Along the shore of Seattle's Lake Washington, hints of mist drift across the water as the early morning sun warms the surface. Dr. Katie Peichel casts fish traps tethered to 20-foot ropes into the cold, shallow water. Her intended trophies: dozens of inch-long threespine stickleback fish. The spiny specimens don't look like much, but they have put Peichel at the forefront of a new generation of genetic researchers.
Her lab at Fred Hutchinson Cancer Research Center has established the stickleback as a powerful model for studying complex genetic traits. Now, these humble fish, long studied by behaviorists and evolutionary biologists, “are this really great model that has grown a lot based on the work that I did as a postdoc,” said Peichel. With the aid of a detailed map of the fish’s genome that Peichel created, researchers around the world now study the stickleback to learn how genetic networks affect the development and evolution of multifaceted, or complex, traits.
"Complex traits result from a combination of many genetic factors as well as environmental factors," she said. "By using sticklebacks as a model organism in the laboratory, we can begin to understand the genetic and environmental components of these traits, and use what we learn in the fish to determine how to study similar traits in humans."
Peichel’s current research focuses on three aspects of stickleback biology: the evolution of sex chromosomes (like humans, sticklebacks have evolved X and Y chromosomes that determine each individual’s sex), the genetics of behaviors such as mating dances and schooling, and the genetic factors driving the formation of new species.
She’s excited that those three interests have recently come together in her team’s studies of the unique marine sticklebacks in the Sea of Japan, which lies between Japan and the Asian continent. These fish evolved on a unique trajectory during a two million-year period in which a land barrier cut off the sea from the rest of the Pacific Ocean and other sticklebacks. Led by former postdoctoral student Dr. Jun Kitano, the team discovered that the long-isolated fish independently evolved their own sex chromosome system and behavioral traits, such as courtship dances, that now keep these fish from interbreeding successfully with sticklebacks from the Pacific Ocean.
“It’s the first demonstration where the evolution of sex chromosomes has actually directly contributed to reproductive isolation,” Peichel said.
She is now seeking to understand the evolutionary pressures that may have shaped these fishes’ new genetic system for sex determination. The Japan Sea sticklebacks, Peichel said, offer “a really great opportunity” to add data to existing theories in the field.
The stickleback is a nondescript creature, yet Peichel has helped to elevate it to one of the most important model organisms in the world. And as her work with these fish continue to yield new discoveries about the genetics of complex traits, she never seems to run out of curiosity about the mysteries she hasn’t yet solved.
“There’s just a million questions that I have that I want to answer,” said Peichel, who can trace her inquisitiveness back to a childhood spent exploring the tide pools of the California coast. “I have more questions than I can answer.”
- Updated by Susan Keown, June 19, 2015