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[
Science,
1998]
About 800 biologists gathered at Stanford University from 20 to 25 June for the 57th annual meeting of the Society for Developmental Biology. Study organisms ranged from flies to mice to plants, but there was plenty of common ground, including a new pathway by which signaling molecules can shape the early embryo and a new gene that helps specify right from left.
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[
Nature,
1992]
Two types of developmental events can cause an embryonic cell to adopt a fate different from that of its neighbours: during a cell division particular contents may be segregated to only one daughter cell and cells may experience different external cues, commonly in the form of inductive cell interactions. Work on development in the nematode Caenorhabditis elegans suggests that most cell fates are specified without a need for cell interactions. In particular, the gut cell lineage of C. elegans has been used as a primary example of specification by differential segregation of determinants. Here I re-examine the role of induction in gut specification by isolating early blastomeres. In C. elegans, the gut derives from all the progeny of a single blastomere (E) of the eight-cell stage. When a gut precursor cell (EMS) is isolated during the first half of the four-cell stage, gut does not differentiate. Gut differentiation is rescued by recombining EMS with its posterior neighbour (P2), but not by recombining EMS with one or both of the other two cells of the four-cell stage. These results demonstrate that P2 induces EMS to form gut in C. elegans.
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Christensen RP, Guo M, McAuliffe M, Kumar A, Kovacevic I, Liu H, Shroff H, Santella A, Marquina-Solis J, Bao Z, Colon-Ramos DA, Wu Y, Tashakkori N, Winter PW, McCreedy E, Mohler W, Bokinsky A
[
Elife,
2015]
The nematode Caenorhabditis elegans possesses a simple embryonic nervous system comprising 222 neurons, a number small enough that the growth of each cell could be followed to provide a systems-level view of development. However, studies of single cell development have largely been conducted in fixed or pre-twitching live embryos, because of technical difficulties associated with embryo movement in late embryogenesis. We present open source untwisting and annotation software which allows the investigation of neurodevelopmental events in post-twitching embryos, and apply them to track the 3D positions of seam cells, neurons, and neurites in multiple elongating embryos. The detailed positional information we obtained enabled us to develop a composite model showing movement of these cells and neurites in an "average" worm embryo. The untwisting and cell tracking capability we demonstrate provides a foundation on which to catalog C. elegans neurodevelopment, allowing interrogation of developmental events in previously inaccessible periods of embryogenesis.
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[
1983]
More than 100 years ago, early European embryologists had posed the two central questions of animal development: First, how is the sameness of cells and organisms maintained during development and reproduction, and what factors transmit this hereditary information? Second, how do the cells of an embryo become different; what factors dictate that a particular cell at a particular time and position becomes committed to a particular developmental pathway? In the intervening century, we have largely answered the first question, acquiring extensive information about the genetic machinery and how it works. By contrast, we have gained little new understanding of the epigenetic process responsible for temporal and positional control of cell determination in embryos. How this process operates remains a central problem of contemporary
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[
Nematology,
2000]
To determine whether embryogenesis of Caenorhabditis elegans is typical for nematodes in general, we started to analyse in comparison several aspects of development in various nematode species. The differences we observed can be subdivided into two classes, those visible in the intact embryo and those requiring experimental interference. Particularly obvious differences of both types were revealed between C. elegans (Rhabditidae) and Acrobeloides nanus (Cephalobidae). Not only does the spatial and temporal pattern of early events differ but also that of intercellular communication and cell specification. Our data suggest that some developmental variations are characteristic for certain nematode groups and therefore may be useful as phylogenetic markers. In contrast, we detected little evidence so far for environmental influence on early developmental processes.