Fine-tuning FAM161A gene augmentation therapy to restore retinal function

• Published in: EMBO molecular medicine Vol. 16; no. 4; pp. 805 - 822
• Main Authors: Arsenijevic, Yvan, Chang, Ning, Mercey, Olivier, El Fersioui, Younes, Koskiniemi-Kuendig, Hanna, Joubert, Caroline, Bemelmans, Alexis-Pierre, Rivolta, Carlo, Banin, Eyal, Sharon, Dror, Guichard, Paul, Hamel, Virginie, Kostic, Corinne
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 15.04.2024; Springer Nature
• Subjects: Animals; Biomedical and Life Sciences; Biomedicine; Ciliopathy; EMBO16; Exons; Eye Proteins - chemistry; Eye Proteins - genetics; Eye Proteins - metabolism; Gene Therapy; Genetic Therapy; Humans; Mice; Molecular Medicine; Promoter Activity; Protein Isoforms - genetics; Protein Isoforms - metabolism; Retina - metabolism; Retinal Degeneration; Retinitis Pigmentosa - genetics; Retinitis Pigmentosa - metabolism; Retinitis Pigmentosa - therapy; Promoter Activity; Ciliopathy; Retinal Degeneration; Gene Therapy
• ISSN: 1757-4684; 1757-4676; 1757-4684
• DOI: 10.1038/s44321-024-00053-x

For 15 years, gene therapy has been viewed as a beacon of hope for inherited retinal diseases. Many preclinical investigations have centered around vectors with maximal gene expression capabilities, yet despite efficient gene transfer, minimal physiological improvements have been observed in various ciliopathies. Retinitis pigmentosa-type 28 (RP28) is the consequence of bi-allelic null mutations in the FAM161A, an essential protein for the structure of the photoreceptor connecting cilium (CC). In its absence, cilia become disorganized, leading to outer segment collapses and vision impairment. Within the human retina, FAM161A has two isoforms: the long one with exon 4, and the short one without it. To restore CC in Fam161a -deficient mice shortly after the onset of cilium disorganization, we compared AAV vectors with varying promoter activities, doses, and human isoforms. While all vectors improved cell survival, only the combination of both isoforms using the weak FCBR1-F0.4 promoter enabled precise FAM161A expression in the CC and enhanced retinal function. Our investigation into FAM161A gene replacement for RP28 emphasizes the importance of precise therapeutic gene regulation, appropriate vector dosing, and delivery of both isoforms. This precision is pivotal for secure gene therapy involving structural proteins like FAM161A. Synopsis AAV gene therapy for retinitis pigmentosa-28 was evaluated in the Fam161a tmb/tmb knockout mice. Accurate transgene regulation, high dose, and co-administration of two vectors encoding for the two isoforms present in the human retina are required to improve both retina structure and function. FAM161A protein expression in the entire photoreceptor cell body is induced by gene delivery of human FAM161A with IRBP-GRK1 promoter-derived AAV vectors. Despite efficient gene transfer, only photoreceptor survival is promoted by IRBP-GRK1 promoter-derived AAV vector but not retina function. Precise expression of FAM161A in the photoreceptor connecting cilium is restored after gene delivery with AAV bearing the FCBR1-F0.4 regulatory regions derived from the human FAM161A gene. Retina survival and functional improvement of Fam161a tmb/tmb knockout mice are enabled by co-administration of both long and short human FAM161A isoforms with FCBR1-F0.4 promoter-derived AAV vectors. AAV gene therapy for retinitis pigmentosa-28 was evaluated in the Fam161a tmb/tmb knockout mice. Accurate transgene regulation, high dose, and co-administration of two vectors encoding for the two isoforms present in the human retina are required to improve both retina structure and function.