The Experts below are selected from a list of 1587 Experts worldwide ranked by ideXlab platform
Francisco Pelegri - One of the best experts on this subject based on the ideXlab platform.
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The Chromosomal Passenger Protein Birc5b Organizes Microfilaments and Germ Plasm in the Zebrafish Embryo
2016Co-Authors: Sreelaja Nair, Mary C Mullins, Florence Marlow, Elliott Abrams, Francisco PelegriAbstract:Microtubule-microfilament interactions are important for cytokinesis and subcellular localization of proteins and mRNAs. In the early zebrafish embryo, Astral Microtubule-microfilament interactions also facilitate a stereotypic segregation pattern of germ plasm ribonucleoparticles (GP RNPs), which is critical for their eventual selective inheritance by germ cells. The precise mechanisms and molecular mediators for both cytoskeletal interactions and GP RNPs segregation are the focus of intense research. Here, we report the molecular identification of a zebrafish maternal-effect mutation motley as Birc5b, a homolog of the mammalian Chromosomal Passenger Complex (CPC) component Survivin. The meiosis and mitosis defects in motley/ birc5b mutant embryos are consistent with failed CPC function, and additional defects in Astral Microtubule remodeling contribute to failures in the initiation of cytokinesis furrow ingression. Unexpectedly, the motley/birc5b mutation also disrupts cortical microfilaments and GP RNP aggregation during early cell divisions. Birc5b localizes to the tips of Astral Microtubules along with polymerizing cortical F-actin and the GP RNPs. Mutant Birc5b co-localizes with cortical F-actin and GP RNPs, but fails to associate with Astral Microtubule tips, leading to disorganized microfilaments and GP RNP aggregation defects. Thus, maternal Birc5b localizes to Astral Microtubule tips and associates with cortical F-actin and GP RNPs, potentially linking the two cytoskeletons to mediate Microtubule-microfilament reorganization and GP RNP aggregation during early embryonic cell cycles in zebrafish. In addition to the known mitotic function of CPC components, our analyse
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the chromosomal passenger protein birc5b organizes microfilaments and germ plasm in the zebrafish embryo
PLOS Genetics, 2013Co-Authors: Sreelaja Nair, Florence L Marlow, Elliott W Abrams, Lee Kapp, Mary C Mullins, Francisco PelegriAbstract:Microtubule-microfilament interactions are important for cytokinesis and subcellular localization of proteins and mRNAs. In the early zebrafish embryo, Astral Microtubule-microfilament interactions also facilitate a stereotypic segregation pattern of germ plasm ribonucleoparticles (GP RNPs), which is critical for their eventual selective inheritance by germ cells. The precise mechanisms and molecular mediators for both cytoskeletal interactions and GP RNPs segregation are the focus of intense research. Here, we report the molecular identification of a zebrafish maternal-effect mutation motley as Birc5b, a homolog of the mammalian Chromosomal Passenger Complex (CPC) component Survivin. The meiosis and mitosis defects in motley/birc5b mutant embryos are consistent with failed CPC function, and additional defects in Astral Microtubule remodeling contribute to failures in the initiation of cytokinesis furrow ingression. Unexpectedly, the motley/birc5b mutation also disrupts cortical microfilaments and GP RNP aggregation during early cell divisions. Birc5b localizes to the tips of Astral Microtubules along with polymerizing cortical F-actin and the GP RNPs. Mutant Birc5b co-localizes with cortical F-actin and GP RNPs, but fails to associate with Astral Microtubule tips, leading to disorganized microfilaments and GP RNP aggregation defects. Thus, maternal Birc5b localizes to Astral Microtubule tips and associates with cortical F-actin and GP RNPs, potentially linking the two cytoskeletons to mediate Microtubule-microfilament reorganization and GP RNP aggregation during early embryonic cell cycles in zebrafish. In addition to the known mitotic function of CPC components, our analyses reveal a non-canonical role for an evolutionarily conserved CPC protein in microfilament reorganization and germ plasm aggregation.
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Model of Birc5b function as a potential molecular mediator of Microtubule-microfilament interactions facilitating germ plasm RNP multimerization.
2013Co-Authors: Sreelaja Nair, Lee Kapp, Mary C Mullins, Florence Marlow, Elliott Abrams, Francisco PelegriAbstract:In wild-type embryos, Birc5b colocalizes with GP RNPs and growing F-actin seed filaments (A). Prior to the first mitosis, this link ensures peripheral movement and circumferential alignment of cortical microfilaments, which we hypothesize provide a substrate that facilitates GP RNP aggregation (B). This results in an aggregating wave of GP RNPs at ends of cortical Astral Microtubule (B, inserts). During the first embryonic cell division, GP RNP aggregates are recruited bilaterally into forming furrows at the tips contralateral furrow Astral Microtubule tips (C). In motley/birc5b mutants, F-actin seed filaments and GP RNPs associate with Birc5b (D) but Microtubule ends fail to contact this complex resulting in defective microfilament reorganization and GP RNP multimerization prior to (E) and during furrow formation (F). Failure to detect Microtubule tips at the cortex and the growth of furrow Microtubules past each other in motley/birc5b mutants are suggestive of a Birc5b-dependent severing function on Astral Microtubules (compare lower inserts in B–F) both prior to (B, E) and during (C, F) furrow formation. For clarity, inserts in B–F show select components: GP RNPs and Microtubules only (upper inserts) and Microtubules only (lower inserts). Abbreviations: GP: germ plasm; MT: Microtubules.
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motley/birc5b mutants fail to effectively multimerize GP RNPs.
2013Co-Authors: Sreelaja Nair, Lee Kapp, Mary C Mullins, Florence Marlow, Elliott Abrams, Francisco PelegriAbstract:Animal views of blastodisc cortex. In wild-type embryos (A–D) the GP RNP aggregation wave (bracket, A) coincides with cortical Astral Microtubule ends (B, bracket indicates the wavefront within the wave). GP RNP multimerization in wild-type embryos result in large GP RNP aggregates (C, D). In motley/birc5b mutants (E–H), cortical Microtubules are disorganized (F), and GP RNPs fail to multimerize effectively (G, H). In nocodazole-treated embryos (I–L), cortical Microtubules are absent (J) and GP RNP multimerization also fails (K, L). Semi-quantitative analysis of GP RNP aggregation showing similar multimerization failures in motley/birc5b and nocodazole-treated embryos compared to wild-type (M). Inset labels in panels A, E, I and C, G, and K indicate ROIs shown at higher magnifications next to the respective panels. Arrows in A, E and I indicate the radial direction, from the center of the blastodisc, along which Microtubules in B tend to be oriented in wild-type embryos. (N–R) consecutive confocal sections acquired with a z-step of 0.5 microns: z5 (N, most cortical), z6 (O) and z7 (P, Q, most internal). Yellow arrow shows a single Microtubule observed in Z6 (O), Z7 (P) and more internal (not shown) planes but not in z5 (N), which appears associated with an RNP in a multimerized aggregate (Q, R). White arrow indicates a pair of Microtubules that appear to converge on a different set of RNPs in the same aggregate (Q,R). The merge panel in R corresponds to Microtubules and RNPs for z7 to show the association of Microtubule tips with RNP aggregates.
Julie P I Welburn - One of the best experts on this subject based on the ideXlab platform.
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Microtubule end tethering of a processive kinesin 8 motor kif18b is required for spindle positioning
Journal of Cell Biology, 2018Co-Authors: Toni Mchugh, Agata A Gluszek, Julie P I WelburnAbstract:Mitotic spindle positioning specifies the plane of cell division during anaphase. Spindle orientation and positioning are therefore critical to ensure symmetric division in mitosis and asymmetric division during development. The control of Astral Microtubule length plays an essential role in positioning the spindle. In this study, using gene knockout, we show that the kinesin-8 Kif18b controls Microtubule length to center the mitotic spindle at metaphase. Using in vitro reconstitution, we reveal that Kif18b is a highly processive plus end-directed motor that uses a C-terminal nonmotor Microtubule-binding region to accumulate at growing Microtubule plus ends. This region is regulated by phosphorylation to spatially control Kif18b accumulation at plus ends and is essential for Kif18b-dependent spindle positioning and regulation of Microtubule length. Finally, we demonstrate that Kif18b shortens Microtubules by increasing the catastrophe rate of dynamic Microtubules. Overall, our work reveals that Kif18b uses its motile properties to reach Microtubule ends, where it regulates Astral Microtubule length to ensure spindle centering.
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Microtubule end tethering of a processive Kinesin-8 motor Kif18b is required for spindle positioning
bioRxiv, 2018Co-Authors: Toni Mchugh, Agata Gluszek-kustusz, Julie P I WelburnAbstract:Mitotic spindle positioning specifies the plane of cell division during anaphase. Spindle orientation and positioning is therefore critical to ensure symmetric division in mitosis and asymmetric division during development. The control of Astral Microtubule length plays an essential role in positioning the spindle. Here we show using gene knockout that the Kinesin-8 Kif18b controls Microtubule length to center the mitotic spindle at metaphase, with implications for symmetric division. Using an integrated approach, we reveal that Kif18b is a highly processive plus end-directed motor that uses a C-terminal non-motor Microtubule-binding region to accumulate at growing Microtubule plus ends. This non-motor Microtubule-binding region is regulated by phosphorylation to spatially control Kif18b accumulation at plus ends and is essential for Kif18b-dependent spindle positioning and regulation of Microtubule length. Here we demonstrate that Kif18b does not act as a Microtubule depolymerase and instead shortens Microtubules by increasing the catastrophe rate of dynamic Microtubules. Overall, our work reveals that Kif18b utilizes its motile properties to reach Microtubule ends where it regulates Astral Microtubule length to ensure spindle centering.
Sreelaja Nair - One of the best experts on this subject based on the ideXlab platform.
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The Chromosomal Passenger Protein Birc5b Organizes Microfilaments and Germ Plasm in the Zebrafish Embryo
2016Co-Authors: Sreelaja Nair, Mary C Mullins, Florence Marlow, Elliott Abrams, Francisco PelegriAbstract:Microtubule-microfilament interactions are important for cytokinesis and subcellular localization of proteins and mRNAs. In the early zebrafish embryo, Astral Microtubule-microfilament interactions also facilitate a stereotypic segregation pattern of germ plasm ribonucleoparticles (GP RNPs), which is critical for their eventual selective inheritance by germ cells. The precise mechanisms and molecular mediators for both cytoskeletal interactions and GP RNPs segregation are the focus of intense research. Here, we report the molecular identification of a zebrafish maternal-effect mutation motley as Birc5b, a homolog of the mammalian Chromosomal Passenger Complex (CPC) component Survivin. The meiosis and mitosis defects in motley/ birc5b mutant embryos are consistent with failed CPC function, and additional defects in Astral Microtubule remodeling contribute to failures in the initiation of cytokinesis furrow ingression. Unexpectedly, the motley/birc5b mutation also disrupts cortical microfilaments and GP RNP aggregation during early cell divisions. Birc5b localizes to the tips of Astral Microtubules along with polymerizing cortical F-actin and the GP RNPs. Mutant Birc5b co-localizes with cortical F-actin and GP RNPs, but fails to associate with Astral Microtubule tips, leading to disorganized microfilaments and GP RNP aggregation defects. Thus, maternal Birc5b localizes to Astral Microtubule tips and associates with cortical F-actin and GP RNPs, potentially linking the two cytoskeletons to mediate Microtubule-microfilament reorganization and GP RNP aggregation during early embryonic cell cycles in zebrafish. In addition to the known mitotic function of CPC components, our analyse
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the chromosomal passenger protein birc5b organizes microfilaments and germ plasm in the zebrafish embryo
PLOS Genetics, 2013Co-Authors: Sreelaja Nair, Florence L Marlow, Elliott W Abrams, Lee Kapp, Mary C Mullins, Francisco PelegriAbstract:Microtubule-microfilament interactions are important for cytokinesis and subcellular localization of proteins and mRNAs. In the early zebrafish embryo, Astral Microtubule-microfilament interactions also facilitate a stereotypic segregation pattern of germ plasm ribonucleoparticles (GP RNPs), which is critical for their eventual selective inheritance by germ cells. The precise mechanisms and molecular mediators for both cytoskeletal interactions and GP RNPs segregation are the focus of intense research. Here, we report the molecular identification of a zebrafish maternal-effect mutation motley as Birc5b, a homolog of the mammalian Chromosomal Passenger Complex (CPC) component Survivin. The meiosis and mitosis defects in motley/birc5b mutant embryos are consistent with failed CPC function, and additional defects in Astral Microtubule remodeling contribute to failures in the initiation of cytokinesis furrow ingression. Unexpectedly, the motley/birc5b mutation also disrupts cortical microfilaments and GP RNP aggregation during early cell divisions. Birc5b localizes to the tips of Astral Microtubules along with polymerizing cortical F-actin and the GP RNPs. Mutant Birc5b co-localizes with cortical F-actin and GP RNPs, but fails to associate with Astral Microtubule tips, leading to disorganized microfilaments and GP RNP aggregation defects. Thus, maternal Birc5b localizes to Astral Microtubule tips and associates with cortical F-actin and GP RNPs, potentially linking the two cytoskeletons to mediate Microtubule-microfilament reorganization and GP RNP aggregation during early embryonic cell cycles in zebrafish. In addition to the known mitotic function of CPC components, our analyses reveal a non-canonical role for an evolutionarily conserved CPC protein in microfilament reorganization and germ plasm aggregation.
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Model of Birc5b function as a potential molecular mediator of Microtubule-microfilament interactions facilitating germ plasm RNP multimerization.
2013Co-Authors: Sreelaja Nair, Lee Kapp, Mary C Mullins, Florence Marlow, Elliott Abrams, Francisco PelegriAbstract:In wild-type embryos, Birc5b colocalizes with GP RNPs and growing F-actin seed filaments (A). Prior to the first mitosis, this link ensures peripheral movement and circumferential alignment of cortical microfilaments, which we hypothesize provide a substrate that facilitates GP RNP aggregation (B). This results in an aggregating wave of GP RNPs at ends of cortical Astral Microtubule (B, inserts). During the first embryonic cell division, GP RNP aggregates are recruited bilaterally into forming furrows at the tips contralateral furrow Astral Microtubule tips (C). In motley/birc5b mutants, F-actin seed filaments and GP RNPs associate with Birc5b (D) but Microtubule ends fail to contact this complex resulting in defective microfilament reorganization and GP RNP multimerization prior to (E) and during furrow formation (F). Failure to detect Microtubule tips at the cortex and the growth of furrow Microtubules past each other in motley/birc5b mutants are suggestive of a Birc5b-dependent severing function on Astral Microtubules (compare lower inserts in B–F) both prior to (B, E) and during (C, F) furrow formation. For clarity, inserts in B–F show select components: GP RNPs and Microtubules only (upper inserts) and Microtubules only (lower inserts). Abbreviations: GP: germ plasm; MT: Microtubules.
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motley/birc5b mutants fail to effectively multimerize GP RNPs.
2013Co-Authors: Sreelaja Nair, Lee Kapp, Mary C Mullins, Florence Marlow, Elliott Abrams, Francisco PelegriAbstract:Animal views of blastodisc cortex. In wild-type embryos (A–D) the GP RNP aggregation wave (bracket, A) coincides with cortical Astral Microtubule ends (B, bracket indicates the wavefront within the wave). GP RNP multimerization in wild-type embryos result in large GP RNP aggregates (C, D). In motley/birc5b mutants (E–H), cortical Microtubules are disorganized (F), and GP RNPs fail to multimerize effectively (G, H). In nocodazole-treated embryos (I–L), cortical Microtubules are absent (J) and GP RNP multimerization also fails (K, L). Semi-quantitative analysis of GP RNP aggregation showing similar multimerization failures in motley/birc5b and nocodazole-treated embryos compared to wild-type (M). Inset labels in panels A, E, I and C, G, and K indicate ROIs shown at higher magnifications next to the respective panels. Arrows in A, E and I indicate the radial direction, from the center of the blastodisc, along which Microtubules in B tend to be oriented in wild-type embryos. (N–R) consecutive confocal sections acquired with a z-step of 0.5 microns: z5 (N, most cortical), z6 (O) and z7 (P, Q, most internal). Yellow arrow shows a single Microtubule observed in Z6 (O), Z7 (P) and more internal (not shown) planes but not in z5 (N), which appears associated with an RNP in a multimerized aggregate (Q, R). White arrow indicates a pair of Microtubules that appear to converge on a different set of RNPs in the same aggregate (Q,R). The merge panel in R corresponds to Microtubules and RNPs for z7 to show the association of Microtubule tips with RNP aggregates.
Toni Mchugh - One of the best experts on this subject based on the ideXlab platform.
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Microtubule end tethering of a processive kinesin 8 motor kif18b is required for spindle positioning
Journal of Cell Biology, 2018Co-Authors: Toni Mchugh, Agata A Gluszek, Julie P I WelburnAbstract:Mitotic spindle positioning specifies the plane of cell division during anaphase. Spindle orientation and positioning are therefore critical to ensure symmetric division in mitosis and asymmetric division during development. The control of Astral Microtubule length plays an essential role in positioning the spindle. In this study, using gene knockout, we show that the kinesin-8 Kif18b controls Microtubule length to center the mitotic spindle at metaphase. Using in vitro reconstitution, we reveal that Kif18b is a highly processive plus end-directed motor that uses a C-terminal nonmotor Microtubule-binding region to accumulate at growing Microtubule plus ends. This region is regulated by phosphorylation to spatially control Kif18b accumulation at plus ends and is essential for Kif18b-dependent spindle positioning and regulation of Microtubule length. Finally, we demonstrate that Kif18b shortens Microtubules by increasing the catastrophe rate of dynamic Microtubules. Overall, our work reveals that Kif18b uses its motile properties to reach Microtubule ends, where it regulates Astral Microtubule length to ensure spindle centering.
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Microtubule end tethering of a processive Kinesin-8 motor Kif18b is required for spindle positioning
bioRxiv, 2018Co-Authors: Toni Mchugh, Agata Gluszek-kustusz, Julie P I WelburnAbstract:Mitotic spindle positioning specifies the plane of cell division during anaphase. Spindle orientation and positioning is therefore critical to ensure symmetric division in mitosis and asymmetric division during development. The control of Astral Microtubule length plays an essential role in positioning the spindle. Here we show using gene knockout that the Kinesin-8 Kif18b controls Microtubule length to center the mitotic spindle at metaphase, with implications for symmetric division. Using an integrated approach, we reveal that Kif18b is a highly processive plus end-directed motor that uses a C-terminal non-motor Microtubule-binding region to accumulate at growing Microtubule plus ends. This non-motor Microtubule-binding region is regulated by phosphorylation to spatially control Kif18b accumulation at plus ends and is essential for Kif18b-dependent spindle positioning and regulation of Microtubule length. Here we demonstrate that Kif18b does not act as a Microtubule depolymerase and instead shortens Microtubules by increasing the catastrophe rate of dynamic Microtubules. Overall, our work reveals that Kif18b utilizes its motile properties to reach Microtubule ends where it regulates Astral Microtubule length to ensure spindle centering.
Patricia Wadsworth - One of the best experts on this subject based on the ideXlab platform.
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cell cycle dependent changes in Microtubule dynamics in living cells expressing green fluorescent protein alpha tubulin
Molecular Biology of the Cell, 2001Co-Authors: Nasser M Rusan, Carey Fagerstrom, Annemarie C Yvon, Patricia WadsworthAbstract:LLCPK-1 cells were transfected with a green fluorescent protein (GFP)-alpha tubulin construct and a cell line permanently expressing GFP-alpha tubulin was established (LLCPK-1alpha). The mitotic index and doubling time for LLCPK-1alpha were not significantly different from parental cells. Quantitative immunoblotting showed that 17% of the tubulin in LLCPK-1alpha cells was GFP-tubulin; the level of unlabeled tubulin was reduced to 82% of that in parental cells. The parameters of Microtubule dynamic instability were compared for interphase LLCPK-1alpha and parental cells injected with rhodamine-labeled tubulin. Dynamic instability was very similar in the two cases, demonstrating that LLCPK-1alpha cells are a useful tool for analysis of Microtubule dynamics throughout the cell cycle. Comparison of Astral Microtubule behavior in mitosis with Microtubule behavior in interphase demonstrated that the frequency of catastrophe increased twofold and that the frequency of rescue decreased nearly fourfold in mitotic compared with interphase cells. The percentage of time that Microtubules spent in an attenuated state, or pause, was also dramatically reduced, from 73.5% in interphase to 11.4% in mitosis. The rates of Microtubule elongation and rapid shortening were not changed; overall dynamicity increased 3.6-fold in mitosis. Microtubule release from the centrosome and a subset of differentially stable Astral Microtubules were also observed. The results provide the first quantitative measurements of mitotic Microtubule dynamics in mammalian cells.
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cell cycle dependent changes in Microtubule dynamics in living cells expressing green fluorescent protein α tubulin
Molecular Biology of the Cell, 2001Co-Authors: Nasser M Rusan, Carey Fagerstrom, Annemarie C Yvon, Patricia WadsworthAbstract:LLCPK-1 cells were transfected with a green fluorescent protein (GFP)-α tubulin construct and a cell line permanently expressing GFP-α tubulin was established (LLCPK-1α). The mitotic index and doubling time for LLCPK-1α were not significantly different from parental cells. Quantitative immunoblotting showed that 17% of the tubulin in LLCPK-1α cells was GFP-tubulin; the level of unlabeled tubulin was reduced to 82% of that in parental cells. The parameters of Microtubule dynamic instability were compared for interphase LLCPK-1α and parental cells injected with rhodamine-labeled tubulin. Dynamic instability was very similar in the two cases, demonstrating that LLCPK-1α cells are a useful tool for analysis of Microtubule dynamics throughout the cell cycle. Comparison of Astral Microtubule behavior in mitosis with Microtubule behavior in interphase demonstrated that the frequency of catastrophe increased twofold and that the frequency of rescue decreased nearly fourfold in mitotic compared with interphase cells. The percentage of time that Microtubules spent in an attenuated state, or pause, was also dramatically reduced, from 73.5% in interphase to 11.4% in mitosis. The rates of Microtubule elongation and rapid shortening were not changed; overall dynamicity increased 3.6-fold in mitosis. Microtubule release from the centrosome and a subset of differentially stable Astral Microtubules were also observed. The results provide the first quantitative measurements of mitotic Microtubule dynamics in mammalian cells.
