Omar A. Mahroo

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 dystr...

Background/Objective: Retinal involvement in autoimmune polyendocrine syndrome type 1 (APS1), a rare monogenic autoimmune disorder caused by mutations in the AIRE gene, is increasingly recognised but remains poorly defined. Prior reports suggest a variable phenotype, ranging from mild changes to severe vision loss, often presumed untreatable. We explored the range of retinal phenotypes associated with AIRE gene deficiency in a multicentre case series of patients with APS1. Methods: We performed a retrospective case note review of patients with molecularly confirmed APS1 from tertiary ophthalmic centres. Clinical history, multimodal retinal imaging, electrophysiology, genetic data, and treatment regimens were analysed. Histopathology was available in one case postmortem. Results: Records were reviewed from five unrelated female patients. Median age was 14 years at onset of ocular involvement and 33 years at most recent follow up. Some findings from two cases have been previously reported. Three distinct pathogenic AIRE variants contributing to biallelic genotypes were observed. Retinal findings ranged from structurally and functionally normal to advanced degeneration. One patient demonstrated sharp zonal atrophy on histopathology. Inflammatory features predominated in two cases, both showing durable vision preservation with periocular or systemic immunomodulation. One patient demonstrated four years of disease stabilisation with rituximab. No consistent genotype-phenotype correlation emerged. Conclusion: AIRE -associated retinopathy encompasses a diverse spectrum, from clinically silent to profound degeneration. Early, targeted immunomodulation might preserve vision in selected cases. These findings advocate for ophthalmic surveillance in APS1, and support further investigation into predictive biomarkers and possible tailored immunotherapy in this vision-threatening autoimmune disorder.

Small nuclear RNAs (snRNAs) combine with specific proteins to generate small nuclear ribonucleoproteins (snRNPs), the building blocks of the spliceosome. U4 snRNA forms a duplex with U6 and, together with U5, contributes to the tri-snRNP spliceosomal complex. Variants in RNU4-2, which encodes U4, have recently been implicated in neurodevelopmental disorders. Here we show that heterozygous inherited and de novo variants in RNU4-2 and in four RNU6 paralogs (RNU6-1, RNU6-2, RNU6-8 and RNU6-9), which encode U6, recur in individuals with nonsyndromic retinitis pigmentosa (RP), a genetic disorder causing progressive blindness. These variants cluster within the three-way junction of the U4/U6 duplex, a site that interacts with tri-snRNP splicing factors also known to cause RP (PRPF3, PRPF8, PRPF31), and seem to affect snRNP biogenesis. Based on our cohort, deleterious variants in RNU4-2 and RNU6 paralogs may explain up to ~1.4% of otherwise undiagnosed RP cases. This study highlights the contribution of noncoding RNA genes to Mendelian disease and reveals pleiotropy in RNU4-2, where distinct variants underlie neurodevelopmental disorder and retinal degeneration.

Glaucoma is a major cause of blindness globally and its prevalence rises with age. This study explored systemic blood-derived DNA methylation epigenetic biomarkers for association with glaucoma and intraocular pressure (IOP). Blood-derived DNA methylation (DNAm) was analyzed in 1,201 European participants from the Canadian Longitudinal Study on Aging (CLSA; Illumina EPIC v1 array) and 843 European participants from TwinsUK (450k array). An Epigenome-Wide Association Study (EWAS) for glaucoma and IOP was conducted, adjusting for age, sex, tobacco smoking, and leukocyte cell types. DNAm-based EpiScores estimates for 108 plasma protein levels were evaluated for associations with glaucoma and IOP. Additionally, 'biological' age acceleration, estimated using five established DNAm 'clocks,' was assessed for glaucoma and IOP and replicated in The Health and Retirement Study (HRS; n = 3,453). EWAS analyses of glaucoma and IOP in individual cohorts did not identify genome-wide significant associations. However, a combined EWAS for overlapping probes in both cohorts identified two epigenome-wide significant CpGs: cg03498697 in the FRMD3 promoter (p = 6.86x10^-8) and cg06044751 intronically within PALLD (p = 1.76x10^-7). EpiScore analysis revealed one IOP Bonferroni-significant association with TNFRSF1B levels in the meta-analysis of both cohorts (p = 1.31x10^-4). DNAm 'clock' analysis in the HRS identified a GrimAge-positive age acceleration associated with glaucoma (p = 0.01). This study identified significant epigenetic blood-derived biomarkers that are associated with glaucoma and IOP. These findings warrant replication in larger and more diverse populations as well as via longitudinal analysis to assess their robustness and potential predictive power.

Pathogenic variants in TUBB4B, which encodes the β-tubulin 4B isotype of microtubule subunits, have been associated with Leber congenital amaurosis with early-onset deafness (LCAEOD), an autosomal dominant condition characterized by early and severe loss of photoreceptor and cochlear cells. The majority of reported cases feature early disease onset and are caused by missense mutations in the R390/R391 hotspot. Multimodal evaluation included ultra-widefield pseudocolor and autofluorescence fundus photography, spectral-domain optical coherence tomography, full-field electroretinography, Goldmann kinetic perimetry, audiography, and genetic testing with next-generation sequencing. We report seven individuals from three unrelated families affected by cone-rod dystrophy and sensorineural hearing loss associated with a novel variant in TUBB4B (c.784C > T, p.R262W). Cone-rod dystrophy associated with this variant generally features a later age of onset compared to the Leber congenital amaurosis caused by variants in the canonical hotspot. This report expands the mutation spectrum and phenotypic range of TUBB4B-associated retinopathies beyond the R390/R391 hotspot and may offer insight into the pathogenesis of this rare tubulinopathy.