Background

Variants in the mitochondrial complex I assembly factor, NUBPL are associated with a rare cause of complex I deficiency mitochondrial disease. Patients affected by complex I deficiency harboring homozygous NUBPL variants typically have neurological problems including seizures, intellectual disability, and ataxia associated with cerebellar hypoplasia. Thus far only 19 cases have been reported worldwide, and no treatment is available for this rare disease.

Methods

To investigate the pathogenesis of NUBPL-associated complex I deficiency, and for translational studies, we generated a knock-in mouse harboring a patient-specific variant Nubpl c.311T>C; p. L104P reported in three families.

Results

Similar to Nubpl global knockout mice, the Nubpl p. L104P homozygous mice are lethal at embryonic day E10.5, suggesting that the Nubpl p. L104P variant is likely a hypomorph allele. Given the recent link between Parkinson's disease and loss-of-function NUBPL variants, we also explored aging-related behaviors and immunocytochemical changes in Nubpl hemizygous mice and did not find significant behavioral and pathological changes for alpha-synuclein and oxidative stress markers .

Conclusion

Our data suggest that homozygotes with Nubpl variants, similar to the null mice, are lethal, and heterozygotes are phenotypically and neuropathologically normal. We propose that a tissue-specific knockout strategy is required to establish a mouse model of Nubpl-associated complex I deficiency disorder for future mechanistic and translational studies.