Journal Club – May 2019

Spindle Heterogeneity, Microtubule Search and Capture, and Bulk Actin Waves

Must Read

Mechanically Distinct Microtubule Arrays Determine the Length and Force Response of the Meiotic Spindle

Takagi et al. | Developmental Cell
The spindle is a remarkable macromolecular machine comprised of dynamic microtubules and associated factors. Given its critical job in driving chromosome segregation, the spindle is robust to mechanical perturbations, maintaining a near constant structure despite a barrage of internal and external forces. Previous works have delved into the architecture and dynamics that give rise to the steady-state spindle, but a map of how microtubules in various regions of the spindle respond to forces is needed. In this study, the Shimamoto lab locally deformed spindles in Xenopus egg extracts with force-calibrated microneedles while simultaneously imaging single microtubules labeled with fluorescent tubulin speckles. The mechanical responses of microtubules were observed to differ depending on their location within the spindle, with the middle of each spindle half being more compliant and fluid-like than than pole and equatorial regions. This mechanical heterogeneity was further demonstrated to emerge from the microtubule crosslinking activities of kinesin-5 and dynein, providing a link between spindle architecture and mechanics.
Discussion Point – The authors propose that the compliant region located in the middle of each spindle half acts as a buffer zone – allowing the spindle to make necessary adjustments in response to physical perturbations without disrupting activity at the pole and equatorial business ends.
Preview by Juraj Simunić and Iva Tolić

Metaphase Spindle: Architecture, Stiffness and Viscoelasticity


Designing A Rigorous Microscopy Experiment: Validating Methods And Avoiding Bias

Important considerations for one of the mostly widely used techniques in cell biology – from sample preparation to post-acquisition processing.
Jost and Waters  |  Journal of Cell Biology

Reviews and Perspectives

Microtubule Assembly From Single Flared Protofilaments – Forget The Cozy Corner?

Cooperative assembly of FtsZ, the bacterial tubulin homolog, may help explain new models of microtubule assembly characterized by the elongation of single protofilaments.
Erickson  |  Biophysical Journal

Conference Watch

French Microtubule Network 2019
July 1-2, 2019
Rennes, France
PurSolutions Logo is a proud sponsor of the of the 4th annual French microtubule network meeting.

Journal Club Picks

  • Multiple microtubule arrays in a single interphase cell are organized by a balance of forces as revealed by centrosome ablation in naturally multinucleated cells.
    Odell et al. |  Koonce Lab |  Molecular Biology of the Cell
  • Excessive astral microtubule-generated forces can damage the genome during mitosis.
    Estrem and Moore |  Moore Lab |  Molecular Biology of the Cell
  • Branched microtubule arrays are shaped by the biased deposition of nucleation sites near microtubule minus ends.
    Thawani et al. |  Stone, Shaevitz, and Petry Labs | eLife
  • Tubulin acetylation inside the microtubule lumen is likely causative of enhanced stability as determined by near atomic-resolution cryo-EM maps.
    Eshun-Wilson et al. | Nogales Lab | PNAS
  • The non-motile ciliary kinesin Kif7 recognizes and stabilizes GTP-tubulin to promote its own microtubule tip tracking.
    Jiang et al. | Subramanian Lab | Developmental Cell
  • The centrosome mediates crosstalk between the microtubule and actin networks as they reorganize during mitosis.
    Farina et al. | Baum Lab | The EMBO Journal
  • Platinum replica electron microscopy reveals the ultrastructure of the actin cytoskeleton at sites of mitochondrial constriction.
    Yang and Svitkina | Svitkina Lab | Nature Cell Biology
  • Biophysical models of cytoskeletal reorganization predict mitotic spindle assembly in the absence of molecular motors.
    Lamson et al. | Betterton Lab | Biophysical Journal
  • A microtubule search and capture mechanism outside of mitosis is important for adaptive immune responses.
    Sarkar et al. | Paul Lab | Biophysical Journal
  • A genome-scale CRISPR–Cas9 fitness screen across hundreds of cancer cell lines identifies several tubulin genes as priority targets in the development of context-specific cancer drugs.
    Behan et al. | Yusa and Garnett Labs | Nature
  • Coordinated actin polymerization transmits a wave of cytoplasmic streaming important for ooplasm-yolk segregation during embryogenesis.
    Shamipour et al. | Hannezo and Heisenberg Labs | Cell

Our opinions are our own and do not represent the views or endorsement of the authors cited.

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