Motor Skill Learning Is Associated with Phase-Dependent Modifications in the Striatal cAMP/PKA/DARPP-32 Signaling Pathway in Rodents

Naringin corrects renal failure related to Lesch-Nyhan disease in a rat model via NOS-cAMP-PKA and BDNF/TrkB pathways

This study explored the effect of naringin (NAR) on HGPRT1 deficiency and hyperuricemia through NOS-cAMP-PKA and BDNF/TrkB signaling pathways induced by caffeine (CAF) and KBrO3 in a rat model. Sixty-three adult male albino rats were randomly assigned into nine (n = 7) groups. Group I: control animals, Group II was treated with 100 mg/kg KBrO3 , Group III was treated with 250 mg/kg CAF, Group IV was treated with 100 mg/kg KBrO3  + 250 mg/kg CAF, Group V was administered with 100 mg/kg KBrO3  + 100 mg/kg haloperidol, Group VI was administered with 100 mg/kg KBrO3  + 50 mg/kg NAR, Group VII was administered with 500 mg/kg CAF + 50 mg/kg NAR, and Group VIII was administered with 100 mg/kg KBrO3  + 250 mg/kg CAF + 50 mg/kg NAR. Finally, group IX was treated with 50 mg/kg NAR. The exposure of rats to KBrO3 and CAF for 21 days induced renal dysfunction linked with Lesch-Nyhan disease. NAR obliterated renal dysfunction linked with Lesch-Nyhan disease by decreasing uric acid, renal malondialdehyde level, inhibiting the activities of arginase, and phosphodiesterase-51 (PDE-51) with corresponding upregulation of brain derived-neurotrophic factor and its receptor (BDNF-TrkB), Bcl11b, HGPRT1, and DARPP-32. Additionally, renal failure related to Lesch-Nyhan disease was remarkably corrected by NAR as shown by the reduced activities of AChE and enzymes of ATP hydrolysis (ATPase, AMPase, and ADA) with affiliated increase in the NO level. This study therefore validates NAR as nontoxic and effective chemotherapy against kidney-related Lesch-Nyhan disease by mitigating effects of toxic food additives and enzymes of ATP-hydrolysis via NOS-cAMP-PKA and BDNF/TrkB signaling pathways.

Inflammation, Dopaminergic Brain and Bilirubin

Dopamine is a well-known neurotransmitter due to its involvement in Parkinson's disease (PD). Dopamine is not only involved in PD but also controls multiple mental and physical activities, such as the pleasure of food, friends and loved ones, music, art, mood, cognition, motivation, fear, affective disorders, addiction, attention deficit disorder, depression, and schizophrenia. Dopaminergic neurons (DOPAn) are susceptible to stressors, and inflammation is a recognized risk for neuronal malfunctioning and cell death in major neurodegenerative diseases. Less is known for non-neurodegenerative conditions. Among the endogenous defenses, bilirubin, a heme metabolite, has been shown to possess important anti-inflammatory activity and, most importantly, to prevent DOPAn demise in an ex vivo model of PD by acting on the tumor necrosis factor-alpha (TNFα). This review summarizes the evidence linking DOPAn, inflammation (when possible, specifically TNFα), and bilirubin as an anti-inflammatory in order to understand what is known, the gaps that need filling, and the hypotheses of anti-inflammatory strategies to preserve dopamine homeostasis with bilirubin included.

Adaptive behaviors of Drosophila larvae on slippery surfaces

Friction is ubiquitous but an essential force for insects during locomotion. Insects use dedicated bio-mechanical systems such as adhesive pads to modulate the intensity of friction, providing a stable grip with touching substrates for locomotion. However, how to uncover behavioral adaptation and regulatory neural circuits of friction modification is still largely understood. In this study, we devised a novel behavior paradigm to investigate adaptive behavioral alternation of Drosophila larvae under low-friction surfaces. We found a tail looseness phenotype similar to slipping behavior in humans, as a primary indicator to assess the degree of slipping. We found a gradual reduction on slipping level in wild-type larvae after successive larval crawling, coupled with incremental tail contraction, displacement, and speed acceleration. Meanwhile, we also found a strong correlation between tail looseness index and length of contraction, suggesting that lengthening tail contraction may contribute to enlarging the contact area with the tube. Moreover, we found a delayed adaptation in rut mutant larvae, inferring that neural plasticity may participate in slipping adaptation. In conclusion, our paradigm can be easily and reliably replicated, providing a feasible pathway to uncover the behavioral principle and neural mechanism of acclimation of Drosophila larvae to low-friction conditions.

Disorders of Hippocampus Facilitated by Hypertension in Purine Metabolism Deficiency is Repressed by Naringin, a Bi-flavonoid in a Rat Model via NOS/cAMP/PKA and DARPP-32, BDNF/TrkB Pathways

Individuals who are hypertensive have a higher tendency of predisposition to other genetic diseases including purine metabolism deficiency. Therefore, the search for nontoxic and effective chemo protective agents to abrogate hypertension-mediated genetic disease is vital. This study therefore investigated the repressive effect of naringin (NAR) against disorder of hippocampus facilitated by hypertension in purine metabolism deficiency. Male albino rats randomly assigned into nine groups (n = 7) were treated for 35 days. Group I: control animals, Group II was treated with 100 mg/kg KBrO₃, Group III was treated with 250 mg/kg caffeine, and Group IV was treated with 100 mg/kg KBrO₃ + 250 mg/kg caffeine. Group V was administered with 100 mg/kg KBrO₃ + 100 mg/kg haloperidol. Group VI was administered with 100 mg/kg KBrO₃ + 50 mg/kg NAR. Group VII was administered with 250 mg/kg caffeine + 50 mg/kg NAR, and Group VIII was administered with 100 mg/kg KBrO₃ + 250 mg/kg caffeine + 50 mg/kg NAR. Finally, group IX was treated with 50 mg/kg NAR. The sub-acute exposure to KBrO₃ and CAF induced hypertension and mediated impairment in the hippocampus cells. This was apparent by the increase in PDE-5¹, arginase, and enzymes of ATP hydrolysis (ATPase and AMPase) with a simultaneous increase in cholinergic (AChE and BuChE) and adenosinergic (ADA) enzymes. The hypertensive-mediated hippocampal impairment was associated to alteration of NO and AC signaling coupled with lower expression of brain-derived neurotrophic factor and its receptor (BDNF-TrkB), down regulation of Bcl11b and DARPP-32 which are neurodevelopmental proteins, and hypoxanthine accumulation. However, these features of CAF-mediated hippocampal damage in KBrO₃-induced hypertensive rats were repressed by post-treatment with NAR via production of neuro-inflammatory mediators, attenuation of biochemical alterations, stabilizing neurotransmitter enzymes, regulating NOS/cAMP/PKA and DARPP-32, BDNF/TrkB signaling, and restoring hippocampal tissues.

Ginsenoside Rg1 exerts neuroprotective effects in 3-nitropronpionic acid-induced mouse model of Huntington's disease via suppressing MAPKs and NF-κB pathways in the striatum

Huntington's disease (HD) is one of main neurodegenerative diseases, characterized by striatal atrophy, involuntary movements, and motor incoordination. Ginsenoside Rg1 (Rg1), an active ingredient in ginseng, possesses a variety of neuroprotective effects with low toxicity and side effects. In this study, we investigated the potential therapeutic effects of Rg1 in a mouse model of HD and explored the underlying mechanisms. HD was induced in mice by injection of 3-nitropropionic acid (3-NP, i.p.) for 4 days. From the first day of 3-NP injection, the mice were administered Rg1 (10, 20, 40 mg·kg^-1, p.o.) for 5 days. We showed that oral pretreatment with Rg1 alleviated 3-NP-induced body weight loss and behavioral defects. Furthermore, pretreatment with Rg1 ameliorated 3-NP-induced neuronal loss and ultrastructural morphological damage in the striatum. Moreover, pretreatment with Rg1 reduced 3-NP-induced apoptosis and inhibited the activation of microglia, inflammatory mediators in the striatum. We revealed that Rg1 exerted neuroprotective effects by suppressing 3-NP-induced activation of the MAPKs and NF-κΒ signaling pathways in the striatum. Thus, our results suggest that Rg1 exerts therapeutic effects on 3-NP-induced HD mouse model via suppressing MAPKs and NF-κΒ signaling pathways. Rg1 may be served as a novel therapeutic option for HD.

Gαo is a major determinant of cAMP signaling in the pathophysiology of movement disorders

The G protein alpha subunit o (Gαo) is one of the most abundant proteins in the nervous system, and pathogenic mutations in its gene (GNAO1) cause movement disorder. However, the function of Gαo is ill defined mechanistically. Here, we show that Gαo dictates neuromodulatory responsiveness of striatal neurons and is required for movement control. Using in vivo optical sensors and enzymatic assays, we determine that Gαo provides a separate transduction channel that modulates coupling of both inhibitory and stimulatory dopamine receptors to the cyclic AMP (cAMP)-generating enzyme adenylyl cyclase. Through a combination of cell-based assays and rodent models, we demonstrate that GNAO1-associated mutations alter Gαo function in a neuron-type-specific fashion via a combination of a dominant-negative and loss-of-function mechanisms. Overall, our findings suggest that Gαo and its pathological variants function in specific circuits to regulate neuromodulatory signals essential for executing motor programs.

Muntean et al. describe biochemical, cellular, and physiological mechanisms by which the heterotrimeric G protein subunit Gαo controls neuromodulatory signaling in the striatum and elucidate mechanisms by which Gαo mutations compromise movements in GNAO1 disorder.

The modulatory role of dopamine receptors in brain neuroinflammation

Neuroinflammation is a general pathological feature of central nervous system (CNS) diseases, primarily caused by activation of astrocytes and microglia, as well as the infiltration of peripheral immune cells. Inhibition of neuroinflammation is an important strategy in the treatment of brain disorders. Dopamine (DA) receptor, a significant G protein-coupled receptor (GPCR), is classified into two families: D1-like (D1 and D5) and D2-like (D2, D3 and D4) receptor families, according to their downstream signaling pathways. Traditionally, DA receptor forms a wide variety of psychological activities and motor functions, such as voluntary movement, working memory and learning. Recently, the role of DA receptor in neuroinflammation has been investigated widely, mainly focusing on nucleotide-binding oligomerization domain-like receptor pyrin domain-containing 3 (NLRP3) inflammasome, renin-angiotensin system, αB-crystallin, as well as invading peripheral immune cells, including T cells, dendritic cells, macrophages and monocytes. This review briefly outlined the functions and signaling pathways of DA receptor subtypes as well as its role in inflammation-related glial cells, and subsequently summarized the mechanisms of DA receptors affecting neuroinflammation. Meaningfully, this article provided a theoretical basis for drug development targeting DA receptors in inflammation-related brain diseases.

Can Neonatal Systemic Inflammation and Hypoxia Yield a Cerebral Palsy-Like Phenotype in Periadolescent Mice?

Cerebral palsy (CP) is one of the most common childhood-onset motor disabilities, attributed to injuries of the immature brain in the foetal or early postnatal period. The underlying mechanisms are poorly understood, rendering prevention and treatment strategies challenging. The aim of the present study was to establish a mouse model of CP for preclinical assessment of new interventions. For this purpose, we explored the impact of a double neonatal insult (i.e. systemic inflammation combined with hypoxia) on behavioural and cellular outcomes relevant to CP during the prepubertal to adolescent period of mice. Pups were subjected to intraperitoneal lipopolysaccharide (LPS) injections from postnatal day (P) 3 to P6 followed by hypoxia at P7. Gene expression analysis at P6 revealed a strong inflammatory response in a brain region-dependent manner. A comprehensive battery of behavioural assessments performed between P24 and P47 showed impaired limb placement and coordination when walking on a horizontal ladder in both males and females. Exposed males also displayed impaired performance on a forelimb skilled reaching task, altered gait pattern and increased exploratory activity. Exposed females showed a reduction in grip strength and traits of anxiety-like behaviour. These behavioural alterations were not associated with gross morphological changes, white matter lesions or chronic inflammation in the brain. Our results indicate that the neonatal double-hit with LPS and hypoxia can induce subtle long-lasting deficits in motor learning and fine motor skills, which partly reflect the symptoms of children with CP who have mild gross and fine motor impairments.

Aminoguanidine reverses cognitive deficits and activation of cAMP/CREB/BDNF pathway in mouse hippocampus after traumatic brain injury (TBI)

PRIMARY OBJECTIVE

We aim to study the effects of chronic aminoguanidine (AG) administration on learning and memory impairment after TBI and explore the potential mechanism involved in this process.

RESEARCH DESIGN

Male C57BL/6J mice were divided into 6 groups: Control, TBI + Veh, TBI+ AG (50, 100, 200 and 400 mg/kg, i.p.).

METHODS AND PROCEDURES

Then, we measured cyclicadenosine 3', 5'-monophosphate (cAMP) content, phosphorylated form of cAMP-response element binding protein (p-CREB) level, iNOS, brain-derived neurotrophic factor (BDNF) and postsynaptic density-93/95 (PSD-93/95) expression in hippocampus. The learning and memory abilities were assessed using Morris water maze and step-down test.

MAIN OUTCOMES AND RESULTS

The results demonstrate that TBI induced down-regulation of BDNF, loss of PSD-93/95, learning and memory deficits with down-regulation of cAMP content and p-CREB/CREB ratio. Administration of AG (200 and 400 mg/kg) reversed TBI induced down-regulation of BDNF and PSD-93/95, up-regulated the cAMP content and p-CREB/CREB ratio, which resulted in improvement of learning and memory ability.

CONCLUSIONS

We suspect that AG (200 and 400 mg/kg) might reverse TBI-induced selective loss of postsynaptic proteins and learning and memory deficits with the activation of cAMP/CREB/BDNF signalling pathway.

Sucrose Abstinence and Environmental Enrichment Effects on Mesocorticolimbic DARPP32 in Rats

Dopamine- and cAMP-regulated neuronal phosphoprotein 32 kDa (DARPP32) is a signaling molecule that could serve as a molecular switch, promoting or restraining sucrose seeking. We measured DARPP32 and pThr34 DARPP32 in the brains of male Long-Evans rats with a history of sucrose self-administration followed by 1 or 30 days of abstinence and exposure to either overnight (acute) or one month (chronic) environmental enrichment (EE). Brains were extracted following a 1 h cue reactivity test or no exposure to the test environment. Micropunches (prelimbic, infralimbic, and anterior cingulate areas of the medial prefrontal cortex, orbitofrontal cortex, dorsal striatum, nucleus accumbens, and ventral tegmental area) were then processed using Western blot. Abstinence increased, while EE decreased, sucrose seeking. DARPP32 and pThr34 DARPP32 levels were affected by testing, abstinence, and/or EE in most regions. Especially salient results were observed in the nucleus accumbens core, a region associated with relapse behaviors. Both acute and chronic EE reduced DARPP32 in the nucleus accumbens core and acute EE increased the ratio of phosphorylated to total DARPP32. Degree of DARPP32 phosphorylation negatively correlated with sucrose seeking. These findings demonstrate a potential role for DARPP32 in mediating the “anti-craving” effect of EE.

A rodent brain-machine interface paradigm to study the impact of paraplegia on BMI performance

BACKGROUND

Most brain machine interfaces (BMI) focus on upper body function in non-injured animals, not addressing the lower limb functional needs of those with paraplegia. A need exists for a novel BMI task that engages the lower body and takes advantage of well-established rodent spinal cord injury (SCI) models to study methods to improve BMI performance.

NEW METHOD

A tilt BMI task was designed that randomly applies different types of tilts to a platform, decodes the tilt type applied and rights the platform if the decoder correctly classifies the tilt type. The task was tested on female rats and is relatively natural such that it does not require the animal to learn a new skill. It is self-rewarding such that there is no need for additional rewards, eliminating food or water restriction, which can be especially hard on spinalized rats. Finally, task difficulty can be adjusted by making the tilt parameters.

RESULTS

This novel BMI task bilaterally engages the cortex without visual feedback regarding limb position in space and animals learn to improve their performance both pre and post-SCI.Comparison with Existing Methods: Most BMI tasks primarily engage one hemisphere, are upper-body, rely heavily on visual feedback, do not perform investigations in animal models of SCI, and require nonnaturalistic extrinsic motivation such as water rewarding for performance improvement. Our task addresses these gaps.

CONCLUSIONS

The BMI paradigm presented here will enable researchers to investigate the interaction of plasticity after SCI and plasticity during BMI training on performance.

Toll-like receptor-4 regulates anxiety-like behavior and DARPP-32 phosphorylation

Toll-like receptors (TLRs) play a crucial role in early innate immune responses to inflammatory agents and pathogens. In the brain, some members of the TLR family are expressed in glial cells and neurons. In particular, TLR4 has been involved in learning and memory processes, stress-induced adaptations, and pathogenesis of neurodegenerative disorders. However, the role of TLR4 in emotional behaviors and their underlying mechanisms are poorly understood. In this study, we investigated the role of TLR4 in emotional and social behavior by using different behavioral approaches, and assessed potential molecular alterations in important brain areas involved in emotional responses. TLR4 knockout (KO) mice displayed increased anxiety-like behavior and reduced social interaction compared to wild type control mice. This behavioral phenotype was associated with an altered expression of genes known to be involved in emotional behavior [e.g., brain-derived neurotrophic factor (BDNF) and metabotropic glutamate receptors (mGluRs)]. Interestingly, the mRNA expression of dopamine- and cAMP-regulated phosphoprotein-32 (DARPP-32) was strongly upregulated in emotion-related regions of the brain in TLR4 KO mice. In addition, the phosphorylation levels at Thr75 and Ser97 in DARPP-32 were increased in the frontal cortex of TLR4 KO male mice. These findings indicate that TLR4 signaling is involved in emotional regulation through modulation of DARPP-32, which is a signaling hub that plays a critical role in the integration of numerous neurotransmitter systems, including dopamine and glutamate.

Genetic Variation in the Dopamine System Influences Intervention Outcome in Children with Cerebral Palsy

Background

There is large variation in treatment responses in children with cerebral palsy. Experimental and clinical results suggest that dopamine neurotransmission and brain-derived neurotrophic factor (BDNF) signalling are involved in motor learning and plasticity, which are key factors in modern habilitation success. We examined whether naturally occurring variations in dopamine and BDNF genes influenced the treatment outcomes.

Methods

Thirty-three children (18–60 months of age) with spastic unilateral cerebral palsy were enrolled in the study. Each child had participated in a training programme consisting of active training of the involved hand for 2 h every day during a 2-month training period. The training outcome was measured using Assisting Hand Assessment before and after the training period. Saliva was collected for genotyping of COMT, DAT, DRD1, DRD2, DRD3, and BDNF. Regression analyses were used to examine associations between genetic variation and training outcome.

Findings

There was a statistically significant association between variation in dopamine genes and treatment outcome. Children with a high polygenic dopamine gene score including polymorphisms of five dopamine genes (COMT, DAT, DRD1, DRD2, and DRD3), and reflecting higher endogenous dopaminergic neurotransmission, had the greatest functional outcome gains after intervention.

Interpretation

Naturally occurring genetic variation in the dopamine system can influence treatment outcomes in children with cerebral palsy. A polygenic dopamine score might be valid for treatment outcome prediction and for designing individually tailored interventions for children with cerebral palsy.

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Naturally occurring variation of dopamine genes is associated with treatment outcomes in children with cerebral palsy.

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Children with polymorphisms reflecting higher endogenous dopaminergic neurotransmission had the greatest functional gains.

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A polygenic dopamine score might be valid to predict treatment outcome.

New evidence-based therapies including active motor learning and training for children with cerebral palsy improve motor function at a group level, but there are also large inter-individual variations. Naturally occurring variations in dopamine and BDNF genes affect motor learning and cortical plasticity.

This study showed that naturally occurring genetic variation of five dopamine genes was associated with the outcome of a 2-month long active upper limb motor training intervention in children with unilateral cerebral palsy. The results suggest that a polygenic dopamine gene score can be used to predict the outcome of motor training programmes for children with cerebral palsy.

Dopamine induces soluble α-synuclein oligomers and nigrostriatal degeneration

Parkinson's disease (PD) is defined by the loss of dopaminergic neurons in the substantia nigra and the formation of Lewy body inclusions containing aggregated α-synuclein. Efforts to explain dopamine neuron vulnerability are hindered by the lack of dopaminergic cell death in α-synuclein transgenic mice. To address this, we manipulated both dopamine levels and α-synuclein expression. Nigrally targeted expression of mutant tyrosine hydroxylase with enhanced catalytic activity increased dopamine levels without damaging neurons in non-transgenic mice. In contrast, raising dopamine levels in mice expressing human A53T mutant α-synuclein induced progressive nigrostriatal degeneration and reduced locomotion. Dopamine elevation in A53T mice increased levels of potentially toxic α-synuclein oligomers, resulting in conformationally and functionally modified species. Moreover, in genetically tractable Caenorhabditis elegans models, expression of α-synuclein mutated at the site of interaction with dopamine prevented dopamine-induced toxicity. These data suggest that a unique mechanism links two cardinal features of PD: dopaminergic cell death and α-synuclein aggregation.

The malleable brain: plasticity of neural circuits and behavior - a review from students to students

One of the most intriguing features of the brain is its ability to be malleable, allowing it to adapt continually to changes in the environment. Specific neuronal activity patterns drive long-lasting increases or decreases in the strength of synaptic connections, referred to as long-term potentiation and long-term depression, respectively. Such phenomena have been described in a variety of model organisms, which are used to study molecular, structural, and functional aspects of synaptic plasticity. This review originated from the first International Society for Neurochemistry (ISN) and Journal of Neurochemistry (JNC) Flagship School held in Alpbach, Austria (Sep 2016), and will use its curriculum and discussions as a framework to review some of the current knowledge in the field of synaptic plasticity. First, we describe the role of plasticity during development and the persistent changes of neural circuitry occurring when sensory input is altered during critical developmental stages. We then outline the signaling cascades resulting in the synthesis of new plasticity-related proteins, which ultimately enable sustained changes in synaptic strength. Going beyond the traditional understanding of synaptic plasticity conceptualized by long-term potentiation and long-term depression, we discuss system-wide modifications and recently unveiled homeostatic mechanisms, such as synaptic scaling. Finally, we describe the neural circuits and synaptic plasticity mechanisms driving associative memory and motor learning. Evidence summarized in this review provides a current view of synaptic plasticity in its various forms, offers new insights into the underlying mechanisms and behavioral relevance, and provides directions for future research in the field of synaptic plasticity. Read the Editorial Highlight for this article on page 788. Cover Image for this issue: doi: 10.1111/jnc.13815.

The involvement of DARPP-32 in the pathophysiology of schizophrenia

Schizophrenia is one of the most devastating heterogeneous psychiatric disorders. The dopamine hypothesis is the longest standing pathoetiologic theory of schizophrenia based on neurochemical evidences of elevated brain striatal dopamine synthesis capacity and increased dopamine release in response to stress. Dopamine and cyclic AMP-regulated phosphoprotein of relative molecular mass 32,000 (DARPP-32) is a cytosolic protein highly enriched in the medium spiny neurons of the neostriatum, considered as the most important integrator between the cortical input and the basal ganglia, and associated with motor control. Accumulating evidences has indicated the involvement of DARPP-32 in the development of schizophrenia; i. DARPP-32 phosphorylation is regulated by several neurotransmitters, including dopamine and glutamate, neurotransmitters implicated in schizophrenia pathogenesis; ii. decrease of both total and phosphorylated DARPP-32 in the prefrontal cortex are observed in schizophrenic animal models; iii. postmortem brain studies indicated decreased expression of DARPP-32 protein in the superior temporal gyrus and dorsolateral prefrontal cortex in patients with schizophrenia; iv. DARPP-32 phosphorylation is increased upon therapy with antipsychotic drugs, such as haloperidol and risperidone which improve behavioral performance in experimental animal models and patients; v. Genetic analysis of the gene coding for DARPP-32 propose an association with schizophrenia. Cumulatively, these findings implicate DARPP-32 protein in schizophrenia and propose it as a potential therapeutic target. Here, we summarize the possible roles of DARPP-32 during the development of schizophrenia and make some recommendations for future research. We propose that DARPP-32 and its interacting proteins may serve as potential therapeutic targets in the treatment of schizophrenia.

Skill Learning Modulates RNA Pol II Poising at Immediate Early Genes in the Adult Striatum

A multilayered complexity of epigenetic and transcriptional regulatory mechanisms underlies neuronal activity-dependent gene transcription. The regulation of RNA Pol II progression along the transcription cycle, from promoter-proximal poising (with RNA Pol II paused at promoter-proximal regions, characterized by a Ser5P⁺-rich and Ser2P⁺-poor RPB1 CTD) to active elongation, has emerged as a major step in transcriptional regulation across several organisms, tissues, and developmental stages, including the nervous system. However, it is not known whether this mechanism is modulated by experience. We investigated the impact of learning a motor skill on RNA Pol II phosphorylation dynamics in the adult mouse striatum. We uncovered that learning modulates the in vivo striatal phosphorylation dynamics of the CTD of the RNA Pol II RPB1 subunit, leading to an increased poising index in trained mice. We found that this modulation occurs at immediate early genes (IEGs), with increased poising of RNA Pol II at both Arc and Fos genes but not at constitutively expressed genes. Furthermore, we confirmed that this was learning dependent, and not just regulated by context or motor activity. These experiments demonstrate a novel phenomenon of learning induced transcriptional modulation in adult brain, which may have implications for our understanding of learning, memory allocation, and consolidation.

The bacterial peptidoglycan-sensing molecule Pglyrp2 modulates brain development and behavior

Recent studies have revealed that the gut microbiota modulates brain development and behavior, but the underlying mechanisms are still poorly understood. Here, we show that bacterial peptidoglycan (PGN) derived from the commensal gut microbiota can be translocated into the brain and sensed by specific pattern-recognition receptors (PRRs) of the innate immune system. Using expression-profiling techniques, we demonstrate that two families of PRRs that specifically detect PGN (that is, PGN-recognition proteins and NOD-like receptors), and the PGN transporter PepT1 are highly expressed in the developing brain during specific windows of postnatal development in both males and females. Moreover, we show that the expression of several PGN-sensing molecules and PepT1 in the developing striatum is sensitive to manipulations of the gut microbiota (that is, germ-free conditions and antibiotic treatment). Finally, we used the PGN-recognition protein 2 (Pglyrp2) knockout mice to examine the potential influence of PGN-sensing molecules on brain development and behavior. We demonstrate that the absence of Pglyrp2 leads to alterations in the expression of the autism risk gene c-Met, and sex-dependent changes in social behavior, similar to mice with manipulated microbiota. These findings suggest that the central activation of PRRs by microbial products could be one of the signaling pathways mediating the communication between the gut microbiota and the developing brain.