GENE ARRAY AND EXPRESSION OF MOUSE RETINA GUANYLATE-CYCLASE-ACTIVATING-PROTEIN-1 AND GUANYLATE-CYCLASE-ACTIVATING-PROTEIN-2

PURPOSE. To identify gene arrangement, chromosomal localization, and e xpression pattern of mouse guanylate cyclase activating proteins GCAP1 and GCAP2, retina-specific Ca2+-binding proteins, and photoreceptor g uanylate cyclase activators. METHODS. The GCAP1 and GCAP2 gents were c loned from genomic libraries and sequenced. The chromosomal localizati on of the GCAP array was determined using fluorescent in situ hybridiz ation. The expression of GCAP1 and GCAP2 in mouse retinal tissue was d etermined by immunocytochemistry. RESULTS. In this study, the mouse GC AP1 and GCAP2 gene array, its chromosomal localization, RNA transcript s, and immunolocalization of the gene products were fully characterize d. The GCAP tail-to-tail array is located at the D band of chromosome 17. Each gene is transcribed into a single transcript of 0.8 kb (GCAP1 ) aid 2 kb (GCAP2). Immunocytochemistry showed that both GCAP genes ar e expressed in retinal photoreceptor cells, but GCAP2 was nearly undet ectable in cones. GCAP2 was also found in amacrine and ganglion cells of the inner retina. Light-adapted and dark-adapted retinas showed no significant difference in the distribution of the most intense GCAP2 s taining within the outer segment and outer plexiform layers. CONCLUSIO NS. Identical GCAP gene structures and the existence of the tail-to-ta il gene array in mouse and human suggest an ancient gene duplication-i nversion event preceding mammalian diversification. Identification of both GCAPs in synaptic regions, and of GCAP2 in the inner retina sugge st roles of these Ca-binding proteins in addition to regulation of pho totransduction.