PhD position available in a collaborative project between the Rico and Schnorrer laboratories at the Turing Centre for Living Systems in the Luminy Campus, Marseille
The muscle spring: quantifying and manipulating the molecular elasticity of muscle in vitro and in vivo
Muscles produce mechanical forces that power animal movements. Different muscle types have vastly different functions, which is manifested in their mechanical properties: mammalian heart is very stiff, skeletal muscle is soft. The major molecular cause suggested to be responsible for this difference are different versions of the giant muscle spring protein called titin. Titin is the largest protein in our body, mechanically linking myosin motor filaments with actin filaments in the muscle sarcomere, which changes in length during the contraction cycle. Molecularly, the titin spring is elongated during muscle relaxation and shortened during muscle contraction and thus contributes significantly to the passive forces in muscle. This Centuri PhD project aims to manipulate the molecular elasticity of muscle using the genetic model Drosophila and quantify its impact on the mechanical and the contractile properties of the manipulated muscle in vivo and in vitro.
muscle, mechanical spring, titin, atomic force microscopy, CRISPR, Drosophila, genetics, forcesensors
Aim1. Using force microscopy to characterise the mechanical properties of different Drosophila
muscles from wild type and titin spring mutants recently generated in the Schnorrer lab.
Aim2. Generation of additional titin spring designer alleles using CRIPR-based fly genetics.
Aim3. Establishment of ex vivo sarcomere force-length measurements of isolated Drosophila muscle fibers
from wild type and titin spring mutants.
Proposed approach (experimental / theoretical / computational)
The proposed project uses Drosophila as an in vivo experimental system to generate different muscle
types and probe their mechanical properties. It will largely focus on two muscle types, larval body muscles with long sarcomeres, which are soft, versus adult flight muscles with short sarcomeres, which are stiff. The project will use established atomic force microscopy to quantify the elasticity and mechanical properties of wild type and titin spring mutant larval and flight muscles using semidissected alive preparations (Aim1). The project will compare wild type muscles to titin spring mutants already generated in the lab and apply established CRISPR-based genome manipulation technologies to generate novel designer titin mutants (Aim2). Furthermore, developing a lever-based rheometer (or force sensor, see Kalenkar, Khalilgharibi or Sagvolden), the project aims to establish an ex vivo system that can quantify sarcomere force-length relationships in isolated larval muscles from wild type and titin spring mutants (Aim3).
This interdisciplinary project bridges from developmental biology of muscle morphogenesis to the biophysics of biological machines, the sarcomeres. It combines the in vivo manipulation of gigantic proteins (titins) using Drosophila genetics (CRISPR) with the quantification of mechanical properties of different wild type and mutant muscle types using atomic force microscopy. It will further develop a force sensing device for measuring active muscle contraction forces from wild type and mutant muscles isolated from Drosophila. This may involve support from the CenTuri engineering platform ‘Mechantronics’ to build such a device.
This is an interdisciplinary PhD project. The selected candidate should enjoy working in two interactive teams, one with a biological focus and strong interest in mechanical forces (Schnorrer) and one with a physics focus and strong interest in biological systems (Rico). Hence, the student can either be an experimental physicist with interest in biological systems or a biologist with strong interest in quantitative biology and principles of mechanobiology. Experimental experience with Drosophila or genetics is not essential, however, basic principles of cell biology, optics or mechanics are of advantage.
Is this project the continuation of an existing project or an entirely new one? In the case of an existing project, please explain the links between the two projects
This is a new project that was not yet funded by Centuri. However, the first titin-spring Drosophila mutants and titin molecular force sensors have been generated during the PhD project of Vincent Loreau, who was funded by the LabEx INFORM.
2 to 5 references related to the project
Hamdani et al. Biophysical Review 2017; doi:10.1007/s12551-017-0263-9
Zhang & Schnorrer G3 2014; doi: 10.1534/g3.114.013979
V. SRR, Kalelkar C, Pullarkat PA 2013. doi:10.1063/1.4824198
Khalilgharibi N, Fouchard J, et al. 2019 doi:10.1038/s41567-019-0516-6
Sagvolden G, Giaever I, Pettersen EO, Feder J. 1999 doi:10.1073/pnas.96.2.471
3 main publications from each PI over the last 5 years
- Lemke SB, Weidemann T, Cost AL, Grashoff C, and Schnorrer F. (2019). A small proportion of Talin molecules transmit forces at developing muscle attachments in vivo. PLoS Biology. 17(3):e3000057. doi: 10.1371/journal.pbio.3000057
- Spletter ML, Barz C, Yeroslaviz A, Zhang X, Lemke SB, Bonnard A, Brunner E, Cardone G, Basler K, Habermann BH, and Schnorrer F. (2018). A transcriptomics resource reveals a transcriptional transition during ordered sarcomere morphogenesis in flight muscle. eLife. 7, e34058. doi: 10.7554/eLife.34058
- Loison O, Weitkunat M, Kaya-Çopur A, Nascimento Alves C, Matzat T, Spletter ML, Luschnig S, Brasselet S,
Lenne PF, and Schnorrer F. (2018). Polarization resolved microscopy reveals a muscle myosin motor independent mechanism of molecular actin ordering during sarcomere maturation. PLOS Biology, 16, e2004718. doi: 10.1371/journal.pbio.2004718
- Valotteau, C, F. Sumbul, F. Rico*. High-speed force spectroscopy: microsecond force measurements using ultrashort cantilevers. Biophysical reviews, 11, 689–699 2019 doi.org/110.1007/s12551-019-00585-4
- Rico, F*, A Russek, L González, H Grubmüller*, and S Scheuring*. Heterogeneous and Rate-Dependent
Streptavidin–Biotin Unbinding Revealed by High-Speed Force Spectroscopy and Atomistic Simulations. PNAS 116, 14, 6594–6601 2019 https://doi.org/10.1073/pnas.1816909116
- Rigato A, Miyagi A, Scheuring S, Rico F*. High-frequency microrheology reveals cytoskeleton dynamics in living cells. Nat Phys, 13(8): 771-775 2017 hal-01764684v1
– In order to apply please visit the application page at the CENTURI website –