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BP: Fachverband Biologische Physik

BP 35: Active Matter V (joint session BP/DY)

BP 35.3: Vortrag

Freitag, 22. März 2024, 10:00–10:15, H 1028

Self-assembly of myofibrils in muscle cells — Francine Kolley¹, Ian D. Estabrook¹, Clara Sidor², Clement Rodier², Frank Schnorrer², and •Benjamin M. Friedrich¹ — ¹Physics of Life, TU Dresden, Germany — ²IBDM, Marseilles, France

Voluntary motions and heartbeat in animals is driven by contractions of myofibrils, millimeter-long acto-myosin bundles with characteristic periodic patterns of micrometer-sized sarcomeres. Yet, the physical mechanisms that drive the self-assembly of these “cytoskeletal crystals” are not understood. Here, we report data demonstrating that myosin molecular motors and actin-crosslinking Z-disc proteins form sarcomeric patterns first, while actin becomes polarity-sorted only hours later [1]. This data informs mathematical models of sarcomere self-assembly that are able to replicate periodic sarcomeric patterns, either through (i) non-local interactions between spatially-extended myosin filaments and Z-disc proteins, which bind to an actin scaffold, or (ii) catch-bond behavior of the prominent Z-protein α-actinin in response to active myosin forces. Both models are robust to small-number fluctuations for a wide parameter range in agent-based simulations, providing plausible mechanisms of early sarcomere self-assembly.

Next, even after the establishment of sarcomeric patterns, new sarcomeres are added to myofibrils, despite these being under mechanical tension. We report a new mechanism of controlled “self-rupture” in which a mother sarcomere divides into two daughter sarcomeres by splitting its myosin stack, and establishing a new Z-disc in between.

[1] https://www.biorxiv.org/content/10.1101/2023.08.01.551279v1

Keywords: pattern formation; cytoskeleton