SciCombinator

Discover the most talked about and latest scientific content & concepts.

Journal: Cell reports

424

Zika virus (ZIKV) is an emerging flavivirus that causes congenital abnormalities and Guillain-Barré syndrome. ZIKV infection also results in severe eye disease characterized by optic neuritis, chorioretinal atrophy, and blindness in newborns and conjunctivitis and uveitis in adults. We evaluated ZIKV infection of the eye by using recently developed mouse models of pathogenesis. ZIKV-inoculated mice developed conjunctivitis, panuveitis, and infection of the cornea, iris, optic nerve, and ganglion and bipolar cells in the retina. This phenotype was independent of the entry receptors Axl or Mertk, given that Axl(-/-), Mertk(-/-), and Axl(-/-)Mertk(-/-) double knockout mice sustained levels of infection similar to those of control animals. We also detected abundant viral RNA in tears, suggesting that virus might be secreted from lacrimal glands or shed from the cornea. This model provides a foundation for studying ZIKV-induced ocular disease, defining mechanisms of viral persistence, and developing therapeutic approaches for viral infections of the eye.

Concepts: Immune system, Gene, Virus, Infection, Eye, Ophthalmology, Tears, Optic nerve

318

Amyloidosis is a major problem in over one hundred diseases, including Alzheimer’s disease (AD). Using the iDISCO visualization method involving targeted molecular labeling, tissue clearing, and light-sheet microscopy, we studied plaque formation in the intact AD mouse brain at up to 27 months of age. We visualized amyloid plaques in 3D together with tau, microglia, and vasculature. Volume imaging coupled to automated detection and mapping enables precise and fast quantification of plaques within the entire intact mouse brain. The present methodology is also applicable to analysis of frozen human brain samples without specialized preservation. Remarkably, amyloid plaques in human brain tissues showed greater 3D complexity and surprisingly large three-dimensional amyloid patterns, or TAPs. The ability to visualize amyloid in 3D, especially in the context of their micro-environment, and the discovery of large TAPs may have important scientific and medical implications.

Concepts: Scientific method, Neuron, Disease, Human brain, Amyloid, Amyloidosis, Beta amyloid, Congo red

315

Antibiotics, though remarkably useful, can also cause certain adverse effects. We detected that treatment of adult mice with antibiotics decreases hippocampal neurogenesis and memory retention. Reconstitution with normal gut flora (SPF) did not completely reverse the deficits in neurogenesis unless the mice also had access to a running wheel or received probiotics. In parallel to an increase in neurogenesis and memory retention, both SPF-reconstituted mice that ran and mice supplemented with probiotics exhibited higher numbers of Ly6C(hi) monocytes in the brain than antibiotic-treated mice. Elimination of Ly6C(hi) monocytes by antibody depletion or the use of knockout mice resulted in decreased neurogenesis, whereas adoptive transfer of Ly6C(hi) monocytes rescued neurogenesis after antibiotic treatment. We propose that the rescue of neurogenesis and behavior deficits in antibiotic-treated mice by exercise and probiotics is partially mediated by Ly6C(hi) monocytes.

Concepts: Immune system, Psychology, Bacteria, Gut flora, Hippocampus, Antibiotic, Probiotic, Clostridium difficile

311

A CAPN1 missense mutation in Parson Russell Terrier dogs is associated with spinocerebellar ataxia. We now report that homozygous or heterozygous CAPN1-null mutations in humans result in cerebellar ataxia and limb spasticity in four independent pedigrees. Calpain-1 knockout (KO) mice also exhibit a mild form of ataxia due to abnormal cerebellar development, including enhanced neuronal apoptosis, decreased number of cerebellar granule cells, and altered synaptic transmission. Enhanced apoptosis is due to absence of calpain-1-mediated cleavage of PH domain and leucine-rich repeat protein phosphatase 1 (PHLPP1), which results in inhibition of the Akt pro-survival pathway in developing granule cells. Injection of neonatal mice with the indirect Akt activator, bisperoxovanadium, or crossing calpain-1 KO mice with PHLPP1 KO mice prevented increased postnatal cerebellar granule cell apoptosis and restored granule cell density and motor coordination in adult mice. Thus, mutations in CAPN1 are an additional cause of ataxia in mammals, including humans.

Concepts: DNA, Neuron, Mutation, Enzyme, Cerebellum, Granule cell, Point mutation, Jack Russell Terrier

280

High-protein (HP) intake during weight loss (WL) therapy is often recommended because it reduces the loss of lean tissue mass. However, HP intake could have adverse effects on metabolic function, because protein ingestion reduces postprandial insulin sensitivity. In this study, we compared the effects of ∼10% WL with a hypocaloric diet containing 0.8 g protein/kg/day and a hypocaloric diet containing 1.2 g protein/kg/day on muscle insulin action in postmenopausal women with obesity. We found that HP intake reduced the WL-induced decline in lean tissue mass by ∼45%. However, HP intake also prevented the WL-induced improvements in muscle insulin signaling and insulin-stimulated glucose uptake, as well as the WL-induced adaptations in oxidative stress and cell structural biology pathways. Our data demonstrate that the protein content of a WL diet can have profound effects on metabolic function and underscore the importance of considering dietary macronutrient composition during WL therapy for people with obesity.

Concepts: Protein, Nutrition, Enzyme, Insulin, Diabetes mellitus, Obesity, Adipose tissue, Metabolic syndrome

248

Cas9 cleaves specific DNA sequences with the assistance of a programmable single guide RNA (sgRNA). Repairing this broken DNA by the cell’s error-prone non-homologous end joining (NHEJ) machinery leads to insertions and deletions (indels) that often impair DNA function. Using HIV-1, we have now demonstrated that many of these indels are indeed lethal for the virus, but that others lead to the emergence of replication competent viruses that are resistant to Cas9/sgRNA. This unexpected contribution of Cas9 to the development of viral resistance is facilitated by some indels that are not deleterious for viral replication, but that are refractory to recognition by the same sgRNA as a result of changing the target DNA sequences. This observation illustrates two opposite outcomes of Cas9/sgRNA action, i.e., inactivation of HIV-1 and acceleration of viral escape, thereby potentially limiting the use of Cas9/sgRNA in HIV-1 therapy.

Concepts: DNA, Gene, Genetics, Mutation, Virus, Genome, RNA, DNA repair

239

Recent epidemics of Zika virus (ZIKV) have been associated with congenital malformation during pregnancy and Guillain-Barré syndrome. There are two ZIKV lineages (African and Asian) that share >95% amino acid identity. Little is known regarding the ability of neutralizing antibodies elicited against one lineage to protect against the other. We investigated the breadth of the neutralizing antibody response following ZIKV infection by measuring the sensitivity of six ZIKV strains to neutralization by ZIKV-confirmed convalescent human serum or plasma samples. Contemporary Asian and early African ZIKV strains were similarly sensitive to neutralization regardless of the cellular source of virus. Furthermore, mouse immune serum generated after infection with African or Asian ZIKV strains was capable of neutralizing homologous and heterologous ZIKV strains equivalently. Because our study only defines a single ZIKV serotype, vaccine candidates eliciting robust neutralizing antibody responses should inhibit infection of both ZIKV lineages, including strains circulating in the Americas.

Concepts: Immune system, Antibody, Protein, Neutralizing antibody, Bacteria, Acid, Antibodies, Congenital disorder

196

Adeno-associated virus (AAV) vectors have emerged as a gene-delivery platform with demonstrated safety and efficacy in a handful of clinical trials for monogenic disorders. However, limitations of the current generation vectors often prevent broader application of AAV gene therapy. Efforts to engineer AAV vectors have been hampered by a limited understanding of the structure-function relationship of the complex multimeric icosahedral architecture of the particle. To develop additional reagents pertinent to further our insight into AAVs, we inferred evolutionary intermediates of the viral capsid using ancestral sequence reconstruction. In-silico-derived sequences were synthesized de novo and characterized for biological properties relevant to clinical applications. This effort led to the generation of nine functional putative ancestral AAVs and the identification of Anc80, the predicted ancestor of the widely studied AAV serotypes 1, 2, 8, and 9, as a highly potent in vivo gene therapy vector for targeting liver, muscle, and retina.

Concepts: DNA, Gene, Molecular biology, Biology, Microbiology, Virus, Adeno-associated virus, Gene therapy

184

Autophagy is a conserved catabolic process that plays a housekeeping role in eliminating protein aggregates and organelles and is activated during nutrient deprivation to generate metabolites and energy. Autophagy plays a significant role in tumorigenesis, although opposing context-dependent functions of autophagy in cancer have complicated efforts to target autophagy for therapeutic purposes. We demonstrate that autophagy inhibition reduces tumor cell migration and invasion in vitro and attenuates metastasis in vivo. Numerous abnormally large focal adhesions (FAs) accumulate in autophagy-deficient tumor cells, reflecting a role for autophagy in FA disassembly through targeted degradation of paxillin. We demonstrate that paxillin interacts with processed LC3 through a conserved LIR motif in the amino-terminal end of paxillin and that this interaction is regulated by oncogenic SRC activity. Together, these data establish a function for autophagy in FA turnover, tumor cell motility, and metastasis.

Concepts: Protein, Cancer, Breast cancer, Metastasis, Oncology, Organelle, Cell biology, Tumor

182

The ventral subiculum (vSUB) plays a key role in addiction, and identifying the neuronal circuits and synaptic mechanisms by which vSUB alters the excitability of dopamine neurons is a necessary step to understand the motor changes induced by cocaine. Here, we report that high-frequency stimulation of the vSUB (HFSvSUB) over-activates ventral tegmental area (VTA) dopamine neurons in vivo and triggers long-lasting modifications of synaptic transmission measured ex vivo. This potentiation is caused by NMDA-dependent plastic changes occurring in the bed nucleus of the stria terminalis (BNST). Finally, we report that the modification of the BNST-VTA neural circuits induced by HFSvSUB potentiates locomotor activity induced by a sub-threshold dose of cocaine. Our findings unravel a neuronal circuit encoding behavioral effects of cocaine in rats and highlight the importance of adaptive modifications in the BNST, a structure that influences motivated behavior as well as maladaptive behaviors associated with addiction.

Concepts: Nervous system, Psychology, Neuron, Ventral tegmental area, Nicotine, Motivation, Human behavior, Dopamine