Characterization of an Otx2 Retinal Enhancer, Poster 48

Cone photoreceptors are crucial to daylight and color vision, and loss permanently impairs sight. Regenerative therapies targeting cones may help to restore vision after photoreceptor damage by disease or injury. Improved... [ view full abstract ]

Cone photoreceptors are crucial to daylight and color vision, and loss permanently impairs sight. Regenerative therapies targeting cones may help to restore vision after photoreceptor damage by disease or injury. Improved understanding of in vivo cone genesis may facilitate development of such therapies. The transcription factor Otx2 is required for the development of photoreceptor and bipolar cells, however, the mechanisms by which Otx2 is activated during cone genesis are still unknown. Three enhancer regions involved in Otx2 transcriptional activation have been characterized, including ECR4, a possible initiator element. In order to identify the minimum sequence required for Otx2 expression, ECR4 was divided into fragments to be analyzed for enhancer activity. The fragments were cloned into reporter plasmids and evaluated for activity in P0 mouse retinal explants by IHC. The 5' and center constructs recapitulated wild type Otx2 expression while the 3' construct failed to express Otx2. Sequence overlap across the active constructs initially identified a 268bp fragment as necessary for enhancer activity. Data from another construct further established a 65bp region as the active region. Additional constructs have been designed to more specifically characterize this enhancer region in future experiments.