Mutations affecting cell competition and growth. N. Zhuo , D.M. Tyler , S. Joglekar , R. Sultan , N.E. Baker. Molecular Genetics, Albert Einstein Col of Med, Bronx, NY.

   In animals mosaic for cells of intrinsically different growth rates, slow-growing cells will be out-competed by their faster neighbors and eliminated from the organism. Comparison of growth rates shows that the slower cells are actively retarded by the presence of faster-growing neighbors. This phenomenon is termed cell competition. Cell competition reflects a homeostatic mechanism to preserve body sizes and proportions from changes in growth rates. The molecular mechanisms of cell competition are unknown, as are the genes involved in it. We performed genetic screens for mutations permitting survival of clones of cells that should be eliminated by competition. We isolated 18 novel mutations that now survive cell competition. In another F1 mosaic screen in the eye, we isolated 10 X-linked mutations that enhance the growth rate of cells. We are now focusing on identifying the genes and investigating their roles in cell competition.