(Relatively) Recent Lab News:
Adam Horn joins the lab as a visiting postdoc. Welcome, Adam!
Adriana Golding defends her Ph.D. thesis. Congratulation, Adriana!
Zac Swider joins the lab as a graduate student working on cortical excitability. Welcome, Zac!
Ani Michaud joins the lab as a graduate student working on cortical excitability. Welcome, Ani!
Tom Burke joins the lab as a postdoc working on cell repair. Welcome, Tom!
(Relatively) Recent Lab Tweets:
(Relatively) Recent Lab Videos:
Ani and Henry's light sheet video of cortical excitability in a frog oocyte was a winner in the 2019 UW-Madison "Cool Science Photo/Video" contest:
This video featuring the Bement Lab's work on single-cell wound repair was a finalist in the 2014 ASCB Celldance competition:
(Relatively) Recent papers:
Spindle–F-actin interactions in mitotic spindles in an intact vertebrate epithelium
In this paper Angela Kita and Zac Swider tackled a longstanding question in cell biology: Does F-actin play a role in mitotic spindle assembly? Despite numerous attempts over the past 50 years, convincing evidence for spindle-associated F-actin filaments has been largely lacking. To address this question, Angela developed and rigorously tested a fixation protocol with the goal of preserving both actin filaments and microtubules. Angela showed that not only do actin filaments pervade the mitotic spindle, they are present in distinct populations throughout the entire cell cycle (seen below). Meanwhile Zac took a live imaging approach, which revealed that the actin filaments detected in fixed samples actually consist of two populations of F-actin: A relatively stable population that appears to be mechanically coupled to the spindle itself, and a population of dynamic F-actin cables that rapidly polymerize from the cell cortex and target the spindle poles (also seen below). Together these results show that the participation of actin filaments in mitotic spindle assembly is far more extensive than commonly believed. We hypothesize that these populations may be involved in spindle positioning and/or mitotic progression. For more details read the whole paper here: pdf
An interaction between myosin-10 and the cell cycle regulator Wee1 links spindle dynamics to mitotic progression in epithelia
Previous work by Sarah Woolner showed that depletion of myosin-10, an unconvential myosin, results in deranged spindle morphology and motility (see pdf). Josh Sandquist and Matt Larson followed up on this finding and identified Wee1, a conserved inhibitor of Cdk1, as a binding partner for myosin-10. Surprisingly, they found that Myo-10 perturbations delayed anaphase onset in a Wee1-dependent manner, that perturbing Myo-10 increased Wee1's inhibitory activity towards Cdk1, and that inhibited Cdk1 concentrated at cell-cell junctions. Together these results suggest a model in which an interaction between Myo-10 and Wee1 link anaphase onset with the stereotypical spindle dance described by Matt previously. For more details read the whole paper here: pdf
Automated mitotic spindle tracking suggests a link between spindle dynamics, spindle orientation, and anaphase onset in epithelial cells
Matt Larson developed an automated spindle-tracking software - the "Spindlometer" - and applied it to address an ongoing question: How do spindles within an epithelium achieve their proper orientation, typically along the long axis of the cell and parallel with the epithelium, before making the decision to enter anaphase? By combining a reproducible imaging regime with his unbiased analysis pipline, Matt found that spindles within an epithelium undergo a stereotypical "dance" prior to anaphase onset. This dance is characterized by a low slow rotation from their initial orientation to their final orientation, followed by a series of rapid oscillations that repeatedly bring the spindle poles into close proximity to the cell cortex. We hypothesize that these cortical contacts may allow the spindle to sense its final orientation and either execute or delay anaphase onset as appropriate. For more details read the whole paper here: pdf
Membrane dynamics during cellular wound repair
Nick Davenport takes a look at membrane dynamics during single-cell wound repair with unprecedented spatiotemporal resolution. This work provides the first direct evidence for "patching" at the wound site: The local fusion of intracellular compartments, which limits the diffusion of extracellular material into the wound. The time series below shows an oblique view of the wound response in a Xenopus oocyte; intracellular vesicles around the wound are labeled with the C2 domain of PKCβ, and the extraceullar fluid is labeled with fluorescent dextran. Nick was awarded the 2017 MBoC Paper of the Year Award by the Molecular Biology of the Cell (MBoC) Editorial Board. For more details read the whole paper here: pdf
Activator–inhibitor coupling between Rho signalling and actin assembly makes the cell cortex an excitable medium
The Bement, Miller, von Dassow, and Goryachev labs collectively characterized, tested, and modeled a reaction-diffusion system which manifests at the cell cortex as self-propagating waves of active Rho, F-actin, and other core components of the cytokinetic machinery. We hypothesize that this sytem explains key features of cytokinesis, including its sensitivity and regulation by the cell cycle. The image below illustrates an example of cortical excitability in a starfish oocyte during Meiosis II. For more information see the Cortical Excitability page of the lab website, or read the whole paper here: pdf