Evolution of allorecognition in a basal chordate

University Of California-Santa Barbara, Santa Barbara CA

Investigators

Abstract

The ability of an individual to discriminate between self and non/self is called allorecognition, and is found throughout the animal kingdom. This immunological recognition process is controlled by incredibly diverse molecules, and individual animals have nearly unique combinations of these, essentially making an individual signature. The best example of this is tissue transplantation: successful transplantation depends on a match of these signatures between donor and recipient, or the tissue will be rejected as being foreign. The molecules responsible are also thought to control other processes, for example the ability to determine the relatedness of another individual. What is not understood is how these molecules can be so varied: the observed diversity is 10 to 100-fold higher than what evolutionary mathematical models predict. Equally important is how this diversity is recognized and acted upon. This proposal focuses on understanding the evolutionary forces which underlie the ability to create, maintain and respond to this genetic diversity. Botryllus schlosseri, is a marine animal whose well studied allorecognition reaction occurs rapidly and can be easily studied. The investigators have recently identified the molecules which underlie this process. Given its convenient life-history traits, coupled with results from other investigators, the investigators can now begin to characterize the events involved with creating and maintaining this genetic diversity of this organism. This includes describing the diversity within and among natural populations, which will lead to a clearer understanding of the evolutionary processes responsible. B. schlosseri also has behavioral responses thought to be controlled by these molecules, which will also be directly tested. The basic appeal of these studies and the straightforward methodology attract numerous undergraduate and high school students (many from under-represented groups), and is incorporated into independent research projects every spring and summer.