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[
Worm Breeder's Gazette,
1994]
Mono- and Polycistronic pre-mRNA Splicing in a C. elegans embryo extract
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[
Curr Biol,
2006]
The transition from oocyte to embryo is among the most enthralling events in developmental biology. Recent studies of this transition in the nematode Caenorhabditis elegans have revealed how conserved kinases administer the destruction of key oocyte meiotic regulators to create an embryo.
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[
Dev Biol,
1986]
During development Caenorhabditis elegans changes from an embryo that is relatively spherical in shape to a long thin worm. This paper provides evidence that the elongation of the body is caused by the outermost layer of embryonic cells, the hypodermis, squeezing the embryo circumferentially. The hypodermal cells surround the embryo and are linked together by cellular junctions. Numerous circumferentially oriented bundles of microfilaments are present at the outer surfaces of the hypodermal cells as the embryo elongates. Elongation is associated with an apparent pressure on the internal cells of the embryo, and cytochalasin D reversibly inhibits both elongation and the increase in pressure. Circumferentially oriented microtubules also are associated with the outer membranes of the hypodermal cells during elongation. Experiments with the microtubule inhibitors colcemid, griseofulvin, and nocodazole suggest that the microtubules function to distribute across the membrane stresses resulting from microfilament contraction, such that the embryo decreases in circumference uniformly during elongation. While the cytoskeletal organization of the hypodermal cells appears to determine the shape of the embryo during elongation, an extracellular cuticle appears to maintain the body shape after elongation.
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[
Worm Breeder's Gazette,
1977]
A method for fixing and embedding C. elegans eggs will be introduced. It involves prolonged osmium or glutaraldehyde-osmium fixation at elevated temperatures. This procedure works on all stages of embryogenesis. 16 embryos in various stages ranging from an uncleaved zygote to a prehatching 'pretzel' have been serially sectioned. The analysis of a 5-hour embryo with 294 cells and of a 7-hour embryo with 540 cells will be presented. Data from the 5-hour embryo supplement the Nomarski results. Data from the 7-hour embryo will be compared with the anatomy of the young L1 worked out by Sulston and Horvitz.
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[
Curr Biol,
2011]
Embryonic morphogenesis requires the coordination of forces across multiple tissues and their associated extracellular matrices. A new study reports a mechanical feedback loop in the Caenorhabditis elegans embryo between muscle and epidermis that may provide a model for understanding how tissues coordinate morphogenetic events in the embryo.
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Wu, Y., Guo, M., Moyle, M., Ardiel, E., Shroff, H., Bokinsky, A., Santella, A., McCreedy, E., Colon-Ramos, D., Karaj, N., Duncan, L., Bao, Z., Levin, M., Mohler, W., Lauziere, A., Harvey, B., Christensen, R.P.
[
International Worm Meeting,
2019]
The Caenorhabditis elegans embryo represents an excellent model system in which to study tissue formation. However, the onset of twitching and elongation makes data analysis during the second half of embryogenesis difficult. Previously, we developed software to enable computational untwisting of the C. elegans embryo, removing the effects of embryo movement and placing embryo images in a common reference frame for analysis. We have now improved our software suite to incorporate more user-friendly positional tracking and better segmentation, reducing clipping of images around the edges of the embryo. We also apply deep learning to segment nuclei in a semi-automated fashion. We apply our software to generate a map showing the position of 158 nuclei in the post-twitching worm embryo, as a partial step in the generation of a complete embryonic nuclear atlas. Tracked nuclei include 16 neurons and 81 body wall muscles. Our improved tools, combined with pre-twitching work from our collaborators on the WormGUIDES project, allow us to pursue the goal of developing a complete nuclear and neurite outgrowth atlas for the nematode embryo from the two cell stage until hatching.
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[
Cold Spring Harb Protoc,
2010]
The Caenorhabditis elegans embryo is particularly amenable to microscopy and embryological studies because of its short developmental time, transparent shell, and nonpigmented cells. The agar mount described in this protocol is an easy way to prepare live C. elegans embryos for microscopic visualization. The mount slightly embeds the embryo in agar to hold it in place. The mount also slightly compresses the embryo to provide consistent orientation such that every embryo will be positioned with either its right side or its left side facing the objective. Other techniques can result in random orientations that complicate analysis and make identification of individual blastomeres more challenging.
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[
Nat Protoc,
2007]
Cell culture is an invaluable tool for investigation of basic biological processes. However, technical hurdles including low cell yield, poor cell differentiation and poor attachment to the growth substrate have limited the use of this tool for studies of the genetic model organism Caenorhabditis elegans. This protocol describes a method for the large-scale culture of C. elegans embryo cells. We also describe methods for in vitro RNA interference, fluorescence-activated cell sorting of embryo cells and imaging of cultured cells for patch-clamp electrophysiology studies. Developing embryos are isolated from gravid adult worms. After eggshell removal by enzymatic digestion, embryo cells are dissociated and plated onto glass substrates. Isolated cells terminally differentiate within 24 h. Analysis of gene expression patterns and cell-type frequency suggests that in vitro embryo cell cultures recapitulate the developmental characteristics of L1 larvae. Cultured embryo cells are well suited for physiological analysis as well as molecular and cell biological studies. The embryo cell isolation protocol can be completed in 5-6 h.
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[
Methods Mol Biol,
2006]
Because of technical hurdles, large-scale cell culture methods have not been widely exploited until recently for the study of Caenorhabditis elegans. Culturing differentiated cells from larvae and adult worms is probably not technically feasible because of difficulties in removing the animal''s cuticle and dissociating cells. In contrast, large numbers of developing embryo cells can be isolated relatively easily. When placed in culture, embryo cells undergo terminal differentiation within 24 h. Cultured embryo cells have been used recently to characterize ion channel function and regulation and to determine cell specific gene expression patterns. This chapter will provide a detailed description of the methods for isolating and culturing C. elegans embryo cells.
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[
EMBO J,
2014]
Development of the early embryo is thought to be mainly driven by maternal gene products and post-transcriptional gene regulation. Here, we used metabolic labeling to show that RNA can be transferred by sperm into the oocyte upon fertilization. To identify genes with paternal expression in the embryo, we performed crosses of males and females from divergent Caenorhabditis elegans strains. RNA sequencing of mRNAs and small RNAs in the 1-cell hybrid embryo revealed that about one hundred sixty paternal mRNAs are reproducibly expressed in the embryo and that about half of all assayed endogenous siRNAs and piRNAs are also of paternal origin. Together, our results suggest an unexplored paternal contribution to early development.