STEEP mediates STING ER exit and activation of signaling.

STING is essential for control of infections and for tumor immunosurveillance, but it can also drive pathological inflammation. STING resides on the endoplasmic reticulum (ER) and traffics following stimulation to the ERGIC/Golgi, where signaling occurs. Although STING ER exit is the rate-limiting step in STING signaling, the mechanism that drives this process is not understood. Here we identify STEEP as a positive regulator of STING signaling. STEEP was associated with STING and promoted trafficking from the ER. This was mediated through stimulation of phosphatidylinositol-3-phosphate (PtdIns(3)P) production and ER membrane curvature formation, thus inducing COPII-mediated ER-to-Golgi trafficking of STING. Depletion of STEEP impaired STING-driven gene expression in response to virus infection in brain tissue and in cells from patients with STING-associated diseases. Interestingly, STING gain-of-function mutants from patients interacted strongly with STEEP, leading to increased ER PtdIns(3)P levels and membrane curvature. Thus, STEEP enables STING signaling by promoting ER exit.

Author Correction: STEEP mediates STING ER exit and activation of signaling.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

The influence of the 5΄-terminal nucleotide on AgoshRNA activity and biogenesis: importance of the polymerase III transcription initiation site.

Recent evidence indicates that shRNAs with a relatively short basepaired stem do not require Dicer processing, but instead are processed by the Argonaute 2 protein (Ago2). We named these molecules AgoshRNAs as both their processing and silencing function are mediated by Ago2. This alternative processing yields only a single RNA guide strand, which can avoid off-target effects induced by the passenger strand of regular shRNAs. It is important to understand this alternative processing route in mechanistic detail such that one can design improved RNA reagents. We verified that AgoshRNAs trigger site-specific cleavage of a complementary mRNA. Second, we document the importance of the identity of the 5΄-terminal nucleotide and its basepairing status for AgoshRNA activity. AgoshRNA activity is significantly reduced or even abrogated with C or U at the 5΄-terminal and is enhanced by introduction of a bottom mismatch and 5΄-terminal nucleotide A or G. The 5΄-terminal RNA nucleotide also represents the +1 position of the transcriptional promoter in the DNA, thus further complicating the analysis. Indeed, we report that +1 modification affects the transcriptional efficiency and accuracy of start site selection, with A or G as optimal nucleotide. These combined results allow us to propose general rules for the design and expression of potent AgoshRNA molecules.

NDRG2 promoted secreted miR-375 in microvesicles shed from M1 microglia, which induced neuron damage.

BACKGROUND: Microglia microvesicles (MVs) has shown to have significant biological functions under normal conditions. A diversity of miRNAs is involved in neuronal development, survival, function, and plasticity, but the exact functional role of NDRG2 and secreted miR-375 in MVs in neuron damage is poorly understood. We investigated the effect of NDRG2 and secreted miR-375 in MVs shed from M1 microglia on neuron damage. METHODS: Expression of Nos2, Arg-1, miR-375, syntaxin-1A, NDRG2 and Pdk 1 were evaluated using RT-PCR or western blotting. Cell viability of N2A neuron was quantified by a MTT assay. RESULTS: Microglia can be polarized into different functional phenotypes. Expression of NDRG2 and Nos2 were significantly increased by LPS treatment on N9 cells, whereas treatment with IL-4 dramatically suppressed the expression of NDRG2 and remarkably elevated expression of Arg-1. Besides, MVs shed from LPS-treated N9 microglia significantly inhibited cell viability of N2A neurons and expression of syntaxin-1A, and NDRG2 interference reversed the up-regulated miR-375 in LPS-treated N9 microglia and MVs shed from LPS-treated N9 cells. Furthermore, NDRG2 could modulate miR-375 expression in N9 microglia and MVs. And miR-375 inhibitor remarkably elevated Pdk1 expression in N2A neurons. Finally, miR-375 inhibitor could reverse suppression effect of NDRG2 overexpression on cell viability of N2A neurons and expression of syntaxin-1A. CONCLUSION: Our results demonstrated that NDRG2 promoted secreted miR-375 in microvesicles shed from M1 microglia, which induced neuron damage. The suppression of NDRG2 and secreted miR-375 in MVs shed from M1 microglia may be potential targets for alleviation of neuron damage.

Methylation entropy landscape of Chinese long-lived individuals reveals lower epigenetic noise related to human healthy aging.

The transition from ordered to noisy is a significant epigenetic signature of aging and age-related disease. As a paradigm of healthy human aging and longevity, long-lived individuals (LLI, >90 years old) may possess characteristic strategies in coping with the disordered epigenetic regulation. In this study, we constructed high-resolution blood epigenetic noise landscapes for this cohort by a methylation entropy (ME) method using whole genome bisulfite sequencing (WGBS). Although a universal increase in global ME occurred with chronological age in general control samples, this trend was suppressed in LLIs. Importantly, we identified 38,923 genomic regions with LLI-specific lower ME (LLI-specific lower entropy regions, for short, LLI-specific LERs). These regions were overrepresented in promoters, which likely function in transcriptional noise suppression. Genes associated with LLI-specific LERs have a considerable impact on SNP-based heritability of some aging-related disorders (e.g., asthma and stroke). Furthermore, neutrophil was identified as the primary cell type sustaining LLI-specific LERs. Our results highlight the stability of epigenetic order in promoters of genes involved with aging and age-related disorders within LLI epigenomes. This unique epigenetic feature reveals a previously unknown role of epigenetic order maintenance in specific genomic regions of LLIs, which helps open a new avenue on the epigenetic regulation mechanism in human healthy aging and longevity.

Scrutiny of genome-wide somatic mutation profiles in centenarians identifies the key genomic regions for human longevity.

Somatic mutations accumulate with age and are associated closely with human health, their characterization in longevity cohorts remains largely unknown. Here, by analyzing whole genome somatic mutation profiles in 73 centenarians and 51 younger controls in China, we found that centenarian genomes are characterized by a markedly skewed distribution of somatic mutations, with many genomic regions being specifically conserved but displaying a high function potential. This, together with the observed more efficient DNA repair ability in the long-lived individuals, supports the existence of key genomic regions for human survival during aging, with their integrity being of essential to human longevity.

Gut microbiota contributes to high-altitude hypoxia acclimatization of human populations.

BACKGROUND: The relationship between human gut microbiota and high-altitude hypoxia acclimatization remains highly controversial. This stems primarily from uncertainties regarding both the potential temporal changes in the microbiota under such conditions and the existence of any dominant or core bacteria that may assist in host acclimatization. RESULTS: To address these issues, and to control for variables commonly present in previous studies which significantly impact the results obtained, namely genetic background, ethnicity, lifestyle, and diet, we conducted a 108-day longitudinal study on the same cohort comprising 45 healthy Han adults who traveled from lowland Chongqing, 243 masl, to high-altitude plateau Lhasa, Xizang, 3658 masl, and back. Using shotgun metagenomic profiling, we study temporal changes in gut microbiota composition at different timepoints. The results show a significant reduction in the species and functional diversity of the gut microbiota, along with a marked increase in functional redundancy. These changes are primarily driven by the overgrowth of Blautia A, a genus that is also abundant in six independent Han cohorts with long-term duration in lower hypoxia environment in Shigatse, Xizang, at 4700 masl. Further animal experiments indicate that Blautia A-fed mice exhibit enhanced intestinal health and a better acclimatization phenotype to sustained hypoxic stress. CONCLUSIONS: Our study underscores the importance of Blautia A species in the gut microbiota's rapid response to high-altitude hypoxia and its potential role in maintaining intestinal health and aiding host adaptation to extreme environments, likely via anti-inflammation and intestinal barrier protection.

A comparative analysis on the synonymous codon usage pattern in viral functional genes and their translational initiation region of ASFV.

The synonymous codon usage pattern of African swine fever virus (ASFV), the similarity degree of the synonymous codon usage between this virus and some organisms and the synonymous codon usage bias for the translation initiation region of viral functional genes in the whole genome of ASFV have been investigated by some simply statistical analyses. Although both GC12% (the GC content at the first and second codon positions) and GC3% (the GC content at the third codon position) of viral functional genes have a large fluctuation, the significant correlations between GC12 and GC3% and between GC3% and the first principal axis of principle component analysis on the relative synonymous codon usage of the viral functional genes imply that mutation pressure of ASFV plays an important role in the synonymous codon usage pattern. Turning to the synonymous codon usage of this virus, the codons with U/A end predominate in the synonymous codon family for the same amino acid and a weak codon usage bias in both leading and lagging strands suggests that strand compositional asymmetry does not take part in the formation of codon usage in ASFV. The interaction between the absolute codon usage bias and GC3% suggests that other selections take part in the formation of codon usage, except for the mutation pressure. It is noted that the similarity degree of codon usage between ASFV and soft tick is higher than that between the virus and the pig, suggesting that the soft tick plays a more important role than the pig in the codon usage pattern of ASFV. The translational initiation region of the viral functional genes generally have a strong tendency to select some synonymous codons with low GC content, suggesting that the synonymous codon usage bias caused by translation selection from the host takes part in modulating the translation initiation efficiency of ASFV functional genes.

Mitogenome evidence shows two radiation events and dispersals of matrilineal ancestry from northern coastal China to the Americas and Japan.

Although it is widely recognized that the ancestors of Native Americans (NAs) primarily came from Siberia, the link between mitochondrial DNA (mtDNA) lineage D4h3a (typical of NAs) and D4h3b (found so far only in East China and Thailand) raises the possibility that the ancestral sources for early NAs were more variegated than hypothesized. Here, we analyze 216 contemporary (including 106 newly sequenced) D4h mitogenomes and 39 previously reported ancient D4h data. The results reveal two radiation events of D4h in northern coastal China, one during the Last Glacial Maximum and the other within the last deglaciation, which facilitated the dispersals of D4h sub-branches to different areas including the Americas and the Japanese archipelago. The coastal distributions of the NA (D4h3a) and Japanese lineages (D4h1a and D4h2), in combination with the Paleolithic archaeological similarities among Northern China, the Americas, and Japan, lend support to the coastal dispersal scenario of early NAs.

Comparative [corrected] codon usage between the three main viruses in pestivirus genus and their natural susceptible livestock.

Classical swine fever virus, bovine viral diarrhea virus (BVDV), and border disease virus can cause serious livestock diseases. The relative synonymous codon usage value, the "effective number of codons" (ENC), the ratio of K(s) value to K(a) value and the principle component analysis were employed to analyze the genetic characteristics of open reading frame (ORF) and the four genes (the N(pro), Erns, E1, E2 genes) of the three viruses and the relationship of codon usage pattern between each virus and its most common host. The amount of under-represented codons is larger than the amount of over-represented ones in ORFs or the four genes of the three viruses. The ENC value and the ratio of K(s)/K(a) for each gene show that mutation pressure plays a role in their evolutional processes. In addition, the evidence that selection from the natural host might influences the codon usage patterns of virus is found in the differences of codon usage patterns of ORF and Erns gene of BVDV strain ZM-95 isolated from domestic pig and those of the rest of BVDV strains isolated from cattle. These results indicate that although a strong mutation pressure from the three pestiviruses takes part in their evolutional processes by the alternation of synonymous codons, translation selection from the susceptible livestock on some genes should not be ignored. The codon usage pattern of the three pestiviruses is a result caused by the equilibrium of mutation pressure from virus and translation selection from its host.

Complete mitogenomes document substantial genetic contribution from the Eurasian Steppe into northern Pakistani Indo-Iranian speakers.

To elucidate whether Bronze Age population dispersals from the Eurasian Steppe to South Asia contributed to the gene pool of Indo-Iranian-speaking groups, we analyzed 19,568 mitochondrial DNA (mtDNA) sequences from northern Pakistani and surrounding populations, including 213 newly generated mitochondrial genomes (mitogenomes) from Iranian and Dardic groups, both speakers from the ancient Indo-Iranian branch in northern Pakistan. Our results showed that 23% of mtDNA lineages with west Eurasian origin arose in situ in northern Pakistan since ~5000 years ago (kya), a time depth very close to the documented Indo-European dispersals into South Asia during the Bronze Age. Together with ancient mitogenomes from western Eurasia since the Neolithic, we identified five haplogroups (~8.4% of maternal gene pool) with roots in the Steppe region and subbranches arising (age ~5-2 kya old) in northern Pakistan as genetic legacies of Indo-Iranian speakers. Some of these haplogroups, such as W3a1b that have been found in the ancient samples from the late Bronze Age to the Iron Age period individuals of Swat Valley northern Pakistan, even have sub-lineages (age ~4 kya old) in the southern subcontinent, consistent with the southward spread of Indo-Iranian languages. By showing that substantial genetic components of Indo-Iranian speakers in northern Pakistan can be traced to Bronze Age in the Steppe region, our study suggests a demographic link with the spread of Indo-Iranian languages, and further highlights the corridor role of northern Pakistan in the southward dispersal of Indo-Iranian-speaking groups.

Mitochondrial ND3 as the novel causative gene for Leber hereditary optic neuropathy and dystonia.

Leber hereditary optic neuropathy and dystonia (LDYT) is a mitochondrial disorder associated with variable combinations of vision loss and progressive generalized dystonia. LDYT is a unique oxidative phosphorylation disorder caused by mutations in mitochondrial ND6 or ND4 gene. In this paper, we describe a Chinese family with 18 LDYT patients. The comprehensive nucleotide sequence analysis of the entire mitochondrial genome using resequencing microarray revealed a mutation (mtND3*10197A (m.10197G>A)) substituting a threonine for a highly conserved alanine at codon 47 of MTND3 on the background of haplogroup D4b. Quantitative analysis of the heteroplasmy of the mutation revealed a homoplasmy in the leukocytes of all the affected individuals on the maternal side. This is the first description of the ND3 mutation causing LDYT. The mtND3*10197A (m.10197G>A) mutation has recently been described in French and Korean patients with Leigh syndrome. These findings suggest that the clinical presentations associated with the mtND3*10197A (m.10197G>A) mutation (ND3) are much wider, encompassing those of LDYT and Leigh syndrome.

Establishment and evaluation of stable cell lines inhibiting foot-and-mouth disease virus by RNA interference.

RNA interference (RNAi) has been proved to be a powerful tool for foot-and-mouth disease virus FMDV inhibition in vitro and in vivo. We established five stable baby hamster kidney 21 cell lines (BHK-21) containing five short hairpin RNAs (shRNAs) expression plasmids (p3D1shRNA, p3D2shRNA, p3D3shRNA, p3D4shRNA, and p3D5shRNA) targeting 3D gene of FMDV. Immunofluorescent assay, virus titration, and real-time quantitative reverse transcription polymerase chain reaction (Q-RT-PCR) were conducted to detect the effect of shRNAs on FMDV replication. After challenged with FMDV of O/CHA/99, two cell lines (p3D1shRNA and p3D4shRNA) showed a significant reduction in the synthesis of viral protein and RNA, accompanied by a sharp decrease in viral yield, and the inhibition could last for at least thirty passages. We developed an efficient procedure for the establishment and evaluation of stable cell lines for anti-FMDV research based on RNAi technology, which can be a candidate method for anti-FMDV research.

The silent point mutations at the cleavage site of 2A/2B have no effect on the self-cleavage activity of 2A of foot-and-mouth disease virus.

The 2A region of the foot-and-mouth disease virus (FMDV) polyprotein is 18 amino acids in length, and 2A self-cleavage site (2A/2B) contains a conserved amino acid motif G2A/P2B. To investigate the synonymous codon usage for Glycine at the 2A/2B cleavage site of FMDV, 66 2A/2B1 nucleotide sequences were aligned and found that the synonymous codon usage of G2A is conserved and GGG was the most frequently used. To examine the role of synonymous codons for G2A in self-cleavage efficiency of 2A/2B, recombinant constructs which contains the chloramphenicol acetyltransferase protein (CAT) and enhanced green fluorescent protein (EGFP) linked by the FMDV 2A sequence with four synonymous codons for G2A were produced. The activities of all the F2As based plasmids were determined in CHO cells. The results showed that the synonymous codon usage patterns for G2A at the cleavage site (2A/2B) have no effect on the cleavage efficiency. This suggests that the synonymous codon usage of 2A peptide has no effect on the cleavage efficiency of FMDV 2A element.

PIN1-842G/C and -667T/C polymorphisms are not associated with the susceptibility of Alzheimer's disease: pooled analysis of epidemiologic studies.

Associations between PIN1 gene polymorphisms and Alzheimer's disease (AD) risk remain controversial, possibly because single studies often lack sufficient statistical power. In this study, we performed a meta-analysis to evaluate the association of two commonly studied PIN1 polymorphisms, -842G/C and -667T/C, with the risk of AD. Relevant studies were identified from PubMed, EMBASE, and China National Knowledge Infrastructure up to October 2012. Data were available from a total of 7 case-control studies with 2504 cases and 2322 controls. Crude odds ratios (OR) and 95% confidence intervals (CI) were used to investigate the strength of the association. The results showed no significant association between PIN1-842G/C polymorphism and AD risk in all comparison models (GG vs. GC: OR=0.84, 95%CI=0.61-1.18; GG vs. CC: OR=0.70, 95%CI=0.35-1.41; GC vs. CC: OR=0.81, 95%CI=0.39-1.69; G vs. C: OR=0.89, 95%CI=0.69-1.17; GG vs. GC+CC: OR=0.81, 95%CI=0.56-1.17; GG+GC vs. CC: OR=0.72, 95%CI=0.36-1.45). For the PIN1-667T/C polymorphism, lack of an association was also found. Subgroup analyses by the ethnicity and patients with late-onset AD did not change the results. Conclusively, the present meta-analysis revealed that PIN1 gene polymorphisms (-842G/C and -667T/C) were unlikely to contribute to AD susceptibility.

The analysis of codon bias of foot-and-mouth disease virus and the adaptation of this virus to the hosts.

The synonymous codon usage patterns of open reading frame (ORF) in foot-and-mouth disease virus (FMDV), the similarity degree of the synonymous codon usage between this virus and the hosts and the genetic diversities of FMDV ORFs and the viral functional genes in viral ORF have been investigated by some simply statistical analyses. As for the synonymous codon usage of FMDV, some over-represented and under-represented codons have a similar usage in all seven serotypes. 33 out of 59 synonymous codons are similarly selected between FMDV ORF and the hosts. It is interesting that the overall codon usage pattern of the strains of serotype O isolated from pigs is different with that of strains of the same serotype isolated from non-pig origin, suggesting that the factor of pigs takes part in the formation of codon usage of FMDV serotype O. Projection of codon usage of nine viral functional genes onto the two-dimensional map represents that even though viral functional genes have various genetic diversities and each gene is not separated from each other based on seven serotypes, the codon usage patterns of VP2, 2C, 3A, 3C and 3D genes belonging to serotype O strains isolated from pigs are different with those of the same serotype strains from non-pig origin. In addition, the interaction between GC12% and GC3% of viral functional genes indicates that the codon usage patterns of VP1, VP2, 2B, 3A, 3C and 3D genes are influenced by mutation pressure from virus. Furthermore, distribution plots of ENC value vs. GC3% for viral function genes indicate that mutation pressure is not the only factor in the formation of codon usage of these genes. The results suggest that both the mutation pressure from virus and the translation selection from the hosts take part in the evolution process of viral functional genes of FMDV.