Inhibition of Trpv4 rescues circuit and social deficits unmasked by acute inflammatory response in a Shank3 mouse model of Autism

Activation of transient receptor potential vanilloid 4 impairs long-term depression in nucleus accumbens and induces depressive-like behavior

Long-term depression (LTD), a form of synaptic plasticity, is impaired in the nucleus accumbens (NAc) in depression. While TRPV4 activation regulates synaptic transmission in the hippocampus, its effects in the NAc remain unclear. Here, we examined the effects of TRPV4 activation on LTD induction in the NAc and depressive-like behavior. Mice that were administered the TRPV4 agonist GSK1016790A into the NAc (GSK-mice) showed depressive-like behavior and impaired LTD induction in NAc slices. Additionally, the mRNA and protein levels of dopamine D2 receptor (D2R) and A-type gamma-aminobutyric acid receptor (GABAAR) were markedly decreased in the NAc of GSK-mice. Meanwhile, administering a D2R (quinpirole) or GABAAR (muscimol) agonist reversed LTD impairment in the NAc. The protein levels of phosphorylated protein kinase C (p-PKC) increased markedly and that of phosphorylated protein kinase B (p-Akt) decreased in the NAc of GSK mice. Administration of a PKC antagonist (GF109203X) or phosphatidylinositol 3-kinase (PI3K) agonist (740 Y-P) significantly increased GABAAR protein levels and restored LTD induction in the NAc of GSK-mice. Administration of quinpirole increased p-Akt and GABAAR protein levels in the NAc of GSK-mice. Finally, administration of quinpirole, muscimol, GF109203X or 740 Y-P improved the depressive-like behavior in GSK-mice. This study suggests that activation of TRPV4 impairs LTD induction in the NAc and induces depressive-like behavior, which is likely mediated by down-regulating D2R to inhibit PI3K-Akt pathway, and activating PKC to decrease the expression of GABAAR.

A Drd1-cre mouse line with nucleus accumbens gene dysregulation exhibits blunted fentanyl seeking

The synthetic opioid fentanyl remains abundant in the illicit drug supply, contributing to tens of thousands of overdose deaths every year. Despite this, the neurobiological effects of fentanyl use remain largely understudied. The nucleus accumbens (NAc) is a central locus promoting persistent drug use and relapse, largely dependent on activity of dopamine D1 receptors. NAc D1 receptor-expressing medium spiny neurons (D1-MSNs) undergo molecular and physiological neuroadaptations in response to chronic fentanyl that may promote relapse. Here, we obtained Drd1-cre120Mxu mice to investigate D1-dependent mechanisms of fentanyl relapse. We serendipitously discovered this mouse line has reduced fentanyl seeking, despite similar intravenous fentanyl self-administration, similar sucrose self-administration and seeking, and greater fentanyl-induced locomotion compared to wildtype counterparts. We found drug-naïve Drd1-cre120Mxu mice have elevated D1 receptor expression in NAc and increased sensitivity to the D1 receptor agonist SKF-38393. After fentanyl self-administration, Drd1-cre120Mxu mice exhibit divergent expression of MSN markers, opioid receptors, glutamate receptor subunits, and TrkB which may underly their blunted fentanyl seeking. Finally, we show fentanyl-related behavior is unaltered by chemogenetic manipulation of NAc core D1-MSNs in Drd1-cre120Mxu mice. Conversely, chemogenetic stimulation of ventral mesencephalon-projecting NAc core MSNs (putative D1-MSNs) in wildtype mice recapitulated the blunted fentanyl seeking of Drd1-cre120Mxu mice, supporting a role for aberrant D1-MSN signaling in this behavior. Together, our data uncover alterations in NAc gene expression and function with implications for susceptibility and resistance to developing fentanyl use disorder.

Shank3 mutation manifests in abnormal gastrointestinal morphology and function in mice

Background

Gastrointestinal (GI) comorbidities are common among those with Autism Spectrum Disorder (ASD), but their etiology is not well understood. This study aimed to characterize gastrointestinal morphology and function in Shank3B mutant mice, a common genetic model of ASD, to identify potential alterations to the GI tract that could underlie ASD-associated GI comorbidities.

Methods

GI and enteric nervous system morphology was characterized using Hematoxylin and Eosin staining and immunohistochemistry. GI permeability was measured using the FITC-Dextran paracellular permeability assay. Whole-GI tract motility time was measured in vivo using the carmine dye motility assay. Colonic contractions were characterized by tracking motility using an ex vivo motility assay.

Results

Homozygous knock-out (KO) Shank3B-/- mice exhibit significantly altered epithelial morphology and increased GI permeability. An increased myenteric plexus density and a higher number of HuC/D-expressing neurons in myenteric ganglia are observed in the colon of Shank3B-/- mice. These mice exhibit slowed whole-GI tract transit and reduced velocity and propagation length of colonic contractions. Compared to Shank3B-/- mice, heterozygous Shank3B+/- mice exhibit milder epithelial, neuronal, and functional alterations.

Conclusion

Shank3B-/- mice exhibit altered GI morphology and function, while Shank3B+/- mice exhibit a partial phenotype. These results indicate that Shank3, whose mutation is associated with ASD, is critical for function of the GI tract and its mutation may contribute to the etiology of GI comorbidities.

Translational research approach to social orienting deficits in autism: the role of superior colliculus-ventral tegmental pathway

Autism Spectrum Disorder (ASD) is characterized by impairments in social interaction and repetitive behaviors. A key characteristic of ASD is a decreased interest in social interactions, which affects individuals' ability to engage with their social environment. This study explores the neurobiological basis of these social deficits, focusing on the pathway between the Superior Colliculus (SC) and the Ventral Tegmental Area (VTA). Adopting a translational approach, our research used Shank3 knockout mice (Shank3-/-), which parallel a clinical cohort of young children with ASD, to investigate these mechanisms. We observed consistent deficits in social orienting across species. In children with ASD, fMRI analyses revealed a significant decrease in connectivity between the SC and VTA. Additionally, using miniscopes in mice, we identified a reduction in the frequency of calcium transients in SC neurons projecting to the VTA, accompanied by changes in neuronal correlation and intrinsic cellular properties. Notably, the interneuronal correlation in Shank3-/- mice and the functional connectivity of the SC to VTA pathway in children with ASD correlated with the severity of social deficits. Our findings underscore the potential of the SC-VTA pathway as a biomarker for ASD and open new avenues for therapeutic interventions, highlighting the importance of early detection and targeted treatment strategies.

TRPV4 Channel in Neurological Disease: from Molecular Mechanisms to Therapeutic Potential

Transient Receptor Potential Vanilloid 4 (TRPV4) is a non-selective cation channel with pivotal roles in various physiological processes, including osmosensitivity, mechanosensation, neuronal development, vascular tone regulation, and bone homeostasis in human bodies. Recent studies have made significant progress in understanding the structure and functional role of TRPV4, shedding light on its involvement in pathological processes, particularly in the realm of neurological diseases. Here, we aim to provide a comprehensive exploration of the multifaceted contributions of TRPV4 to neurological diseases, spanning its intricate molecular mechanisms to its potential as a target for therapeutic interventions. We delve into the structural and functional attributes of TRPV4, scrutinize its expression profile, and elucidate the possible mechanisms through which it participates in the pathogenesis of neurological disorders. Furthermore, we discussed recent years' progress in therapeutic strategies aimed at harnessing TRPV4 for the treatment of these diseases. These insights will provide a basis for understanding and designing modality-specific pharmacological agents to treat TRPV4-associated disorders.

A Drd1-cre mouse line with nucleus accumbens gene dysregulation exhibits blunted fentanyl seeking

The synthetic opioid fentanyl remains abundant in the illicit drug supply, contributing to tens of thousands of overdose deaths every year. Despite this, the neurobiological effects of fentanyl use remain largely understudied. The nucleus accumbens (NAc) is a central locus promoting persistent drug use and relapse, largely dependent on activity of dopamine D1 receptors. NAc D1 receptor-expressing medium spiny neurons (D1-MSNs) undergo molecular and physiological adaptations that contribute to negative affect during fentanyl abstinence, but whether these neuroadaptations also promote fentanyl relapse is unclear. Here, we obtained Drd1-cre 120Mxu mice to investigate D1-dependent mechanisms of fentanyl relapse. We serendipitously discovered this mouse line is resistant to fentanyl seeking, despite similar intravenous fentanyl self-administration, and greater fentanyl-induced locomotion, compared to wildtype counterparts. In drug naïve mice, we found Drd1-cre 120Mxu mice have elevated D1 receptor expression in NAc, alongside increased expression of MSN marker genes Chrm4 and Penk . We show Drd1-cre 120Mxu mice have increased sensitivity to the D1 receptor agonist SKF-38393, and exhibit divergent expression of MSN markers, opioid receptors, glutamate receptor subunits, and TrkB after fentanyl self-administration that may underly blunted fentanyl seeking. Finally, we show fentanyl-related behavior is unaltered by chemogenetic manipulation of D1-MSNs in Drd1-cre 120Mxu mice. Conversely, chemogenetic stimulation of putative D1-MSNs in wildtype mice recapitulated the blunted fentanyl seeking of Drd1-cre 120Mxu mice, supporting a role for aberrant D1-MSN signaling in this behavior. Together, our data uncover alterations in NAc gene expression and function with implications for susceptibility and resistance to developing fentanyl use disorder.

Metalomics Revealed that Changes of Serum Elements were Associated with Oxidative Stress-Induced Inflammation of Cortex in a Mouse Model of Autism

Autism spectrum disorder (ASD) is a neurodevelopmental disorder emerging during early childhood. However, the mechanism underlying the pathogenesis of ASD remains unclear. This study investigated the alterations of elements in serum and prefrontal cortex of BTBR T + tf/J (BTBR) mice and potential mechanisms. The male BTBR mice were used for experimental group and C57BL/6 J (C57) mice were used for control group (n = 15). After behavioral tests were monitored, serum and prefrontal cortex of mice were analyzed by ICP-MS. The results demonstrated that the level of copper (Cu) was increased, and the levels of calcium (Ca), magnesium (Mg), selenium (Se), cobalt (Co), iron (Fe) and zinc (Zn) were decreased in BTBR mice compared to C57 mice (p < 0.01). The levels of above differential elements in serum demonstrated positive correlations with those in prefrontal cortex. Meanwhile, differential elements in prefrontal cortex had correlations with the total distance traveled (open field test) and the number of marbles buried (marble burying test) in BTBR mice (p < 0.05 or p < 0.01). The abnormally changed elements in serum might cross blood-brain-barrier into the brain and lead to oxidative stress, causing inflammation. Furtherly, the levels of inflammation-related indicators including tumor necrosis factor-alpha (TNF-α), nuclear factor kappa-B (NF-κB), interleukin-6 (IL-6) and interleukin-1β (IL-1β) were increased in prefrontal cortex of BTBR mice (p < 0.01), which were consistent with the aforementioned results. Our study suggested that the abnormal elements in the serum of BTBR mice may cause oxidative stress and inflammation in prefrontal cortex, which might contribute to increase the understanding of ASD pathogenesis.

Evidence for common mechanisms of pathology between SHANK3 and other genes of Phelan-McDermid syndrome

Chromosome 22q13.3 deletion (Phelan-McDermid) syndrome (PMS, OMIM 606232) is a rare genetic condition that impacts neurodevelopment. PMS most commonly results from heterozygous contiguous gene deletions that include the SHANK3 gene or likely pathogenic variants of SHANK3 (PMS-SHANK3 related). Rarely, chromosomal rearrangements that spare SHANK3 share the same general phenotype (PMS-SHANK3 unrelated). Very recent human and model system studies of genes that likely contribute to the PMS phenotype point to overlap in gene functions associated with neurodevelopment, synaptic formation, stress/inflammation and regulation of gene expression. In this review of recent findings, we describe the functional overlaps between SHANK3 and six partner genes of 22q13.3 (PLXNB2, BRD1, CELSR1, PHF21B, SULT4A1, and TCF20), which suggest a model that explains the commonality between PMS-SHANK3 related and PMS-SHANK3 unrelated classes of PMS. These genes are likely not the only contributors to neurodevelopmental impairments in the region, but they are the best documented to date. The review provides evidence for the overlapping and likely synergistic contributions of these genes to the PMS phenotype.

Balance Between Projecting Neuronal Populations of the Nucleus Accumbens Controls Social Behavior in Mice

BACKGROUND

Deficient social interactions are a hallmark of major neuropsychiatric disorders, and accumulating evidence points to altered social reward and motivation as key underlying mechanisms of these pathologies. In the present study, we further explored the role of the balance of activity between D1 and D2 receptor-expressing striatal projection neurons (D1R- and D2R-SPNs) in the control of social behavior, challenging the hypothesis that excessive D2R-SPN activity, rather than deficient D1R-SPN activity, compromises social behavior.

METHODS

We selectively ablated D1R- and D2R-SPNs using an inducible diphtheria toxin receptor-mediated cell targeting strategy and assessed social behavior as well as repetitive/perseverative behavior, motor function, and anxiety levels. We tested the effects of optogenetic stimulation of D2R-SPNs in the nucleus accumbens (NAc) and pharmacological compounds repressing D2R-SPN.

RESULTS

Targeted deletion of D1R-SPNs in the NAc blunted social behavior in mice, facilitated motor skill learning, and increased anxiety levels. These behaviors were normalized by pharmacological inhibition of D2R-SPN, which also repressed transcription in the efferent nucleus, the ventral pallidum. Ablation of D1R-SPNs in the dorsal striatum had no impact on social behavior but impaired motor skill learning and decreased anxiety levels. Deletion of D2R-SPNs in the NAc produced motor stereotypies but facilitated social behavior and impaired motor skill learning. We mimicked excessive D2R-SPN activity by optically stimulating D2R-SPNs in the NAc and observed a severe deficit in social interaction that was prevented by D2R-SPN pharmacological inhibition.

CONCLUSIONS

Repressing D2R-SPN activity may represent a promising therapeutic strategy to relieve social deficits in neuropsychiatric disorders.

The cortico-striatal circuitry in autism-spectrum disorders: a balancing act

The basal ganglia are major targets of cortical inputs and, in turn, modulate cortical function via their projections to the motor and prefrontal cortices. The role of the basal ganglia in motor control and reward is well documented and there is also extensive evidence that they play a key role in social and repetitive behaviors. The basal ganglia influence the activity of the cerebral cortex via two major projections from the striatum to the output nuclei, the globus pallidus internus and the substantia nigra, pars reticulata. This modulation involves a direct projection known as the direct pathway and an indirect projection via the globus pallidus externus and the subthalamic nucleus, known as the indirect pathway. This review discusses the respective contribution of the direct and indirect pathways to social and repetitive behaviors in neurotypical conditions and in autism spectrum disorders.

The PFC-LH-VTA pathway contributes to social deficits in IRSp53-mutant mice

Dopamine (DA) neurons in the ventral tegmental area (VTA) promote social brain functions by releasing DA onto nucleus accumbens neurons, but it remains unclear how VTA neurons communicate with cortical neurons. Here, we report that the medial prefrontal cortex (mPFC)-lateral hypothalamus (LH)-VTA pathway contributes to social deficits in mice with IRSp53 deletion restricted to cortical excitatory neurons (Emx1-Cre;Irsp53fl/fl mice). LH-projecting mutant mPFC neurons display abnormally increased excitability involving decreased potassium channel gene expression, leading to excessive excitatory synaptic input to LH-GABA neurons. A circuit-specific IRSp53 deletion in LH-projecting mPFC neurons also increases neuronal excitability and induces social deficits. LH-GABA neurons with excessive mPFC excitatory synaptic input show a compensatory decrease in excitability, weakening the inhibitory LHGABA-VTAGABA pathway and subsequently over-activating VTA-GABA neurons and over-inhibiting VTA-DA neurons. Accordingly, optogenetic activation of the LHGABA-VTAGABA pathway improves social deficits in Emx1-Cre;Irsp53fl/fl mice. Therefore, the mPFC-LHGABA-VTAGABA-VTADA pathway contributes to the social deficits in Emx1-Cre;Irsp53fl/fl mice.

The dopamine hypothesis of autism spectrum disorder: A comprehensive analysis of the evidence

Despite intensive research into the etiopathogenesis of autism spectrum disorder (ASD), limited progress has been achieved so far. Among the plethora of models seeking to clarify how ASD arises, a coherent dopaminergic model was lacking until recently. In 2017, we provided a theoretical framework that we designated "the dopamine hypothesis of ASD". In the meantime, numerous studies yielded empirical evidence for this model. 4 years later, we provided a second version encompassing a refined and reconceptualized framework that accounted for these novel findings. In this chapter, we will review the evidence backing the previous versions of our model and add the most recent developments to the picture. Along these lines, we intend to lay out a comprehensive analysis of the supporting evidence for the dopamine hypothesis of ASD.

Maturation of nucleus accumbens synaptic transmission signals a critical period for the rescue of social deficits in a mouse model of autism spectrum disorder

Social behavior emerges early in development, a time marked by the onset of neurodevelopmental disorders featuring social deficits, including autism spectrum disorder (ASD). Although social deficits are at the core of the clinical diagnosis of ASD, very little is known about their neural correlates at the time of clinical onset. The nucleus accumbens (NAc), a brain region extensively implicated in social behavior, undergoes synaptic, cellular and molecular alterations in early life, and is particularly affected in ASD mouse models. To explore a link between the maturation of the NAc and neurodevelopmental deficits in social behavior, we compared spontaneous synaptic transmission in NAc shell medium spiny neurons (MSNs) between the highly social C57BL/6J and the idiopathic ASD mouse model BTBR T⁺Itpr3^tf/J at postnatal day (P) 4, P6, P8, P12, P15, P21 and P30. BTBR NAc MSNs display increased spontaneous excitatory transmission during the first postnatal week, and increased inhibition across the first, second and fourth postnatal weeks, suggesting accelerated maturation of excitatory and inhibitory synaptic inputs compared to C57BL/6J mice. BTBR mice also show increased optically evoked medial prefrontal cortex-NAc paired pulse ratios at P15 and P30. These early changes in synaptic transmission are consistent with a potential critical period, which could maximize the efficacy of rescue interventions. To test this, we treated BTBR mice in either early life (P4-P8) or adulthood (P60-P64) with the mTORC1 antagonist rapamycin, a well-established intervention for ASD-like behavior. Rapamycin treatment rescued social interaction deficits in BTBR mice when injected in infancy, but did not affect social interaction in adulthood.

Acute cannabidiol treatment enhances social interaction in adult male mice

Cannabidiol (CBD) is a non-intoxicating phytochemical from Cannabis sativa that is increasingly used to manage pain. The potential for CBD to ameliorate dimensional behavior symptoms occurring in multiple psychiatric disorders was suggested, including social interaction impairments. To test this hypothesis, adult male BTBRT+Itpr3tf/J (BTBR) mice, a model of idiopathic autism exhibiting social preference deficits and restrictive repetitive behaviors, were acutely treated with vehicle or 0.1, 1, or 10 mg/kg CBD. Social interaction preference was assessed 50 min after treatment, followed by social novelty preference at 60 min, marble burying at 75 min and social dominance at 120 min. CBD (10 mg/kg) enhanced BTBR social interaction but not social novelty preference, marble burying or dominance, with serum levels = 29 ± 11 ng/mg at 3 h post-injection. Next, acute 10 mg/kg CBD was compared to vehicle treatment in male serotonin transporter (SERT) knock-out mice, since SERT deficiency is an autism risk factor, and in their wildtype background strain controls C57BL/6J mice. CBD treatment generally enhanced social interaction preference and attenuated social novelty preference, yet neither marble burying nor dominance was affected. These findings show acute treatment with as little as 10 mg/kg purified CBD can enhance social interaction preference in male mice that are otherwise socially deficient.

Identification and characterization of circular RNA in the model of autism spectrum disorder from PM2.5 exposure

PM_2.5 induces a series of effects on neurological disorders, including autism spectrum disorder (ASD), however, the mechanism is not completely clear yet. Circular RNAs (circRNAs) are a class of closed-loop structures that can be stably expressed in vivo. In our experiments, rats exposed to PM_2.5 exhibited autism-like phenotypes, such as anxiety, and memory loss. To explore the etiology, we performed transcriptome sequencing and found significant differences in the expression of circRNA. A total of 7770 circRNAs were identified between the control and experimental groups, 18 of which were differentially expressed, we selected ten circRNAs and performed qRT-PCR and Sanger sequencing to validate them. By GO and KEGG enrichment analysis, we found differentially expressed circRNAs that were mainly enriched in processes related to placental development and reproduction. Finally, using bioinformatics, we predicted miRNAs and mRNAs that circ-Mbd5 and circ-Ash1l might regulate and constructed circRNA-miRNA-mRNA networks involving genes associated with ASD, suggesting that circRNAs might regulate the occurrence of ASD.

SHANK3 in vagal sensory neurons regulates body temperature, systemic inflammation, and sepsis

Excessive inflammation has been implicated in autism spectrum disorder (ASD), but the underlying mechanisms have not been fully studied. SHANK3 is a synaptic scaffolding protein and mutations of SHANK3 are involved in ASD. Shank3 expression in dorsal root ganglion sensory neurons also regulates heat pain and touch. However, the role of Shank3 in the vagus system remains unknown. We induced systemic inflammation by lipopolysaccharide (LPS) and measured body temperature and serum IL-6 levels in mice. We found that homozygous and heterozygous Shank3 deficiency, but not Shank2 and Trpv1 deficiency, aggravates hypothermia, systemic inflammation (serum IL-6 levels), and sepsis mortality in mice, induced by lipopolysaccharide (LPS). Furthermore, these deficits can be recapitulated by specific deletion of Shank3 in Nav1.8-expressing sensory neurons in conditional knockout (CKO) mice or by selective knockdown of Shank3 or Trpm2 in vagal sensory neurons in nodose ganglion (NG). Mice with Shank3 deficiency have normal basal core temperature but fail to adjust body temperature after perturbations with lower or higher body temperatures or auricular vagus nerve stimulation. In situ hybridization with RNAscope revealed that Shank3 is broadly expressed by vagal sensory neurons and this expression was largely lost in Shank3 cKO mice. Mechanistically, Shank3 regulates the expression of Trpm2 in NG, as Trpm2 but not Trpv1 mRNA levels in NG were significantly reduced in Shank3 KO mice. Our findings demonstrated a novel molecular mechanism by which Shank3 in vagal sensory neurons regulates body temperature, inflammation, and sepsis. We also provided new insights into inflammation dysregulation in ASD.

Evidence that GIRK Channels Mediate the DREADD-hM4Di Receptor Activation-Induced Reduction in Membrane Excitability of Striatal Medium Spiny Neurons

The hM4Di receptor-based chemogenetic DREADD system has been widely used to suppress neuronal activities, which has contributed substantially to the identification of behavior-associated neuronal circuitries including those in the striatum. One major mechanism by which hM4Di receptor activation suppresses neuronal activity is that the activation reduces membrane excitability, which is thought to be mediated by the opening of GIRK channels. However, previous studies have suggested that GIRK channels are barely expressed in the striatum, which naturally raises the question whether the hM4Di receptor activation-induced reduction in membrane excitability found in striatal medium spiny neurons (MSNs, which constitute 95-98% of the striatal neuronal population) is truly mediated by the endogenous GIRK channels in such scarcity. This study aims to answer this question by applying a GIRK channel-selective blocker, tertiapin-Q (TPNQ), to striatal MSNs. This study first verified that application of clozapine (CZP), an hM4Di receptor agonist, to MSNs expressing the hM4Di receptors hyperpolarized the cell membrane, and reduced membrane excitability and input resistance. This study next revealed that TPNQ post-treatment completely canceled the above CZP-induced electrophysiological effects and that TPNQ pretreatment mostly prevented further expression of the above CZP-induced electrophysiological effects. In addition, confocal microscopy imaging also revealed significant above-background GIRK1 immunofluorescence signals in striatal MSNs. These data suggest that the TPNQ-sensitive GIRK channels, despite being expressed at low levels, are likely the major mediator downstream of hM4Di receptor activation to reduce membrane excitability in striatal MSNs. These results imply that the notion held by scientists in the field that GIRK channels are absent in the striatum or their expression level is not significant enough to exert any function might be oversimplified or incorrect.

Phenotypic Variability in Phelan–McDermid Syndrome and Its Putative Link to Environmental Factors

Phelan–McDermid syndrome (PMS) is a multi-systemic disorder characterized by both genetic and phenotypic variability. Genetic abnormalities causing PMS span from pathogenic variants of the SHANK3 gene to chromosomal rearrangements affecting the 22q13 region and leading to the loss of up to over nine megabases. The clinical presentation of individuals with PMS includes intellectual disability, neonatal hypotonia, delayed or absent speech, developmental delay, and minor dysmorphic facial features. Several other features may present with differences in age of onset and/or severity: seizures, autism, regression, sleep disorders, gastrointestinal problems, renal disorders, dysplastic toenails, and disrupted thermoregulation. Among the causes of this phenotypic variability, the size of the 22q13 deletion has effects that may be influenced by environmental factors interacting with haploinsufficiency or hemizygous variants of certain genes. Another mechanism linking environmental factors and phenotypic variability in PMS involves the loss of one copy of genes like BRD1 or CYP2D6, located at 22q13 and involved in the regulation of genomic methylation or pharmacokinetics, which are also influenced by external agents, such as diet and drugs. Overall, several non-mutually exclusive genetic and epigenetic mechanisms interact with environmental factors and may contribute to the clinical variability observed in individuals with PMS. Characterization of such factors will help to better manage this disorder.