Yim, A. K. Y. | Search bioRxiv

bioRxiv2018

Single cell RNAseq uncovers a robust transcriptional response to morphine by oligodendrocytes

Molecular and behavioral responses to opioids are thought to be primarily mediated by neurons, although there is accumulating evidence that other cell types also play a role in drug addiction. To investigate cell-type-specific opioid responses, we performed single-cell RNA sequencing of the nucleus accumbens of mice following acute morphine treatment. Differential expression analysis uncovered robust morphine-dependent changes in gene expression in oligodendrocytes. We examined the expression of selected genes, including Cdkn1a and Sgk1, by FISH, confirming their induction by morphine in oligodendrocytes. Further analysis using RNAseq of FACS-purified oligodendrocytes revealed a large cohort of morphine-regulated genes. Importantly, the affected genes are enriched for roles in cellular pathways intimately linked to oligodendrocyte maturation and myelination, including the unfolded protein response. Altogether, our data shed light on a novel, morphine-dependent transcriptional response by oligodendrocytes that may contribute to the myelination defects observed in human opioid addicts.

neuroscience↗

bioRxiv2017

Differential Brd4-bound enhancers drive critical sex differences in glioblastoma

Sex can be an important determinant of cancer phenotype, and exploring sex-biased tumor biology holds promise for identifying novel therapeutic targets and new approaches to cancer treatment. In an established isogenic murine model of glioblastoma, we discovered correlated transcriptome-wide sex differences in gene expression, H3K27ac marks, large Brd4-bound enhancer usage, and Brd4 localization to Myc and p53 genomic binding sites. These sex-biased gene expression patterns were also evident in human glioblastoma stem cells (GSCs). These observations led us to hypothesize that Brd4-bound enhancers might underlie sex differences in stem cell function and tumorigenicity in GBM. We found that male and female GBM cells exhibited opposing responses to pharmacological or genetic inhibition of Brd4. Brd4 knockdown or pharmacologic inhibition decreased male GBM cell clonogenicity and in vivo tumorigenesis, while increasing both in female GBM cells. These results were validated in male and female patient-derived GBM cell lines. Furthermore, analysis of the Cancer Therapeutic Response Portal of human GBM samples segregated by sex revealed that male GBM cells are significantly more sensitive to BET inhibitors than are female cells. Thus, for the first time, Brd4 activity is revealed to drive a sex differences in stem cell and tumorigenic phenotype, resulting in diametrically opposite responses to BET inhibition in male and female GBM cells. This has important implications for the clinical evaluation and use of BET inhibitors. SignificanceConsistent sex differences in incidence and outcome have been reported in numerous cancers including brain tumors. GBM, the most common and aggressive primary brain tumor, occurs with higher incidence and shorter survival in males compared to females. Brd4 is essential for regulating transcriptome-wide gene expression and specifying cell identity, including that of GBM. We report that sex-biased Brd4 activity drive sex differences in GBM and render male and female tumor cells differentially sensitive to BET inhibitors. The observed sex differences in BETi treatment strongly indicate that sex differences in disease biology translate into sex differences in therapeutic responses. This has critical implications for clinical use of BET inhibitors further affirming the importance of inclusion of sex as a biological variable.

genomics↗