Characterization of mouse synaptic vesicle-2-associated protein (Msvop) specifically expressed in the mouse central nervous system

Unraveling astrocyte behavior in the space brain: Radiation response of primary astrocytes

Introduction

Exposure to space conditions during crewed long-term exploration missions can cause several health risks for astronauts. Space radiation, isolation and microgravity are major limiting factors. The role of astrocytes in cognitive disturbances by space radiation is unknown. Astrocytes' response toward low linear energy transfer (LET) X-rays and high-LET carbon (12C) and iron (56Fe) ions was compared to reveal possible effects of space-relevant high-LET radiation. Since astronauts are exposed to ionizing radiation and microgravity during space missions, the effect of simulated microgravity on DNA damage induction and repair was investigated.

Methods

Primary murine cortical astrocytes were irradiated with different doses of X-rays, 12C and 56Fe ions at the heavy ion accelerator GSI. DNA damage and repair (γH2AX, 53BP1), cell proliferation (Ki-67), astrocytes' reactivity (GFAP) and NF-κB pathway activation (p65) were analyzed by immunofluorescence microscopy. Cell cycle progression was investigated by flow cytometry of DNA content. Gene expression changes after exposure to X- rays were investigated by mRNA-sequencing. RT-qPCR for several genes of interest was performed with RNA from X-rays- and heavy-ion-irradiated astrocytes: Cdkn1a, Cdkn2a, Gfap, Tnf, Il1β, Il6, and Tgfβ1. Levels of the pro inflammatory cytokine IL-6 were determined using ELISA. DNA damage response was investigated after exposure to X-rays followed by incubation on a 2D clinostat to simulate the conditions of microgravity.

Results

Astrocytes showed distinct responses toward the three different radiation qualities. Induction of radiation-induced DNA double strand breaks (DSBs) and the respective repair was dose-, LET- and time-dependent. Simulated microgravity had no significant influence on DNA DSB repair. Proliferation and cell cycle progression was not affected by radiation qualities examined in this study. Astrocytes expressed IL-6 and GFAP with constitutive NF-κB activity independent of radiation exposure. mRNA sequencing of X-irradiated astrocytes revealed downregulation of 66 genes involved in DNA damage response and repair, mitosis, proliferation and cell cycle regulation.

Discussion

In conclusion, primary murine astrocytes are DNA repair proficient irrespective of radiation quality. Only minor gene expression changes were observed after X-ray exposure and reactivity was not induced. Co-culture of astrocytes with microglial cells, brain organoids or organotypic brain slice culture experiments might reveal whether astrocytes show a more pronounced radiation response in more complex network architectures in the presence of other neuronal cell types.

Temporal Cortex Microarray Analysis Revealed Impaired Ribosomal Biogenesis and Hyperactivity of the Glutamatergic System: An Early Signature of Asymptomatic Alzheimer's Disease

Pathogenic aging is regarded as asymptomatic AD when there is no cognitive deficit except for neuropathology consistent with Alzheimer's disease. These individuals are highly susceptible to developing AD. Braak and Braak's theory specific to tau pathology illustrates that the brain's temporal cortex region is an initiation site for early AD progression. So, the hub gene analysis of this region may reveal early altered biological cascades that may be helpful to alleviate AD in an early stage. Meanwhile, cognitive processing also drags its attention because cognitive impairment is the ultimate result of AD. Therefore, this study aimed to explore changes in gene expression of aged control, asymptomatic AD (AsymAD), and symptomatic AD (symAD) in the temporal cortex region. We used microarray data sets to identify differentially expressed genes (DEGs) with the help of the R programming interface. Further, we constructed the protein-protein interaction (PPI) network by performing the STRING plugin in Cytoscape and determined the hub genes via the CytoHubba plugin. Furthermore, we conducted Gene Ontology (GO) enrichment analysis via Bioconductor's cluster profile package. Resultant, the AsymAD transcriptome revealed the early-stage changes of glutamatergic hyperexcitability. Whereas the connectivity of major hub genes in this network indicates a shift from initially reduced rRNA biosynthesis in the AsymAD group to impaired protein synthesis in the symAD group. Both share the phenomenon of breaking tight junctions and others. In conclusion, this study offers new understandings of the early biological vicissitudes that occur in the brain before the manifestation of symAD and gives new promising therapeutic targets for early AD intervention.

Construction of Novel DNA Methylation-Based Prognostic Model to Predict Survival in Glioblastoma

Glioblastoma (GBM) is a most aggressive primary cancer in brain with poor prognosis. This study aimed to identify novel tumor biomarkers with independent prognostic values in GBMs. The DNA methylation profiles were downloaded from The Cancer Genome Atlas and Gene Expression Omnibus database. Differential methylated genes (DMGs) were screened from recurrent GBM samples using limma package in R software. Functional enrichment analysis was performed to identify major biological processes and signaling pathways. Furthermore, critical DMGs associated with the prognosis of GBM were screened according to univariate and multivariate cox regression analysis. A risk score-based prognostic model was constructed for these DMGs and prediction ability of this model was validated in training and validation data set. In total, 495 DMGs were identified between recurrent samples and disease-free samples, including 356 significantly hypermethylated and 139 hypomethylated genes. Functional and pathway items for these DMGs were mainly related to sensory organ development, neuroactive ligand-receptor interaction, pathways in cancer, etc. Five genes with abnormal methylation level were significantly correlated with prognosis according to survival analysis, such as ALX1, KANK1, NUDT12, SNED1, and SVOP. Finally, the risk model provided an effective ability for prognosis prediction both in training and validation data set. We constructed a novel prognostic model for survival prediction of GBMs. In addition, we identified five DMGs as critical prognostic biomarkers in GBM progression.

Characteristics of 29 novel atypical solute carriers of major facilitator superfamily type: evolutionary conservation, predicted structure and neuronal co-expression

Solute carriers (SLCs) are vital as they are responsible for a major part of the molecular transport over lipid bilayers. At present, there are 430 identified SLCs, of which 28 are called atypical SLCs of major facilitator superfamily (MFS) type. These are MFSD1, 2A, 2B, 3, 4A, 4B, 5, 6, 6 L, 7, 8, 9, 10, 11, 12, 13A, 14A and 14B; SV2A, SV2B and SV2C; SVOP and SVOPL; SPNS1, SPNS2 and SPNS3; and UNC93A and UNC93B1. We studied their fundamental properties, and we also included CLN3, an atypical SLC not yet belonging to any protein family (Pfam) clan, because its involvement in the same neuronal degenerative disorders as MFSD8. With phylogenetic analyses and bioinformatic sequence comparisons, the proteins were divided into 15 families, denoted atypical MFS transporter families (AMTF1-15). Hidden Markov models were used to identify orthologues from human to Drosophila melanogaster and Caenorhabditis elegans Topology predictions revealed 12 transmembrane segments (for all except CLN3), corresponding to the common MFS structure. With single-cell RNA sequencing and in situ proximity ligation assay on brain cells, co-expressions of several atypical SLCs were identified. Finally, the transcription levels of all genes were analysed in the hypothalamic N25/2 cell line after complete amino acid starvation, showing altered expression levels for several atypical SLCs.

Soy glyceollins regulate transcript abundance in the female mouse brain

Glyceollins (Glys), produced by soy plants in response to stress, have anti-estrogenic activity in breast and ovarian cancer cell lines in vitro and in vivo. In addition to known anti-estrogenic effects, Gly exhibits mechanisms of action not involving estrogen receptor (ER) signaling. To date, effects of Gly on gene expression in the brain are unknown. For this study, we implanted 17-β estradiol (E2) or placebo slow-release pellets into ovariectomized CFW mice followed by 11 days of exposure to Gly or vehicle i.p. injections. We then performed a microarray on total RNA extracted from whole-brain hemispheres and identified differentially expressed genes (DEGs) by a 2 × 2 factorial ANOVA with an false discovery rate (FDR) = 0.20. In total, we identified 33 DEGs with a significant E2 main effect, 5 DEGs with a significant Gly main effect, 74 DEGs with significant Gly and E2 main effects (but no significant interaction term), and 167 DEGs with significant interaction terms. Clustering across all DEGs revealed that transcript abundances were similar between the E2 + Gly and E2-only treatments. However, gene expression after Gly-only treatment was distinct from both of these treatments and was generally characterized by higher transcript abundance. Collectively, our results suggest that whether Gly acts in the brain through ER-dependent or ER-independent mechanisms depends on the target gene.

Hippocampal CA3 transcriptome signature correlates with initial precipitating injury in refractory mesial temporal lobe epilepsy

BACKGROUND

Prolonged febrile seizures constitute an initial precipitating injury (IPI) commonly associated with refractory mesial temporal lobe epilepsy (RMTLE). In order to investigate IPI influence on the transcriptional phenotype underlying RMTLE we comparatively analyzed the transcriptomic signatures of CA3 explants surgically obtained from RMTLE patients with (FS) or without (NFS) febrile seizure history. Texture analyses on MRI images of dentate gyrus were conducted in a subset of surgically removed sclerotic hippocampi for identifying IPI-associated histo-radiological alterations.

METHODOLOGY/PRINCIPAL FINDINGS

DNA microarray analysis revealed that CA3 global gene expression differed significantly between FS and NFS subgroups. An integrative functional genomics methodology was used for characterizing the relations between GO biological processes themes and constructing transcriptional interaction networks defining the FS and NFS transcriptomic signatures and its major gene-gene links (hubs). Co-expression network analysis showed that: i) CA3 transcriptomic profiles differ according to the IPI; ii) FS distinctive hubs are mostly linked to glutamatergic signalization while NFS hubs predominantly involve GABAergic pathways and neurotransmission modulation. Both networks have relevant hubs related to nervous system development, what is consistent with cell genesis activity in the hippocampus of RMTLE patients. Moreover, two candidate genes for therapeutic targeting came out from this analysis: SSTR1, a relevant common hub in febrile and afebrile transcriptomes, and CHRM3, due to its putative role in epilepsy susceptibility development. MRI texture analysis allowed an overall accuracy of 90% for pixels correctly classified as belonging to FS or NFS groups. Histological examination revealed that granule cell loss was significantly higher in FS hippocampi.

CONCLUSIONS/SIGNIFICANCE

CA3 transcriptional signatures and dentate gyrus morphology fairly correlate with IPI in RMTLE, indicating that FS-RMTLE represents a distinct phenotype. These findings may shed light on the molecular mechanisms underlying refractory epilepsy phenotypes and contribute to the discovery of novel specific drug targets for therapeutic interventions.