- Reexpression of retinoic acid receptor (RAR) gamma or overexpression of RAR alpha or RAR beta in RAR gamma-null F9 cells reveals a partial functional redundancy between the three RAR types. Taneja, R., Bouillet, P., Boylan, J.F., Gaub, M.P., Roy, B., Gudas, L.J., Chambon, P. Proc. Natl. Acad. Sci. U.S.A. (1995)