Fatal breathing dysfunction in a mouse model of Leigh syndrome

Abstract

Leigh syndrome (LS) is a subacute necrotizing encephalomyelopathy with gliosis in several brain regions that usually results in infantile death. Loss of murine Ndufs4, which encodes NADH dehydrogenase (ubiquinone) iron-sulfur protein 4, results in compromised activity of mitochondrial complex I as well as progressive neurodegenerative and behavioral changes that resemble LS. Here, we report the development of breathing abnormalities in a murine model of LS. Magnetic resonance imaging revealed hyperintense bilateral lesions in the dorsal brain stem vestibular nucleus (VN) and cerebellum of severely affected mice. The mutant mice manifested a progressive increase in apnea and had aberrant responses to hypoxia. Electrophysiological recordings within the ventral brain stem pre-Bötzinger respiratory complex were also abnormal. Selective inactivation of Ndufs4 in the VN, one of the principle sites of gliosis, also led to breathing abnormalities and premature death. Conversely, Ndufs4 restoration in the VN corrected breathing deficits and prolonged the life span of knockout mice. These data demonstrate that mitochondrial dysfunction within the VN results in aberrant regulation of respiration and contributes to the lethality of Ndufs4-knockout mice.

Succination is Increased on Select Proteins in the Brainstem of the NADH dehydrogenase (ubiquinone) Fe-S protein 4 (Ndufs4) Knockout Mouse, a Model of Leigh Syndrome

“…These mice show remarkable similarities to the human disease, with symptoms that include ataxia, seizures, dystonia, and respiratory failure (28). Histologically, the brain of the Ndufs4 mouse shows changes that include decreased neuronal numbers, astrocyte and microglial proliferation (28,47), and the accumulation of lipid droplets in both astrocytes and microglia (48). Strikingly, we observed clear increases in …”

“…The most pathologically affected regions of the brain in Ndufs4 KO mice include the vestibular nuclei (VN), the inferior olive/gigantocellular reticular nucleus (IO/Gi) of the BS, and the deep cerebellar fastigial nucleus (FN) (28,47). To test if protein succination was specifically increased in these areas of the brain, we obtained micropunches of VN, IO/Gi, and FN from 400 m brain slices; we also included micropunches from the typically unaffected crus 1 ansiform lobule (Crus 1) of the cerebellum as negative control.…”

“…We then narrowed our focus based on the observations in the VN, considering that these nuclei are involved in respiratory control and knowing that the Ndufs4 KO mice commonly die because of respiratory failure (47). We again used isoelectric focusing (pI 4 -7) followed by 2D SDS-PAGE separation to better examine the succinated proteins in the VN of Ndufs4 KO mice.…”

The Role of Mitochondrially Derived ATP in Synaptic Vesicle Recycling

“…The NDUFS4 protein, NADH dehydrogenase (ubiquinone) iron-sulfur protein 4, is an essential subunit of mitochondrial complex I. Deleting this gene produces devastating neurologic consequences in humans (44) and mice (19,45) and severely impairs respiration in mesencephalic neurons (46). However, cultured dopaminergic neurons that lack NDUFS4 due to Cre-mediated gene inactivation have normal survival (46,47).…”

Mitochondrial disorders: aetiologies, models systems, and candidate therapies

“…The exploitation of endogenous import mechanisms will likely provide strategies that target sufficient proportions of intracellular mitochondria to elicit readily quantifiable and potentially beneficial effects. Murine model for Leigh syndrome Gene replacement NDUFS4 AAV2/1 stereotactic injection in mediolateral vestibular nucleus [105] Murine model for ethylmalonic encephalopathy Gene replacement to liver ETHE1 AAV2/8-mediated gene transfer to liver [75] Harlequin mice with complex I deficiency-related neurodegeneration Gene replacement AIF1 AAV2/2 intravitreal injection followed by electroporation [106] Two murine models for LHON Allotopic gene replacement ND4 AAV2/2 and electroporation in vitreous [53,54] MTPT model for PD Trans-kingdom gene replacement Candidate gene therapies for mitochondrial disorders Nucleotide delivery methodologies, together with methods to optimise protein import into mitochondria, are being used to explore candidate therapies for mitochondrial deficiency disorders ( Table 2). Most of the mitochondrial proteome (comprising approximately 1500 polypeptides)…”