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Microglia and complement can mediate neurodegeneration in Alzheimer’s disease (AD). By integrative multi-omics analysis, here we show that astrocytic and microglial proteins are increased in TauP301S synapse fractions with age and in a C1q-dependent manner. In addition to microglia, we identified that astrocytes contribute substantially to synapse elimination in TauP301S hippocampi. Notably, we found relatively more excitatory synapse marker proteins in astrocytic lysosomes, whereas microglial lysosomes contained more inhibitory synapse material. C1q deletion reduced astrocyte–synapse association and decreased astrocytic and microglial synapses engulfment in TauP301S mice and rescued synapse density. Finally, in an AD mouse model that combines β-amyloid and Tau pathologies, deletion of the AD risk gene Trem2 impaired microglial phagocytosis of synapses, whereas astrocytes engulfed more inhibitory synapses around plaques. Together, our data reveal that astrocytes contact and eliminate synapses in a C1q-dependent manner and thereby contribute to pathological synapse loss and that astrocytic phagocytosis can compensate for microglial dysfunction.

Concomitant activation of the Wnt pathway and suppression of Mapk signalling by two small molecule inhibitors (2i) in the presence of leukaemia inhibitory factor (LIF) (hereafter termed 2i/L) induces a naive state in mouse embryonic stem (ES) cells that resembles the inner cell mass (ICM) of the pre-implantation embryo. Since the ICM exists only transiently in vivo, it remains unclear how sustained propagation of naive ES cells in vitro affects their stability and functionality. Here we show that prolonged culture of male mouse ES cells in 2i/L results in irreversible epigenetic and genomic changes that impair their developmental potential. Furthermore, we find that female ES cells cultured in conventional serum plus LIF medium phenocopy male ES cells cultured in 2i/L. Mechanistically, we demonstrate that the inhibition of Mek1/2 is predominantly responsible for these effects, in part through the downregulation of DNA methyltransferases and their cofactors. Finally, we show that replacement of the Mek1/2 inhibitor with a Src inhibitor preserves the epigenetic and genomic integrity as well as the developmental potential of ES cells. Taken together, our data suggest that, although short-term suppression of Mek1/2 in ES cells helps to maintain an ICM-like epigenetic state, prolonged suppression results in irreversible changes that compromise their developmental potential.

Profound global loss of DNA methylation is a hallmark of many cancers. One potential consequence of this is the reactivation of transposable elements (TEs) which could stimulate the immune system via cell-intrinsic antiviral responses. Here, we develop REdiscoverTE, a computational method for quantifying genome-wide TE expression in RNA sequencing data. Using The Cancer Genome Atlas database, we observe increased expression of over 400 TE subfamilies, of which 262 appear to result from a proximal loss of DNA methylation. The most recurrent TEs are among the evolutionarily youngest in the genome, predominantly expressed from intergenic loci, and associated with antiviral or DNA damage responses. Treatment of glioblastoma cells with a demethylation agent results in both increased TE expression and de novo presentation of TE-derived peptides on MHC class I molecules. Therapeutic reactivation of tumor-specific TEs may synergize with immunotherapy by inducing inflammation and the display of potentially immunogenic neoantigens., Treatment with demethylation agents can reactivate transposable elements. Here in glioblastoma, the authors also show that this is accompanied by de novo presentation of TE-derived peptides on MHC class I molecules.

The effect of an oxygen-carrying perfluorochemical emulsion on bleomycin antitumor activity and pulmonary toxicity was examined. Fluosol-DA (0.3 ml/mouse, i.v.), combined with bleomycin (10 or 15 mg/kg, i.p.) and a 2 h exposure to 95% oxygen (BFO) increased by five- to six-fold the tumor growth delay of FSaIIC fibrosarcoma compared to bleomycin alone (B). Only a slight increase in tumor growth delay was noted with the incomplete combinations of bleomycin and O2 (BO) and bleomycin and Fluosol-DA (BF). When bleomycin (10 mg/kg) was co-administered with 0.3 ml Fluosol-DA and 95% O2, cell survival was reduced ten-fold compared to that seen with bleomycin alone. In contrast, the surviving fraction of cells obtained from FSaIIC tumors treated in vivo indicated that 0.3 ml Fluosol-DA per mouse or a 2 h exposure to 95% O2 did not markedly alter the effects of bleomycin alone. The pulmonary effects of the BFO combination were assessed during the course of the therapy by bronchoalveolar lavage (BAL) analysis and pulmonary hydroxyproline (OH-Pro) content. Mice treated with this combination had a 20-fold increase in total numbers of cells obtained in the BAL compared to control animals. An increased cellularity in the lungs was also seen morphologically. The composition of the cells in the lavage fluid was altered after BFO but not BO treatment and reflected a neutrophilic influx. Furthermore, total protein recovered in the BAL fluid was increased 5-fold in the BFO treatment group compared to that in the control mice. Pulmonary OH-Pro, an index of collagen and fibrosis, was unaffected acutely after three treatments of either BFO or BO compared to control mice. Thus, Fluosol-DA and O2 can enhance the antitumor activity of bleomycin. The increased pulmonary cellularity suggests that this combination may also have adverse effects on lung tissue.