Cohen SM et al. (2022) G3 (Bethesda) "Formation and Function of Dauer Ascarosides in the Nematodes C. briggsae and C. elegans."

Sternberg PW, Schroeder FC, Wrobel CJJ, Prakash SJ, Cohen SM

[G3 (Bethesda), 2022]

The biosynthetic pathways and functions of ascaroside signaling molecules in the nematode Caenorhabditis elegans have been studied in order to better understand complex, integrative developmental decision-making. Although it is known that ascarosides play multiple roles in the development and behavior of nematode species other than C. elegans, these parallel pheromone systems have not been well-studied. Here, we show that ascarosides in the nematode Caenorhabditis briggsae are biosynthesized in the same manner as C. elegans and act to induce the alternative developmental pathway that generates the stress-resistant dauer lifestage. We show that ascr#2 is the primary component of crude dauer pheromone in C. briggsae; in contrast, C. elegans dauer pheromone relies on a combination of ascr#2, ascr#3, and several other components. We further demonstrate that Cbr-daf-22, like its C. elegans ortholog Cel-daf-22, is necessary to produce short-chain ascarosides. Moreover, Cbr-daf-22 and Cel-daf-22 mutants produce an ascaroside-independent metabolite that acts antagonistically to crude dauer pheromone and inhibits dauer formation.

Cohen SM et al. (2015) Biochem Biophys Res Commun "Evolutionary and functional perspectives on signaling from neuronal surface to nucleus."

Li B, Cohen SM, Ma H, Tsien RW

[Biochem Biophys Res Commun, 2015]

Reliance on Ca(2+) signaling has been well-preserved through the course of evolution. While the complexity of Ca(2+) signaling pathways has increased, activation of transcription factors including CREB by Ca(2+)/CaM-dependent kinases (CaMKs) has remained critical for long-term plasticity. In C. elegans, the CaMK family is made up of only three members, and CREB phosphorylation is mediated by CMK-1, the homologue of CaMKI. CMK-1 nuclear translocation directly regulates adaptation of thermotaxis behavior in response to changes in the environment. In mammals, the CaMK family has been expanded from three to ten members, enabling specialization of individual elements of a signal transduction pathway and increased reliance on the CaMKII subfamily. This increased complexity enables private line communication between Ca(2+) sources at the cell surface and specific cellular targets. Using both new and previously published data, we review the mechanism of a CaMKII-CaM nuclear translocation. This intricatepathway depends on a specific role for multiple Ca(2+)/CaM-dependent kinases and phosphatases: /CaMKII phosphorylates CaMKII to trap CaM; CaN dephosphorylates CaMKII to dispatch it to the nucleus; and PP2A induces CaM release from CaMKII so that CaMKK and CaMKIV can trigger CREB phosphorylation. Thus, while certain basic elements have been conserved from C. elegans, evolutionary modifications offer opportunities for targeted communication, regulation of key nodes and checkpoints, and greater specificity and flexibility in signaling.

Huitema K et al. (2004) EMBO J "Identification of a family of animal sphingomyelin synthases."

van den Dikkenberg J, Holthuis JC, Brouwers JF, Huitema K

[EMBO J, 2004]

Sphingomyelin (SM) is a major component of animal plasma membranes. Its production involves the transfer of phosphocholine from phosphatidylcholine onto ceramide, yielding diacylglycerol as a side product. This reaction is catalysed by SM synthase, an enzyme whose biological potential can be judged from the roles of diacylglycerol and ceramide as anti- and proapoptotic stimuli, respectively. SM synthesis occurs in the lumen of the Golgi as well as on the cell surface. As no gene for SM synthase has been cloned so far, it is unclear whether different enzymes are present at these locations. Using a functional cloning strategy in yeast, we identified a novel family of integral membrane proteins exhibiting all enzymatic features previously attributed to animal SM synthase. Strikingly, human, mouse and Caenorhabditis elegans genomes each contain at least two different SM synthase (SMS) genes. Whereas human SMS1 is localised to the Golgi, SMS2 resides primarily at the plasma membrane. Collectively, these findings open up important new avenues for studying sphingolipid function in animals.

Barbee SA et al. (2006) Dev Biol "The Sm proteins regulate germ cell specification during early C. elegans embryogenesis."

Barbee SA, Evans TC

[Dev Biol, 2006]

Sm and Sm-like proteins are core components of the splicesome but have other functions distinct from pre-mRNA processing. Here, we show that Sm proteins also regulate germ cell specification during early C. elegans embryogenesis. SmE and SmG were required to maintain transcriptional quiescence in embryonic germ cell precursors. In addition, depletion of SmE inhibited expression of the germ lineage-specific proteins PIE-1, GLD-1, and NOS-2, but did not affect maintenance of several maternal mRNAs. PIE-1 had previously been shown to activate transcriptional silencing and NOS-2 expression. We found that PIE-1 also promotes GLD-1 expression by a process that is independent of transcriptional silencing. Thus, Sm proteins could control transcriptional silencing and maternal protein expression by regulating PIE-1. However, loss of SmE function also caused defects in P granule localization and premature division in early germline blastomeres, processes that are independent of PIE-1 function. Therefore, the Sm proteins control multiple aspects of germ cell precursor development. Because depletion of several other core splicing factors did not affect these events, these Sm functions are likely distinct from pre-mRNA splicing. Sm family proteins assemble into ribonucleoprotein complexes (RNPs) that control RNA activities. We suggest that novel Sm RNPs directly or indirectly influence posttranscriptional control of maternal mRNAs to promote germ cell specification in the early C. elegans embryo.

Peg MacMorris et al. (2007) International Worm Meeting "A novel family of C. elegans snRNPs contains proteins associated with trans-splicing."

Erika Lasda, Alison Larsen, Brian Kraemer, Tom Blumenthal, Madhur Kumar, Peg MacMorris

[International Worm Meeting, 2007]

In approximately 70% of C. elegans pre-mRNAs, the RNA sequence between the 5 cap and the first 3 splice site is replaced by trans-splicing a short spliced leader (SL) from the Sm snRNP, SL1. C. elegans also utilizes a similar Sm snRNP, SL2, to trans-splice at sites between genes in polycistronic pre-mRNAs from operons. How do SL1 and SL2 snRNPs function in different contexts? Here we show that the SL1 snRNP contains a complex of SL75p and SL21p, homologs of novel proteins previously reported in the Ascaris SL snRNP. Interestingly, the SL2 snRNP does not contain either of these proteins. However, SL75p and SL26p, a paralog of SL21p, are components of another Sm snRNP that contains a novel snRNA species, Sm Y. Knockdown of SL75p is lethal. However, knockdown of either SL21p or SL26p alone leads to cold-sensitive sterility, whereas knockdown of both SL21p and SL26p is lethal. This suggests that these two proteins have overlapping functions even though they are associated with different classes of snRNP. These phenotypic relationships, along with the association of SL26p with SL75p imply that, like the SL1 RNA/Sm/SL75p/SL21p complex, the Sm Y/Sm/SL75p/SL26p complex is associated with trans-splicing. We hypothesize that the Sm Y snRNP is somehow associated with SL2-specific trans-splicing. This idea is supported by the fact that the sequences of SL2 RNA and Sm Y allow base pairing of the two snRNPs through their second stem/loops. We are currently testing for this base pairing interaction using psoralen/UV crosslinking.

Macmorris M et al. (2007) RNA "A novel family of C. elegans snRNPs contains proteins associated with trans-splicing."

Kumar M, MacMorris M, Lasda E, Kraemer B, Blumenthal T, Larsen A

[RNA, 2007]

In many Caenorhabditis elegans pre-mRNAs, the RNA sequence between the 5'' cap and the first 3'' splice site is replaced by trans-splicing a short spliced leader (SL) from the Sm snRNP, SL1. C. elegans also utilizes a similar Sm snRNP, SL2, to trans-splice at sites between genes in polycistronic pre-mRNAs from operons. How do SL1 and SL2 snRNPs function in different contexts? Here we show that the SL1 snRNP contains a complex of SL75p and SL21p, which are homologs of novel proteins previously reported in the Ascaris SL snRNP. Interestingly, we show that the SL2 snRNP does not contain these proteins. However, SL75p and SL26p, a paralog of SL21p, are components of another Sm snRNP that contains a novel snRNA species, Sm Y. Knockdown of SL75p is lethal. However, knockdown of either SL21p or SL26p alone leads to cold-sensitive sterility, whereas knockdown of both SL21p and SL26p is lethal. This suggests that these two proteins have overlapping functions even though they are associated with different classes of snRNP. These phenotypic relationships, along with the association of SL26p with SL75p, imply that, like the SL1 RNA/Sm/SL75p/SL21p complex, the Sm Y/Sm/SL75p/SL26p complex is associated with trans-splicing.

Scott A Barbee et al. (2001) International C. elegans Meeting "The splicesomal Sm proteins play a role in P granule localization during early embryogenesis."

Scott A Barbee, Thomas C Evans, Alex L Lublin

[International C. elegans Meeting, 2001]

In early C. elegans embryos, development is initiated by asymmetric cell division, which leads to the precise localization cell fate regulators to specific cells. One feature of early asymmetry is the localization of cytoplasmic RNP particles, the P granules, to the germ cell precursors at each of several polarized cell divisions. The composition and function of P-granules is not well understood. Further, the mechanisms that control the localization of P-granules and other factors in the embryo are poorly understood. We used RNA interference (RNAi) to screen a cDNA library for new genes involved in early polarity. Surprisingly, one of the genes identified is the ortholog of human SmE. SmE is one of several Sm proteins that form a multisubunit complex required for snRNP assembly, nuclear import, and mRNA splicing. RNAi of Sm subunits in C. elegans caused mislocalization of P granules to somatic sisters of germ cells after the 4-8 cell stages in the early embryo. In addition, Sm RNAi disrupted the subcellular distribution of PGL-1 (a P-granule component) in both mature germ cells and in germ cell precursors after the 8-cell stage. P-granules in wild type germ cells are primarily attached to the nucleus, but in Sm (RNAi) germ cells and embryos, the nuclear attachment of many P-granules is lost. At lower penetrance, GLP-1 protein was inappropriately expressed in posterior cells following Sm RNAi. By contrast, RNAi of the core splicing factors U1 70K and U2AF65, or of RNA polymerase II, had no effect on P granule segregation, subcellular distribution, or GLP-1 asymmetry, although all caused severe embryonic defects. These data suggest that the P-granule and GLP-1 asymmetry phenotypes from Sm RNAi are not likely to result from a general defect in splicing. Therefore, Sm proteins may have a role in P-granule localization that is independent of splicing. Interestingly, antibodies against the Sm complex stain P granules at all stages of development. Sm RNAi attenuates this staining. Therefore, Sm proteins may be P granule components that affect the localization of P granules by controlling their integrity or nuclear attachment in germ cells and their precursors. The Sm proteins are also found in the nucleus of most cells. However, nuclear localization of the Sm’s is dynamically regulated during oogenesis and germ cell precursor formation, suggesting that regulation of the Sm complex or snRNPs may be important for germ cell development.

Zhang W et al. (2016) Cell Mol Neurobiol "Shengmai Formula Ameliorates Pathological Characteristics in AD C.elegans."

Zhang Z, Zhu H, Fei D, Li H, Ren H, Wang D, Wang X, Zhang W, Zhi D

[Cell Mol Neurobiol, 2016]

Shengmai (SM) formula, a classical traditional Chinese medicine formula, is composed of Panax ginseng (Pg), Ophiopogon japonicus (Oj), and Schisandra Chinesis (Sc). SM has been clinically used to treat heart failure and ischemic heart disease. Although SM formula has been reported to be potential for fighting against Alzheimer's disease (AD) by previous works, there are many gaps in our knowledge on its usage in AD treatment on an organism level and will then need to be further clarified. In this study, transgenic Caenorhabditis elegans expressing human A1-42 are used to evaluate SM formula efficacy to treat AD phenotype and to investigate its underlying mechanism. The results showed that SM formula ameliorated AD pathological characteristics of paralysis behavior and chemotaxis defect in transgenic C.elegans. With SM treatment, the number of A deposits decreased, the levels of gene expressions of hsp16-2, hsp16-41, ace-1, ace-2, and TNFA1P1 homolog genes were down-regulated. Our results also showed that Oj exhibited more stronger effect on delaying paralysis in worms than Pg and Sc did, and synergistic action was observed between Pg and Oj, and Sc further enhanced the activity of Pg/Oj combination on delaying paralysis behavior. Further, SM with herbs of Pg, Oj, and Sc at a dose proportion of 9:9:6 exhibited superior therapeutic efficacy in comparison with herbs at other dose proportions. After SM formula extracted by ethanol, it delayed AD symptoms on a wider dose from 0.2 to 10.0mg/mL with no toxic effect. These results provided more evidence for SM formula being potential to be used to treat AD.

Garg D et al. (2014) Ageing Res Rev "miRNAs and aging: A genetic perspective."

Garg D, Cohen SM

[Ageing Res Rev, 2014]

A growing body of evidence shows that microRNA expression changes with age in animals ranging from nematode to human. Genetic studies of microRNA function in vivo provide the means to move beyond correlation and to explore cause-effect relationships. Genetic studies in C. elegans and Drosophila have identified cellular pathways involved in organismal aging. Here, we review the evidence that microRNAs act in vivo as regulators of aging pathways, with emphasis on Drosophila.

Chen EB et al. (1998) Trends Genet "Understanding cell migration guidance: lessons from sex myoblast migration in C. elegans."

Chen EB, Stern MJ

[Trends Genet, 1998]

Studies of sex myoblast (SM) migration in the nematode Caenorhabditis elegans have shown that multiple guidance mechanisms cooperate to ensure the accurate and reproducible targeting of the SMs. Many issues arise in the analysis of SM migration, including the action of multiple guidance mechanisms, redundant sources of guidance information, the multiple uses of molecular components, and whether factors affect cell fate determination events or the guidance mechanisms themselves. These issues are common to many cell migration events and make the analysis of SM migration instructive to our general understanding of how cell migrations are controlled.