Patients, cells, and organelles: The intersection of science and serendipity
Authors: Nicholas F. LaRusso
Journal: Hepatology (2011)

I was flattered when Keith Lindor asked me to contribute to the "Master's Perspective" series, especially when I saw the list of prior contributors, a "Who's-Who" of hepatology. It was reassuring that I was friends with all the prior contributors, collaborated with many of them, and was critically mentored by one of them (Alan Hofmann) (Fig. 1A). Indeed, as you will see later, my career in gastroenterology was also the result of a serendipitous opportunity1 that emerged when one of the other prior contributors (Al Czaja) had an unexpected change in his career plans. Thus, this essay will consist largely of personal anecdotes about the often unpredictable experiences and life-changing events that influenced my career as well as my science. In an effort to be helpful to younger colleagues, and with all humility and lack of presumption, I will also share some conclusions about how to develop a successful career in academic medicine. (A) Alan Hofmann, (B) Christian deDuve, (C) Bill Foulk on teaching rounds, (D) The BARF group. Arrows show Alan Hofmann and Nick LaRusso. With that in mind, a key conclusion that I've come to from my experience as a physician-scientist (that might be useful to those of you who aspire to someday write your own "Master's Perspective") is to develop a unique scientific niche that results in new and important information related to understanding and intervening in disease. To quote one of my mentors, the Nobel Laureate Christian de Duve (Fig. 1B), "…as scientists, we do not simply read the book of nature, we write it…".2 Oh, and one other thing—it's important to hang around with really smart people! (Like the contributors to this series). DOM, Department of Medicine; ECG, electrocardiogram; GI, gastroenterology; NIH, National Institutes of Health; PBC, primary biliary cirrhosis; PSC, primary sclerosing cholangitis. I grew up in Brooklyn, NY, the oldest of five. My parents were loving, supportive, and hard-working; neither had advanced beyond high school but both had great aspirations for and expectations of their children, especially their oldest son. As a Catholic boy raised in an Italian-American family, the professions that received the highest esteem were medicine and the clergy. Although the idea of becoming a priest entered my mind, it stayed there for less than 30 seconds! So, my earliest memories include the admiration and respect my parents had for physicians and the medical profession. Indeed, the unspoken, and occasionally spoken, idea that I would ultimately become a doctor was fairly pervasive even though none of my extended family were physicians. This not-so-subtle expectation was enhanced by my interactions with our family physician, Dr. Bernard Melnick. Melnick would visit our house (doctors still made house calls then) whenever I had a sore throat, which was often as a child, and regularly inject me with penicillin. Although I feared the injections, I was in awe of the confidence, compassion, and command that this individual displayed. He seemed to always be totally engaged, focused, and energized, and tried hard to alleviate my fears. On the occasions when we would visit his office, it was clean, well-organized, and efficient. So, my exposure to our family doctor provided me a concrete role model, a vision of what a doctor's life might be like, and the essence of what physicians did—they helped people! As a teenager, I had the great privilege of attending Brooklyn Prep, an all-boys Jesuit college preparatory school, in the heart of Flatbush. Prep was one of four Jesuit high schools in New York City, was highly competitive, and required a challenging entrance exam. Students were predominantly first- and second-generation Italian-American, Irish-American, and Polish-American kids who, like me, were often the first in their families to aspire to a college education. The Jesuit curriculum "trained us for nothing, but prepared us for everything".3 We entered as boys and left as educated young men. The three-century tradition of Jesuit education was based on the principal of "cura personalis"—care of the entire person. In practice, its distinguishing characteristics included a rigorous intellectual and athletic experience, an energetic and demanding academic environment, a focus on the common good, and a compassionate commitment to each individual in society. This enlightened environment and the challenging culture of personal development further encouraged my interest in medicine in at least three ways. First, I learned to be disciplined, focused, and able to multitask. Second, it emphasized what the essence of medicine was all about: helping others. And third, it instilled a sense of personal responsibility to society, what the Jesuits called "noblesse oblige", which, loosely translated, means because we had been given so much, we had an obligation to give back. So, when I entered Boston College on an academic scholarship, medicine was my trajectory. Any lesson in this story for you aspiring physician-scientists? Don't ever forget why you became a physician: to help people! When I was a third-year medical student at New York Medical College working at Metropolitan Hospital in upper Manhattan, which was a wonderful environment for gaining confidence in taking care of very sick patients, my chief resident was a brilliant young internist named Bob Cattani. He had spent a short time at the Mayo Clinic before taking over my hospital team. As a result of this experience, he strongly encouraged me to apply for an externship at Mayo during my fourth year of medical school. He opined that the "blood and guts" medicine I was experiencing at Metropolitan Hospital, a huge indigent care facility dealing mainly with gunshot wounds, drug addiction, and alcohol-related illnesses, although critical to my evolution as a physician, could be refined and expanded by exposure to the Mayo model of care. With that in mind, I applied for and successfully obtained a 3-month externship at the Mayo Clinic during my fourth year of medical school. In perhaps a foreordained and certainly fortuitous scenario, I was assigned to the Gastroenterology (GI) Division at the Mayo Clinic and made hospital rounds with Bill Foulk, Sid Phillips, and Dick Reitemier. I was enormously impressed by their depth of medical knowledge, their humility, their focus on the needs of the patient, and their commitment to education. The Mayo environment was a stark contrast to the intense and often competitive atmosphere I experienced in New York. The Mayo academic climate was relaxed, nurturing, and supportive; there were few examples of one-upmanship or self-promotion on rounds. The focus was always on how the team could most help the patient. An example of this was how Bill Foulk taught on rounds (Fig. 1C). Although he had written extensively on primary biliary cirrhosis (PBC), a disease which was just beginning to be defined, he rarely directly quoted his own literature contributions. Alternatively, in a rather matter-of-fact way, he gently communicated his enormous insights about this poorly understood syndrome, hardly ever mentioning the fact that he had been one of the earliest to recognize and describe the disease. Indeed, this was my first exposure to liver disease other than alcoholic liver disease, which was basically all I had seen in New York. I was also exposed to Ralph Smith, a brilliant cardiologist who designed the first software programs for interpreting electrocardiograms (ECGs). I would spend part of each afternoon in the ECG laboratory reviewing hundreds of ECGs. After 2 weeks with Ralph, I could interpret just about any ECG pattern. This skill was particularly useful to me because my first rotation as an intern was in the Cardiac Intensive Care Unit at Metropolitan Hospital. Indeed, I became the go-to person among the house staff for complicated ECGs. I left Mayo in awe of the institution and the faculty, and determined to return for my residency training, which I subsequently did. So, what if any lessons can be culled out of this experience? For your clinical training, go to the best places with the best people and choose an atmosphere that is most conducive to your learning style! The importance of this particular advice will come up again later. My residency experience at the Mayo Clinic following an internship at Metropolitan Hospital was outstanding. During those 2 years, I refined the clinical skills I had developed in an inner-city hospital by exposure to a wide spectrum of diseases and a superb group of attendings (at Mayo, they are called "consultants"). Unfortunately, I could not make a decision about a subspecialty as I approached the end of my residency primarily because I enjoyed just about every rotation I had experienced. As a result of my indecision, I tentatively planned a 1-year locum tenens in the region, primarily to earn money to help pay off my college and medical school loans. Then a serendipitous event occurred. Al Czaja, a world-renowned hepatologist and a previous contributor to the Master's Perspective series, was scheduled to enter a National Institutes of Health (NIH) GI Fellowship at Mayo. However, he got drafted; this was at the height of the Vietnam War, and doctors were in short supply. I was available because I had joined the army reserves, and was offered the "Czaja slot". Because I had no other concrete plans, and had thoroughly enjoyed my GI rotations, I accepted. The NIH training grant, which Mayo had recently been awarded by NIH with Bill Summerskill as the principal investigator, required 2 years of full-time research followed by a year of clinical training. The career lesson from this experience, if there is one, is that fate is often a major determining factor in one's career. Things happen in life that are totally unpredictable, and I would encourage a willingness to be flexible and alert to unexpected opportunities. To quote Carly Simon and James Taylor in their memorable rendition of "Mocking Bird", sometimes you need "…to ride with the tide and go with the flow". Having accepted Czaja's position in the NIH training program, I entered the GI unit in 1972.The unit at that time was flourishing under the visionary leadership of Bill Summerskill and populated with such luminaries as Bill Go, Sid Phillips, Juan Malagelada, and my ultimate mentor, Alan Hofmann (Fig. 2). Alan accepted me into his group with some reluctance because I had virtually no research experience and some uncertainty about how committed I was to a career in research. GI Research Unit, July 1972. My experience with Alan was life-changing; he was a constant source of ideas, always optimistic and encouraging, and a charismatic teacher. However, he traveled a lot. Thus, I was often left to my own skills at the bench which unfortunately were quite limited. One of Alan's senior fellows, Neville Hoffman, a brilliant scientist from Perth, Australia, took me under his wing and was critically important to my research evolution. It was a marvelous 2 years during which I studied biliary lipid secretion and bile acid metabolism in patients using creative intubation techniques and a new radioimmunoassay for serum bile acids developed in the GI unit.4-6 I began to consider the possibility that I might have something to contribute in research. It seemed I had an inquisitive and sometimes creative mind, and that my liberal arts education in high school and college prepared me well for communicating—I wrote effectively and clearly and lectured with increasing confidence. A monumental turning point in my career happened one afternoon when Alan invited me to his house for a couple of beers after one of our lab meetings. These meetings occurred on Friday afternoons and were called the BARF meetings (BARF stood for Bile Acid Research Fellowship!) (Fig. 1D). Over more than a couple of beers, Alan gently suggested that, if I was serious about an independent research career, I should consider expanding my research training at a more basic level. He was sufficiently visionary to realize the importance of the evolving fields of cell and molecular biology to the future of research in general, and to GI research in particular. I accepted his advice with enthusiasm. At that time, and to this day, the Mayo Clinic had a program called the Mayo Foundation Scholar Program; fellows who were identified as potential faculty were offered the opportunity to go elsewhere to learn new skills and bring them back to Mayo. And Mayo would assume all financial responsibility! The philosophy was based on the tradition started by the Mayo Brothers, who traveled all over the world to learn new things and bring them back to Rochester, MN. So with the support of Doug McGill, the division chief at the time, Alan arranged for me to visit laboratories at the NIH, Yale University, and his alma mater, the Rockefeller University. I presented seminars, met people, and talked science with the goal of deciding where I would spend my 2 years as a Mayo Foundation Scholar. The decision turned out to be an easy one. I was accepted as a Guest Investigator in the Department of Biochemical Cytology at the Rockefeller University, headed by Christian de Duve who had just been awarded the Nobel Prize for his work on cell fractionation and identification of the lysosome In July 1975, I joined de Duve's laboratory and worked directly with two nurturing senior scientists in de Duve's group, Miklos Müller and Stanley Fowler. The more exposed I was to cell biology (I audited selective graduate courses at the Rockefeller University), the more I enjoyed research and the more confident I became that I could make a contribution. In part because my work with Alan had focused on biliary lipid secretion but also because I had published an article on biliary metal secretion,7 I continued to focus my attention on the liver during the Rockefeller years, basically trying to understand how molecules get into and out of hepatocytes.8 This experience taught me the importance of concentrated, extended research training; by the time I joined the faculty at Mayo, I had had a total of 4 years of full-time research training: two with Alan studying primarily humans, and two at the Rockefeller University, studying primarily cells and organelles. Moreover, I became conversant with a scientific discipline (i.e., cell biology). I emerged from my experience at the Rockefeller University with additional confidence and a perception of myself as a physician-scientist and an epithelial cell biologist. What's the lesson here for aspiring physician-scientists? Get as much research training as possible with the best people in the best laboratories, and become fully conversant with a scientific discipline. And one more thing: be willing to take the advice of your mentors! Although Alan was my primary research mentor, I published an article during my NIH fellowship with Bill Summerskill on chronic active hepatitis.9 This experience both exposed me to patients with this condition as well as to a master clinical hepatologist. I found I really liked seeing patients with liver disease, especially if, like Summerskill, I had something substantive to contribute to their care. During my third year of fellowship, which was primarily clinical, I worked almost exclusively with Doug McGill, the Division Chief, who had a practice focused entirely on liver disease. I saw a wide spectrum of liver disease with Doug, and my attraction to clinical hepatology continued to grow. Doug was also a master clinician conversant with the literature, but he had a pragmatic approach and could very quickly get to the bottom line, which suited my personality very well. My growing interest in liver also related to the fact that my research with Alan had focused on biliary lipid secretion, although at that time, the conceptual distinction between the parenchymal liver (i.e., that made up of hepatocytes) and the biliary tree (i.e., that made up of cholangiocytes) had not fully emerged. Nevertheless, given my initial research experience with Alan and then Bill, and my clinical training with Doug, hepatology was a natural area for my focus. Besides, and this is important, I was fascinated by the liver from a physiologic and pathophysiologic perspective at a time when hepatology was emerging as a distinct discipline within the science and practice of gastroenterology. So, hepatology became my shtick! What's the lesson here? I think the most successful physician-scientists, regardless of how basic their research, maintain a continuous connection with patients. And ideally, the kinds of problems they see in their clinics provide the insights that spawn the hypotheses and questions they address in their labs. More on this below. During my postdoctoral research at the Rockefeller University, my work focused on hepatocytes. When I returned to Mayo and established my own laboratory, my initial R01 (research project grant) addressed the cellular mechanisms of hepatocyte secretion. My first independent contributions defined the excretory pathway within hepatocytes that were important in the transport of metals and in the disposition of cellular digestive products resulting from hepatocyte lysosomal degradation.10-16 The work was progressing very well due to the outstanding fellows that worked with me in the early years, including Rick Sewell, Greg Gores, Gene LeSage, and Jack Gross. As I was developing my laboratory, I also explored options for the focus of my clinical activities. Although I had significant protected time as a result of substantial hard money support from Mayo plus the rapid approval of my first R01, I enjoyed seeing patients and wanted to develop a focused area of clinical activity. The liver diseases that were attracting the most attention at that time, before the explosion of interest in viral hepatitis, were already the focus of Mayo colleagues. Rollie Dickson, Dick Fleming, Keith Lindor, and Jurgen Ludwig were defining the natural history of PBC; Bill Summerskill and Al Czaja were describing the clinical and biochemical features of autoimmune hepatitis; and what work was being done at Mayo in alcoholic and drug-induced liver disease was generally the purview of Doug McGill. So, my challenge was to find a disease that needed definition and clarification, that no one else at Mayo seemed to be interested in, and that I could use to help advance my career. I settled on primary sclerosing cholangitis (PSC), probably for all the wrong reasons and not with a lot of initial support. The disease was esoteric and obscure, generally mentioned, if at all, in a single paragraph in most hepatology textbooks. Jurgen Ludwig, our superb hepatopathologist, told me that "…this disease simply does not exist because I have never seen a case at autopsy". At any rate, a serendipitous partnership with a bright and very energetic GI fellow, Russ Wiesner, led to the publication of an important article describing the clinical, biochemical, and histologic features of patients with PSC seen at Mayo.17 With the advent of endoscopic retrograde cholangiopancreatography, which came along just at the right time for someone interested in studying PSC, and the resultant increase in its diagnosis, Russ, I, and many others at Mayo were able to generate a large series of studies that put this disease on the map,18-29 including the first randomized clinical trial in PSC.30 Thus, PSC became a well-recognized and increasingly diagnosed, albeit still idiopathic, cholestatic liver disease and Mayo became a major referral center for this syndrome. I seemed to have chosen well and at the right time, clearly more a matter of luck than brilliance! While my laboratory was still primarily focused on the pathobiology of hepatocytes, I had somewhat of an insight for reasons that, quite frankly, I don't even remember. I hypothesized that the epithelial cells that lined the biliary tree were likely the target cells for many of the cholestatic liver diseases (PBC, PSC, cholangiocarcinoma, etc.) that were increasingly being seen in our clinics. Indeed, I had tucked away in my "idea file" years earlier that a future area for fruitful exploration might be understanding the biology of the cells that lined the biliary tree (we subsequently coined the term "cholangiocyte" for these cells at the first American Association for the Study of Liver Diseases [AASLD] Single Topic Conference on the Pathobiology of Biliary Epithelia that I coorganized with Al Sirica in 2000). The working hypothesis was, and still is, that a group of diseases, which we termed the "cholangiopathies",31 could be conceptually clustered despite different etiologies, because their common final pathway was alteration in the phenotype of the cells that lined the biliary tree, i.e., the cholangiocytes (Table 1). The problem at the time, however, was that there were essentially no techniques available to study cholangiocytes. So, because scientific advances require techniques to answer questions and test hypotheses (a principle that de Duve often emphasized), I devoted a substantial amount of time and effort developing methodologies to investigate cholangiocyte biology (Fig. 3A),32-40 including an animal model of immune-mediated cholangitis.41 With those techniques in hand, and with the help of outstanding fellows (Moto Ishii, Akinobu Kato, Stuart Roberts, Gianfranco Alpini, Chee-Kiat Tan, Yoshi Ueno, John Phillips, Raul Marinelli, Flo Que, Kostas Lazaridis, Emanuella Cova, Ming Chen, Steve O'Hara, and Jonathan Dranoff) and superb technicians (Pam Tietz and Patrick Splinter), we began to systematically define the secretory, absorptive, and proliferative activities of cholangiocytes as well as the interaction of cholangiocytes with microbes. And wherever possible, we identified the proteins and signaling pathways responsible for these activities. Our strategy was always to first understand normal cholangiocyte function in order to allow the generation of hypotheses relevant to disease.42-66 (A) Experimental models to study cholangiocyte biology. (a) Scanning electron micrograph of a group of isolated cholangiocytes after separation using immunomagnetic beads. Note that the prominent microvilli (arrowheads) are limited to one side of the cells. Magnification = 4400. (b) Transmission electron micrograph cross-section of normal rat cholangiocytes in culture demonstrates characteristics of polarized cells with apical microvilli (arrowheads) and numerous basolateral intercellular interdigitations near the collagen-coated filter denoted by asterisk (*) (bar = 2 mm, magnification = 7500). (c,d) Transmission electron micrograph of (c) apical and (d) basolateral plasma membrane domains revealed similar homogenous vesiculated membranes of varied shapes and sizes without apparent contamination of other organelles (bar = 0.5 μm, magnification = 22,500). (e) Three-dimensional reconstructed image of the intrahepatic biliary tree isolated from normal rat liver. (f) Light micrograph of an unstained isolated bile duct unit from rat liver. After overnight culture, the two ends seal to form an enclosed unit. A single layer of epithelial cells with a thin outer layer of connective tissue surrounds the lumen. (g) Microperfused intrahepatic bile duct unit isolated from rat liver, manually dissected and cannulated with micropipettes. (h) Transmission electron micrograph of C. parvum infection of cultured human cholangiocytes. A parasitophorous vacuole contains a developing parasite stage that is intracellular but extracytoplasmic. A macrogamete is shown in the inset, demonstrating development of sexual stages of the parasite. Bar = 1 mm. (B) Nick LaRusso at one of his lab meetings talking about cholangiocyte cilia. So, what's the lesson here? Well, there are several, and they're all important. First, physician-scientists develop the questions they study in the laboratory from the patients they see in the clinic. Second, don't always listen to your senior colleagues (sorry Jurgen). Third, propose the questions and then make sure you develop the necessary techniques rather than the other way around (avoid the "have technique, looking for a question" approach). Finally, make sure you're having fun; insights require enthusiasm. I never purposefully aspired to administrative leadership positions within academic medicine. Indeed, for the first 10 years of my career, I focused entirely on developing my laboratory and a focused clinical practice, and turned down multiple job opportunities as Division Chief at other institutions. However, in the late 1980s, Bob Frye, a world-renowned cardiologist, became the fourth Chair of the Department of Medicine (DOM) at the Mayo Clinic, and asked me to be his Vice-Chair for Research. By then, my laboratory was established and progressing well. In addition, I greatly admired Bob and felt strongly that under his leadership the DOM had the capacity to expand its research enterprise, and so I accepted the position. I found that I liked medical administration. I enjoyed both developing strategy and executing tactics, and found building something new was professionally rewarding (not unlike what one does in the laboratory). Indeed, colleagues have described my management style as one of "visionary pragmatism"; I like to decide where to go and then execute in getting there. When the position of Chief of GI at the Mayo Clinic became open, I was offered the opportunity and accepted it with enthusiasm. I spent 9 years as Chief of GI and consider my major contributions to be doubling its size by recruiting outstanding individuals, expanding the research enterprise, and restructuring the division into interest groups and focused clinics. Because of the disciplined approach that I learned from the Jesuits (i.e., "age quod agis", that is, "do what you're doing"), as well as my willingness to delegate to the outstanding individuals who helped me lead the division, especially Keith Lindor, I found that I could continue to expand my research program, maintain a focused clinical practice, and lead what ultimately evolved into the largest (some would say the best) division of gastroenterology, all at the same time. Moreover, I was privileged to become President of the AASLD during the 1990s, as well as editor of Gastroenterology. I loved what I would call the "structured variety" of my professional life; each day was different but the weeks had a definite balance and rhythm around research, practice, education, and administration. I divided the week into 10 half days and distributed my time in those buckets among these various responsibilities. Nevertheless, my professional identity was always that of a physician-scientist, and I was careful to assure adequate time and attention to my laboratory. In 1999, I was offered the position as Chair of the DOM at Mayo, an opportunity, quite frankly, that I never seriously aspired to, but one that I accepted with great enthusiasm and excitement. My 9 years as Chair of the DOM were among the most satisfying of my professional life. With the help of superb vice and associate chairs, skilled administrators, and brilliant division chiefs, we developed an ambitious strategic plan for the department, doubled its size, increased NIH funding four-fold (moving our Department from 37th to 12th in NIH funding for departments of medicine) and undertook a major departmental restructuring through fusion of several existing divisions, establishment of new ones, and development of programs in aging, innovative health care delivery, clinical immunology and immunotherapeutics, integrative medicine, global health, translational immunobiology and biodefense, and professionalism. Many of these programs have subsequently evolved into centers serving the entire Mayo enterprise. So, what have I learned from these experiences that might be of value to young colleagues? Try hard to get the right first job; I did and that is why I have never left Mayo. Make sure your laboratory is up and running successfully before you seriously consider major administrative responsibilities, however seductive having a title might seem. Be organized in the use of your time; your ideas and your time are your most valuable assets. Be open to opportunities that you may never have aspired to, but know who you are; in my case, I am always a physician-scientist. And make sure you have fun (I think I already said that but it is worth saying again). My research program, being as objective as I can be, is thriving and remains the most satisfying component of my professional activities. We continue to develop new areas in cholangiocyte pathobiology based on the strategy that we need to understand how cholangiocytes function normally to generate hypotheses relevant to how their dysfunction might result in disease. Currently, the laboratory is heavily focused on the function and dysfunction of cholangiocyte primary cilia, an organelle that historically had been considered vestigial but more recently is recognized as critically important in development, cancer, and cystic kidney and liver disease (Fig. 3B). Our work has demonstrated that cholangiocytes express primary cilia that act as mechano-, chemo-, and osmosensors, display an array of key functionally important proteins, and are critical to normal cholangiocyte function and important in cystic liver disease.67-75 The work has often been devised and always executed by brilliant fellows (Anatoliy and Tetyana Masyuk, Sergio Gradilone, Jesus Banales) and superb technicians (Bing Huang, Angie Stroope, Gabriella Gajdos, Brynn Radke, and Christy Trussoni). Moreover, we have been able to identify molecular targets related to cystic liver disease that have already led to a successful clinical trial.76 In addition, we have begun to explore the role of small, noncoding RNAs in normal and abnormal cholangiocyte signaling,77-80 and we are developing hypotheses around the concept of the "activated cholangiocyte" and the consequences of this activation. I remain grateful for the opportunity to continue to influence the lives of my younger colleagues. Throughout my career and the lineage of the laboratory, I have had the privilege to work with and mentor a myriad of students, technicians, and postdoctoral fellows. Their careers in the United States and abroad have followed successful trajectories leading to admission to medical school, establishment of their own independent laboratories, and appointments as professors, division chiefs, and department chairs. I remain in touch with many of them and continue to collaborate with some. I consider them my most important legacy. My clinical activities now center primarily on a subset of the cholangiopathies, namely, biliary tract malignancies. Importantly, related laboratory efforts are focused on developing biomarkers for early detection of cholangiocarcinoma and relating abnormal ciliary function to the development of this devastating malignancy. Having stepped down as Chair of the DOM in mid-2008, I can now devote my time to new initiatives. Recently, we were awarded a Silvio O. Conte Digestive Diseases Center by NIH on Cell Signaling, of which I am the principal investigator. In addition, I am the medical director of the Mayo Clinic Center for Innovation, a new institutional initiative whose mission is to transform the experience and delivery of health care. This opportunity has provided me with a whole new set of exciting and interesting challenges and exposure to the evolving disciplines of innovation, design thinking, and entrepreneurship. I intend to continue all these activities as long as I and my colleagues (and the NIH) feel that I am making reasonable contributions. And, I approach the next phase of my career with excited interest in and curiosity about what the future holds. I trust that this very personal perspective will inform some, inspire a few, not bore too many, and encourage those who read and reflect on it that the life of a physician-scientist is not a bad way to spend one's time. Discovering how cells normally work and what goes wrong when they become diseased, being able to make a difference in the lives of people suffering from sickness, helping to "write the book of nature", working with very bright individuals and helping to promote the careers of younger colleagues, and building something that did not exist before is, to quote Ralph Waldo Emerson, "…to leave the world a bit better…and to have succeeded". It is also a way to have a lot of fun! I would like to express my gratitude to Debbie Hintz and Pamela Tietz who helped with the preparation of this manuscript and to Alan Hofmann for providing me with Fig. 1D.