Evidence for a novel left-right handedness choice mechanism in C. elegans. Export

@inproceedings{citeulike:3332957, abstract = { The arrangement of internal organs in most animals, including C. elegans, shows a distinct left-right (L-R) asymmetry. This L-R handedness generally becomes fixed during early embryonic development. In worms, skewing of the mitotic spindles in the dividing ABa and ABp cells following the 4-cell stage breaks the bilateral symmetry and establishes the overall L-R handedness of the animal. If the skewing of these spindles is reversed by physical manipulation or in a spn-1 mutant, healthy, mirror-symmetric worms with L-R reversed organs develop. We have obtained preliminary evidence for an additional L-R symmetry breaking mechanism that is independent of this early event. The adult male tail in C. elegans contains nine bilateral pairs of sensory rays that are required for successful mating behavior. Each ray is composed of two neurons and a structural cell. It was reported many years ago by John Sulston that the absence of rays is a common occurrence in wildtype males. We have confirmed these observations: 33\% of N2 males are missing one or two rays, particularly the posterior-most R8 or R9 rays. We found that the absence of these rays requires core components that activate programmed cell death. Mutations in ced-3 and ced-4 partially suppress this ray loss, whereas mutation of egl-1 completely eliminates the effect. These results imply that the absence of rays is the result of stochastic cell death in the ray lineages. This stochastic ray loss shows a handedness bias: rays on the right side are absent twice as frequently as those on left. To our surprise, this L-R bias in ray loss persisted in handedness-reversed worms from a spn-1 mutant. However, we found that heat-shock stress changed the handedness of ray loss, resulting in a reverse in the ratio of missing rays on left and right sides. Remarkably, mutations in ced-3 eliminated the asymmetric loss of only the left rays, whereas ced-4 mutations showed the opposite effect. Thus, there appears to be natural, CED-3-independent and CED-4-independent cell death occurring during male tail development on the left and right respectively. Our findings suggest that there may be a second L-R symmetry breaking system in C. elegans and that handedness cues influence distinct cell death pathways on opposite sides of the animal.}, author = {Choi, Shin S. and Bloss, Tim A. and Rothman, Joel H.}, citeulike-article-id = {3332957}, citeulike-linkout-0 = {http://www.wormbase.org/db/misc/paper?name=WBPaper00030192}, journal = {International Worm Meeting}, keywords = {c35d109, c48d12, c\_elegans, caenorhabditis\_elegans, ced-3, ced-4, celegans, egl-1, elegans, f23b129, gpa-16, meeting\_abstract, nematode, wormbase, y95b8a5}, posted-at = {2008-09-24 17:53:52}, priority = {3}, title = {Evidence for a novel left-right handedness choice mechanism in C. elegans.}, url = {http://www.wormbase.org/db/misc/paper?name=WBPaper00030192}, year = {2007} }

TY - CONF ID - citeulike:3332957 L3 - citeulike-article-id:3332957 N2 - The arrangement of internal organs in most animals, including C. elegans, shows a distinct left-right (L-R) asymmetry. This L-R handedness generally becomes fixed during early embryonic development. In worms, skewing of the mitotic spindles in the dividing ABa and ABp cells following the 4-cell stage breaks the bilateral symmetry and establishes the overall L-R handedness of the animal. If the skewing of these spindles is reversed by physical manipulation or in a spn-1 mutant, healthy, mirror-symmetric worms with L-R reversed organs develop. We have obtained preliminary evidence for an additional L-R symmetry breaking mechanism that is independent of this early event. The adult male tail in C. elegans contains nine bilateral pairs of sensory rays that are required for successful mating behavior. Each ray is composed of two neurons and a structural cell. It was reported many years ago by John Sulston that the absence of rays is a common occurrence in wildtype males. We have confirmed these observations: 33% of N2 males are missing one or two rays, particularly the posterior-most R8 or R9 rays. We found that the absence of these rays requires core components that activate programmed cell death. Mutations in ced-3 and ced-4 partially suppress this ray loss, whereas mutation of egl-1 completely eliminates the effect. These results imply that the absence of rays is the result of stochastic cell death in the ray lineages. This stochastic ray loss shows a handedness bias: rays on the right side are absent twice as frequently as those on left. To our surprise, this L-R bias in ray loss persisted in handedness-reversed worms from a spn-1 mutant. However, we found that heat-shock stress changed the handedness of ray loss, resulting in a reverse in the ratio of missing rays on left and right sides. Remarkably, mutations in ced-3 eliminated the asymmetric loss of only the left rays, whereas ced-4 mutations showed the opposite effect. Thus, there appears to be natural, CED-3-independent and CED-4-independent cell death occurring during male tail development on the left and right respectively. Our findings suggest that there may be a second L-R symmetry breaking system in C. elegans and that handedness cues influence distinct cell death pathways on opposite sides of the animal. JF - International Worm Meeting TI - Evidence for a novel left-right handedness choice mechanism in C. elegans. KW - c35d109 KW - c48d12 KW - c_elegans KW - caenorhabditis_elegans KW - ced-3 KW - ced-4 KW - celegans KW - egl-1 KW - elegans KW - f23b129 KW - gpa-16 KW - meeting_abstract KW - nematode KW - wormbase KW - y95b8a5 AU - Choi, Shin AU - Bloss, Tim AU - Rothman, Joel PY - 2007/// UR - http://www.wormbase.org/db/misc/paper?name=WBPaper00030192 ER -