Crystallin genes: lens specificity of the murine alpha A-crystallin gene

The abundant soluble proteins of the eye lens, the crystallins, are encoded by several gene families which are developmentally regulated in the embryonic lens. We have studied the expression of the murine alpha A-crystallin gene. Transfection experiments using the pSVO-CAT vector and explanted lens epithelia from embryonic chickens demonstrated proximal (-88 to -60) and distal (-111 to -85) regulatory sequences which interact when the alpha A-crystallin promoter is activated in the lens cells. Transgenic mouse experiments showed that the sequence between positions -366 to +46 of the alpha A-crystallin promoter can drive foreign genes selectively in the lens. A fusion gene consisting of this alpha A-crystallin promoter sequence and the T-antigen gene of SV40 produced a lens tumor in transgenic mice. Thus, crystallin promoters provide a useful model for tissue-specific gene expression and permit targeting the expression of foreign genes to a highly differentiated tissue during development.