Schlientz, A. et al. (2017) International Worm Meeting "Exploring the role of CLASPCLS-2 in oocyte meiotic spindle assembly and bipolarity."

Schlientz, A., Bowerman, B.

[International Worm Meeting, 2017]

Oocyte meiotic spindles assemble in the absence centrosomes, which provide microtubule nucleation and establish bipolarity during mitotic and sperm meiotic spindle assembly. This phenomenon begs the question, what factors are required for establishing/maintaining oocyte meiotic spindle bipolarity given the absence of centrosomes? To enhance our understanding of spindle assembly in the absence of centrosomes, we are investigating the role of the C. elegans CLASP family member CLS-2 in oocyte meiotic spindle assembly. Studies of CLASP family members indicate that these proteins promote microtubule stability by preventing microtubule depolymerization, but how they contribute to oocyte meiotic spindle assembly remains poorly understood.1 To better examine the role of CLASPCLS-2 in oocyte meiotic spindle assembly, we have used CRISPR/Cas9 to generate putative CLS-2 null-alleles. These new alleles show both the previously reported mitotic defects via Nomarski DIC microscopy, as well as occasional instances of multiple maternal pronuclei - a phenotype associated with defects in oocyte meiotic spindle assembly that has not been previously reported after cls-2(RNAi). Using spinning disk confocal microscopy, we have also observed the previously reported oocyte meiotic chromosome segregation defects.2 Loss of CLS-2 in oocytes results in the formation of highly aberrant spindles lacking distinct bipolarity, which fail to segregate chromosomal masses during both meiosis I and II. Intriguingly, the membrane ingression normally observed during polar body extrusion appears to be absent in our CLS-2 mutants, and polar body extrusion may be completely absent. This is in contrast to several other oocyte spindle assembly defective mutants, in which membrane ingression occurs even if polar body extrusion is abnormal to varying degrees. These preliminary results indicate that CLS-2 may play important roles in both spindle assembly and polar body extrusion. We are characterizing both processes in more detail to better define the requirements for CLS-2 during oocyte meiotic spindle assembly. 1. Al-Bassam, J. & Chang, F. Regulation of microtubule dynamics by TOG-domain proteins XMAP215/Dis1 and CLASP. Trends Cell Biol 21, 604-614 (2011). 2. Dumont, J. & Desai, A. Acentrosomal spindle assembly and chromosome segregation during oocyte meiosis. Trends Cell Biol 22, 241-249 (2012).

Schlientz, A. et al. (2019) International Worm Meeting "Using spindle assembly defective mutants to investigate polar body extrusion during oocyte meiosis."

Bowerman, B., Schlientz, A.

[International Worm Meeting, 2019]

During oocyte meiotic cell division, discarded chromosomes are extruded into small polar bodies. However, the cues that mediate polar body extrusion are not well understood. To gain insight, we are investigating the relationship between oocyte meiotic spindle assembly and polar body extrusion. We have begun by exploring the role of CLS-2, a C. elegans CLASP family member, and are comparing its spindle assembly and polar body extrusion defects to those in mei-1/Katanin and klp-18/kinesin 12 mutants. Previous studies of CLASP family proteins indicate that they function to promote microtubule stability and may be important for regulating interactions between the microtubule and actin cytoskeletons, but how they contribute to polar body extrusion remains unknown. We used CRISPR/Cas9 to generate putative cls-2 null alleles, and live imaging with fluorescent protein fusions to assess CLS-2/CLASP requirements. As others have reported, cls-2(-) mutants have chromosome segregation defects during oocyte meiosis. In addition, we have found that microtubule levels are reduced, and the mutant oocytes fail to assemble bipolar spindles. Intriguingly, ~85% of cls-2(-) oocytes fail to extrude a polar body during meiosis I (n=69) and exhibit increased levels of global cortical furrowing compared to wild type. Moreover, based on live imaging of NMY-2/non-muscle myosin and ANI-1/anillin, the polar body contractile ring structure appears fragmented and discontinuous in cls-2(-) mutants. Similar to cls-2(-) oocytes, mei-1 and klp-18 mutant oocytes fail to segregate chromosomes, and mei-1/Katanin mutants also frequently fail to extrude a polar body during meiosis I (85%, n=14) although global cortical furrowing appears normal. In contrast, oocytes depleted of klp-18/kinesin 12 usually do extrude polar bodies (20% failure in meiosis I, n = 10) and also have more normal global cortical furrowing. We are currently analyzing furrowing dynamics and contractile ring and spindle components to further compare spindle assembly and polar body extrusion defects in these mutants. We anticipate that such a comparative analysis will provide insight into the cues that mediate polar body extrusion during oocyte meiotic cell division.

Schlientz AJ et al. (2020) PLoS Genet "C. elegans CLASP/CLS-2 negatively regulates membrane ingression throughout the oocyte cortex and is required for polar body extrusion."

Schlientz AJ, Bowerman B

[PLoS Genet, 2020]

The requirements for oocyte meiotic cytokinesis during polar body extrusion are not well understood. In particular, the relationship between the oocyte meiotic spindle and polar body contractile ring dynamics remains largely unknown. We have used live cell imaging and spindle assembly defective mutants lacking the function of CLASP/CLS-2, kinesin-12/KLP-18, or katanin/MEI-1 to investigate the relationship between meiotic spindle structure and polar body extrusion in C. elegans oocytes. We show that spindle bipolarity and chromosome segregation are not required for polar body contractile ring formation and chromosome extrusion in klp-18 mutants. In contrast, oocytes with similarly severe spindle assembly defects due to loss of CLS-2 or MEI-1 have penetrant and distinct polar body extrusion defects: CLS-2 is required early for contractile ring assembly or stability, while MEI-1 is required later for contractile ring constriction. We also show that CLS-2 both negatively regulates membrane ingression throughout the oocyte cortex during meiosis I, and influences the dynamics of the central spindle-associated proteins Aurora B/AIR-2 and MgcRacGAP/CYK-4. We suggest that proper regulation by CLS-2 of both oocyte cortical stiffness and central spindle protein dynamics may influence contractile ring assembly during polar body extrusion in C. elegans oocytes.

Quartey MO et al. (2021) Sci Rep "The A(1-38) peptide is a negative regulator of the A(1-42) peptide implicated in Alzheimer disease progression."

Pennington PR, Heistad RM, Nyarko JNK, Barnes JR, Bolanos MAC, Parsons MP, Knudsen KJ, De Carvalho CE, Leary SC, Mousseau DD, Buttigieg J, Maley JM, Quartey MO

[Sci Rep, 2021]

The pool of -Amyloid (A) length variants detected in preclinical and clinical Alzheimer disease (AD) samples suggests a diversity of roles for A peptides. We examined how a naturally occurring variant, e.g. A(1-38), interacts with the AD-related variant, A(1-42), and the predominant physiological variant, A(1-40). Atomic force microscopy, Thioflavin T fluorescence, circular dichroism, dynamic light scattering, and surface plasmon resonance reveal that A(1-38) interacts differently with A(1-40) and A(1-42) and, in general, A(1-38) interferes with the conversion of A(1-42) to a -sheet-rich aggregate. Functionally, A(1-38) reverses the negative impact of A(1-42) on long-term potentiation in acute hippocampal slices and on membrane conductance in primary neurons, and mitigates an A(1-42) phenotype in Caenorhabditis elegans. A(1-38) also reverses any loss of MTT conversion induced by A(1-40) and A(1-42) in HT-22 hippocampal neurons and APOE 4-positive human fibroblasts, although the combination of A(1-38) and A(1-42) inhibits MTT conversion in APOE 4-negative fibroblasts. A greater ratio of soluble A(1-42)/A(1-38) [and A(1-42)/A(1-40)] in autopsied brain extracts correlates with an earlier age-at-death in males (but not females) with a diagnosis of AD. These results suggest that A(1-38) is capable of physically counteracting, potentially in a sex-dependent manner, the neuropathological effects of the AD-relevant A(1-42).

Danielle Thierry-Mieg et al. (2003) Worm Breeder's Gazette "www.wormgenes.org , a new gene centered database"

Vahan Simonyan, Michel Potdevin, Mark Sienkiewicz, Yuji KOHARA, Jean Thierry-Mieg, Danielle Thierry-Mieg, Tadasu SHIN-I

[Worm Breeder's Gazette, 2003]

Wormgenes is a new resource for C.elegans offering a detailed summary about each gene and a powerful query system.

Tangrodchanapong T et al. (2020) Front Pharmacol "Frondoside A Attenuates Amyloid- Proteotoxicity in Transgenic Caenorhabditis elegans by Suppressing Its Formation."

Tangrodchanapong T, Sobhon P, Meemon K

[Front Pharmacol, 2020]

Oligomeric assembly of Amyloid- (A) is the main toxic species that contribute to early cognitive impairment in Alzheimer's patients. Therefore, drugs that reduce the formation of A oligomers could halt the disease progression. In this study, by using transgenic <i>Caenorhabditis elegans</i> model of Alzheimer's disease, we investigated the effects of frondoside A, a well-known sea cucumber <i>Cucumaria frondosa</i> saponin with anti-cancer activity, on A aggregation and proteotoxicity. The results showed that frondoside A at a low concentration of 1 M significantly delayed the worm paralysis caused by A aggregation as compared with control group. In addition, the number of A plaque deposits in transgenic worm tissues was significantly decreased. Frondoside A was more effective in these activities than ginsenoside-Rg3, a comparable ginseng saponin. Immunoblot analysis revealed that the level of small oligomers as well as various high molecular weights of A species in the transgenic <i>C. elegans</i> were significantly reduced upon treatment with frondoside A, whereas the level of A monomers was not altered. This suggested that frondoside A may primarily reduce the level of small oligomeric forms, the most toxic species of A. Frondoside A also protected the worms from oxidative stress and rescued chemotaxis dysfunction in a transgenic strain whose neurons express A. Taken together, these data suggested that low dose of frondoside A could protect against A-induced toxicity by primarily suppressing the formation of A oligomers. Thus, the molecular mechanism of how frondoside A exerts its anti-A aggregation should be studied and elucidated in the future.

Hodgkin JA (1998) International Journal of Developmental Biology "Seven types of pleiotropy."

Hodgkin JA

[International Journal of Developmental Biology, 1998]

Pleiotropy , a situation in which a single gene influences multiple phenotypic tra its, can arise in a variety of ways. This paper discusses possible underlying mechanisms and proposes a classification of the various phenomena involved.

Tuck S (2011) Curr Biol "Extracellular vesicles: budding regulated by a phosphatidylethanolamine translocase."

Tuck S

[Curr Biol, 2011]

Recent work on a Caenorhabditis elegans transmembrane ATPase reveals a central role for the aminophospholipid phosphatidylethanolamine in the production of a class of extracellular vesicles.

Viney ME et al. (2004) Naturwissenschaften "Is dauer pheromone of Caenorhabditis elegans really a pheromone?"

Viney ME, Franks NR

[Naturwissenschaften, 2004]

Animals respond to signals and cues in their environment. The difference between a signal (e.g. a pheromone) and a cue (e.g. a waste product) is that the information content of a signal is subject to natural selection, whereas that of a cue is not. The model free-living nematode Caenorhabditis elegans forms an alternative developmental morph (the dauer larva) in response to a so-called 'dauer pheromone', produced by all worms. We suggest that the production of 'dauer pheromone' has no fitness advantage for an individual worm and therefore we propose that 'dauer pheromone' is not a signal, but a cue. Thus, it should not be called a pheromone.

Schaeffer JM et al. (1990) J Antibiot (Tokyo) "Cochlioquinone A, a nematocidal agent which competes for specific [3H]ivermectin binding sites."

Williamson JM, Schaeffer JM, Bergstrom AR, Liesch JM, Goetz MA, Frazier EG

[J Antibiot (Tokyo), 1990]

Cochlioquinone A, isolated from the fungus Helminthosporium sativum, was found to have nematocidal activity. Cochlioquinone A is a competitive inhibitor of specific [3H]ivermectin binding suggesting that cochlioquinone A and ivermectin interact with the same membrane receptor.