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Background The brain-derived neurotrophic factor (BDNF) Valine 66 to Methionine human polymorphism results in impaired activity-dependent BDNF release and has been linked to psychiatric disorders including depression and anxiety. We previously showed that male knock-in mice carrying the mouse Methionine homolog (Met68BDNF) exhibit excessive and compulsive alcohol drinking behaviors as compared to the wild-type Val68BDNF mice. Objective Here, we set out to determine the potential mechanism for the heightened and compulsive alcohol drinking phenotypes detected in Met68BDNF mice. Results We found that male, but not female Met68BDNF mice exhibit social anxiety-like behaviors. We further show that male Met68BDNF mice exhibit a preference for alcohol over social interaction. In contrast, alcohol place preference without an alternative social reward, is similar in male Met68BDNF and Val68BDNF mice. Since the Met68BDNF mice show social anxiety phenotypes, we tested whether alcohol reliefs anxiety similarly in Met68BDNF and Val68BDNF mice and found that male, but not female Met68BDNF mice are insensitive to the acute anxiolytic action of alcohol. Finally, we show that this acute tolerance to alcohol-dependent anxiolysis can be restored by overexpressing wild-type Val68BDNF in the ventral hippocampus (vHC) of Met68BDNF mice. Conclusions Together, our results suggest that excessive alcohol drinking in the Met68BDNF may be attributed, in part, to heighted social anxiety and a lack of alcohol-dependent anxiolysis, a phenotype that is associated with malfunction of BDNF signaling in the vHC of male Met68BDNF mice.

International audience; Rett syndrome (RTT) is an X-linked neurogenetic disorder caused by mutations of the MECP2 (methyl-CpG-binding protein 2) gene. Over two decades of work established MeCP2 as a protein with pivotal roles in the regulation of the epigenome, neuronal physiology, synaptic maintenance, and behaviour. Given the genetic aetiology of RTT and the proof of concept of its reversal in a mouse model, considerable efforts have been made to design therapeutic approaches to re-express MeCP2. By being at the forefront of the development of innovative gene therapies, research on RTT is of paramount importance for the treatment of monogenic neurological diseases. Here we discuss the recent advances and challenges of promising genetic strategies for the treatment of RTT including gene replacement therapies, gene/RNA editing strategies, and reactivation of the silenced X chromosome.

The brain-derived neurotrophic factor (BDNF) Valine 66 to Methionine human polymorphism results in impaired activity-dependent BDNF release and has been linked to psychiatric disorders including depression and anxiety. We previously showed that male knock-in mice carrying the mouse Methionine homolog (Met68BDNF) exhibit excessive and compulsive alcohol drinking behaviors as compared to the wild-type Val68BDNF mice.Here, we set out to determine the potential mechanism for the heightened and compulsive alcohol drinking phenotypes detected in Met68BDNF mice.We found that male, but not female Met68BDNF mice exhibit social anxiety-like behaviors. We further show that male Met68BDNF mice exhibit a preference for alcohol over social interaction. In contrast, alcohol place preference without an alternative social reward, is similar in male Met68BDNF and Val68BDNF mice. Since the Met68BDNF mice show social anxiety phenotypes, we tested whether alcohol reliefs anxiety similarly in Met68BDNF and Val68BDNF mice and found that male, but not female Met68BDNF mice are insensitive to the acute anxiolytic action of alcohol. Finally, we show that this acute tolerance to alcohol-dependent anxiolysis can be restored by overexpressing wild-type Val68BDNF in the ventral hippocampus (vHC) of Met68BDNF mice.Together, our results suggest that excessive alcohol drinking in the Met68BDNF may be attributed, in part, to heighted social anxiety and a lack of alcohol-dependent anxiolysis, a phenotype that is associated with malfunction of BDNF signaling in the vHC of male Met68BDNF mice.

Alcohol Use Disorder (AUD) affects a large portion of the population. Unfortunately, efficacious medications to treat the disease are limited. Studies in rodents suggest that mTORC1 plays a crucial role in mechanisms underlying phenotypes such as heavy alcohol intake, habit, and relapse. Thus, mTORC1 inhibitors, which are used in the clinic, are promising therapeutic agents to treat AUD. However, chronic inhibition of mTORC1 in the periphery produces undesirable side effects, which limit their potential use for the treatment of AUD. To overcome these limitations, we designed a binary drug strategy in which male mice were treated with the mTORC1 inhibitor RapaLink-1 together with a small molecule (RapaBlock) to protect mTORC1 activity in the periphery. We show that whereas RapaLink-1 administration blocked mTORC1 activation in the liver, RapaBlock abolished the inhibitory action of Rapalink-1. RapaBlock also prevented the adverse side effects produced by chronic inhibition of mTORC1. Importantly, co-administration of RapaLink-1 and RapaBlock inhibited alcohol-dependent mTORC1 activation in the nucleus accumbens and attenuated alcohol seeking and drinking., Chronic use of mTORC1 inhibitors produces undesirable side effects in humans which limit their value for CNS disorders treatment. The authors present a binary drug strategy to protects mTORC1 activity in the periphery and show its potential utility in preclinical models of alcohol use disorder.

Brain-derived neurotrophic factor (BDNF) signaling in the dorsolateral striatum (DLS) gates alcohol self-administration in rodents. The major source of BDNF in the striatum is the cortex, and we recently found that BDNF-expressing neurons in the ventrolateral orbitofrontal cortex (vlOFC) extend axonal projections to the DLS. We therefore hypothesized that BDNF in the vlOFC to DLS circuit moderates alcohol intake. We show that overexpression of BDNF in the vlOFC, which activates BDNF signaling in the DLS, is sufficient to attenuate voluntary consumption and seeking of 20% alcohol in the home cage using a two-bottle choice paradigm. Overexpressing BDNF in the vlOFC had no effect on the consumption of a sweetened saccharin solution. In addition, BDNF overexpression in the neighboring motor cortex did not alter alcohol intake. Finally, pathway-specific overexpression of BDNF in DLS-projecting vlOFC neurons significantly reduced alcohol intake and preference. Overall, BDNF in the vlOFC, and specifically in a vlOFC-DLS pathway, keeps alcohol drinking in moderation.

BDNF is released from axon terminals originating in the cerebral cortex onto striatal neurons. Here, we characterized BDNF in the corticostriatal circuitry. First, we utilized Bdnf-Cre and Ribotag transgenic mouse lines to label BDNF-positive cells in the cortex, and detected BDNF expression in the motor cortex, medial prefrontal cortex (mPFC) and the orbitofrontal cortex (OFC). Next, we used a retrograde viral tracing strategy, in combination with Bdnf-Cre knockin mice, to map the cortical outputs of BDNF neurons in the dorsal striatum. We found that the BDNF-positive prefrontal regions differentially project to the dorsal striatum. Specifically, BDNF-expressing neurons located in the mPFC project to both dorsolateral striatum (DLS) and dorsomedial striatum (DMS), and those located in the motor cortex project to the DLS. Surprisingly however, the BDNF-expressing OFC neurons differentially target the dorsal striatum depending on their mediolateral location. Specifically, the DMS is mainly innervated by the medial part of the OFC (mOFC) whereas, the DLS receives projections specifically from the ventrolateral region of the OFC (vlOFC). Next, using an anterograde viral tracing strategy, we confirmed the presence of a BDNF-specific vlOFC-DLS circuit. Finally, we show that overexpression of BDNF in the vlOFC activates TrkB signaling specifically in the DLS but not in the DMS demonstrating the functionality of this circuit. Our study uncovers a previously unknown neural circuit composed of BDNF-positive vlOFC neurons projecting to the DLS. These findings could have important implications for the role of BDNF signaling in the OFC as well as in other corticostriatal circuitries. Significance Statement BDNF is released in axons upon neuronal depolarization. Surprisingly, careful mapping of BDNF projecting neurons in CNS has not been conducted. Using anterograde and retrograde viral strategies in combination with transgenic reporter mice, we mapped out corticostriatal BDNF circuits. We found that mPFC BDNF neurons project to both the DMS and DLS, and the motor cortex to the DLS only. In contrast, BDNF neurons in the OFC are anatomically segregated. Whereas BDNF in mOFC neurons project to the DMS, BDNF in vlOFC project specifically to the DLS. Our findings could be important to the study of BDNF in corticostriatal circuitries.

Mutations in the X-linked MECP2 gene are responsible for Rett syndrome (RTT), a severe neurological disorder. MECP2 is a transcriptional modulator that finely regulates the expression of many genes, specifically in the central nervous system. Several studies have functionally linked the loss of MECP2 in astrocytes to the appearance and progression of the RTT phenotype in a non-cell autonomous manner and mechanisms are still unknown. Here, we used primary astroglial cells from Mecp2-deficient (KO) pups to identify deregulated secreted proteins. Using a differential quantitative proteomic analysis, twenty-nine proteins have been identified and four were confirmed by Western blotting with new samples as significantly deregulated. To further verify the functional relevance of these proteins in RTT, we tested their effects on the dendritic morphology of primary cortical neurons from Mecp2 KO mice that are known to display shorter dendritic processes. Using Sholl analysis, we found that incubation with Lcn2 or Lgals3 for 48 h was able to significantly increase the dendritic arborization of Mecp2 KO neurons. To our knowledge, this study, through secretomic analysis, is the first to identify astroglial secreted proteins involved in the neuronal RTT phenotype in vitro, which could open new therapeutic avenues for the treatment of Rett syndrome.

The psychedelic alkaloid ibogaine has anti-addictive properties in both humans and animals1. Unlike most medications for the treatment of substance use disorders, anecdotal reports suggest that ibogaine has the potential to treat addiction to various substances, including opiates, alcohol and psychostimulants. The effects of ibogaine-like those of other psychedelic compounds-are long-lasting2, which has been attributed to its ability to modify addiction-related neural circuitry through the activation of neurotrophic factor signalling3,4. However, several safety concerns have hindered the clinical development of ibogaine, including its toxicity, hallucinogenic potential and tendency to induce cardiac arrhythmias. Here we apply the principles of function-oriented synthesis to identify the key structural elements of the potential therapeutic pharmacophore of ibogaine, and we use this information to engineer tabernanthalog-a water-soluble, non-hallucinogenic, non-toxic analogue of ibogaine that can be prepared in a single step. In rodents, tabernanthalog was found to promote structural neural plasticity, reduce alcohol- and heroin-seeking behaviour, and produce antidepressant-like effects. This work demonstrates that, through careful chemical design, it is possible to modify a psychedelic compound to produce a safer, non-hallucinogenic variant that has therapeutic potential.

Fyn kinase in the dorsomedial striatum (DMS) of rodents plays a central role in mechanisms underlying excessive alcohol intake. The DMS is comprised of medium spiny neurons (MSNs) that project directly (dMSNs) or indirectly (iMSNs) to the substantia nigra. Here, we examined the cell-type specificity of Fyn’s actions in alcohol use. First, we knocked down Fyn selectively in DMS dMSNs or iMSNs of mice and measured the level of alcohol consumption. We found that downregulation of Fyn in dMSNs, but not in iMSNs, reduces excessive alcohol but not saccharin intake. D1Rs are coupled to Gαs/olf, which activate cAMP signaling. To examine whether Fyn’s actions are mediated through cAMP signaling, DMS dMSNs were infected with GαsDREADD, and the activation of Fyn signaling was measured following CNO treatment. We found that remote stimulation of cAMP signaling in DMS dMSNs activates Fyn and promotes the phosphorylation of the Fyn substrate, GluN2B. In contract, remote activation of GαsDREADD in DLS dMSNs did not alter Fyn signaling. We then tested whether activation of GαsDREADD in DMS dMSNs or iMSNs alters alcohol intake and observed that CNO-dependent activation of GαsDREADD in DMS dMSNs but not iMSNs increases alcohol but not saccharin intake. Finally, we examined the contribution of Fyn to GαsDREADD-dependent increase in alcohol intake, and found that systemic administration of the Fyn inhibitor, AZD0503 blocks GαsDREADD-dependent increase in alcohol consumption. Our results suggest that the cAMP-Fyn axis in the DMS dMSNs is a molecular transducer of mechanisms underlying the development of excessive alcohol consumption. Fil: Ehinger, Yann. University of California San Francisco; Estados Unidos Fil: Morisot, Nadege. Nkarta Therapeutics; Estados Unidos. University of California San Francisco; Estados Unidos Fil: Phamluong, Khanhky. University of California San Francisco; Estados Unidos Fil: Sakhai, Samuel A.. Sage Therapeutics; Estados Unidos. University of California San Francisco; Estados Unidos Fil: Soneja, Drishti. University of California San Francisco; Estados Unidos Fil: Adrover, Martín Federico. National Institutes of Health; Estados Unidos. University Of California San Francisco (ucsf); Estados Unidos. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Investigaciones en Ingeniería Genética y Biología Molecular "Dr. Héctor N. Torres"; Argentina Fil: Alvarez, Veronica A.. National Institutes of Health; Estados Unidos Fil: Ron, Dorit. University of California San Francisco; Estados Unidos

Heavy alcohol use reduces the levels of the brain-derived neurotrophic factor (BDNF) in the prefrontal cortex of rodents through the upregulation of microRNAs (miRs) targeting BDNF mRNA. In humans, an inverse correlation exists between circulating blood levels of BDNF and the severity of psychiatric disorders including alcohol abuse. Here, we set out to determine whether a history of heavy alcohol use produces comparable alterations in the blood of rats. We used an intermittent access to 20% alcohol using the two-bottle choice paradigm (IA20%2BC) and measured circulating levels of BDNF protein and miRs targeting BDNF in the serum of Long-Evans rats before and after 8 weeks of excessive alcohol intake. We observed that the drinking profile of heavy alcohol users is not unified, whereas 70% of the rats gradually escalate their alcohol intake (late onset), and 30% of alcohol users exhibit a very rapid onset of drinking (rapid onset). We found that serum BDNF levels are negatively correlated with alcohol intake in both rapid onset and late onset rats. In contrast, increased expression of the miRs targeting BDNF, miR30a-5p, miR-195-5p, miR191-5p and miR206-3p, was detected only in the rapid onset rats. Finally, we report that the alcohol-dependent molecular changes are not due to alterations in platelet number. Together, these data suggest that rats exhibit both late and rapid onset of alcohol intake. We further show that heavy alcohol use produces comparable changes in BDNF protein levels in both groups. However, circulating microRNAs are responsive to alcohol only in the rapid onset rats.

Mutations in the X‐linked MECP2 gene are responsible for Rett syndrome (RTT), a severe neurological disorder for which there is no treatment. Several studies have linked the loss of MeCP2 function to alterations of brain‐derived neurotrophic factor (BDNF) levels, but non‐specific overexpression of BDNF only partially improves the phenotype of Mecp2‐deficient mice. We and others have previously shown that huntingtin (HTT) scaffolds molecular motor complexes, transports BDNF‐containing vesicles, and is under‐expressed in Mecp2 knockout brains. Here, we demonstrate that promoting HTT phosphorylation at Ser421, either by a phospho‐mimetic mutation or inhibition of the phosphatase calcineurin, restores endogenous BDNF axonal transport in vitro in the corticostriatal pathway, increases striatal BDNF availability and synaptic connectivity in vivo, and improves the phenotype and the survival of Mecp2 knockout mice—even though treatments were initiated only after the mice had already developed symptoms. Stimulation of endogenous cellular pathways may thus be a promising approach for the treatment of RTT patients., BDNF is one of the most prominent deregulated factors in Rett syndrome, a severe neurodevelopmental disorder. This study reveals that huntingtin phosphorylation stimulates BDNF axonal transport and improves many features in a Rett mouse model, suggesting a possible therapeutic approach.

Heavy alcohol use reduces the levels of the brain-derived neurotrophic factor (BDNF) in the prefrontal cortex of rodents through the upregulation of microRNAs targetingBDNFmRNA. In humans, an inverse correlation exists between circulating blood levels of BDNF and the severity of psychiatric disorders including alcohol abuse. Here, we set out to determine whether a history of heavy alcohol use produces comparable alterations in the blood of rats. We used an intermittent access to 20% alcohol using the 2-bottle choice paradigm (IA20%2BC), and measured circulating levels of BDNF protein and microRNAs in the serum of Long-Evans rats before and after 8-weeks of excessive alcohol intake. We observed that the drinking profile of heavy alcohol users is not unified; Whereas 70% of the rats gradually escalate their alcohol intake (Late Onset), 30% of alcohol users exhibit a very Rapid Onset of drinking (Rapid Onset). We found that serum BDNF levels are negatively correlated with alcohol intake in both Rapid Onset and Late Onset rats. In contrast, increased expression of the microRNAs (miRs) targeting BDNF, miR30a-5p, miR-195-5p, miR191-5p and miR206-3p, was detected only in the Rapid Onset rats. Finally, we report that the alcohol-dependent molecular changes are not due to alterations in platelet number. Our data suggest that rats exhibit both Late and Rapid Onset of alcohol intake. We further show that heavy alcohol use produces comparable changes in BDNF protein levels in both groups. However, circulating microRNAs are responsive to alcohol only in the Rapid Onset rats.

The mammalian target of rapamycin complex 1 (mTORCl) plays an important role in dendritic translation, synaptic plasticity, and learning and memory. We previously showed that heavy alcohol use activates mTORC1 in the orbitofrontal cortex (OFC) of rodents. Here, we set out to determine the consequences of alcohol-dependent mTORC1 activation in the OFC. We found that although inhibition of mTORC1 in the OFC does not alter rat alcohol intake per se, it attenuates alcohol seeking. We then tested whether mTORC1 in the OFC is required for goal-directed or habitual alcohol seeking. To do so, rats were trained self-administer alcohol under a random ratio (RR) or a random interval (RI) schedule of reinforcement, which biases toward goal-directed or habitual responding, respectively, and tested whether mTORC1 inhibition alters lever presses following alcohol devaluation. We found that pharmacological inhibition of mTORC1 or knockdown of the adaptor protein, Raptor, did not affect goal-directed alcohol responding but restored sensitivity to devaluation in RI-trained rats. In contrast, habitual responding for sucrose was unaltered by mTORC1 inhibition. These data suggest that mTORC1 in the OFC drives alcohol habit. We then elucidate the mechanism by which mTORC1 is activated by alcohol, and found that the recruitment of GluN2B during alcohol withdrawal stimulates mTORC1 in OFC cFos-positive neurons. Finally, we show that inhibition of GluN2B in the OFC attenuates both alcohol seeking and habitual responding for alcohol. Together, our data suggest that alcohol withdrawal promotes an NMDAR-dependent activation of mTORC1 which in turn drives habitual alcohol seeking.