GNAO1 organizes the cytoskeletal remodeling and firing of developing neurons

An N-terminal and ankyrin repeat domain interactome of Shank3 identifies the protein complex with the splicing regulator Nono in mice

An autism-associated gene Shank3 encodes multiple splicing isoforms, Shank3a-f. We have recently reported that Shank3a/b-knockout mice were more susceptible to kainic acid-induced seizures than wild-type mice at 4 weeks of age. Little is known, however, about how the N-terminal and ankyrin repeat domains (NT-Ank) of Shank3a/b regulate multiple molecular signals in the developing brain. To explore the functional roles of Shank3a/b, we performed a mass spectrometry-based proteomic search for proteins interacting with GFP-tagged NT-Ank. In this study, NT-Ank was predicted to form a variety of complexes with a total of 348 proteins, in which RNA-binding (n = 102), spliceosome (n = 22), and ribosome-associated molecules (n = 9) were significantly enriched. Among them, an X-linked intellectual disability-associated protein, Nono, was identified as a NT-Ank-binding protein. Coimmunoprecipitation assays validated the interaction of Shank3 with Nono in the mouse brain. In agreement with these data, the thalamus of Shank3a/b-knockout mice aberrantly expressed splicing isoforms of autism-associated genes, Nrxn1 and Eif4G1, before and after seizures with kainic acid treatment. These data indicate that Shank3 interacts with multiple RNA-binding proteins in the postnatal brain, thereby regulating the homeostatic expression of splicing isoforms for autism-associated genes after birth.

The immunoreactive signature of monocyte-derived dendritic cells from patients with Down syndrome

The clinical spectrum of Down syndrome (DS) ranges from congenital malformations to premature aging and early-onset senescence. Excessive immunoreactivity and oxidative stress are thought to accelerate the pace of aging in DS patients; however, the immunological profile remains elusive. We investigated whether peripheral blood monocyte-derived dendritic cells (MoDCs) in DS patients respond to lipopolysaccharide (LPS) distinctly from non-DS control MoDCs. Eighteen DS patients (age 2-47 years, 12 males) and 22 controls (age 4-40 years, 15 males) were enrolled. CD14-positive monocytes were immunopurified and cultured for 7 days in the presence of granulocyte-macrophage colony-stimulating factor and IL-4, yielding MoDCs in vitro. After the LPS-stimulation for 48 hours from days 7 to 9, culture supernatant cytokines were measured by multiplex cytokine bead assays, and bulk-prepared RNA from the cells was used for transcriptomic analyses. MoDCs from DS patients produced cytokines/chemokines (IL-6, IL-8, TNF-α, MCP-1, and IP-10) at significantly higher levels than those from controls in response to LPS. RNA sequencing revealed that DS-derived MoDCs differentially expressed 137 genes (74 upregulated and 63 downregulated) compared with controls. A gene enrichment analysis identified 5 genes associated with Toll-like receptor signaling (KEGG: hsa04620, P = 0.00731) and oxidative phosphorylation (hsa00190, P = 0.0173) pathways. MoDCs obtained from DS patients showed higher cytokine or chemokine responses to LPS than did control MoDCs. Gene expression profiles suggest that hyperactive Toll-like receptor and mitochondrial oxidative phosphorylation pathways configure the immunoreactive signature of MoDCs in DS patients.

Gnao1 is a molecular switch that regulates the Rho signaling pathway in differentiating neurons

GNAO1 encodes G protein subunit alpha O1 (Gαo). Pathogenic variations in GNAO1 cause developmental delay, intractable seizures, and progressive involuntary movements from early infancy. Because the functional role of GNAO1 in the developing brain remains unclear, therapeutic strategies are still unestablished for patients presenting with GNAO1-associated encephalopathy. We herein report that siRNA-mediated depletion of Gnao1 perturbs the expression of transcripts associated with Rho GTPase signaling in Neuro2a cells. Consistently, siRNA treatment hampered neurite outgrowth and extension. Growth cone formation was markedly disrupted in monolayer neurons differentiated from iPSCs from a patient with a pathogenic variant of Gαo (p.G203R). This variant disabled neuro-spherical assembly, acquisition of the organized structure, and polarized signals of phospho-MLC2 in cortical organoids from the patient's iPSCs. We confirmed that the Rho kinase inhibitor Y27632 restored these morphological phenotypes. Thus, Gαo determines the self-organizing process of the developing brain by regulating the Rho-associated pathway. These data suggest that Rho GTPase pathway might be an alternative target of therapy for patients with GNAO1-associated encephalopathy.

Dyskinetic crisis in GNAO1-related disorders: clinical perspectives and management strategies

Background

GNAO1-related disorders (GNAO1-RD) encompass a diverse spectrum of neurodevelopmental and movement disorders arising from variants in the GNAO1 gene. Dyskinetic crises, marked by sudden and intense exacerbations of abnormal involuntary movements, present a significant challenge in GNAO1-RD.

Objectives

This study aimed to establish a standardized framework for understanding dyskinetic crises, addressing crucial aspects such as definition, triggers, diagnostic criteria, complications, and management strategies.

Methods

A Delphi consensus process was conducted involving international experts in GNAO1-RD. The panel of thirteen experts participated in three voting rounds, discussing 90 statements generated through a literature review and clinical expertise.

Results

Consensus was achieved on 31 statements, defining dyskinetic crises as abrupt, paroxysmal episodes involving distinct abnormal movements in multiple body regions, triggered by emotional stress or infections. Dyskinetic crises may lead to functional impairment and complications, emphasizing the need for prompt recognition. While individualized pharmacological recommendations were not provided, benzodiazepines and clonidine were suggested for acute crisis management. Chronic treatment options included tetrabenazine, benzodiazepines, gabapentin, and clonidine. Deep brain stimulation should be considered early in the treatment of refractory or prolonged dyskinetic crisis.

Conclusion

This consensus provides a foundation for understanding and managing dyskinetic crises in GNAO1-RD for clinicians, caregivers, and researchers. The study emphasizes the importance of targeted parental and caregiver education, which enables early recognition and intervention, thereby potentially minimizing both short- and long-term complications. Future research should concentrate on differentiating dyskinetic crises from other neurological events and investigating potential risk factors that influence their occurrence and nature. The proposed standardized framework improves clinical management, stakeholder communication, and future GNAO1-RD research.

ATP1A3 regulates protein synthesis for mitochondrial stability under heat stress

Pathogenic variants in ATP1A3, the gene encoding the α3 subunit of the Na+/K+-ATPase, cause alternating hemiplegia of childhood (AHC) and related disorders. Impairments in Na+/K+-ATPase activity are associated with the clinical phenotype. However, it remains unclear whether additional mechanisms are involved in the exaggerated symptoms under stressed conditions in patients with AHC. We herein report that the intracellular loop (ICL) of ATP1A3 interacted with RNA-binding proteins, such as Eif4g (encoded by Eif4g1), Pabpc1 and Fmrp (encoded by Fmr1), in mouse Neuro2a cells. Both the siRNA-mediated depletion of Atp1a3 and ectopic expression of the p.R756C variant of human ATP1A3-ICL in Neuro2a cells resulted in excessive phosphorylation of ribosomal protein S6 (encoded by Rps6) and increased susceptibility to heat stress. In agreement with these findings, induced pluripotent stem cells (iPSCs) from a patient with the p.R756C variant were more vulnerable to heat stress than control iPSCs. Neurons established from the patient-derived iPSCs showed lower calcium influxes in responses to stimulation with ATP than those in control iPSCs. These data indicate that inefficient protein synthesis contributes to the progressive and deteriorating phenotypes in patients with the p.R756C variant among a variety of ATP1A3-related disorders.

Molecular Dynamic Simulations to Determine Individualized Therapy: Tetrabenazine for the GNAO1 Encephalopathy E246K Variant

INTRODUCTION

GNAO1 encephalopathy is characterized by severe hypotonia, psychomotor retardation, epilepsy, and movement disorders. Genetic variations in GNAO1 have been linked to neurological symptoms including movement disorders like dystonia. The correlation between the E246K mutation in the Gα subunit and aberrant signal transduction of G proteins has been established but no data are reported regarding the efficacy of medical treatment with tetrabenazine.

METHODS

Molecular modeling studies were performed to elucidate the molecular mechanisms underlying this mutation. We developed drug efficacy models using molecular dynamic simulations that replicated the behavior of wild-type and mutated proteins in the presence or absence of ligands.

RESULTS AND DISCUSSION

We demonstrated that the absence of the mutation leads to normal signal transduction upon receptor activation by the endogenous ligand, but not in the presence of tetrabenazine. In contrast, the presence of the mutation resulted in abnormal signal transduction in the presence of the endogenous ligand, which was corrected by the drug tetrabenazine. Tetrabenazine was identified as a promising therapeutic option for pediatric patients suffering from encephalopathy due to an E246K mutation in the GNAO1 gene validated through molecular dynamics. This is a potential first example of the use of this technique in a rare neurological pediatric disease.

RNA Interference Effectors Selectively Silence the Pathogenic Variant GNAO1 c.607 G > A In Vitro

RNA interference (RNAi)-based therapeutics hold the potential for dominant genetic disorders, enabling sequence-specific inhibition of pathogenic gene products. We aimed to direct RNAi for the selective suppression of the heterozygous GNAO1 c.607 G > A variant causing GNAO1 encephalopathy. By screening short interfering RNA (siRNA), we showed that GNAO1 c.607G>A is a druggable target for RNAi. The si1488 candidate achieved at least twofold allelic discrimination and downregulated mutant protein to 35%. We created vectorized RNAi by incorporating the si1488 sequence into the short hairpin RNA (shRNA) in the adeno-associated virus (AAV) vector. The shRNA stem and loop were modified to improve the transcription, processing, and guide strand selection. All tested shRNA constructs demonstrated selectivity toward mutant GNAO1, while tweaking hairpin structure only marginally affected the silencing efficiency. The selectivity of shRNA-mediated silencing was confirmed in the context of AAV vector transduction. To conclude, RNAi effectors ranging from siRNA to AAV-RNAi achieve suppression of the pathogenic GNAO1 c.607G>A and discriminate alleles by the single-nucleotide substitution. For gene therapy development, it is crucial to demonstrate the benefit of these RNAi effectors in patient-specific neurons and animal models of the GNAO1 encephalopathy.

Cortical neurons obtained from patient-derived iPSCs with GNAO1 p.G203R variant show altered differentiation and functional properties

Pathogenic variants in the GNAO1 gene, encoding the alpha subunit of an inhibitory heterotrimeric guanine nucleotide-binding protein (Go) highly expressed in the mammalian brain, have been linked to encephalopathy characterized by different combinations of neurological symptoms, including developmental delay, hypotonia, epilepsy and hyperkinetic movement disorder with life-threatening paroxysmal exacerbations. Currently, there are only symptomatic treatments, and little is known about the pathophysiology of GNAO1-related disorders. Here, we report the characterization of a new in vitro model system based on patient-derived induced pluripotent stem cells (hiPSCs) carrying the recurrent p.G203R amino acid substitution in Gαo, and a CRISPR-Cas9-genetically corrected isogenic control line. RNA-Seq analysis highlighted aberrant cell fate commitment in neuronal progenitor cells carrying the p.G203R pathogenic variant. Upon differentiation into cortical neurons, patients' cells showed reduced expression of early neural genes and increased expression of astrocyte markers, as well as premature and defective differentiation processes leading to aberrant formation of neuronal rosettes. Of note, comparable defects in gene expression and in the morphology of neural rosettes were observed in hiPSCs from an unrelated individual harboring the same GNAO1 variant. Functional characterization showed lower basal intracellular free calcium concentration ([Ca2+]i), reduced frequency of spontaneous activity, and a smaller response to several neurotransmitters in 40- and 50-days differentiated p.G203R neurons compared to control cells. These findings suggest that the GNAO1 pathogenic variant causes a neurodevelopmental phenotype characterized by aberrant differentiation of both neuronal and glial populations leading to a significant alteration of neuronal communication and signal transduction.

Lineage commitment pathways epigenetically oppose oncogenic Gαq/11-YAP signaling in dormant disseminated uveal melanoma

The mechanisms driving late relapse in uveal melanoma (UM) patients remains a medical mystery and major challenge. Clinically it is inferred that UM disseminated cancer cells (DCCs) persist asymptomatic for years-to-decades mainly in the liver before they manifest as symptomatic metastasis. Here we reveal using Gαq/11 mut /BAP wt human uveal melanoma models and human UM metastatic samples, that the neural crest lineage commitment nuclear receptor NR2F1 is a key regulator of spontaneous UM DCC dormancy in the liver. Using a quiescence reporter, RNA-seq and multiplex imaging we revealed that rare dormant UM DCCs upregulate NR2F1 expression and genes related to neural crest programs while repressing gene related to cell cycle progression. Gain and loss of function assays showed that NR2F1 silences YAP1/TEAD1 transcription downstream of Gαq/11 signaling and that NR2F1 expression can also be repressed by YAP1. YAP1 expression is repressed by NR2F1 binding to its promoter and changing the histone H3 tail activation marks to repress YAP1 transcription. In vivo CRISPR KO of NR2F1 led dormant UM DCCs to awaken and initiate relentless liver metastatic growth. Cut&Run and bulk RNA sequencing further confirmed that NR2F1 epigenetically stimulates neuron axon guidance and neural lineage programs, and it globally represses gene expression linked to G-protein signaling to drive dormancy. Pharmacological inhibition of Gαq/11 mut signaling resulted in NR2F1 upregulation and robust UM growth arrest, which was also achieved using a novel NR2F1 agonist. Our work sheds light on the molecular underpinnings of UM dormancy revealing that transcriptional programs driven by NR2F1 epigenetically short-circuit Gαq/11 signaling to its downstream target YAP1.

Highlights

Quiescent solitary uveal melanoma (UM) DCCs in the liver up- and down-regulate neural crest and cell cycle progression programs, respectively.NR2F1 drives solitary UM DCC dormancy by antagonizing the Gαq/11-YAP1 pathway; small molecule Gαq/11 inhibition restores NR2F1 expression and quiescence. NR2F1 short-circuits oncogenic YAP1 and G-protein signaling via a chromatin remodeling program. Loss of function of NR2F1 in dormant UM DCCs leads to aggressive liver metastasis.

Graphical abstract

Severity of GNAO1-Related Disorder Correlates with Changes in G-Protein Function

OBJECTIVE

GNAO1-related disorders (OMIM #615473 and #617493), caused by variants in the GNAO1 gene, are characterized by developmental delay or intellectual disability, hypotonia, movement disorders, and epilepsy. Neither a genotype-phenotype correlation nor a clear severity score have been established for this disorder. The objective of this prospective and retrospective observational study was to develop a severity score for GNAO1-related disorders, and to delineate the correlation between the underlying molecular mechanisms and clinical severity.

METHODS

A total of 16 individuals with GNAO1-related disorders harboring 12 distinct missense variants, including four novel variants (p.K46R, p.T48I, p.R209P, and p.L235P), were examined with repeated clinical assessments, video-electroencephalogram monitoring, and brain magnetic resonance imaging. The molecular pathology of each variant was delineated using a molecular deconvoluting platform.

RESULTS

The patients displayed a wide variability in the severity of their symptoms. This heterogeneity was well represented in the GNAO1-related disorders severity score, with a broad range of results. Patients with the same variant had comparable severity scores, indicating that differences in disease profiles are not due to interpatient variability, but rather, to unique disease mechanisms. Moreover, we found a significant correlation between clinical severity scores and molecular mechanisms.

INTERPRETATION

The clinical score proposed here provides further insight into the correlation between pathophysiology and phenotypic severity in GNAO1-related disorders. We found that each variant has a unique profile of clinical phenotypes and pathological molecular mechanisms. These findings will contribute to better understanding GNAO1-related disorders. Additionally, the severity score will facilitate standardization of patients categorization and assessment of response to therapies in development. ANN NEUROL 2023;94:987-1004.

Genotype-phenotype correlation and treatment effects in young patients with GNAO1-associated disorders

BACKGROUND

Patients carrying pathogenic variants in GNAO1 often present with early-onset central hypotonia and global developmental delay, with or without epilepsy. As the disorder progresses, a complex hypertonic and hyperkinetic movement disorder is a common phenotype. A genotype-phenotype correlation has not yet been described and there are no evidence-based therapeutic recommendations.

METHODS

To improve understanding of the clinical course and pathophysiology of this ultra-rare disorder, we built up a registry for GNAO1 patients in Germany. In this retrospective, multicentre cohort study, we collected detailed clinical data, treatment effects and genetic data for 25 affected patients.

RESULTS

The main clinical features were symptom onset within the first months of life, with central hypotonia or seizures. Within the first year of life, nearly all patients developed a movement disorder comprising dystonia (84%) and choreoathetosis (52%). Twelve (48%) patients suffered life-threatening hyperkinetic crises. Fifteen (60%) patients had epilepsy with poor treatment response. Two patients showed an atypical phenotype and seven novel pathogenic variants in GNAO1 were identified. Nine (38%) patients were treated with bilateral deep brain stimulation of the globus pallidus internus. Deep brain stimulation reduced hyperkinetic symptoms and prevented further hyperkinetic crises. The in silico prediction programmes did not predict the phenotype by the genotype.

CONCLUSION

The broad clinical spectrum and genetic findings expand the phenotypical spectrum of GNAO1-associated disorder and therefore disprove the assumption that there are only two main phenotypes. No specific overall genotype-phenotype correlation was identified. We highlight deep brain stimulation as a useful treatment option in this disorder.

Heterogeneity and mitochondrial vulnerability configurate the divergent immunoreactivity of human induced microglia-like cells

Microglia play versatile roles in progression of and protection against neuroinflammatory diseases. Little is known, however, about the mechanisms underlying the diverse reactivity of microglia to inflammatory conditions. We investigated how human induced microglia-like (iMG) cells respond to innate immune ligands. Quantitative PCR showed that poly-I:C and lipopolysaccharide (LPS) activated the expression of IL1B and TNF. Immunoreactivity of iMG did not differ between controls (n = 11) and patients with neuroinflammatory diseases (n = 24). Flow cytometry revealed that CD14high cells expressed interleukin (IL) -1β after LPS treatment. Immunoblotting showed that poly-I:C and LPS differentially activated inflammatory pathways but commonly induced mitochondrial instability and the expression of pyruvate kinase isoform M2 (PKM2). Furthermore, a potent stimulator of PKM2 (DASA-58) alleviated IL-1β production after LPS treatment. These data indicate that heterogeneous cell populations and mitochondrial stability underlie the divergent immunoreactivity of human iMG in environments.

A beginner's guide on the use of brain organoids for neuroscientists: a systematic review

BACKGROUND

The first human brain organoid protocol was presented in the beginning of the previous decade, and since then, the field witnessed the development of many new brain region-specific models, and subsequent protocol adaptations and modifications. The vast amount of data available on brain organoid technology may be overwhelming for scientists new to the field and consequently decrease its accessibility. Here, we aimed at providing a practical guide for new researchers in the field by systematically reviewing human brain organoid publications.

METHODS

Articles published between 2010 and 2020 were selected and categorised for brain organoid applications. Those describing neurodevelopmental studies or protocols for novel organoid models were further analysed for culture duration of the brain organoids, protocol comparisons of key aspects of organoid generation, and performed functional characterisation assays. We then summarised the approaches taken for different models and analysed the application of small molecules and growth factors used to achieve organoid regionalisation. Finally, we analysed articles for organoid cell type compositions, the reported time points per cell type, and for immunofluorescence markers used to characterise different cell types.

RESULTS

Calcium imaging and patch clamp analysis were the most frequently used neuronal activity assays in brain organoids. Neural activity was shown in all analysed models, yet network activity was age, model, and assay dependent. Induction of dorsal forebrain organoids was primarily achieved through combined (dual) SMAD and Wnt signalling inhibition. Ventral forebrain organoid induction was performed with dual SMAD and Wnt signalling inhibition, together with additional activation of the Shh pathway. Cerebral organoids and dorsal forebrain model presented the most cell types between days 35 and 60. At 84 days, dorsal forebrain organoids contain astrocytes and potentially oligodendrocytes. Immunofluorescence analysis showed cell type-specific application of non-exclusive markers for multiple cell types.

CONCLUSIONS

We provide an easily accessible overview of human brain organoid cultures, which may help those working with brain organoids to define their choice of model, culture time, functional assay, differentiation, and characterisation strategies.

CRISPR/Cas9-generated mouse model with humanizing single-base substitution in the Gnao1 for safety studies of RNA therapeutics

The development of personalized medicine for genetic diseases requires preclinical testing in the appropriate animal models. GNAO1 encephalopathy is a severe neurodevelopmental disorder caused by heterozygous de novo mutations in the GNAO1 gene. GNAO1 c.607 G>A is one of the most common pathogenic variants, and the mutant protein Gαo-G203R likely adversely affects neuronal signaling. As an innovative approach, sequence-specific RNA-based therapeutics such as antisense oligonucleotides or effectors of RNA interference are potentially applicable for selective suppression of the mutant GNAO1 transcript. While in vitro validation can be performed in patient-derived cells, a humanized mouse model to rule out the safety of RNA therapeutics is currently lacking. In the present work, we employed CRISPR/Cas9 technology to introduce a single-base substitution into exon 6 of the Gnao1 to replace the murine Gly203-coding triplet (GGG) with the codon used in the human gene (GGA). We verified that genome-editing did not interfere with the Gnao1 mRNA or Gαo protein synthesis and did not alter localization of the protein in the brain structures. The analysis of blastocysts revealed the off-target activity of the CRISPR/Cas9 complexes; however, no modifications of the predicted off-target sites were detected in the founder mouse. Histological staining confirmed the absence of abnormal changes in the brain of genome-edited mice. The created mouse model with the “humanized” fragment of the endogenous Gnao1 is suitable to rule out unintended targeting of the wild-type allele by RNA therapeutics directed at lowering GNAO1 c.607 G>A transcripts.

Gln52 mutations in GNAO1-related disorders and personalized drug discovery

•Gln52 mutations have been found in patients with GNAO1-related disorders.•Gln52 can be mutated to Pro and Arg, leading to different clinical manifestations.•Personalized drug discovery is tailored to specific GNAO1 mutations.

Shank3a/b isoforms regulate the susceptibility to seizures and thalamocortical development in the early postnatal period of mice

Epileptic seizures are distinct but frequent comorbidities in children with autism spectrum disorder (ASD). The hyperexcitability of cortical and subcortical neurons appears to be involved in both phenotypes. However, little information is available concerning which genes are involved and how they regulate the excitability of the thalamocortical network. In this study, we investigate whether an ASD-associated gene, SH3 and multiple ankyrin repeat domains 3 (Shank3), plays a unique role in the postnatal development of thalamocortical neurons. We herein report that Shank3a/b, the splicing isoforms of mouse Shank3, were uniquely expressed in the thalamic nuclei, peaking from two to four weeks after birth. Shank3a/b-knockout mice showed lower parvalbumin signals in the thalamic nuclei. Consistently, Shank3a/b-knockout mice were more susceptible to generalized seizures than wild-type mice after kainic acid treatments. Together, these data indicate that NT-Ank domain of Shank3a/b regulates molecular pathways that protect thalamocortical neurons from hyperexcitability during the early postnatal period of mice.

Restoration of the GTPase activity and cellular interactions of Gαo mutants by Zn2+ in GNAO1 encephalopathy models

De novo point mutations in GNAO1, gene encoding the major neuronal G protein Gα_o, have recently emerged in patients with pediatric encephalopathy having motor, developmental, and epileptic dysfunctions. Half of clinical cases affect codons Gly²⁰³, Arg²⁰⁹, or Glu²⁴⁶; we show that these mutations accelerate GTP uptake and inactivate GTP hydrolysis through displacement Gln²⁰⁵ critical for GTP hydrolysis, resulting in constitutive GTP binding by Gα_o. However, the mutants fail to adopt the activated conformation and display aberrant interactions with signaling partners. Through high-throughput screening of approved drugs, we identify zinc pyrithione and Zn²⁺ as agents restoring active conformation, GTPase activity, and cellular interactions of the encephalopathy mutants, with negligible effects on wild-type Gα_o. We describe a Drosophila model of GNAO1 encephalopathy where dietary zinc restores the motor function and longevity of the mutant flies. Zinc supplements are approved for diverse human neurological conditions. Our work provides insights into the molecular etiology of GNAO1 encephalopathy and defines a potential therapy for the patients.

Translational pediatrics: clinical perspective for Phelan-McDermid syndrome and autism research

Phelan-McDermid syndrome (PMS) is a rare genetic disorder presenting with developmental delay, epilepsy, and autism spectrum disorder (ASD). The segmental deletion of chromosome 22q13.3 affects the copy number of SHANK3, the gene encoding a scaffolding protein at the postsynaptic density. Biological studies indicate that SHANK3 plays crucial roles in the development of synaptic functions in the postnatal brain. Notably, induced pluripotent stem (iPS) cells have enabled researchers to develop brain organoids and microglia from patients and to explore the pathophysiology of neurodevelopmental disorders in human cells. Single-cell RNA sequencing of these cells revealed that human-specific genes are uniquely expressed during cortical development. Thus, patient-derived disease models are expected to identify as-yet-unidentified functions of SHANK3 in the development of human brain. These efforts may help establish a new style of translational research in pediatrics, which is expected to provide therapeutic insight for children with PMS and broader categories of disease. IMPACT: Phelan-McDermid syndrome is a prototypic model for molecular studies of autism spectrum disorder. Brain organoids are expected to provide therapeutic insight. Single-cell RNA sequencing of microglia may uncover the functional roles of human-specific genes.