Zhang, Bo et al. (2011) International Worm Meeting "Searching for Negative Regulators of Neurite Outgrowth in Caenorhabditis elegans."

Song, Song, Ding, Mei, Huang, Xun, Zhang, Bo

[International Worm Meeting, 2011]

How do individual nerve fibers find their way along specific paths in a complex environment such as the developing central nervous system? A principal mechanism in axon guidance is binding of a receptor protein on the axon surface to a guidance molecule. However, it remains a mystery exactly how a limited number of guidance molecules can pilot the growth of billions of neurons. In our previous work, we identified a conserved Wnt pathway composed of Wnt ligand CWN-2, Frizzled receptors CFZ-2 and MIG-1, co-receptor CAM-1/Ror and downstream component DSH-1, which is crucial for RME neurite anterior-posterior (A-P) outgrowth in C. elegans. To address how axon outgrowth is terminated and how the termination signal interacts with Wnt pathway, we further searched mutants with longer RME processes. From an unbiased screen, we recovered an xd49 mutant, which displays a longer RME process phenotype. Furthermore, we also identified two more genes that could negatively regulate RME neurite outgrowth. Currently, we are taking genetics and biochemistry approaches to address how Wnt pathway interacts with this newly identified axon termination signal and how Wnt activity could be attenuated on time to fine tune the proper length of the axon. Detailed analysis will be reported in this meeting.

Zhang, Bo et al. (2015) International Worm Meeting "Imaging the dynamic chromatin status at specific loci in C. elegans."

Huang, Bo, L'Etoile, Noelle, Ward, Jordan, Zhang, Bo, Chen, Baohui

[International Worm Meeting, 2015]

Gene expression is regulated dynamically during development. The conformation of chromatin as well as its modifications regulate the transcriptional activity of genes. Studies have shown that some sites of euchromatin (which is usually transcriptionally active) can switch to the typically inactive heterochromatic state under specific developmental signaling cues, and vice versa (Oberdoerffer & Sinclair, 2007; Trojer & Reinberg, 2007). Though such chromatin dynamics contribute to developmental processes, whether they underlie behavioral plasticity is unknown. Previous studies in our lab have demonstrated that in AWC olfactory sensory neurons of C. elegans, odr-1, which encodes a guanylyl cyclase, is repressed in odor-adapted animals (Juang et al., 2013). In addition, we also observed increased binding of the heterochromatin associated factor HPL-2 at the odr-1 locus in AWC as a result of odor adaptation. This suggests that the repression of odr-1 expression might be due to changes in chromatin conformation. We plan to develop a CRISPR/Cas9 or TALE-based fluorescence imaging technique to facilitate monitoring of the dynamic changes in chromatin structure at specific loci, such as odr-1. By targeting endonuclease-deficient Cas9 or TALE tagged with fluorescent proteins to specific sites around a DNA locus, chromatin conformation changes may alter the distance and interaction between these reporters yielding a visible change under the microscope. We hope that this tool will enhance our ability to study dynamics of specific loci on chromosomes in live animals in the future. This will allow us to test our hypothesis that odor signaling dynamically alters the chromatin state at specific loci and that these changes promote behavioral plasticity.

Hoskins R (1987) Worm Breeder's Gazette "unc-30 on the map."

Hoskins R

[Worm Breeder's Gazette, 1987]

The unc-30 gene has been found to lie on the physical map, in a contig previously shown by J. Yuan to span the ced-3 locus(CSH 1987). unc-30 recombinants were picked from the progeny of unc-31(e928)unc- 30(e191)/BO parents and used to map BO/N2 DNA polymorphisms found in the ced-3 contig. The data indicate that unc-30 is surprisingly close to ced-3.Two polymorphisms have been mapped. They have been designated eP56 and eP57, and are recognized by hybridization with the cosmids ZK987 and C43A2, respectively. They map as follows: unc- 31[8]eP56[4]ePS[1]unc-30. A right-hand limit on the position of unc- 30 has been established by Yuan. She has mapped a BO-specific Tc1 to the right of ced-3 in the cosmid MMMC1. The physical distance between unc-30 and ced-3 must therefore be less than 120kb of DNA; the genetic distance between them is 0.3-0.5%. It should now be possible to clone the unc-30 gene. Attempts toward this end have been hampered by the potpourri of repeat sequences in cosmids to the right of eP57. Several DNA polymorphisms have been found in EMS, [32P], and spontaneous BO unc-30 alleles.

Ayyadevara S et al. (1995) International C. elegans Meeting "MAPPING OF LONGEVITY DETERMINING GENES IN C. ELEGANS"

Thaden JJ, Ayyadevara S, Ebert RHA, Shmookler Reis RJ

[International C. elegans Meeting, 1995]

Absence of inbreeding depression, short mean life span and reduced generation time make C. elegans an excellent model system for studying genes that determine longevity. Recombinant inbred strains have been used in a number of organisms to map genes of aging. Recombinant inbred (RI) lines were generated from a cross between a low-Tc1-copy strain (Cl2a) and a high-copy strain (Bergerac-BO). A similar cross (Ebert et al; Genetics 1993) was made between Bristol N2 and Bergerac-BO for the same purpose, and the genotypes were analysed by using sequence-tagged strain specific markers. As aging is polygenic and any two strains will be polymorphic at only some of the relevent loci the present cross is aimed at mapping additional genes that determine longevity. Bergerac-BO and Cl2a worms were crossed for seven generations to accumulate recombinations, followed by five generations of selffertilizations to achieve homozygsoity. Analysed genotypes of young and old worms from a synchronously aging population, will be presented.

Beckenbach KA et al. (1988) Worm Breeder's Gazette "strain identification using mitochrondria RFLD's."

Rose AM, Beckenbach KA, Baillie DL

[Worm Breeder's Gazette, 1988]

We have investigated the possibility of using RFLD's (Restriction Fragment Length Differences) of a mtDNA fragment to distinguish the various C. elegans strains. Ann Rose's lab cloned the 5kb EcoRI restriction fragment (pCeh109) of the mitochondria DNA. Total DNA from N2, BO, PA-2, GA-1, and N2(DR) was isolated, restricted, fractionated on an agarose gel, and transferred to nitrocellulose. The filter was then probed using [32p] labelled pCeh109. The restriction enzymes we used were AccI, AluI, AvaII, DdeI, DraI, HaeIII, HincII, HinfII, and RsaI. Six of the nine enzymes used showed an RFLD that easily distinguished Pa2 from the others, and two showed a possible difference between N2 and BO. Since PA-2 shows an RLFD with so many of the restriction enzymes, it is possible that the mtDNA of this strain has some sort of rearrangement. The nature of these RLFD's and the ones between N2 and BO are currently being investigated.

Beckenbach KA et al. (1984) Worm Breeder's Gazette "the cloning of the region around unc-22."

Beckenbach KA, Rose AM, Baillie DL

[Worm Breeder's Gazette, 1984]

The region around unc-22, flanked by unc-43 on the left and unc-31 on the right, has been intensively studied in our laboratory over the last eight years using conventional genetic analysis. We have now embarked upon a molecular analysis of this same region. We have at present identified and recovered about 300 kb of DNA that lies within this two map unit interval. Tc1 induced restriction fragment length differences closely linked to unc-22 were identified in the N2 and BO strains. DNA was prepared from a strain constructed by serial backcrossing of N2/BO heterozygotes to N2 males (where the BO chromosome IV was marked with a EMS induced unc-22 allele). After each cross the unc-22 marked BO chromosome was recovered homozygous. This procedure was repeated six times. A lambda gt10 EcoRI library was constructed and subsequently screened for Tc1-containing sequences. These phage were isolated and their genomic fragments subcloned into pUC13 or pUC19 plasmid vectors. The flanking sequences were recovered by EcoRV digestion followed by blunt end ligation and recloning of the Tc1 deleted plasmid. These plasmids provided convenient probes for the mapping of the associated N2/BO RFLD. Three factor mapping was carried out using the marker pairs unc-43 unc-31 to map the plasmid-defined RFLD. The resulting newly-defined molecular sites are shown on the accompanying figure. The plasmids which defined each site were then used to isolate genomic clones from our lambda Charon 4 library (prepared by T. Snutch). About 25-30 kb of flanking sequence was recovered for each probe. These lambda phage were in turn checked for overlap with existing cosmids in John Sulston's genomic mapping collection. [See Figure 1]

Irazoqui JE (2015) Immunity "Why worms watch their hemidesmosomes and why you should, too."

Irazoqui JE

[Immunity, 2015]

Hemidesmosomes are cellular attachment structures of great importance to the epidermis. In this issue of Immunity, Zhang et al. (2015) have discovered that in addition to having structural functions, invertebrate and human hemidesmosomes are actively monitored by the cell as a novel mechanism for detecting pathogenic infection.

Kumsta C et al. (2019) J Cell Biol "Getting under the skin: Cuticle damage elicits systemic autophagy response in C. elegans."

Hansen M, Kumsta C

[J Cell Biol, 2019]

In this issue, Zhang et al. (2019. <i>J. Cell. Biol.</i> https://doi.org/10.1083/jcb.201907196) describe a molecular mechanism by which cuticular damage in the nematode <i>C. elegans</i> leads to systemic induction of autophagy by signals propagated from sensory neurons via the TGF- signaling pathway.

Harris LJ et al. (1986) Mol Cell Biol "Somatic excision of transposable element Tc1 from the Bristol genome of Caenorhabditis elegans."

Harris LJ, Rose AM

[Mol Cell Biol, 1986]

We investigated the ability of the transposable element Tc1 to excise from the genome of the nematode Caenorhabditis elegans var. Bristol N2. Our results show that in the standard lab strain (Bristol), Tc1 excision occurred at a high frequency, comparable to that seen in the closely related Bergerac strain BO. We examined excision in the following way. We used a unique sequence flanking probe (pCeh29) to investigate the excision of Tc1s situated in the same location in both strains. Evidence of high-frequency excision from the genomes of both strains was observed. The Tc1s used in the first approach, although present in the same location in both genomes, were not known to be identical. Thus, a second approach was taken, which involved the genetic manipulation of a BO variant, Tc1(Hin). The ability of this BO Tc1(Hin) to excise was retained after its introduction into the N2 genome. Thus, we conclude that excision of Tc1 from the Bristol genome occurs at a high frequency and is comparable to that of Tc1 excision from the Bergerac genome. We showed that many Tc1 elements in N2 were apparently functionally intact and were capable of somatic excision. Even so, N2 Tc1s were prevented from exhibiting the high level of heritable transposition displayed by BO elements. We suggest that Bristol Tc1 elements have the ability to transpose but that transposition is heavily repressed in the gonadal tissue.

Svendsen JM et al. (2018) Dev Cell "piRNA Rules of Engagement."

Svendsen JM, Montgomery TA

[Dev Cell, 2018]

piRNAs are known to silence transposable elements, but not all piRNAs match transposon sequences. Recent studies from Shen etal. (2018) and Zhang etal. (2018) identify rules for piRNA target recognition in Caenorhabditis elegans. Permissive pairing rules allow targeting of essentially all germline mRNAs, while protective mechanisms prevent silencing self-genes.