First Person is a series of interviews with the first authors of a selection of papers published in Journal of Cell Science, helping early-career researchers promote themselves alongside their papers. Safia Omer is first author on ‘Overexpression of Mdm36 reveals Num1 foci that mediate dynein-dependent microtubule sliding in budding yeast’, published in JCS. Safia is a post-doctoral associate in the lab of Wei-Lih Lee at Dartmouth College, Department of Biological Sciences, Hanover, NH, USA, investigating the interplay between cytoskeleton and organelles using quantitative imaging.

Safia Omer

How would you explain the main findings of your paper in lay terms?

Cells use dynein to organize their internal space so that they can grow and divide properly. In baker's yeast cells, dynein travels to the cell periphery, where a protein called Num1 helps it attach to the cell membrane and pull on the nucleus via connecting filaments known as microtubules. This process is important during cell division, as it ensures that the nucleus is placed precisely at the midpoint of the dividing cell, so that the genetic material segregates equally into the progeny. Researchers have long proposed that multiple dynein molecules work as a team to amplify its pulling force at the outskirts of the cell; however, where and how the dynein team is assembled is not clear. A prevailing hypothesis postulates that the size of the Num1 cluster dictates the size of the dynein team. A larger Num1 cluster would assemble a larger dynein team, producing a stronger pulling force. Nevertheless, the results in our paper demonstrate, for the first time, that dynein is specifically attached by small Num1 clusters (composed of about six Num1 molecules). We found no correlation between the size of Num1 clusters and the efficiency of dynein-based pulling activity. Rather, we show that enhancing Num1 clusters is necessary for a different, separate function of Num1 – anchorage of the mitochondrial network to the cell periphery.

Were there any specific challenges associated with this project? If so, how did you overcome them?

We did not face any specific technical challenges but rather some conceptual ones, especially as our results began to contrast with some of the prevailing notions for the role of dynein-anchoring proteins. With rigorous experimental design and analysis, we were able to confirm the findings in the paper and strengthen our working model.

When doing the research, did you have a particular result or ‘eureka’ moment that has stuck with you?

There were several ‘eureka’ moments during this project, but the most critical one is when we first discovered the striking phenotype of Num1 localization in the Mdm36-overexpressing cells, which were initially observed by John Beckford, a co-author on the paper. Another memorable moment was when we were able to directly observe astral microtubule plus-ends sliding on individual cortical Num1 clusters, which enabled us to precisely characterize the sites where dynein mediates spindle pulling.

Why did you choose Journal of Cell Science for your paper?

JCS is a well-known journal that publishes excellent cell biology papers of high quality. Additionally, JCS offers to publish the peer review history alongside the manuscript, which is a nice avenue for authors to provide additional rebuttal explanations if their data conflicts with the prevailing notions in the field.

What motivated you to pursue a career in science, and what have been the most interesting moments on the path that led you to where you are now?

I knew that I wanted to be in science since my first molecular biology class in college. I was (and still am) fascinated by the exquisite molecular details of how cells are built to form a living reproducing unit. My most interesting moments were generated by the great mentors that I have encountered since the early start of my research path. I have been shaped by their curiosity and enthusiasm for cell biology.

Who are your role models in science? Why?

I did my undergraduate and Master's research project in Sudan, a developing African country with very limited resources devoted to research. My role models are the resilient scientists who, in spite of the bleak research environment, endure with patience, creativity and resourcefulness as they continue to mentor students and do research.

What's next for you?

I will be pursuing another postdoctoral fellowship in Prof. Rene Harrison’s Lab at the University of Toronto, investigating aspects of cytoskeletal organization in macrophages.

Striking enhancement of Num1 clusters upon overexpression of its assembly factor Mdm36.

Striking enhancement of Num1 clusters upon overexpression of its assembly factor Mdm36.

Tell us something interesting about yourself that wouldn't be on your CV

When I am not working in the lab, I enjoy watching art-house films.

Safia Omer's contact details: Dartmouth College, Department of Biological Sciences, 78 College Street, Hanover, NH 03755, USA.

E-mail: safia.omer@dartmouth.edu


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Overexpression of Mdm36 reveals Num1 foci that mediate dynein-dependent microtubule sliding in budding yeast
J. Cell Sci
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