Single cell molecular alterations reveal target cells and pathways of conditioned fear memory

Astrocytic CREB in Nucleus Accumbens Promotes Susceptibility to Chronic Stress

BACKGROUND

Increasing evidence implicates astrocytes in stress and depression in both rodent models and human major depressive disorder. Despite this, little is known about the transcriptional responses to stress of astrocytes within the nucleus accumbens (NAc), a key brain reward region, and their influence on behavioral outcomes.

METHODS

We used whole-cell sorting, RNA sequencing, and bioinformatic analyses to investigate the NAc astrocyte transcriptome in male mice in response to chronic social defeat stress (CSDS). Immunohistochemistry was used to determine stress-induced changes in astrocytic CREB (cAMP response element binding protein) within the NAc. Finally, astrocytic regulation of depression-like behavior was investigated using viral-mediated manipulation of CREB in combination with CSDS.

RESULTS

We found a robust transcriptional response in NAc astrocytes to CSDS in stressed mice, with changes seen in both stress-susceptible and stress-resilient animals. Bioinformatic analysis revealed CREB, a transcription factor widely studied in neurons, as one of the top-predicted upstream regulators of the NAc astrocyte transcriptome, with opposite activation states implicated in resilient versus susceptible mice. This bioinformatic deduction was confirmed at the protein level with immunohistochemistry. Moreover, NAc astrocyte morphological complexity correlated with CREB activation and was reduced selectively in astrocytes of resilient mice. Viral overexpression of CREB selectively in NAc astrocytes promoted susceptibility to chronic stress.

CONCLUSIONS

Together, our data demonstrate that the astrocyte transcriptome responds robustly to CSDS and that transcriptional regulation in astrocytes contributes to depressive-like behaviors. A better understanding of transcriptional regulation in astrocytes may reveal unknown molecular mechanisms underlying neuropsychiatric disorders.

Transthyretin, a novel prognostic marker of POCD revealed by time-series RNA-sequencing analysis

Postoperative cognitive dysfunction (POCD) is defined as a declined cognition, measured by neuropsychological tests, that persists for months or even longer after surgery. Heterogeneities in the diagnosis of POCD usually involve differences in the test batteries, the cutoffs, and the timing of assessments. Although peripheral and CSF markers of neuroinflammation have been shown to correlate with increased risk of POCD, most of them are non-specific and cannot be used for POCD diagnosis. These factors hampered the understanding of the pathogenesis of POCD as well as the development of effective preventions/treatments. In this study, we found Ttr in a panel of potential POCD biomarkers identified using time-series analysis of the transcriptomes and proteomes of the hippocampi of POCD mice that diagnosed on individual basis with composite Z-scores of test batteries consisting of Y maze and open field test. Compared with their counterparts without POCD, the levels of Ttr were significantly lower in the peripheral circulation as well as in the hippocampi of the mice developed POCD at all indicated time points after surgery. The levels of peripheral TTR in human patients with delayed neurocognitive recovery were found to be reduced at 24 h after abdominal surgery, compared with those who did not. Endogenous expression of Ttr was verified in microglia cells both in vitro and in vivo. Results of in vitro assay indicated a potential role of Ttr in ameliorating LPS-induced microglial priming and protecting the differentiation of oligodendrocyte progenitor cells (OPCs) in proinflammatory microenvironment, which was one of the determinant factors in regulating the pathological progression of POCD.

A review and analysis of key biomarkers in Alzheimer's disease

Alzheimer's disease (AD) is a progressive neurodegenerative disorder that affects over 50 million elderly individuals worldwide. Although the pathogenesis of AD is not fully understood, based on current research, researchers are able to identify potential biomarker genes and proteins that may serve as effective targets against AD. This article aims to present a comprehensive overview of recent advances in AD biomarker identification, with highlights on the use of various algorithms, the exploration of relevant biological processes, and the investigation of shared biomarkers with co-occurring diseases. Additionally, this article includes a statistical analysis of key genes reported in the research literature, and identifies the intersection with AD-related gene sets from databases such as AlzGen, GeneCard, and DisGeNet. For these gene sets, besides enrichment analysis, protein-protein interaction (PPI) networks utilized to identify central genes among the overlapping genes. Enrichment analysis, protein interaction network analysis, and tissue-specific connectedness analysis based on GTEx database performed on multiple groups of overlapping genes. Our work has laid the foundation for a better understanding of the molecular mechanisms of AD and more accurate identification of key AD markers.

Astrocytic CREB in nucleus accumbens promotes susceptibility to chronic stress

Background

Increasing evidence implicates astrocytes in stress and depression in both rodent models and human Major Depressive Disorder (MDD). Despite this, little is known about the transcriptional responses to stress of astrocytes within the nucleus accumbens (NAc), a key brain reward region, and their influence on behavioral outcomes.

Methods

We used whole cell sorting, RNA-sequencing, and bioinformatic analyses to investigate the NAc astrocyte transcriptome in male mice in response to chronic social defeat stress (CSDS). Immunohistochemistry was used to determine stress-induced changes in astrocytic CREB within the NAc. Finally, astrocytic regulation of depression-like behavior was investigated using viral-mediated manipulation of CREB in combination with CSDS.

Results

We found a robust transcriptional response in NAc astrocytes to CSDS in stressed mice, with changes seen in both stress-susceptible and stress-resilient animals. Bioinformatic analysis revealed CREB, a transcription factor widely studied in neurons, as one of the top-predicted upstream regulators of the NAc astrocyte transcriptome, with opposite activation states seen in resilient versus susceptible mice. This bioinformatic result was confirmed at the protein level with immunohistochemistry. Viral overexpression of CREB selectively in NAc astrocytes promoted susceptibility to chronic stress.

Conclusions

Together, our data demonstrate that the astrocyte transcriptome responds robustly to CSDS and, for the first time, that transcriptional regulation in astrocytes contributes to depressive-like behaviors. A better understanding of transcriptional regulation in astrocytes may reveal unknown molecular mechanisms underlying neuropsychiatric disorders.