HSPRF Research Report 27 August 2012
Prof. Alan Mackay-Sim
Olfactory stem cells from HSPers continue to give us new insights into how the spastin genetic mutation might lead to the disease. In the last few months we have been working on how the disruption to the microtubule network within HSP stem cells could affect cell functions. Microtubules are part of the cell “road network” to move cell organelles around to where they are needed. From what we know about the function of spastin, it makes sense that cells from HSP patients with spastin mutations have disruptions to their microtubules. There are many cell organelles (“transport trucks”) specialised encapsulated structures that carry out the work of the cell and are vital to its functions and survival. Organelles move around inside the cell within the microtubule network.
We have shown that certain organelles, namely mitochondria and peroxisomes, have altered distribution inside HSP stem cells. Our work gives us new insights into HSP because we have shown that cells from HSPers have significant anomalies in many aspects of their biology but can, at the same time, function normally in many respects. This helps explain why people with spastin mutations may not develop HSP symptoms until well into adulthood. They key question now is, what is the difference between stem cells and corticospinal motor neurons that allow the stem cells to cope but the motor neurons to fail? We have submitted this work for publication in an international scientific journal.
Current work in the lab
Dr. Yongjun Fan, Ph.D.
In previous work, we introduced a few microtubule-binding drugs to treat the cells and found that HSP cells responded differently compared to the healthy control cells. At very low concentrations, the drugs can rescue the stable microtubules to control levels, suggesting a potential avenue for HSP treatment. I am now finding out how these drugs affect mitochondria and peroxisomes as well as other cell organelles, including lysosomes and endoplasmic reticulum. Lysosomes and endoplasmic reticulum, like peroxisomes and mitochondria, are changed in HSP cortical spinal axons.
Now we are trying to decipher the cellular mechanisms using HSP cells.
Some of the changes we are seeing in HSP stem cells are similar to cellular pathologies in other motor neuron diseases. This means that the many mutations in HSP and various other motor neuron diseases may act through the same common cellular pathways. We have some ideas now as to the identity of one of the common pathways.
Gautam Wali, Ph.D. candidate
I am working on how the changes in the microtubules affect the movement of cell organelles in HSP stem cells. Presently, I am working on tracking and analyzing the movement of peroxisomes in living HSP stem cells. To do this I use genetic engineering to make the peroxisomes inside cells glow fluorescent green and video the peroxisomes with time-lapse imaging down a microscope. The videos are then analyzed with a specialized computer program with which I can follow simultaneously the movement of 150 peroxisomes. Do this for 10 cells from each of 10 HSP samples and 10 controls and it generates masses of data! I am also working on inducing HSP stem cells to differentiate the stem cells into neuronal cells with long projections, like axons. The plan is to use these cells to test for potential changes to organelle transport and distribution. I plan to work on defining the trafficking defects of the mitochondria and try to rectify them by screening microtubule-binding drugs.
Simon Weyers, Ph.D. candidate
I am working on getting an inside view into the dynamics of microtubule formation in cells from HSPers with and without mutations in the spastin gene. We think that spastin is altering the speed with which microtubules form and this might then affect organelle distribution. To see microtubules forming inside the cell, I am genetically engineering cells to make the microtubules glow green as they are being made inside the cell. The DNA construct for genetic engineering was kindly given to us by Prof Niels Galjart from the Department of Cell Biology and Genetics in Rotterdam, Netherlands. I have now established this method in our laboratory. The plan is to use time-lapse video imaging to quantify the speeds of microtubule formation in HSP and healthy control stem cells to see if we can find disease specific differences in microtubule dynamics. I will then look at microtubule dynamics after the cells are treated with microtubule-binding drugs.