Student Thesis Peppered with Insights into ALS

Tuesday, May 10, 2016
Laura MacNair headshot
LMP doctoral student Laura MacNair

"Looking down the microscope, some people see things and some don't."

So says Janice Robertson, a professor in the Department of Laboratory Medicine and Pathobiology at the University of Toronto.

Robertson should know. She has made some big discoveries about amyotrophic lateral sclerosis (ALS), a neuromuscular disease that kills most people it strikes within five years of diagnosis.

And she has supervised students who have done the same — including Laura MacNair, who is writing her doctoral thesis this spring and will graduate in the fall.

MacNair played a key role on two papers from Robertson's lab in the last year that have helped shift the focus of research on ALS (and frontotemporal dementia, which has a similar molecular genetic pathology).

Robertson credits much of MacNair's success to a methodical and thorough approach in the lab. "She just gets on with it," says Robertson, who is also a scientist at the Tanz Centre for Research in Neurodegenerative Diseases. "She's become the go-to person in the lab, like a kind of oracle. I'll be very sad to see her go."

Scientists have known since 2011 that mutations in the C9orf72 gene are the most common cause of ALS and FTD, but they had no way to see how those changes affect cell function as the diseases take hold.

Robertson and her team developed antibodies that let them track the location and function of C9-short and C9-long, the two protein isoforms of the C9orf72 gene.

MacNair made the surprising discovery that C9-short is lost from the nucleus of diseased motor neurons in patients with ALS. "It was a pivotal observation, and it has helped shine a light on the relevance of C9orf72 in disease," says Robertson.

The Annals of Neurology published the findings, in a paper that was one of its top 20 downloads in 2015.

Robertson and other ALS researchers suspect that C9-short disrupts the nuclear shuttling complex — a process critical for healthy cell function which lets other proteins move back and forth across the nuclear membrane.

Several other labs are now studying the role of C9-short in ALS and FTD.

MacNair and her colleagues also found that loss of C9-short correlates with the similar mislocalization from the nucleus of TDP-43, a protein that clinicians use to diagnose most cases of ALS.

The group validated their findings with human samples from the ALS Clinic at Sunnybrook Health Sciences Centre, where they work with Professor Lorne Zinman, a staff neurologist and the clinic's director.

That collaboration was a big draw for MacNair when she chose to study with Robertson in 2010.

"One thing that drew me here was access to a post-mortem database of ALS samples," says MacNair. "It was a bit personal because my grandfather had passed away with Parkinson's disease, and he donated his body to science. I wanted to look at neurodegenerative diseases in animal models but also in humans."

MacNair has attended autopsies to collect patient tissue and visited the clinic to observe diagnostic procedures, and she says both were great learning experiences.

She also credits Shangxi Xiao, a researcher who has been with Robertson since she set up her lab in Toronto, with sharing some useful advice. "One thing I learned from Shangxi is that if you do your experiments slowly and carefully, but right the first time, it ends up being more productive in the long run," she says. "The point is to focus on what's important and avoid the distraction of trying to seem busy."

That approach served MacNair well for other recent work on the TDP-43 protein. She and her colleagues found that the disappearance of TDP-43 from the nucleus of diseased motor neurons in mice leads to misregulation of two RNA-binding proteins — DDX58 and MTHFSD — which could contribute to cell degeneration in ALS.

The group was the first to combine a technique called Translating Ribosome Affinity Purification with microarray analysis, which allowed them to see changes in mRNAs (messenger RNAs) as they are translated into proteins in mice with ALS, at exact stages of disease and in specific neurons. (Cells use mRNAs as templates when they create proteins from DNA.)

"Neither gene had come up in previous high-throughput studies," says MacNair. "But the mRNAs of both genes bind to TDP-43 directly, which is significant because TDP-43 is the major pathology in ALS."

The journal Brain published the results in January this year and featured them with an editor's choice profile on the web.

These days, MacNair spends extra-long hours in the lab and writes her PhD thesis at home. In her free time, she plays with her basset hound, Bowie, or goes to the gym to rock climb — another activity that requires deliberate and careful strategy.

MacNair is unsure about her next career move, but it could be a postdoctoral fellowship in another city or a role in brain health outside academia. She is still plotting her options.

Two things seem certain about MacNair's future — it will involve science and, for Robertson, some mixed feelings.

"One of the joys of supervising graduate students is seeing them come in and develop into confident researchers who take satisfaction in their experiments," says Robertson. "It will be hard to watch her go, I'll be very happy to see her succeed as she moves on with her career." — Jim Oldfield