Most cell biologists wouldn't usually think of working with creatures from Antarctica and the tropics, but Rachael Ream isn't a run-of-the-mill cell biologist. Hooked on the cytoskeleton, Ream's fascination with comparative physiology made her choose the cells that she worked with carefully. Wondering what effects temperature might have on cytoskeleton formation, Ream decided to work with keratocytes; mobile cells that migrate across a wound to protect creatures from infection, inching forward by actin polimerization. Ream realised that if she turned to ectothermic fish ranging from the poles to the equator, she could work with cells that were adapted to temperatures ranging from below zero to almost 40°C! Watching the cells shuffle across a microscope slide, it was clear that temperature had a dramatic effect on the cell's mobility.
But when Ream suggested her project to her advisors, George Somero and Julie Theriot, they weren't even sure whether the species she planned to work with had keratocytes! Undaunted, she set off for 6 weeks of intensive field work on the southern continent; `Antarctica was the best experience' remembers Ream. After capturing several Trematomus bernacchii from the icy waters, Ream's tenacity was rewarded. The fish had keratocytes, allbeit rather sluggish ones.
Returning to her home lab, Ream set about working with fish from tropical and more temperate climes, choosing two eurythermal species that are content at any temperature from approximately 5-40°C, and a tropical stenotherm that prefers a more restricted range from 26-30°C. Acclimating the fish to a range of temperatures, Ream collected scales from the fish, and cultured the keratocytes that came with them. Watching the cells as they crawled across the microscope stage, it was clear that as the temperature rose, the keratocytes all speeded up, no matter what temperature they had been acclimated to. And when the cells reached the fish's preferred temperature, all three species move at the same pace, outstripping the sluggish Antarctic keratocytes.
But Ream noticed something else. As she increased the temperature of the keratocyte's microscope slide, they seemed to get distracted. Instead of moving directly, in a straight line, they started to wander away from their course, and some even began moving round in circles! And Ream also noticed that the keratocytes that had come from fish acclimated to lower temperatures tended to hold their course better as the temperature rose than keratocytes from fish acclimated to warmer temperatures; they were all over the place. Acclimation temperature had a dramatic effect on the cell's bearings. Ream realised that there must be different cellular mechanisms involved in governing the cell's sense of direction and speed, and that she could use the keratocytes temperature sensitive behaviour to solve intriguing questions about actin polymerisation.
Delighted that her longshot experiment has turned out so well, Ream adds that she is surprised that the Antarctic fish's keratocytes were so much slower than their temperate cousins. `We still do not know what this means in terms of the keratocytes' ability to effectively close wounds, but obviously it raises the question of just how functional they are in Antarctic fish' says Ream. But one thing's sure, how everwell they work for the fish, these keratocytes seem set to become a staple of cytoskeletal study.
