Fine-tuning FAM161A gene augmentation therapy to restore retinal function

Area of Science:

• Ophthalmology
• Genetics
• Molecular Biology

Background:

• Gene therapy shows promise for inherited retinal diseases, but achieving physiological improvements remains challenging.
• Retinitis pigmentosa-type 28 (RP28) results from FAM161A mutations, crucial for photoreceptor connecting cilia (CC) structure.
• Loss of FAM161A function leads to CC disorganization, outer segment collapse, and vision loss.

Purpose of the Study:

• To investigate the efficacy of AAV-mediated gene replacement therapy for RP28 in Fam161a-deficient mice.
• To compare the impact of different AAV vector promoter activities, doses, and FAM161A isoforms on therapeutic outcomes.
• To determine the optimal conditions for restoring CC structure and function in RP28.

Main Methods:

• Utilized adeno-associated virus (AAV) vectors to deliver human FAM161A isoforms to Fam161a-deficient mouse models.
• Compared various promoter strengths, vector doses, and delivery of both long and short FAM161A isoforms.
• Assessed cell survival, CC structure, and retinal function following gene therapy interventions.

Main Results:

• All tested AAV vectors improved photoreceptor cell survival in the treated mice.
• Precise FAM161A expression in the CC, achieved by co-delivering both isoforms with a weak promoter (FCBR1-F0.4), significantly enhanced retinal function.
• Suboptimal vector strategies resulted in less targeted expression and limited functional recovery.

Conclusions:

• Successful gene therapy for RP28 necessitates precise regulation of therapeutic gene expression, specifically for structural proteins like FAM161A.
• Optimizing vector design, promoter selection, dosage, and delivery of relevant gene isoforms is critical for restoring CC and improving vision.
• This study highlights the importance of isoform-specific delivery and controlled expression for effective gene replacement therapies in inherited retinal diseases.