A Potential Regulatory Role for Intronic microRNA-338-3p for Its Host Gene Encoding Apoptosis-Associated Tyrosine Kinase

MicroRNAs (miRNAs) are important gene regulators that are abundantly expressed in both the developing and adult mammalian brain. These non-coding gene transcripts are involved in post-transcriptional regulatory processes by binding to specific target mRNAs. Approximately one third of known miRNA genes are located within intronic regions of protein coding and non-coding regions, and previous studies have suggested a role for intronic miRNAs as negative feedback regulators of their host genes. In the present study, we monitored the dynamic gene expression changes of the intronic miR-338-3p and miR-338-5p and their host gene Apoptosis-associated Tyrosine Kinase (AATK) during the maturation of rat hippocampal neurons. This revealed an uncorrelated expression pattern of mature miR-338 strands with their host gene. Sequence analysis of the 3′ untranslated region (UTR) of rat AATK mRNA revealed the presence of two putative binding sites for miR-338-3p. Thus, miR-338-3p may have the capacity to modulate AATK mRNA levels in neurons. Transfection of miR-338-3p mimics into rat B35 neuroblastoma cells resulted in a significant decrease of AATK mRNA levels, while the transfection of synthetic miR-338-5p mimics did not alter AATK levels. Our results point to a possible molecular mechanism by which miR-338-3p participates in the regulation of its host gene by modulating the levels of AATK mRNA, a kinase which plays a role during differentiation, apoptosis and possibly in neuronal degeneration

Single-cell molecular profiling of all three components of the HPA axis reveals adrenal ABCB1 as a regulator of stress adaptation

Chronic activation and dysregulation of the neuroendocrine stress response have severe physiological and psychological consequences, including the development of metabolic and stress-related psychiatric disorders. We provide the first unbiased, cell type-specific, molecular characterization of all three components of the hypothalamic-pituitary-adrenal axis, under baseline and chronic stress conditions. Among others, we identified a previously unreported subpopulation of Abcb1b+ cells involved in stress adaptation in the adrenal gland. We validated our findings in a mouse stress model, adrenal tissues from patients with Cushing's syndrome, adrenocortical cell lines, and peripheral cortisol and genotyping data from depressed patients. This extensive dataset provides a valuable resource for researchers and clinicians interested in the organism's nervous and endocrine responses to stress and the interplay between these tissues. Our findings raise the possibility that modulating ABCB1 function may be important in the development of treatment strategies for patients suffering from metabolic and stress-related psychiatric disorders

Sex shapes cell-type-specific transcriptional signatures of stress exposure in the mouse hypothalamus

Summary: Stress-related psychiatric disorders and the stress system show prominent differences between males and females, as well as strongly divergent transcriptional changes. Despite several proposed mechanisms, we still lack the understanding of the molecular processes at play. Here, we explore the contribution of cell types to transcriptional sex dimorphism using single-cell RNA sequencing. We identify cell-type-specific signatures of acute restraint stress in the paraventricular nucleus of the hypothalamus, a central hub of the stress response, in male and female mice. Further, we show that a history of chronic mild stress alters these signatures in a sex-specific way, and we identify oligodendrocytes as a major target for these sex-specific effects. This dataset, which we provide as an online interactive app, offers the transcriptomes of thousands of individual cells as a molecular resource for an in-depth dissection of the interplay between cell types and sex on the mechanisms of the stress response

miR-323a regulates ERBB4 and is involved in depression.

International audienceMajor depressive disorder (MDD) is a complex and debilitating illness whose etiology remains unclear. Small RNA molecules, such as micro RNAs (miRNAs) have been implicated in MDD, where they display differential expression in the brain and the periphery. In this study, we quantified miRNA expression by small RNA sequencing in the anterior cingulate cortex and habenula of individuals with MDD and psychiatrically-healthy controls. Thirty-two miRNAs showed significantly correlated expression between the two regions (False Discovery Rate < 0.05), of which four, miR-204-5p, miR-320b, miR-323a-3p, and miR-331-3p, displayed upregulated expression in MDD. We assessed the expression of predicted target genes of differentially expressed miRNAs in the brain, and found that the expression of erb-b2 receptor tyrosine kinase 4 (ERBB4), a gene encoding a neuregulin receptor, was downregulated in both regions, and was influenced by miR-323a-3p in vitro. Finally, we assessed the effects of manipulating miRNA expression in the mouse ACC on anxiety- and depressive-like behaviors. Mice in which miR-323-3p was overexpressed or knocked-down displayed increased and decreased emotionality, respectively. Additionally, these mice displayed significantly downregulated and upregulated expression of Erbb4, respectively. Overall, our findings indicate the importance of brain miRNAs in the pathology of MDD, and emphasize the involvement of miR-323a-3p and ERBB4 in this phenotype. Future studies further characterizing miR-323a-3p and neuregulin signaling in depression are warranted

MiR-338 is encoded within the AATK gene and is expressed during maturation of hippocampal neurons.

<p>(A) A schematic overview of rat miR-338 encoded within the seventh intron (depicted in blue) of the AATK gene located on chromosome 11, with the exons shown in red. The depicted genes are <i>Rattus norvegicus</i> AATK (rno-AATK) and miR-338 (rno-miR-338). (B) qPCR assay was used to assess levels of pre-miR-338, mature miR-338-3p and miR-338-5p, and AATK mRNA in cultured rat hippocampal neurons (DIV 0–21). The data represents relative fold change in AATK and miR-338 expression levels to DIV 0.</p

MiR-338 targets AATK.

<p>(A) Pre-miR-338, and miR-338-3p levels in B35 cells (transfected with pmiR-338 or pmiR-null plasmids) were quantified following PCR. Pre-miR-338 levels are visualized on 4% agarose gels containing ethidium bromide using UV absorption (254 nm wavelength), and pre-miR-338 band intensities are expressed relative to U6 snRNA. Furthermore qRT-PCR assessment of miR-338-3p levels, expressed relative to U6 snRNA following pmiR-338 overexression versus the null condition. (B) Quantification of AATK mRNA levels in B35 cells transfected with pmiR-338 or pmiR-null vectors, as determined 72 hrs following transfection using qRT-PCR. (C) Relative firefly luciferase activity in B35 cells measured in light units. Cells were co-transfected with luciferase encoding the 3′UTR of rat AATK (indicated as 3′AATK) and either with the pmiR-null control vector, or the pmiR-338 overexpression vector. Luciferase activity was normalized to Renilla luciferase activity. Error bars represent the SEM for n = 3 independent experiments, * is <i>p</i><0.05 with pmiR-null vs. pmiR-338 (Student's t test).</p