No abstract

Reduced nicotinamide adenine dinucleotide (NADH):ubiquinone oxidoreductase (complex I) is the largest complex of the mitochondrial respiratory chain and complex I deficiency accounts for approximately 30% cases of respiratory-chain deficiency in humans. Only seven mitochondrial DNA genes, but >35 nuclear genes encode complex I subunits. In an attempt to elucidate the molecular bases of complex I deficiency, we studied the six most-conserved complex I nuclear genes (NDUFV1, NDUFS8, NDUFS7, NDUFS1, NDUFA8, and NDUFB6) in a series of 36 patients with isolated complex I deficiency by denaturing high-performance liquid chromatography and by direct sequencing of the corresponding cDNA from cultured skin fibroblasts. In 3/36 patients, we identified, for the first time, five point mutations (del222, D252G, M707V, R241W, and R557X) and one large-scale deletion in the NDUFS1 gene. In addition, we found six novel NDUFV1 mutations (Y204C, C206G, E214K, IVS 8+41, A432P, and del nt 989-990) in three other patients. The six unrelated patients presented with hypotonia, ataxia, psychomotor retardation, or Leigh syndrome. These results suggest that screening for complex I nuclear gene mutations is of particular interest in patients with complex I deficiency, even when normal respiratory-chain-enzyme activities in cultured fibroblasts are observed.

Inappropriate stimulation or defective negative regulation of the type I interferon response can lead to autoinflammation. In genetically uncharacterized cases of the type I interferonopathy Aicardi-Goutières syndrome, we identified biallelic mutations in LSM11 and RNU7-1, encoding components of the replication-dependent histone pre-mRNA processing complex. Mutations were associated with the misprocessing of canonical histone transcripts, and a disturbance of linker histone stoichiometry. Additionally, we observed an altered distribution of nuclear cyclic GMP-AMP synthase (cGAS), and enhanced interferon signaling mediated by the cGAS-stimulator of interferon genes (STING) pathway in patient fibroblasts. Finally, we established that chromatin without linker histone more efficiently stimulates cGAS production in vitro. We conclude that nuclear histones, as key constituents of chromatin, are essential in suppressing the immunogenicity of self-DNA.

Primary cultures of human embryonic neurons and astrocytes have been used to test the interactions between neural cells and either human immunodeficiency virus type 1 (HIV-1) or HIV-1-infected monocytes. After direct infection with HIV-1, neither morphological alteration of neurons and astrocytes nor signs of viral replication were observed. Similarly, cultured human neurons and astrocytes were resistant to incubation with the supernatant of HIV-1-infected U937 cells, a human monoblastoid cell line. In contrast, HIV-1-infected U937 monocytic cells adhered to neural cells and induced large plaques of necrosis surrounding them. This cytopathic effect began at the time of viral replication (day 16 after infection). Its intensity depended on that of viral replication, and its range was identical to the region of diffusion of viral antigens, as judged by immunocytochemistry. The cytopathic effect was not dependent on the release of free radicals. It could not be induced by cytokines or cytokine-stimulated U937 cells. It is likely that this cytopathic effect depends on the release of viral antigens either within the site of adherence itself or within close range of the astrocyte membrane.