by PhilipJ on 29 October 2006
So I’m late as usual, but here at last is a recap of the local retreat we held for biophysics and biomathematics research in Vancouver. I should preface this by saying it was organised entirely by graduate students, and that things went beyond smoothly, so many kudos to them. I think our two keynote speakers were also highly impressed, which is always a good thing.
Speaking of our keynote speakers, Joe Howard from the Max Planck Institute of Molecular Cell Biology and Genetics in Dresden, Germany started the conference with his talk. He began by talking about the current knowledge of different molecular motors, such as myosin and kinesin, and then focused in on a member of the kinesin family which isn’t a processive stepper which carries cargo (a translocase), but depolymerizes microtubules instead of simply walking on them (a depolymerase), called MCAK. The motion of this enzyme was also quite different from most kinesins. “Typical” kinesin binds to a microtubule and walks, unidirectionally, for a few hundred steps and then unbinds, and does so anywhere along the track (e.g., it doesn’t need to start at the beginning of the microtubule), and each step is thought to hydrolize an ATP molecule. MCAK, however, binds the microtubule at random, and then rapidly diffuses back and forth for about one second before letting go or finding it’s binding site at the end of the microtubule, before commencing depolymerization! To see more details about this work, see their paper in Nature, subscription required. This was then compared to how it is believed that transcription factors can find their very specific binding sites on DNA, by attaching somewhere and carrying out a faster-than-processive-motion random walk, looking for their specific sequences.
Joe also talked at length about new work on the dynamics of the mitotic spindle observed during asymmetric cell division. To create daughter cells which are not twins (that is, two different cells that will “grow up” to carry out different functions), some kind of asymmetry in the cell division process must be present. In some cases (I can’t recall what kind of cells they were), it is a physical size difference between the two daughter cells. The chromosomal DNA being taken from the centre of the mother cell to the new centres of each daughter cell travels a different distance, and, as it turns out, has a rocking motion as it is being pulled. He showed fluorescence microscopy movies of this process, and it was truly amazing to watch. In colaboration with theorists at another MPI, a model of load-depending molecular motors was created, and described the observed dynamics quite well. He also described sperm swimming dynamics, and particularly how dyneins seem to control the beating of the cilia of a sperm cell.
The take home message of Joe’s talk was that in many of these processes (the mitotic spindle dynamics, sperm cell swimming, etc), a chemical-based signalling system would be too slow to describe the dynamics observed, and that force, via load-dependent activity of molecular motors acting as a feedback mechanism, is a previously unthought of method for information to travel about the cell.
Our other keynote speaking was Kazuhiko Kinosita from Waseda University in Tokyo, Japan. AndrÃ© saw him give a similar talk at the Biophysical Society earlier this year, so for the details, head back to AndrÃ©‘s post. He also showed us some new work they’re doing, but I shouldn’t talk about that until a publication comes out!
We also had graduate student (and post-doc) talks, which were largely enjoyable, but so short — 10 minutes — that it was hard a lot out of them, and a poster session that went quite well.
The retreat ended with a forum on the issues surrounding collaborations between physicists and biologists, and this section was unfortunately much too short. This led to a bunch of discussions between us grad students in my own lab, so I’ll talk more about those ideas in another post.
Minor update—There are some photos of the event at the Frontier’s website, here.