The AP2 proteins are normally expressed in ectodermally derived vertebrate tissues where they are necessary for normal growth and development. The factors have also been implicated in the control of cell proliferation, viral transformation, and oncogenesis. AP2 seems to play in important role in human breast cancer. AP2 alpha is the only AP2 protein required for early morphogenesis of the lens vesicle. AP2 beta appears to be required for normal face and limb development and for proper terminal differentiation and function of renal tubular epithelia.