Molecular and Neural Functions of Rai1, the Causal Gene for Smith-Magenis Syndrome

ADAR3 modulates neuronal differentiation and regulates mRNA stability and translation

ADAR3 is a catalytically inactive member of the family of adenosine deaminases acting on RNA (ADARs). Here we have investigated its function in the context of the developing mouse brain. The expression of ADAR3 gradually increases throughout embryogenesis and drops after birth. Using primary cortical neurons, we show that ADAR3 is only expressed in a subpopulation of in vitro differentiated neurons, which suggests specific functions rather than being a general regulator of ADAR editing in the brain. The analysis of the ADAR3 interactome suggested a role in mRNA stability and translation, and we show that expression of ADAR3 in a neuronal cell line that is otherwise ADAR3-negative changes the expression and stability of a large number of mRNAs. Notably, we show that ADAR3 associates with polysomes and inhibits translation. We propose that ADAR3 binds to target mRNAs and stabilizes them in non-productive polysome complexes. Interestingly, the expression of ADAR3 downregulates genes related to neuronal differentiation and inhibits neurofilament outgrowth in vitro. In summary, we propose that ADAR3 negatively regulates neuronal differentiation, and that it does so by regulating mRNA stability and translation in an editing-independent manner.

Tunable, self-contained gene dosage control via proteolytic cleavage of CRISPR-Cas systems

Gene therapy holds great therapeutic potential. Yet, controlling cargo expression in single cells is limited due to the variability of delivery methods. We implement an incoherent feedforward loop based on proteolytic cleavage of CRISPR-Cas activation or inhibition systems to reduce gene expression variability against the variability of vector delivery. We demonstrate dosage control for activation and inhibition, post-delivery tuning, and RNA-based delivery, for a genome-integrated marker. We then target the RAI1 gene, the haploinsufficiency and triplosensitivity of which cause two autism-related syndromes, Smith-Magenis-Syndrome (SMS) and Potocki-Lupski-Syndrome, respectively. We demonstrate dosage control for RAI1 activation in HEK293s, Neuro-2As, and mouse cortical neurons via AAVs and lentiviruses. Finally, we activate the intact RAI1 copy in SMS patient-derived cells to an estimated two-copy healthy range, avoiding the harmful three-copy regime. Our circuit paves the way for viable therapy in dosage-sensitive disorders, creating precise and tunable gene regulation systems for basic and translational research.

Brain Specific RagA Overexpression Triggers Depressive-Like Behaviors in Mice via Activating ADORA2A Signaling Pathway

Neuroinflammation hallmarks the pathology of depression although the etiological complexity has not yet been resolved. Previous studies demonstrate that bacterial lipopolysaccharide induces depressive-like behaviors by activating RagA-mTOR-p70S6K signaling pathway. The current project aims to investigate whether and how brain-specific RagA overexpression triggers depressive-like behaviors in mice. Full-length RagA cDNA is cloned into the mammalian expression vector under the control of brain specific promoter, and subsequently overexpressed in the brain of mouse embryos. Indeed, RagA transgenic mice exhibit depressive-like behaviors and memory impairments. RNA-seq profiling of the prefrontal cortex (PFC) transcriptome highlights adenosine A2a receptor (ADORA2A) as a key differentially expressed gene (DEG). Western blotting confirms that ADORA2A and phospho-p70S6K are markedly elevated in RagA transgenic mice. Behavioral assessments demonstrate that ADORA2A inhibitor istradefylline markedly attenuates depressive-like behaviors. Further metabolomics reveals that N-acetylserotonin and several depression-related metabolites are downregulated while proteomic profiling showed that OLIG1 and other proteins are significantly regulated in RagA transgenic mice. Collectively, RagA overexpression alters the expression patterns of signaling proteins and the metabolism of depression-associated metabolites. RagA may cause depressive-like behaviors in mice via activating p70S6K/ADORA2A signaling pathway. Thus, RagA-p70S6K-ADORA2A signaling pathway may be a target for the development of new antidepressant therapies.

Overlapping hearing and communication profiles for the deletion and the RAI1 variant form of Smith-Magenis Syndrome (SMS)

Smith-Magenis syndrome (SMS), a rare, genetically linked complex developmental disorder is associated with hearing loss and delays in speech-language development. Approximately 70 % of those with SMS have a genetic deletion within chromosome 17p11.2 and 10 % have a single gene mutation in the same area, known as the RAI1 variant form of SMS. Previous studies presented preliminary comparisons of the phenotype of those with deletion versus the mutation form of SMS, but none focused on hearing, speech-language, and communication profiles. The current study examined patient registry data and compared two groups of individuals with SMS to determine if genetic differences influence the communication phenotype and to determine the importance of the RAI1 gene in hearing, speech, and language abilities in children. Speech-language and hearing data from the international SMS Patient Registry for 33 subjects with SMS were analyzed: 23 with a genetic deletion (SMS (del)) and 10 with an RAI1 mutation (SMS (RAI1)). Hearing status, otopathology findings, early speech-language milestones, mode of communication, intelligibility, vocal quality, language abilities, and literacy skills were analyzed. There were small differences between the groups for hearing status, otopathological findings, mode of communication, voice quality, intelligibility, speech-language abilities, and literacy. Overlap in the speech-language phenotype between groups confirms previous hypotheses that suggest haploinsufficiency of the RAI1 gene is responsible for the SMS phenotype and that the RAI1 gene is critical for speech-language development. Future studies should include direct testing of receptive and expressive language abilities, including analyses of language samples, with larger groups of individuals to replicate and extend the current findings.

Mechanistic perspective on the actions of vitamin a in autism spectrum disorder etiology

Vitamin A (VA) has many functions in the body, some of which are key for the development and functioning of the nervous system, while some others might indirectly influence neural function. Both hypovitaminosis and hypervitaminosis A can lead to clinical manifestations of concern for individuals and for general global health. Scientific evidence on the link between VA and autism spectrum disorder (ASD) is growing, with some clinical studies and accumulating results obtained from basic research using cellular and animal models. Remarkably, it has been shown that VA deficiency can exacerbate autistic symptomatology. In turn, VA supplementation has been shown to be able to improve autistic symptomatology in selected groups of individuals with ASD. However, it is important to recognize that ASD is a highly heterogeneous condition. Therefore, it is important to clarify how and when VA supplementation can be of benefit for affected individuals. Here we delve into the relationship between VA and ASD, discussing clinical observations and mechanistic insights obtained from research on selected autistic syndromes and laboratory models to advance in defining how the VA signaling pathway can be exploited for treatment of ASD.

A novel partnership between lncTCF7 and SND1 regulates the expression of the TCF7 gene via recruitment of the SWI/SNF complex

Long non-coding RNAs (lncRNAs) play key roles in cellular pathways and disease progression, yet their molecular mechanisms remain largely understudied. The lncRNA lncTCF7 has been shown to promote tumor progression by recruiting the SWI/SNF complex to the TCF7 promoter, activating its expression and the WNT signaling pathway. However, how lncTCF7 recruits SWI/SNF remains to be determined, and lncTCF7-specific binding partners are unknown. Using RNA-pulldown and quantitative mass spectrometry, we identified a novel interacting protein partner for lncTCF7, SND1, a multifunctional RNA binding protein that can also function as a transcription co-activator. Knockdown analysis of lncTCF7 and SND1 reveals that they are both required for the expression of TCF7. Chromatin immunoprecipitation assays suggest that both SND1 and lncTCF7 are required for recruiting the SWI/SNF chromatin remodeling complex, and these functions, in tandem, activate the expression of TCF7. Finally, using structural probing and RNA-pulldown of lncTCF7 and its subdomains, we highlight the potential binding region for SND1 in the 3'-end of lncTCF7. Overall, this study highlights the critical roles lncRNAs play in regulating gene expression and provides new insights into the complex network of interactions that underlie this process.

Allele-Specific Regulation of the Candidate Autism Liability Gene RAI1 by the Enhancer Variant rs4925102 (C/G)

Retinoic acid-induced 1 (RAI1) is a dosage-sensitive gene that causes autistic phenotypes when deleted or duplicated. Observations from clinical cases and animal models also suggest that changes of RAI1 expression levels contribute to autism. Previously, we used a bioinformatic approach to identify several single nucleotide polymorphisms (SNPs) located within the 5'-region of RAI1 that correlate with RAI1 mRNA expression in the human brain. In particular, the SNP rs4925102 was identified as a candidate cis-acting regulatory variant, the genotype of which may affect the binding of transcription factors that influence RAI1 mRNA expression. In this study, we provide experimental evidence based on reporter gene, chromatin immunoprecipitation (ChIP), and chromatin conformation capture (3C) assays that rs4925102 regulates RAI1 mRNA expression in an allele-specific manner in human cell lines, including the neuroblastoma-derived cell line SH-SY5Y. We also describe a statistically significant association between rs4925102 genotype and autism spectrum disorder (ASD) diagnosis in a case-control study and near-statistically significant association in an Autism Genome Project (AGP) transmission disequilibrium (TDT) study using Caucasian subjects.

Comprehensive analysis of the proximity-dependent nuclear interactome for the oncoprotein NOTCH1 in live cells

Notch signaling plays a critical role in cell fate decisions in all cell types. Furthermore, gain-of-function mutations in NOTCH1 have been uncovered in many human cancers. Disruption of Notch signaling has recently emerged as an attractive disease treatment strategy. However, the nuclear interaction landscape of the oncoprotein NOTCH1 remains largely unexplored. We therefore employed here a proximity-dependent biotin identification approach to identify in vivo protein associations with the nuclear Notch1 intracellular domain in live cells. We identified a large set of previously reported and unreported proteins that associate with NOTCH1, including general transcription and elongation factors, DNA repair and replication factors, coactivators, corepressors, and components of the NuRD and SWI/SNF chromatin remodeling complexes. We also found that Notch1 intracellular domain associates with protein modifiers and components of other signaling pathways that may influence Notch signal transduction and protein stability such as USP7. We further validated the interaction of NOTCH1 with histone deacetylase 1 or GATAD2B using protein network analysis, proximity-based ligation, in vivo cross-linking and coimmunoprecipitation assays in several Notch-addicted cancer cell lines. Through data mining, we also revealed potential drug targets for the inhibition of Notch signaling. Collectively, these results provide a valuable resource to uncover the mechanisms that fine-tune Notch signaling in tumorigenesis and inform therapeutic targets for Notch-addicted tumors.

Comparative analyses of the Smith-Magenis syndrome protein RAI1 in mice and common marmoset monkeys

Retinoic acid-induced 1 (RAI1) encodes a transcriptional regulator critical for brain development and function. RAI1 haploinsufficiency in humans causes a syndromic autism spectrum disorder known as Smith-Magenis syndrome (SMS). The neuroanatomical distribution of RAI1 has not been quantitatively analyzed during the development of the prefrontal cortex, a brain region critical for cognitive function and social behaviors and commonly implicated in autism spectrum disorders, including SMS. Here, we performed comparative analyses to uncover the evolutionarily convergent and divergent expression profiles of RAI1 in major cell types during prefrontal cortex maturation in common marmoset monkeys (Callithrix jacchus) and mice (Mus musculus). We found that while RAI1 in both species is enriched in neurons, the percentage of excitatory neurons that express RAI1 is higher in newborn mice than in newborn marmosets. By contrast, RAI1 shows similar neural distribution in adult marmosets and adult mice. In marmosets, RAI1 is expressed in several primate-specific cell types, including intralaminar astrocytes and MEIS2-expressing prefrontal GABAergic neurons. At the molecular level, we discovered that RAI1 forms a protein complex with transcription factor 20 (TCF20), PHD finger protein 14 (PHF14), and high mobility group 20A (HMG20A) in the marmoset brain. In vitro assays in human cells revealed that TCF20 regulates RAI1 protein abundance. This work demonstrates that RAI1 expression and protein interactions are largely conserved but with some unique expression in primate-specific cells. The results also suggest that altered RAI1 abundance could contribute to disease features in disorders caused by TCF20 dosage imbalance.

Smith-Magenis syndrome protein RAI1 regulates body weight homeostasis through hypothalamic BDNF-producing neurons and neurotrophin downstream signalling

Retinoic acid-induced 1 (RAI1) haploinsufficiency causes Smith-Magenis syndrome (SMS), a genetic disorder with symptoms including hyperphagia, hyperlipidemia, severe obesity, and autism phenotypes. RAI1 is a transcriptional regulator with a pan-neural expression pattern and hundreds of downstream targets. The mechanisms linking neural Rai1 to body weight regulation remain unclear. Here we find that hypothalamic brain-derived neurotrophic factor (BDNF) and its downstream signalling are disrupted in SMS (Rai1+/-) mice. Selective Rai1 loss from all BDNF-producing cells or from BDNF-producing neurons in the paraventricular nucleus of the hypothalamus (PVH) induced obesity in mice. Electrophysiological recordings revealed that Rai1 ablation decreased the intrinsic excitability of PVHBDNF neurons. Chronic treatment of SMS mice with LM22A-4 engages neurotrophin downstream signalling and delayed obesity onset. This treatment also partially rescued disrupted lipid profiles, insulin intolerance, and stereotypical repetitive behaviour in SMS mice. These data argue that RAI1 regulates body weight and metabolic function through hypothalamic BDNF-producing neurons and that targeting neurotrophin downstream signalling might improve associated SMS phenotypes.

Revisiting the expression of BDNF and its receptors in mammalian development

Brain-derived neurotrophic factor (BDNF) promotes the survival and functioning of neurons in the central nervous system and contributes to proper functioning of many non-neural tissues. Although the regulation and role of BDNF have been extensively studied, a rigorous analysis of the expression dynamics of BDNF and its receptors TrkB and p75NTR is lacking. Here, we have analyzed more than 3,600 samples from 18 published RNA sequencing datasets, and used over 17,000 samples from GTEx, and ~ 180 samples from BrainSpan database, to describe the expression of BDNF in the developing mammalian neural and non-neural tissues. We show evolutionarily conserved dynamics and expression patterns of BDNF mRNA and non-conserved alternative 5' exon usage. Finally, we also show increasing BDNF protein levels during murine brain development and BDNF protein expression in several non-neural tissues. In parallel, we describe the spatiotemporal expression pattern of BDNF receptors TrkB and p75NTR in both murines and humans. Collectively, our in-depth analysis of the expression of BDNF and its receptors gives insight into the regulation and signaling of BDNF in the whole organism throughout life.

Possible involvement of silent mutations in cancer pathogenesis and evolution

Recent studies have shown that some silent mutations can be harmful to various processes. In this study, we performed a comprehensive in silico analysis to elucidate the effects of silent mutations on cancer pathogenesis using exome sequencing data derived from the Cancer Genome Atlas. We focused on the codon optimality scores of silent mutations, which were defined as the difference between the optimality of synonymous codons, calculated using the codon usage table. The relationship between cancer evolution and silent mutations showed that the codon optimality score of the mutations that occurred later in carcinogenesis was significantly higher than of those that occurred earlier. In addition, mutations with higher scores were enriched in genes involved in the cell cycle and cell division, while those with lower scores were enriched in genes involved in apoptosis and cellular senescence. Our results demonstrate that some silent mutations can be involved in cancer pathogenesis.

Differential Regulation of the BDNF Gene in Cortical and Hippocampal Neurons

Brain-derived neurotrophic factor (BDNF) is a widely expressed neurotrophin that supports the survival, differentiation, and signaling of various neuronal populations. Although it has been well described that expression of BDNF is strongly regulated by neuronal activity, little is known whether regulation of BDNF expression is similar in different brain regions. Here, we focused on this fundamental question using neuronal populations obtained from rat cerebral cortices and hippocampi of both sexes. First, we thoroughly characterized the role of the best-described regulators of BDNF gene - cAMP response element binding protein (CREB) family transcription factors, and show that activity-dependent BDNF expression depends more on CREB and the coactivators CREB binding protein (CBP) and CREB-regulated transcriptional coactivator 1 (CRTC1) in cortical than in hippocampal neurons. Our data also reveal an important role of CREB in the early induction of BDNF mRNA expression after neuronal activity and only modest contribution after prolonged neuronal activity. We further corroborated our findings at BDNF protein level. To determine the transcription factors regulating BDNF expression in these rat brain regions in addition to CREB family, we used in vitro DNA pulldown assay coupled with mass spectrometry, chromatin immunoprecipitation (ChIP), and bioinformatics, and propose a number of neurodevelopmentally important transcription factors, such as FOXP1, SATB2, RAI1, BCL11A, and TCF4 as brain region-specific regulators of BDNF expression. Together, our data reveal complicated brain region-specific fine-tuning of BDNF expression.SIGNIFICANCE STATEMENT To date, majority of the research has focused on the regulation of brain-derived neurotrophic factor (BDNF) in the brain but much less is known whether the regulation of BDNF expression is universal in different brain regions and neuronal populations. Here, we report that the best described regulators of BDNF gene from the cAMP-response element binding protein (CREB) transcription factor family have a more profound role in the activity-dependent regulation of BDNF in cortex than in hippocampus. Our results indicate a brain region-specific fine tuning of BDNF expression. Moreover, we have used unbiased determination of novel regulators of the BDNF gene and report a number of neurodevelopmentally important transcription factors as novel potential regulators of the BDNF expression.

Retinoic acid-induced 1 gene haploinsufficiency alters lipid metabolism and causes autophagy defects in Smith-Magenis syndrome

Smith-Magenis syndrome (SMS) is a neurodevelopmental disorder characterized by cognitive and behavioral symptoms, obesity, and sleep disturbance, and no therapy has been developed to alleviate its symptoms or delay disease onset. SMS occurs due to haploinsufficiency of the retinoic acid-induced-1 (RAI1) gene caused by either chromosomal deletion (SMS-del) or RAI1 missense/nonsense mutation. The molecular mechanisms underlying SMS are unknown. Here, we generated and characterized primary cells derived from four SMS patients (two with SMS-del and two carrying RAI1 point mutations) and four control subjects to investigate the pathogenetic processes underlying SMS. By combining transcriptomic and lipidomic analyses, we found altered expression of lipid and lysosomal genes, deregulation of lipid metabolism, accumulation of lipid droplets, and blocked autophagic flux. We also found that SMS cells exhibited increased cell death associated with the mitochondrial pathology and the production of reactive oxygen species. Treatment with N-acetylcysteine reduced cell death and lipid accumulation, which suggests a causative link between metabolic dyshomeostasis and cell viability. Our results highlight the pathological processes in human SMS cells involving lipid metabolism, autophagy defects and mitochondrial dysfunction and suggest new potential therapeutic targets for patient treatment.

rAAV-CRISPRa therapy corrects Rai1 haploinsufficiency and rescues selective disease features in Smith-Magenis syndrome mice

Haploinsufficiency in retinoic acid induced 1 (RAI1) causes Smith-Magenis syndrome (SMS), a severe neurodevelopmental disorder characterized by neurocognitive deficits and obesity. Currently, curative treatments for SMS do not exist. Here, we take a recombinant adeno-associated virus (rAAV)-clustered regularly interspaced short palindromic repeats activation (CRISPRa) approach to increase expression of the remaining intact Rai1 allele. Building upon our previous work that found the paraventricular nucleus of hypothalamus plays a central role in SMS pathogenesis, we performed paraventricular nucleus of hypothalamus-specific rAAV-CRISPRa therapy by increasing endogenous Rai1 expression in SMS (Rai1^±) mice. We found that rAAV-CRISPRa therapy rescues excessive repetitive behavior, delays the onset of obesity, and partially reduces hyperphagia in SMS mice. Our work provides evidence that rAAV-CRISPRa therapy during early adolescence can boost the expression of healthy Rai1 allele and modify disease progression in a mouse model of Smith-Magenis syndrome.

A unique Smith-Magenis patient with a de novo intragenic deletion on the maternally inherited overexpressed RAI1 allele

RAI1 is a dosage-sensitive gene whose decreased or increased expression by recurrent and non-recurrent 17p11.2 deletions or duplications causes Smith-Magenis (SMS) or Potocki-Lupski syndromes (PTLS), respectively. Here we report on a 21-year-old female patient showing SMS phenotype who was found to carry a 3.4 kb de novo intragenic RAI1 deletion. Interestingly, a significant increase in RAI1 transcript levels was identified in the patient's, brother's and mother's peripheral blood cells. Allele-specific dosage analysis revealed that the patient's maternally inherited overexpressed RAI1 allele harbors the intragenic deletion, confirming the SMS diagnosis due to the presence of a single wild-type RAI1 functional allele. The mother and brother do not present any PTLS neurologic/behavioral clinical features. Extensive sequencing of RAI1 promoter and predicted regulatory regions showed no potential causative variants accounting for gene overexpression. However, the mother and both children share a novel private missense variant in RAI1 exon 3, currently classified as a VUS (uncertain significance), though predicted by two bioinformatic tools to disrupt the binding site of one specific transcription factor. The reported familial case, the second showing RAI1 overexpression in the absence of RAI1 duplication, may help to understand the regulation of RAI1 dosage sensitivity although its phenotypic effect remains to be determined.

Loss of Rai1 enhances hippocampal excitability and epileptogenesis in mouse models of Smith-Magenis syndrome

Smith–Magenis syndrome (SMS) is a neurodevelopmental disorder associated with autism and epileptic seizures. SMS is caused by losing one copy of the gene encoding retinoic acid induced 1 (RAI1), a ubiquitously expressed transcriptional regulator. To pinpoint brain regions and cell types contributing to neuronal hyperexcitability in SMS, we combined electrophysiology and three-dimensional imaging of Fos expression in the intact mouse brain. We found that Rai1-deficient hippocampal dentate gyrus granule cells (dGCs) show increased intrinsic excitability and enhanced glutamatergic synaptic transmission. Our findings indicate that Rai1 safeguards the hippocampal network from hyperexcitability and could help explain abnormal brain activity in SMS.

Hyperexcitability of brain circuits is a common feature of autism spectrum disorders (ASDs). Genetic deletion of a chromatin-binding protein, retinoic acid induced 1 (RAI1), causes Smith–Magenis syndrome (SMS). SMS is a syndromic ASD associated with intellectual disability, autistic features, maladaptive behaviors, overt seizures, and abnormal electroencephalogram (EEG) patterns. The molecular and neural mechanisms underlying abnormal brain activity in SMS remain unclear. Here we show that panneural Rai1 deletions in mice result in increased seizure susceptibility and prolonged hippocampal seizure duration in vivo and increased dentate gyrus population spikes ex vivo. Brain-wide mapping of neuronal activity pinpointed selective cell types within the limbic system, including the hippocampal dentate gyrus granule cells (dGCs) that are hyperactivated by chemoconvulsant administration or sensory experience in Rai1-deficient brains. Deletion of Rai1 from glutamatergic neurons, but not from gamma-aminobutyric acidergic (GABAergic) neurons, was responsible for increased seizure susceptibility. Deleting Rai1 from the Emx1^Cre-lineage glutamatergic neurons resulted in abnormal dGC properties, including increased excitatory synaptic transmission and increased intrinsic excitability. Our work uncovers the mechanism of neuronal hyperexcitability in SMS by identifying Rai1 as a negative regulator of dGC intrinsic and synaptic excitability.

Relationships between food-related behaviors, obesity, and medication use in individuals with Smith-Magenis syndrome

BACKGROUND

Smith-Magenis syndrome (SMS) is a complex neurodevelopmental disorder that includes obesity and food-seeking/satiety-related behaviors.

AIMS

This study examined associations between food-related/hyperphagic behaviors, weight, and medication use in individuals with SMS.

METHODS/PROCEDURES

Caregivers of individuals with SMS in the Parents and Researchers Interested in SMS (PRISMS) Patient Registry completed a demographic/medication questionnaire, the Hyperphagia Questionnaire for Clinical Trials, and the Food Related Problems Questionnaire.

OUTCOMES/RESULTS

Among 49 participants (M_age = 16.41 ± 12.73 years, range = 4-69 years, 55% girls/women), individuals with SMS with overweight/obesity (n = 22) had worse overall food-related problems including greater impaired satiety (p < 0.05), maladaptive eating behaviors (p < 0.05), inappropriate response (p < 0.01), and hyperphagia (p < 0.01) compared to individuals of normal/underweight (n = 27). Those taking anti-depressants/anxiolytics (n = 16) had greater maladaptive eating behaviors (p < 0.05), hyperphagic behaviors (p < 0.05), and hyperphagic severity (p < 0.05) than those not taking anti-depressants/anxiolytics (n = 33). Boys/men with SMS had greater maladaptive eating behaviors (p < 0.05), inappropriate response (p < 0.05), and hyperphagic drive (p < 0.01) than girls/women with SMS.

CONCLUSIONS/IMPLICATIONS

Maladaptive food-related behaviors were higher in individuals with SMS with overweight/obesity, taking anti-depressants/anxiolytics, or who were male. Medications in this population should be chosen with weight-related side effects in mind.

Smith-Magenis Syndrome—Clinical Review, Biological Background and Related Disorders

Smith-Magenis syndrome (SMS) is a complex genetic disorder characterized by distinctive physical features, developmental delay, cognitive impairment, and a typical behavioral phenotype. SMS is caused by interstitial 17p11.2 deletions (90%), encompassing multiple genes and including the retinoic acid-induced 1 gene (RAI1), or by pathogenic variants in RAI1 itself (10%). RAI1 is a dosage-sensitive gene expressed in many tissues and acting as transcriptional regulator. The majority of individuals exhibit a mild-to-moderate range of intellectual disability. The behavioral phenotype includes significant sleep disturbance, stereotypes, maladaptive and self-injurious behaviors. In this review, we summarize current clinical knowledge and therapeutic approaches. We further discuss the common biological background shared with other conditions commonly retained in differential diagnosis.

Disruption of MeCP2-TCF20 complex underlies distinct neurodevelopmental disorders

MeCP2 is associated with Rett syndrome (RTT), MECP2 duplication syndrome, and a number of conditions with isolated features of these diseases, including autism, intellectual disability, and motor dysfunction. MeCP2 is known to broadly bind methylated DNA, but the precise molecular mechanism driving disease pathogenesis remains to be determined. Using proximity-dependent biotinylation (BioID), we identified a transcription factor 20 (TCF20) complex that interacts with MeCP2 at the chromatin interface. Importantly, RTT-causing mutations in MECP2 disrupt this interaction. TCF20 and MeCP2 are highly coexpressed in neurons and coregulate the expression of key neuronal genes. Reducing Tcf20 partially rescued the behavioral deficits caused by MECP2 overexpression, demonstrating a functional relationship between MeCP2 and TCF20 in MECP2 duplication syndrome pathogenesis. We identified a patient exhibiting RTT-like neurological features with a missense mutation in the PHF14 subunit of the TCF20 complex that abolishes the MeCP2-PHF14-TCF20 interaction. Our data demonstrate the critical role of the MeCP2-TCF20 complex for brain function.

Angelman Syndrome and Angelman-like Syndromes Share the Same Calcium-Related Gene Signatures

Angelman-like syndromes are a group of neurodevelopmental disorders that entail clinical presentation similar to Angelman Syndrome (AS). In our previous study, we showed that calcium signaling is disrupted in AS, and we identified calcium-target and calcium-regulating gene signatures that are able to differentiate between AS and their controls in different models. In the herein study, we evaluated these sets of calcium-target and calcium-regulating genes as signatures of AS-like and non-AS-like syndromes. We collected a number of RNA-seq datasets of various AS-like and non-AS-like syndromes and performed Principle Component Analysis (PCA) separately on the two sets of signature genes to visualize the distribution of samples on the PC1-PC2 plane. In addition to the evaluation of calcium signature genes, we performed differential gene expression analyses to identify calcium-related genes dysregulated in each of the studied syndromes. These analyses showed that the calcium-target and calcium-regulating signatures differentiate well between AS-like syndromes and their controls. However, in spite of the fact that many of the non-AS-like syndromes have multiple differentially expressed calcium-related genes, the calcium signatures were not efficient classifiers for non-AS-like neurodevelopmental disorders. These results show that features based on clinical presentation are reflected in signatures derived from bioinformatics analyses and suggest the use of bioinformatics as a tool for classification.

Temporal dissection of Rai1 function reveals brain-derived neurotrophic factor as a potential therapeutic target for Smith-Magenis syndrome

Haploinsufficiency of RAI1 is responsible for Smith-Magenis Syndrome (SMS), a childhood neurodevelopmental disorder associated with hyperphagia, obesity, and autistic features. We previously showed that constitutive inactivation of one or both copies of Rai1 in the germline or developing brain induces SMS-like neurobehavioral deficits and obesity in mice. By contrast, the postnatal function of Rai1 is unclear. Here, we globally deleted one or both copies of Rai1 during two postnatal developmental windows by generating an inducible Rai1 knockout mouse model. We found that delayed Rai1 deletion at 3 or 8 weeks of age had no effect on neurobehavioral functions but resulted in adult-onset obesity and decreased expression of brain-derived neurotrophic factor (Bdnf) in the hypothalamus. Remarkably, genetic overexpression of human Bdnf in Rai1 heterozygous mice reversed SMS-like obesity, hyperphagia, metabolic syndrome-like features, and hyposociability. Increasing Bdnf signaling in the paraventricular nucleus of the hypothalamus (PVH) or the ventromedial nucleus of the hypothalamus (VMH) was sufficient to mediate the anti-obesity effect. Our work identifies the function of Rai1 in different temporal windows after birth and provides in vivo evidence that increasing Bdnf signaling is therapeutically effective in a preclinical mouse model of SMS.

RAI1 Regulates Activity-Dependent Nascent Transcription and Synaptic Scaling

Long-lasting forms of synaptic plasticity such as synaptic scaling are critically dependent on transcription. Activity-dependent transcriptional dynamics in neurons, however, remain incompletely characterized because most previous efforts relied on measurement of steady-state mRNAs. Here, we use nascent RNA sequencing to profile transcriptional dynamics of primary neuron cultures undergoing network activity shifts. We find pervasive transcriptional changes, in which ∼45% of expressed genes respond to network activity shifts. We further link retinoic acid-induced 1 (RAI1), the Smith-Magenis syndrome gene, to the transcriptional program driven by reduced network activity. Remarkable agreement among nascent transcriptomes, dynamic chromatin occupancy of RAI1, and electrophysiological properties of Rai1-deficient neurons demonstrates the essential roles of RAI1 in suppressing synaptic upscaling in the naive network, while promoting upscaling triggered by activity silencing. These results highlight the utility of bona fide transcription profiling to discover mechanisms of activity-dependent chromatin remodeling that underlie normal and pathological synaptic plasticity.

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BrU-seq reveals nascent transcription during synaptic up- or downscaling

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Smith-Magenis syndrome protein RAI1 regulates upscaling-associated transcription

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RAI1 departs chromatin in response to network activity shifts

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RAI1 blocks upscaling in naive networks and promotes inactivity-induced upscaling

Autism Spectrum Disorder: Signaling Pathways and Prospective Therapeutic Targets

The Autism Spectrum Disorder (ASD) consists of a prevalent and heterogeneous group of neurodevelopmental diseases representing a severe burden to affected individuals and their caretakers. Despite substantial improvement towards understanding of ASD etiology and pathogenesis, as well as increased social awareness and more intensive research, no effective drugs have been successfully developed to resolve the main and most cumbersome ASD symptoms. Hence, finding better treatments, which may act as "disease-modifying" agents, and novel biomarkers for earlier ASD diagnosis and disease stage determination are needed. Diverse mutations of core components and consequent malfunctions of several cell signaling pathways have already been found in ASD by a series of experimental platforms, including genetic associations analyses and studies utilizing pre-clinical animal models and patient samples. These signaling cascades govern a broad range of neurological features such as neuronal development, neurotransmission, metabolism, and homeostasis, as well as immune regulation and inflammation. Here, we review the current knowledge on signaling pathways which are commonly disrupted in ASD and autism-related conditions. As such, we further propose ways to translate these findings into the development of genetic and biochemical clinical tests for early autism detection. Moreover, we highlight some putative druggable targets along these pathways, which, upon further research efforts, may evolve into novel therapeutic interventions for certain ASD conditions. Lastly, we also refer to the crosstalk among these major signaling cascades as well as their putative implications in therapeutics. Based on this collective information, we believe that a timely and accurate modulation of these prominent pathways may shape the neurodevelopment and neuro-immune regulation of homeostatic patterns and, hopefully, rescue some (if not all) ASD phenotypes.

Smith-Magenis syndrome: Report of morphological and new functional cardiac findings with review of the literature

Smith-Magenis syndrome (SMS) is a genetic disorder characterized by multiple congenital anomalies, sleep disturbance, behavioral impairment, and intellectual disability. Its genetic cause has been defined as an alteration in the Retinoic Acid-Induced 1 gene. Cardiac anomalies have been reported since the first description of this condition in patients with 17p11.2 deletion. Variable cardiac defects, including ventricular septal defects, atrial septal defects, tricuspid stenosis, mitral stenosis, tricuspid and mitral regurgitation, aortic stenosis, pulmonary stenosis, mitral valve prolapse, tetralogy of Fallot, and total anomalous pulmonary venous connection, have been anecdotally reported and systematic case series are still lacking. Herein, we define the spectrum of the cardiac phenotype and describe for the first time the cardiac function in a large cohort of pediatric patients with SMS. Revision of the literature and correlations between genotype and cardiac phenotype was performed.

Dissecting the complexity of CNV pathogenicity: insights from Drosophila and zebrafish models

Genetic architecture predisposes regions of the human genome to copy-number variants, which confer substantial disease risk, most prominently towards neurodevelopmental disorders. These variants typically contain multiple genes and are often associated with extensive pleiotropy and variable phenotypic expressivity. Despite the expansion of the fidelity of CNV detection, and the study of such lesions at the population level, understanding causal mechanisms for CNV phenotypes will require biological testing of constituent genes and their interactions. In this regard, model systems amenable to high-throughput phenotypic analysis of dosage-sensitive genes (and combinations thereof) are beginning to offer improved granularity of CNV-driven pathology. Here, we review the utility of Drosophila and zebrafish models for pathogenic CNV regions, highlight the advances made in discovery of single gene drivers and genetic interactions that determine specific CNV phenotypes, and argue for their validity in dissecting conserved developmental mechanisms associated with CNVs.

Network and Evolutionary Analysis of Human Epigenetic Regulators to Unravel Disease Associations

We carried out a system-level analysis of epigenetic regulators (ERs) and detailed the protein–protein interaction (PPI) network characteristics of disease-associated ERs. We found that most diseases associated with ERs can be clustered into two large groups, cancer diseases and developmental diseases. ER genes formed a highly interconnected PPI subnetwork, indicating a high tendency to interact and agglomerate with one another. We used the disease module detection (DIAMOnD) algorithm to expand the PPI subnetworks into a comprehensive cancer disease ER network (CDEN) and developmental disease ER network (DDEN). Using the transcriptome from early mouse developmental stages, we identified the gene co-expression modules significantly enriched for the CDEN and DDEN gene sets, which indicated the stage-dependent roles of ER-related disease genes during early embryonic development. The evolutionary rate and phylogenetic age distribution analysis indicated that the evolution of CDEN and DDEN genes was mostly constrained, and these genes exhibited older evolutionary age. Our analysis of human polymorphism data revealed that genes belonging to DDEN and Seed-DDEN were more likely to show signs of recent positive selection in human history. This finding suggests a potential association between positive selection of ERs and risk of developmental diseases through the mechanism of antagonistic pleiotropy.

Dosage-sensitive genes in autism spectrum disorders: From neurobiology to therapy

Autism spectrum disorders (ASDs) are a group of heterogenous neurodevelopmental disorders affecting 1 in 59 children. Syndromic ASDs are commonly associated with chromosomal rearrangements or dosage imbalance involving a single gene. Many of these genes are dosage-sensitive and regulate transcription, protein homeostasis, and synaptic function in the brain. Despite vastly different molecular perturbations, syndromic ASDs share core symptoms including social dysfunction and repetitive behavior. However, each ASD subtype has a unique pathogenic mechanism and combination of comorbidities that require individual attention. We have learned a great deal about how these dosage-sensitive genes control brain development and behaviors from genetically-engineered mice. Here we describe the clinical features of eight monogenic neurodevelopmental disorders caused by dosage imbalance of four genes, as well as recent advances in using genetic mouse models to understand their pathogenic mechanisms and develop intervention strategies. We propose that applying newly developed quantitative molecular and neuroscience technologies will advance our understanding of the unique neurobiology of each disorder and enable the development of personalized therapy.

Optimizing Nervous System-Specific Gene Targeting with Cre Driver Lines: Prevalence of Germline Recombination and Influencing Factors

The Cre-loxP system is invaluable for spatial and temporal control of gene knockout, knockin, and reporter expression in the mouse nervous system. However, we report varying probabilities of unexpected germline recombination in distinct Cre driver lines designed for nervous system-specific recombination. Selective maternal or paternal germline recombination is showcased with sample Cre lines. Collated data reveal germline recombination in over half of 64 commonly used Cre driver lines, in most cases with a parental sex bias related to Cre expression in sperm or oocytes. Slight differences among Cre driver lines utilizing common transcriptional control elements affect germline recombination rates. Specific target loci demonstrated differential recombination; thus, reporters are not reliable proxies for another locus of interest. Similar principles apply to other recombinase systems and other genetically targeted organisms. We hereby draw attention to the prevalence of germline recombination and provide guidelines to inform future research for the neuroscience and broader molecular genetics communities.

Sleep as a translationally-relevant endpoint in studies of autism spectrum disorder (ASD)

Sleep has numerous advantages for aligning clinical and preclinical (basic neuroscience) studies of neuropsychiatric illness. Sleep has high translational relevance, because the same endpoints can be studied in humans and laboratory animals. In addition, sleep experiments are conducive to continuous data collection over long periods (hours/days/weeks) and can be based on highly objective neurophysiological measures. Here, we provide a translationally-oriented review on what is currently known about sleep in the context of autism spectrum disorder (ASD), including ASD-related conditions, thought to have genetic, environmental, or mixed etiologies. In humans, ASD is frequently associated with comorbid medical conditions including sleep disorders. Animal models used in the study of ASD frequently recapitulate dysregulation of sleep and biological (diurnal, circadian) rhythms, suggesting common pathophysiologies across species. As our understanding of the neurobiology of ASD and sleep each become more refined, it is conceivable that sleep-derived metrics may offer more powerful biomarkers of altered neurophysiology in ASD than the behavioral tests currently used in humans or lab animals. As such, the study of sleep in animal models for ASD may enable fundamentally new insights on the condition and represent a basis for strategies that enable the development of more effective therapeutics.

Apical-Basal Polarity Signaling Components, Lgl1 and aPKCs, Control Glutamatergic Synapse Number and Function

Normal synapse formation is fundamental to brain function. We show here that an apical-basal polarity (A-BP) protein, Lgl1, is present in the postsynaptic density and negatively regulates glutamatergic synapse numbers by antagonizing the atypical protein kinase Cs (aPKCs). A planar cell polarity protein, Vangl2, which inhibits synapse formation, was decreased in synaptosome fractions of cultured cortical neurons from Lgl1 knockout embryos. Conditional knockout of Lgl1 in pyramidal neurons led to reduction of AMPA/NMDA ratio and impaired plasticity. Lgl1 is frequently deleted in Smith-Magenis syndrome (SMS). Lgl1 conditional knockout led to increased locomotion, impaired novel object recognition and social interaction. Lgl1+/- animals also showed increased synapse numbers, defects in open field and social interaction, as well as stereotyped repetitive behavior. Social interaction in Lgl1+/- could be rescued by NMDA antagonists. Our findings reveal a role of apical-basal polarity proteins in glutamatergic synapse development and function and also suggest a potential treatment for SMS patients with Lgl1 deletion.

Parental experiences with behavioural problems in Smith-Magenis syndrome: The need for syndrome-specific competence

The experience of having a rare disorder was summarised in a large study as 'falling outside the vast field of knowledge of the professionals'. Parents (31 mothers and 17 fathers) of 32 persons with Smith-Magenis syndrome (SMS) participated in this study. A phenomenological approach was used to analyse the data into topics and themes. Four themes emerged: behavioural challenges displayed, parents' strategies for meeting the challenging behaviours, parents' experiences of their own competence and parents' experiences of professionals' competence and understanding regarding children with SMS and their behaviour challenges. We found that parents of children with SMS experience that they are exposed to severe challenging behaviours from their child. The parents believe that they experience more misunderstandings with professionals and that the challenging behaviours increase because there are some specific characteristics of SMS that professionals are not aware of or do not consider in their support services.

Smith-Magenis Syndrome: Molecular Basis of a Genetic-Driven Melatonin Circadian Secretion Disorder

Smith-Magenis syndrome (SMS), linked to Retinoic Acid Induced (RAI1) haploinsufficiency, is a unique model of the inversion of circadian melatonin secretion. In this regard, this model is a formidable approach to better understand circadian melatonin secretion cycle disorders and the role of the RAI1 gene in this cycle. Sleep-wake cycle disorders in SMS include sleep maintenance disorders with a phase advance and intense sleepiness around noon. These disorders have been linked to a general disturbance of sleep-wake rhythm and coexist with inverted secretion of melatonin. The exact mechanism underlying the inversion of circadian melatonin secretion in SMS has rarely been discussed. We suggest three hypotheses that could account for the inversion of circadian melatonin secretion and discuss them. First, inversion of the circadian melatonin secretion rhythm could be linked to alterations in light signal transduction. Second, this inversion could imply global misalignment of the circadian system. Third, the inversion is not linked to a global circadian clock shift but rather to a specific impairment in the melatonin secretion pathway between the suprachiasmatic nuclei (SCN) and pinealocytes. The development of diurnal SMS animal models that produce melatonin appears to be an indispensable step to further understand the molecular basis of the circadian melatonin secretion rhythm.

Tyrosine aminotransferase is involved in the oxidative stress response by metabolizing meta-tyrosine in Caenorhabditis elegans

Under oxidative stress conditions, hydroxyl radicals can oxidize the phenyl ring of phenylalanine, producing the abnormal tyrosine isomer meta-tyrosine (m-tyrosine). m-Tyrosine levels are commonly used as a biomarker of oxidative stress, and its accumulation has recently been reported to adversely affect cells, suggesting a direct role for m-tyrosine in oxidative stress effects. We found that the Caenorhabditis elegans ortholog of tyrosine aminotransferase (TATN-1)-the first enzyme involved in the metabolic degradation of tyrosine-is up-regulated in response to oxidative stress and directly activated by the oxidative stress-responsive transcription factor SKN-1. Worms deficient in tyrosine aminotransferase activity displayed increased sensitivity to multiple sources of oxidative stress. Biochemical assays revealed that m-tyrosine is a substrate for TATN-1-mediated deamination, suggesting that TATN-1 also metabolizes m-tyrosine. Consistent with a toxic effect of m-tyrosine and a protective function of TATN-1, tatn-1 mutant worms exhibited delayed development, marked reduction in fertility, and shortened lifespan when exposed to m-tyrosine. A forward genetic screen identified a mutation in the previously uncharacterized gene F01D4.5-homologous with human transcription factor 20 (TCF20) and retinoic acid-induced 1 (RAI1)-that suppresses the adverse phenotypes observed in m-tyrosine-treated tatn-1 mutant worms. RNA-Seq analysis of F01D4.5 mutant worms disclosed a significant reduction in the expression of specific isoforms of genes encoding ribosomal proteins, suggesting that alterations in protein synthesis or ribosome structure could diminish the adverse effects of m-tyrosine. Our findings uncover a critical role for tyrosine aminotransferase in the oxidative stress response via m-tyrosine metabolism.

Preclinical Testing in Translational Animal Models of Prader-Willi Syndrome: Overview and Gap Analysis

Prader-Willi syndrome (PWS) is a rare neurodevelopmental disorder causing endocrine, musculoskeletal, and neurological dysfunction. PWS is caused by the inactivation of contiguous genes, complicating the development of targeted therapeutics. Clinical trials are now underway in PWS, with more trials to be implemented in the next few years. PWS-like endophenotypes are recapitulated in gene-targeted mice in which the function of one or more PWS genes is disrupted. These animal models can guide priorities for clinical trials or provide information about efficacy of a compound within the context of the specific disease. We now review the current status of preclinical studies that measure the effect of therapeutics on PWS-like endophenotypes. Seven categories of therapeutics (oxytocin and related compounds, K⁺-ATP channel agonists, melanocortin 4 receptor agonists, incretin mimetics and/or GLP-1 receptor agonists, cannabinoids, ghrelin agents, and Caralluma fimbriata [cactus] extract) have been tested for their effect on endophenotypes in both PWS animal models and clinical trials. Many other therapeutics have been tested in clinical trials, but not preclinical models of PWS or vice versa. Fostering dialogs among investigators performing preclinical validation of animal models and those implementing clinical studies will accelerate the discovery and translation of therapies into clinical practice in PWS.

Behavior and sleep disturbance in Smith-Magenis syndrome

PURPOSE OF REVIEW

To provide an update of the most recent studies on Smith-Magenis syndrome (SMS) with a focus on the unique pattern of behavioral and sleep disturbances associated with the condition.

RECENT FINDINGS

The recent literature on SMS has focused on the characteristic severe behavioral and sleep disturbances. A better understanding of the underlying pathophysiological mechanisms and common clinical course has helped further characterize SMS, while much is left to be discovered in regard to effective treatment/management.

SUMMARY

SMS is a difficult to manage genetic condition defined by pervasive and progressive behavioral and sleep disturbances with a unique pattern that can often be easily discerned from other neurodevelopmental disorders. Common behavioral features include maladaptive/self-injurious, aggressive, stereotypic, and the newly appreciated food seeking behaviors associated with SMS. In addition, there is a sleep disturbance defined by an altered circadian rhythm with frequent nighttime waking and daytime sleepiness, causing patients and families significant distress. Small studies have suggested some treatment/management approaches to the behavioral and sleep disturbances, however, much remains to be discovered.

Early adolescent Rai1 reactivation reverses transcriptional and social interaction deficits in a mouse model of Smith-Magenis syndrome

Losing one copy of the RAI1 gene causes Smith–Magenis syndrome (SMS), a neurodevelopmental disorder. Using a newly generated SMS mouse model, this study demonstrates that restoring the Rai1 gene dose in an early postnatal window could repair gene expression and social interaction deficits in this SMS model. The SMS mouse model also showed a reduced density of dendritic spines, anatomical correlates of excitatory synapses, in the prefrontal cortex. Artificial activation of prefrontal cortex neurons partially alleviated the behavioral deficits. These findings suggest that, similar to Rett syndrome, SMS is caused by disruption of a chromatin-modifying gene with reversible developmental phenotypes, highlighting the potential treatment windows in childhood or adolescence.

Haploinsufficiency of Retinoic Acid Induced 1 (RAI1) causes Smith–Magenis syndrome (SMS), a syndromic autism spectrum disorder associated with craniofacial abnormalities, intellectual disability, and behavioral problems. There is currently no cure for SMS. Here, we generated a genetic mouse model to determine the reversibility of SMS-like neurobehavioral phenotypes in Rai1 heterozygous mice. We show that normalizing the Rai1 level 3–4 wk after birth corrected the expression of genes related to neural developmental pathways and fully reversed a social interaction deficit caused by Rai1 haploinsufficiency. In contrast, Rai1 reactivation 7–8 wk after birth was not beneficial. We also demonstrated that the correct Rai1 dose is required in both excitatory and inhibitory neurons for proper social interactions. Finally, we found that Rai1 heterozygous mice exhibited a reduction of dendritic spines in the medial prefrontal cortex (mPFC) and that optogenetic activation of mPFC neurons in adults improved the social interaction deficit of Rai1 heterozygous mice. Together, these results suggest the existence of a postnatal temporal window during which restoring Rai1 can improve the transcriptional and social behavioral deficits in a mouse model of SMS. It is possible that circuit-level interventions would be beneficial beyond this critical window.

A Rare De Novo RAI1 Gene Mutation Affecting BDNF-Enhancer-Driven Transcription Activity Associated with Autism and Atypical Smith-Magenis Syndrome Presentation

Deletions and mutations involving the Retinoic Acid Induced 1 (RAI1) gene at 17p11.2 cause Smith-Magenis syndrome (SMS). Here we report a patient with autism as the main clinical presentation, with some SMS-like features and a rare de novo RAI1 gene mutation, c.3440G > A (p.R1147Q). We functionally characterized the RAI1 p.R1147Q mutant protein. The mutation, located near the nuclear localization signal, had no effect on the subcellular localization of the mutant protein. However, similar to previously reported RAI1 missense mutations in SMS patients, the RAI1 p.R1147Q mutant protein showed a significant deficiency in activating in vivo transcription of a reporter gene driven by a BDNF (brain-derived neurotrophic factor) intronic enhancer. In addition, expression of other genes associated with neurobehavioral abnormalities and/or neurodevelopmental disorders were found to be altered in this patient. These results suggest a likely contribution of RAI1, either alone or in combination of other factors, to social behavior and reinforce the RAI1 gene as a candidate gene in patients with autistic manifestations or social behavioral abnormalities.

Reversed gender ratio of autism spectrum disorder in Smith-Magenis syndrome

Background

A substantial amount of research shows a higher rate of autistic type of problems in males compared to females. The 4:1 male to female ratio is one of the most consistent findings in autism spectrum disorder (ASD).

Lately, the interest in studying ASD in genetic disorders has increased, and research has shown a higher prevalence of ASD in some genetic disorders than in the general population.

Smith-Magenis syndrome (SMS) is a rare and complex genetic syndrome caused by an interstitial deletion of chromosome 17p11.2 or a mutation on the retinoic acid induced 1 gene. The disorder is characterised by intellectual disability, multiple congenital anomalies, obesity, neurobehavioural abnormalities and a disrupted circadian sleep-wake pattern.

Methods

Parents of 28 persons with SMS between 5 and 50 years old participated in this study. A total of 12 of the persons with SMS were above the age of 18 at the time of the study. A total of 11 came from Sweden and 17 were from Norway.

We collected information regarding the number of autism spectrum symptoms using the Social Communication Questionnaire (SCQ) and the Social Responsiveness Scale (SRS). Adaptive behaviour was also measured using the Vineland Adaptive Behavior Scale II. The level of intellectual disability was derived from a review of the medical chart.

Results

We found significant gender differences in ASD symptomatology using the SCQ and SRS questionnaires. We found approximately three females per male above the SCQ cutoff. The same differences were not found in the intellectual level and adaptive behaviour or for behavioural and emotional problems.

Gender had an independent contribution in a regression model predicting the total SCQ score, and neither the Vineland Adaptive Behavior Scale II nor the Developmental Behaviour Checklist had an independent contribution to the SCQ scores.

Conclusion

We found a clear reversed gender difference in ASD symptomatology in persons with SMS. This may be relevant in the search for female protective factors assumed to explain the male bias in ASD.

Antipurinergic therapy for autism-An in-depth review

Are the symptoms of autism caused by a treatable metabolic syndrome that traces to the abnormal persistence of a normal, alternative functional state of mitochondria? A small clinical trial published in 2017 suggests this is possible. Based on a new unifying theory of pathogenesis for autism called the cell danger response (CDR) hypothesis, this study of 10 boys, ages 5-14years, showed that all 5 boys who received antipurinergic therapy (APT) with a single intravenous dose of suramin experienced improvements in all the core symptoms of autism that lasted for 5-8weeks. Language, social interaction, restricted interests, and repetitive movements all improved. Two children who were non-verbal spoke their first sentences. None of these improvements were observed in the placebo group. Larger and longer studies are needed to confirm this promising discovery. This review introduces the concept of M2 (anti-inflammatory) and M1 (pro-inflammatory) mitochondria that are polarized along a functional continuum according to cell stress. The pathophysiology of the CDR, the complementary functions of M1 and M2 mitochondria, relevant gene-environment interactions, and the metabolic underpinnings of behavior are discussed as foundation stones for understanding the improvements in ASD behaviors produced by antipurinergic therapy in this small clinical trial.

RAI1 gene mutations: mechanisms of Smith-Magenis syndrome

Smith-Magenis syndrome (SMS; OMIM #182290) is a complex genetic disorder characterized by distinctive physical features, developmental delay, cognitive impairment, and a typical behavioral phenotype. SMS is caused by interstitial 17p11.2 deletions, encompassing multiple genes and including the retinoic acid-induced 1 gene (RAI1), or by mutations in RAI1 itself. About 10% of all the SMS patients, in fact, carry an RAI1 mutation responsible for the phenotype. RAI1 (OMIM *607642) is a dosage-sensitive gene expressed in many tissues and highly conserved among species. Over the years, several studies have demonstrated that RAI1 (or its homologs in animal models) acts as a transcriptional factor implicated in embryonic neurodevelopment, neuronal differentiation, cell growth and cell cycle regulation, bone and skeletal development, lipid and glucose metabolisms, behavioral functions, and circadian activity. Patients with RAI1 pathogenic variants show some phenotypic differences when compared to those carrying the typical deletion. They usually have lower incidence of hypotonia and less cognitive impairment than those with 17p11.2 deletions but more frequently show the behavioral characteristics of the syndrome and overeating issues. These differences reflect the primary pathogenetic role of RAI1 without the pathogenetic contribution of the other genes included in the typical 17p11.2 deletion. The better comprehension of physiological roles of RAI1, its molecular co-workers and interactors, and its contribution in determining the typical SMS phenotype will certainly open a new path for therapeutic interventions.

A New Patient with Potocki-Lupski Syndrome: A Literature Review

Speech delay, intellectual disability, and behavioral disturbances are the main clinical manifestations of Potocki-Lupski syndrome. Other features include infantile hypotonia, the absence of major dysmorphism, sleep disorders, and congenital anomalies, particularly of the cardiovascular system. A male patient with Potocki-Lupski syndrome is reported herein. He showed speech and borderline cognitive delay, behavioral troubles with no signs suggestive of autism, in the absence of major dysmorphism. A de novo 17p12-p11.2 duplication spanning 3.6 Mb was detected, with boundaries from 15,284,052 to 18,647,233 (hg19 assembly). At the age of 5 years, the child showed a noticeable improvement of speech skills and a moderate scholastic performance was reached. Upon analysis of the clinical manifestations of the present patient and those reported in existing literature, we found that the syndrome may present in various degrees of clinical expressivity. Affected patients may manifest symptoms ranging from mild behavioral disturbances to severe degrees of autism.

The interrelationship of metabolic syndrome and neurodegenerative diseases with focus on brain-derived neurotrophic factor (BDNF): Kill two birds with one stone

The brain-derived neurotrophic factor (BDNF) is involved in metabolic syndrome (MetS) and neurodegenerative diseases (NDD) like Alzheimer's disease, Huntington's disease, Parkinson's disease and depression. If one factor plays an essential role in the pathogenesis of two diseases, it can be concluded that there might be a common root in these two diseases, as well. This review was aimed to highlight the crucial roles of BDNF in the pathogenesis of MetS and NDD and to introduce sole prophylactic or therapeutic applications, BDNF gene therapy and BDFN administration, in controlling MetS and NDD.

Rai1 frees mice from the repression of active wake behaviors by light

Besides its role in vision, light impacts physiology and behavior through circadian and direct (aka ‘masking’) mechanisms. In Smith-Magenis syndrome (SMS), the dysregulation of both sleep-wake behavior and melatonin production strongly suggests impaired non-visual light perception. We discovered that mice haploinsufficient for the SMS causal gene, Retinoic acid induced-1 (Rai1), were hypersensitive to light such that light eliminated alert and active-wake behaviors, while leaving time-spent-awake unaffected. Moreover, variables pertaining to circadian rhythm entrainment were activated more strongly by light. At the input level, the activation of rod/cone and suprachiasmatic nuclei (SCN) by light was paradoxically greatly reduced, while the downstream activation of the ventral-subparaventricular zone (vSPVZ) was increased. The vSPVZ integrates retinal and SCN input and, when activated, suppresses locomotor activity, consistent with the behavioral hypersensitivity to light we observed. Our results implicate Rai1 as a novel and central player in processing non-visual light information, from input to behavioral output.

DOI:http://dx.doi.org/10.7554/eLife.23292.001

Rai1 Haploinsufficiency Is Associated with Social Abnormalities in Mice

Background: Autism is characterized by difficulties in social interaction, communication, and repetitive behaviors; with different degrees of severity in each of the core areas. Haploinsufficiency and point mutations of RAI1 are associated with Smith-Magenis syndrome (SMS), a genetic condition that scores within the autism spectrum range for social responsiveness and communication, and is characterized by neurobehavioral abnormalities, intellectual disability, developmental delay, sleep disturbance, and self-injurious behaviors. Methods: To investigate the relationship between Rai1 and social impairment, we evaluated the Rai1^+/− mice with a battery of tests to address social behavior in mice. Results: We found that the mutant mice showed diminished interest in social odors, abnormal submissive tendencies, and increased repetitive behaviors when compared to wild type littermates. Conclusions: These findings suggest that Rai1 contributes to social behavior in mice, and prompt it as a candidate gene for the social behaviors observed in Smith-Magenis Syndrome patients.