Biology subjects

Chumakova, L.

Publications and source records attributed to Chumakova, L..

4 recordsLinked to original sources

bioRxiv2019

The walkoff effect: cargo distribution implies motor type in bidirectional microtubule bundles

Cells rely on molecular motors moving along an ever-shifting network of polymers (microtubules) for the targeted delivery of cell organelles to biologically-relevant locations. We present a stochastic model for a molecular motor stepping along a bidirectional bundle of microtubules, as well as a tractable analytical model. Using these models, we investigate how the preferred stepping direction of the motor (parallel or antiparallel to the microtubule growth, corresponding to kinesin and dynein motor families) quantitatively and qualitatively affects the cargo delivery. We predict which motor type is responsible for which cargo type, given the experimental distribution of cargo in the cell, and report experimental findings which support this guideline for motor classification.

cell biology↗

bioRxiv2019

Cellular crowding guides and debundles the microtubule cytoskeleton

Cytoplasm is densely packed with macromolecules causing cellular crowding, which alters interactions inside cells and differs between biological systems. Here we investigate the impact of crowding on microtubule cytoskeleton organization. Using mathematical modelling, we find that only anisotropic crowding affects the mean microtubule direction, but any crowding reduces the number of microtubules that form bundles. We validate these predictions in vivo using Drosophila follicular epithelium. Since cellular components are transported along microtubules, our results identify cellular crowding as a novel regulator of this transport and cell organization.

cell biology↗

bioRxiv2019

Inferring punctuated evolution in the learned songs of African sunbirds

Signals used in animal communication, especially those that are learned, are thought to be prone to rapid and/or regular evolution. It has been hypothesized that the evolution of song learning in birds has resulted in elevated diversification rates, as learned song may be subject to especially rapid evolution, and song is involved in mate choice. However, we know little about the evolutionary modes of learned song divergence over timescales relevant to speciation. Here we provide evidence that aspects of the territorial songs of Eastern Afromontane sky island sunbirds Cinnyris evolve in a punctuated fashion, with periods of stasis, on the order of hundreds of thousands of years or more, broken up by strong evolutionary pulses. Stasis in learned songs is inconsistent with learned traits being subject to constant or frequent change, as would be expected if selection does not constrain song phenotypes, or if novel phenotypes are frequently advantageous. Learned song may instead follow a process resembling peak shifts on adaptive landscapes. While much research has focused on the potential for rapid evolution in bird song, our results suggest that selection can tightly constrain the evolution of learned songs over fairly long timescales. More broadly, these results demonstrate that some aspects of highly variable, plastic traits can exhibit punctuated evolution, with stasis over fairly long time periods.

evolutionary biology↗

bioRxiv2019

Robustness of bidirectional microtubule network self-organization

Robustness of biological systems is crucial for their survival, however, for many systems its origin is an open question. Here we analyze one sub-cellular level system, the microtubule cytoskeleton. Microtubules self-organize into a network, along which cellular components are delivered to their biologically relevant locations. While individual microtubule are highly dynamic with their dynamics depends on the organism environment and genetics, network sensitivity to this dynamics would result in pathologies. Combining mathematical modelling with genetic manipulations in Drosophila, we show that the microtubule self-organization indeed does not depend on dynamics of individual microtubules, and thus is robust on the tissue level. We demonstrate the origin of this robustness via a mathematical model, suggesting this being a generic mechanism.

cell biology↗