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

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

[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.

Kim YI et al. (2004) J Mol Biol "Transcriptional regulation and life-span modulation of cytosolic aconitase and ferritin genes in C.elegans."

Kim YI, Cho JH, Yoo OJ, Ahnn J

[J Mol Biol, 2004]

Ferritin is the major iron storage protein regulating cytosolic concentration of iron by storing excess iron. Vertebrate ferritins are heteropolymeric proteins composed of heavy chain and light chain subunits. We have characterized two Caenorhabditis elegans genes (ftn-1 and ftn-2), which encode ferritin homologs showing high degree of similarity to mammalian ferritin heavy chains. Even though these two ferritins are more than 78% identical in amino acid sequence, our data show that expression patterns and responses to iron are quite different. Cytosolic aconitase (aco-1), iron regulatory protein, is known to regulate cellular iron concentration by modulating translation of the ferritin mRNA in addition to its enzymatic activity that converts citrate into iso-citrate. We have shown that the expression levels of aco-1 and ftn-1 genes are both regulated by iron treatment but in opposite ways. Interestingly, mutant animals lacking ACO-1 and FTN-1 show significantly reduced life-span upon iron stress, while N2 and ftn-2 animals show no difference. Our results suggest that ftn-1 and aco-1 are transcriptionally regulated by iron and are important for iron homeostasis affecting life-span upon iron stress conditions in C.elegans.

Min Sung Choi et al. (2007) International Worm Meeting "Genes that act in specification of the vulval secondary (2) fate."

Iva Greenwald, Min Sung Choi

[International Worm Meeting, 2007]

LIN-12/Notch signaling specifies Vulval Precursor Cells (VPCs) to adopt the 2 fate. Upon ligand binding, the intracellular domain of LIN-12 is released and translocates to the nucleus, where it forms a transcriptional activation complex with the sequence-specific DNA binding protein LAG-1. Direct target genes of LIN-12 in VPCs have been identified by searching for genes that contain LAG-1 binding sites in their 5 flanking regions, using various search criteria (1,2). We have used a computational approach to predict novel LIN-12 target genes, using specific criteria based on the nature and arrangement of LAG-1 binding sites in the promoter of the LIN-12 target gene mir-61 (2). We will present the results of transcriptional expression pattern screening of the set of genes obtained in our search. We will also present our work in progress on a set of genes that share the 5 flanking region and are expressed in presumptive 2 VPCs, the pattern expected of LIN-12 target genes. Analysis of mir-61 and its target, vav-1, suggested that they constitute a positive autoregulatory loop in which LIN-12 activation leads to expression of a negative regulator (mir-61) of a negative regulator (vav-1) of lin-12 activity (2). Thus, vav-1 is an indirect target of LIN-12 that influences the 2 fate. We will present our ongoing work on another microRNA gene that appears to be a direct target of LIN-12; the protein-encoding gene that is its likely target behaves genetically as a negative regulator of lin-12 activity, and hence these genes together also appear to function in a positive autoregulatory loop. We will also discuss the potential intersection of these two microRNA-mediated loops. (1) Yoo et al., Science 303:663-6(2004). (2) Yoo and Greenwald, Science 310:1330-3 (2005).

Sternberg PW (2004) Science "Developmental biology. A pattern of precision."

Sternberg PW

[Science, 2004]

The amazing precision with which different cell types find their correct locations in developing tissues has fascinated biologists for decades. Models of cell fate patterning during development emphasize the contrast between spatial gradients of developmental signals that act at long range and cell-to-cell signaling events that act locally. Development of the vulva in the nematode Caenorhabditis elegans provides an elegant model system for examining the patterning of cell fate in an animal. There is strong evidence that two different intercellular signals contribute to the relatively simple induction of cell fate among vulval precursor cells (VPCs): a long-range spatial gradient of epidermal growth factor (EGF) mediated by the EGF receptor (1, 2) and a cell-to-cell lateral signal mediated by the Notch-like receptor LIN-12 (35). It is well established that the combined action of the EGF receptor and LIN-12 receptor signaling pathways generate the pattern of VPCs in the developing vulva (6); however, the molecular details of this cooperative effect have remained elusive. On page 663 of this issue, Yoo et al. (7) provide the missing molecular connection. They report that VPCs activated by a low level of EGF are blocked from adopting a particular cell fate by a LIN-12 lateral signal from a neighboring cell.

Kershner, Aaron M. et al. (2011) International Worm Meeting "Two likely GLP-1/Notch targets are essential for germline stem sell maintenance in both larvae and adults."

Shin, Heaji J., Kimble, Judith, Kershner, Aaron M.

[International Worm Meeting, 2011]

C. elegans germline stem cells (GSCs) are maintained by GLP-1/Notch signaling and two redundant PUF family mRNA binding proteins, FBF-1 and FBF-2 (collectively, FBF). Notch signaling is essential for GSC maintenance in both larvae and adults, while FBF is essential only in late L4s and adults. The fbf-2 gene is the only Notch target gene known to date with a key role in GSC maintenance (1). Therefore, we sought additional Notch targets crucial for germline self-renewal. Two genes, lst-1 and T27F6.4, were identified as likely FBF targets (2) and also putative Notch targets (3). To ask whether lst-1 and T27F6.4 control GSC maintenance, we analyzed an lst-1 deletion mutant and T27F6.4 (RNAi) animals (progeny of L4s fed T27F6.4 RNAi bacteria). No effect was seen when either gene was removed singly, but depletion of the two together had a phenotype indistinguishable from that of a null glp-1 mutant: germ cell number was reduced from ~2000 to 8-10 total in L3 stage and these few germ cells differentiated as sperm. We conclude that lst-1 and T27F6.4 are redundant in their control of larval GSC proliferation and therefore dub T27F6.4 sygl-1, for synthetic germline proliferation defective. A different RNAi regimen, which depleted lst-1 and sygl-1 specifically in adults, revealed that these two regulators also control adult germline self-renewal. We suggest that the lst-1 and sygl-1 genes are pivotal for GSC maintenance throughout postembryonic germline development. References: (1) Lamont and Kimble (2004) Dev Cell 7(5):697-707; (2) Kershner and Kimble (2010) PNAS 107(8):3936-41; (3) Yoo and Greenwald (2004) Science 303(5658):637-8.

Escobar Restrepo, Juan et al. (2015) International Worm Meeting "Lipid asymmetry and signaling regulation during vulva development."

Hajnal, Alex, Haag, Andrea, Escobar Restrepo, Juan

[International Worm Meeting, 2015]

C. elegans let-23 is the homologue of the EGFR family of receptor tyrosine kinases and is required for the formation of the hermaphrodite vulva. LET-23 in the Vulva Precursor Cell (VPC) P6.p interacts with LIN-3 and activates the LET-60/MPK-1 pathway to acquire a 1deg cell fate. This triggers lateral LIN-12 NOTCH signaling in the adjacent P5.p and P7.p VPCs which acquire a 2deg cell fate (Sternberg et.al, Shaye et.al and Yoo et. al). In addition, several components of the LET-60/MPK-1 pathway are down-regulated in 2deg fated cells, for example let-23 (Berset. et al). We performed an in vivo RNAi screen for defects in receptor localization and/or expression using a functional LET-23::GFP reporter (Haag et.al). RNAi against tat-5 caused increased expression of LET-23::GFP in the daughters of P5.p and P7.p as compared to empty vector RNAi. A mutant of tat-5 displays a Protruding vulva phenotype and in combination with a mutant of the close homologue tat-6, shows a low penetrant Adjacent Primary Fate (APF) phenotype. The APF phenotype is enhanced when combined with a let-60(gf) mutation and is accompanied by an increase in the number of induced cells. Thus tat-5/tat-6 may act as negative regulators of the LET-60/MPK-1 pathway. tat-5 encodes a P4-type ATPase that functions as a flippase to inhibit phosphatidylethanolamine (PE) exposure on the outer plasma membrane. This activity is required to regulate the release extracellular vesicles (ECVs) in the worm (Wehman et.al) and vesicular protein trafficking in lower eukaryotes (Reviewed in Paulusma C. et. al). Here we discuss possible roles of lipid asymmetry in the acquisition of cell fates during vulval development.

Ji Li et al. (2007) International Worm Meeting "A systematic analysis of the roles of heterochronic genes in VPC fate specification."

Iva Greenwald, Ji Li

[International Worm Meeting, 2007]

We plan a systematic investigation of the roles of heterochronic genes in vulval precursor cell (VPC) competence and fate patterning. We have a particular interest in a potential role of heterochronic genes in LIN-12-mediated lateral signaling, which promotes the 2o fate, because vulval bursting, a phenotype associated with many heterochronic mutants, may be a symptom of an underlying problem in lateral signaling (cf. Grishok et al., 2001; Yoo and Greenwald, 2005). Furthermore, elegant work by Ambros (1999) showed that LIN-12-mediated specification of the 2o fate appears to be "gated" by the cell cycle, which in turn is controlled by heterochronic gene activity (Euling and Ambros, 1996). As a first step, we are examining vulval cell fates in heterochronic mutants using 1o and 2o fate markers. In addition, we will use a tissue-specific rescue or depletion approach to determine the cellular focus of heterochronic genes for vulval phenotypes to gain insight into whether these genes function in the signaling or receiving end of events involved in VPC competence and patterning. Finally, we will look at the potential cell-cycle gating of LIN-12 target gene expression. Genes expressed specifically in P5.p and P7.p may promote the 2o fate, whether they are direct targets of LIN-12 or not. The let-7 family member mir-48, a heterochronic gene (Abbott et al., 2005; Li et al., 2005), has been reported to display a 2o cell specific expression pattern (Esquela-Kerscher et al., 2005). We are investigating the role of mir-48 in 2o fate specification. Preliminary results suggest that ectopic expression of mir-48 in the presumptive 1o VPC causes the expression of a 2o cell fate marker, and also causes a timing defect consistent with a heterochronic phenotype (Li et al., 2005). Our progress in these areas will be presented.