Biology subjects

Nader, G. P. F.

Publications and source records attributed to Nader, G. P. F..

4 recordsLinked to original sources

bioRxiv2026

Osmotic Coupling of Mechanics and Epigenetics Regulates Chromatin Phase Organization

Cells experience epigenetic, osmotic, and mechanical perturbations that reorganize chromatin, yet how these distinct cues are integrated into a common physical response of the nucleus remains unclear. Here, we identify nuclear hydration as a central state variable that links microenvironmental perturbations to chromatin phase organization and nuclear mechanics. We develop a non-equilibrium mesoscale model that couples chromatin elasticity, water transport, and epigenetic reaction-diffusion kinetics. In this framework, chromatin behaves as a deformable polymer that segregates into coexisting water-rich euchromatic and water-poor heterochromatic phases, whose compositions and morphologies are regulated by hydration-dependent swelling, elastic strain, and histone-mark interconversion. The model predicts that epigenetic perturbations, osmotic shocks, and volume-changing mechanical loads reorganize chromatin by shifting intranuclear water content, nuclear volume, and euchromatin-heterochromatin phase balance. It further predicts that anisotropic forces impose directional strain, driving heterochromatin elongation, alignment, and lamellar transitions. Quantitative comparisons with super-resolution imaging, AFM and chromatin-accessibility measurement - across pharmacological, osmotic, and mechanical perturbations including confinement and micropatterning - support these predictions. Together, our results establish a chemo-mechano-osmotic framework in which nuclear hydration integrates biochemical and biophysical cues to regulate chromatin organization across scales.

biophysics↗

bioRxiv2026

Coupled nucleoplasmic flows and envelope expansion govern the mechanical resistance of the nucleus

In recent year, it became clear that the cell nucleus can undergo large deformations, during immune cell migration and tumor growth. These deformations generate signals that allow cells to sense their environment and adapt to it. How cells cope with and respond to large deformations thus strongly depends on the nuclear mechanics, but our understanding of the physical properties of the nucleus remains incomplete. In particular, it is not clear how the nuclear volume responds to deformation. Here we combine controlled confinement assays, high-resolution imaging and atomic force microscopy with theoretical modelling to propose a physical model of the cell nucleus that accounts for its surface and bulk properties and addresses both steady-state and transient regimes. Our results establish the nucleus as a poroelastic body in which mechanics are dominated by the envelope and dynamics by the chromatin, and suggest that regulating water permeability may be as important as softening the envelope for cells migrating rapidly through dense tissues.

biophysics↗

bioRxiv2022

Mechanical Stimulation Shapes the Immunoregulatory Properties of Dendritic Cells

Motile cells such as immune and cancer cells experience large deformation events that result from the physical constraints they encounter while migrating within tissues or circulating between organs. It has become increasingly clear that these cells can survive and adapt to these changes in cell shape using dedicated shape sensing pathways. However, how shape sensing impacts their function and fate remains largely unknown. Here we identify a shape sensing mechanism that couples cell motility to expression of CCR7, the chemokine receptor that guides immune cells to lymph nodes. We found that this mechanism is controlled by the lipid metabolism enzyme cPLA2, requires an intact nuclear envelop and exhibits an exquisitely sensitive activation threshold tuned by ARP2/3 and its inhibitor Arpin. We further show that shape sensing through the ARP2/3-cPLA2 axis controls Ikk{beta}-NF{kappa}B-dependent transcriptional reprogramming of dendritic cells, which instructs them to migrate to lymph nodes in an immunoregulatory state compatible with their homeostatic tolerogenic function. These results highlight that the cell shape changes experienced by motile cells evolving within the complex environment of tissues can dictate their behavior and fate.

cell biology↗

bioRxiv2022

Nuclear envelope disruption triggers hallmarks of aging in lung alveolar macrophages

Aging is characterized by gradual immune dysfunction and increased risk for many diseases, including respiratory infections. Genomic instability is thought to play a central role in the aging process but the mechanisms that damage nuclear DNA in aging are insufficiently defined. Cells that migrate or reside within confined environments experience forces applied to their nucleus, leading to transient nuclear envelope (NE) ruptures. NE ruptures are associated with DNA damage, and Lamin A/C is required to limit these events. Here, we show that Lamin A/C protects lung alveolar macrophages from NE rupture and hallmarks of aging. Lamin A/C ablation in immune cells results in a selective depletion of lung alveolar macrophages (AM) and a heightened susceptibility to influenza infection. Lamin A/C-deficient AM that persist display constitutive nuclear envelope rupture marks, DNA damage and p53-dependent senescence. In wild-type mice, we found that AM migrate within constricted spaces in vivo, at heights that induce NE rupture and DNA damage. AM from aged wild-type mice and from Lamin A/C-deficient mice share an upregulated lysosomal signature with CD63 expression, and we find that CD63 is required to clear damaged DNA in macrophages. We propose that induction of genomic instability by NE disruption represents a mechanism of aging in alveolar macrophages.

immunology↗