AimsThe role of nitric oxide (NO) in heart failure (HF) is complex and remains controversial. We tested the hypothesis that the role of NO in isolated atria and cardiomyocytes is altered in isoproterenol-induced HF. Methods and resultsRats received isoproterenol (ISO, 5 mg/kg/day, intraperitoneally) or vehicle for 1 week. Haemodynamic parameters were obtained by left ventricular catheterization. Effects of NOS inhibition on isolated atria and on electrically paced left ventricular myocytes were determined. Additionally, expressions of nitric oxide synthases and their allosteric modulators hsp90, caveolin-1, and caveolin-3 proteins in the left ventricles were measured. ISO increased left ventricular mass by 33% and decreased indices of left ventricular systolic and diastolic function dp/dt min and dp/dt max (both P , 0.05). Isolated atria from HF rats had a lower spontaneous beating rate (P , 0.05). NOS inhibition by L-NAME increased basal frequency and attenuated the positive chronotropic effect of beta-adrenergic stimulation in the HF group (P , 0.05). Ventricular myocytes from failing hearts had impaired cell shortening. L-NAME decreased contractility of control, but not failing myocytes. Left ventricular expressions of eNOS, hsp90, iNOS, but not nNOS or caveolins, were increased. ConclusionDespite the increased capacity for NO synthesis in isoproterenol-induced HF, NO does not sustain contractility of failing myocytes. NO may contribute to the decreased basal heart rate and it may accelerate beta-adrenergic stimulation of chronotropy.--

BackgroundHuman immunodeficiency virus type 1 (HIV-1) latency represents the major barrier to virus eradication in infected individuals because cells harboring latent HIV-1 provirus are not affected by current antiretroviral therapy (ART). We previously demonstrated that DNA methylation of HIV-1 long terminal repeat (5’ LTR) restricts HIV-1 reactivation and, together with chromatin conformation, represents an important mechanism of HIV-1 latency maintenance. Here, we explored the new issue of temporal development of DNA methylation in latent HIV-1 5’ LTR.ResultsIn the Jurkat CD4+ T cell model of latency, we showed that the stimulation of host cells contributed to de novo DNA methylation of the latent HIV-1 5’ LTR sequences. Consecutive stimulations of model CD4+ T cell line with TNF-α and PMA or with SAHA contributed to the progressive accumulation of 5’ LTR DNA methylation. Further, we showed that once established, the high DNA methylation level of the latent 5’ LTR in the cell line model was a stable epigenetic mark. Finally, we explored the development of 5’ LTR DNA methylation in the latent reservoir of HIV-1-infected individuals who were treated with ART. We detected low levels of 5’ LTR DNA methylation in the resting CD4+ T cells of the group of patients who were treated for up to 3 years. However, after long-term ART, we observed an accumulation of 5’ LTR DNA methylation in the latent reservoir. Importantly, within the latent reservoir of some long-term-treated individuals, we uncovered populations of proviral molecules with a high density of 5’ LTR CpG methylation.ConclusionsOur data showed the presence of 5’ LTR DNA methylation in the long-term reservoir of HIV-1-infected individuals and implied that the transient stimulation of cells harboring latent proviruses may contribute, at least in part, to the methylation of the HIV-1 promoter.Electronic supplementary materialThe online version of this article (doi:10.1186/s13148-016-0185-6) contains supplementary material, which is available to authorized users.

Subgroup J avian leukosis virus (ALV-J) is unique among the avian sarcoma and leukosis viruses in using the multimembranespanning cell surface protein Na ؉ /H ؉ exchanger type 1 (NHE1) as a receptor. The precise localization of amino acids critical for NHE1 receptor activity is key in understanding the virus-receptor interaction and potential interference with virus entry. Because no resistant chicken lines have been described until now, we compared the NHE1 amino acid sequences from permissive and resistant galliform species. In all resistant species, the deletion or substitution of W38 within the first extracellular loop was observed either alone or in the presence of other incidental amino acid changes. Using the ectopic expression of wild-type or mutated chicken NHE1 in resistant cells and infection with a reporter recombinant retrovirus of subgroup J specificity, we studied the effect of individual mutations on the NHE1 receptor capacity. We suggest that the absence of W38 abrogates binding of the subgroup J envelope glycoprotein to ALV-J-resistant cells. Altogether, we describe the functional importance of W38 for virus entry and conclude that natural polymorphisms in NHE1 can be a source of host resistance to ALV-J.T he first step in retrovirus infection is attachment of the virus envelope glycoproteins to the specific cell surface receptor. Consequently, the susceptibility of each cell strictly depends on the expression and display of proper receptor molecules. This attachment, as well as the following phases of virus entry, requires a perfect match of receptors and envelope glycoproteins (1). Structural alterations within variable and hypervariable envelope glycoprotein regions easily abrogate the infectivity or even change the receptor usage and broaden the host range. This is best exemplified by avian sarcoma and leukosis viruses (ASLVs), a closely related group of retroviruses which evolved into five subgroups, A to E, that utilize three different receptors encoded by three genetic loci, tva, tvb, and tvc (1, 2). The tva locus encodes a protein belonging to the family of low-density lipoprotein receptors and determines susceptibility to the subgroup A ASLVs (3, 4). The tumor necrosis factor receptor-related protein encoded by the tvb locus confers susceptibility to subgroup B, D, and E ASLVs (5-7). Finally, subgroup C ASLVs utilize the Tvc protein of the butyrophilin family with two immunoglobulin-like domains (8). The complete resistance or decreased susceptibility of host chicken cells to a particular ASLV subgroup can then be caused by premature termination or a frameshift in the receptor-encoding loci (8-10), decreased receptor expression and display (11), and even single amino acid substitutions in the receptor sequence (9, 12).Subgroup J avian leukosis virus (ALV-J), the prototype virus isolate of which is HPRS-103, is an independent envelope subgroup which does not interfere with subgroups A to E and cannot be neutralized by antisera raised against subgroups A to E (13). ALV-J was originally d...

Avian leukosis virus subgroup J (ALV-J) is an important concern for the poultry industry. Replication of ALV-J depends on a functional cellular receptor, the chicken Na+/H+ exchanger type 1 (chNHE1). Tryptophan residue number 38 of chNHE1 (W38) in the extracellular portion of this molecule is a critical amino acid for virus entry. We describe a CRISPR/Cas9-mediated deletion of W38 in chicken primordial germ cells and the successful production of the gene-edited birds. The resistance to ALV-J was examined both in vitro and in vivo, and the ΔW38 homozygous chickens tested ALV-J–resistant, in contrast to ΔW38 heterozygotes and wild-type birds, which were ALV-J–susceptible. Deletion of W38 did not manifest any visible side effect. Our data clearly demonstrate the antiviral resistance conferred by precise CRISPR/Cas9 gene editing in the chicken. Furthermore, our highly efficient CRISPR/Cas9 gene editing in primordial germ cells represents a substantial addition to genotechnology in the chicken, an important food source and research model.

Syncytin-1 and -2, human fusogenic glycoproteins encoded by the env genes of the endogenous retroviral loci ERVWE1 and ERVFRDE1, respectively, contribute to the differentiation of multinucleated syncytiotrophoblast in chorionic villi. In non-trophoblastic cells, however, the expression of syncytins has to be suppressed to avoid potential pathogenic effects. We studied the epigenetic suppression of ERVWE1 and ERVFRDE1 5′-long terminal repeats by DNA methylation and chromatin modifications. Immunoprecipitation of the provirus-associated chromatin revealed the H3K9 trimethylation at transcriptionally inactivated syncytins in HeLa cells. qRT-PCR analysis of non-spliced ERVWE1 and ERVFRDE1 mRNAs and respective env mRNAs detected efficient splicing of endogenously expressed RNAs in trophoblastic but not in non-placental cells. Pointing to the pathogenic potential of aberrantly expressed syncytin-1, we have found deregulation of transcription and splicing of the ERVWE1 in biopsies of testicular seminomas. Finally, ectopic expression experiments suggest the importance of proper chromatin context for the ERVWE1 splicing. Our results thus demonstrate that cell-specific retroviral splicing represents an additional epigenetic level controling the expression of endogenous retroviruses.

Background: PP2A is a regulator of cardiac excitation-contraction coupling. Results: Cardiomyocyte-directed overexpression of B56␣, the main cardiac PP2A regulatory subunit, results in the dephosphorylation of myofilament proteins, increased Ca 2ϩ sensitivity, and higher contractility. Conclusion: This suggests an important role for B56␣ in regulating PP2A activity and thereby the contractile function. Significance: PP2A-B56␣ is a potential pharmacological target to improve cardiac performance in failing hearts.

Avian leukosis viruses (ALVs), which are pathogens of concern in domestic poultry, utilize specific receptor proteins for cell entry that are both necessary and sufficient for host susceptibility to a given ALV subgroup. This unequivocal relationship offers receptors as suitable targets of selection and biotechnological manipulation with the aim of obtaining virus-resistant poultry. This approach is further supported by the existence of natural knock-outs of receptor genes that segregate in inbred lines of chickens. We used CRISPR/Cas9 genome editing tools to introduce frame-shifting indel mutations into tva, tvc, and tvj loci encoding receptors for the A, C, and J ALV subgroups, respectively. For all three loci, the homozygous frame-shifting indels generating premature stop codons induced phenotypes which were fully resistant to the virus of respective subgroup. In the tvj locus, we also obtained in-frame deletions corroborating the importance of W38 and the four amino-acids preceding it. We demonstrate that CRISPR/Cas9-mediated knock-out or the fine editing of ALV receptor genes might be the first step in the development of virus-resistant chickens.

The group of closely related avian sarcoma and leukosis viruses (ASLVs) evolved from a common ancestor into multiple subgroups, A to J, with differential host range among galliform species and chicken lines. These subgroups differ in variable parts of their envelope glycoproteins, the major determinants of virus interaction with specific receptor molecules. Three genetic loci, tva, tvb, and tvc, code for single membrane-spanning receptors from diverse protein families that confer susceptibility to the ASLV subgroups. The host range expansion of the ancestral virus might have been driven by gradual evolution of resistance in host cells, and the resistance alleles in all three receptor loci have been identified. Here, we characterized two alleles of the tva receptor gene with similar intronic deletions comprising the deduced branch-point signal within the first intron and leading to inefficient splicing of tva mRNA. As a result, we observed decreased susceptibility to subgroup A ASLV in vitro and in vivo. These alleles were independently found in a close-bred line of domestic chicken and Indian red jungle fowl (Gallus gallus murghi), suggesting that their prevalence might be much wider in outbred chicken breeds. We identified defective splicing to be a mechanism of resistance to ASLV and conclude that such a type of mutation could play an important role in virus-host coevolution. Retroviruses enter the host cell through specific receptors, cell surface proteins with high affinity to viral envelope glycoproteins. The interaction between receptors and viral glycoproteins is very complex and includes the initial attachment of the virion, profound conformational changes in the structure of the viral glycoprotein, exposure of fusion peptides, and, ultimately, the fusion of viral and cellular membranes (5, 47). Despite the strict structural requirements for these interactions, hypervariability of retroviral glycoproteins can change the receptor usage and broaden the host range. Indeed, closely related families of retroviruses have evolved into multiple subgroups that utilize different cellular surface proteins as receptors. For example, the group of avian alpharetroviruses avian sarcoma and leukosis viruses (ASLVs) comprise 10 related subgroups, A to J, which either do not interfere at all with each other or interfere only nonreciprocally in infecting chicken cells. The susceptibility of chicken cells to highly related ASLV subgroups A to E is determined by three genetic loci, tva, tvb, and tvc (5, 41). The Tva protein belongs to the family of low-density lipoprotein receptors (LDLRs) (6, 48) and determines susceptibility to the subgroup A ASLVs. The tumor necrosis factor receptor-related protein Tvb confers susceptibility to subgroup B, D, and E ASLVs by three nonoverlapping binding sites (2,3,8), and the Tvc protein, closely related to the mammalian butyrophilins, serves as receptor for C subgroup ASLV (14).The rapid evolution of novel retrovirus envelopes is compelled by the appearance of host entry restrictions. Gen...