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for term "sites"
- Cell Biology of the Caenorhabditis elegans Nucleus...) or a single X chromosome (in males). The functional organization of a C. elegans chromosome is somewhat different from that of chromosomes in vertebrate cells. First, while in vertebrate cells chromosomes typically have a single centromere (the site of kinetochore assembly, through which chromosomes associate ~~~
- The Caenorhabditis elegans Excretory System: A Model for Tubulogenesis, Cell Fate Specification, and Plasticity...topologies and models for unicellular tube formation. (A and B) In multicellular tubes (A) and seamed unicellular tubes (B), adherens junctions (in black) separate and delineate the apical and basal domains. (C and D) In seamless unicellular tubes, junctions appear only at the end(s) of the tube, at the site ~~~
Figure 1Tube topologies and models for unicellular tube formation. (A and B) In multicellular tubes (A) and seamed unicellular tubes (B), adherens junctions (in black) separate and delineate the apical and basal domains. (C and D) In seamless unicellular tubes, junctions appear only at the end(s) of the tube, at the site of connection to another cell. Some multicellular tubes form by a cord-hollowing mechanism (A) involving polarized vesicle trafficking toward the lumen (arrows) (Datta et al. 2011). The excretory pore cell (in blue) (B) forms a seamed tube by wrapping and forming an autocellular junction (AJ). The excretory duct cell (in yellow) (C) initially forms a seamed tube and then converts to a seamless tube via autofusion to remove the AJ (Stone et al. 2009). The canal cell (in red) (D) forms a seamless tube, likely through a cell-hollowing mechanism involving polarized vesicle trafficking toward the lumen. The origin of relevant vesicles is not known. The intercellular junction with the duct may provide a polarizing cue that directs vesicle targeting to this region. For all tubes, both basal and apical sides may secrete extracellular matrices. For all diagrams, lumen is shown in lighter color.
Figure 12Spatial organization of C. elegans chromosomes. Examples of X chromosome (top) and chromosome I (bottom) are shown. Chromosome conformation capture (Hi-C) analysis was carried out on chromosomes from C. elegans embryos. The data from Hi-C analyses are typically depicted on a matrix where all chromosomal loci (in this case binned in 50-kb resolution) are on both the x- and y-axes, and the frequency of interaction (as reflected by the number of reads that span two loci) is color coded, with darker colors indicating a higher incidence of interaction (or more reads). Interactions will obviously be the greatest between two adjacent loci on the same chromosome, generating a very dark diagonal. The panels shown in this figure focus on a few megabases to each side of this diagonal. Diamond-shaped structures, such as the ones seen along the diagonal for the X chromosome, reflect TADs and indicate that there is a higher level of interaction between distant sites within the coordinates of the TAD than outside the TAD. This analysis revealed that C. elegans chromosomes are organized in megabase-sized TADs separated by boundaries (green lines; darker green indicates stronger boundary). The organization in TADs is more pronounced for the X chromosome than for autosomes (chromosome I shown as example). Figure courtesy of Barbara Meyer; data from Crane et al. (2015).