The effects of complex I deficiency on neurogenesis and white matter development in a mouse model of Leigh Syndrome (LS)

Abstract

Leigh syndrome (LS) is one of the most prevalent inherited mitochondrial disorders in pediatric population, typically presenting in early childhood with psychomotor regression and progressive neurological decline. Current understanding suggests that pathogenic variants affecting mitochondrial respiratory-chain complexes impair oxidative phosphorylation (OXPHOS), leading to bioenergetic failure in vulnerable brain regions resulting in the characteristic bilateral, symmetric deep gray matter lesions observed on MRI. While this neuron-centric perspective helps explain regional vulnerability in LS, it overlooks the substantial mitochondrial demand of neural stem/progenitor cells (NSCs), which generate the majority of the brain cells during the embryonic and early postnatal periods. However, the in vivo consequences of sustained mitochondrial dysfunction during early neurogenesis remain poorly characterized. We leveraged the NDUFS4 knockout (KO) mouse, a well-established model of Complex I (CI) deficiency that recapitulates key clinical and neuropathological features of LS, to test whether sustained CI loss during early development disrupts NSC proliferation and lineage progression and secondarily impairs white matter maturation. Gross neuroanatomical analysis revealed reduced brain weight and decreased hemispheric width. Immunohistochemistry showed an early reduction at postnatal day 14 (P14) in NSC and neuroblast populations within the SVZ, with the neurogenic defect progressing at later timepoints to impaired lineage advancement. To resolve cell type–specific effects of CI deficiency, single-cell RNA sequencing (scRNA-seq) was conducted on the SVZ, which revealed a proliferation deficit in NSCs and intermediate progenitors. This finding was independently validated using neurosphere assays. Transcriptional programs and pathways linked to neurogenesis and oligodendrogenesis were significantly downregulated in KO neural progenitors. Although abundance of oligodendrocyte progenitors in the SVZ was not significantly altered, early and late myelin gene/protein expression was reduced, accompanied by decreased corpus callosum thickness. Together, these early neurodevelopmental defects in neurogenesis and callosal growth offer a potential mechanistic explanation for the developmental delays observed in LS. This work encourages future research into neurogenesis in other primary mitochondrial disorders and neurodegenerative disorders, especially those where developmental delays are a key feature.