Cecchetelli AD et al. (2017) Mech Dev "Regulating distal tip cell migration in space and time."

Cram EJ, Cecchetelli AD

[Mech Dev, 2017]

Gonad morphogenesis in the nematode C. elegans is guided by two leader cells, the distal tip cells (DTC). The DTCs migrate along a stereotyped path, executing two 90 turns before stopping at the midpoint of the animal. This migratory path determines the double-U shape of the adult gonad, therefore, the path taken by the DTCs can be inferred from the final shape of the organ. In this review, we focus on the mechanism by which the DTC executes the first 90 turn from the ventral to dorsal side of the animal, and how it finds its correct stopping place at the midpoint of the animal. We discuss the role of heterochronic genes in coordinating DTC migration with larval development, the role of feedback loops and miRNA regulation in phenotypic robustness, and the role of RNA binding proteins in the cessation of DTC migration.

Cecchetelli, Alyssa D et al. (2015) International Worm Meeting "RHO-1 is required for normal oocyte transit through the spermatheca."

Cecchetelli, Alyssa D, Cram, Erin J

[International Worm Meeting, 2015]

Mechanotransduction, converting a mechanical signal into a biochemical response, is vital for proper development, tissue function and homeostasis of biological tubes. Defects in a cell's ability to sense and respond to external stimuli can lead to complications and diseases such as asthma, atherosclerosis and cancer. The C. elegans spermatheca, the site of fertilization within the worm, provides an ideal in vivo model to study this biological process. Stretch of the incoming oocyte is converted into waves of calcium potentiated by PLC-1 that culminates in acto-myosin contractility and expulsion of fertilized embryos into the uterus. Loss of functional PLC-1 results in trapping of embryos within the spermatheca due to a lack of calcium signaling within the tissue. What remains unknown however, is what proteins act up or downstream of PLC-1 in the mechanotransduction pathway. One possible regulator is the small GTPase RHO-1. RHO-1 overexpression using a gain of function (gf) allele results in a highly constricted spermathecae and rapid transit, similar to loss of SPV-1, a recently identified GTPase-activating protein (GAP). Conversely, RHO-1 depletion via RNAi leads to embryos that become trapped in the spermatheca and/or worms that exhibit abnormal ovulations, where incoming oocytes are pinched in half upon entry. Preliminary evidence shows that RHO-1 has an affect on proper calcium oscillations, providing evidence that RHO-1 may be acting upstream of PLC-1. PLC-1 interestingly contains a unique RHO-1 interaction domain in addition to a CDC25 RAS guanine nucleotide exchange factor (GEF), EF hand, and RAS association domains. A structure function analysis of PLC-1 is in progress to determine the role of each PLC-1 domain in oocyte transit through the spermatheca. Although the presence of a unique RHO-1 interaction site suggests RHO-1 as a direct regulator, preliminary evidence does not support this hypothesis. It is possible that RHO-1 is indirectly regulating PLC-1 activity and subsequently calcium release. Given the conservation of PLC-1, RHO-1 and the identified mechanotransduction pathway that controls C. elegans ovulation, this work will provide insights into the biological mechanisms required to convert a mechanical stimulus into a biochemical response.

Cecchetelli AD et al. (2016) Dev Biol "CACN-1 is required in the Caenorhabditis elegans somatic gonad for proper oocyte development."

Tannoury H, Cram EJ, Hugunin J, Cecchetelli AD

[Dev Biol, 2016]

CACN-1/Cactin is a conserved protein identified in a genome-wide screen for genes that regulate distal tip cell migration in the nematode Caenorhabditis elegans. In addition to possessing distal tip cells that migrate past their correct stopping point, animals depleted of cacn-1 are sterile. In this study, we show that CACN-1 is needed in the soma for proper germ line development and maturation. When CACN-1 is depleted, sheath cells are absent and/or abnormal. When sheath cells are absent, hermaphrodites produce sperm, but do not switch appropriately to oocyte production. When sheath cells are abnormal, some oocytes develop but are not successfully ovulated and undergo endomitotic reduplication (Emo). Our previous proteomic studies show that CACN-1 interacts with a network of splicing factors. Here, these interactors were screened for germ line phenotypes using RNAi. Depletion of many of these factors led to missing or abnormal sheath cells and germ line defects, particularly absent and/or Emo oocytes. These results suggest CACN-1 is part of a protein network that influences somatic gonad development and function through alternative splicing or post-transcriptional gene regulation.

Cecchetelli, Alyssa D. et al. (2017) International Worm Meeting "A novel role for heterotrimeric G protein alpha subunits in C. elegans ovulation."

Cecchetelli, Alyssa D., Cram, Erin J.

[International Worm Meeting, 2017]

Mechanotransduction, converting a mechanical signal into a biochemical response, is vital for proper development, tissue function and homeostasis. Defects in a cell's ability to sense and respond to external stimuli can lead to complications in development and diseases such as asthma. The C. elegans spermatheca, the site of fertilization, provides an ideal in vivo model to study this biological process. Stretch of the incoming oocyte is converted into waves of calcium potentiated by PLC-1 that culminates in acto-myosin contractility and expulsion of fertilized embryos into the uterus. What remains unknown however, is what activates PLC-1. Loss of functional PLC-1 results in trapping of embryos within the spermatheca due to a lack of calcium signaling within the tissue. To identify potential activators of PLC-1, we conducted a candidate RNAi screen and identified two heterotrimeric G protein alpha subunits, GOA-1 (Gi/Go class) and GSA-1 (Gs class) as essential for proper oocyte transit through the spermatheca. Depletion of goa-1 via RNAi and a loss of function allele result in a significant increase in the number of embryos occupying spermathecae compared to wild type animals. Further analysis revealed that this increase in occupied spermathecae coincides with abnormal calcium signaling and extremely long embryo transits through the spermatheca, resulting in a significant reduction in broodsize. Depletion of gsa-1 via RNAi results in trapping of embryos in the spermatheca due to a lack of calcium signaling in the spermathecal bag comparable to the loss of plc-1. These results provide novel evidence that heterotrimeric G protein signaling may play an essential role in the stimulation of calcium signaling perhaps through the regulation of phospholipases like PLC-1. Given the conservation of PLC-1, GOA-1, GSA-1 and the pathway that regulates C. elegans ovulation, this work should provide insights into stretch activation of phospholipase signaling in vivo.

Castaneda, P.G. et al. (2019) International Worm Meeting "KIN-1/PKA affects calcium signaling and actomyosin contractility in the C. elegans spermatheca."

Cram, E.J., Cecchetelli, A., Castaneda, P.G.

[International Worm Meeting, 2019]

The Caenorhabditis elegans (C. elegans) spermatheca, the site for embryo fertilization, is a tube composed of a single layer of cells that undergo cyclic stretching, constriction, and relaxation as ~150 oocytes pass through the gonad and into the spermatheca. The spermatheca consists of the distal neck, the bag, and the spermatheca-uterine (sp-ut) valve. Immediately after oocyte entry, the sp-ut valve constricts. After ~10 minutes, the bag begins to constrict, and the valve relaxes allowing the fertilized embryo to exit the spermatheca and enter the uterus. Upon oocyte entry, the phospholipase PLC-1 is activated and inositol trisphosphate (IP3) and diacylglycerol (DAG) are produced. IP3 signals the release of calcium from the ER, which, coupled with Rho signaling and myosin activation, ultimately results in cell contraction in the spermathecal bag. 3'-5'-Cyclic adenosine monophosphate (cAMP) is a fundamental secondary messenger responsible for signaling numerous diverse biological processes, including cell contractility and relaxation. Targets of cAMP include the cAMP-dependent protein kinase KIN-1/PKA. We have identified a signaling pathway that activates PKA as a regulator of spermathecal contractility. The pathway includes GSA-1 a G-protein alpha subunit of the Gs class, ACY-4 adenylyl cyclase, KIN-1/PKA and KIN-2 the regulatory subunit of PKA. Depletion of GSA-1 and KIN-1 during ovulation events results in the inability of embryos to exit the spermatheca. KIN-1 is necessary for the formation of contractile acto-myosin bundles, suggesting cAMP signaling affects actomyosin contractility. Using GCaMPv3, a genetically encoded calcium sensor, we observed that expressing GSA-1(GF) or treating animals with kin-2 RNAi results in the initiation of calcium signaling in the spermatheca in the absence of oocyte entry, something we have never observed in WT animals. In summary, we present data that shows cAMP signaling plays a role in the spermatheca through PKA, can dramatically affect calcium signaling, and is able to alter actomyosin contractility.

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.