A comprehensive map of missense trafficking variants in rhodopsin and their response to pharmacologic correction

Metabolomics Effects of Folding Correction in Retinitis Pigmentosa Rhodopsin Mutant P23A.

The hypothesis that there is a biochemical link, most likely the UPR, between rhodopsin folding/misfolding status and metabolic homeostasis is supported and targeted metabolic modulation may offer a complementary therapeutic avenue for treating RP.

Missense variants in KATNA1 alter microtubule dynamics and underlie dominant macular dystrophy

Summary Inherited retinal diseases (IRDs) encompass a broad spectrum of genetic conditions leading to visual impairment. In this study, we identify KATNA1, encoding the catalytic p60 subunit of the microtubule-severing enzyme katanin, as a previously unrecognized cause of autosomal dominant macular dystrophy (adMD), a form of IRD. Specifically, we could ascertain the presence of 10 heterozygous missense changes affecting six conserved amino acids in 21 individuals from 16 unrelated families from various parts of the world, all presenting with non-syndromic MD of variable severity. Structure-guided analyses indicated that the identified variants potentially disrupt katanin’s assembly into hexamers or its ability to bind or hydrolyze ATP, thus compromising its microtubule-severing function. Characterization of patient-derived fibroblasts revealed accumulation of acetylated microtubules both in the cytoplasm and within the primary cilium, together with an altered subcellular distribution of KATNA1. Immunostaining of human retinal tissue showed that KATNA1 specifically localizes to photoreceptors, with distinct distribution patterns between rod and cone photoreceptors. Immunogold transmission electron microscopy confirmed this finding, revealing KATNA1 distribution along the rod axoneme and predominantly within the cone connecting cilium. Together, these results establish KATNA1 as a novel gene associated with adMD, possibly accounting for ~4% of all unresolved MD cases, and associate defective microtubule severing and cytoskeletal dysregulation with macular degeneration.

Comprehensive Mapping of SGCA Variant Effects Reveals Domain-Specific Constraints Relevant to Sarcoglycanopathies

Pathogenic variants in SGCA, encoding α-sarcoglycan, cause an autosomal recessive limb-girdle muscular dystrophy, LGMDR3/2D, yet clinical interpretation of SGCA variants remains challenging due to the high prevalence of rare missense variants. α-sarcoglycan is an essential component of the sarcoglycan complex at the muscle cell membrane, and pathogenic variants frequently impair its membrane localization. Here, we systematically assess the effects of all possible single-nucleotide variants across the SGCA coding sequence using a saturation mutagenesis-based experimental assay that quantifies α-sarcoglycan surface expression. We generate a comprehensive functional atlas that distinguishes tolerated and damaging variants, aligning with independent genetic and clinical evidence, and reveals domain-specific properties of the cytoplasmic region, in which C-terminal truncating variants retain membrane localization, suggesting possible pathogenic mechanisms beyond impaired trafficking. This work provides a scalable functional framework to support genetic diagnosis and variant interpretation in sarcoglycanopathies. Graphical Abstract Schematic overview of saturation mutagenesis-based functional mapping of SGCA.

Deep Mutational Scanning of the GPCR Rhodopsin Reveals Pleiotropic Mutational Effects and Their Roles in Modulating Light Sensitivity

Loss of RUBCN causes autophagy overdrive in a neurodevelopmental disorder with age-dependent neurodegeneration

Pathogenic variants in RUBCN, encoding the Run domain Beclin-1 interacting and cysteine-rich domain-containing protein (Rubicon) have been implicated in autosomal recessive spinocerebellar ataxia 15 (SCAR15). However, the molecular mechanisms underlying disease pathogenesis remain poorly understood. Here, we report 18 individuals from 15 unrelated families harbouring biallelic RUBCN variants, who present with an aggressive neurodevelopmental disorder variably characterized by seizures, developmental delay, intellectual disability and movement abnormalities that cause regression, progressive brain atrophy and neurodegenerative features. Through functional characterization, we demonstrate that a subset of disease-associated putative truncating variants disrupt autophagy regulation. In Caenorhabditis elegans models, loss-of-function RUBCN variants result in an increased autophagic flux and impaired neuronal function, recapitulating key features in humans. Correspondingly, cellular assays reveal that nonsense and frameshift RUBCN variants lead to defective autophagy inhibition, underscoring a crucial role for RUBCN as a key negative autophagy regulator. Molecular dynamics simulations rank the eleven missense variants by structural effect, with p.Arg813Trp alone altering the target protein at both the local and the regional level and lying within the RAB7A-binding module that the truncating alleles remove altogether. Our findings establish and expand the RUBCN-related disorders as a clinically and molecularly distinct subset of autophagy-related diseases. By delineating both the genetic landscape and cellular consequences of Rubicon dysfunction, this study enhances our understanding of autophagy-related neurodevelopmental disorders and provides a foundation for future therapeutic investigations.

Damaging RBM20 E-rich domain variants are not rescued by gene replacement