Expression of the Blue-Light Receptor Cryptochrome in the Human Retina

• Published in: Investigative ophthalmology & visual science Vol. 44; no. 10; pp. 4515 - 4521
• Main Authors: Thompson, Carol L, Rickman, Catherine Bowes, Shaw, Steven J, Ebright, Jessica N, Kelly, Una, Sancar, Aziz, Rickman, Dennis W
• Format: Journal Article
• Language: English
• Published: Rockville, MD ARVO 01-10-2003; Association for Research in Vision and Ophtalmology
• Subjects: Adult; Aged; Biological and medical sciences; Cryptochromes; Drosophila Proteins; Eye and associated structures. Visual pathways and centers. Vision; Eye Proteins; Female; Flavoproteins - genetics; Flavoproteins - metabolism; Flavoproteins - radiation effects; Fundamental and applied biological sciences. Psychology; Humans; Immunohistochemistry; Light; Male; Middle Aged; Photoreceptor Cells, Invertebrate; Receptors, G-Protein-Coupled; Retina - metabolism; Retinal Ganglion Cells - metabolism; Retinal Pigments - genetics; Retinal Pigments - metabolism; Retinal Pigments - radiation effects; Reverse Transcriptase Polymerase Chain Reaction; RNA, Messenger - metabolism; Subcellular Fractions; Vertebrates: nervous system and sense organs; Human; Eye; Gene CRY2; Retina; Gene CRY1; Blue light; Gene expression; In vitro; Biological receptor
• ISSN: 0146-0404; 1552-5783; 1552-5783
• DOI: 10.1167/iovs.03-0303

To analyze the patterns of expression of the cryptochromes, CRY1 and CRY2, in the human retina and to correlate expression of these putative blue-light receptors with nonvisual photoreceptor localization.
CRY1 and CRY2 mRNA expression was analyzed in 4-mm diameter punches of macula and midperipheral human retina by quantitative RT-PCR. CRY2 protein expression was examined by immunohistochemistry in cross sections of human retina, and its subcellular localization was determined by immunoblot analysis of fractionated human retinal extracts.
CRY2 mRNA was 11 times more abundant than CRY1 throughout adult human retina. CRY2 immunoreactivity was detected in most cells in the ganglion cell layer (GCL) and in a subset of cells in the inner nuclear layer (INL) in both the macula and periphery. Immunoperoxidase staining further revealed that CRY2 was localized throughout the cytoplasm of cells in the GCL as well as within nuclei. This intracellular localization of CRY2 was confirmed by immunoblot analysis of fractionated human retinal extracts.
Photopigments governing circadian photoreception have been localized to the inner retina. The relative abundance of CRY2 transcripts, coupled with CRY2 localization to the inner retina, supports a photoreceptive role for CRY2 in human retina. Furthermore, the discovery that CRY2 is also localized within the cytoplasm of some cells in the GCL, suggests it may perform a function separate from its known nuclear role in the transcriptional feedback loop underlying the molecular circadian clock.