Transposable elements (TEs) are mobile genetic elements, highly enriched in heterochromatin, that constitute a large percentage of the DNA content of eukaryotic genomes. Aging in Drosophila melanogaster is characterized by loss of repressive heterochromatin structure and loss of silencing of reporter genes in constitutive heterochromatin regions. Using next-generation sequencing, we found that transcripts of many genes native to heterochromatic regions and TEs increased with age in fly heads and fat bodies. A dietary restriction regimen, known to extend life span, repressed the age-related increased expression of genes located in heterochromatin, as well as TEs. We also observed a corresponding age-associated increase in TE transposition in fly fat body cells that was delayed by dietary restriction. Furthermore, we found that manipulating genes known to affect heterochromatin structure, including overexpression of Sir2, Su(var)3-9, and Dicer-2, as well as decreased expression of Adar, mitigated age-related increases in expression of TEs. Increasing expression of either Su(var)3-9 or Dicer-2 also led to an increase in life span. Mutation of Dicer-2 led to an increase in DNA double-strand breaks. Treatment with the reverse transcriptase inhibitor 3TC resulted in decreased TE transposition as well as increased life span in TE-sensitized Dicer-2 mutants. Together, these data support the retrotransposon theory of aging, which hypothesizes that epigenetically silenced TEs become deleteriously activated as cellular defense and surveillance mechanisms break down with age. Furthermore, interventions that maintain repressive heterochromatin and preserve TE silencing may prove key to preventing damage caused by TE activation and extending healthy life span.aging | heterochromatin | transposable elements | dietary restriction | silencing

SUMMARY Insulators are multi-protein-DNA complexes thought to affect gene expression by mediating inter- and intra-chromosomal interactions. Drosophila insulators contain specific DNA binding proteins plus common components, such as CP190, that facilitate these interactions. Here we examine changes in the distribution of Drosophila insulator proteins during the heat-shock and ecdysone responses. We find that CP190 recruitment to insulator sites is the main regulatable step in controlling insulator function during heat shock. In contrast, both CP190 and DNA binding protein recruitment are regulated during the ecdysone response. CP190 is necessary to stabilize specific chromatin loops and for proper activation of transcription of genes regulated by this hormone. These findings suggest that cells may regulate recruitment of insulator proteins to the DNA in order to activate insulator activity at specific sites and create distinct patterns of nuclear organization that are necessary to achieve proper gene expression in response to different stimuli.

In gonadal tissues, the Piwi-interacting (piRNA) pathway preserves genomic integrity by employing 23–29 nucleotide (nt) small RNAs complexed with argonaute proteins to suppress parasitic mobile sequences of DNA called transposable elements (TEs). Although recent evidence suggests that the piRNA pathway may be present in select somatic cells outside the gonads, the role of a non-gonadal somatic piRNA pathway is not well characterized. Here we report a functional somatic piRNA pathway in the adult Drosophila fat body including the presence of the piRNA effector protein Piwi and canonical 23–29 nt long TE-mapping piRNAs. The piwi mutants exhibit depletion of fat body piRNAs, increased TE mobilization, increased levels of DNA damage and reduced lipid stores. These mutants are starvation sensitive, immunologically compromised and short-lived, all phenotypes associated with compromised fat body function. These findings demonstrate the presence of a functional non-gonadal somatic piRNA pathway in the adult fat body that affects normal metabolism and overall organismal health.

A multi-level ilioinguinal-iliohypogastric nerve block technique can reduce the amount of systemic morphine required to control post-Cesarean delivery pain but this reduction was not associated with a reduction of opioid related adverse effects in our study group.

Heterochromatin formation drives epigenetic mechanisms associated with silenced gene expression. Repressive heterochromatin is established through the RNA interference pathway, triggered by double-stranded RNAs that can be modified via RNA editing. However, the biological consequences of such modifications remain enigmatic. Here we show that RNA editing regulates heterochromatic gene silencing in Drosophila. We utilize the binding activity of an RNA editing enzyme to visualize the in vivo production of a long double-stranded RNA trigger mediated by Hoppel transposable elements. Using homologous recombination, we delete this trigger, dramatically altering heterochromatic gene silencing and chromatin architecture. Furthermore, we show that the trigger RNA is edited, serves as a key regulator of chromatin state, and that dADAR auto-editing generates a natural suppressor of gene silencing. Lastly, systemic differences in RNA editing activity generates inter-individual variation in silencing state within a population. Our data reveal a global role for RNA editing in regulating gene expression.

Glucocorticoids influence cell proliferation and differentiation in the lung. We examined the expression of the glucocorticoid receptor (GR) gene in urethan-induced mouse lung tumors and transformed lung cell lines to determine whether any altered responsiveness to these steroids is involved in the neoplastic development of some lung tumors. We find that a GR mRNA of similar size and amount is expressed in both normal lung and urethan-induced lung tumors. The K-ras gene is activated in urethan-induced lung adenomas and transformed lung cell lines. Both alveolar and papillary lung adenomas express slightly elevated levels of K-ras mRNA and similar levels of H-ras mRNA, but variable levels of c-myc mRNA, GR and K-ras mRNAs are concurrently expressed in a cyclic manner during the proliferation of nontransformed C10 and transformed A5 lung cell lines. Treatment of the C10 cells with dexamethasone (Dex) results in the inhibition of cell proliferation and the down-regulation of both the GR and K-ras mRNA. Dex treatment also down-regulated GR mRNA levels in A5 and LM2 cells, but no inhibitory effect was observed on K-ras mRNA levels or cell proliferation. These results suggest that glucocorticoids can inhibit K-ras expression in nontransformed lung cells. Although transformed lung cells respond to the steroid by down-regulation of the GR, the presence of an activated K-ras allele may override the inhibitory effects of these hormones on cell proliferation.

Amateur wrestling at the high school and collegiate level in the United States often involves exercise and thermal dehydration as well as food and fluid restriction to "make weight". Available evidence suggests this is the opposite of what is optimal for high-intensity exercise performance. A high-intensity taper will substantially improve performance when conducted after a period of high-volume high intensity training. Additionally, dehydration of approximately 3-4% of body weight will most definitely impair muscular endurance during high-intensity exercise although it likely will not impair maximal muscular strength or power. Even more gradual weight loss practices over a few days, which result in a reduction of body weight by approximately 3.3 to 6% will result in impaired performance as assessed by wrestling specific tests. It would seem of paramount importance for wrestlers to maintain a high-carbohydrate diet of approximately 8-10 g carbohydrate/kg body weight/day to maintain training intensity and optimize performance during individual matches and tournaments. Thus, the evidence would suggest that, prior to competition, collegiate wrestlers should be: 1) tapered, 2) in the euhydrated state, and 3) have ingested a high carbohydrate diet, rather than undergo rapid weight loss prior to competition.

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