- The chicken beta/epsilon-globin enhancer directs autonomously regulated, high-level expression of the chicken epsilon-globin gene in transgenic mice. Foley, K.P., Pruzina, S., Winick, J.D., Engel, J.D., Grosveld, F., Fraser, P. Proc. Natl. Acad. Sci. U.S.A. (1994)