AUTHORS
Mukhtar Ullah, Atta Ur Rehman, Madhur Shetty, Michael D Allen, Ehsan Ullah, Sabrina G Signorini, Cyril Burin des Roziers, Rosalie M Grijalva, Abdur Rashid, Asad Munir, Alessandra Pia Porretta, Enza Maria Valente, Aime R Agather, Ioannis Dimopoulos, Robert B Hufnagel, Edouard Malandain, Juliette Coursimault, Muhammad Ansar, Stylianos E Antonarakis, Andrea Superti-Furga, Sanaullah Jan, Brian P Brooks, Giacomo Calzetti, Bin Guan, Mathieu Quinodoz, L Keith Henry, Carlo Rivolta
JAMA Ophthalmol. 2026 Jan 1;144(1):70-78. doi: 10.1001/jamaophthalmol.2025.4875.
ABSTRACT
Importance: Inherited retinal dystrophies are a group of disorders that may lead to progressive vision loss. Improved knowledge of their molecular genetics is important for accurate diagnosis or development of targeted therapies.
Objective: To identify pathogenic variants in the SLC6A6 gene (encoding TauT, the main transporter for taurine) and assess their role in the molecular pathogenesis of hereditary early-onset retinal dystrophy (EORD) in affected individuals from diverse ethnic backgrounds.
Design, setting, and participants: This was a retrospective, multicenter observational study conducted between June 2019 and March 2025, involving 7 affected and 10 unaffected individuals from 4 unrelated families recruited in Pakistan, Italy, the US, and France.
Exposure: Pathogenic variants in SLC6A6 in individuals with EORD.
Main outcomes and measures: Genetic, clinical, and functional outcomes of pathogenic variants in SLC6A6 in individuals with Leber congenital amaurosis (LCA) and EORD. All patients underwent standard clinical examinations, including visual acuity, full-field electroretinography, and multimodal retinal imaging, followed by measurement of fasting plasma taurine levels. In vitro and ex vivo taurine transport and membrane trafficking assays in human embryonic kidney (HEK)-293 cells, as well as patient-derived fibroblasts, were also performed.
Results: All 7 affected individuals exhibited LCA/EORD, with extraocular findings in some. Genetic analysis identified homozygous pathogenic SLC6A6 variants in all affected individuals, while unaffected relatives were heterozygous carriers. Families 1 and 2 carried missense variants p.(Thr249Ile) and p.(Ala294Thr), while families 3 and 4 carried truncating variants-a deletion of exon 11 and p.(Thr113Ter), respectively. Functional studies demonstrated that both missense variants are associated with complete loss of taurine transport in HEK-293 cells and patient-derived fibroblasts. Additionally, irrespective of the variants considered, plasma taurine levels in affected individuals were reduced compared with heterozygous carriers (difference between means, -31.7 µmol/L; 95% CI, -42.7 to -20.8; P < .001) and healthy control individuals (difference between means, -37.7 µmol/L; 95% CI -41.6 to -33.8; P < .001).
Conclusions and relevance: These findings confirm and expand the role of biallelic variants in SLC6A6 in association with LCA/EORD due to impaired taurine transport. These findings suggest that patients with a diagnosis of SLC6A6-related LCA/EORD may be candidates for investigational oral taurine supplementation.
PMID: 41343195 | PMCID: PMC12679424 | DOI: 10.1001/jamaophthalmol.2025.4875
