Aug 2026· Molecular Psychiatry· 0 citations· 80 references
Medicine
TL;DR
The first comprehensive human mechanistic model of PPP1R9A haploinsufficiency using an isogenic CRISPR/Cas9-engineered iPSC system differentiated into cortical neurons is established, providing a human-specific mechanistic framework linking reduced Neurabin I dosage to neurodevelopmental and psychiatric disease risk.
Abstract
Heterozygous loss-of-function variants in Neurabin I (PPP1R9A), responsible for encoding a cytoskeletal scaffolding protein essential for synaptic plasticity, are recurrently associated with neurodevelopmental and neuropsychiatric disorders, yet their direct effects on human neuronal maturation remain unclear. Here, we establish the first comprehensive human mechanistic model of PPP1R9A haploinsufficiency using an isogenic CRISPR/Cas9-engineered iPSC system differentiated into cortical neurons to define dosage-dependent functional consequences. PPP1R9A+/- neurons exhibited pronounced hyperspinogenesis and increased neuritic complexity, indicative of aberrant structural maturation; however, whole-cell patch-clamp recordings revealed impaired intrinsic excitability, including reduced action potential firing, altered waveform properties, and defective axo-somatic coupling, uncovering a striking dissociation between neuronal morphology and function. Long-read single-cell transcriptomics and quantitative proteomics identified coordinated downregulation of ion channel and synaptic transmission pathways, including genes essential for sodium channel function and glutamatergic signaling, together with disruption of synaptic vesicle cycling, axon guidance, and neurodevelopmental programs. Pseudotime trajectory analysis further demonstrated delayed neuronal differentiation, with mutant neurons accumulating at intermediate developmental states rather than acquiring mature cortical identities. Importantly, molecular rescue experiments confirmed causality, as restoration of full-length PPP1R9A expression robustly normalized transcriptional and synaptic signaling programs, whereas allele-specific antisense oligonucleotide-mediated suppression of the mutant transcript achieved only partial rescue. Taken together, these findings establish PPP1R9A haploinsufficiency as a driver of impaired molecular, electrophysiological, and developmental maturation in human cortical neurons, providing a human-specific mechanistic framework linking reduced Neurabin I dosage to neurodevelopmental and psychiatric disease risk.
It is demonstrated that SYNGAP1 haploinsufficiency disrupts early human brain development and accelerates intrinsic neuronal maturation, with pathogenic mechanisms emerging before synaptogenesis and extending beyond SYNGAP1’s established synaptic role.
Montanna Waters, Lucas Teasdale, Sean Byars et al.· bioRxiv· 0 citations
Neurexins and neuroligins are evolutionarily conserved synaptic adhesion molecules that play essential roles in synapse formation and neural circuit function, with mutations linked to neurodevelopmental disorders such as autism. Here, we combined whole-transcriptome sequencing with phenotypic characterization to define the molecular consequences of neurexin and neuroligin deficiency in Caenorhabditis elegans. Young adult worms carrying allele-specific loss-of-function mutations in nrx-1 (ok1649 and tm1961) or nlg-1 (ok259 and tm474), orthologues for human NRXNs or NLGNs, respectively, were subjected to RNA sequencing and compared with wild-type animals. Mutant strains exhibited impaired growth, altered locomotor activity, increased social aggregation, and reduced ventral nerve cord neuronal integrity. Transcriptomic analysis revealed extensive gene-expression changes, particularly in the nrx-1 (tm1961) allele, with dysregulation of genes involved in cuticle development, neuronal signaling, protein homeostasis, innate immunity, mitochondrial organization, and transcriptional regulation. Gene Ontology and KEGG enrichment analyses identified significant perturbations in developmental, metabolic, stress-response, translational, and synaptic pathways. Together, these findings demonstrate that disruption of neurexin–neuroligin signaling drives transcriptional reprogramming that extends beyond synaptic dysfunction, linking molecular alterations to developmental, behavioral, and neuromorphological abnormalities.
Omamuyouwi M Ijomone, Victor E. Anadu, Toheeb O. Oyerinde et al.· Research Square· 0 citations
Findings establish OCNDS as a disorder of compartment-specific translational dysregulation driven by impaired CK2α–G3BP1 control of RNA granule homeostasis, and establish G3bp1 knockdown rescues translational and morphological phenotypes across all OCNDS alleles.
GNB1 encephalopathy (GNB1-E) is a rare neurodevelopmental disorder associated with motor dysfunction, epilepsy and learning disability caused by mutations in the gene encoding the G protein subunit Gβ1. Previous work has shown that altered Gβ1 can disrupt activation of G-protein-coupled inwardly rectifying potassium (GIRK) channels, dysregulate neuronal excitability and cause seizures. However, the relevant upstream regulators of Gβ1 and the consequences of GIRK dysfunction for neuronal synaptic, cellular and circuit function have not been characterized. Here we report that mice of both sexes carrying the deleterious p.I80T mutation in Gnb1 present features consistent with GNB1-E, including developmental delay, decreased locomotion and increased anxiety. Using histology, whole-cell patch-clamp electrophysiology and pharmacology in ex vivo brain slices, we find that hippocampal neurons in heterozygous Gnb1I80T/+ mice exhibit simplified dendritic morphologies, decreased synaptic inhibition mediated by metabotropic GABAB receptors and increased dendritic excitability. These phenotypes result in longer duration dendritic calcium spikes in response to synaptic afferent stimulation, an effect that is reversed by a specific activator of GIRK channels, ML297. Given the known roles of dendritic calcium spikes in driving burst firing and inducing synaptic plasticity, these findings suggest that targeting dendritic excitability has therapeutic potential to address both the seizure susceptibility and learning deficits associated with GNB1-E. Significance Statement GNB1 encephalopathy (GNB1-E) is a rare neurodevelopmental disorder associated with motor dysfunction, epilepsy and learning disability for which there are currently no mechanism-based treatments. Here we show that a pathogenic variant of the G protein subunit Gβ1 impairs activation of neuronal G-protein-coupled inwardly rectifying potassium (GIRK) channels by inhibitory synaptic GABAB receptors. This leads to increased dendritic excitability and longer duration dendritic calcium spikes in mouse hippocampal neurons in response to stimulation of synaptic inputs. We find that this phenotype is reversed by a drug that activates GIRK channels, opening pathways to develop therapies for GNB1-E that specifically target dendritic excitability.
Sam Gritz, Anshul Voleti, Matthew S. Scarnati et al.· bioRxiv· 0 citations
During development, neurexin-2 (NRXN2) is a cell adhesion molecule localized to presynaptic terminals as well as axonal shafts and immature neurites, where it participates in the regulation of neuronal cell morphogenesis. Given its critical role in early neuronal development, NRXN2 is considered a susceptibility gene product for neurodevelopmental disorders (NDDs) such as autism spectrum disorder (ASD) and intellectual disability (ID). However, the intracellular signaling mechanisms linking NRXN2 deficiency to abnormal neuronal cell morphology remain unclear. Herein, we investigated the molecular basis of excessive cell morphogenesis induced by the knockdown of NRXN2 using the N1E-115 cell line, a model of neuronal morphogenesis characterized by neurite outgrowth. Silencing NRXN2 using the clustered regularly interspaced short palindromic repeat (CRISPR)/Cas13 system resulted in a marked enhancement of process elongation. Mechanistically, we found that Girdin (also called GIV or CCDC88A), a non-receptor guanine nucleotide exchange factor for heterotrimeric G proteins, can mediate the excessive process length phenotype. Transfection of either the regulator of G protein signaling (RGS) domain of RGS3, a GTPase-activating protein for G proteins, or the G protein-binding domain of engulfment and cell motility 1 (ELMO1) rescued the excessive process formation. Similar results were obtained in primary cortical neurons. In addition, these interventions normalized downstream Rac1 activity in cells. Together, our findings elucidate Girdin signaling as a mediator of excessive neuronal process formation following NRXN2 knockdown, providing mechanistic insight into how the loss of function of NRXN2 leads to aberrant cell morphogenesis at least at the molecular and cellular levels. These results suggest that signaling through Girdin may contribute to the morphological abnormalities associated with NRXN2-related neurodevelopmental disorders.
Hideji Yako, Mikito Takahashi, Mami Akiyama et al.· International Journal of Mol...· 1 citation
These findings identify ankyrin-G as a molecular bridge between excitatory neuronal activity, synaptic structure, and myelin-associated protein expression, revealing a pathway by which ANK3 variants may contribute to neuropsychiatric disease.
Sehyoun Yoon, Marc Dos Santos, Natalia Khalatyan et al.· Proceedings of the National...· 0 citations
