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

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.