In the April 2015 issue of the JCI, Choate et al. define a new subtype of ichthyosis with confetti (IWC), a skin disease in which patients present with red, scaly skin at birth and then develop hundreds of normal skin spots as they age. The identified subtype is caused by a de novo mutation in keratin 1 (KRT1). The mutation results in partial collapse of the cytoplasmic intermediate filament network and mislocalization to the nucleus. Their research implicates KRT1 in the high frequency of revertant mosaicism in IWC. We talked to the lead author, Keith Choate, about this work and his career path as a physician-scientist.
Could you tell us about the research you recently published in JCI and your role in the project?
In the course of studying patients with IWC, we became a major referral center for this disorder, which we recognized was vanishingly rare. We identified one kindred that had a confetti-like phenotype, but looked different from the kindreds that we initially described. These individuals had red skin like other confetti patients did, but they had a much more significant palmoplantar keratoderma. In contrast to patients who have IWC due to KRT10 mutations, these individuals had small white spots that were more focused in flexural areas and which didn't grow as large in size as what we saw in our KRT10 patients. This disorder proved to be interesting to us. We sought to use the same approach that we had used to identify KRT10 mutations. Essentially, we tried to do biopsies of the white spots to grow cells from them, and then to look for loss of heterozygosity. What we discovered is that we were not finding loss-of-heterozygosity events, despite going back and doing more biopsies. Ultimately, we found that there were a few white spot cell lines in which we were identifying small B allele deviations. This led us to go back to the patients and to do new biopsies on the white spots and use laser capture microscopy to specifically isolate pure populations of revertant cells.
What were the biggest challenges that you encountered while pursuing this work?
In this work, we used laser capture microscopy to isolate revertant cells. One of the major hurdles to overcome was developing a new methodology to effectively genotype the laser capture–microdissected tissue. The other challenge was that this work was based on one family. In this family, we were able to prove that the mutation arose de novo in the affected individual, and it was transmitted to his children. In general, in genetics, we want to have more than one family. We conducted a wide search to identify patients who had the same phenotype, and we were unable to find any. My lab is now focused on ultra-rare genetic phenotypes and understanding their genetic basis. We have encountered this problem repeatedly now. We have compelling biology behind a genetic phenotype, and yet without a second family, it becomes difficult to be certain that you have the right gene without more extensive functional characterization.
What new research directions did this work uncover?
When we had our initial publication on IWC and KRT10 mutations, we saw a remarkably arginine-rich tail appended to KRT10. We thought that the arginine-rich motif was itself responsible for revertant mosaicism. This kindred, however, shows us something different. The frameshift that we are seeing in this disorder is not arginine rich and does not cause mislocalization of the mutant protein to the nucleolus. Since KRT1 is a binding partner for KRT10, this suggests that the reversion is intrinsic to disruption of normal KRT1/KRT10 function, and not necessarily to the specific frameshift motif. This led us in a new direction away from the specific frameshift peptide and toward understanding the basic biology of how keratins function within normal and diseased tissue.
How do you see this research being applied in the future?
The phenomenon of revertant mosaicism is quite interesting. What is remarkable about the skin is that you can see these events happening before your eyes. What is most exciting for us is the possibility that we might be able to enhance the frequency with which revertant mosaicism occurs within this disorder. By better understanding its mechanisms, especially given that it's all occurring via mitotic recombination, we hope that we could ultimately make revertant mosaicism happen on command. We recognize that there are dominant disorders in the skin and other tissues that would be very amendable to [such] therapeutic approaches.
As a physician-scientist, what was your strategy for melding your clinical and research interests?
It is really the early mentorship experience that gives you a model of the career that you want to have. I certainly had a number of friends who were successful in doing a variety of different things, but I think it was the early experience of the power of the skin as a genetic model system that led me to pursue this path. When you choose a path, you want to choose to do something that you love. Not only was the science exciting to me, but it was also important for me to do clinically significant medicine. I chose dermatology because it is not just warts and acne, as some may think, but it provides the opportunity to treat significant disorders including inflammatory, genetic, and autoimmune conditions while working in collaborative teams. What was important for me was that it was not only an opportunity to do interesting science, but also to be a productive member of a classic teaching hospital working environment.
What do you think has contributed the most to your current success as a physician-scientist?
I think mentors help position you scientifically. They help you choose the right laboratory. They help to advise you to find other mentors. I think that one of the most important things is to have people around you who refill the well of scientific curiosity and excitement. There are those mentors who reinvigorate you and help to take you in new directions. Environment is also absolutely critical to people being successful. Environment is a multifaceted thing. It encompasses having the support of the institution and being in a department that has a proven track record of success.
What were some of the challenges that you encountered, at the junior faculty level, when you were establishing your own lab and getting started?
There are a lot of challenges to getting started. One of the primary challenges as a junior investigator is to be seen as being distinct from your mentor. It is particularly difficult if you stay at the same institution. It takes a longer period of time for people to recognize your successes as being uniquely your own. The other challenge is attracting brilliant people to join the lab. Toward that end, I became involved in the MD/PhD program so that I could recruit young scientists to the laboratory. I have to say that when you are starting out, undergraduates and medical students really prove to be some of the best people to have in the research environment, because getting talented postdocs is a hard thing to do before your laboratory has big name recognition. Both of the MD/PhD students in my lab started as medical students who got excited about science much in the way that I did, and then applied to and were accepted into the MD/PhD program.
How do you typically balance the demands of research, clinical duties, and teaching as you strive to be the so-called triple threat as a physician scientist?
Honestly, I do think that it is challenging to be the triple threat. At the same time, it is also very exciting and inspiring. To a degree, I try to do this by compartmentalizing my clinical and my research life. I do the great majority of my outpatient clinical responsibilities on a single day of the week. I am a “pure” clinician on that day. I set aside focused time during the week to address any clinical issues that arise. I break my time as an attending on the inpatient service into two-week blocks, which are more manageable and do not detract from the lab. One of the things that I have found to be particularly useful is that my clinical exposure is the inspiration for a lot of what I do. The time that I spend in clinic is, in many ways, contributing research questions back to the lab. I am fortunate to be able to have a degree of overlap between my research and my clinical practice. As for education, residents and fellows really are excited and engaged in translational work. They actually also contribute pretty significantly to what we do. I constantly feel like the challenge is always to do the best you can in all the things that you do and to set realistic expectations for what you can accomplish in your clinical time and in your research time. It is especially important to be thoughtful and mindful about your personal time and about your family, and the things that you need to do to refill your well of creativity by not always being in the clinical and research environment.
What advice do you have for trainees who are hoping to pursue careers as physician-scientists as they embark on this path?
I mentioned mentorship being important. I think that the lab environment is also very important. Labs become your extended family, to a degree. You also have to make sure that you have the right scientific fit. The research questions have to be about something that really drives you and excites you, but the lab also needs to be an environment where you feel like you have the capacity to develop meaningful relationships with the people who surround you. Certainly, the mentor is an important part of that equation, but I think you learn a tremendous amount from the people who are slightly ahead of you and slightly behind you. You are not successful in isolation. You are successful in a group. You have to make sure to choose an environment where other people who have come before you have been successful and an environment that is a good fit for you intellectually and personally. This is important because science is not always successful, obviously. There are long periods of hard work, and being in the right environment makes that load easier to bear.
About the First Author
Keith A. Choate, MD, PhD, is an Associate Professor of Dermatology, of Genetics, and of Pathology at Yale–New Haven Hospital. He is a physician-scientist who brings insights from skin biology research to his medical dermatology practice. For this work, Dr. Choate received the 2011 Young Investigator Award from the American Academy of Dermatology. Dr. Choate has published more than 30 peer-reviewed articles and chapters and has presented his work at national and international meetings. He is a member of the Medical and Scientific Advisory Board of the Foundation for Ichthyosis and Related Skin Types.
About the interviewers
Freddy T. Nguyen is an MD/PhD candidate at the University of Illinois at Urbana-Champaign. He is the Founder of the American Physician Scientists Association and served on the Associate Member Council of the American Association for Cancer Research, His research interests currently lie at the intersection of biomedical optics and cancer research. He received his B.S. in Chemistry and B.A. in Mathematics from Rice University.
Dania Daye, MD, PhD, is in the internal medicine residency program at Brigham and Women’s Hospital and a Clinical Fellow in Medicine at Harvard Medical School. Dr. Daye is a graduate of the Medical Scientist Training Program (MSTP) and of the HHMI-NIBIB Interfaces program in Bioengineering at the University of Pennsylvania. She is a past president of the American Physician Scientists Association.
Widespread reversion of genetic disease is rare; however, such events are particularly evident in some skin disorders in which normal clones develop on a background of affected skin. We previously demonstrated that mutations in keratin 10 (
Keith A. Choate, Yin Lu, Jing Zhou, Peter M. Elias, Samir Zaidi, Amy S. Paller, Anita Farhi, Carol Nelson-Williams, Debra Crumrine, Leonard M. Milstone, Richard P. Lifton