Developmental inhibition of miR-iab8-3p disrupts mushroom body neuron structure and adult learning ability

The Biological Roles of microRNAs in Drosophila Development

Drosophila is a well-established insect model system for studying various physiological phenomena and developmental processes, with a focus on gene regulation. Drosophila development is controlled by programmed regulatory mechanisms specific to individual tissues. When key developmental processes are shared among various insects, the associated regulatory networks are believed to be conserved across insects. Thus, studies of developmental regulation in Drosophila have substantially contributed to our understanding of insect development. Over the past two decades, studies on microRNAs (miRNAs) in Drosophila have revealed their crucial regulatory roles in various developmental processes. This review focuses on the biological roles of miRNAs in specific tissues and processes associated with Drosophila development. Additionally, as a future direction, we discuss sequencing technologies that can analyze the interactions between miRNAs and their target genes, with the aim of enhancing miRNA studies in Drosophila development.

MiR-33-5p Regulates CREB to Induce Morphine State-dependent Memory in Rats: Interaction with the µ Opioid Receptor

The aim of the present study was to examine the hypothesis that miR-33-5p attenuates morphine state-dependent (StD) memory via the µ opioid receptor by regulating cyclic AMP response element-binding protein (CREB). The effects of post-training morphine and morphine StD memory and their interaction with pre-test naloxone were evaluated using a single-trial inhibitory avoidance paradigm. Then, the hippocampal miR-33-5p gene and pCREB/CREB protein expression profiles were evaluated using quantitative real-time PCR and western blotting, respectively. We found that while post-training morphine and morphine StD memory respectively up- and down-regulate the miR-33-5p expression profile in the hippocampus, the reverse results are true for the expression of pCREB/CREB. Pre-test naloxone antagonized the response. Overall, our findings suggest that the expression levels of miR-33-5p in the hippocampus set the basis for morphine StD memory with low miR-33-5p enabling state dependency. The mechanism is mediated via miR33-5p and CREB signaling with the interaction of the µ opioid receptor. This finding may be used as a potential strategy for ameliorating morphine-induced memory-related disorders.

p75NTR enhances cognitive dysfunction in a mouse Alzheimer's disease model by inhibiting microRNA-210-3p-mediated PCYT2 through activation of NF-κB

Alzheimer's disease (AD) is a main cause of dementia and exhibits abnormality in cognitive behaviors. Here, we probed into the role of p75 neurotrophin receptor (p75NTR) in cognitive dysfunction in AD. Primarily, C57BL/6 mouse and neuroblastoma cells were treated by amyloid-beta1-42 (Aβ_1-42), respectively, to establish the in vivo and in vitro models of AD. The downstream genes of p75NTR were predicted by RNA-sequencing and bioinformatics analysis. Then the interaction among p75NTR, nuclear factor kappa B (NF-κB), microRNA-210-3p (miR-210-3p) and phosphoethanolamine cytidylyltransferase 2 (PYCT2) was verified, followed by analysis of their effects on cognitive behaviors and biological characteristics of hippocampal neurons of mouse with AD-like symptoms. p75NTR knockout alleviated cognitive dysfunction in mice with AD-like symptoms and reduced Aβ_1-42-induced hippocampal neuron damage and apoptosis. p75NTR up-regulated miR-210-3p expression by activating NF-κB, thereby limiting PCYT2 expression. PCYT2 silencing in p75NTR^-/- mice promoted neuronal apoptosis and aggravated cognitive dysfunction in AD mouse models. In summary, p75NTR is capable of accelerating cognitive dysfunction in AD by mediating the NF-κB/miR-210-3p/PCYT2 axis.

The making of the Drosophila mushroom body

The mushroom body (MB) is a computational center in the Drosophila brain. The intricate neural circuits of the mushroom body enable it to store associative memories and process sensory and internal state information. The mushroom body is composed of diverse types of neurons that are precisely assembled during development. Tremendous efforts have been made to unravel the molecular and cellular mechanisms that build the mushroom body. However, we are still at the beginning of this challenging quest, with many key aspects of mushroom body assembly remaining unexplored. In this review, I provide an in-depth overview of our current understanding of mushroom body development and pertinent knowledge gaps.

miR-92a Suppresses Mushroom Body-Dependent Memory Consolidation in Drosophila

MicroRNAs (miRNAs) fine tune gene expression to regulate many aspects of nervous system physiology. Here, we show that miR-92a suppresses memory consolidation that occurs in the αβ and γ mushroom body neurons (MBns) of Drosophila, making miR-92a a memory suppressor miRNA. Bioinformatics analyses suggested that mRNAs encoding kinesin heavy chain 73 (KHC73), a protein that belongs to Kinesin-3 family of anterograde motor proteins, may be a functional target of miR-92a. Behavioral studies that employed expression of khc73 with and without its 3' untranslated region (UTR) containing miR-92a target sites, luciferase assays in HEK cells with reporters containing wild-type and mutant target sequences in the khc73 3'UTR, and immunohistochemistry experiments involving KHC73 expression with and without the wild-type khc73 3'UTR, all point to the conclusion that khc73 is a major target of miR-92a in its functional role as a miRNA memory suppressor gene.

Effects of regulating miR-132 mediated GSK-3β on learning and memory function in mice

The aimf of this study was to explore effects of miR-132 and glycogen synthase kinase-3β (GSK-3β) on learning and memory in mice. miR-132 inhibitor GSK-3β overexpression agent (sh-GSK-3β) and normal saline (negative control group) were injected into the hippocampus of adult mice, and healthy adult mice were taken as the unrelated control group. The expression of miR-132 and GSK-3β in the hippocampus of adult and elderly mice was detected using reverse transcription-quantitative PCR (RT-qPCR) and western blot analysis. Morris water maze test was employed to detect learning and memory function in mice. The dual luciferase reporter was adopted to determine the relationship between miR-132 and GSK-3β. Compared with the adult group, the expression of miR-132 was significantly downregulated in the hippocampus in the elderly group, while the expression of GSK-3β was upregulated. Injecting miR-132 inhibitor into the hippocampus of adult mice led to a significant increase in escape latency and a significant decrease in the number of times of crossing platforms. The injection of GSK-3β overexpression agent into the hippocampus of adult mice resulted in a marked increase in escape latency and a significant decrease in the number of times of crossing platforms in the water maze test. It was also found that downregulation of GSK-3β reversed the decline in learning and memory in mice caused by downregulation of miR-132 expression. The dual luciferase report identified a targeted regulatory relationship between miR-132 and GSK-3β. Overexpression of miR-132 can inhibit the expression of GSK-3β in mouse learning and memory ability, which provides some inspiration for understanding the occurrence of learning and memory disorders and future treatment methods.

Circulating MicroRNA-19b Identified From Osteoporotic Vertebral Compression Fracture Patients Increases Bone Formation

Circulating microRNAs (miRNAs) play important roles in regulating gene expression and have been reported to be involved in various metabolic diseases, including osteoporosis. Although the transcriptional regulation of osteoblast differentiation has been well characterized, the role of circulating miRNAs in this process is poorly understood. Here we discovered that the level of circulating miR-19b was significantly lower in osteoporotic patients with vertebral compression fractures than that of healthy controls. The expression level of miR-19b was increased during osteoblastic differentiation of human mesenchymal stem cells (hMSCs) and MC3T3-E1 cells, and transfection with synthetic miR-19b could promote osteoblastic differentiation of hMSCs and MC3T3-E1 cells. PTEN (phosphatase and tensin homolog deleted from chromosome 10) was found to be directly repressed by miR-19b, with a concomitant increase in Runx2 expression and increased phosphorylation of AKT (protein kinase B, PKB). The expression level of circulating miR-19b in aged ovariectomized mice was significantly lower than in young mice. Moreover, the osteoporotic bone phenotype in aged ovariectomized mice was alleviated by the injection of chemically modified miR-19b (agomiR-19b). Taken together, our results show that circulating miR-19b plays an important role in enhancing osteoblastogenesis, possibly through regulation of the PTEN/pAKT/Runx2 pathway, and may be a useful therapeutic target in bone loss disorders, such as osteoporosis. © 2019 American Society for Bone and Mineral Research.

MicroRNA function in Drosophila memory formation

MicroRNAs (miRs) are small non-coding RNAs that regulate protein expression through post-transcriptional mechanisms. They participate in broad aspects of biology from the control of developmental processes to tumorigenesis. Recent studies in Drosophila show that they also regulate activity-dependent and sensory-specific protein expression and support olfactory memory formation. Among the hundreds of miRs described, several have been demonstrated to be required for normal learning, memory, or for the development of neuronal circuits that support memory formation. Fly models of human diseases offer promise of identifying miRs whose expression becomes dysregulated and part of the pathological state, providing models for understanding brain disorders and drug discovery.