Thesis defense
Title : Premature senescence by lamin A/C alterations: fast probing the viscoelasticity at the cellular and sub-cellular scale
Members of jury :
– Charlotte Rivière, Institut Lumière-Matière, Lyon (Reviewer)
– Matthieu Piel, Institut Curie, Paris (Reviewer)
– Atef Asnacios, Laboratoire Matière et Systèmes Complexes, Paris (Committee member)
– Giovanni Cappello, Laboratoire Interdisciplinaire de Physique, Grenoble (Chair-person)
– Catherine Badens, Marseille Medical Genetics, Marseille (Committee member)
– Jean-François Rupprecht, Centre de Physique Théorique, Marseille (committee member)
– Emmanuèle Helfer, Centre Interdisciplinaire de Nanoscience de Marseille, Marseille (PhD supervisor)
Abstract :
Lamin A/C is a constituent of the nuclear envelope. It contributes to nuclear mechanical properties such as shape and rigidity. Mutations in LMNA gene induce pathologies called laminopathies which display varying degree of severity. The most severe form is Hutchinson-Gilford Progeria Syndrome (HGPS) where the entire organism ages prematurely. At the cellular level, laminopathies share phenotypes such as misshaped nuclei or premature senescence. Most studies have focused on HGPS, showing an increased rigidity of the nucleus. Whether this is HGPS-specific or common to all laminopathies is not answered yet. The relationship between LMNA mutations, mechanical alterations in cells and laminopathy severity remains unknown, resulting in lack of diagnosis and treatment.
My PhD aimed at investigating this relationship at the cell scale, in the second timescale. I developed a microfluidic device to quantify the deformation dynamics of cells passing through constrictions. We combined microfluidic measurements with semi-automated image analysis and a rheological model to extract cellular mechanical properties.
We studied prematurely senescent fibroblasts from patients carrying the LMNA R482W mutation and fibroblasts from a healthy individual treated with a protease inhibitor known to alter lamin A/C production. Prematurely senescent fibroblasts exhibit a higher viscosity which dominates the deformation dynamics of the cells in constrictions. The viscous behavior not only depends on the nucleus but also on the actin and microtubule networks.
Our microfluidic device opens the way towards a simple, fast, and inexpensive mechanics-based test to identify predisposition to premature aging.
