Rod photoreceptor-specific gene expression in human retinoblastoma cells

Abstract

Retinoblastoma cells in culture have previously been shown to express cone-specific genes but not their rod counterparts. We have detected the messages for the rod α, β, and γ subunits of cGMP phosphodiesterase (PDE), the rod α subunit of transducin, rod opsin, and the cone α' subunit of PDE in RNA of human Y-79 retinoblastoma cells by reverse transcription-PCR. Quantitative analysis of the mRNAs for the rod α and cone α' PDE subunits revealed that they were expressed at comparable levels; however, the transcript encoding the rod β 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- specific genes was endogenous in Y-79 retinoblastoma cells, cultures were transfected with a construct containing the promoter region of the rod β PDE subunit gene attached to the firefly luciferase reporter vector. Significant levels of reporter enzyme activity were observed in the cell lysates. Our results demonstrate that the Y-79 retinoblastoma cell line is a good model system for the study of transcriptional regulation of rod-specific genes.