VAB-1/EFN-4/PTP-3 pathways. KAL-1 is the C. elegans homolog of human Kallman syndrome protein, anosmin-1 (Rugarli et al. 2002). A kal-1 mutation displays low penetrance defects in epidermal morphogenesis. Using 4-D analysis, we find that kal-1 mutants display delayed closure of the ventral cleft. We also find that a kal-1 mutation enhances the morphogenetic phenotypes of all mutants tested (vab-1(null), efn null mutations and ptp-3), suggesting that KAL-1 may define a separate signaling pathway. We are also studying the post-embryonic functions of ephrins. EFN-4 is expressed in the primary cells of the developing vulva (Hudson and Chisholm, 2002 WCWM, abstract 144). efn-4 mutants display very low penetrance defects in vulval morphogenesis and induction. The cadherin CDH-3 is also expressed in vulval cells (Pettit et al. 1996). A cdh-3 mutation causes epidermal morphogenesis defects (6) reminiscent of those in weak efn-4 mutants. We find that the cdh-3 mutation does not enhance efn-4(null) mutant phenotypes but significantly enhances efn-1(null) mutant phenotypes, suggestive of a role for cdh-3 in efn-4 signaling. Further analysis of the phenotypes will be presented.

Vivegananthan U et al. (1997) International C. elegans Meeting "ANALYSIS OF FEM-3 PROTEIN INTERACTIONS"

Spence AM, Vivegananthan U

[International C. elegans Meeting, 1997]

Male development in C. elegans depends on the activities of the three fem genes. Conversely, female development requires that fem activity be negatively regulated. We are interested in how the products of the fem genes function and how their activity is regulated. We have previously presented evidence that the negative regulation of fem activity in XX somatic tissues depends upon a protein-protein interaction between FEM-3 and the cytoplasmic domain of the transmembrane protein, TRA-2A (Spence et al., 1995 C. elegans meeting). FEM-3 also associates with FEM-2, and we predict that this association is important for the specification of male fates (Chin-Sang and Spence, 1996. Genes Dev. 10: 2314-25.). We wish to define the domains in FEM-3 responsible for each interaction and to establish the significance of both interactions. Deletion analysis in the yeast two-hybrid system identifies two regions required for interaction with FEM-2 but not with TRA-2A. We have modified the yeast two-hybrid system to screen for fem-3 mutations that selectively disrupt the FEM-3/FEM-2 or the FEM-2/TRA-2A interaction. We will test the resulting mutant proteins for their ability to promote male development and their sensitivity to regulation by TRA-2A.

Beatty A et al. (2013) Development "PAR-2, LGL-1 and the CDC-42 GAP CHIN-1 act in distinct pathways to maintain polarity in the C. elegans embryo."

Beatty A, Morton DG, Kemphues K

[Development, 2013]

In the one-cell C. elegans embryo, polarity is maintained by mutual antagonism between the anterior cortical proteins PAR-3, PKC-3, PAR-6 and CDC-42, and the posterior cortical proteins PAR-2 and LGL-1 on the posterior cortex. The mechanisms by which these proteins interact to maintain polarity are incompletely understood. In this study, we investigate the interplay among PAR-2, LGL-1, myosin, the anterior PAR proteins and CDC-42. We find that PAR-2 and LGL-1 affect cortical myosin accumulation by different mechanisms. LGL-1 does not directly antagonize the accumulation of cortical myosin and instead plays a role in regulating PAR-6 levels. By contrast, PAR-2 likely has separate roles in regulating cortical myosin accumulation and preventing the expansion of the anterior cortical domain. We also provide evidence that asymmetry of active CDC-42 can be maintained independently of LGL-1 and PAR-2 by a redundant pathway that includes the CDC-42 GAP CHIN-1. Finally, we show that, in addition to its primary role in regulating the size of the anterior cortical domain via its binding to PAR-6, CDC-42 has a secondary role in regulating cortical myosin that is not dependent on PAR-6.