Covid-19: Fat, Obesity, Inflammation, Ethnicity, and Sex Differences

Although obesity is known to be a risk factor for COVID-19 severity, there is an urgent need to distinguish between different kinds of fat-visceral and subcutaneous fat-and their inflammation status in COVID-19. These different fat types have partially diverging biochemical roles in the human body, and they are differentially associated with SARS-CoV-2, which targets the angiotensin-converting enzyme 2 (ACE2) for cell entry. ACE2 is highly expressed in adipose tissue, especially in visceral fat, suggesting an important role for this tissue in determining COVID-19 disease severity. In this perspective article, we discuss group differences in the amount of visceral fat levels and the extent of inflammation in adipocytes of visceral fat tissue, which may, in part, drive population, cross-national, ethnic, and sex differences in COVID-19 disease. It is vital to steer the scientific community's attention to the effects of visceral fat in creating individual and population differences in COVID-19 severity. This can help researchers unravel the reasons for the reported population, ethnic, and sex differences in COVID-19 severity and mortality

RNase H1 promotes replication fork progression through oppositely transcribed regions of Drosophila mitochondrial DNA

Mitochondrial DNA (mtDNA) replication uses a simple core machinery similar to those of bacterial viruses and plasmids, but its components are challenging to unravel. Here, we found that, as in mammals, the single Drosophila gene for RNase H1 (rnh1) has alternative translational start sites, resulting in two polypeptides, targeted to either mitochondria or the nucleus. RNAi-mediated rnh1 knockdown did not influence growth or viability of S2 cells, but compromised mtDNA integrity and copy number. rnh1 knockdown in intact flies also produced a phenotype of impaired mitochondrial function, characterized by respiratory chain deficiency, locomotor dysfunction, and decreased lifespan. Its overexpression in S2 cells resulted in cell lethality after 5-9 days, attributable to the nuclearly localized isoform. rnh1 knockdown and overexpression produced opposite effects on mtDNA replication intermediates. The most pronounced effects were seen in genome regions beyond the major replication pauses where the replication fork needs to progress through a gene cluster that is transcribed in the opposite direction. RNase H1 deficiency led to an accumulation of replication intermediates in these zones, abundant mtDNA molecules joined by four-way junctions, and species consistent with fork regression from the origin. These findings indicate replication stalling due to the presence of unprocessed RNA/DNA heteroduplexes, potentially leading to the degradation of collapsed forks or to replication restart by a mechanism involving strand invasion. Both mitochondrial RNA and DNA syntheses were affected by rnh1 knockdown, suggesting that RNase H1 also plays a role in integrating or coregulating these processes in Drosophila mitochondria.Peer reviewe

Extra-pair paternity explains cooperation in a bird species

In many social animals, females mate with multiple males, but the adaptive value of female extra-pair mating is not fully understood. Here, we tested whether male pied flycatchers (Ficedula hypoleuca) engaging in extra-pair copulations with neighboring females were more likely to assist their neighbors in antipredator defense. We found that extra-pair sires joined predator-mobbing more often, approached predators more closely, and attacked predators more aggressively than males without extra-pair offspring in the neighboring nest. Extra-pair mating may incentivize males to assist in nest defense because of the benefits that this cooperative behavior has on their total offspring production. For females, this mating strategy may help recruit more males to join in antipredator defense, offering better protection and ultimately improving reproductive success. Our results suggest a simple mechanism by which extra-pair mating can improve reproductive success in breeding birds. In summary, males siring extra-pair offspring in neighboring nests assist neighbors in antipredator defense more often than males without extra-pair offspring.publishedVersio

A Rolling Circle Replication Mechanism Produces Multimeric Lariats of Mitochondrial DNA in Caenorhabditis elegans

Mitochondrial DNA (mtDNA) encodes respiratory complex subunits essential to almost all eukaryotes; hence respiratory competence requires faithful duplication of this molecule. However, the mechanism(s) of its synthesis remain hotly debated. Here we have developed Caenorhabditis elegans as a convenient animal model for the study of metazoan mtDNA synthesis. We demonstrate that C. elegans mtDNA replicates exclusively by a phage-like mechanism, in which multimeric molecules are synthesized from a circular template. In contrast to previous mammalian studies, we found that mtDNA synthesis in the C. elegans gonad produces branched-circular lariat structures with multimeric DNA tails; we were able to detect multimers up to four mtDNA genome unit lengths. Further, we did not detect elongation from a displacement-loop or analogue of 7S DNA, suggesting a clear difference from human mtDNA in regard to the site(s) of replication initiation. We also identified cruciform mtDNA species that are sensitive to cleavage by the resolvase RusA; we suggest these four-way junctions may have a role in concatemer-to-monomer resolution. Overall these results indicate that mtDNA synthesis in C. elegans does not conform to any previously documented metazoan mtDNA replication mechanism, but instead are strongly suggestive of rolling circle replication, as employed by bacteriophages. As several components of the metazoan mitochondrial DNA replisome are likely phage-derived, these findings raise the possibility that the rolling circle mtDNA replication mechanism may be ancestral among metazoans.Peer reviewe

Mitochondrial Transcription Terminator Family Members mTTF and mTerf5 Have Opposing Roles in Coordination of mtDNA Synthesis

Peer reviewe

Food quality affects the expression of antimicrobial peptide genes upon simulated parasite attack in the larvae of greater wax moth

Predator-prey interactions are an important evolutionary force affecting the immunity of the prey. Parasitoids and mites pierce the cuticle of their prey, which respond by activating their immune system against predatory attacks. Immunity is a costly function for the organism, as it often competes with other life-history traits for limited nutrients. We tested whether the expression of antimicrobial peptides (AMP) of the larvae of the greater wax moth Galleria mellonella (L.) (Lepidoptera: Pyralidae) changes as a consequence of insertion of a nylon monofilament, which acts like a synthetic parasite. The treatment was done for larvae grown on a high-quality vs. a low-quality diet. The expression of Gloverin and 6-tox were upregulated in response to the insertion of the nylon monofilament. The expression of 6-tox, Cecropin-D, and Gallerimycin were significantly higher in the low-quality diet' group than in the high-quality diet' group. As food quality seems to affect AMP gene expression in G. mellonella larvae, it should always be controlled for in studies on bacterial and fungal infections in G. mellonella

Extra-pair paternity explains cooperation in a bird species

In many social animals, females mate with multiple males, but the adaptive value of female extra-pair mating is not fully understood. Here, we tested whether male pied flycatchers (Ficedula hypoleuca) engaging in extra-pair copulations with neighboring females were more likely to assist their neighbors in antipredator defense. We found that extra-pair sires joined predator-mobbing more often, approached predators more closely, and attacked predators more aggressively than males without extra-pair offspring in the neighboring nest. Extra-pair mating may incentivize males to assist in nest defense because of the benefits that this cooperative behavior has on their total offspring production. For females, this mating strategy may help recruit more males to join in antipredator defense, offering better protection and ultimately improving reproductive success. Our results suggest a simple mechanism by which extra-pair mating can improve reproductive success in breeding birds. In summary, males siring extra-pair offspring in neighboring nests assist neighbors in antipredator defense more often than males without extra-pair offspring

2DNAGE analysis of <i>C</i>. <i>elegans</i> mitochondrial DNA reveals prominent replication and recombination intermediates but no initiation bubbles.

<p>(A) Physical and transcriptional maps of the <i>Caenorhabditis elegans</i> mitochondrial genome, arbitrarily linearized for clarity. Arrows depict transcriptional orientation and relative lengths of protein coding genes (light grey arrows), large and small ribosomal RNA genes (dark grey arrows), and two NCRs (yellow and red bars). Hybridization probe locations are indicated by orange bars; see also Supplementary Information. (B) MtDNA isolated from a sucrose gradient-enriched mitochondrial preparation was restriction enzyme cleaved as indicated to generate 3.8 or 5 kb fragments that collectively cover the entire genome, subjected to 2DNAGE and probed to identify intermediates containing the 465 bp ‘major’ NCR (ClaI/ApaI digest; red circle); the 104 bp ‘minor’ NCR (BsrGI/ClaI digest; yellow circle); or a coding region only (ApaI/BsrGI digest). (C) A diagram of replication intermediate migration within 2DNAGE gels is depicted (counter-clockwise from lower right: 1n spot of linear monomer mtDNA fragments; Y-shaped replication forks; bubble-shaped initiation intermediates, in this case absent from the gels, hence depicted in red, with dotted line; cruciform recombination intermediates). Panels are representative of three independent experiments per fragment.</p

Advancing forks are engaged in strand-synchronous replication.

<p>MtDNA was treated with RNase H, S1 nuclease, or both, fractionated by 2DNAGE and blot-hybridized with a probe specific to the major-NCR, illustrated as in <a href="http://www.plosgenetics.org/article/info:doi/10.1371/journal.pgen.1004985#pgen.1004985.g001" target="_blank">Fig. 1B</a>. (A) untreated, MfeI-digested mtDNA (diagram at left); RNase H treatment diminishes replication intermediates, yet a full Y arc persists. Treatment by S1 nuclease alone does not alter migration of replication intermediates. A proportion of intermediates persist treatment with S1 nuclease after RNase H indicating a lack of RNA:DNA hybrid tracts in <i>C</i>. <i>elegans</i> mtDNA. (B) ImageJ-quantified mean hybridization intensity of the Y arc derived from the major NCR-containing region, relative to the monomer spot. See also <a href="http://www.plosgenetics.org/article/info:doi/10.1371/journal.pgen.1004985#pgen.1004985.s002" target="_blank">S2 Fig.</a> for similar analysis of the remainder of the genome.</p

<i>C</i>. <i>elegans</i> mtDNA forms lariat-shaped rolling circle replication intermediates.

<p>RNase I-treated mitochondrial nucleic acid was spread on parlodion-coated copper grids and visualized by TEM. (A) Frequency distribution of estimated strand-lengths of monomeric circular mtDNAs (Cir) and the circular portion of lariat mtDNAs (Lar) in kb. (B) Frequency distribution of estimated tail lengths of lariat mtDNAs, in kb. (C) Representative electron micrograph of a double-stranded DNA monomer circle. (D) Representative electron micrograph of an mtDNA lariat. (E) Multimeric lariat molecule with one genome unit-length circle (1n; 13.8 kb) with concatemeric linear tail (3.5n; 48.2 kb). (F) Higher magnification of the apparently double-stranded circle-tail junction. (G) Lariat with partial ssDNA structure consisting of a genome unit-length circle (1n; 13.8 kb) and concatemer tail (2.6n; 35.7 kb). Magnification of the single-stranded regions along the tail (H), as well as at the tail-circle junction (I); arrows indicate ssDNA. Scale bars, 0.2 μm. Data generated from three independent mtDNA isolations.</p