Origin of porcine circovirus type 2 (PCV2) from swine affected by PCV2-associated diseases in Croatia.

Porcine circovirus type 2 (PCV2) causes some of the most significant economic losses in pig production. Several multisystemic syndromes have been attributed to PCV2 infection, which are known as PCV2-associated diseases (PCVDs). This study investigated the origin and evolution of PCV2 sequences in domestic pigs and wild boars affected by PCVDs in Croatia. Viral sequences were recovered from three wild boars diagnosed with PCV2-systemic disease (PCV2-SD), 63 fetuses positive for PCV2 DNA as determined by PCR, 14 domestic pigs affected with PCV2-SD (displaying severe interstitial nephritis) and five domestic pigs with proliferative and necrotising pneumonia. Seventeen complete PCV2 genomes were recovered. Phylogenetic and evolutionary analyses based on median-joining phylogenetic networks, amino acid alignments and principal coordinate analysis were performed using complete genomes, as well as complete and partial ORF sequences for ORF1 and ORF2. Two of the 17 PCV2 sequences belonged to PCV2a, 14 to PCV2b and one was unclustered. PCV2b was the predominant genotype in Croatia and has been linked to international trade as a route of introduction. Correlation between particular viral strains with PCVDs is lacking.

DTI abnormalities in anterior corpus callosum of rats with spike-wave epilepsy.

OBJECTIVE: Absence epilepsy is a common seizure disorder in children which can produce chronic psychosocial sequelae. Human patients and rat absence models show bilateral spike-wave discharges (SWD) in cortical regions. We employed diffusion tensor imaging (DTI) in rat absence models to detect abnormalities in white matter pathways connecting regions of seizure activity. METHODS: We studied Wistar albino Glaxo rats of Rijswijk (WAG/Rij), genetic absence epilepsy rats of Strasbourg (GAERS), and corresponding nonepileptic control strains. Ex vivo DTI was performed at 9.4 T with diffusion gradients applied in 16 orientations. We compared fractional anisotropy (FA), perpendicular (lambda(perpendicular)) and parallel (lambda(||)) diffusivity between groups using t-maps and region of interest (ROI) measurements. RESULTS: Adult epileptic WAG/Rij rats exhibited a localized decrease in FA in the anterior corpus callosum. This area was confirmed by tractography to interconnect somatosensory cortex regions most intensely involved in seizures. This FA decrease was not present in young WAG/Rij rats before onset of SWD. GAERS, which have more severe SWD than WAG/Rij, exhibited even more pronounced callosal FA decreases. Reduced FA in the epileptic animals originated from an increased lambda(perpendicular) with no significant changes in lambda(||). INTERPRETATION: Reduced FA with increased lambda(perpendicular) suggests that chronic seizures cause reduction in myelin or decreased axon fiber density in white matter pathways connecting regions of seizure activity. These DTI abnormalities may improve the understanding of chronic neurological difficulties in children suffering with absence epilepsy, and may also serve as a noninvasive biomarker for monitoring beneficial effects of treatment.

Targeting silence: the use of site-specific recombination to introduce in vitro methylated DNA into the genome.

DNA methylation has emerged as an important component of transcriptional regulation. However, our understanding of how DNA methylation influences transcription, chromatin structure, replication timing, and imprinting has been limited by the lack of experimental systems that permit control of the methylation state of genes in a chromosomal context. Here, we describe a novel technique that allows for efficient introduction of methylated and unmethylated DNA into defined sites in the mammalian genome. This protocol utilizes bacterial CpG methyltransferases to methylate the DNA of interest in vitro, followed by site-specific targeting using Cre recombinase. Long-term maintenance of the methylation state in vivo allows analysis of the biological consequences of methylation by direct comparison of the methylated and unmethylated state in the same genomic position.

Methylation-mediated proviral silencing is associated with MeCP2 recruitment and localized histone H3 deacetylation.

The majority of 5-methylcytosine in mammalian DNA resides in endogenous transposable elements and is associated with the transcriptional silencing of these parasitic elements. Methylation also plays an important role in the silencing of exogenous retroviruses. One of the difficulties inherent in the study of proviral silencing is that the sites in which proviruses randomly integrate influence the probability of de novo methylation and expression. In order to compare methylated and unmethylated proviruses at the same genomic site, we used a recombinase-based targeting approach to introduce an in vitro methylated or unmethylated Moloney murine leukemia-based provirus in MEL cells. The methylated and unmethylated states are maintained in vivo, with the exception of the initially methylated proviral enhancer, which becomes demethylated in vivo. Although the enhancer is unmethylated and remodeled, the methylated provirus is transcriptionally silent. To further analyze the repressed state, histone acetylation status was determined by chromatin immunoprecipitation (ChIP) analyses, which revealed that localized histone H3 but not histone H4 hyperacetylation is inversely correlated with proviral methylation density. Since members of the methyl-CpG binding domain (MBD) family of proteins recruit histone deacetylase activity, these proteins may play a role in proviral repression. Interestingly, only MBD3 and MeCP2 are expressed in MEL cells. ChIPs with antibodies specific for these proteins revealed that only MeCP2 associates with the provirus in a methylation-dependent manner. Taken together, our results suggest that MeCP2 recruitment to a methylated provirus is sufficient for transcriptional silencing, despite the presence of a remodeled enhancer.

Position effects are influenced by the orientation of a transgene with respect to flanking chromatin.

We have inserted two expression cassettes at tagged reference chromosomal sites by using recombinase-mediated cassette exchange in mammalian cells. The three sites of integration displayed either stable or silencing position effects that were dominant over the different enhancers present in the cassettes. These position effects were strongly dependent on the orientation of the construct within the locus, with one orientation being permissive for expression and the other being nonpermissive. Orientation-specific silencing, which was observed at two of the three site tested, was associated with hypermethylation but not with changes in chromatin structure, as judged by DNase I hypersensitivity assays. Using CRE recombinase, we were able to switch in vivo the orientation of the transgenes from the permissive to the nonpermissive orientation and vice versa. Switching from the permissive to the nonpermissive orientation led to silencing, but switching from the nonpermissive to the permissive orientation did not lead to reactivation of the transgene. Instead, transgene expression occurred dynamically by transcriptional oscillations, with 10 to 20% of the cells expressing at any given time. This result suggested that the cassette had been imprinted (epigenetically tagged) while it was in the nonpermissive orientation. Methylation analysis revealed that the methylation state of the inverted cassettes resembled that of silenced cassettes except that the enhancer had selectively lost some of its methylation. Sorting of the expressing and nonexpressing cell populations provided evidence that the transcriptional oscillations of the epigenetically tagged cassette are associated with changes in the methylation status of regulatory elements in the transgene. This suggests that transgene methylation is more dynamic than was previously assumed.

Reporters of gene expression: enzymatic assays.

Initially developed for use in bacteria, reporter gene systems are now being utilized in eukaryotic cells.

Genomic targeting of methylated DNA: influence of methylation on transcription, replication, chromatin structure, and histone acetylation.

We have developed a strategy to introduce in vitro-methylated DNA into defined chromosomal locations. Using this system, we examined the effects of methylation on transcription, chromatin structure, histone acetylation, and replication timing by targeting methylated and unmethylated constructs to marked genomic sites. At two sites, which support stable expression from an unmethylated enhancer-reporter construct, introduction of an in vitro-methylated but otherwise identical construct results in specific changes in transgene conformation and activity, including loss of the promoter DNase I-hypersensitive site, localized hypoacetylation of histones H3 and H4 within the reporter gene, and a block to transcriptional initiation. Insertion of methylated constructs does not alter the early replication timing of the loci and does not result in de novo methylation of flanking genomic sequences. Methylation at the promoter and gene is stable over time, as is the repression of transcription. Surprisingly, sequences within the enhancer are demethylated, the hypersensitive site forms, and the enhancer is hyperacetylated. Nevertheless, the enhancer is unable to activate the methylated and hypoacetylated reporter. Our findings suggest that CpG methylation represses transcription by interfering with RNA polymerase initiation via a mechanism that involves localized histone deacetylation. This repression is dominant over a remodeled enhancer but neither results in nor requires region-wide changes in DNA replication or chromatin structure.

Dynamic analysis of proviral induction and De Novo methylation: implications for a histone deacetylase-independent, methylation density-dependent mechanism of transcriptional repression.

Methylation of cytosines in the CpG dinucleotide is generally associated with transcriptional repression in mammalian cells, and recent findings implicate histone deacetylation in methylation-mediated repression. Analyses of histone acetylation in in vitro-methylated transfected plasmids support this model; however, little is known about the relationships among de novo DNA methylation, transcriptional repression, and histone acetylation state. To examine these relationships in vivo, we have developed a novel approach that permits the isolation and expansion of cells harboring expressing or silent retroviruses. MEL cells were infected with a Moloney murine leukemia virus encoding the green fluorescent protein (GFP), and single-copy, silent proviral clones were treated weekly with the histone deacetylase inhibitor trichostatin A or the DNA methylation inhibitor 5-azacytidine. Expression was monitored concurrently by flow cytometry, allowing for repeated phenotypic analysis over time, and proviral methylation was determined by Southern blotting and bisulfite methylation mapping. Shortly after infection, proviral expression was inducible and the reporter gene and proviral enhancer showed a low density of methylation. Over time, the efficacy of drug induction diminished, coincident with the accumulation of methyl-CpGs across the provirus. Bisulfite analysis of cells in which 5-azacytidine treatment induced GFP expression revealed measurable but incomplete demethylation of the provirus. Repression could be overcome in late-passage clones only by pretreatment with 5-azacytidine followed by trichostatin A, suggesting that partial demethylation reestablishes the trichostatin-inducible state. These experiments reveal the presence of a silencing mechanism which acts on densely methylated DNA and appears to function independently of histone deacetylase activity.

Single cell analysis and selection of living retrovirus vector-corrected mucopolysaccharidosis VII cells using a fluorescence-activated cell sorting-based assay for mammalian beta-glucuronidase enzymatic activity.

Mutations in the acid beta-glucuronidase gene lead to systemic accumulation of undegraded glycosaminoglycans in lysosomes and ultimately to clinical manifestations of mucopolysaccharidosis VII (Sly disease). Gene transfer by retrovirus vectors into murine mucopolysaccharidosis VII hematopoietic stem cells or fibroblasts ameliorates glycosaminoglycan accumulation in some affected tissues. The efficacy of gene therapy for mucopolysaccharidosis VII depends on the levels of beta-glucuronidase secreted by gene-corrected cells; therefore, enrichment of transduced cells expressing high levels of enzyme prior to transplantation is desirable. We describe the development of a fluorescence-activated cell sorter-based assay for the quantitative analysis of beta-glucuronidase activity in viable cells. Murine mucopolysaccharidosis VII cells transduced with a beta-glucuronidase retroviral vector can be isolated by cell sorting on the basis of beta-glucuronidase activity and cultured for further use. In vitro analysis revealed that sorted cells have elevated levels of beta-glucuronidase activity and secrete higher levels of cross-correcting enzyme than the population from which they were sorted. Transduced fibroblasts stably expressing beta-glucuronidase after subcutaneous passage in the mucopolysaccharidosis VII mouse can be isolated by cell sorting and expanded ex vivo. A relatively high percentage of these cells maintain stable expression after secondary transplantation, yielding significantly higher levels of enzymatic activity than that generated in the primary transplant.

Families with multiple cases of gluten-sensitive enteropathy.

UNLABELLED: Early detection of oligosymptomatic gluten-sensitive enteropathy (GSE) may contribute to the prevention of late complications, such as malignancy. Family members of known GSE patients are at higher risk of being affected. To evaluate the frequency and clinical significance of multiple occurrence, we routinely offered an antiendomysium antibody (EmA)-based non-invasive screening to affected families. Among 997 family members of 396 GSE patients, we identified 89 subjects with EmA positivity and/or severe jejunal villous atrophy. In 83 cases GSE has been verified, four patients refused the biopsy and two subjects are under further observation for latent celiac disease. Prevalence of GSE was 8.5% (80/943) among the first-degree relatives, with significantly higher values in the siblings (13.8%) and offsprings (12.0%) than in the parents (4.2%) of the probands (p < 0.001). In 55 families (13.9% of the families studied) two, in ten families (2.5%) three, in one family four and in one other family six members were affected. Combinations of the clinical presentations of index and screening-detected cases were highly variable, with a high percentage of silent and atypical forms in the relatives. GSE cases presenting both with and without dermatitis herpetiformis occurred in 15 families. Six GSE cases with atypical or mild dermatitis herpetiformis were detected in consequence of the screening. CONCLUSIONS: EmA-assisted family screening resulted in the detection of a clinically significant number of additional GSE patients.

Prospective significance of antiendomysium antibody positivity in subsequently verified celiac disease.

BACKGROUND: In order to assess their long-term predictability for the diagnosis of celiac disease, antiendomysium antibody results were compared with the outcome of the Interlaken diagnostic process. METHODS: Prospective gluten challenge was performed in 153 children with previously diagnosed flat small-intestine mucosa. In 90 patients (Group A), endomysium antibodies were initially positive, in seven (Group B) they were negative, and 56 patients (Group C) had no initial serological results. In IgA-deficient persons, IgG antibodies were also assayed, both by the immunofluorescent method. RESULTS: Histological relapse rates were 100% (90/90), 14.3% (1/7), and 76.8% (43/56), p < 0.001, in Groups A, B, and C, respectively. Each patient with relapse also exhibited endomysium antibody positivity during the challenge. Patients in whom celiac disease could be finally ruled out remained consistently endomysium-antibody negative. The celiac disease patient in Group B had severe secondary immunoglobulin deficiency at entry, which explained the initial negativity. Diagnosis based on antiendomysium antibody positivity and flat mucosa gave a higher applicability (92.8 vs. 50.3%) and reliability (relapse rate 100 vs. 89.6%) than the 1990 European Society of Paediatric Gastroenterology and Nutrition (ESPGAN) criteria among these patients. CONCLUSIONS: Endomysium antibody positivity at presentation has been found to be as useful as gluten challenge in the diagnosis of celiac disease, even in patients under the age of 2 years. Challenge is still advisable in patients with a flat small intestinal mucosa when antiendomysium antibody results are negative or have not been done, as among these patients significantly lower relapse rates were found.

Detection and isolation of gene-corrected cells in Gaucher disease via a fluorescence-activated cell sorter assay for lysosomal glucocerebrosidase activity.

Gaucher disease type 1 results from the accumulation of glucocerebroside in macrophages of the reticuloendothelial system, as a consequence of a deficiency in glucocerebrosidase (GC) activity. Recent improvements in the methodologies for introducing foreign genes into bone marrow stem cells have prompted several groups to test the efficacy of gene transfer therapy as a curative treatment for Gaucher disease. Limitations of this approach include the potential for insufficient engraftment of gene-corrected cells and incomplete transduction of hematopoietic stem cells using retroviral gene transfer. Overcoming these obstacles may be critical in the case of treatment for Gaucher disease type 1, because GC transduced cells have not been shown to have a growth advantage over noncorrected cells. Here, we describe the development and application of a novel, fluorescence-activated cell sorter based assay that directly quantitates GC activity at the single cell level. In a test of this application, fibroblasts from a Gaucher patient were transduced, and high expressing cells sorted based on GC activity. Reanalysis of cultured sorted fibroblasts reveals that these cells maintain high levels of enzymatic activity, compared with the heterogeneous population from which they were sorted. The assay is sufficiently sensitive to distinguish GC activity found in Gaucher patient monocytes from that in normal controls. Furthermore, preliminary results indicate that increased GC activity can be detected in transduced, CD34+ enriched peripheral blood mononuclear cells isolated from a Gaucher patient. This method should be a useful addition to current gene therapy protocols as a means to quantitatively assess gene correction of relevant cell populations and potentially purify transduced cells for transplantation.

Variable subcellular localization of a neuron-specific protein during NTera 2 differentiation into post-mitotic human neurons.

The current report describes the molecular characterization of the human (the D4S234 locus) and mouse (the m234) homologs of a gene that was isolated during our genomic analysis of the Huntington disease gene region. Sequence comparisons of full-length cDNA clones revealed that the mouse and human homologs encoded evolutionarily conserved 21-kDa proteins with greater than 90% amino acid sequence identity. Extensive sequence identity between the D4S234 gene and the rat p1A75 gene (a previously identified rat neuron-specific gene) showed that these genes are interspecies homologs. Furthermore, the D4S234 protein exhibited significant amino acid similarity to a 19-kDa mouse protein that localizes to the Golgi apparatus of embryonic neurons. However, nonconservative sequence differences suggested that these genes are independent members of a multigene family. Northern analyses revealed that rodent D4S234 expression occurred predominantly in the brain and included all brain regions. Neuron-specific expression was demonstrated using Northern analysis of cultured glial cells and quinolinic acid-treated rat brain samples. Minimal amounts of the rodent D4S234 mRNA were detected prenatally; however, elevated adult levels were detected within 1 month of birth. Sequence analyses of the human and mouse D4S234 proteins identified an evolutionarily conserved hydrophobic sequence and a consensus nuclear localization signal in both genes. Immunofluorescence microscopy, using an antipeptide antibody, established that the human D4S234 protein preferentially localized to the nucleus of mitotic cultured cells. Since the rat p1A75 protein was previously mapped to the neuronal cytoplasm by in situ hybridization, the subcellular localization of the D4S234 protein was subsequently examined during differentiation of the NTera 2 (NT2) cell line. Following differentiation into postmitotic NT2-N neurons, the D4S234 protein demonstrated cytoplasmic staining and reduced or undetectable nuclear staining in many cells. The variation in the intracellular localization of the D4S234 protein in mitotic and nonmitotic cells suggests that the subcellular localization of this protein is developmentally regulated and provides clues about the biochemical function of this protein.

Enzyme-generated intracellular fluorescence for single-cell reporter gene analysis utilizing Escherichia coli beta-glucuronidase.

We report the development of a new fluorescence-activated cell sorter (FACS)-based reporter gene system utilizing the enzymatic activity of the E. coli beta-glucuronidase (gus) gene. When loaded with the Gus substrate fluorescein-di-beta-D-glucuronide (FDGlcu), individual mammalian cells expressing and translating gus mRNA liberate sufficient levels of intracellular fluorescein for quantitative analysis by flow cytometry. This assay can be used to FACS sort viable cells based on Gus enzymatic activity, and the efficacy of the assay can be measured independently by using a fluorometric lysate assay. Furthermore, both the beta-glucuronidase and the previously described E. coli beta-galactosidase enzymes have high specificities for their cognate substrates, allowing each reporter gene to be measured by FACS independently.

Simultaneous fluorescence-activated cell sorter analysis of two distinct transcriptional elements within a single cell using engineered green fluorescent proteins.

Green fluorescent protein (GFP) is widely used as a reporter gene in both prokaryotes and eukaryotes. However, the fluorescence levels of wild-type GFP (wtGFP) are not bright enough for fluorescence-activated cell sorting or flow cytometry. Several GFP variants were generated that are brighter or have altered excitation spectra when expressed in prokaryotic cells. We engineered two GFP genes with different combinations of these mutations, GFP(S65T,V163A) termed GFP-Bex1, and GFP(S202F,T203I,V163A) termed GFP-Vex1. Both show enhanced brightness and improved signal-to-noise ratios when expressed in mammalian cells and appropriately excited, compared with wtGFP. Each mutant retains only one of the two excitation peaks of the wild-type protein. GFP-Bex1 excites at 488 nm (blue) and GFP-Vex1 excites at 406 nm (violet), both of which are available laser lines. Excitation at these wavelengths allows for the independent analyses of these mutants by fluorescence-activated cell sorting, permitting simultaneous, quantitative detection of expression from two different genes within single mammalian cells.

[New cases of celiac disease detected by anti-endomysial antibody test in families of gluten-sensitive patients and among children examined for non-specific gastrointestinal complaints]. / Anti-endomysium ellenanyag vizsgálattal felderített új coeliakia esetek gluten sensitiv betegek családjában és nem specifikus gastrointestinalis panaszok miatt vizsgált gyermekekben.

Among 228 relatives of 101 gluten-sensitive patients, 13 anti-endomysium antibody (EmA) positive persons (7 children and 6 adults) were identified. In 12/13 cases jejunal biopsy confirmed severe villous atrophy consistent with celiac disease. In the single EmA positive sibling without villous atrophy the histology is thought to be influenced by a steroid treatment because of pulmonary disease. By routine EmA-testing 12 unexpected EmA positive patients were found out of 756 children with complaints and laboratory results otherwise not justifying jejunal biopsy at the first evaluation. Their initial diagnoses were: proteinuria, colitis, Crohn's disease, rickets, recurrent vomiting, resolved postinfectious lactase deficiency, "previously excluded" celiac disease. Severe villous atrophy could be demonstrated in all EmA positive patients subsequently. In further 204 EmA negative children the biopsy showed no atrophy. EmA positivity may reveal clinically not apparent severe villous atrophy emphasizing the role of a new non invasive and highly specific serological screening method for celiac disease.

An estimate of the number of genes in the Huntington disease gene region and the identification of 13 transcripts in the 4p16.3 segment.

Physical mapping and genetic linkage studies have positioned the Huntington disease (HD) gene to a relatively large genomic region in the distal portion of the short arm of human chromosome 4 (4p16.3). To estimate the number of genes present in this region and to identify candidate disease genes, several clones that map to the 4p16.3 segment have been examined for clusters of CpG-rich restriction sites and transcribed sequences. Thirteen expressed sequences were identified and were shown by pulsed-field gel electrophoresis not to cluster into a small segment of the 4p16.3 band. The frequency of transcripts in these clones suggests that the putative HD gene region contains about 100 genes.

[Congenital saccharase-isomaltase defect--diagnostic difficulties]. / Congenitalis saccharase-isomaltase defektus--a diagnózis nehézségei.

Seven patients with congenital sucrase-isomaltase deficiency corresponding to the known diagnostic criteria and five patients having combined disaccharidase deficiencies with unusual pattern characterized by more pronounced sucrase than lactase deficiency were found among 505 children investigated by first jejunal biopsy. On the base of the case histories, the complications and the comparative evaluation of patient and control groups' data (the latter consisted of nine untreated coeliacs) the congenital sucrase-isomaltase deficiency was found to make the patients to be especially susceptible to enteral infections and consequently to postinfectious intestinal damages. These complicated cases do not correspond to the classic diagnostic criteria of the congenital enzyme deficiency causing diagnostic errors. In order to avoid the misdiagnoses the authors suggest modification of the diagnostic criteria of congenital sucrase-isomaltase deficiency as follows: the diagnosis of congenital enzyme deficiency might be verified in spite of mild histological signs and hypolactasia if the degree of lactase deficiency repeatedly and significantly is exceeded by the degree of sucrase deficiency.