BACKGROUND:There is increasing evidence on the role of circular RNAs (circRNAs) in neuronal and muscular processes. Accordingly, their dysregulation is associated with neurodegenerative diseases and myopathies. We investigated circRNA expression in the central nervous system (CNS) and skeletal muscle, the two main tissues affected in amyotrophic lateral sclerosis (ALS). RESULTS:Based on circRNA sequencing analysis in spinal cord from ALS mice (SOD1G93A) followed by a literature search, 30 circRNAs potentially involved in ALS were tested. All selected circRNAs were downregulated in the SOD1G93A spinal cord, whereas only half of these were quantifiable and were generally upregulated in quadriceps muscle of SOD1G93A mice. Such tissue-dependent expression pattern was observed in both sexes and circRNA abundance in the spinal cord was higher than in the muscle, both in wild type and in SOD1G93A mice. Finally, we assessed the 18 circRNAs with the largest expression differences and the highest degree of interspecies conservation in brain samples from sporadic ALS (sALS) patients and healthy controls. Similar to the mouse model, circRNA levels tended to decrease in the CNS of sALS patients. CONCLUSIONS:Expression of circRNAs may be systematically altered in the two tissues most affected by ALS in a progressive and opposed manner. Although more detailed studies are warranted, circRNAs are potentially related to ALS etiopathogenesis and could possibly serve as future biomarkers, therapeutic targets, or customized therapeutic tools to modulate the pathology.

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Retroviral reverse transcriptase activity and the increased expression of human endogenous retroviruses (HERVs) are associated with amyotrophic lateral sclerosis (ALS). We were interested in confirming HERVK overexpression in the ALS brain, its use as an accessory diagnostic marker for ALS, and its potential interplay with neuroinflammation. Using qPCR to analyze HERVK expression in peripheral blood mononuclear cells (PBMCs) and in postmortem brain samples from ALS patients, no significant differences were observed between patients and control subjects. By contrast, we report alterations in the expression patterns of specific HERVK copies, especially in the brainstem. Out of 27 HERVK copies sampled, the relative expression of 17 loci was >1.2-fold changed in samples from ALS patients. In particular, the relative expression of two HERVK copies (Chr3-3 and Chr3-5) was significantly different in brainstem samples from ALS patients compared with controls. Further qPCR analysis of inflammation markers in brain samples revealed a significant increase in NLRP3 levels, while TNFA, IL6, and GZMB showed slight decreases. We cannot confirm global HERVK overexpression in ALS, but we can report the ALS-specific overexpression of selected HERVK copies in the ALS brain. Our data are compatible with the requirement for better patient stratification and support the potential importance of particular HERVK copies in ALS.

and IntroductionHuman endogenous retrovirus (HERV) are the present day versions of retroviral germline infections that have occured millions of years ago, which occupy about 8 % of the genome [1]. While they are mostly replication deficient, they are known to express RNA and protein [2] during particular developmental stages, or as a response to aging [3], inflammation and a wide range of pathologies [4]. A human retrovirus discovered in Multiple Sclerosis (MS) patients [5], turned out to be the prototype of a novel HERV family referred to as HERVW [6]. The HERVW family consists of 213 elements, 12 out of which are complete proviral copies with intact LTRs [7]. Increased expression of HERVW in peripheral blood mononuclear cells (PBMCs) has been repeatedly associated with MS, and the presence of HERVW protein or elevated RNA transcription has been correlated with disease activity [8,9,10]. While a contribution of HERVW-encoded proteins to brain disease is suggested by their presence in MS-associated brain lesions, expression in peripheral organs may be involved in the disease process through cytokine-induced damage to the blood brain barrier and subsequent infiltration of monocytes. Alterations in peripheral expression may also serve as a useful and practical marker for the diagnostics of this CNS disease. Therefore, we quantified overall HERVW levels and identified individual HERVW loci actually transcribed in PBMCs. Analysis was carried out in patients diagnosed with Clinically Isolated Syndrome (CIS), a precursor to MS, defined by a single episode of neurologic symptoms lasting at least 24 h. CIS is an indicator of future development of MS, as 60 % of the people diagnosed with CIS develop MS [11]. These patients potentially represent the earliest stage of MS routinely available for clinical analysis. We undertook a Next Generation Sequencing (NGS)-based analysis of transcripts amplified from cDNA obtained from patients with CIS and samples from healthy controls. Data presented from this pilot experiment indicate that the relative frequency of specific HERVW copies is altered in PBMC of CIS patients, even in the absence of overall HERVW overexpression. Such altered frequency appears to be derived from less abundantly transcribed but potentially MS-related HERVW loci.

Yin Yang 2 encodes a mammalian-specific transcription factor (YY2) that shares high homology in the zinc finger region with both YY1 and REX1/ZFP42, encoded by the Yin Yang 1 and Reduced Expression Protein 1/Zinc Finger Protein 42 gene, respectively. In contrast to the well-established roles of the latter two in gene regulation, X chromosome inactivation and binding to specific transposable elements (TEs), much less is known about YY2, and its presence during mouse preimplantation development has not been described. As it has been reported that mouse embryonic stem cells (mESC) cannot be propagated in the absence of Yy2, the mechanistic understanding of how Yy2 contributes to mESC maintenance remains only very partially characterized. We describe Yy2 expression studies using RT-PCR and staining with a high-affinity polyclonal serum in mouse embryos and mESC. Although YY2 is expressed during preimplantation development, its presence appears dispensable for developmental progress in vitro until formation of the blastocyst. Attenuation of Yy2 levels failed to alter either Zscan4 levels in two-cell embryos or IAP and MERVL levels at later preimplantation stages. In contrast to previous claims that constitutively expressed shRNA against Yy2 in mESC prohibited the propagation of mESC in culture, we obtained colonies generated from mESC with attenuated Yy2 levels. Concomitant with a decreased number of undifferentiated colonies, Yy2-depleted mESC expressed higher levels of Zscan4 but no differences in the expression of TEs or other pluripotency markers including Sox2, Oct4, Nanog and Esrrb were observed. These results confirm the contribution of Yy2 to the maintenance of mouse embryonic stem cells and show the preimplantation expression of YY2. These functions are discussed in relation to mammalian-specific functions of YY1 and REX1.

Aim: The aim of this study was to determine if alterations in DNA methylation in the human placenta would support suspected preterm labor as a pathologic insult associated with diminished placental health. Methods: We evaluated placental DNA methylation at seven loci differentially methylated in placental pathologies using targeted bisulfite sequencing, in placentas associated with preterm labor (term birth after suspected preterm labor [n = 15] and preterm birth [n = 15]), and controls (n = 15). Results: DNA methylation levels at the NCAM1 and PLAGL1 loci in placentas associated with preterm labor did differ significantly (p < 0.05) from controls. Discussion: Specific alterations in methylation patterns indicative of an unfavourable placental environment are associated with preterm labor per se and not restricted to preterm birth.

Placental 11β-hydroxysteroid dehydrogenase type 2 (11β-HSD2) operates as a functional barrier to protect the fetus from excessive exposure to maternal cortisol. Previous studies using animal models have demonstrated that prenatal stress can influence the expression of glucocorticoids related genes, reducing placenta function of 11B-HSD-2 which ultimately lead to suboptimal fetal growth. However, the influence of maternal stress on fetal outcomes, as well as the influence on the expression of the enzyme in the human placenta has not been previously described. The objective of this study was to determine the role of maternal stress in sub-optimal fetal growth and its relation with RNA expression and DNA methylation of the placental 11β-HSD2. Nested case-control study in full-term singleton gestations. The Perceived Stress Scale (PSS) and the state-trait anxiety inventory were assessed in mothers of pregnancies with antenatal suspicion of sub-optimal fetal growth that subsequently delivered a small for gestational age (SGA) neonate [birthweight<10th centile; n=205] and in a control group who delivered normally grown neonates (n=247). In addition, in a subset of patients (n=35 cases and 26 controls), RNA expression levels of placental 11β-HSD2 were analyzed, as well as the extent of DNA methylation (four CpG sites) of the locus. Maternal perceived stress scale was significantly higher in cases than in controls [Mean: 22 (SD ± 8.7) vs. 20.2 (SD ± 8.5); p=0.03]. Similarly, maternal state anxiety was significantly higher in mothers that subsequently delivered an SGA neonate compared to controls [1.8 (1.5 – 2.2) vs. 1.95 (1.7 – 2.35); p=0.0004]. Furthermore, placental 11β-HSD2 RNA expression (α)(Ln) was significantly lower in cases than in controls [0.41 (0.29 – 0.87) vs. 1.1 (0.62 – 1.75); p=0.003] (Figure 1). No differences were found in the average or mean percentage of placental 11β-HSD2 methylation between cases and controls. However, when groups were subdivided according to the presence of maternal stress, SGA cases with maternal stress (n=12) had a significantly different median level of methylation compared to controls [8.3 % (7.6 - 10.3) vs. 11.4 % (10.2 - 13.1); p=0.02] (Figure 2). Our findings suggest a significant association between pregnant women's stress and suboptimal fetal growth, affecting RNA expression and DNA methylation of glucocorticoids-related placental genes.View Large Image Figure ViewerDownload Hi-res image Download (PPT)

Background Yin Yang 2 (YY2) is a zinc finger protein closely related to the well-characterized Yin Yang 1 (YY1). YY1 is a DNA-binding transcription factor, with defined functions in multiple developmental processes, such as implantation, cell differentiation, X inactivation, imprinting and organogenesis. Yy2 has been treated as a largely immaterial duplication of Yy1, as they share high homology in the Zinc Finger-region and similar if not identical in vitro binding sites. In contrast to these similarities, gene expression alterations in HeLa cells with attenuated levels of either Yy1 or Yy2 were to some extent gene-specific. Moreover, the chromatin binding sites for YY2, except for its association with transposable retroviral elements (RE) and Endogenous Retroviral Elements (ERVs), remain to be identified. As a first step towards defining potential Yy2 functions matching or complementary to Yy1, we considered in vivo DNA binding sites of YY2 in trophoblast stem (TS) cells. Results We report the presence of YY2 protein in mouse-derived embryonic stem (ES) and TS cell lines. Following up on our previous report on ERV binding by YY2 in TS cells, we investigated the tissue-specificity of REX1 and YY2 binding and confirm binding to RE/ERV targets in both ES cells and TS cells. Because of the higher levels of expression, we chose TS cells to understand the role of Yy2 in gene and chromatin regulation. We used in vivo YY2 association as a measure to identify potential target genes. Sequencing of chromatin obtained in chromatin-immunoprecipitation (ChIP) assays carried out with αYY2 serum allowed us to identify a limited number of chromatin targets for YY2. Some putative binding sites were validated in regular ChIP assays and gene expression of genes nearby was altered in the absence of Yy2. Conclusions YY2 binding to ERVs is not confined to TS cells. In vivo binding sites share the presence of a consensus binding motif. Selected sites were uniquely bound by YY2 as opposed to YY1, suggesting that YY2 exerts unique contributions to gene regulation. YY2 binding was not generally associated with gene promoters. However, several YY2 binding sites are linked to long noncoding RNA (lncRNA) genes and we show that the expression levels of a few of those are Yy2-dependent.