Lao, Victor et al. (2021) International Worm Meeting "Chromo domain proteins maintain germline immortality and restrict transgenerational RNAi inheritance"

Lao, Victor, Li, Chengyin, Aram, Reta, Lee, Tammy L., Saltzman, Arneet L.

[International Worm Meeting, 2021]

Mechanisms that preserve germ cell fate and genome stability safeguard the germ cell lineage over generations, thus ensuring germline 'immortality'. In C. elegans, germline immortality and transgenerational epigenetic inheritance (TEI) phenomena have shared genetic requirements. In particular, several genes with key roles in small RNA pathways and chromatin regulation are required for maintaining fertility and for RNA interference (RNAi) inheritance, an established model for TEI. However, the mechanisms that limit the duration of RNAi inheritance are less well understood. We previously reported a loss of germline immortality upon deletion of cec-3 and cec-6, two genes encoding chromo domain proteins that recognize heterochromatin-associated histone marks (H3K9 and H3K27 methylation). To understand how cec-3 and cec-6 contribute to germline immortality, we used several reporter and phenotypic assays for small RNA and chromatin regulation. Unexpectedly, we found that cec-3 and cec-6 together limit the transgenerational duration of RNAi inheritance. We also found that cec-3 and cec-6 differentially affect repetitive transgene regulation and RNAi sensitivity in the germline versus the soma. In cec-3;cec-6 mutant animals, we see an enhanced nuclear RNAi and a mildly reduced germline RNAi response. In addition, whereas a repetitive transgene was desilenced in the germline of cec-6 mutant animals, it was ectopically silenced in the soma in both cec-6 and cec-3 mutant animals. This transgene silencing was partially dependent on the H3K9me2 methyltransferase met-2. We further observed changes in the morphology of perinuclear germ granules, which are organizing centers of RNA regulation. Together, our data suggest that cec-3 and cec-6 modulate small RNA-directed chromatin regulation to limit TEI and preserve germline immortality.

Lee, Tammy et al. (2021) International Worm Meeting "Chromodomain proteins CEC-3 and CEC-6 promote germ granule integrity and genome stability"

Lee, Tammy, Lao, Victor, Aram, Reta, Saltzman, Arneet

[International Worm Meeting, 2021]

Cooperation between mechanisms that safeguard germline immortality is required for the continual inheritance of genetic information. In C. elegans, the interplay between small RNA and chromatin regulation pathways impacts fertility across generations, while disruption to the chromatin landscape can also lead to genome instability. The C. elegans chromodomain proteins, CEC-3 and CEC-6, recognize heterochromatin-associated histone H3K9 and H3K27 methylation in vitro and cec-3;cec-6 mutant animals show progressive sterility or a 'mortal germline' phenotype. To understand the mechanism underlying this fertility defect, we are investigating the roles of cec-3 and cec-6 in germ cell fate, small RNA pathways and heterochromatin regulation. Live imaging of GFP-tagged PGL-1 suggests disruption of perinuclear RNA germline granules (P-granules) in cec-3;cec-6 mutant adult germlines. A reporter assay also implicated cec-3 and cec-6 in protecting the genome against repeat instability. We are also examining the effects of cec-3 and cec-6 on the expression of repetitive elements, transposons and endogenous siRNA targets. Together, our results suggest a role for these heterochromatin reader proteins in the small RNA and chromatin silencing pathways that maintain germ cell fate and genome integrity.

Marx JL (1984) Science "New clues to developmental timing."

Marx JL

[Science, 1984]

Within the past few years researchers have finally begun to be able to peer inside a hitherto impenetrable black box, namely, the development of complex organisms. The genes that control the commitment of embryonic cells to specific fates are now being found and characterized. A case in point is reported in this issue of Science (p. 409). Victor Ambros of Harvard University and H. Robert Horvitz of Massachusetts Institute of Technology have identified genes that affect the timing of developmental events in the roundworm Caenorhabditis elegans.

Link CD (1988) Worm Breeder's Gazette "Call for C. elegans Cloned Genes"

Link CD

[Worm Breeder's Gazette, 1988]

A few years ago, when I was brewing up C. elegans and P. redivivus libraries, I also constructed a genomic lambda EMBL-4 library from a wild strain, WS9-6, that I had gotten from Victor Ambros. This male/female strain is morphologically similar to C. elegans, but is not cross-fertile with either C. elegans or C. remanei. This spring I am planning to fish some C. elegans genes out of this library as an exercise for a molecular genetics laboratory course. If anyone has a gene that they might like isolated from this library (for evolutionary comparisons, etc.) please let me know.

(2019) Development "The people behind the papers - Sungwook Choi."

[Development, 2019]

The control of timing in development is crucial, both within and between tissues. Heterochrony involves shifts in the rate of development of some tissues relative to others, and although the first heterochronic genes were identified in <i>Caenorhabditis elegans</i> in the early 1980s, their role in inter-tissue developmental coordination is still not completely understood. A new paper in Development tackles this problem with an analysis of the role of <i>lin-28</i>, a key heterochronic gene, in worm fertility. We caught up with Sungwook Choi, first author and recently graduated PhD student in Victor Ambros' lab at the University of Massachusetts Medical School in Worcester, to find out more.

Maatouk D et al. (2006) ScientificWorldJournal "MicroRNAs in development."

Harfe B, Maatouk D

[ScientificWorldJournal, 2006]

Over 10 years ago, the lab of Victor Ambros cloned an unusual gene, lin-4, which encodes two small RNA transcripts[1]. In the past few years, hundreds more of these tiny transcripts, termed microRNAs (miRNAs), have been uncovered in over a dozen species. The functions of the first two miRNAs, lin-4 and let-7, were relatively easy to identify since they were found in forward genetic screens in Caenorhabditis elegans[1,2,3]. However, uncovering the functions of the growing list of miRNAs presents a challenge to developmental biologists. This review will describe our current understanding of how miRNAs regulate gene expression and will focus on the roles these noncoding RNAs play during the development of both invertebrate and vertebrate species.

Hodgkin JA (1988) Worm Breeder's Gazette "informational suppression by male-abnormal mutations: new names, new data."

Hodgkin JA

[Worm Breeder's Gazette, 1988]

As previously reported (WBG 10-1: 112, 10-2: 30, etc.) mutations at six different loci act as allele-specific suppressors of mutations in a variety of genes: tra-2, unc-54, etc. These mutations also have characteristic morphological effects on the anatomy of the adult male tail and, to a lesser extent, of the hermaphrodite vulva. For this reason they have hitherto been assigned to the mab (male abnormal) gene category: mab-1, ed) and mab-12 through mab-16 (unpublished). However, they exhibit such a distinctive set of common properties that it has been decided (with the agreement of Andy Papp, Victor Ambros, Rock Pulak and Phil Anderson, who have been responsible for isolating most of these suppressor mutations) to assign them to a new gene

Victor L. Jensen et al. (2006) European Worm Meeting "A Potential DAF-16 Target Involved in Longevity"

David L. Baillie, Victor L. Jensen, Donald L. Riddle

[European Worm Meeting, 2006]

Victor L. Jensen1, David L. Baillie2, and Donald L. Riddle3. Genes differing in steady-state RNA levels between N2 and daf-2 adults and N2 dauer larvae were identified using Serial Analysis of Gene Expression (SAGE) databases. One gene, a putative transcription factor, was isolated from a screen for genes involved in longevity. The outcrossed knockout allele was shown to have extended longevity, ~3% Him and ~2% Vab phenotypes. The 1 kb of genomic sequence 5? of the confirmed transcription start site contains several possible DAF-16 binding sites. By using a series of truncated promoter sequences to drive GFP expression, possible in vivo activity for these DAF-16 binding sites was observed. One consensus site DBE (DAF-16 Binding Element) may act to repress transcription. This is in agreement with the SAGE data which shows down regulation of this transcription factor in the daf-2 background. In daf-2 mutants DAF-16 is activated and is required for extended longevity. Transcriptional targets and the DNA binding motif for the transcription factor will be elucidated, and its role in longevity will be characterized.

Sudomo M et al. (2010) Adv Parasitol "Elimination of lymphatic filariasis in Southeast Asia."

Hernandez L, Wu WP, Duong S, Sudomo M, Bergquist R, Chayabejara S

[Adv Parasitol, 2010]

Approximately 15 million people with lymphatic filariasis (LF) live in Southeast Asia. Wuchereria bancrofti (transmitted by the Mansonia and Anopheles vectors), Brugia malayi and Brugia timori (both transmitted by Culex quinquefasciatus) are the filarial species in this region. The endemic countries are: Cambodia, Lao People's Democratic Republic, the Philippines, Indonesia, Thailand and Timor-Leste, which have all agreed to eliminate transmission of the disease by 2020. The public health interventions with respect to LF are based on the 1997 World Health Assembly resolution (WHA 50.29) which recommends elimination of the disease through mass drug administration (MDA) using diethylcarbamazine (DEC) and albendazole. The drugs are generally donated and as governments contribute 60-90% of the operational costs, MDA is deemed to be comparatively inexpensive for local administrations in relation to other public health programmes. So far, elimination has been accomplished only in the People's Republic of China (P.R. China) and this achievement is therefore described here in some detail. Resurgences have occurred but they have been successfully dealt with. Historically, the endemic areas in P.R. China covered 16,514 townships (or urban sub-districts), situated in 864 counties (or cities) in 14 provinces (or autonomous regions or municipalities). The total population at risk of infection in all endemic areas of P.R. China was originally 342 million.

Winkenbach LP et al. (2019) RNA Biol "Todos Santos small RNA symposium."

Claycomb JM, Doser R, Pasquinelli AE, Winkenbach LP, Reed KJ, Phillips CM

[RNA Biol, 2019]

Worm biologists from the United States, Canada, and the United Kingdom gathered at the Colorado State University Todos Santos Center in Baja California Sur, Mexico, April 3-5, 2019 for the Todos Santos Small RNA Symposium. Meeting participants, many of whom were still recovering from the bomb cyclone that struck a large swath of North America just days earlier, were greeted by the warmth and sunshine that is nearly ubiquitous in the sleepy seaside town of Todos Santos. With only 24 speakers, the meeting had the sort of laid-back vibe you might expect amongst the palm trees and ocean breeze of the Pacific coast of Mexico. The meeting started with tracing the laboratory lineages of participants. Not surprisingly, the most common parental lineages represented at the meeting were Dr. Craig Mello, Dr. Gary Ruvkun, and Dr. Victor Ambros, whom, together with Dr. Andy Fire and Dr. David Baulcombe, pioneered the small RNA field. In sad irony, on the closing day of the meeting, participants were met with the news of Dr. Sydney Brenner's passing. By establishing the worm, <i>Caenorhabditis elegans</i>, as a model system Dr. Brenner paved the way for much of the research discussed here.