Neuritin1 Cis-Regulatory Elements Enable Gene Expression Preferentially in Retinal Ganglion Cells

Retinal ganglion cells (RGCs) are essential for visual signal transmission, yet they are vulnerable to injury and degeneration. Gene modulation in RGCs using adeno-associated virus (AAV) offers a promising avenue for neuroprotection and regeneration, but promoters lack sufficient RGC specificity, limiting the precision needed for preclinical studies. This study aims to identify novel promoter-enhancer combinations (PECs) to achieve gene expression preferentially in RGCs.

We evaluated existing transcriptomic data to identify neuritin 1 (Nrn1) as a gene with highly restricted RGC expression in the retina. Synthetic PECs derived from human and mouse Nrn1 loci were incorporated into AAV2 vectors driving expression of a nuclear-targeted reporter GreenLantern. AAVs were delivered via intravitreal injection into C57BL6/J mice, and transduction efficiency and RGC specificity were evaluated in both young and aged retinas and those subjected to intraorbital optic nerve crush (ONC), using immunohistochemistry and quantitative analysis of RBPMS+ cells.

We found that AAV2 with a human Nrn1-PEC drives gene expression in RGCs. Quantitative analysis revealed that over 83% of transduced cells were RBPMS+, indicating robust RGC selectivity and significantly outperforming ubiquitous promoters. Notably, the Nrn1-PEC retained strong and selective transgene expression in RGCs in aged mice and following ONC, demonstrating its resilience under aged and injury conditions.

The Nrn1-PEC enables efficient and injury-resilient gene expression in RGCs, addressing a key limitation in cell-specific targeting. This AAV-incorporated PEC offers a robust platform for evaluating neuroprotective interventions and accelerates the translational development of gene therapies for glaucoma and other optic neuropathies.