The gene product Murr1 restricts HIV-1 replication in resting CD4+ lymphocytes

Although human immunodeficiency virus-1 (HIV-1) infects quiescent and proliferating CD4+ lymphocytes, the virus replicates poorly in resting T cells. Factors that block viral replication in these cells might help to prolong the asymptomatic phase of HIV infection; however, the molecular mechanisms that control this process are not fully understood. Here we show that Murr1, a gene product known previously for its involvement in copper regulation, inhibits HIV-1 growth in unstimulated CD4+ T cells. This inhibition was mediated in part through its ability to inhibit basal and cytokine-stimulated nuclear factor (NF)-kappaB activity. Knockdown of Murr1 increased NF-kappaB activity and decreased IkappaB-alpha concentrations by facilitating phospho-IkappaB-alpha degradation by the proteasome. Murr1 was detected in CD4+ T cells, and RNA-mediated interference of Murr1 in primary resting CD4+ lymphocytes increased HIV-1 replication. Through its effects on the proteasome, Murr1 acts as a genetic restriction factor that inhibits HIV-1 replication in lymphocytes, which could contribute to the regulation of asymptomatic HIV infection and the progression of AIDS.     

Accelerated vaccination for Ebola virus haemorrhagic fever in non-human primates

Containment of highly lethal Ebola virus outbreaks poses a serious public health challenge. Although an experimental vaccine has successfully protected non-human primates against disease, more than six months was required to complete the immunizations, making it impractical to limit an acute epidemic. Here, we report the development of accelerated vaccination against Ebola virus in non-human primates. The antibody response to immunization with an adenoviral (ADV) vector encoding the Ebola glycoprotein (GP) was induced more rapidly than with DNA priming and ADV boosting, but it was of lower magnitude. To determine whether this earlier immune response could nonetheless protect against disease, cynomolgus macaques were challenged with Ebola virus after vaccination with ADV-GP and nucleoprotein (NP) vectors. Protection was highly effective and correlated with the generation of Ebola-specific CD8(+) T-cell and antibody responses. Even when animals were immunized once with ADV-GP/NP and challenged 28 days later, they remained resistant to challenge with either low or high doses of virus. This accelerated vaccine provides an intervention that may help to limit the epidemic spread of Ebola, and is applicable to other viruses.     

Adrenergic neuroplasticity is maintained in the nutritional rehabilitated adult rat

Summary This work examined the capacity of intact catecholaminergic axons to grow, in response to lesions, in the brain of adult rats following nutritional rehabilitation. The partially deafferented epithalamic habenula was used as a model to study neuronal plasticity. Noradrenergic neurons appear to maintain their plasticity in rats recovered from their postnatal undernutrition.Supported by a BRSG-UTMSH grant.Supported by a NIH grant.Acknowledgments. Thanks are due to Mrs Malka Gottesfeld for her invaluable assistance.     

Combined activation of Ras and Akt in neural progenitors induces glioblastoma formation in mice

Gliomas are the most common primary malignant brain tumours and are classified into four clinical grades, with the most aggressive tumours being grade 4 astrocytomas (also known as glioblastoma multiforme; GBM). Frequent genetic alterations in GBMs (refs 2-5) result in stimulation of common signal transduction pathways involving Ras, Akt and other proteins. It is not known which of these pathways, if any, are sufficient to induce GBM formation. Here we transfer, in a tissue-specific manner, genes encoding activated forms of Ras and Akt to astrocytes and neural progenitors in mice. We found that although neither activated Ras nor Akt alone is sufficient to induce GBM formation, the combination of activated Ras and Akt induces high-grade gliomas with the histological features of human GBMs. These tumours appear to arise after gene transfer to neural progenitors, but not after transfer to differentiated astrocytes. Increased activity of RAS is found in many human GBMs (ref. 11), and we show here that Akt activity is increased in most of these tumours, implying that combined activation of these two pathways accurately models the biology of this disease.     

Hotspots of aberrant epigenomic reprogramming in human induced pluripotent stem cells

Induced pluripotent stem cells (iPSCs) offer immense potential for regenerative medicine and studies of disease and development. Somatic cell reprogramming involves epigenomic reconfiguration, conferring iPSCs with characteristics similar to embryonic stem (ES) cells. However, it remains unknown how complete the reestablishment of ES-cell-like DNA methylation patterns is throughout the genome. Here we report the first whole-genome profiles of DNA methylation at single-base resolution in five human iPSC lines, along with methylomes of ES cells, somatic cells, and differentiated iPSCs and ES cells. iPSCs show significant reprogramming variability, including somatic memory and aberrant reprogramming of DNA methylation. iPSCs share megabase-scale differentially methylated regions proximal to centromeres and telomeres that display incomplete reprogramming of non-CG methylation, and differences in CG methylation and histone modifications. Lastly, differentiation of iPSCs into trophoblast cells revealed that errors in reprogramming CG methylation are transmitted at a high frequency, providing an iPSC reprogramming signature that is maintained after differentiation.     

UCP2 mediates ghrelin's action on NPY/AgRP neurons by lowering free radicals

The gut-derived hormone ghrelin exerts its effect on the brain by regulating neuronal activity. Ghrelin-induced feeding behaviour is controlled by arcuate nucleus neurons that co-express neuropeptide Y and agouti-related protein (NPY/AgRP neurons). However, the intracellular mechanisms triggered by ghrelin to alter NPY/AgRP neuronal activity are poorly understood. Here we show that ghrelin initiates robust changes in hypothalamic mitochondrial respiration in mice that are dependent on uncoupling protein 2 (UCP2). Activation of this mitochondrial mechanism is critical for ghrelin-induced mitochondrial proliferation and electric activation of NPY/AgRP neurons, for ghrelin-triggered synaptic plasticity of pro-opiomelanocortin-expressing neurons, and for ghrelin-induced food intake. The UCP2-dependent action of ghrelin on NPY/AgRP neurons is driven by a hypothalamic fatty acid oxidation pathway involving AMPK, CPT1 and free radicals that are scavenged by UCP2. These results reveal a signalling modality connecting mitochondria-mediated effects of G-protein-coupled receptors on neuronal function and associated behaviour.     

Activating mutations in ALK provide a therapeutic target in neuroblastoma

Neuroblastoma, an embryonal tumour of the peripheral sympathetic nervous system, accounts for approximately 15% of all deaths due to childhood cancer. High-risk neuroblastomas are rapidly progressive; even with intensive myeloablative chemotherapy, relapse is common and almost uniformly fatal. Here we report the detection of previously unknown mutations in the ALK gene, which encodes a receptor tyrosine kinase, in 8% of primary neuroblastomas. Five non-synonymous sequence variations were identified in the kinase domain of ALK, of which three were somatic and two were germ line. The most frequent mutation, F1174L, was also identified in three different neuroblastoma cell lines. ALK complementary DNAs encoding the F1174L and R1275Q variants, but not the wild-type ALK cDNA, transformed interleukin-3-dependent murine haematopoietic Ba/F3 cells to cytokine-independent growth. Ba/F3 cells expressing these mutations were sensitive to the small-molecule inhibitor of ALK, TAE684 (ref. 4). Furthermore, two human neuroblastoma cell lines harbouring the F1174L mutation were also sensitive to the inhibitor. Cytotoxicity was associated with increased amounts of apoptosis as measured by TdT-mediated dUTP nick end labelling (TUNEL). Short hairpin RNA (shRNA)-mediated knockdown of ALK expression in neuroblastoma cell lines with the F1174L mutation also resulted in apoptosis and impaired cell proliferation. Thus, activating alleles of the ALK receptor tyrosine kinase are present in primary neuroblastoma tumours and in established neuroblastoma cell lines, and confer sensitivity to ALK inhibition with small molecules, providing a molecular rationale for targeted therapy of this disease.