Sex Associated Differential Expressions of the Alternatively Spliced Variants mRNA of OPRM1 in Brain Regions of C57BL/6 Mouse

Background/Aims: Opiates are potent analgesics but their clinical use is limited by sex-associated side effects, such as drug tolerance, opioid-induced hyperalgesia and withdrawal reaction. OPRM1, as the main receptor of opioids, plays an important role in the pharmacological process of opioids in rodents and human. We have previously investigated OPRM1, the μ opioid receptor gene, which have dozens of alternatively spliced variants probably correlating with opioid-induced effects in brain regions of four inbred mouse strains and demonstrated the strain-specific expressions of these splice variants. Also, within a strain, the regional expression patterns of some of the variants were similar while others were opposite. Thus, we are aiming to seek out the relationship between sex differences and these alternatively spliced variants. Methods: The present studies follow a SYBR green quantitative PCR (qPCR) which we had used before to examine the expression of OPRM1 splice variant mRNAs in selected brain regions of male and female C57BL/6 mice. Sex-associated differences in baseline latency, opioid-induced tolerance, analgesia and addiction were examined and determined by Tail-flick test, jumps and statistical analysis. Results: The mRNA levels of opioid receptor gene splice variants in male and female mice showed significant differences among the brain regions, implying region-specific alternative splicing of the OPRM1 gene, which was consistent with our previous study. More importantly, the complete mRNA expression profiles of the OPRM1 splice variants was also gender-specific, suggesting a sexual influence on OPRM1 alternative splicing. Conclusion: In brief, we put forward that the distinctions among baseline latency, opioid-induced tolerance, analgesia and physical dependence in male and female mice might correlate with sex associated differential expressions of OPRM1 gene.

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Differential Expressions of the Alternatively Spliced Variant mRNAs of the µ Opioid Receptor Gene, OPRM1, in Brain Regions of Four Inbred Mouse Strains

PLoS ONE ◽

10.1371/journal.pone.0111267 ◽

2014 ◽

Vol 9 (10) ◽

pp. e111267 ◽

Cited By ~ 24

Author(s):

Jin Xu ◽

Zhigang Lu ◽

Mingming Xu ◽

Grace C. Rossi ◽

Benjamin Kest ◽

...

Keyword(s):

Opioid Receptor ◽

Receptor Gene ◽

Inbred Mouse ◽

Brain Regions ◽

Mouse Strains ◽

Inbred Mouse Strains ◽

Alternatively Spliced ◽

Spliced Variant

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Alternative Pre-mRNA Splicing of the Mu Opioid Receptor Gene, OPRM1: Insight into Complex Mu Opioid Actions

Biomolecules ◽

10.3390/biom11101525 ◽

2021 ◽

Vol 11 (10) ◽

pp. 1525

Author(s):

Shan Liu ◽

Wen-Jia Kang ◽

Anna Abrimian ◽

Jin Xu ◽

Luca Cartegni ◽

...

Keyword(s):

Alternative Splicing ◽

Opioid Receptor ◽

Splice Variants ◽

Receptor Gene ◽

Opioid Analgesics ◽

Single Copy ◽

Mu Opioid Receptor ◽

Mu Opioid ◽

Mu Opioids ◽

Functional Relevance

Most opioid analgesics used clinically, including morphine and fentanyl, as well as the recreational drug heroin, act primarily through the mu opioid receptor, a class A Rhodopsin-like G protein-coupled receptor (GPCR). The single-copy mu opioid receptor gene, OPRM1, undergoes extensive alternative splicing, creating multiple splice variants or isoforms via a variety of alternative splicing events. These OPRM1 splice variants can be categorized into three major types based on the receptor structure: (1) full-length 7 transmembrane (TM) C-terminal variants; (2) truncated 6TM; and (3) single TM variants. Increasing evidence suggests that these OPRM1 splice variants are pharmacologically important in mediating the distinct actions of various mu opioids. More importantly, the OPRM1 variants can be targeted for development of novel opioid analgesics that are potent against multiple types of pain, but devoid of many side-effects associated with traditional opiates. In this review, we provide an overview of OPRM1 alternative splicing and its functional relevance in opioid pharmacology.

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Aerobic Exercise Induces Alternative Splicing of Neurexins in Frontal Cortex

Journal of Functional Morphology and Kinesiology ◽

10.3390/jfmk6020048 ◽

2021 ◽

Vol 6 (2) ◽

pp. 48

Author(s):

Elisa Innocenzi ◽

Ida Cariati ◽

Emanuela De Domenico ◽

Erika Tiberi ◽

Giovanna D’Arcangelo ◽

...

Keyword(s):

Alternative Splicing ◽

Aerobic Exercise ◽

Frontal Cortex ◽

Molecular Mechanisms ◽

Splice Variants ◽

Brain Regions ◽

Synaptic Function ◽

Molecular Changes ◽

Beneficial Effects ◽

The Impact

Aerobic exercise (AE) is known to produce beneficial effects on brain health by improving plasticity, connectivity, and cognitive functions, but the underlying molecular mechanisms are still limited. Neurexins (Nrxns) are a family of presynaptic cell adhesion molecules that are important in synapsis formation and maturation. In vertebrates, three-neurexin genes (NRXN1, NRXN2, and NRXN3) have been identified, each encoding for α and β neurexins, from two independent promoters. Moreover, each Nrxns gene (1–3) has several alternative exons and produces many splice variants that bind to a large variety of postsynaptic ligands, playing a role in trans-synaptic specification, strength, and plasticity. In this study, we investigated the impact of a continuous progressive (CP) AE program on alternative splicing (AS) of Nrxns on two brain regions: frontal cortex (FC) and hippocampus. We showed that exercise promoted Nrxns1–3 AS at splice site 4 (SS4) both in α and β isoforms, inducing a switch from exon-excluded isoforms (SS4−) to exon-included isoforms (SS4+) in FC but not in hippocampus. Additionally, we showed that the same AE program enhanced the expression level of other genes correlated with synaptic function and plasticity only in FC. Altogether, our findings demonstrated the positive effect of CP AE on FC in inducing molecular changes underlying synaptic plasticity and suggested that FC is possibly a more sensitive structure than hippocampus to show molecular changes.

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Can quantifying morphology and TMEM119 expression distinguish between microglia and infiltrating macrophages after ischemic stroke and reperfusion in male and female mice?

Journal of Neuroinflammation ◽

10.1186/s12974-021-02105-2 ◽

2021 ◽

Vol 18 (1) ◽

Author(s):

Kimberly F. Young ◽

Rebeca Gardner ◽

Victoria Sariana ◽

Susan A. Whitman ◽

Mitchell J. Bartlett ◽

...

Keyword(s):

Ischemic Stroke ◽

Brain Injury ◽

Western Blot ◽

Calcium Binding ◽

Transmembrane Protein ◽

Brain Regions ◽

Morphological Data ◽

Cell Populations ◽

Male And Female ◽

Female Mice

AbstractBackgroundIschemic stroke is an acquired brain injury with gender-dependent outcomes. A persistent obstacle in understanding the sex-specific neuroinflammatory contributions to ischemic brain injury is distinguishing between resident microglia and infiltrating macrophages—both phagocytes—and determining cell population-specific contributions to injury evolution and recovery processes. Our purpose was to identify microglial and macrophage populations regulated by ischemic stroke using morphology analysis and the presence of microglia transmembrane protein 119 (TMEM119). Second, we examined sex and menopause differences in microglia/macrophage cell populations after an ischemic stroke.MethodsMale and female, premenopausal and postmenopausal, mice underwent either 60 min of middle cerebral artery occlusion and 24 h of reperfusion or sham surgery. The accelerated ovarian failure model was used to model postmenopause. Brain tissue was collected to quantify the infarct area and for immunohistochemistry and western blot methods. Ionized calcium-binding adapter molecule, TMEM119, and confocal microscopy were used to analyze the microglia morphology and TMEM119 area in the ipsilateral brain regions. Western blot was used to quantify protein quantity.ResultsPost-stroke injury is increased in male and postmenopause female mice vs. premenopause female mice (p< 0.05) with differences primarily occurring in the caudal sections. After stroke, the microglia underwent a region, but not sex group, dependent transformation into less ramified cells (p< 0.0001). However, the number of phagocytic microglia was increased in distal ipsilateral regions of postmenopausal mice vs. the other sex groups (p< 0.05). The number of TMEM119-positive cells was decreased in proximity to the infarct (p< 0.0001) but without a sex group effect. Two key findings prevented distinguishing microglia from systemic macrophages. First, morphological data were not congruent with TMEM119 immunofluorescence data. Cells with severely decreased TMEM119 immunofluorescence were ramified, a distinguishing microglia characteristic. Second, whereas the TMEM119 immunofluorescence area decreased in proximity to the infarcted area, the TMEM119 protein quantity was unchanged in the ipsilateral hemisphere regions using western blot methods.ConclusionsOur findings suggest that TMEM119 is not a stable microglia marker in male and female mice in the context of ischemic stroke. Until TMEM119 function in the brain is elucidated, its use to distinguish between cell populations following brain injury with cell infiltration is cautioned.

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The melanocortin-3 receptor is a pharmacological target for the regulation of anorexia

Science Translational Medicine ◽

10.1126/scitranslmed.abd6434 ◽

2021 ◽

Vol 13 (590) ◽

pp. eabd6434

Author(s):

Patrick Sweeney ◽

Michelle N. Bedenbaugh ◽

Jose Maldonado ◽

Pauline Pan ◽

Katelyn Fowler ◽

...

Keyword(s):

Sexual Dimorphism ◽

Feeding Behavior ◽

Critical Role ◽

Brain Regions ◽

Sexually Dimorphic ◽

Male And Female ◽

Female Mice ◽

Bidirectional Regulation ◽

Fear And Anxiety ◽

Agouti Related Protein

Ablation of hypothalamic AgRP (Agouti-related protein) neurons is known to lead to fatal anorexia, whereas their activation stimulates voracious feeding and suppresses other motivational states including fear and anxiety. Despite the critical role of AgRP neurons in bidirectionally controlling feeding, there are currently no therapeutics available specifically targeting this circuitry. The melanocortin-3 receptor (MC3R) is expressed in multiple brain regions and exhibits sexual dimorphism of expression in some of those regions in both mice and humans. MC3R deletion produced multiple forms of sexually dimorphic anorexia that resembled aspects of human anorexia nervosa. However, there was no sexual dimorphism in the expression of MC3R in AgRP neurons, 97% of which expressed MC3R. Chemogenetic manipulation of arcuate MC3R neurons and pharmacologic manipulation of MC3R each exerted potent bidirectional regulation over feeding behavior in male and female mice, whereas global ablation of MC3R-expressing cells produced fatal anorexia. Pharmacological effects of MC3R compounds on feeding were dependent on intact AgRP circuitry in the mice. Thus, the dominant effect of MC3R appears to be the regulation of the AgRP circuitry in both male and female mice, with sexually dimorphic sites playing specialized and subordinate roles in feeding behavior. Therefore, MC3R is a potential therapeutic target for disorders characterized by anorexia, as well as a potential target for weight loss therapeutics.

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