Clifford Tabin Awarded Conklin Medal

By Marsha E. Lucas

The Society for Developmental Biology awarded Clifford J. Tabin of Harvard Medical School the 2012 Edwin G. Conklin Medal for his extraordinary research contributions to the field of developmental biology and his exemplary mentoring of the next generation of scientists. Tabin, best known for discovering Sonic hedgehog and demonstrating that it was the molecule responsible for anterior-posterior patterning in the limb bud, was nominated for the Conklin Medal by his former students and postdocs. In a July interview prior to the 71st SDB Annual Meeting, Tabin expressed his appreciation. “[The Conklin Medal] coming from peers in general and from the society [SDB] is very meaningful. ... The fact that ones own students and postdocs would want to do that is heartwarming,” Tabin said.

“I have learned that the reason that I got this award was that a particular former postdoc of mine decided that she wanted to see if other people would be interested in nominating me and she wrote to all of my former students and postdocs and an extraordinarily large number of them bombarded the SDB office with letters. And when the SDB office couldn’t find any other nominees because the letters were buried in the big pile of Tabin nominating letters...they said, ‘Well, I guess this is the only guy this year’ and they gave it to me,” he recalled jokingly.

Tabin began his scientific career as a graduate student with Robert Weinberg at the Massachusetts Institute of Technology in 1976. There he worked on recombinant DNA constructing the first retroviral vector, an essential molecular tool for introducing new genes into cells. He also identified the genetic mutation in a bladder cancer cell line which activated RAS, the first known human oncogene. He was able to show that the mutated RAS gene when placed in a retroviral vector and injected into mice could cause cancer.

In 1984, Tabin began a short postdoc in Douglas Melton’s lab at Harvard University. He along with fellow postdoc Richard Harvey cloned the first Xenopus Hox genes (at the same time Eddy De Robertis’ lab cloned different Xenopus Hox genes). Tabin became interested in studying whether Hox genes were differentially expressed in the hind limb and forelimb. “I said, ‘Why don’t we see if we can bring modern molecular biology to limbs and use Hox genes as a starting point?’”

Since Melton’s lab focused on early Xenopus development and early tadpoles don’t have limbs, Tabin sought out an independent postdoc at Massachusetts General Hospital (MGH). “The independent postdoc is a gamble,” he said. “When people talk to me about it I tell them don’t do it unless you’re a hundred percent comfortable with the idea that if you do it and it falls flat, you’ll do a second postdoc.” Tabin was in no rush to move on to the next stage of his career and his gamble paid off. At MGH he switched amphibian species and studied limb regeneration in newts. Taking a molecular approach, Tabin cloned Hox genes differentially expressed in regenerating limbs and a retinoic acid receptor that functioned in regeneration.

This independent postdoc gave Tabin a head start as he transitioned into a faculty position at Harvard University in 1989. He developed tools for ectopically expressing genes in the chicken embryo, expanding the possibilities for studies in yet another classical limb system. Through a collaboration with Andy McMahon and Phil Ingham, he discovered Sonic hedgehog was the molecule acting in the vertebrate limb bud to control anterior-posterior patterning. This was the first example of a morphogen that acted in a concentration dependent manner to establish distinct developmental fates. He went on to study left-right asymmetry linking the signaling molecules Sonic hedgehog and Nodal in a genetic cascade.

Tabin’s lab has tackled limb development with diverse organisms including chickens, mice, jerboas, and axolotls. He has studied development of the gut, muscles, bones, and tendons to name a few. He helped establish the field of evolutionary developmental biology with his studies on beak development in Darwin’s finches and the evolution of cave fish.

“I’ve always just sort of studied whatever questions I find interesting,” he said. “You can’t start out your career being all over the map or you’d never be able to get your feet off the ground.” However, now he has the luxury to study many questions around a common theme—how morphology arises.

“Fundamentally, the difference between a cat and a mouse is not different cell types. The differences between a cat and a mouse are very subtle differences in how you form morphological structures. ... The subtle differences in morphology make all the difference in giving us the beauty and variety around us,” he said.

In addition to scientific excellence, the Conklin Medal awards great mentors. “I take the mentoring role or the role of launching other people’s careers very seriously,” Tabin said.

This is evidenced by the amount of time he puts into helping his trainees learn to write papers, prepare talks, and if they’re interested, finding opportunities for them to teach. This is important, he said, for their success down the road.

With Tabin’s broad interests, he allows his students and postdocs to pick their own projects. “My basic philosophy is you get the best people you can, you try and raise significant resources so they have a lot of flexibility financially to do whatever they want, and then you just support them in whatever they want to do. ... And if you give really good people a great environment and a lot of resources, they’re going to do great stuff. And if you’re doing it with them, it’s going to be a lot of fun.”

As for his own mentors, he said, “I should start with my parents here because fundamentally what you’re like personally has an enormous amount to do with the way you’re going to run a lab. ... It was my parents who taught me to be a man.”

His father was a physicist and had a similar career in research, while his mother (now deceased) was a psychologist. Being able to share his successes with them throughout the years has been one of the most rewarding parts of his career.

“The meaning of these [awards] are not lost on my father,” he said. Even though there is no actual medal that comes with the Conklin Medal, Tabin said, “Whatever they give me, my dad’s going to ultimately get [it].”