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© Springer Verlag

A comprehensive account was published of the current understanding of myosins, actin-based molecular motors, that contains a chapter on the current knowledge of class IX myosins that was contributed by the Bähler group. Class IX myosins demonstrate not only unique motor properties, but simultaneously serve as negative regulators of an important signaling pathway that controls various cellular processes such as e.g. cell morphology and cell migration.

© FB13

The video shows mesenchymal stem cells (OP9) during differentiation into adipocytes (fat cells) over the course of almost 48 hours.
It was recorded with a novel holotomographic microscope, the Nanolive 3D Cell Explorer, which allows label-free nanoscopy based on the refractive index of different cell components.
The technique clearly resolves nuclei, mitochondria, as well as lipid droplets. Furthermore, a mitosis as well as an apoptosis event are shown.
Courtesy of the groups Busch and Grasshoff.

Publication Group Grashoff
Lengthwise cut through the thorax of a fruit fly having an inserted force sensor in the talin protein. The force sensor on the muscle-tendon connections is green and the flight muscles are magenta.
© S. Lemke et al.

How do muscle and tendon connections last a lifetime?

Cell biologists show in fruit flies how a protein controls mechanical stress on muscle-tendon attachments.
Muscles are connected to tendons to power animal movements such as running, swimming or flying. Forces are produced by myofibrils, contractile chains of actin and myosin, which are pulling on muscle-tendon connections called attachments. During animal development, these muscle-tendon attachments must be established such that they resist high mechanical forces for the entire life of the animal. How the individual protein molecules that build the attachments ‘feel’ the mechanical forces inside an intact muscle can now be measured with modern cell and developmental biology techniques. An interdisciplinary team lead by Frank Schnorrer and Carsten Grashoff at the Developmental Biology Institute of CNRS & Aix Marseille University, the Max Planck Institute of Biochemistry in Munich and the Institute for Molecular Cell Biology at University of Münster has now been able to quantify the mechanical forces transmitted by a key attachment protein called Talin during the development of muscle attachments. Sandra Lemke, a PhD student in the Schnorrer group, used the flight muscles of the fruit fly Drosophila for these molecular force measurements and found that a surprisingly small proportion of Talin molecules experiences detectable forces at developing muscle-tendon attachments. She found that muscles deal with the increasing tissue forces by recruiting an high number of Talin molecules to attachments. This way, many Talin molecules can dynamically share the high peak forces produced during muscle contractions, for example while flying. This mechanical adaptation concept ensures that muscle-tendon connections can last for life. These new results have just been published in PLoS Biology. more

AG Hanley: Discovery of a new heart muscle component
Transmission electron micrograph of heart muscle. The repeating striped elements represent sarcomeres, and the dark structures represent mitochondria.
© Andreas Unger

Researchers at Münster University have identified a motor protein that is important for the contractile units of heart muscle.

 In order for the heart to work properly, it must exert muscular force. This involves the coordinated contraction of numerous sarcomeres, the smallest contractile units of heart muscle. Muscle contraction is brought about by the activity of conventional motor proteins, which pull on thin filaments to shorten sarcomeres. Together with researchers from Toronto (Canada) and Leiden (the Netherlands), scientists from the University of Münster have now found out more about the function of a specific unconventional motor protein, myosin 18A (Myo18A): they have discovered a new variant of the protein that appears to be responsible for the assembly and mechanical stability of sarcomeres in the heart. The results could help scientists better understand how sarcomeres are formed and regulated. The study has been published in “The Journal of Biological Chemistry”, where it was selected as an “Editors’ Pick” and identified as a research highlight. more