BLUE CONES AND CONE BIPOLAR CELLS SHARE TRANSCRIPTIONAL SPECIFICITY AS DETERMINED BY EXPRESSION OF HUMAN BLUE VISUAL PIGMENT-DERIVED TRANSGENES

Sequences 5' of the human blue visual pigment gene have been assayed i n transgenic mice for their ability to direct cell-type-specific expre ssion of linked beta-galactosidase (lacZ) and placental alkaline phosp hatase (P ALP1) reporters. Constructs containing either 5.4 kilobases (kb) or 0.47 kb of 5' flanking DNA direct expression exclusively to th e retina. Within the retina, transgene expression is confined to blue cones and cone bipolar cells, as determined, respectively, by double l abeling with anti-cone pigment antibodies and by morphologic analyses. These results imply that blue cones and cone bipolar cells have parti ally overlapping transcriptional specificities.