Biology subjects

Alsina, A.

Publications and source records attributed to Alsina, A..

4 recordsLinked to original sources

bioRxiv2026

Shared neurogenesis onset is sufficient to explain bilateral matching in the vertebrate retina

Bilateral symmetry is a hallmark of many paired organs and often essential for optimal functionality. The vertebrate eyes are a prominent example of this, as the matched development of the two retinas is required for accurate visual processing. While macroscopic aspects of symmetry emergence across systems have been investigated, how bilateral matching is maintained once cells start to differentiate remains less understood. Here we address this question using the zebrafish retina as a model to follow neurogenic programs in vivo at single-cell resolution. We perform quantitative 3D live imaging of both retinas simultaneously and directly compare neurogenesis onset and propagation within and across embryos. We find that neurogenic waves initiate at the retinal poles and progress towards the mid-retina in a conserved spatiotemporal pattern. Within embryos, the two eyes exhibit highly similar neurogenesis dynamics when it comes to timing of neurogenesis onset, cell number increase, and spatial wave progression. Across embryos, however, variability is larger. While these observations hint at active inter-retinal coordination, a stochastic model predicts that a shared onset of neurogenesis can be sufficient to explain bilateral matching. Targeted genetic perturbation experiments support this prediction. We find that altering wave propagation affects patterning but not bilateral similarity. Disrupting neurogenesis onset timing, however, reduces bilateral symmetry between eyes. Thus, the combination of experiment and theory identifies synchronized neurogenesis onset as a key determinant of bilateral symmetry, revealing a minimal principle for how reproducible development of paired organs can emerge from stochastic processes.

developmental biology↗

bioRxiv2025

Model-based inference of cell cycle dynamics captures alterations of the DNA replication programme

The cell cycle of eukaryotic cells consists of several processes that must be carefully orchestrated and completed in a timely manner. Alterations in cell cycle dynamics have been linked to the onset of various diseases, underscoring the need for quantitative methods to analyze cell cycle progression. Here, using a combination of high-throughput experimental data and theoretical modeling, we develop RepliFlow, a model-based approach to infer cell cycle dynamics from flow cytometry data of DNA content in asynchronous cell populations. We model the DNA content distribution as the result of both noisy single-cell measurements and the populations age structure. We show that RepliFlow captures not only changes in the length of each cell cycle phase but also alterations in the underlying DNA replication dynamics. RepliFlow is species-agnostic and recapitulates results from more sophisticated analyses based on nucleotide incorporation. Finally, we propose a minimal DNA replication model that enables to derive microscopic insights about origin firing rates and replication fork speed from population-wide DNA content measurements. Our work presents a scalable framework for inferring cell cycle dynamics from flow cytometry data, enabling the characterization of replication program alterations.

systems biology↗

bioRxiv2020

Specialisation and plasticity in a primitively social insect

Biological systems not only have the remarkable capacity to build and maintain complex spatio-temporal structures in noisy environments, they can also rapidly break up and rebuild such structures. How such systems can simultaneously achieve both robust specialisation and plasticity is poorly understood. Here we use primitive societies of Polistes wasps as a model system where we experimentally perturb the social structure by removing the queen and follow the re-establishment of the social steady state over time. We combine a unique experimental strategy correlating time-resolved measurements across vastly different scales with a theoretical approach. We show that Polistes integrates antagonistic processes on multiple scales to distinguish between extrinsic and intrinsic perturbations and thereby achieve both robust specialisation and rapid plasticity. The long-term stability of the social structure relies on dynamic DNA methylation which controls transcriptional noise. Such dynamics provide a general principle of how both specialization and plasticity can be achieved in biological systems. One Sentence SummaryA primitive social insect simultaneously achieves specialisation and plasticity by integrating antagonistic dynamics on different scales. HighlightsO_LIWe employ a unique experimental approach correlating dynamics of societies, individuals, and epigenetic gene regulation C_LIO_LIA social insect simultaneously achieves specialisation and plasticity by integrating antagonistic processes on different spatial scales C_LIO_LIRegulation of population-level noise by DNA methylation ensures long-term stability of phenotypic specialisation C_LI

biophysics↗

bioRxiv2016

Balance of microtubule stiffness and cortical tension determines the size of blood cells with marginal band across species

The fast blood stream of animals is associated with large shear stresses. Consequently, blood cells have evolved a special morphology and a specific internal architecture allowing them to maintain their integrity over several weeks. For instance, non-mammalian red blood cells, mammalian erythroblasts and platelets have a peripheral ring of microtubules, called the marginal band, that flattens the overall cell morphology by pushing on the cell cortex. In this article, we model how the shape of these cells stems from the balance between marginal band elasticity and cortical tension. We predict that the diameter of the cell scales with the total microtubule polymer, and verify the predicted law across a wide range of species. Our analysis also shows that the combination of the marginal band rigidity and cortical tension increases the ability of the cell to withstand forces without deformation. Finally, we model the marginal band coiling that occurs during the disc-to-sphere transition observed for instance at the onset of blood platelet activation. We show that when cortical tension increases faster than crosslinkers can unbind, the marginal band will coil, whereas if the tension increases slower, the marginal band may shorten as microtubules slide relative to each other.\n\nSignificance StatementMany blood cells have a discoidal shape, which is essential for them to function properly within the organism. For some cells, such as blood platelets, this shape is due to the interplay between the elasticity of the marginal band, which is a closed ring of stiff filaments called microtubules, and the tension of the cell cortex, a polymer scaffold associated with the plasma membrane. Dmitrieff et al. examined how cell size is determined by the mechanical balance between these two components. Remarkably, the theory is confirmed over nearly three orders of magnitudes, by data collected from 25 species. The theory also shows how the composite structure is adapted to resist transient mechanical challenges, as encountered in the blood stream.

biophysics↗