The NRL (neural retina leucine zipper) gene encodes a basic motif-leucine zipper (bZIP) transcription factor of the Maf subfamily, which plays a critical role in the development and function of photoreceptor cells, particularly rods, in the mammalian retina. Gene expression of NRL is highly specific to the retina, appearing in postmitotic neuronal cells during embryonic development and maintaining high levels in mature neural retina. It functions as a master regulator of rod photoreceptor cell fate, working in conjunction with other transcription factors like CRX and NR2E3 to activate rod-specific genes (e.g., rhodopsin) and repress cone-specific genes. Cellular tissues predominantly labeled by NRL include rod photoreceptor nuclei, with some labeling also observed in rod and cone inner segments, somata, and synapses, and weak labeling in the cytoplasm of scattered cells in the inner nuclear and ganglion cell layers. Mutations in the NRL gene are associated with various inherited retinal degenerative diseases, most notably Retinitis Pigmentosa (RP), which can manifest as autosomal dominant (Retinitis Pigmentosa 27) or autosomal recessive forms (clumped pigmentary retinal degeneration, resembling Enhanced S-cone Syndrome), leading to progressive loss of vision ^[1-3].

The B6-hNRL mouse is a humanized model, constructed by replacing the sequences from 5'UTR to 3'UTR of the endogenous mouse Nrl gene with the corresponding human NRL gene sequence. B6-hNRL mice can be used for research into the pathogenesis of various inherited retinal degenerative diseases such as Retinitis Pigmentosa (RP). They are also useful for the screening, development, and safety evaluation of NRL-targeted drugs.