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ATMscience

My interests

I am broadly interested in quantitative cell biology and the physics of living systems. I am particularly fascinated with the cytoskeleton, especially microtubules, and also by the physical properties of the cytoplasm. While I don't have a favorite organism, I have worked with a variety of model organisms (such as yeast, plants, and mammalian cells) as well as non-model organisms (such as Spirostomum) and in vitro systems. My primary investigative method is microscopy, and I have spent thousands of hours applying it in various forms.


I have a broad interest in multiple fundamental research topics
•    Understanding the roles and regulation of cytoskeleton organization and dynamics
•    Describing the physical properties of the cytoplasm and their regulation
•    Deciphering how the properties of the cytoplasm impact cellular functions

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The cytoskeleton consists of a network of filaments assembled from soluble proteins, and I am fascinated by the dynamic properties of these filaments. These filaments, particularly microtubules, alternate between phases of growth and shrinkage, switching stochastically between the two. These fundamental and intrinsic behaviors have been reproduced in vitro for decades. However, in living cells, microtubule dynamics are regulated by a myriad of factors, as well as by the physical properties of the surrounding environment. Understanding how a cell organizes its network of microtubules—polymerizing them in specific regions while depolymerizing them in others—is a central question for unraveling cellular architecture.

For my Ph.D. work, I focused on one such regulator of microtubule dynamics: the EB1 protein from Arabidopsis thaliana (Molines et al., 2018, Molines et al., 2020). While EB1 proteins from other eukaryotes (yeast, mammals, flies) have been extensively studied both in cells and in vitro, the plant ortholog differs in sequence and has been less well explored. My research demonstrated that EB1 regulates microtubule network organization in Arabidopsis (Molines et al., 2018) and showed that its effects on microtubule dynamics in vitro differ from those of the mammalian version (Molines et al., 2020).

Microtubules re-organization blue light treatment arabidopsis

Microtubule network reorganization upon blue light treatment in Arabidopsis thaliana epidermal hypocotyl cell.
Lindeboom et al., 2013, Science.

Model of the Bacterial Cytoplasm.
McGuffee and Elcock, 2010, PLoS Comput Biol 

The cytoplasm is a complex environment, composed of proteins, carbohydrates, nucleic acids, and ions, all at high concentrations. It is both crowded and viscous, with proteins in close proximity to one another. Additionally, it is a dynamic environment in which energy is constantly consumed to drive molecular motion. These properties arise from the composition of the cytoplasm, with higher concentrations leading to increased crowding and viscosity. However, we still lack a detailed understanding of how its physical properties emerge and how its composition influences them. It remains unclear whether cells have evolved specific molecular mechanisms to detect and adjust for changes in cytoplasmic viscosity or crowding, or if these properties are regulated passively. A significant part of my postdoctoral research has focused on gaining a deeper understanding of the physical properties of the cytoplasm in Schizosaccharomyces pombe (fission yeast) (Garner, Molines et al., 2023).

The physical properties of the cytoplasm are fundamental to cellular biology. Viscosity and crowding, for example, are bulk properties of a solution known to influence various biochemical reactions. In vitro, enzymatic reactions typically slow down with increased viscosity and speed up with increased crowding. This suggests that metabolic reactions occurring within the cytoplasm could be sensitive to its physical properties. However, we still lack a detailed understanding of which reactions are affected, and to what extent. This gap in knowledge arises partly because the actual physical properties of the cytoplasm are not well characterized, and partly because it is challenging to manipulate these properties within living cells. A key focus of my postdoctoral research was to use osmotic shocks as a method to acutely alter cytoplasmic properties. This approach allowed us to demonstrate that microtubule dynamics are sensitive to cytoplasmic viscosity in eukaryotic cells, including yeast, mammals, and plants (Molines et al., 2022).

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Potential effect of crowding on proteins behavior.
From Kuznetsova et al., 2014

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