TOPOGRAPHICAL REGULATION OF CONE AND ROD OPSIN GENES - PARALLEL, POSITION-DEPENDENT LEVELS OF TRANSCRIPTION

RNase protection assays were used to follow rhodopsin and red cone ops in mRNA levels during bovine fetal development as a function of retina l position. Following induction, an equivalent radial gradient of rod and cone opsin mRNA is present in the fetal retina. This gradient is m aintained in the adult retina even though no corresponding gradient in rod or cone cell density is present. Since the mRNA expression gradie nt does not progress radially, position dependent levels of photorecep tor-specific transcription is suggested.