Early life adversity targets the transcriptional signature of hippocampal NG2+ glia and affects voltage gated sodium (Nav) channels properties.

The precise mechanisms underlying the detrimental effects of early life adversity (ELA) on adult mental health remain still elusive. To date, most studies have exclusively targeted neuronal populations and not considered neuron-glia crosstalk as a crucially important element for the integrity of stress-related brain function. Here, we have investigated the impact of ELA, in the form of a limited bedding and nesting material (LBN) paradigm, on a glial subpopulation with unique properties in brain homeostasis, the NG2+ cells. First, we have established a link between maternal behavior, activation of the offspring's stress response and heterogeneity in the outcome to LBN manipulation. We further showed that LBN targets the hippocampal NG2+ transcriptome with glucocorticoids being an important mediator of the LBN-induced molecular changes. LBN altered the NG2+ transcriptome and these transcriptional effects were correlated with glucocorticoids levels. The functional relevance of one LBN-induced candidate gene, Scn7a, could be confirmed by an increase in the density of voltage-gated sodium (Nav) channel activated currents in hippocampal NG2+ cells. Scn7a remained upregulated until adulthood in LBN animals, which displayed impaired cognitive performance. Considering that Nav channels are important for NG2+ cell-to-neuron communication, our findings provide novel insights into the disruption of this process in LBN mice.

Lymphoblast-derived integration-free iPSC line AD-TREM2-3 from a 74 year-old Alzheimer's disease patient expressing the TREM2 p.R47H variant.

Human lymphoblast cells from a male diagnosed with Alzheimer's disease (AD) expressing the TREM2 p.R47H variant were used to generate integration-free induced pluripotent stem cells (iPSCs) by over-expressing episomal-based plasmids harbouring OCT4, SOX2, KLF4, LIN28, L-MYC and p53 shRNA. The derived iPSC line - AD-TREM2-3 was defined as pluripotent based on (i) expression of pluripotency-associated markers (ii) embryoid body-based differentiation into cell types representative of the three germ layers and (iii) the similarity between the transcriptome of the iPSC line and the human embryonic stem cell line H1 with a Pearson correlation of 0.940.

Lymphoblast-derived integration-free iPSC line AD-TREM2-1 from a 67year-old Alzheimer's disease patient expressing the TREM2 p.R47H variant.

Human lymphoblast cells from a male diagnosed with Alzheimer's disease (AD) expressing the TREM2 p.R47H variant were used to generate integration-free induced pluripotent stem cells (iPSCs) by over-expressing episomal-based plasmids harbouring OCT4, SOX2, NANOG, LIN28, c-MYC and L-MYC. AD-TREM2-1 was defined as pluripotent based on (i) expression of pluripotency-associated markers (ii) embryoid body-based differentiation into cell types representative of the three germ layers and (iii) the similarity between the transcriptome of the iPSC line and the human embryonic stem cell line H1 with a Pearson correlation of 0.947.

Re-Arrangements in the Cytoplasmic Distribution of Small RNAs Following the Maternal-to-Zygotic Transition in Drosophila Embryos.

Small ribonucleic acids (RNAs) are known to regulate gene expression during early development. However, the dynamics of interaction between small RNAs and polysomes during this process is largely unknown. To investigate this phenomenon, 0-1 h and 7-8 h Drosophila melanogaster embryos were fractionated on sucrose density gradients into four fractions based on A254 reading (1) translationally inactive messenger ribonucleoprotein (mRNP), (2) 60S, (3) monosome, and (4) polysome. Comparative analysis of deep-sequencing reads from fractionated and un-fractionated 0-1 h and 7-8 h embryos revealed development-specific co-sedimentation pattern of small RNAs with the cellular translation machinery. Although most micro RNAs (miRNAs) did not have a specific preference for any state of the translational machinery, we detected fraction-specific enrichment of a few miRNAs such as dme-miR-1-3p, -184-3p, 5-5p and 263-5p. More interestingly, we observed changes in the subcellular location of a subset of miRNAs in fractionated embryos despite no measurable difference in their amount in unfractionated embryos. Transposon-derived endo small interfering RNAs (siRNAs) were over-expressed in 7-8 h embryos and associated mainly with the mRNP fraction. In contrast, transposon-derived PIWI-interacting RNAs (piRNA), which were more abundant in 0-1 h embryos, co-sedimented primarily with the polysome fractions. These results suggest that there appears to be a complex interplay among the small RNAs with respect to their polysome-cosedimentation pattern during early development in Drosophila melanogaster.

Differentially Expressed tRNA-Derived Small RNAs Co-Sediment Primarily with Non-Polysomal Fractions in Drosophila.

Recent studies point to the existence of poorly characterized small regulatory RNAs generated from mRNAs, rRNAs and tRNAs. To explore the subcellular location of tRNA-derived small RNAs, 0-1 and 7-8 h Drosophila embryos were fractionated on sucrose density gradients. Analysis of 12,553,921 deep-sequencing reads from unfractionated and fractionated Drosophila embryos has revealed that tRFs, which are detected mainly from the 5'ends of tRNAs, co-sediment with the non-polysomal fractions. Interestingly, the expression levels of a subset of tRFs change temporally following the maternal-to-zygotic transition in embryos. We detected non-polysomal association of tRFs in S2 cells as well. Differential tRF expression pattern points to developmental significance at the organismal level. These results suggest that tRFs are associated primarily with the non-polysomal complexes in Drosophila embryos and S2 cells.

Oligodendrocyte precursor cells synthesize neuromodulatory factors.

NG2 protein-expressing oligodendrocyte progenitor cells (OPC) are a persisting and major glial cell population in the adult mammalian brain. Direct synaptic innervation of OPC by neurons throughout the brain together with their ability to sense neuronal network activity raises the question of additional physiological roles of OPC, supplementary to generating myelinating oligodendrocytes. In this study we investigated whether OPC express neuromodulatory factors, typically synthesized by other CNS cell types. Our results show that OPC express two well-characterized neuromodulatory proteins: Prostaglandin D2 synthase (PTGDS) and neuronal Pentraxin 2 (Nptx2/Narp). Expression levels of the enzyme PTGDS are influenced in cultured OPC by the NG2 intracellular region which can be released by cleavage and localizes to glial nuclei upon transfection. Furthermore PTGDS mRNA levels are reduced in OPC from NG2-KO mouse brain compared to WT cells after isolation by cell sorting and direct analysis. These results show that OPC can contribute to the expression of these proteins within the CNS and suggest PTGDS expression as a downstream target of NG2 signaling.