Learning From Leaders: An Interview With Leonard Zon, MD

Leonard Zon, MD
Grousbeck Professor of Pediatrics, Harvard Medical School; Professor of Stem Cell and Regenerative Biology, Harvard University; Stem Cell Program Director, Boston Children’s Hospital

Leonard Zon, MD, one of two 2019 ASH Mentor Award recipients, talks about the importance of hiring nice people who also happen to be smart.


Did you always know you wanted to go into medicine?

Well, when I came out of the womb, my mother said, “That’s a doctor.” So, the answer would be “yes.” Both of her brothers were doctors, and the dream was to have me continue the tradition. It helped that I always enjoyed medicine and knew it was the right career for me.

She also wanted my younger brother to become a doctor, but he ended up as one of the world’s leading musicologists.

Is there any other career you could see yourself in?

I play trumpet as an extracurricular activity and might have had a chance to be a professional trumpet player. I ran into a problem, though: My brother was a child piano prodigy. I was good, but not that good. In college, I played in several concert bands and performed at many weddings and bar mitzvahs, but it was pretty clear that I wanted to go into medicine.

I still play trumpet every day. I’ve been performing for 35 years in the Longwood Symphony Orchestra, an orchestra composed of members of Boston’s medical community.

Why did you decide to focus in hematology?

During college, I spent a summer volunteering on the leukemia ward at the Roswell Park Cancer Institute in Buffalo, New York, which made me think more seriously about working in cancer biology. Then, while a student at Jefferson Medical College (now known as Thomas Jefferson University), I heard a lecture by Allan Erslev, MD, the researcher who discovered erythropoietin. I was blown away and knew that I had to work with him.

He became an important mentor to me, along with Jaime Caro, MD, who was an assistant professor at the time. That experience gave me the bug for academics. When I finished up in the lab, Dr. Erslev told me, “If you want to do academic hematology, go to Boston.” So, I went to Boston for my internal medicine residency and oncology fellowship.

The other reason was my personal connection to oncology: My mom developed breast cancer while I was in high school. She passed away during my fourth year of medical school. That experience strengthened my resolve to go into hematology/oncology.

During your training, who were the mentors who helped shape your career?

I think it’s very important to collect mentors along the way as you progress through your career. I still have plenty of mentors now!

When I went into residency, the second patient I saw had HIV and was being cared for by Jerome Groopman, MD. I eventually worked in Dr. Groopman’s lab, where he helped me realize my potential and where we pioneered many discoveries in blood cells and HIV. He became one of my lifelong mentors.

“I hear all my mentors’ voices in the back of my head, but I’ve developed my own mentoring style based on what happens in my lab.”

Then, during fellowship, I worked with Stuart Orkin, MD, in his lab. He was an incredible mentor (and a 2009 ASH Mentor Award recipient). He instilled in me a passion for science and the confidence to try any laboratory technique that I needed to learn. It’s been wonderful to have him not only as a mentor, but ultimately as a colleague and a friend. We had offices next to each other for 25 years, and we’re still quite close.

When I was starting my lab at Boston Children’s Hospital, I met Samuel Lux, IV, MD, a 2006 ASH Mentor Awardee. He has a great ability to see the best in everybody and spends endless hours making sure that the people he’s mentoring have done well. I valued every moment I spent with him and the help he gave me on my own experiments – and occasionally on life.

Last, David Nathan, MD, the kingpin of hematology here at Boston Children’s Hospital and 1986 ASH President, taught me how science should be done.

Did you try to emulate your own mentors?

When you’re running a laboratory or any operation, your approach might be influenced by those you trained with, but you don’t have to do it exactly the way they did. I hear all my mentors’ voices in the back of my head, but I’ve developed my own mentoring style based on what happens in my lab.

My guiding principle is to be there for my trainees so, over the years, I developed a set of lectures about the various aspects of running a lab – or just living life. A lecture could cover something relatively simple, like delivering an elevator pitch or approaching a meeting the right way, or more complex management topics, like balancing a budget or figuring out which buttons to push to get someone to do a certain activity. We talk about these topics at lab retreats and “postdoc teas,” two-hour afternoon teas where we delve into a given topic.

Lately, I’ve been doing some even broader lectures, on the topics of happiness and worrying. Again, these are built around behaviors I notice in my lab. I started seeing people putting a lot of pressure on themselves about experiments not going as planned or other disappointments. To help them reframe their thinking, I developed this lecture based on the set of tools I use to try to make me happier when things aren’t going well. It covers appreciating where and who you are, developing confidence, and finding joy in the little things, as well as putting more stock in what you think of yourself than what others think of you.

I also do career mentoring, which is important as people enter the job market or start their postdoc fellowships. That means helping them understand the sets of principles needed to get a job and be successful in it, like giving a good talk. An important strategy is to pick two words to describe your new lab’s topic. It needs to be a “new” field different from your mentor’s field. Then, tell everyone on the interview trail and every student you recruit what your two words are. I think most of the people who work in my lab can get their message across very well.

What is the secret to your success?

First, hire smart people. If you support them and set them up for success, they’ll do great things. Second, hire nice people. Even if somebody has had a wildly successful career, if they’re not an intrinsically nice person, we probably wouldn’t take them in my lab. By creating an environment of smart, nice people interacting, we’ve built a place where people want to be.

Over the years, as different personalities came into the lab, I realized that everyone has one flaw that prevents him or her from being great. As the lab leader, I needed to figure out what that flaw is and counteract it.

What career accomplishments are you most proud of? And how have you handled disappointments?

There are many personal accomplishments I take pride in: When I was starting my lab, I had the idea to use zebrafish as a model system to study blood diseases. I wasn’t entirely sure how to do that, but about nine years in, we had set up the whole system and cloned ferroportin, a mutant gene involved in iron metabolism. Now, we’ve identified five zebrafish mutants that were in novel genes involved in human disease.

In 2007, our lab produced a paper that described prostaglandin E2, a drug that enhances the synthesis of blood stem cells. The drug actually was developed through zebrafish models. Prostaglandin E2 has been used in several patients in clinical trials.

In addition, I started the International Society for Stem Cell Research and was its founding president. It’s difficult to start a society, but I managed to do it with help from a lot of great stem cell biologists. Our membership has grown to 4,500 stem cell researchers.

Of course, I also take pride in my mentees’ accomplishments. Many of them have their own successful labs or are doing amazing things in industry.

Disappointments are always hard. One of my biggest disappointments was as a postdoc fellow. I was trying to clone the erythropoetin receptor – which a friend of mine, Alan D’Andrea, MD, was also trying to do at the same time. We ended up in a little bit of a competition, and Dr. D’Andrea won. For about three months I truly thought I was out of science and my whole life in academia was over. That’s when Dr. Orkin invited me to help him in his work cloning the transcription factor GATA-1. I came up with an idea for how to clone that gene, and we were able to use Dr. D’Andrea’s library in our efforts to clone GATA-1.

Now, when I’m facing a disappointment, I try to figure out how I can attack it or how I can persevere. As Dr. Orkin told me, “The system has a way of rewarding persistence.”

What do you enjoy most about mentoring?

I love having meetings with my postdocs and graduate students – hearing about the data they’ve produced and how excited they are about what they’re learning. I love any time I spend talking science with someone in my lab or in my office – that’s the best part of my day.

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