First Person is a series of interviews with the first authors of a selection of papers published in Journal of Cell Science, helping researchers promote themselves alongside their papers. Udo Onwubiko is first author on ‘ Cdc42 prevents precocious Rho1 activation during cytokinesis in a Pak1-dependent manner’, published in JCS. Udo conducted the research described in this article while a graduate student in Dr Maitreyi Das's lab at the University of Tennessee, USA. She is now a postdoc in the lab of Dr Amy Maddox at University of North Carolina, Chapel Hill, investigating how cells organize spatially and temporally to give rise to higher functional structures, such as organs and tissues.

Udo Onwubiko

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

Our paper describes a phenomenon that highlights a way in which cells coordinate time-dependent processes, in this case, events leading to cytokinesis. We report that this time-dependent coordination requires dynamic crosstalk between two conserved Rho GTPases – Rho1 and Cdc42. We show that Cdc42 blocks untimely Rho1 activation during cytokinesis, thereby preserving the integrity of cytokinesis by ensuring septum formation and ring constriction begin at the right time in the cell cycle.

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

Yes, there were a few challenges. Most of this work was done as we struggled through the COVID-19 pandemic, which brought with it many challenges, including adjusting work schedules, canceling and re-planning experiments, etc. A major discovery in our work was uncovering that Cdc42 prevented premature Rho1 activation at the division site via its effector  Pak1 kinase. Given that Pak1 is an essential gene, we had to use temperature-sensitive mutants, and controlled promoters to discern its role in Rho1 function during cytokinesis. This was challenging because we had to be sure that our observations were accurate. I had to coordinate blind tests with undergraduate students, and other members of the team. Additionally, since we were controlling Pak1 function, and deletions of this protein are lethal, our experiments were long, and accurate results required time-dependent and well-organized experiments, with the proper controls. These were achieved by teamwork, a dedication to succeed and good planning.

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

Yes! One day I came into the lab and found some yeast cells growing on a plate supplemented with components that should inhibit their growth. In yeast genetics, one can control the expression of certain genes via compounds, such as thiamine. While investigating Rho1 function, we used thiamine to inhibit the expression of an essential Rho1 activator, which results in cell death. Interestingly, these mutant cells grew in the presence of thiamine when Cdc42 was inactive, suggesting that lack of active Cdc42 overcame the effect of reduced Rho1 activity. This eureka moment helped cement our findings that Cdc42 prevented Rho1 activation spatially and temporally.

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

My first paper was published with JCS, and their review process is very straightforward and concise. I also enjoy the content of the work they publish and feel that this work will be a great addition.

A yeast cell in late anaphase (white box), as visualized by the actomyosin ring (Rlc1–tdTomato) and spindle pole bodies (Sad1–mCherry), showing activate Rho1 (RBD-mNG) at the division site, where the septum formation has initiated (Calcofluor). Active Rho1 is not present at the division site of the adjacent cell in early mitosis (left).

A yeast cell in late anaphase (white box), as visualized by the actomyosin ring (Rlc1–tdTomato) and spindle pole bodies (Sad1–mCherry), showing activate Rho1 (RBD-mNG) at the division site, where the septum formation has initiated (Calcofluor). Active Rho1 is not present at the division site of the adjacent cell in early mitosis (left).

Have you had any significant mentors who have helped you beyond supervision in the lab? How was their guidance special?

Yes, it is always important to have someone actively listen to your thoughts about things, and give you guidance and good feedback. I had my committee members who were very helpful individually on my journey with this paper. They gave me feedback and guidance beyond lab work.

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 was motivated to pursue a career in science because growing up, both of my parents loved using scientific methods with almost everything. I had moments when I wondered if I was just in science because of the influence of my parents. However, my most empowering period unfolded in graduate school when I came to terms with the fact that I love challenging myself with questions that can inform us about life in its true form. My goal is to continue to excel, knowing that I can be a source of hope for ‘others’ who look like me, or are from similar backgrounds or places as I am. I want these ‘others’ to know that they can always achieve their goals, I want my success to encourage them, and I also want to be able to give helpful answers.

Who are your role models in science? Why?

My dad is my biggest role model. All my life he often sang and talked about his science. So indeed, the sound of ‘science’ should sound like a broken record to me, but he must have done a great job because I have grown into enjoying the art of properly investigating a scientific problem, and not being afraid to fail in the process.

What's next for you?

I am currently working as a postdoc at the University of North Carolina (UNC), where I hope to figure out physio-molecular connections between apoptosis and contractility in germ cell development.

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

Earlier this year, I recently started a little non-governmental organization (NGO) that funds medical expenses for families in Western Africa who cannot afford medical bills and school fees/supplies in need. My goal is to create a source of hope and aid for those who are in dire need of educational and medical assistance.

Udo Onwubiko’s contact details: University of North Carolina, Chapel Hill, USA.

E-mail: udon@unc.edu

Onwubiko
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U. N.
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Kalathil
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D.
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Koory
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E.
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Pokharel
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S.
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Roberts
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H.
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Mitoubsi
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A.
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Das
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M.
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2023
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Cdc42 prevents precocious Rho1 activation during cytokinesis in a Pak1-dependent manner
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J. Cell Sci.
136
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jcs261160
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