Biallelic NDUFA13 variants lead to a neurodevelopmental phenotype with gradual neurological impairment

Abstract

Abstract Biallelic variants in NADH-ubiquinone oxidoreductase 1 alpha subcomplex 13 (NDUFA13) have been linked to mitochondrial complex I deficiency, nuclear type 28, based on three affected individuals from two families. With only two families reported, the clinical and molecular spectrum of NDUFA13-related diseases remains unclear. We report 10 additional affected individuals from nine independent families, identifying four missense variants (including recurrent c.170G>A) and three ultra-rare or novel predicted loss-of-function biallelic variants. Updated clinical-radiological data from previously reported families and a literature review compiling clinical features of all reported patients with isolated complex I deficiency caused by 43 genes encoding complex I subunits and assembly factors are also provided. Our cohort (mean age 7.8 ± 5.4 years; range 2.5–18) predominantly presented a moderate-to-severe neurodevelopmental syndrome with oculomotor abnormalities (84%), spasticity/hypertonia (83%), hypotonia (69%), cerebellar ataxia (66%), movement disorders (58%), and epilepsy (46%). Neuroimaging revealed bilateral symmetric T2 hyperintense substantia nigra lesions (91.6%) and optic nerve atrophy (66.6%). Protein modeling suggests missense variants destabilize a critical junction between the hydrophilic and membrane arms of complex I. Fibroblasts from two patients showed reduced complex I activity and compensatory complex IV activity increase. This study characterizes NDUFA13-related disease in 13 individuals, highlighting genotype-phenotype correlations.