Faculty Interview: Dr. Dan Kessler

Chair of the Cell and Molecular Biology Graduate Group for the last sixteen years, Dr. Dan Kessler has been a beacon of leadership and mentorship for students at every step of their graduate career. The CAMB Newsletter team was thrilled to sit down with Dan and learn more about the road that led him to Penn, his time as a PI, and his advice to current students in these unprecedented times.

Tell us a little bit about your scientific journey. What was your path like?

My parents were teachers. Growing up in Binghamton, NY, my mother was an elementary school teacher and my father a professor of English and a poet at the State University of New York at Binghamton. My role models were teachers, not scientists, and teaching and mentoring have been a central focus of my faculty career. In sixth grade, I had a formative experience during my father's sabbatical semester in Honolulu, HI. The school I attended had an innovative experiential science curriculum involving day trips to the reefs and tidal pools of the island. This hands-on experience with marine life sparked a lifelong passion for biology.

As a freshman at Cornell University, I had my first laboratory experience as a work study student washing glassware and weighing samples in an animal nutrition laboratory. I then joined a bacterial genetics lab for my undergraduate research experience, working with Bacillus subtilis to identify mutants in the branched-chain amino acid biosynthetic pathway. There, I learned to love the unstructured freedom of the lab and the excitement of doing experiments.

From Cornell I went directly to graduate school at Rockefeller University, doing thesis research with Dr. Jim Darnell. I studied the signaling pathways and transcriptional response to interferon signals, identifying the founding members of the STAT family. I've always felt like I peaked in graduate school with regard to impact and productivity, which was a direct result of the talented and supportive people I worked with. At Rockefeller, I had my first exposure to developmental biology and the models used, including the work of Dr. Steve DiNardo, a newly arrived assistant professor. I was fascinated by the three-dimensional transformation of the embryo and the tools for visualizing gene expression.

Motivated to explore this field, I pursued a postdoctoral fellowship with Dr. Doug Melton at Harvard University, studying the inductive signals and transcriptional regulators that controlled germ layer formation in the frog embryo. This work established the direction of my independent research career at Penn. At Harvard, I also had my first teaching experience in an undergraduate embryology course. During the period of my training (1986-1994), I don't recall mentorship being widely discussed, but I was drawn to faculty mentors who were kind and seemed to be genuinely invested in the success and well-being of their trainees. This set a positive example that I have strived to fulfill in my faculty roles. I arrived at Penn in 1995 to join the recently established Department of Cell and Developmental Biology, which has consistently been a wonderfully supportive and scientifically creative community.

What factors influenced your decision to become a PI? When did you know it was the right path for you?

Although not a scientist, my father’s work exposed me to the creative independence and intellectual freedom of an academic career, as well as the joys of teaching and mentoring. Through my research experiences, I came to appreciate how anyone in the lab could be the source of an important new idea, hypothesis, or experimental approach. In thinking about a career in science, I couldn't imagine working in a setting that didn't allow that freedom. All of my scientific role models were academics and I didn't have much awareness of other career paths in science. Choosing graduate school was an easy decision for me, but I had no meaningful understanding of the career beyond the work at the bench; no concept of what it was to publish a paper or write a successful grant. So at an early stage, the choice of an academic career path was a relatively uninformed leap of faith, and my understanding of what was required to be a successful PI was learned on the job. Fortunately, I started my career at Penn during a period that seems far more forgiving with regard to grants and publications, and I was able to navigate the early years of my career with less pressure than current assistant professors experience. I've never really questioned whether this career path was right for me, even during the most stressful moments. I was very lucky to start at Penn together with exceptionally talented colleagues and friends, including Dr. Peter Klein, Dr. Mary Mullins, Dr. Michael Granato, and others, and within weeks of arriving I was certain I had made the right decision, both in career path and institution. That belief persists to this day. 

What was your favorite part about being a PI?

From the very start I loved working with students in the lab, sharing those rare moments of discovery, and seeing them develop independence and succeed in their career goals. I also really enjoyed the process of drafting manuscripts together with students. Once the initial draft was completed by the student we would sit together at the computer and make revisions, working through the language to find clarity in communicating the critical ideas and results. I found that students appreciated this approach as a method for providing guidance on effective writing, leading to a better understanding than simply scribbling comments on the paper. And then of course was just the fun of being in the lab as everybody did their experiments. Like many faculty, I had a habit of passing through the lab every hour or so to check in. And most of all, I enjoyed the conversations, whether about science, sports, politics, family life, and which bar or restaurant got a good review from the weekend. When things were going well, the lab had a family feel to it, which I was grateful for.

What led to you becoming the chair of CAMB? How did you prepare for your role as chair of CAMB?

Early on, becoming chair of CAMB was certainly not a goal of mine. To be honest, CAMB always appeared so large and complex that the job seemed impossible. And now that I've been doing it for 15 years, the job still seems impossible at times. The path to becoming CAMB chair was more organic than strategic. Following the example of my parents, I arrived at Penn with a strong desire to get involved in teaching, mentoring, and advising. I had minimal experience, but felt getting involved right away was important. I joined the Developmental Biology (DB) program within CAMB as soon as I arrived on campus. Dr. Jonathan Raper was DB chair at the time, and also a faculty mentor to me. Eager to get involved, I soon became academic advisor for DB. Much of what I initially learned about supporting and advising students came from Jonathan in advising sessions we held together. Several years later, Jonathan became CAMB chair, and it was a natural move for me to become DB chair. After five years as DB chair, during which the program became Developmental, Stem Cell and Regenerative Biology (DSRB), Jonathan stepped down as CAMB chair and I moved into that role. I'm not sure if this reflected my qualifications or the fact that no one else wanted to do it, but either way, I was definitely in over my head for the first few years. I made many mistakes, but was grateful for the support and patience of the program chairs as I figured it out.

I can say that one of the main incentives for taking on leadership roles in DSRB and CAMB has been the exceptional CAMB administrative team: Meagan, Anna, Kathy, and more recently Christina and Ryan. Their commitment to the students and the quality of the CAMB experience is amazing, and is perhaps the most important contributor to the strength of CAMB today. Even after 15 years, I rely on Meagan to ensure I’m getting it right in all aspects of the job.

Universities claim certain humanistic values that should be reflected in the academic programs. However, it is individual faculty who express those values in their support and guidance of students. The underlying motivation for my service in CAMB has always been a desire to fulfill those values in advocating for the needs, success, and wellbeing of students.

What advice would you give for current students who might one day be interested in such a position?

All of us, students and faculty alike, arrive at Penn with a focus on doing the science. But we bring a breadth of other interests with us and this environment offers a wonderful opportunity to pursue those as well, whether that’s teaching, policy, mentorship, program design, advocacy, etc. My advice is get involved in the things that matter to you. Take a chance and put yourself out there. Engage with your faculty mentors and program leaders in discussing the quality of your experience and propose ideas for how to make things better. Support your peers and pursue issues of value to you on and off campus. All aspects of engagement build a foundation of experience and knowledge that will serve you well in your future careers, especially should you desire a leadership role in graduate education.

Between your time as a PI and as CAMB chair, you’ve helped many students navigate the challenges of a PhD. Based on this experience, what would you say are important traits for a good mentor?

It's critical for a mentor to meet a student where they are. To be open to the changing needs and circumstances the student experiences during their journey in graduate school. To be willing to receive constructive feedback, and even to seek it out, in continually trying to improve as a mentor. To be kind, patient, and to listen intentionally. To understand that what worked well before may not be the best approach right now. To guide a student towards independence, creating space for them to determine the direction of their research and even fail productively. To always value a student as an individual and colleague, especially when the experiments aren't working.

What are your favorite moments to look back on from your time as CAMB chair?

There are many favorite moments, including recruitment events, the annual symposium and, of course, student-faculty basketball and softball. Each year, graduation is a true celebration for me. Having the privilege of acknowledging the accomplishments of our exceptional students makes tangible the success of our program and the value of the work we do collectively, students, faculty, and staff. I attend as many thesis defenses as I'm able, and while each is a hugely satisfying experience, there are those that really stand out and offer a personal feeling of accomplishment. Some students face difficult challenges, whether personal or scientific, during their thesis work, and consider leaving without the degree. Having the opportunity to support such students, help them navigate the challenges to get back on track, and see them succeed in completing the PhD is an especially sweet experience for me. The hug or handshake for these students is particularly meaningful knowing the challenges overcome. 

What was one of the most challenging parts of being the chair?

The most personally challenging part of the job is dealing with faculty who are behaving badly. And most often that bad behavior is at the expense of students in classes, prelim exams, thesis committees, or in the thesis lab. Thankfully, it's a minority of faculty who do so, but when it happens, it can be highly demanding both in emotion and effort for me. For the student, the situation creates a compounded problem with the behavior itself causing harm, as well as the fear that reporting it will create additional difficulties or retaliation. Over the years I've worked hard to cultivate the trust of the students so that when they are facing such situations they can come to me confident that I won't make things worse. In the more extreme cases I will intervene directly with a faculty member, but only with the permission of the student. As you might imagine, faculty who behave badly do not have good self-awareness and do not take constructive feedback well, so providing direct and honest feedback can be an unpleasant experience. In isolated cases, faculty have been dismissed from the graduate group, yet it felt like a failure on my part that a student had such a negative experience. I'm grateful that such circumstances are less common in recent years, and I believe this reflects an increased focus on good mentorship, especially among the junior faculty.

What’s next for you now that you’re stepping down?

I am not retiring or leaving Penn. I will stay close to CAMB and will continue to advocate for, support, and advise students. Whether this will be in an informal or formal capacity will be determined with Dr. Craig Bassing, once he becomes chair in July 2026. I will work closely with Craig to ensure a successful transition into his new role. I may even continue to hold office hours. Beyond CAMB, it’s my intention to remain engaged in graduate education at PSOM, and possibly at the university level, focusing on program development and policy, student resources and advocacy, as well as possibly taking on a course director role. As CAMB chair, I have worked very closely with BGS leadership for many years, and I’d be eager to contribute to the broad mission of BGS. I have also served on the Faculty Advisory Council for Access and Academic Support, chaired by the Vice Provost for Education, and I’m excited to explore the possibility of contributing to the graduate education mission at the university level. And I will continue as co-director of PennPREP, the impactful post-bac pathway program in PennMed. There are many avenues for me to stay engaged in this meaningful work, and to continue supporting the success and wellbeing of graduate students.

What do you enjoy doing outside of work?

At 61 years old I try to stay active, including basketball, softball, yoga, and the gym, as well as hikes with the dogs. The past year has been a challenge as 50 years of basketball got the better of my arthritic knee. I spent most of 2024 trying to get the knee back into shape but ultimately had a knee replacement in December. I'm doing well now and although not back to basketball, I have started playing softball again. I'm a Philly sports fan, but my enthusiasm doesn't reach the extremes of those who grew up in Philly. I definitely try to get to a few Phillies and Sixers games each year. A favorite cultural activity is BalletX, a local modern ballet group that partners with young choreographers in creating new works. I recommend BalletX to anyone with an interest or curiosity for modern dance.

What is one thing you hope every CAMB student will take away from their time at Penn?

What I hope for every CAMB student is that they leave their graduate school experience with strong confidence in their abilities and ideas, built on a foundation of research accomplishments. That they build a broad supportive network of peers and faculty to take with them into the next stages of their career. And that they retain, and even expand, the joy of doing science, which is what brought them to CAMB in the first place.

Any closing words of advice for the current cohort of CAMB PhD students?

Recent months have been the most challenging, stressful, and chaotic period of my career as a faculty member. It’s essential to acknowledge the attacks facing our community and institution, and the resulting fear, uncertainty, and harm related to identity, immigrant status, family, research support, and career. Despite these overwhelming circumstances, I urge you to stay away from hopelessness, to engage in causes of importance to you, to raise your voice, and to take care of each other. This country will always need science and scientists, and your persistence in pursuing your research and education, especially now, gives me hope. I believe there are better days ahead, and although the path is uncertain, your intellect, creativity, persistence, and energy are essential for us to get there.