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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.

Neuropathological studies have shown that human immunodeficiency virus type 1-infected cells within the brain express several markers characteristic of macrophages and could either be microglial cells, or monocytes invading the CNS, or both. To better define the target cells of human immunodeficiency virus type 1 within the brain, we have studied human microglial cells, both in vivo and in vitro, and compared them to monocytes for their antigenic markers and their susceptibility to human immunodeficiency virus type 1 infection. Brain-derived macrophages were isolated from primary cortical and spinal cord cultures obtained from 8 to 12-week-old human embryos. The isolated cells presented esterase activity, phagocyted zymosan particles, expressed several (Fc receptors, and CD68/Ki-M7 and CD11b/CR3 receptors) of the macrophagic antigenic markers, and appeared to be resident microglial cells from human embryonic brain. Conversely, brain-derived macrophages did not express antigens CD4, CD14, or CD68/Ki-M6, which are easily detected on freshly isolated monocytes. Using these antigenic differences between isolated microglial cells and monocytes, we have observed that two populations of macrophages could be individualized. In the normal adult brain, microglial cells were numerous in both the gray and the white matter. The infrequent cells sharing antigens with monocytes were found almost exclusively around vessels. In 8 to 12-week-old human embryos, microglial cells were found in both the parenchyma and the germinative layer. Cells sharing antigens with monocytes were only found at the top of and inside the germinative layer. In brain tissue from patients with human immunodeficiency virus type 1 encephalitis, cells sharing antigens with monocytes are abundant not only around the vessels but also in the parenchyma. In double-labeling experiments, human immunodeficiency virus type 1-infected cells showed monocyte antigens. Finally, microglial cells also differ from monocytes in their in vitro susceptibility to human immunodeficiency virus type 1 infection; after stimulation by r-TNF alpha or GmCSF, monocytes but not microglial cells can replicate human immunodeficiency virus type 1. This in vitro difference in human immunodeficiency virus type 1 susceptibility between monocytes and microglial cells together with the presence of monocytic antigens within the brain tissue of human immunodeficiency virus type 1-infected patients suggest that human immunodeficiency virus type 1-infected cells within the brain are either monocytes that have crossed the blood-brain barrier and spread through the tissue or perivascular microglial cells that, after phagocyting infected blood lymphocytes, subsequently contain viral antigen and migrate to brain tissue.

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The aim of this prospective study was to investigate changes in muscle activity during gait in children with Duchenne muscular Dystrophy (DMD). Dynamic surface electromyography recordings (EMGs) of 16 children with DMD and pathological gait were compared with those of 15 control children. The activity of the rectus femoris (RF), vastus lateralis (VL), medial hamstrings (HS), tibialis anterior (TA) and gastrocnemius soleus (GAS) muscles was recorded and analysed quantitatively and qualitatively. The overall muscle activity in the children with DMD was significantly different from that of the control group. Percentage activation amplitudes of RF, HS and TA were greater throughout the gait cycle in the children with DMD and the timing of GAS activity differed from the control children. Significantly greater muscle coactivation was found in the children with DMD. There were no significant differences between sides. Since the motor command is normal in DMD, the hyper-activity and co-contractions likely compensate for gait instability and muscle weakness, however may have negative consequences on the muscles and may increase the energy cost of gait. Simple rehabilitative strategies such as targeted physical therapies may improve stability and thus the pattern of muscle activity.

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