Fine-tuning FAM161A gene augmentation therapy to restore retinal function

Abstract

In 15 years, inherited retinal diseases have seen gene therapy as a springboard to hope. Many preclinical investigations focused on vectors with maximal gene expression capabilities. But despite an efficient gene transfer, little physiological improvement was noted for certain ciliopathies. FAM161A is an essential protein for the structure of photoreceptor connecting cilium (CC). In the absence of FAM161A, cilia disorganize resulting in outersegment collapses and vision impairment. Within the human retina, FAM161A produces two isoforms: the long with exon 4, and the short, lacking it. To restore CC in Fam161a-deficient mice, we compared AAV vectors with different promoter activities, doses, and human isoforms injected subretinally in 14-days Fam161atm1b/tm1b mice, shortly after the onset of cilium disorganization. All vectors improved cell survival, but only combining both isoforms using the weak FCBR1-F0.4 promoter allowed precise FAM161A expression in the CC and enhanced retinal function. Our study on FAM161A gene replacement for RP28, a rod-cone-related disease, underscores the critical need for precise therapeutic gene regulation, appropriate vector dosing and delivery of both isoforms. Fine tuning of therapeutic gene expression, tailored to disease traits, is crucial for restoring retinal function. This precision is pivotal for secure gene therapy involving structural proteins like FAM161A.