Laboratoire Matière et Systèmes Complexes

There will be a live diffusion with Zoom :

Monday January 30th, 11h30 in room 454 A.

Please contact Jean-Baptiste Manneville to attend the visio-seminar.

Enhanced cell viscosity as a marker of premature senescence induced by lamin A/C alterations

Emmanuèle Helfer

Aix Marseille Univ, CNRS, CINAM, Turing Centre for Living Systems

Lamin A/C is a constituent of the nuclear envelope that contributes to nucleus mechanical properties such as stability, shape, and rigidity. Mutations in lamin A/C induce pathologies called laminopathies, with common phenotypes such as nuclear abnormal shape or cell premature senescence (i.e. premature ageing). Laminopathies display varying severity and can be tissue-specific, like Type 2 Familial Partial Lipodystrophy (FPLD2) where only adipose tissues are affected, or multi-systemic, like Progeria where the entire body ages prematurely. The relationship between lamin A/C mutations, mechanical alterations in cells, and laminopathy severity remains unknown, resulting in lack of diagnosis and treatment. We studied human primary fibroblasts with altered lamin A/C and displaying premature senescence : i) cells from healthy individual treated with Atazanavir (AZN), a protease inhibitor which alters lamin A/C production and artificially induces senescence [1] ; and ii) cells issued from FPLD2 patients carrying the lamin A/C R482W mutation [2]. We developed a microfluidic device to quantify the deformation dynamics of the cells passing through specifically-designed constrictions. We combined high-throughput microfluidic measurements with semi-automated image analysis and a rheological model to extract cell rheological properties [3]. We also treated the cells with drugs to destabilize the cytoskeleton and decipher its contribution to the cell response. We show that prematurely senescent fibroblasts mainly exhibit a more viscous behavior than non-senescent cells. In our setup, viscosity – but not rigidity – dominates the cell deformation dynamics in the constrictions. The viscous behavior is not driven exclusively by the nucleus, but rather by actin, and, unexpectedly, by microtubules. Our results suggest that lamin A/C can also control the cellular mechanical response through a modulation of the nucleo-cytoskeleton links. Despite affecting lamin A/C ad inducing premature senescence in a way similar to the mutation, AZN treatment induces milder biological and rheological phenotypes. Interestingly, cells from FPLD2 patients, both carrying the same mutation, display different behavior : cells from one patient were much more viscous, and incidentally, this patient had a more severe form of FPLD2. Hence, our setup might be sensitive to patient state severity. Our microfluidic device opens the way towards a simple, fast, and inexpensive mechanics-based test to identify predisposition to premature aging.

[1] N Bonello-Palot, et al. Atherosclerosis 237, 45–52 (2014) [2] A Decaudain, et al. The J. Clin. Endocrinol. & Metab. 92, 4835–4844 (2007) [3] K Guevorkian, et al. Phys. Rev. Lett. 104, 218101 (2010)