The activity of the serotonin receptor 2C is regulated by alternative splicing

Oral Administration of Efavirenz Dysregulates the Tph2 Gene in Brain Serotonergic Areas and Alters Weight and Mood in Mice

Most HIV-antiretroviral drugs have adverse effects. Efavirenz (EFV) is an example of a drug with neuropsychiatric effects, such as anxiety, depression, and suicidal thoughts, in people living with HIV (PLWH). The mechanisms by which EFV causes neuropsychiatric alterations in PLWH are complex, multifactorial, and not fully understood, although several studies in animals have reported changes in brain energy metabolism, alterations in monoamine turnover, GABA, and glutamate levels, and changes in 5-HT receptors. In this report, we studied the effects of EFV on the serotonergic system in healthy mice, specifically, whether EFV results in alterations in the levels of the tryptophan hydroxylase 2 (Tph2) gene in the brain. EFV (10 mg/kg) and distilled water (1.5 µL/kg) (control group) were orally administered to the mice for 36 days. At the end of the treatment, Tph2 expression levels in mouse brains were measured, and mood was evaluated by three trials: the forced swim test, elevated plus maze, and open field test. Our results revealed dysregulation of Tph2 expression in the brainstem, amygdala, and hypothalamus in the EFV group, and 5-HT levels increased in the amygdala in the EFV group. In the behavioral tests, mice given EFV exhibited a passive avoidance response in the forced swim test and anxiety-like behavior in the elevated plus maze, and they lost weight. Herein, for the first time, we showed that EFV triggered dysregulation of the Tph2 gene in the three serotonergic areas studied; and 5-HT levels increased in the amygdala using the ELISA method. However, further studies will be necessary to clarify the increase of 5-HT in the amygdala as well as understand the paradoxical decrease in body weight with the simultaneous increase in food consumption. It will also be necessary to measure 5-HT by other techniques different from ELISA, such as HPLC.

The role of brain serotonin signaling in excessive alcohol consumption and withdrawal: A call for more research in females

Alcohol Use Disorder (AUD) is a leading cause of death and disability worldwide, but current treatments are insufficient in fully addressing the symptoms that often lead to relapses in alcohol consumption. The brain's serotonin system has been implicated in AUD for decades and is a major regulator of stress-related behaviors associated with increased alcohol consumption. This review will discuss the current literature on the association between neurobiological adaptations in serotonin systems and AUD in humans as well as the effectiveness of serotonin receptor manipulations on alcohol-related behaviors like consumption and withdrawal. We will further discuss how these findings in humans relate to findings in animal models, including a comparison of systemic pharmacological manipulations modulating alcohol consumption. We next provide a detailed overview of brain region-specific roles for serotonin and serotonin receptor signaling in alcohol-related behaviors in preclinical animal models, highlighting the complexity of forming a cohesive model of serotonin function in AUD and providing possible avenues for more effective therapeutic intervention. Throughout the review, we discuss what is known about sex differences in the sequelae of AUD and the role of serotonin in these sequelae. We stress a critical need for additional studies in women and female animals so that we may build a clearer path to elucidating sex-specific serotonergic mechanisms and develop better treatments.

Latest updates on the serotonergic system in depression and anxiety

Psychiatric disorders are among the leading causes of global health burden, with depression and anxiety being the most disabling subtypes. The two common disorders, depression and anxiety, usually coexist and are pathologically polygenic with complicated etiologies. Current drug-based therapies include selective serotonin reuptake inhibitors, serotonin and norepinephrine reuptake inhibitors, and 5-hydroxytryptamine partial agonists. However, these modalities share common limitations, such as slow onset and low efficacy, which is why potential mechanistic insights for new drug targets are needed. In this review, we summarize recent advances in brain localization, pathology, and therapeutic mechanisms of the serotonergic system in depression and anxiety.

Ligand-independent receptor clustering modulates transmembrane signaling: a new paradigm

Cell-surface receptors mediate communication between cells and their environment. Lateral membrane organization and dynamic receptor cluster formation are fundamental in signal transduction and cell signaling. However, it is not yet fully understood how receptor clustering modulates a wide variety of physiologically relevant processes. Recent growing evidence indicates that biological responses triggered by membrane receptors can be modulated even in the absence of the natural receptor ligand. We review the most recent findings on how ligand-independent receptor clustering can regulate transmembrane signaling. We discuss the latest technologies to control receptor assembly, such as DNA nanotechnology, optogenetics, and optochemistry, focusing on the biological relevance and unraveling of ligand-independent signaling.

Deleting Snord115 genes in mice remodels monoaminergic systems activity in the brain toward cortico-subcortical imbalances

The neuronal-specific SNORD115 has gathered interest because its deficiency may contribute to the pathophysiology of Prader-Willi syndrome (PWS), possibly by altering post-transcriptional regulation of the gene encoding the serotonin (HTR2C) receptor. Yet, Snord115-KO mice do not resume the main symptoms of PWS, and only subtle-altered A-to-I RNA editing of Htr2c mRNAs was uncovered. Because HTR2C signaling fine-tunes the activity of monoaminergic neurons, we addressed the hypothesis that lack of Snord115 alters monoaminergic systems. We first showed that Snord115 was expressed in both monoaminergic and non-monoaminergic cells of the ventral tegmental area (VTA) and the dorsal raphe nucleus (DRN) harboring cell bodies of dopaminergic and serotonergic neurons, respectively. Measuring the tissue level of monoamines and metabolites, we found very few differences except that the content of homovanillic acid-a metabolite of dopamine-was decreased in the orbitofrontal and prefrontal cortex of Snord115-KO mice. The latter effects were, however, associated with a few changes in monoamine tissue content connectivity across the 12 sampled brain regions. Using in vivo single-cell extracellular recordings, we reported that the firing rate of VTA dopaminergic neurons and DRN serotonergic neurons was significantly increased in Snord115-KO mice. These neural circuit dysfunctions were not, however, associated with apparent defects in binge eating, conditioned place preference to cocaine, cocaine-induced hyperlocomotion or compulsive behavior. Altogether, our multiscale study shows that the absence of Snord115 impacts central monoaminergic circuits to an extent that does not elicit gross behavioral abnormalities.

Aβ peptides stabilize GPCRs in inactive form and trigger inverse agonism in Alzheimer's disease

Several G-protein coupled receptors (GPCR) are upregulated in Alzheimer's Disease (AD), which ought to facilitate neurotransmission, and improve cognition. Yet, despite this upregulation, associated physiological effects are not observed in AD patients. This paradox solicits urgent attention to find a suitable justification for disturbed neurotransmission in AD. This article focuses on the role of Aβ granules and their possible interaction with GPCRs that modulate neurotransmission and AD progression.

Association of the 5HTR2C gene Ser23 variation with childhood allergic asthma

Objective: Allergic asthma is the most frequently observed subtype of individuals with asthma. The effects of serotonin plays in the pathophysiology of asthma has not been clearly determined. Thus, this study aimed to investigate the association between the 5HTR2C gene rs 6318 G>C polymorphism and allergic asthma in pediatric patients in Cyprus.

Methods: This study included total number of 177 individuals with 118 control and 59 pediatric patients (43 atopic and 16 non-atopic asthma patient). A skin prick test was performed for each patient to confirm asthma diagnosis and to evaluate atopic status. Genotyping for the 5HTR2C was completed by Real Time-PCR analysis.

Results: The genotype distribution frequencies were not in agreement with the Hardy-Weinberg Equilibrium in the patients’ group (p<0.00001). The frequency of the risk allele (allele C) was not significantly different between the patient and control groups (p=0.255). The genotypic distribution between atopic asthma and non-atopic asthma within the patientsts groups was not in agreement with the Hardy-Weinberg Equilibrium (p=0.006). However, risk allele presence showed a statistically significant association with atopy-related asthma (p=0.037).

Discussion & Conclusion: Overall, despite the finding of no association between the 5HTR2C rs6318 C allele and childhood asthma, the current results indicated that there is a strong association between the 5HTR2C rs6318 C variant and childhood atopic asthma.

Natural copy number variation of tandemly repeated regulatory SNORD RNAs leads to individual phenotypic differences in mice

Genic copy number differences can have phenotypic consequences, but so far this has not been studied in detail in natural populations. Here, we analysed the natural variation of two families of tandemly repeated regulatory small nucleolar RNAs (SNORD115 and SNORD116) in the house mouse (Mus musculus). They are encoded within the Prader-Willi Syndrome gene region, known to be involved in behavioural, metabolic, and osteogenic functions in mammals. We determined that the copy numbers of these SNORD RNAs show substantial natural variation, both in wild-derived mice as well as in an inbred mouse strain (C57BL/6J). We show that copy number differences are subject to change across generations, making them highly variable and resulting in individual differences. In transcriptome data from brain samples, we found SNORD copy-number correlated regulation of possible target genes, including Htr2c, a predicted target gene of SNORD115, as well as Ankrd11, a predicted target gene of SNORD116. Ankrd11 is a chromatin regulator, which has previously been implicated in regulating the development of the skull. Based on morphometric shape analysis of the skulls of individual mice of the inbred strain, we show that shape measures correlate with SNORD116 copy numbers in the respective individuals. Our results suggest that the variable dosage of regulatory RNAs can lead to phenotypic variation between individuals that would typically have been ascribed to environmentally induced variation, while it is actually encoded in individual differences of copy numbers of regulatory molecules.

Region- and receptor-specific effects of chronic social stress on the central serotonergic system in mice

Serotonin (5-HT), via its receptors expressed in discrete brain regions, modulates aversion and reward processing and is implicated in various psychiatric disorders including depression. Stressful experiences affect central serotonergic activity and act as a risk factor for depression; this can be modelled preclinically. In adult male C57BL/6J mice, 15-day chronic social stress (CSS) leads to depression-relevant behavioural states, including increased aversion and reduced reward sensitivity. Based on this evidence, here we investigated CSS effects on 5-HT1A, 5-HT2A, and 5-HT2C receptor binding in discrete brain regions using in vitro quantitative autoradiography with selective radioligands. In addition, mRNA expression of Htr1a, 2a, 2c and Slc6a4 (5-HT transporter) was measured by quantitative PCR. Relative to controls, the following effects were observed in CSS mice: 5-HT1A receptor binding was markedly increased in the dorsal raphe nucleus (136%); Htr1a mRNA expression was increased in raphe nuclei (19%), medial prefrontal cortex (35%), and hypothalamic para- and periventricular nuclei (21%) and ventral medial nucleus (38%). 5-HT2A receptor binding was decreased in the amygdala (48%) and ventral tegmental area (60%); Htr2a mRNA expression was increased in the baso-lateral amygdala (116%). 5-HT2C receptor binding was decreased in the dorsal raphe nucleus (42%). Slc6a4 mRNA expression was increased in the raphe (59%). The present findings add to the translational evidence that chronic social stress impacts on the central serotonergic system in a region- and receptor-specific manner, and that this altered state of the serotonergic system contributes to stress-induced dysfunctions in emotional processing.

Central 5-HTR2C in the Control of Metabolic Homeostasis

The 5-hydroxytryptamine 2C receptor (5-HTR2C) is a class G protein-coupled receptor (GPCR) enriched in the hypothalamus and the brain stem, where it has been shown to regulate energy homeostasis, including feeding and glucose metabolism. Accordingly, 5-HTR2C has been the target of several anti-obesity drugs, though the associated side effects greatly curbed their clinical applications. Dissecting the specific neural circuits of 5-HTR2C-expressing neurons and the detailed molecular pathways of 5-HTR2C signaling in metabolic regulation will help to develop better therapeutic strategies towards metabolic disorders. In this review, we introduced the regulatory role of 5-HTR2C in feeding behavior and glucose metabolism, with particular focus on the molecular pathways, neural network, and its interaction with other metabolic hormones, such as leptin, ghrelin, insulin, and estrogens. Moreover, the latest progress in the clinical research on 5-HTR2C agonists was also discussed.

Reassessment of the involvement of Snord115 in the serotonin 2c receptor pathway in a genetically relevant mouse model

SNORD115 has been proposed to promote the activity of serotonin (HTR2C) receptor via its ability to base pair with its pre-mRNA and regulate alternative RNA splicing and/or A-to-I RNA editing. Because SNORD115 genes are deleted in most patients with the Prader-Willi syndrome (PWS), diminished HTR2C receptor activity could contribute to the impaired emotional response and/or compulsive overeating characteristic of this disease. In order to test this appealing but never demonstrated hypothesis in vivo, we created a CRISPR/Cas9-mediated Snord115 knockout mouse. Surprisingly, we uncovered only modest region-specific alterations in Htr2c RNA editing profiles, while Htr2c alternative RNA splicing was unchanged. These subtle changes, whose functional relevance remains uncertain, were not accompanied by any discernible defects in anxio-depressive-like phenotypes. Energy balance and eating behavior were also normal, even after exposure to high-fat diet. Our study raises questions concerning the physiological role of SNORD115, notably its involvement in behavioural disturbance associated with PWS.

Effects of 5-HT2C receptor modulation and the NA reuptake inhibitor atomoxetine in tests of compulsive and impulsive behaviour

Drug repositioning has gained strategic value as a reaction to high attrition rates of new drugs as they pass through the clinical development process. The 5-HT2C receptor agonist lorcaserin (Belviq®), and the selective NA reuptake inhibitor atomoxetine (Strattera®) represent two drugs FDA approved for obesity and ADHD respectively. Although both drugs are of differing pharmacological class, each share a property of regulating impulsive behaviours in preclinical studies, and thus represent candidates for consideration in clinical conditions labelled as 'impulsive-compulsive disorders'. The present studies investigated both drugs, as well as the highly selective 5-HT2C agonist CP-809101 in two tests of compulsive action: schedule-induced polydipsia (SIP) and increased perseverative [PSV] (and premature [PREM]) responses emitted during an extended ITI 5-choice task. While lorcaserin (0.06-0.6 mg/kg), CP-809101 (0.1-1 mg/kg) and atomoxetine (0.1-1 mg/kg) each reduced both PREM and PSV measures in the 5-choice task, at equivalent doses only lorcaserin and CP-809101 affected excessive water intake in the SIP task, atomoxetine (0.1-2 mg/kg) was essentially ineffective. Further evidence supporting a role of the 5-HT2C receptor as an important regulator of impulsive-compulsive behaviours, the selective antagonist SB-242084 produced the opposing effects to lorcaserin, i.e promoting both impulsive and compulsive behaviours. The profile of atomoxetine may suggest differences in the nature of compulsive action measured either as non-regulatory drinking in the SIP task, and PSV responses made in a 5-choice task. These studies support the consideration of 5-HT2C receptor agonists, typified by lorcaserin, and atomoxetine as potential treatments for clinical conditions categorised as 'impulsive-compulsive disorders'. This article is part of the special issue entitled 'Serotonin Research: Crossing Scales and Boundaries'.

RNA Editing of Serotonin 2C Receptor and Alcohol Intake

Serotonin 2C receptor (5-HT_{2 C}R) belongs to the superfamily of seven transmembrane domain receptors coupled to G proteins (GPCR). It is broadly distributed in the CNS and its expression is relatively high in the limbic system including the amygdala, nucleus accumbens (NAc), hippocampus, and hypothalamus. Based on its expression patterns and numerous pharmacological studies, 5-HT_{2 C}R is thought to be involved in various brain functions including emotion, appetite, and motor behavior. Here, we review 5-HT_{2 C}R and its relationship with alcohol intake with a particular focus on the involvement of 5-HT_{2 C}R mRNA editing and its association with alcohol preference in mice. RNA editing is a post-transcriptional modification mechanism. In mammals, adenosine is converted to inosine by the deamination enzymes ADAR1 and ADAR2. 5-HT_{2 C}R is the only GPCR subjected to RNA editing within the coding region. It has five editing sites in exon 5 that encode the second intracellular loop. Consequently, three amino acids residues (I156, N158, and I160) of the unedited receptor (INI) may be altered to differently edited isoforms, resulting in a change of receptor activity such as 5-HT potency and G-protein coupling. 5-HT_{2 C}R in the NAc is involved in enhanced alcohol drinking after chronic alcohol exposure and alterations in 5-HT_{2 C}R mRNA editing is important in determining the alcohol preference using different strains of mice and genetically modified mice. RNA editing of this receptor may participate in the development of alcoholism.

From Receptor Selectivity to Functional Selectivity: The Rise of Biased Agonism in 5-HT1A Receptor Drug Discovery

Despite extensive efforts to design serotonin 5-HT1A receptor compounds, there are currently no clinically available selective agonists to explore the therapeutic potential of activating this receptor. Commonly used drugs targeting 5-HT1A receptors, such as buspirone or other azapirone compounds, possess only limited selectivity over cross-reacting sites, act as partial agonists for 5-HT1A receptor activation, and are metabolically labile, generating active metabolites. In addition, drug discovery has been hampered by the multiplicity of 5-HT1A receptor subpopulations, expressed in different brain regions, that are coupled to distinct molecular signaling mechanisms and mediate a wide variety of physiological responses, both desired and undesired. In this context, advances in 5-HT1A receptor drug discovery have attracted attention of novel 'biased agonists' that are selective, efficacious and preferentially target the brain regions that mediate therapeutic activity without triggering side effects. The prototypical first-in-class compound NLX-101 (a.k.a. F15599; 3-chloro-4-fluorophenyl-[4-fluoro-4-[[(5-methylpyrimidin-2-ylmethyl)amino]methyl]piperidin- 1-yl]methanone), preferentially activates 5-HT1A receptors in cortical regions and exhibits potent, rapidacting and sustained antidepressant-like and procognitive properties in animal models. Here the background has been reviewed that led to the discovery of the class of 1-(1-benzoylpiperidin-4- yl)methanamine derivatives, including NLX-101, as well as recent advances in discovery of novel 5-HT1A receptor biased agonists, notably aryloxyethyl derivatives of 1‑(1-benzoylpiperidin-4yl)methanamine which show promising pharmacological activity both in vitro and in vivo. Overall, the results suggest that opportunities exist for innovative drug discovery of selective 5-HT1A receptor biased agonists that may open new avenues for the treatment of CNS disorders involving dysfunction of serotonergic neurotransmission.

Biomarkers of suicidal behaviors: A comprehensive critical review

Suicide is a relevant worldwide public health problem. Many studies have shown that different demographic and clinical factors are potentially associated with suicidal behavior. Other studies have reported data about the role of biomarkers in the onset of suicidal behaviors. Specifically, researchers have found that suicidal risk may be increased by abnormalities in serotonergic system, hypothalamic-pituitary-adrenal axis, lipid metabolism, immune system and neuronal plasticity. The identification of specific biological parameters associated with self-harm may be helpful to implement prevention strategies and also to detect new therapeutic strategies. In this review, we summarize and analyze the results of main studies about neurobiological mechanisms related to suicidal behavior, also exploring the possible interconnection between the different biological systems.

Alternative splicing in serotonergic system: Implications in neuropsychiatric disorders

BACKGROUND

The serotonergic system is a key component of physiological brain function and is essential for proper neurological activity. Numerous neuropsychiatric disorders are associated with deregulation of the serotonergic system. Accordingly, many pharmacological treatments are focused on modulation of this system. While providing a promising line of therapeutic moderation, these approaches may be complicated due to the presence of alternative splicing events for key genes in this pathway. Alternative splicing is a co-transcriptional process by which different mRNA transcripts can be produced from the same gene. These different isoforms may have diverse activities and functions, and their relative balance is often critical for the maintenance of homeostasis. Alternative splicing greatly increases the production of proteins, augmenting cell plasticity, and provides an important control point for regulation of gene expression.

AIM

The objective of this narrative review is to discuss the potential impact of alternative splicing of different components of the serotonergic system and speculate on their involvement in several neuropsychiatric disorders.

CONCLUSIONS

The specific role of each isoform in disease and their relative activities in the signalling pathways involved are yet to be determined. We need to gain a better understanding of the basis of alternative isoforms of the serotonergic system in order to fully understand their impact and be able to develop new effective pharmacological isoform-specific targets.

Brain region-specific alterations of RNA editing in PDE8A mRNA in suicide decedents

Phosphodiesterases (PDE) are key modulators of signal transduction and are involved in inflammatory cell activation, memory and cognition. There is a two-fold decrease in the expression of phosphodiesterase 8A (PDE8A) in the temporal cortex of major depressive disorder (MDD) patients. Here, we studied PDE8A mRNA-editing profile in two architectonically distinct neocortical regions in a clinically well-characterized cohort of age- and sex-matched non-psychiatric drug-free controls and depressed suicide decedents. By using capillary electrophoresis single-stranded conformational polymorphism (CE-SSCP), a previously validated technique to identify A-to-I RNA modifications, we report the full editing profile of PDE8A in the brain, including identification of two novel editing sites. Editing of PDE8A mRNA displayed clear regional difference when comparing dorsolateral prefrontal cortex (BA9) and anterior cingulate cortex (BA24). Furthermore, we report significant intra-regional differences between non-psychiatric control individuals and depressed suicide decedents, which could discriminate the two populations. Taken together, our results (i) highlight the importance of immune/inflammatory markers in major depressive disorder and suicide and (ii) establish a direct relationship between A-to-I RNA modifications of peripheral markers and A-to-I RNA editing-related modifications in brain. This work provides the first immune response-related brain marker for suicide and could pave the way for the identification of a blood-based biomarker that predicts suicidal behavior.

Caralluma fimbriata extract activity involves the 5-HT2c receptor in PWS Snord116 deletion mouse model

INTRODUCTION

In Prader-Willi syndrome (PWS), nonprotein coding small nucleolar (sno) RNAs are involved in the paternally deleted region of chromosome 15q11.2-q13, which is believed to cause the hyperphagic phenotype of PWS. Central to this is SnoRNA116. The supplement Caralluma fimbriata extract (CFE) has been shown to decrease appetite behavior in some individuals with PWS. We therefore investigated the mechanism underpinning the effect of CFE on food intake in the Snord116del mouse. Experiments utilized appetite stimulants which included a 5-hydroxytryptamine (5-HT) 2c receptor antagonist (SB242084), as the 5-HT2cR is implicated in central signaling of satiety.

METHODS

After 9-week chronic CFE treatment (33 mg or 100 mg kg^-1  day^-1 ) or placebo, the 14-week-old Snord116del (SNO) and wild-type mice (n = 72) were rotated through intraperitoneal injections of (a) isotonic saline; (b) 400 mg/kg of 2-deoxyglucose (2DG) (glucose deprivation); (c) 100 mglkg beta-mercaptoacetate (MA), fatty acid signaling; and (d) SB242084 (a selective 5HT2cR antagonist), with 5 days between reagents. Assessments of food intake were from baseline to 4 hr, followed by immunohistochemistry of neural activity utilizing c-Fos, neuropeptide Y, and alpha-melanocyte-stimulating hormone within hypothalamic appetite pathways.

RESULTS

Caralluma fimbriata extract administration decreased food intake more strongly in the SNO100CFE group with significantly stimulated food intake demonstrated during coadministration with SB242084. Though stimulatory deprivation was expected to stimulate food intake, 2DG and MA resulted in lower intake in the snord116del mice compared to the WT animals (p = <0.001). Immunohistochemical mapping of hypothalamic neural activity was consistent with the behavioral studies.

CONCLUSIONS

This study identifies a role for the 5-HT2cR in CFE-induced appetite suppression and significant stimulatory feeding disruptions in the snord116del mouse model.

The posterior pituitary expresses the serotonin receptor 2C

The serotonin receptor 2C (5HT2C) is an important drug target to treat obesity and depression. Its pre-mRNA undergoes alternative splicing, encoding a short RNA1 isoform that is localized intracellularly and a full-length isoform (RNA2) that can reach the cell membrane. These splicing isoforms are deregulated in Prader-Willi syndrome (PWS), due to the loss of a trans-acting regulatory RNA, SNORD115. Here we show that the 5HT2C mRNA is expressed in the posterior pituitary, suggesting that 5HT2C mRNA is generated in the hypothalamus and subsequently conveyed by axonal transport. In the pituitary, the ratio of 5HT2C isoforms is regulated by feeding, and can be manipulated using a splice-site changing oligonucleotide injected into the blood. The pituitary expression of the 5HT2C mRNA may constitute a previously unknown mechanism whereby serotonin in the circulation or drugs targeting the 5HT2C might induce side-effects. Finally, the deregulation of 5HT2C splicing isoforms in PWS could contribute to the known hormonal imbalances.

Neuronal differentiation induces SNORD115 expression and is accompanied by post-transcriptional changes of serotonin receptor 2c mRNA

The serotonin neurotransmitter system is widespread in the brain and implicated in modulation of neuronal responses to other neurotransmitters. Among 14 serotonin receptor subtypes, 5-HT2cR plays a pivotal role in controlling neuronal network excitability. Serotonergic activity conveyed through receptor 5-HT2cR is regulated post-transcriptionally via two mechanisms, alternative splicing and A-to-I RNA editing. Brain-specific small nucleolar RNA SNORD115 harbours a phylogenetically conserved 18-nucleotide antisense element with perfect complementarity to the region of 5ht2c primary transcript that undergoes post-transcriptional changes. Previous 5ht2c minigene studies have implicated SNORD115 in fine-tuning of both post-transcriptional events. We monitored post-transcriptional changes of endogenous 5ht2c transcripts during neuronal differentiation. Both SNORD115 and 5ht2c were upregulated upon neuronal commitment. We detected increased 5ht2c alternative exon Vb inclusion already at the stage of neuronal progenitors, and more extensive A-to-I editing of non-targeted sites A and B compared to adjacent adenosines at sites E, C and D throughout differentiation. As the extent of editing is known to positively correlate with exon Vb usage while it reduces receptor functionality, our data support the model where SNORD115 directly promotes alternative exon inclusion without the requirement for conversion of key adenosines to inosines, thereby favouring production of full-length receptor isoforms with higher potency.