Vancoppenolle B et al. (1996) European Worm Meeting "Comparison of the early embryonic cell lineage of Caenorhabdi- tis elegans and Pellioditis marina, two rhabditid nematodes."

Vancoppenolle B, Coomans AV, Schnabel R, Borgonie G

[European Worm Meeting, 1996]

The early embryonic cell lineage of Pellioditis marina, a marine rhabditid with relatively short developing time was traced using a 4D-microscope. Although the general pattern of cell divisions is congruent with the lineage described for Caenorhabditis elegans by Sulston and coworkers, striking differences can be observed concerning migrations, timing of divisions and cell deaths. The AB, MS and C lineage of P. marina differ from those of C. elegans both in the occurence of additional cell deaths as wel as in the abscence of certain cell deaths. Additionaly, Caap does not divide in accordance with the characteristic period of the rest of the C lineage. In contrast with C. elegans, the E founder cell in P. marina undergoes a migration before gastrulation and devides into Ea and Ep only after E has entered the interior of the embryo. D and P4 divide in a similar way as in C. elegans.

Vancoppenolle B et al. (1997) International C. elegans Meeting "COMPARISON OF THE EMBRYONIC CELL LINEAGE OF CAENORHABDITIS ELEGANS AND PELLIODITIS MARINA"

Borgonie G, Vancoppenolle B, Schnabel R, Coomans AV

[International C. elegans Meeting, 1997]

The early embryonic cell lineage of Pellioditis marina, a marine rhabditid with relatively short developing time (9hrs at 25!C) was traced using a 4D-microscope. Although the general pattern of cell division is congruent with the lineage described for Caenorhabditis elegans by Sulston and Co-workers, striking differences can be observed concerning migrations, timing of divisions and cell deaths. The AB, MS and C lineage of Pellioditis marina differ from those of Caenorhabditis elegans both in the occurence of additional cell deaths as well as in the abscence of certain cell deaths. Additionaly, Caap does not divide in accordance with the characteristic period for the rest of the C-lineage. In contrast with Caenorhabditis elegans, the E founder cell in Pellioditis marina undergoes a migration before gastrulation and divides into Ea and Ep only after E has entered the interior of the embryo. D and P4 divide in a similar way as in Caenorhabditis elegans.

W Houthoofd et al. (2002) European Worm Meeting "Embryonic development of the free-living, marine nematode Pellioditis marina"

G Borgonie, A Coomans, B Vancoppenolle, K Jacobsen, W Houthoofd

[European Worm Meeting, 2002]

Until now only the embryonic cell lineage of the model organism Caenorhabditis elegans has been described (Sulston et al., 1983). The embryonic cell lineage of the free-living nematode Pellioditis marina has been traced from zygote up until the initiation of muscle contraction by means of 4D-microscopy, marking the second detailed description of the embryonic development of a nematode. P. marina is a close relative of C. elegans, but has adapted to a marine, brackish environment. The overall lineage resembles strongly on that of C. elegans, with a few small differences. The developmental tempo of the early embryogenesis (until division of E cell) is more then two times slower than C. elegans. But the primordial germline cell P4 is already present at the 15-cell stage (in C. elegans at the 24-cell stage). At the stage of muscle contraction (when most cells are established), P. marina has as many cells as C. elegans (571 cells) but less cell deaths (67 and 106 respectively). Tissue conservation varies from highly conserved to highly variable. The intestine, the primordial gonad and the body muscles are highly conserved in the two species, while the pharynx, the epidermis and the nervous system have a more variable configuration. The systematic position of Pellioditis remains unsolved, whether Caenorhabditis or Rhabditis is the closest relative. The early embryogenesis and the developmental timing are comparable with that of other Rhabditis species, while the overall cell lineage is almost identical with that of C. elegans. The latter is a strong argument to place P. marina close to C. elegans in the classification. In more primitive nematodes (like Halicephalobus sp.), sublineages form identical cells, which migrate to their exact location. C. elegans has adjusted these lineages to avoid these migrations (Borgonie et al., 2000). This could explain the chaotic' fate topology in the C. elegans cell lineage. P. marina falls in between: it has already adjusted the Caa-lineage to form two nerve cells, but still has migrations that are avoided in C. elegans.

Erin Newman-Smith et al. (2001) International C. elegans Meeting "END-2, an apparent nuclear hormone receptor, relocalizes from the cytoplasm to the plasma membrane in response to environmental conditions"

Erin Newman-Smith, Marina Len, Gina Broitman-Maduro, Joel Rothman

[International C. elegans Meeting, 2001]

end-2 encodes a putative nuclear hormone receptor (NHR) that, based on gene reporter studies, is expressed in the endoderm throughout the life of the worm. NHR family members are transcriptional regulators that are activated when bound to their small lipophilic ligands such as steroids. While some NHRs are localized to the nucleus, others are cytoplasmic in the absence of ligand and translocate to the nucleus upon ligand binding. Once in the nucleus, they bind target sequences and regulate gene expression. We have found that while END-2 is present in the nucleus during early development, unexpectedly, it appears to localize to the plasma membrane under certain conditions later in development. END-2 antibody reveals nuclear expression of the protein in posterior cells of early embryos (pre-bean stage), consistent with RNA in situ analysis. However, by the bean stage, END-2 antigen relocalizes to the plasma membranes of developing gut cells. This membrane association continues through to hatching . Our preliminary biochemical results further indicate that END-2 partially associates with the membrane fraction obtained from both early and late embryos based on western blot analysis of embryonic extracts. We are biochemically investigating how END-2 associates with this membrane fraction. We found that in larvae, END-2 antigen is either primarily cytoplasmic (and nuclear-excluded) or is localized to the membrane, depending on the preparation examined. The variable localization of END-2 to the cytoplasm or membrane in larvae is attributable to variations in environmental conditions. When worms are grown in uncrowded conditions, END-2 is present throughout the cytoplasm of gut cells. However, when they are cultured at high density, the protein appears to partition to the membrane. The effect of crowding on END-2 localization may be a response to dauer pheromone, a hypothesis that we are currently testing. This intriguing localization pattern of END-2 is atypical for NHRs and suggests a possible novel mode of action. One postulate is that membrane-associated END-2 transduces a signal from the membrane. Such a possibility is consistent with the evidence that a number of steroids can transduce a signal that is independent of transcription, and in some cases the ligands can act without entering the cell. Alternatively, the non-membrane localized form of END-2 may function like a typical NHR and localization to the membrane may be a mechanism for sequestering END-2, rendering it inactive. We are performing genetic and biochemical studies to investigate these alternatives.

Erin Newman-Smith et al. (2002) West Coast Worm Meeting "DPR-1, a membrane-associated nuclear hormone receptor, prevents dauer recovery"

Erin Newman-Smith, Joel H Rothman, Marina Len, Gina Broitman-Maduro

[West Coast Worm Meeting, 2002]

DPR-1 (dauer pheromone responsive-1, previously END-2) is expressed throughout the life of the worm in the endoderm lineage. DPR-1 is a nuclear hormone receptor (NHR) and as such is expected to reside primarily in the cytoplasm or nucleus. While at different stages in the development of the worm DPR-1 is detected in the cytoplasm or nucleus, it moves to the membrane in response to crowded growth conditions. This membrane localization is extremely unusual for an NHR. The redistribution of DPR-1 to the membrane is detected both by immunocytochemistry and in western blots of worm extracts. We found that dauer pheromone also causes DPR-1 to become membrane-localized. The membrane targeting of DPR-1 may be a direct response to dauer pheromone, as the change in localization can occur very early in larval development, at the beginning of the L1 stage. Dauer pheromone is a small lipophilic molecule with characteristics of a bile acid, suggesting that it might act through an NHR. We are currently investigating whether DPR-1 might be such a dauer pheromone receptor.

Sudhaus W (1974) Zool. Jb. Syst. Bd. "Zur Systematik, Verbreitung, Okologie und Biologie neuer und wenig bekannter Rhabditiden (Nematoda) 2. Teil."

Sudhaus W

[Zool. Jb. Syst. Bd., 1974]

Five new species of the genus Rhabditis are described (Rh. riemanni n. sp., Rh. remanei n. sp., Rh. reciproca n. sp., Rh. blumi n. sp., and Rh. valida n. sp.) belonging to five subgenera (Crustorhabditis, Caenorhabditis, Rhabditis, Cephaloboides, and Pellioditis). The descriptions of four additional species are revised (Rh. ocypodis Chitwood, Rh. scanica Allgen, Rh. plicata Volk, and Rh. bengalensis Timm). The new subgenus Crustorhabditis n. subgen. derives from the paraphyletic subgenus Mesorhabditis. The species of the former group show a transition from living in littoral seaweed deposits to an obligate association with amphibious crabs (Crustacea). Information about the distribution, ecology, biology and ethology of all these species is presented (with two distribution maps, one for Rh. marina for comparison). Supplementary notes are given from Protorhabditis oxyuroides Sudhaus and Rhabditis tripartita von Linstow.

Volker Braun et al. (2001) International C. elegans Meeting "Nematode embryonic cell lineages are computationally efficient"

Gaetan Borgonie, Kim Jacobsen, Armand Leroi, Hans-Peter Meinzer, Paul Agapow, Volker Braun, Wouter Houthoofd, Ricardo Azevedo, Markus Gumbel

[International C. elegans Meeting, 2001]

The fixed cell lineages of nematodes like Caenorhabditis elegans are thought to provide a particularly efficient way to build an organism. However, many aspects of the C.elegans embryonic lineage are not obviously efficient (e.g., the distribution of neurons). Here we test whether the embryonic lineages of three species of rhabditid nematodes, C. elegans, Pellioditis marina and Rhabditophanes sp., are computationally efficient in the way cell fates are specified. We define three measures of cell lineage computational efficiency: number of symmetry breaking events, number of determination events and number of sublineages. First, we find that the actual cell lineages of all species specify most cellular phenotypes, such as cell morphology, function, and position in the hatchling, significantly more efficiently than would be expected if these phenotypes were randomly distributed in the same lineage, regardless of the efficiency measure used. Second, we show that the topologies of the actual lineages, themselves, significantly improve the efficiency of cell fate specification compared to cell lineages with random topologies. Third, we find that the cell lineages of the three species, show comparable levels of computational efficiency, despite considerable differences in topology and cell fates assignments. Our results suggest that the embryonic lineages of rhabditid nematodes evolve to place the right cell in the right place in a computationally efficient way.

Houthoofd W et al. (2008) Int J Dev Biol "The embryonic cell lineage of the nematode Rhabditophanes sp."

Houthoofd W, Jacobsen K, Willems M, Coomans A, Borgonie G

[Int J Dev Biol, 2008]

One of the unique features of the model organism Caenorhabditis elegans is its invariant development, where a stereotyped cell lineage generates a fixed number of cells with a fixed cell type. It remains unclear how embryonic development evolved within the nematodes to give rise to the complex, invariant cell lineage of C. elegans. Therefore, we determined the embryonic cell lineage of the nematode, Rhabditophanes sp. (family Alloionematidae) and made detailed cell-by-cell comparison with the known cell lineages of C. elegans, Pellioditis marina and Halicephalobus gingivalis. This gave us a unique data set of four embryonic cell lineages, which allowed a detailed comparison between these cell lineages at the level of each individual cell. This lineage comparison revealed a similar complex polyclonal fate distribution in all four nematode species (85% of the cells have the same fate). It is striking that there is a conservation of a C. elegans like polyclonal cell lineage with strong left-right asymmetry. We propose that an early symmetry-breaking event in nematodes of clade IV-V is a major developmental constraint which shapes their asymmetric cell lineage.

Ricardo B R Azevedo et al. (2002) East Coast Worm Meeting "Nematode embryonic cell lineages are computationally efficient"

Markus Gumbel, Ricardo B R Azevedo, Ute Platzer, Hans-Peter Meinzer, Kim Jacobsen, Armand M Leroi, Volker Braun, Gaetan Borgonie, Paul-Michael Agapow, Wouter Houthoofd

[East Coast Worm Meeting, 2002]

What is the minimal amount of information required to specify the cells of a metazoan? Based on ideas from algorithmic information theory and phylogenetics, we develop an algorithm for predicting the distribution of determination events in complete cell lineages. We assume that all such events are either cell autonomous or the outcome of permissive cell-cell interactions, and that the lineage is parsimoniously specified. Applying our algorithm to the complete embryonic lineage of Caenorhabditis elegans, we show that it predicts many known molecular events required to specify cell fates. We then show that less information is required to specify the actual C. elegans lineage than lineages simulated under null models. This is also true for two other species of rhabditid nematode, Pellioditis marina and Rhabditophanes sp., despite many interspecific differences in lineage topology and cell fate assignments. Only one cell fate was found to be inneficiently specified in all species: programmed cell death. Unlike normal cells, most apoptotic cells appear to have no particular function during development. However, we show that the computational efficiency of embryonic development would be increased if cell deaths did not occur all. Thus, selection for increased computational efficiency should lead to a reduction in the number of programmed cell deaths in embryonic cell lineages. Although many programmed cell deaths occur in the C. elegans embryonic lineage (17% of all cells), all of them occur in single-cell monoclones. This is a significantly higher proportion than that expected from permuted lineages and suggests that cell deaths have not accumulated neutrally in the cell lineages of the ancestors of C. elegans. That the absence of cell death monoclones containing two or more cells is due to selection and not due to an intrinsic constraint is demonstrated by the observation that they have been found in other species. Such cases, we suggest, arise frequently, but are then eliminated by reprogramming. Indeed, the main function of somatic cell death in these nematodes might be to eliminate redundant cells over the course of evolution. Our results strongly suggest that selection for computational efficiency moulds the evolution of nematode embryonic cell lineages. But even though nematode lineages are more efficient than random lineages, they are clearly not as efficient as they might be. Why not? The polyclonal origin of some cell fates might be due to the need to generate cells of the same type, such as neurons, in various parts of the embryo. This is supported by the observation that in all species studied here, the majority of cells are born close to their final position in the embryo. We speculate that, in C. elegans, P. marina and Rhabditophanes sp., the fitness cost of repeatedly specifying the same cell type may be less than the cost of additional cell migrations.

Ayuso, Cristina et al. (2019) MicroPubl Biol

Ayuso, Cristina, Askjaer, Peter

[MicroPubl Biol, 2019]

Several techniques are available for spatiotemporal control of genome recombination and gene expression in the nematode Caenorhabditis elegans. Here we report a novel tool to combine the powerful FLP-Frt and GAL4-UAS systems to increase their versality and to offer additional levels of control.FLP is an enzyme that catalyzes recombination between two short Frt DNA sequences and is frequently used to excise genomic fragments flanked by Frt sites, thereby either activating or knocking out gene expression, depending on the experimental design (Hubbard, 2014). Recently, we generated multiple strains that stably express FLP in different somatic tissues from single-copy transgenes and demonstrated that they in most cases induce recombination in ~100% of the cells of the expected tissue (Munoz-Jimenez et al., 2017). We subsequently constructed a strain for germline recombination to permanently knock out Frt-flanked genes or exons (Macas-Len and Askjaer, 2018).The GAL4-UAS system is based on the Saccharomyces cerevisiae Gal4p transcription factor and its cognate DNA target called upstream activating sequence (UAS). Typically, this bipartite system includes a series of driver strains expressing GAL4 in specific tissues and one or several strains with an effector gene downstream of UAS repeats. Wang and colleagues from the Sternberg laboratory recently optimized the GAL4-UAS system for C. elegans (cGAL) and reported several tissue-specific cGAL drivers (Wang et al., 2017). Moreover, they have developed a split cGAL toolkit where the DNA binding and activation domains are expressed as individual polypeptides, thereby enabling further fine-tuning of spatiotemporal control: only when and where the two components are co-expressed they will activate the UAS::effector transgene (Wang et al., 2018).