A breakthrough at IRB Barcelona fills a knowledge gap in understanding how the cell division apparatus, the mitotic spindle, is formed.
The in vivo visualization and monitoring of the starting points of microtubules — filaments responsible for organising the mitotic spindle — provides novel insight into the dynamic architecture of this structure.
The findings will also contribute to understanding how the mitotic spindle is perturbed by drugs that target microtubules and that are used in chemotherapy.
The division of a cell in two requires the assembly of the mitotic spindle, an extremely complex structure, which is the result of the coordinated action of a multitude of proteins and a finely tuned balance of their activities. A large part of the time that a cell requires to divide is devoted to assembling the mitotic spindle, which, superficially, resembles a ball of thread with the shape of a rugby ball.
The most abundant components of the spindle are the microtubules. “By labelling the ends of thousands of these fine filaments, which are indispensable and extremely dynamic and variable, we have finally been able to follow their distribution and movement during the assembly of the mitotic spindle,” explains Jens Lüders, a cell biologist from the Institute for Research in Biomedicine (IRB Barcelona). The breakthrough appeared yesterday in the advanced online edition of the journal Nature Cell Biology.
“For more than 10 years we have been able to track only the growing ends of microtubules but not the starting points. As a result, we lacked essential information in order to understand the dynamic architecture of the mitotic spindle and how it contributes to cell division,” says Lüders. Headed by the German scientist who runs the Microtubule Organisation group at IRB Barcelona, the study carries only two names, his own and that of the French researcher Nicolas Lecland, first author, who completed his PhD at IRB Barcelona through a “la Caixa” fellowship.
The scientists have demonstrated that the protein γ-tubulin localizes at the starting points of the microtubule filaments and is relatively stably associated with these structures. Using a version of γ-tubulin that carries a fluorescent label activated by laser light, the researchers were able to follow the movement of the starting points of microtubules within mitotic spindles by filming dividing human cells.
The Advanced Digital Microscopy Facility, a joint IRB Barcelona-Barcelona Science Park Facility run by the IRB physicist Julien Colombelli, has been crucial for setting up the technology required. “The success of this study is also the result of the technical know-how and cutting-edge technology available, without which we would never have been able to tackle this project,” emphasizes Lüders.
The researchers describe for the first time where most microtubules form inside the mitotic spindle, how they develop, and how their starting points are transported—with the help of three motor proteins—to opposite poles of the spindle, where they attach. Simultaneous to this process, the opposite ends of the filaments extend towards the cell centre, where they interact with chromosomes.
When the spindle is finally assembled, the microtubules pull the chromosomes to opposite poles and initiate the physical division of the cell. “We now have a more complete understanding of how the spindle assembles and functions and can use our novel marker for testing old and new hypotheses about underlying mechanisms,” says the scientist.
A new tool to study cancer
In addition, the breakthrough paves the way to “better” understanding the mode of action of drugs that inhibit microtubules and that are used in chemotherapy. These kinds of drugs impede the mitotic spindle, thus preventing cell division and interfering with tumour growth.
In spite of the many years of clinical success of these treatments against cancer, little is known about how they impair spindle architecture and function. Although these drugs are highly efficient, they do not show the specificity desirable as they also affect healthy dividing cells. In addition, they affect non-dividing cells such as neurons, in which microtubules also have important functions.
“A better understanding of the differences in spindle organisation between cancer and healthy cells and how they respond to microtubule-targeted drugs is essential in order to optimise treatments, for example by identifying more specific drugs or new targets. This tool could be useful to achieve these objectives,” states the researcher.
The study has been supported by structural funds from the Generalitat de Catalunya, a Marie Curie grant from the European Union, and the Plan Nacional, of the Ministry of Economy and Competitiveness.
The dynamics of microtubule minus ends in the human mitotic spindle
Nicolas Lecland and Jens Lüders
Nature Cell Biology (2014) Doi: http://dx.doi.org/10.1038/ncb2996
Sònia Armengou | Eurek Alert!
Two Group A Streptococcus genes linked to 'flesh-eating' bacterial infections
25.09.2017 | University of Maryland
Rainbow colors reveal cell history: Uncovering β-cell heterogeneity
22.09.2017 | DFG-Forschungszentrum für Regenerative Therapien TU Dresden
At the productronica trade fair in Munich this November, the Fraunhofer Institute for Laser Technology ILT will be presenting Laser-Based Tape-Automated Bonding, LaserTAB for short. The experts from Aachen will be demonstrating how new battery cells and power electronics can be micro-welded more efficiently and precisely than ever before thanks to new optics and robot support.
Fraunhofer ILT from Aachen relies on a clever combination of robotics and a laser scanner with new optics as well as process monitoring, which it has developed...
Plants and algae use the enzyme Rubisco to fix carbon dioxide, removing it from the atmosphere and converting it into biomass. Algae have figured out a way to increase the efficiency of carbon fixation. They gather most of their Rubisco into a ball-shaped microcompartment called the pyrenoid, which they flood with a high local concentration of carbon dioxide. A team of scientists at Princeton University, the Carnegie Institution for Science, Stanford University and the Max Plank Institute of Biochemistry have unravelled the mysteries of how the pyrenoid is assembled. These insights can help to engineer crops that remove more carbon dioxide from the atmosphere while producing more food.
A warming planet
Our brains house extremely complex neuronal circuits, whose detailed structures are still largely unknown. This is especially true for the so-called cerebral cortex of mammals, where among other things vision, thoughts or spatial orientation are being computed. Here the rules by which nerve cells are connected to each other are only partly understood. A team of scientists around Moritz Helmstaedter at the Frankfiurt Max Planck Institute for Brain Research and Helene Schmidt (Humboldt University in Berlin) have now discovered a surprisingly precise nerve cell connectivity pattern in the part of the cerebral cortex that is responsible for orienting the individual animal or human in space.
The researchers report online in Nature (Schmidt et al., 2017. Axonal synapse sorting in medial entorhinal cortex, DOI: 10.1038/nature24005) that synapses in...
Whispering gallery mode (WGM) resonators are used to make tiny micro-lasers, sensors, switches, routers and other devices. These tiny structures rely on a...
Using ultrafast flashes of laser and x-ray radiation, scientists at the Max Planck Institute of Quantum Optics (Garching, Germany) took snapshots of the briefest electron motion inside a solid material to date. The electron motion lasted only 750 billionths of the billionth of a second before it fainted, setting a new record of human capability to capture ultrafast processes inside solids!
When x-rays shine onto solid materials or large molecules, an electron is pushed away from its original place near the nucleus of the atom, leaving a hole...
19.09.2017 | Event News
12.09.2017 | Event News
06.09.2017 | Event News
25.09.2017 | Power and Electrical Engineering
25.09.2017 | Health and Medicine
25.09.2017 | Physics and Astronomy