Preprint describes high-throughput assay to validate BEST1 variants for bestrophinopathy gene therapy
Researchers have used a halide-sensitive YFP quenching assay to functionally characterise known BEST1 variants, supporting variant classification for an investigational gene therapy programme.
A preprint posted to bioRxiv from researchers working on the OPGx-BEST1 programme describes a robust, scalable cell-based assay for functionally validating variants in the Bestrophin-1 gene (BEST1). Bestrophinopathies are a heterogeneous group of inherited retinal degenerative diseases caused by pathogenic BEST1 variants; more than 250 have been reported, but only a small proportion have been functionally interrogated to confirm loss-of-function status.
The assay uses a halide-sensitive yellow fluorescent protein (YFP) reporter to measure chloride channel activity in retinal pigment epithelium (RPE) cells. Loss-of-function variants — those that impair BEST1's chloride channel activity — produce a measurable reduction in YFP quenching. OPGx-BEST1 is an investigational gene therapy designed to restore BEST1 function via augmented wild-type expression; functional evidence of loss-of-function is therefore a prerequisite for establishing which patients' variants are likely to be complemented by the approach.
The authors report that the assay reliably distinguishes pathogenic from benign variants across a tested panel, and propose it as a scalable platform for functional classification of variants of uncertain significance (VUS) — a long-standing challenge in BEST1-related disease. Because this work is a preprint, it has not yet undergone formal peer review, and the assay's performance characteristics should be considered preliminary.
Plain-language version
For patients, families, and general readers. Educational only — not medical advice.
Bestrophinopathies are a group of rare inherited eye diseases caused by faults (called variants or mutations) in a gene called BEST1, which helps cells in the back of the eye manage the flow of charged particles called chloride ions. Researchers have now described a laboratory test that can check whether a specific BEST1 fault actually stops the gene working properly — something that could not always be confirmed for many of the 250-plus known faults. This matters because a gene therapy called OPGx-BEST1 is being developed that aims to restore BEST1 function, and knowing which genetic faults it might help with is an important step. This work is a preprint, meaning it has been shared publicly but has not yet been formally checked by independent scientists.
This is an educational summary, not medical advice. If anything here raises questions for you, please speak with your GP or a clinical professional.
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Primary sourcePreprint bioRxiv (Cold Spring Harbor Laboratory) · 2026-10-24Functional Validation of Known BEST1 Variants Using a Robust Halide-Sensitive YFP Quenching Assay