ROD PHOTORECEPTOR-SPECIFIC GENE-EXPRESSION IN HUMAN RETINOBLASTOMA CELLS

Retinoblastoma cells in culture have previously been shown to express cone-specific genes but not their rod counterparts. We have detected t he messages for the rod alpha, beta, and gamma subunits of cGMP phosph odiesterase (PDE), the rod a subunit of transducin, rod opsin, and the cone alpha' subunit of PDE in RNA of human Y-79 retinoblastoma cells by reverse transcription-PCR. Quantitative analysis of the mRNAs for t he rod alpha and cone alpha(') PDE subunits revealed that they were ex pressed at comparable levels; however, the transcript encoding the rol l beta PDE subunit was 10 times more abundant in these cells. Northern hybridization analysis of Y-79 cell RNA confirmed the presence of the transcripts for rod and cone PDE catalytic subunits. To test whether the transcriptional machinery required for the expression of rod-speci fic genes was endogenous in Y-79 retinoblastoma cells, cultures were t ransfected with a construct containing the promoter region of the rod beta PDE subunit gene attached to the firefly luciferase reporter vect or. Significant levels of reporter enzyme activity were observed in th e cell lysates. Our results demonstrate that the Y-79 retinoblastoma c ell line is a good model system for the study of transcriptional regul ation of rod-specific genes.