Identification and characterization of L1-specific endo-siRNAs essential for early embryonic development in pig

Delivering the Promise of Gene Therapy with Nanomedicines in Treating Central Nervous System Diseases

Central Nervous System (CNS) diseases, such as Alzheimer's diseases (AD), Parkinson's Diseases (PD), brain tumors, Huntington's disease (HD), and stroke, still remain difficult to treat by the conventional molecular drugs. In recent years, various gene therapies have come into the spotlight as versatile therapeutics providing the potential to prevent and treat these diseases. Despite the significant progress that has undoubtedly been achieved in terms of the design and modification of genetic modulators with desired potency and minimized unwanted immune responses, the efficient and safe in vivo delivery of gene therapies still poses major translational challenges. Various non-viral nanomedicines have been recently explored to circumvent this limitation. In this review, an overview of gene therapies for CNS diseases is provided and describes recent advances in the development of nanomedicines, including their unique characteristics, chemical modifications, bioconjugations, and the specific applications that those nanomedicines are harnessed to deliver gene therapies.

Pathogenic Effects and Potential Regulatory Mechanisms of Tea Polyphenols on Obesity

Overweight and obesity are major threats to human health. Tea polyphenols exert multiple beneficial effects on human health and may play a positive regulatory role in fat assumption. However, how tea polyphenols contribute to the regulation of fat metabolism remains unclear to date. Small RNA expression profile can be regulated by tea polyphenols in adipocytes. Therefore, tea polyphenols may regulate fat metabolism by controlling small RNA-associated biological processes. In this study, we developed a systematic research platform based on mouse models and performed small RNA sequencing to identify the specific role of small RNAs in the regulatory effect of tea polyphenols on fat metabolism. We compared the expression levels of different small RNA subtypes, including piRNAs and miRNAs, and identified a group of differentially expressed small RNAs in the experimental and control groups. Most of these small RNAs participate in lipid metabolism, suggesting that small RNAs play a significant role in tea polyphenol-associated obesity and related pathogenesis. Furthermore, gene ontology and KEGG pathway enrichment indicated that small RNAs influence the regulatory effects of tea polyphenols on obesity, revealing the potential pathogenic mechanisms for such nutritional disease.

Endo-siRNAs regulate early embryonic development by inhibiting transcription of long terminal repeat sequence in pig†

Activity of some endogenous retroviruses (ERVs) has been proven to be important for development of early mammalian embryo. However, abnormal activation of ERVs can also cause genetic diseases due to their ability to retrotranspose, so the regulatory mechanism to limit transcription of ERVs needs to be clarified. Endogenous small interfering RNA (endo-siRNA) has been reported to protect cells against transposable elements (TEs). Here, we determined the role of ERVs long terminal repeat sequences (LTRs) derived endo-siRNAs (LTR-siRNAs) on inhibition of the activity of ERVs during early embryonic development in pig. Seven most highly expressed LTR-siRNAs were identified in porcine zygote by high-throughput small RNA sequencing. We verified that the biogenesis of the LTR-siRNAs was DICER-dependent and they were generated from double-stranded RNA (dsRNA) formed by sense and antisense transcripts of LTRs. And, the expression of sense and antisense of LTRs might be due to the loss of DNA methylation at some LTR loci. Furthermore, we showed that the LTR-siRNAs could regulate early embryonic development by repression of LTRs expression at a post-transcriptional level. So, we propose here, during early embryonic development when epigenetic reprogramming occurs, the endo-siRNA pathway acts as a sophisticated balance of regulatory mechanism for ERV activity.

Endo-siRNAs repress expression of SINE1B during in vitro maturation of porcine oocyte

Approximately 40% of mammalian genome is made of transposable elements (TEs), and during specific biological processes, such as gametogenesis, they may be activated by global demethylation, so strict silencing mechanism is indispensable for genomic stability. Here, we performed small RNA-seq on Dicer1 knockdown (KD) oocytes in pig, and observed short interspersed nuclear elements 1B (SINE1B) derived endogenous small interfering RNAs (endo-siRNAs), termed SINE1B-siRNAs, were significantly decreased and their biogenesis was dependent on Dicer1 and transcript of SINE1B. Furthermore, by injection of mimics and inhibitors of the SINE1B-siRNAs into germinal vesicle-stage (GV-stage) oocytes, we found the maturation rate was significantly decreased by SINE1B-siRNAs, indicating the SINE1B-siRNAs are indispensible for in vitro maturation (IVM) of porcine oocyte. To figure out the mechanism, we checked the expression pattern and DNA methylation status of SINE1B during IVM of porcine oocytes, and demonstrated the SINE1B-siRNAs could repress SINE1B expression induced by hypomethylation at a post-transcriptional level. Our results suggest that during gametogenesis when the erasure of DNA methylation occurs, endo-siRNAs act as a chronic response to limit retrotransposon activation.

Oocyte related factors impacting on embryo quality: relevance for in vitro embryo production

The outcome of pregnancy is closely linked to early events that occur during the onset of embryogenesis. The first stages in embryonic development are mainly governed by the storage of maternal factors present in the oocyte at the time of fertilisation. In this review, we outline the different classes of oocyte transcripts that may be involved in activation of the embryonic genome as well as those associated with epigenetic reprogramming, imprinting maintenance or the control of transposon mobilisation during preimplantation development. We also report the influence of cumulus-oocyte crosstalk during the maturation process on the oocyte transcriptome and how in vitro procedures can affect these interactions.

A Possible Role for Long Interspersed Nuclear Elements-1 (LINE-1) in Huntington's Disease Progression

BACKGROUND Recent studies have shown that increased mobilization of Long Interspersed Nuclear Elements-1 (L1) can promote the pathophysiology of multiple neurological diseases. However, its role in Huntington's disease (HD) remains unknown. MATERIAL AND METHODS R6/2 mice - a common mouse model of HD - were used to evaluate changes in L1 mobilization. Pyrosequencing was used to evaluate methylation content changes. L1-ORF1 and L1-ORF2 expression analysis were evaluated by RT-PCR and immunoblotting. Changes in pro-survival signaling were evaluated by L1-ORF overexpression studies and validated in the mouse model by immunohistochemistry and immunoblotting. RESULTS We found an increased mobilization of L1 elements in the caudate genome of R6/2 mice (p<0.05) - a common mouse model of HD - but not in wild-type mice. Subsequent pyrosequencing and expression analysis showed that the L1 elements were hypomethylated and their respective ORFs were overexpressed in the affected tissues. In addition, a significant decrease in the pro-survival proteins such as the phosphoproteins of AKT target proteins, mTORC1 activity, and AMPK alpha levels was observed with the increase in the expression L1-ORF2. CONCLUSIONS These findings indicate that hyperactive retrotransposition of L1 triggers a downstream signaling pathway affecting the neuronal survival pathways via downregulation of mTORC1 activity and AMPKalpha and increasing apoptosis in neurons.

Re-Arrangements in the Cytoplasmic Distribution of Small RNAs Following the Maternal-to-Zygotic Transition in Drosophila Embryos

Small ribonucleic acids (RNAs) are known to regulate gene expression during early development. However, the dynamics of interaction between small RNAs and polysomes during this process is largely unknown. To investigate this phenomenon, 0–1 h and 7–8 h Drosophila melanogaster embryos were fractionated on sucrose density gradients into four fractions based on A₂₅₄ reading (1) translationally inactive messenger ribonucleoprotein (mRNP), (2) 60S, (3) monosome, and (4) polysome. Comparative analysis of deep-sequencing reads from fractionated and un-fractionated 0–1 h and 7–8 h embryos revealed development-specific co-sedimentation pattern of small RNAs with the cellular translation machinery. Although most micro RNAs (miRNAs) did not have a specific preference for any state of the translational machinery, we detected fraction-specific enrichment of a few miRNAs such as dme-miR-1-3p, -184-3p, 5-5p and 263-5p. More interestingly, we observed changes in the subcellular location of a subset of miRNAs in fractionated embryos despite no measurable difference in their amount in unfractionated embryos. Transposon-derived endo small interfering RNAs (siRNAs) were over-expressed in 7–8 h embryos and associated mainly with the mRNP fraction. In contrast, transposon-derived PIWI-interacting RNAs (piRNA), which were more abundant in 0–1 h embryos, co-sedimented primarily with the polysome fractions. These results suggest that there appears to be a complex interplay among the small RNAs with respect to their polysome-cosedimentation pattern during early development in Drosophila melanogaster.