Pathogenic variants in NUP214 cause “plugged” nuclear pore channels and acute febrile encephalopathy

nitzan Biran ¹ Boris Fichtman ¹ Tamar Harel ² Fadia Zagairy ¹ Carolyn D. Applegate ^3,4 Yuval Salzberg ¹ Tal Gilboa ⁵ Somaya Salah ² Avraham Shaag ^2,6 Natalia Simanovsky ⁷ Giuseppe Punzi ⁸ Ciro Leonardo Pierri ⁸ Ada Hamosh ^3,4 Orly Elpeleg ^2,6 Simon Edvardson ^5,6 Amnon Harel ¹

¹Azrieli Faculty of Medicine, Bar-Ilan University, Israel
²Department of Genetic and Metabolic Diseases, Hadassah-Hebrew University Medical Center, Israel
³Mckusick-Nathans Institute of Genetic Medicine, Department of Pediatrics, Johns Hopkins University School of Medicine, USA
⁴Baylor-Hopkins Center for Mendelian Genomics, Johns Hopkins University School of Medicine, USA
⁵Pediatric Neurology Unit, Hadassah-Hebrew University Medical Center, Israel
⁶Monique and Jacques Roboh Department of Genetic Research, Hadassah-Hebrew University Medical Center, Israel
⁷Department of Medical Imaging, Hadassah Medical Center, Israel
⁸Laboratory of Biochemistry, Molecular and Computational Biology; Department of Biosciences, Biotechnologies and Biopharmaceutics, University of Bari, Italy

The cytoplasmic side of the nuclear pore complex (NPC) is characterized by distinct architectural features, such as the cytoplasmic ring and filaments, and by a subset of asymmetrically localized nucleoporins. Nup214, localized to the base of the cytoplasmic filaments, plays a key role in nuclear protein and mRNA export. Here, we identify a rare neurodegenerative disease linked to a missense mutation in the human Nup214 gene. Clinical symptoms include intractable epilepsy, movement disorder and mental retardation and brain imaging was noted for cerebellar atrophy and abnormal signals over the basal ganglia and brain stem.

The analysis of primary fibroblasts derived from a patient revealed Nup214 and Nup88 protein levels are reduced, while the total number and density of NPCs is unaltered. Functional assays point to a delay in classical NLS-mediated import and to an accumulation of mRNA in patient cell nuclei when the export machinery is overloaded by transfection with a pEGFP plasmid. A comparison of control and patient-derived fibroblasts demonstrates changes in the response to heat shock stress, including a dramatic surge in apoptosis in patient cells. Scanning electron microscopy shows a large increase in the presence of central particles in the pore channel of patient NPCs. This suggests that large transport cargoes may be delayed in passage through the NPC channel. We hypothesize that cells in the hardest hit tissues (e.g., neurons in the central nervous system) may be irreversibly damaged by such perturbations in nuclear transport pathways.