Nrl (neural retina leucine zipper gene) encodes a retinal transcription factor that plays an essential role in rod photoreceptor differentiation and homeostasis. Dysfunction or death of rod photoreceptors precedes cone loss in many retinal and macular degenerative diseases.
In this transgenic strain, the Nrl promoter drives expression of EGFP (enhanced green fluorescent protein) specifically in rod photoreceptors and the pineal gland. In the adult retina, GFP is detected only in the outer nuclear layer, which contains rod and cone photoreceptor nuclei, and in the corresponding inner and outer segments. Immunostaining with anti-rhodopsin antibody shows complete colocalization with GFP, whereas no overlap is observed between GFP and cone-specific markers. Fluorescence is detected shortly after terminal cell division, corresponding to the timing of rod genesis. GFP-positive cells, although few and scattered, are first observed at E12 (embryonic day 12).
When combined with an Nrl knockout mutation (see Stock No. 021152), GFP-positive photoreceptors express S-opsin, consistent with the transformation of rod precursors into cones.
