VISUAL PIGMENT GENE STRUCTURE AND EXPRESSION IN HUMAN RETINAE

We determined the genotypes of the X-chromosome-linked red/green color vision genes by a novel PCR/SSCP-based method and assessed expression by mRNA analysis in retinae of 51 unselected post mortem eye specimen s from Caucasian males of unknown color vision status, All individuals had a single red (long-wave) pigment gene and one or more (an average of two) green (middle-wave) pigment genes, Four males had 5'green-red 3' hybrid genes in addition to normal red and green pigment genes, The se findings are consistent with earlier studies on human visual pigmen t gene structure using Southern blotting and with a recent study using pulsed-field electrophoresis. We interpret claims of much larger numb ers of red, green and green-red hybrid genes to be technical artifacts , The ratio of expressed red to green pigment retinal mRNA varied wide ly (1-10 with a mode of 4) and was not correlated with that of red to green pigment genes, In one individual with a green-red hybrid gene in addition to normal red and green pigment genes, the normal red pigmen t gene and the hybrid gene were both expressed, but the normal green g ene was not, This person presumably had deuteranomalous color vision, Two with green-red hybrid genes expressed the normal red and green pig ment genes, but not the hybrid genes, These two individuals presumably had normal color vision, We interpret the failure to express their gr een-red hybrid genes to be caused by their location at a more distal p osition in the visual pigment gene array.