Informing the Interplay Between Nuclear Function and Structure Drives the Career of the STEM CELLS 2016 Young Investigator Award Winner
Gunes Uzer, PhD, assistant professor in the Department of Mechanical and Biomedical Engineering at Boise State University (Boise, Idaho), is the 2016 recipient of STEM CELLS’ Young Investigator Award (YIA). This $10,000 prize is awarded annually to a young scientist whose paper is judged to be of worldwide significance by the Editors of the Journal.
Dr. Uzer’s award-winning study, “Cell Mechanosensitivity to Extremely Low-Magnitude Signals Is Enabled by a LINCed Nucleus,” focuses on the role of the nuclear envelope and the nucleoskeleton as a dynamic, mechano-responsive signaling platform that regulates the biochemical and physical coupling of cells to the outside world. In particular, it shows how the LINC complex of the nuclear envelope is a mechano-sensitive regulatory organelle in stem cell biology.
“Our finding has significant biomedical implications for approaches to cancer, injury, aging, and diseases associated with poor nucleo-cytoskeletal coupling,” he said. “The findings from this paper have also laid the foundation for a prestigious NASA fellowship, opening new research avenues to study how mechanical adaptation of LINC complexes regulate stem cell fate under microgravity.”
Dr. Uzer joined Boise State in August 2016 as the director of its Mechanical Adaptations Laboratory, where he now leads a multidisciplinary research program. In the past 10 years, his studies have covered a broad range of topics, including advanced material characterization, experimental photometry, finite element modeling, as well as cell and animal models. His work on stem cell mechanobiology is focused on identifying relevant components of mechanical signals that modulate a wide variety of musculoskeletal cell functions as well as defining the mechanical control of stem cell structure, function, and fate.
Dr. Uzer was awarded his bachelor’s degree in physics (Turkey), then received his master’s in mechanical engineering and a doctorate in biomedical engineering, both from Stony Brook University, New York (United States). He did his postdoctoral work at the University of North Carolina, Chapel Hill, working with Janet Rubin, MD, in the Department of Medicine, Division of Endocrinology.
Dr. Uzer has earned several professional awards in addition to STEM CELLS’s YIA, including, among others, the Harold Frost Young Investigator Award, given by the American Society of Bone and Mineral Research, as well as that organization’s Young Investigator Travel Award, both in 2015, and the NASA New York City Research Initiative (NYCRI) Achievement Award in 2009.
He answers several questions posed by STEM CELLS about his paper, his other work in the stem cells field, and more here:
STEM CELLS: What hypothesis were you testing in the research described in your award-winning paper?
Uzer: Our bodies sense and respond to mechanical challenges from the organismal down to the cellular level. In this way, when applied at high frequency (30–100Hz), low intensity mechanical vibrations (0.1–1g, where 1g is the earth’s gravitational pull) have been shown to increase bone mass and reduce fat mass by promoting osteoblast differentiation and inhibiting adipocyte recruitment in mesenchymal stem cells (MSCs).
It was not clear, however, how these extremely small mechanical signals were sensed at the cellular level.
Our earlier findings have shown that cellular response to these high frequency accelerations correlate with rate of acceleration, rather than secondary signals like fluid shear stress or substrate deformation, rejecting the possibility of a typical outside-inside signaling. In this study, we considered the possibility of dynamic accelerations generating intracellular forces via nuclear motion and hypothesized that the cell response to vibrations was supported by the LINC (Linker of Nucleoskeleton and Cytoskeleton) complex that provides mechanical coupling between the nucleus and the actin cytoskeleton.
STEM CELLS: Can you explain why investigating this hypothesis is important to stem cell research?
Uzer: Form derived from a cell’s mechanical environment drives its function and fate. In the past decade, we have seen a considerable advance in understanding how cytoskeletal structures and focal adhesions work as mechano-sensors in cells. In contrast, we are just learning how the nucleus, the biggest organelle in the cell, may actively participate in cellular mechano-sensitivity.
In this way, identification of fundamental mechanisms regulating this mechano-sensory function would be critical in designing better treatment strategies in regenerative medicine.
STEM CELLS: Briefly outline the approach you used to test your hypothesis.
Uzer: We have directly tested the role of LINC complex in the activation of mechano-sensitive pathways in response to low magnitude vibrations. To avoid any confounding factors, we have selected focal adhesion kinase (FAK) activation as the outcome variable. As focal adhesion activation takes place at the cell-substrate interface, away from the cell nucleus, this provided us a metric we could reliably measure.
To test whether LINC-mediated nucleo-cytoskeletal connectivity was required, we disrupted the LINC anchor Sun proteins—inhibiting the connectivity between nucleus and cytoskeleton. This way, if low intensity vibrations were able to generate inside-inside force on the cytoskeleton by virtue of nucleo-cytoskeletal connections, this would have inhibited it. We indeed found this to be the case.
Importantly, as a control we used substrate strain, a well-known mechanical regimen that directly activates integrin mediated outside-inside signaling. In this case, we have shown that disruption of LINC mediated connectivity had no effect.
STEM CELLS: What was/were the most important finding(s) to come out of your study?
Uzer: The most important concept that came out of this study was that cells—in this case, MSCs—utilize a multitude of mechanisms to sense various external stimuli and that the LINC mediated physical connections between a nucleus and the cytoskeleton at the nuclear envelope, and the cellular structure as an extension of that, can act directly as a mechano-sensory element.
Critically, when mechanical challenges were applied in succession, it amplified cellular response. This suggests that the forces imposed on the cytoskeleton not only activate signaling events but that cellular structure adopts configurations more permissive to activation of mechano-signaling pathways. In this way, form not only follows function but also informs it.
STEM CELLS: Was there a specific methodological technique important to these studies?
Uzer: Techniques we use in the laboratory usually involve widely accepted imaging and protein analysis methods. Our group specializes in applying a variety of mechanical challenges to cells. These include custom-made systems for applying dynamic high frequency (30–200Hz) low magnitude (0.1–1g) vibrations or low frequency (0.1–2Hz) high magnitude substrate strain (1–20%).
STEM CELLS: What does this mean for stem cell biology and its application?
Uzer: The function and fate of stem cells are untimely driven by the environmental cues, whether mechanical or chemical. There is an increasing awareness in the scientific community that the nucleus actively participates in the mechano-transduction process rather than being a passive node for incoming mechanical signals. Our study demonstrates the mechano-sensory capabilities of LINC complexes at the nuclear surface. A basic understanding of how LINC complexes and the nuclear envelope in general are regulated would be invaluable in discovering how the cellular environment drives stem cell function.
STEM CELLS: What's the best scenario that you would like to see come out of your study?
Uzer: I think we already have the best outcome. Our study led to a very exciting set of studies to elucidate the structural components of the nucleus as a mechano-sensitive and mechano-responsive signaling platform.
STEM CELLS: Let’s turn the spotlight on you for a bit. Why did you choose to go into stem cell research?
Uzer: As an aspiring scientist in musculoskeletal biology, studying why mechanical signals (or lack of them) regulate bone and fat mass, it became very clear that instead of studying bone and fat cells separately, focusing on the common progenitor, mesenchymal stem cells, was the right choice.
STEM CELLS: Can you talk about your training, any mentors who might have influenced you and what motivates you today?
Uzer: In addition to being a mechanical engineer trained in experimental mechanics, my PhD training falls into the realm of exercise and bone physiology. I was always lucky to work with exceptional scientists who encouraged me to ask new questions and broaden my horizons. My PhD mentor, Stefan Judex, who persuaded me to go into academia, and Clinton Rubin at Stony Brook University – both of whom I still actively collaborate with today – provided me the lens to look into biology through mechanics. Exceptional support from my postdoctoral advisor, Janet Rubin at the University of North Carolina, was instrumental for me to carve the scientific niche I inhabit today.
Throughout all my career, unrelenting support from my wife, both professional and personal, has been the driving force for me. Scientifically, the idea that we can discover the underlying mechanisms of how biological systems work has been a big motivation for me. In no other profession would I have had a chance to ask fundamental questions to understand how mechanical qualities drive stem cell fate. For that I am grateful.
STEM CELLS: Tell us a bit about your current position.
Uzer: I am currently Assistant Professor in Mechanical and Biomedical Engineering at Boise State University. I have a small but dedicated group of like-minded scientists that work with me. Together we are working to develop new optical and biochemical methods that would allow us to better understand how cell structure interacts with signaling mechanisms to control stem cell fate.
This is really a very exciting time for me as both my department and the Biomolecular Research Center led by Dr. Julia Oxford provided me exceptional funding and facilities to establish my own research program as part of the NIH COBRE (Centers of Biomedical Research Excellence) program. The collaborative research environment at Boise State University has been exceptional. Many research teams have opened their resources to me and my group as we work toward establishing our capabilities. I am looking forward to strengthening these collaborations to broaden the collective impact of our work.
STEM CELLS: Is there anything else that you think is important to bring up about your paper, your work and what you think should happen next?
Uzer: Absolutely. Studies stemming from our work not only led me to get a prestigious fellowship from the NASA-funded National Space Biomedical Institute, but now we are understanding that the LINC complexes not only provide connectivity but also direct the signaling in stem cells to control fate selection. We intend to deepen our understanding on how mechanical signals inform the interplay between nuclear function and structure.
STEM CELLS: Why did you select the journal STEM CELLS to publish your paper?
Uzer: STEM CELLS is a well-respected and a long-standing journal in this field. In this way, we were very happy that we were able to publish our findings in there.
STEM CELLS: How do you think the Young Investigator Award might affect your career?
Uzer: As a junior faculty who is trying to establish a research program, being recognized by one of the leading journals in the field is both gratifying and reassuring that the research direction we are taking is making an impact.