A University of Florida scientist whose interest in embryonic development and evolution led him to discover the molecular building blocks that shape appendages ranging from feet to flippers was named a Howard Hughes Medical Institute Early Career Scientist on Thursday, March 26, a distinction given to only 50 researchers in the United States.
Martin Cohn, Ph.D., a developmental biologist and a member of the UF Genetics Institute, became the only Florida scientist to be selected for the competitive HHMI program, placing UF in the company of research institutions such as Stanford University, Harvard University and The Johns Hopkins University.
The HHMI Early Career Scientist program is intended to provide support to the nation’s best early career faculty who have reached a critical point in establishing vibrant research programs.
“HHMI’s support to stellar scientists like Dr. Cohn who are at the peak of their creativity is a wise investment, and I think there will be inevitable returns in terms of scientific discoveries and biomedical progress,” said Win Phillips, UF’s vice president for research.
Researchers from U.S. universities and medical schools chosen for the Early Career Scientist Program become HHMI employees, but remain at their home institutions, receiving their salary plus $1.5 million in laboratory support over six years to pay the costs associated with a high-level research program.
“We saw a tremendous opportunity for HHMI to impact the research community by freeing promising scientists to pursue their best ideas during this early stage of their careers,” said HHMI President Thomas R. Cech. “At the same time, we hope that our investment in these 50 faculty will free the resources of other agencies to support the work of other outstanding early career scientists.”
Cohn became interested in the evolution of limbs while an undergraduate at the University of Texas at Austin. He received his master’s degree in biological anthropology at Kent State University and his doctoral degree in developmental biology at University College London. Cohn is currently an associate professor in the biology department of the College of Liberal Arts and Sciences and the anatomy and cell biology department in the College of Medicine.
His findings have led to new levels of understanding of evolutionary processes and shed light on human problems such as birth defects.
“I realized that if I wanted to understand how animal form changes during evolution, such as how the skeleton evolved or how snakes lost their legs, I had to understand development, because that’s when the genetic blueprint for the body is being executed,” Cohn said.
He began by studying chick embryos, a classic scientific model of limb development. At University College London, he discovered that the embryonic master switch for limb formation was a multifunctional protein called fibroblast growth factor. The finding, published in the journal Cell, was later proven true for other animals, including people.
After finding the trigger, Cohn set out to find what determines the precise positioning of limbs, such as hands on the ends of arms at the shoulders, and feet on the ends of legs protruding from the trunk.
His research led him to the Hox family of genes, which direct the formation of body structures in organisms ranging from worms to people. His work showing that Hox9 genes determine where limbs develop along the trunk was published in the journal Nature in 1997. He went on to discover the molecular basis for loss of limbs during snake evolution and the role of Hox genes in the origin of jaws — findings that were published in Nature in 1999 and 2002.
Since arriving at UF in 2003, Cohn’s group has discovered the evolutionary origin of the genetic program for fin development, shown how this program was modified to form fingers and toes, and identified the molecular basis for the loss of legs during whale evolution. The group has also published widely on the origin of skeletal development.
Along the way, Cohn’s lab noticed striking similarities between the processes that control limb development and those that regulate development of the genitalia. They decided to ask whether the same genes could be involved in development of these distinct appendages.
“We’re beginning to uncover the genetic and cellular processes that take place in external genitalia development, like outgrowth and closure of the urethral tube,” Cohn said. “The incidence of genitourinary malformations in humans came as a huge surprise to me. A staggeringly high frequency of one in 250 kids has a urethral tube defect, and that number has more than doubled in the past 30 years without an explanation.”
Understanding how genes respond to the environment is important for identifying the basis of these malformations, Cohn said.
“Dr. Cohn can work with the tools of molecular biology to find out what’s happening at that level and he looks to see if what he is predicting is actually happening in the animal — the only place that has any real meaning,” said Dr. Kenneth Berns, director of the UF Genetics Institute. “His work has been novel and fresh and I can see why it captured the interest of the Howard Hughes Medical Institute.”