p53-dependent DNA repair during the DNA damage response requires actin nucleation by JMY.

The tumour suppressor p53 is a nuclear transcription factor with key roles during DNA damage to enable a variety of cellular responses including cell cycle arrest, apoptosis and DNA repair. JMY is an actin nucleator and DNA damage-responsive protein whose sub-cellular localisation is responsive to stress and during DNA damage JMY undergoes nuclear accumulation. To gain an understanding of the wider role for nuclear JMY in transcriptional regulation, we performed transcriptomics to identify JMY-mediated changes in gene expression during the DNA damage response. We show that JMY is required for effective regulation of key p53 target genes involved in DNA repair, including XPC, XRCC5 (Ku80) and TP53I3 (PIG3). Moreover, JMY depletion or knockout leads to increased DNA damage and nuclear JMY requires its Arp2/3-dependent actin nucleation function to promote the clearance of DNA lesions. In human patient samples a lack of JMY is associated with increased tumour mutation count and in cells results in reduced cell survival and increased sensitivity to DNA damage response kinase inhibition. Collectively, we demonstrate that JMY enables p53-dependent DNA repair under genotoxic stress and suggest a role for actin in JMY nuclear activity during the DNA damage response.

Fecal Microbiota Transplantation for Recurrent Clostridioides difficile Infection Associates With Functional Alterations in Circulating microRNAs.

BACKGROUND AND AIMS: The molecular mechanisms underlying successful fecal microbiota transplantation (FMT) for recurrent Clostridioides difficile infection (rCDI) remain poorly understood. The primary objective of this study was to characterize alterations in microRNAs (miRs) following FMT for rCDI. METHODS: Sera from 2 prospective multicenter randomized controlled trials were analyzed for miRNA levels with the use of the Nanostring nCounter platform and quantitative reverse-transcription (RT) polymerase chain reaction (PCR). In addition, rCDI-FMT and toxin-treated animals and ex vivo human colonoids were used to compare intestinal tissue and circulating miRs. miR inflammatory gene targets in colonic epithelial and peripheral blood mononuclear cells were evaluated by quantitative PCR (qPCR) and 3'UTR reporter assays. Colonic epithelial cells were used for mechanistic, cytoskeleton, cell growth, and apoptosis studies. RESULTS: miRNA profiling revealed up-regulation of 64 circulating miRs 4 and 12 weeks after FMT compared with screening, of which the top 6 were validated in the discovery cohort by means of RT-qPCR. In a murine model of relapsing-CDI, RT-qPCR analyses of sera and cecal RNA extracts demonstrated suppression of these miRs, an effect reversed by FMT. In mouse colon and human colonoids, C difficile toxin B (TcdB) mediated the suppressive effects of CDI on miRs. CDI dysregulated DROSHA, an effect reversed by FMT. Correlation analyses, qPCR ,and 3'UTR reporter assays revealed that miR-23a, miR-150, miR-26b, and miR-28 target directly the 3'UTRs of IL12B, IL18, FGF21, and TNFRSF9, respectively. miR-23a and miR-150 demonstrated cytoprotective effects against TcdB. CONCLUSIONS: These results provide novel and provocative evidence that modulation of the gut microbiome via FMT induces alterations in circulating and intestinal tissue miRs. These findings contribute to a greater understanding of the molecular mechanisms underlying FMT and identify new potential targets for therapeutic intervention in rCDI.

Site-specific effects of apolipoprotein E expression on diet-induced obesity and white adipose tissue metabolic activation.

Apolipoprotein E (APOE) has been strongly implicated in the development of diet induced obesity. In the present study, we investigated the contribution of brain and peripherally expressed human apolipoprotein E3 (APOE3), the most common human isoform, to diet induced obesity. In our studies APOE3 knock-in (Apoe3knock-in), Apoe-deficient (apoe-/-) and brain-specific expressing APOE3 (Apoe3brain) mice were fed western-type diet for 12week and biochemical analyses were performed. Moreover, AAV-mediated gene transfer of APOE3 to apoe-/- mice was employed, as a means to achieve APOE3 expression selectively in periphery, since peripherally expressed APOE does not cross blood brain barrier (BBB) or blood-cerebrospinal fluid barrier (BCSFB). Our data suggest a bimodal role of APOE3 in visceral white adipose tissue (WAT) mitochondrial metabolic activation that is highly dependent on its site of expression and independent of postprandial dietary lipid deposition. Our findings indicate that brain APOE3 expression is associated with a potent inhibition of visceral WAT mitochondrial oxidative phosphorylation, leading to significantly reduced substrate oxidation, increased fat accumulation and obesity. In contrast, peripherally expressed APOE3 is associated with a notable shift of substrate oxidation towards non-shivering thermogenesis in visceral WAT mitochondria, leading to resistance to obesity.

MicroRNA214 Is Associated With Progression of Ulcerative Colitis, and Inhibition Reduces Development of Colitis and Colitis-Associated Cancer in Mice.

BACKGROUND & AIMS: Persistent activation of the inflammatory response contributes to the development of inflammatory bowel diseases, which increase the risk of colorectal cancer. We aimed to identify microRNAs that regulate inflammation during the development of ulcerative colitis (UC) and progression to colitis-associated colon cancer (CAC). METHODS: We performed a quantitative polymerase chain reaction analysis to measure microRNAs in 401 colon specimens from patients with UC, Crohn's disease, irritable bowel syndrome, sporadic colorectal cancer, or CAC, as well as subjects without these disorders (controls); levels were correlated with clinical features and disease activity of patients. Colitis was induced in mice by administration of dextran sodium sulfate (DSS), and carcinogenesis was induced by addition of azoxymethane; some mice also were given an inhibitor of microRNA214 (miR214). RESULTS: A high-throughput functional screen of the human microRNAome found that miR214 regulated the activity of nuclear factor-κB. Higher levels of miR214 were detected in colon tissues from patients with active UC or CAC than from patients with other disorders or controls and correlated with disease progression. Bioinformatic and genome-wide profile analyses showed that miR214 activates an inflammatory response and is amplified through a feedback loop circuit mediated by phosphatase and tensin homolog (PTEN) and PDZ and LIM domain 2 (PDLIM2). Interleukin-6 induced signal transducer and activator of transcription 3 (STAT3)-mediated transcription of miR214. A miR214 chemical inhibitor blocked this circuit and reduced the severity of DSS-induced colitis in mice, as well as the number and size of tumors that formed in mice given azoxymethane and DSS. In fresh colonic biopsy specimens from patients with active UC, the miR214 inhibitor reduced inflammation by increasing levels of PDLIM2 and PTEN. CONCLUSIONS: Interleukin-6 up-regulates STAT3-mediated transcription of miR214 in colon tissues, which reduces levels of PDLIM2 and PTEN, increases phosphorylation of AKT, and activates nuclear factor-κB. The activity of this circuit correlates with disease activity in patients with UC and progression to colorectal cancer.