RNA interference (RNAi) is a sequence-specific gene regulatory mechanism conserved among diverse eukaryotes. The sequence specificity in RNAi is determined by a family of 18-to 30-nucleotide (nt) regulatory small RNAs (for review, see Aravin and Tuschl 2005). Two major classes of endogenous small RNAs have been characterized: microRNAs (miRNAs) and small interfering RNAs (siRNAs). miRNAs-the best-characterized endogenous small RNAs in eukaryotes-have been identified in diverse plants and animals, and are mainly involved in development and differentiation. miRNAs are processed from miRNA precursors (pre-miRNAs) with a stem-loop structure and regulate gene expression through translational repression or mRNA cleavage (for reviews, see Ambros 2004;Bartel 2004;He and Hannon 2004;Du and Zamore 2005). siRNAs are generated from long double-stranded RNA (dsRNA) and are mainly involved in defense against molecular parasites including viruses, transposons, and transgenes through RNAi (Sijen and Plasterk 2003;Shi et al. 2004). Endogenous siRNAs have been classified into at least three subclasses: repeat-associated siRNAs (rasiRNAs), trans-acting siRNAs (ta-siRNAs), and siRNAs derived from natural antisense transcripts (nat-siRNAs) (Lippman and Martienssen 2004;Peragine et al. 2004;Borsani et al. 2005). rasiRNAs corresponding to repetitive elements repress the repeat sequences at the transcriptional or post-transcriptional level and maintain a centromeric heterochromatic
Observations of rapid shifts in mitochondrial DNA (mtDNA) variants between generations prompted the creation of the bottleneck theory. A prevalent hypothesis is that a massive reduction in mtDNA content during early oogenesis leads to the bottleneck. To test this, we estimated the mtDNA copy number in single germline cells and in single somatic cells of early embryos in mice. Primordial germ cells (PGCs) show consistent, moderate mtDNA copy numbers across developmental stages, whereas primary oocytes demonstrate substantial mtDNA expansion during early oocyte maturation. Some somatic cells possess a very low mtDNA copy number. We also demonstrated that PGCs have more than 100 mitochondria per cell. We conclude that the mitochondrial bottleneck is not due to a drastic decline in mtDNA copy number in early oogenesis but rather to a small effective number of segregation units for mtDNA in mouse germ cells. These results provide new information for mtDNA segregation models and for understanding the recurrence risks for mtDNA diseases.
Peri-operative SARS-CoV-2 infection increases postoperative mortality. The aim of this study was to determine the optimal duration of planned delay before surgery in patients who have had SARS-CoV-2 infection. This international, multicentre, prospective cohort study included patients undergoing elective or emergency surgery during October 2020. Surgical patients with pre-operative SARS-CoV-2 infection were compared with those without previous SARS-CoV-2 infection. The primary outcome measure was 30-day postoperative mortality. Logistic regression models were used to calculate adjusted 30-day mortality rates stratified by time from diagnosis of SARS-CoV-2 infection to surgery. Among 140,231 patients (116 countries), 3127 patients (2.2%) had a pre-operative SARS-CoV-2 diagnosis. Adjusted 30-day mortality in patients without SARS-CoV-2 infection was 1.5% (95%CI 1.4-1.5). In patients with a pre-operative SARS-CoV-2 diagnosis, mortality was increased in patients having surgery within 0-2 weeks, 3-4 weeks and 5-6 weeks of the diagnosis (odds ratio (95%CI) 4.1 (3.3-4.8), 3.9 (2.6-5.1) and 3.6 (2.0-5.2), respectively). Surgery performed ≥ 7 weeks after SARS-CoV-2 diagnosis was associated with a similar mortality risk to baseline (odds ratio (95%CI) 1.5 (0.9-2.1)). After a ≥ 7 week delay in undertaking surgery following SARS-CoV-2 infection, patients with ongoing symptoms had a higher mortality than patients whose symptoms had resolved or who had been asymptomatic (6.0% (95%CI 3.2-8.7) vs. 2.4% (95%CI 1.4-3.4) vs. 1.3% (95%CI 0.6-2.0), respectively). Where possible, surgery should be delayed for at least 7 weeks following SARS-CoV-2 infection. Patients with ongoing symptoms ≥ 7 weeks from diagnosis may benefit from further delay.
The expression pattern and function of the murine endogenous retrovirus-like (MuERV-L) gene in mouse preimplantation embryos was investigated. MuERV-L was rapidly transcribed from the beginning of S phase (8 h after fertilization) in the first cell cycle. MuERV-L expression was completely repressed when transcription from the zygotic genome was inhibited by alpha-amanitin. These results reveal that MuERV-L is transcribed from the zygotic genome and that it is expressed earlier than any other genes previously reported. In addition, MuERV-L was expressed even when the first round of DNA synthesis was inhibited by aphidicolin, suggesting that its expression is controlled by the zygotic clock. The function of MuERV-L in the development of mouse embryos was also examined using antisense oligonucleotides. The developmental competence of embryos was markedly suppressed after the 4-cell stage when they were treated with antisense oligonucleotides. This result suggests that MuERV-L plays an important role in the development of mouse embryos at the early preimplantation stage.
Gonocytes are primitive germ cells that reside in the seminiferous tubules of neonatal testes and give rise to spermatogonia, thereby initiating spermatogenesis. Due to a lack of specific markers, the isolation and culture of these cells has proven to be difficult in the pig. In the present study, we show that a lectin, Dolichos biflorus agglutinin (DBA), which has specific affinity for primordial germ cells (PCGs) in the genital ridge, binds specifically to gonocytes in neonatal pig testes. The specific affinity of DBA for germ cells was progressively lost with age. This suggests that DBA binds strongly to primitive germ cells, such as gonocytes, weakly to primitive spermatogonia, and not at all to spermatogonia. The presence of alkaline phosphatase (AP) activity in the germ cells of neonatal pig testis confirmed the existence of primitive germ cells. Gonocytes from neonatal pig testis were purified, and a cell population that consisted of approximately 70% gonocytes was obtained, as indicated by the DBA binding assay. Purified gonocytes were cultured in DMEM/F12 supplemented with 10% FBS in the absence of any specific growth factors for 7 days. The cells remained viable and proliferated actively in culture. Initially, the gonocytes grew as focal colonies that transformed to three-dimensional colonies by 7 days of culture. Cultured germ cells expressed SSEA-1, a marker for embryonic stem (ES) cells, and were negative for the expression of somatic cell markers. These results should help to establish a male germ cell line that could be used for studying spermatogenesis in vitro and for genetic modification of pigs.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
customersupport@researchsolutions.com
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
This site is protected by reCAPTCHA and the Google Privacy Policy and Terms of Service apply.
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.