Structural interaction between DISC1 and ATF4 underlying transcriptional and synaptic dysregulation in an iPSC model of mental disorders

Deep sequencing of proteotoxicity modifier genes uncovers a Presenilin-2/beta-amyloid-actin genetic risk module shared among alpha-synucleinopathies

Whether neurodegenerative diseases linked to misfolding of the same protein share genetic risk drivers or whether different protein-aggregation pathologies in neurodegeneration are mechanistically related remains uncertain. Conventional genetic analyses are underpowered to address these questions. Through careful selection of patients based on protein aggregation phenotype (rather than clinical diagnosis) we can increase statistical power to detect associated variants in a targeted set of genes that modify proteotoxicities. Genetic modifiers of alpha-synuclein (ɑS) and beta-amyloid (Aβ) cytotoxicity in yeast are enriched in risk factors for Parkinson's disease (PD) and Alzheimer's disease (AD), respectively. Here, along with known AD/PD risk genes, we deeply sequenced exomes of 430 ɑS/Aβ modifier genes in patients across alpha-synucleinopathies (PD, Lewy body dementia and multiple system atrophy). Beyond known PD genes GBA1 and LRRK2, rare variants AD genes (CD33, CR1 and PSEN2) and Aβ toxicity modifiers involved in RhoA/actin cytoskeleton regulation (ARGHEF1, ARHGEF28, MICAL3, PASK, PKN2, PSEN2) were shared risk factors across synucleinopathies. Actin pathology occurred in iPSC synucleinopathy models and RhoA downregulation exacerbated ɑS pathology. Even in sporadic PD, the expression of these genes was altered across CNS cell types. Genome-wide CRISPR screens revealed the essentiality of PSEN2 in both human cortical and dopaminergic neurons, and PSEN2 mutation carriers exhibited diffuse brainstem and cortical synucleinopathy independent of AD pathology. PSEN2 contributes to a common-risk signal in PD GWAS and regulates ɑS expression in neurons. Our results identify convergent mechanisms across synucleinopathies, some shared with AD.

Defined co-cultures of glutamatergic and GABAergic neurons with a mutation in DISC1 reveal aberrant phenotypes in GABAergic neurons

BACKGROUND

Mutations in the gene DISC1 are associated with increased risk for schizophrenia, bipolar disorder and major depression. The study of mutated DISC1 represents a well-known and comprehensively characterized approach to understand neuropsychiatric disease mechanisms. However, previous studies have mainly used animal models or rather heterogeneous populations of iPSC-derived neurons, generated by undirected differentiation, to study the effects of DISC1 disruption. Since major hypotheses to explain neurodevelopmental, psychiatric disorders rely on altered neuronal connectivity observed in patients, an ideal iPSC-based model requires accurate representation of the structure and complexity of neuronal circuitries. In this study, we made use of an isogenic cell line with a mutation in DISC1 to study neuronal synaptic phenotypes in a culture system comprising a defined ratio of NGN2 and ASCL1/DLX2 (AD2)-transduced neurons, enriched for glutamatergic and GABAergic neurons, respectively, to mimic properties of the cortical microcircuitry.

RESULTS

In heterozygous DISC1 mutant neurons, we replicated the expected phenotypes including altered neural progenitor proliferation as well as neurite outgrowth, deregulated DISC1-associated signaling pathways, and reduced synaptic densities in cultures composed of glutamatergic neurons. Cultures comprising a defined ratio of NGN2 and AD2 neurons then revealed considerably increased GABAergic synapse densities, which have not been observed in any iPSC-derived model so far. Increased inhibitory synapse densities could be associated with an increased efficiency of GABAergic differentiation, which we observed in AD2-transduced cultures of mutant neurons. Additionally, we found increased neuronal activity in GABAergic neurons through calcium imaging while the activity pattern of glutamatergic neurons remained unchanged.

CONCLUSIONS

In conclusion, our results demonstrate phenotypic differences in a co-culture comprising a defined ratio of DISC1 mutant NGN2 and AD2 neurons, as compared to culture models comprising only one neuronal cell type. Altered synapse numbers and neuronal activity imply that DISC1 impacts the excitatory/inhibitory balance in NGN2/AD2 co-cultures, mainly through increased GABAergic input.

Aggregation of Disrupted in Schizophrenia 1 arises from a central region of the protein

An emerging approach to studying major mental illness is through proteostasis, with the identification of several proteins that form insoluble aggregates in the brains of patients. One of these is Disrupted in Schizophrenia 1 (DISC1), a neurodevelopmentally-important scaffold protein, and product of a classic schizophrenia risk gene. DISC1 aggregates have been detected in post mortem brain tissue from patients with schizophrenia, bipolar disorder and major depressive disorder, as well as various model systems, although the mechanism by which it aggregates is still unclear. Aggregation of two other proteins implicated in mental illness, TRIOBP-1 and NPAS3, was shown to be dependent on very specific structural regions of the protein. We therefore looked at the domain structure of DISC1, and investigated which structural elements are key for its aggregation. While none of the known structured DISC1 regions (named D, I, S and C respectively) formed aggregates individually when expressed in neuroblastoma cells, the combination of the D and I regions, plus the linker region between them, formed visible aggregates. Further refinement revealed that a region of approximately 30 amino acids between these two regions is critical for aggregation, and deletion of this region is sufficient to abolish the aggregation propensity of DISC1. This finding from mammalian cell culture contrasts with the recent determination that the C-region of DISC1 can aggregate in vitro, although some variations of the C-terminal of DISC1 could aggregate in our system. It therefore appears likely that DISC1 aggregation, implicated in mental illness, can occur through at least two distinct mechanisms.

Genetics of human brain development

Brain development in humans is achieved through precise spatiotemporal genetic control, the mechanisms of which remain largely elusive. Recently, integration of technological advances in human stem cell-based modelling with genome editing has emerged as a powerful platform to establish causative links between genotypes and phenotypes directly in the human system. Here, we review our current knowledge of complex genetic regulation of each key step of human brain development through the lens of evolutionary specialization and neurodevelopmental disorders and highlight the use of human stem cell-derived 2D cultures and 3D brain organoids to investigate human-enriched features and disease mechanisms. We also discuss opportunities and challenges of integrating new technologies to reveal the genetic architecture of human brain development and disorders.

Evidence of DISC1 as an arsenic binding protein and implications regarding its role as a translational activator

Disrupted-in-schizophrenia-1 (DISC1) is a scaffolding protein that plays a pivotal role in orchestrating signaling pathways involved in neurodevelopment, neural migration, and synaptogenesis. Among those, it has recently been reported that the role of DISC1 in the Akt/mTOR pathway can shift from a global translational repressor to a translational activator in response to oxidative stress induced by arsenic. In this study we provide evidence that DISC1 can directly bind arsenic via a C-terminal cysteine motif (C-X-C-X-C). A series of fluorescence-based binding assays were conducted with a truncated C-terminal domain construct of DISC1 and a series of single, double, and triple cysteine mutants. We found that arsenous acid, a trivalent arsenic derivative, specifically binds to the C-terminal cysteine motif of DISC1 with low micromolar affinity. All three cysteines of the motif are required for high-affinity binding. Electron microscopy experiments combined with in silico structural predictions reveal that the C-terminal of DISC1 forms an elongated tetrameric complex. The cysteine motif is consistently predicted to be located within a loop, fully exposed to solvent, providing a simple molecular framework to explain the high-affinity of DISC1 toward arsenous acid. This study sheds light on a novel functional facet of DISC1 as an arsenic binding protein and highlights its potential role as both a sensor and translational modulator within Akt/mTOR pathway.

ATF4 Transcriptionally Activates SHH to Promote Proliferation, Invasion, and Migration of Gastric Cancer Cells

Activating transcription factor 4 (ATF4) is a DNA-binding protein widely generated in mammals, which has two biological characteristics that bind the cAMP response element (CRE). The mechanism of ATF4 as a transcription factor in gastric cancer affecting the Hedgehog pathway remains unclear. Here, we observed that ATF4 was markedly upregulated in gastric cancer (GC) using immunohistochemistry and Western blotting assays in 80 paraffin-embedded GC samples and 4 fresh samples and para-cancerous tissues. ATF4 knockdown using lentiviral vectors strongly inhibited the proliferation and invasion of GC cells. ATF4 upregulation using lentiviral vectors promoted the proliferation and invasion of GC cells. We predicted that the transcription factor ATF4 is bound to the SHH promoter via the JASPA database. Transcription factor ATF4 is bound to the promoter region of SHH to activate the Sonic Hedgehog pathway. Mechanistically, rescue assays showed that ATF4 regulated gastric cancer cells' proliferation and invasive ability through SHH. Similarly, ATF4 enhanced the tumor formation of GC cells in a xenograft model.

Modeling common and rare genetic risk factors of neuropsychiatric disorders in human induced pluripotent stem cells

Recent genome-wide association studies (GWAS) and whole-exome sequencing of neuropsychiatric disorders, especially schizophrenia, have identified a plethora of common and rare disease risk variants/genes. Translating the mounting human genetic discoveries into novel disease biology and more tailored clinical treatments is tied to our ability to causally connect genetic risk variants to molecular and cellular phenotypes. When combined with the Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR)/CRISPR-associated (Cas) nuclease-mediated genome editing system, human induced pluripotent stem cell (hiPSC)-derived neural cultures (both 2D and 3D organoids) provide a promising tractable cellular model for bridging the gap between genetic findings and disease biology. In this review, we first conceptualize the advances in understanding the disease polygenicity and convergence from the past decade of iPSC modeling of different types of genetic risk factors of neuropsychiatric disorders. We then discuss the major cell types and cellular phenotypes that are most relevant to neuropsychiatric disorders in iPSC modeling. Finally, we critically review the limitations of iPSC modeling of neuropsychiatric disorders and outline the need for implementing and developing novel methods to scale up the number of iPSC lines and disease risk variants in a systematic manner. Sufficiently scaled-up iPSC modeling and a better functional interpretation of genetic risk variants, in combination with cutting-edge CRISPR/Cas9 gene editing and single-cell multi-omics methods, will enable the field to identify the specific and convergent molecular and cellular phenotypes in precision for neuropsychiatric disorders.

Conformational heterogeneity coupled with β-fibril formation of a scaffold protein involved in chronic mental illnesses

Chronic mental illnesses (CMIs) pose a significant challenge to global health due to their complex and poorly understood etiologies and hence, absence of causal therapies. Research of the past two decades has revealed dysfunction of the disrupted in schizophrenia 1 (DISC1) protein as a predisposing factor involved in several psychiatric disorders. DISC1 is a multifaceted protein that serves myriads of functions in mammalian cells, for instance, influencing neuronal development and synapse maintenance. It serves as a scaffold hub forming complexes with a variety (~300) of partners that constitute its interactome. Herein, using combinations of structural and biophysical tools, we demonstrate that the C-region of the DISC1 protein is highly polymorphic, with important consequences for its physiological role. Results from solid-state NMR spectroscopy and electron microscopy indicate that the protein not only forms symmetric oligomers but also gives rise to fibrils closely resembling those found in certain established amyloid proteinopathies. Furthermore, its aggregation as studied by isothermal titration calorimetry (ITC) is an exergonic process, involving a negative enthalpy change that drives the formation of oligomeric (presumably tetrameric) species as well as β-fibrils. We have been able to narrow down the β-core region participating in fibrillization to residues 716-761 of full-length human DISC1. This region is absent in the DISC1^Δ22aa splice variant, resulting in reduced association with proteins from the dynein motor complex, viz., NDE-like 1 (NDEL1) and lissencephaly 1 (LIS1), which are crucial during mitosis. By employing surface plasmon resonance, we show that the oligomeric DISC1 C-region has an increased affinity and shows cooperativity in binding to LIS1 and NDEL1, in contrast to the noncooperative binding mode exhibited by the monomeric version. Based on the derived structural models, we propose that the association between the binding partners involves two neighboring subunits of DISC1 C-region oligomers. Altogether, our findings highlight the significance of the DISC1 C-region as a crucial factor governing the balance between its physiological role as a multifunctional scaffold protein and aggregation-related aberrations with potential significance for disease.

High Expression of PAMR1 Predicts Favorable Prognosis and Inhibits Proliferation, Invasion, and Migration in Cervical Cancer

Peptidase domain containing associated with muscle regeneration 1 (PAMR1) is frequently lost in breast cancer samples and is considered as a tumor suppressor. The roles and mechanisms of PAMR1 in other types of cancers are still unclear. In our present study, we identified PAMR1 as an invasion-related regulator in cervical cancer. Public database and immunohistochemical (IHC) analysis showed that the expression level of PAMR1 in cervical cancer tissues was lower than that in normal cervix tissues and was negatively related to clinicopathologic features. The high expression of PAMR1 also predicted a better prognosis of cervical cancer patients. CCK8, Transwell, and wound-healing assays demonstrated that knockdown of PAMR1 facilitated the proliferation, migration, and invasion of cervical cancer cells. Additionally, gene set enrichment analysis (GSEA) showed a variety of cancer-related pathways potentially activated or suppressed by PAMR1. Moreover, we verified that PAMR1 inhibited MYC target and mTORC1 signaling pathways. In conclusion, our study revealed the suppressor role of PAMR1 in cervical cancer, providing a new insight into the molecular mechanism of cervical cancer progression.

Extending the Horizon of Homology Detection with Coevolution-based Structure Prediction

Traditional sequence analysis algorithms fail to identify distant homologies when they lie beyond a detection horizon. In this review, we discuss how co-evolution-based contact and distance prediction methods are pushing back this homology detection horizon, thereby yielding new functional insights and experimentally testable hypotheses. Based on correlated substitutions, these methods divine three-dimensional constraints among amino acids in protein sequences that were previously devoid of all annotated domains and repeats. The new algorithms discern hidden structure in an otherwise featureless sequence landscape. Their revelatory impact promises to be as profound as the use, by archaeologists, of ground-penetrating radar to discern long-hidden, subterranean structures. As examples of this, we describe how triplicated structures reflecting longin domains in MON1A-like proteins, or UVR-like repeats in DISC1, emerge from their predicted contact and distance maps. These methods also help to resolve structures that do not conform to a "beads-on-a-string" model of protein domains. In one such example, we describe CFAP298 whose ubiquitin-like domain was previously challenging to perceive owing to a large sequence insertion within it. More generally, the new algorithms permit an easier appreciation of domain families and folds whose evolution involved structural insertion or rearrangement. As we exemplify with α1-antitrypsin, coevolution-based predicted contacts may also yield insights into protein dynamics and conformational change. This new combination of structure prediction (using innovative co-evolution based methods) and homology inference (using more traditional sequence analysis approaches) shows great promise for bringing into view a sea of evolutionary relationships that had hitherto lain far beyond the horizon of homology detection.

Generation of hypothalamic arcuate organoids from human induced pluripotent stem cells

Human brain organoids represent remarkable platforms for recapitulating features of human brain development and diseases. Existing organoid models do not resolve fine brain subregions, such as different nuclei in the hypothalamus. We report the generation of arcuate organoids (ARCOs) from human induced pluripotent stem cells (iPSCs) to model the development of the human hypothalamic arcuate nucleus. Single-cell RNA sequencing of ARCOs revealed significant molecular heterogeneity underlying different arcuate cell types, and machine learning-aided analysis based on the neonatal human hypothalamus single-nucleus transcriptome further showed a human arcuate nucleus molecular signature. We also explored ARCOs generated from Prader-Willi syndrome (PWS) patient iPSCs. These organoids exhibit aberrant differentiation and transcriptomic dysregulation similar to postnatal hypothalamus of PWS patients, indicative of cellular differentiation deficits and exacerbated inflammatory responses. Thus, patient iPSC-derived ARCOs represent a promising experimental model for investigating nucleus-specific features and disease-relevant mechanisms during early human arcuate development.

LncRNA-AC006129.1 reactivates a SOCS3-mediated anti-inflammatory response through DNA methylation-mediated CIC downregulation in schizophrenia

Schizophrenia is a complex genetic disorder, the non-Mendelian features of which are likely complicated by epigenetic factors yet to be elucidated. Here, we performed RNA sequencing of peripheral blood RNA from monozygotic twins discordant for schizophrenia, and identified a schizophrenia-associated upregulated long noncoding RNA (lncRNA, AC006129.1) that participates in the inflammatory response by enhancing SOCS3 and CASP1 expression in schizophrenia patients and further validated this finding in AC006129.1-overexpressing mice showing schizophrenia-related abnormal behaviors. We find that AC006129.1 binds to the promoter region of the transcriptional repressor Capicua (CIC), facilitates the interactions of DNA methyltransferases with the CIC promoter, and promotes DNA methylation-mediated CIC downregulation, thereby ameliorating CIC-induced SOCS3 and CASP1 repression. Derepression of SOCS3 enhances the anti-inflammatory response by inhibiting JAK/STAT-signaling activation. Our findings reveal an epigenetic mechanism with etiological and therapeutic implications for schizophrenia.

Making Sense of Patient-Derived iPSCs, Transdifferentiated Neurons, Olfactory Neuronal Cells, and Cerebral Organoids as Models for Psychiatric Disorders

The improvement of experimental models for disorders requires a constant approximation towards the dysregulated tissue. In psychiatry, where an impairment of neuronal structure and function is assumed to play a major role in disease mechanisms and symptom development, this approximation is an ongoing process implicating various fields. These include genetic, animal, and post-mortem studies. To test hypotheses generated through these studies, in vitro models using non-neuronal cells such as fibroblasts and lymphocytes have been developed. For brain network disorders, cells with neuronal signatures would, however, represent a more adequate tissue. Considering the limited accessibility of brain tissue, research has thus turned towards neurons generated from induced pluripotent stem cells as well as directly induced neurons, cerebral organoids, and olfactory neuroepithelium. Regarding the increasing importance and amount of research using these neuronal cells, this review aims to provide an overview of all these models to make sense of the current literature. The development of each model system and its use as a model for the various psychiatric disorder categories will be laid out. Also, advantages and limitations of each model will be discussed, including a reflection on implications and future perspectives.

Sex-Specific Cannabidiol- and Iloperidone-Induced Neuronal Activity Changes in an In Vitro MAM Model System of Schizophrenia

Cortical circuit dysfunction is thought to be an underlying mechanism of schizophrenia (SZ) pathophysiology with normalization of aberrant circuit activity proposed as a biomarker for antipsychotic efficacy. Cannabidiol (CBD) shows potential as an adjunctive antipsychotic therapy; however, potential sex effects in these drug interactions remain unknown. In the present study, we sought to elucidate sex effects of CBD coadministration with the atypical antipsychotic iloperidone (ILO) on the activity of primary cortical neuron cultures derived from the rat methylazoxymethanol acetate (MAM) model used for the study of SZ. Spontaneous network activity measurements were obtained using a multielectrode array at baseline and following administration of CBD or ILO alone, or combined. At baseline, MAM male neurons displayed increased bursting activity whereas MAM female neurons exhibited no difference in bursting activity compared to sex-matched controls. CBD administered alone showed a rapid but transient increase in neuronal activity in the MAM networks, an effect more pronounced in females. Furthermore, ILO had an additive effect on CBD-induced elevations in activity in the MAM male neurons. In the MAM female neurons, CBD or ILO administration resulted in time-dependent elevations in neuronal activity, but the short-term CBD-induced increases in activity were lost when CBD and ILO were combined. Our findings indicate that CBD induces rapid increases in cortical neuronal activity, with sex-specific drug interactions upon ILO coadministration. This suggests that sex should be a consideration when implementing adjunct therapy for treatment of SZ.

Applying stem cells and CRISPR engineering to uncover the etiology of schizophrenia

Schizophrenia is a highly heritable, polygenic disorder. A growing list of common genetic variants have been associated with schizophrenia; there is a clear need to understand the role of these risk factors in the etiology of disease. The majority of these variants occur in noncoding regions of the genome and are thought to regulate the expression of one or more genes in a cell type-specific fashion. Recent advances in stem cell biology and molecular genetics have resulted in two invaluable advances: hiPSC technology makes possible the generation of donor-specific disease-relevant neural cell types, whereas CRISPR-based techniques can be applied to manipulate individual variants and/or their gene targets. New multiplexed gene manipulation and CRISPR screening techniques show great promise toward dissecting the complex interactions between the myriad disease-associated variants. This review outlines key advances in hiPSC and CRISPR technology, describing their applications and future potential in the field of schizophrenia research.

Pharmacological rescue in patient iPSC and mouse models with a rare DISC1 mutation

We previously identified a causal link between a rare patient mutation in DISC1 (disrupted-in-schizophrenia 1) and synaptic deficits in cortical neurons differentiated from isogenic patient-derived induced pluripotent stem cells (iPSCs). Here we find that transcripts related to phosphodiesterase 4 (PDE4) signaling are significantly elevated in human cortical neurons differentiated from iPSCs with the DISC1 mutation and that inhibition of PDE4 or activation of the cAMP signaling pathway functionally rescues synaptic deficits. We further generated a knock-in mouse line harboring the same patient mutation in the Disc1 gene. Heterozygous Disc1 mutant mice exhibit elevated levels of PDE4s and synaptic abnormalities in the brain, and social and cognitive behavioral deficits. Pharmacological inhibition of the PDE4 signaling pathway rescues these synaptic, social and cognitive behavioral abnormalities. Our study shows that patient-derived isogenic iPSC and humanized mouse disease models are integral and complementary for translational studies with a better understanding of underlying molecular mechanisms.

Negative Symptoms of Schizophrenia and Dopaminergic Transmission: Translational Models and Perspectives Opened by iPSC Techniques

Negative symptoms (NS) represent a heterogeneous dimension of schizophrenia (SCZ), associated with a poor functional outcome. A dysregulated dopamine (DA) system, including a reduced D1 receptor activation in the prefrontal cortex, DA hypoactivity in the caudate and alterations in D3 receptor activity, seems to contribute to the pathogenesis of NS. However, failure to take into account the NS heterogeneity has slowed down progress in research on their neurobiological correlates and discoveries of new effective treatments. A better neurobiological characterization of NS is needed, and this requires objective quantification of their features that can be applied in translational models, such as animal models and human inducible pluripotent stem cells (iPSC). In this review we summarize the evidence for dopaminergic alterations relevant to NS in translational animal models focusing on dysfunctional motivation, a core aspect of NS. Among others, experiments on mutant rodents with an overexpression of DA D2 or D3 receptors and the dopamine deficient mice are discussed. In the second part we summarize the findings from recent studies using iPSC to model the pathogenesis of SCZ. By retaining the genetic background of risk genetic variants, iPSC offer the possibility to study the effect of de novo mutations or inherited polymorphisms from subgroups of patients and their response to drugs, adding an important tool for personalized psychiatry. Given the key role of DA in NS, we focus on findings of iPSC-derived DA neurons. Since implementation of iPSC-derived neurons to study the neurobiology of SCZ is a relatively recent acquisition, the available data are limited. We highlight some methodological aspects of relevance in the interpretation of in vitro testing results, including limitations and strengths, offering a critical viewpoint for the implementation of future pharmacological studies aimed to the discovery and characterization of novel treatments for NS.

Focus on Causality in ESC/iPSC-Based Modeling of Psychiatric Disorders

Genome-wide association studies (GWAS) have identified an increasing number of genetic variants that significantly associate with psychiatric disorders. Despite this wealth of information, our knowledge of which variants causally contribute to disease, how they interact, and even more so of the functions they regulate, is still poor. The availability of embryonic stem cells (ESCs) and the advent of patient-specific induced pluripotent stem cells (iPSCs) has opened new opportunities to investigate genetic risk variants in living disease-relevant cells. Here, we analyze how this progress has contributed to the analysis of causal relationships between genetic risk variants and neuronal phenotypes, especially in schizophrenia (SCZ) and bipolar disorder (BD). Studies on rare, highly penetrant risk variants have originally led the field, until more recently when the development of (epi-) genetic editing techniques spurred studies on cause-effect relationships between common low risk variants and their associated neuronal phenotypes. This reorientation not only offers new insights, but also raises issues on interpretability. Concluding, we consider potential caveats and upcoming developments in the field of ESC/iPSC-based modeling of causality in psychiatric disorders.

Invited Review: Epigenetics in neurodevelopment

Neural development requires the orchestration of dynamic changes in gene expression to regulate cell fate decisions. This regulation is heavily influenced by epigenetics, heritable changes in gene expression not directly explained by genomic information alone. An understanding of the complexity of epigenetic regulation is rapidly emerging through the development of novel technologies that can assay various features of epigenetics and gene regulation. Here, we provide a broad overview of several commonly investigated modes of epigenetic regulation, including DNA methylation, histone modifications, noncoding RNAs, as well as epitranscriptomics that describe modifications of RNA, in neurodevelopment and diseases. Rather than functioning in isolation, it is being increasingly appreciated that these various modes of gene regulation are dynamically interactive and coordinate the complex nature of neurodevelopment along multiple axes. Future work investigating these interactions will likely utilize 'multi-omic' strategies that assay cell fate dynamics in a high-dimensional and high-throughput fashion. Novel human neurodevelopmental models including iPSC and cerebral organoid systems may provide further insight into human-specific features of neurodevelopment and diseases.

Disorder Mediated Oligomerization of DISC1 Proteins Revealed by Coarse-Grained Molecular Dynamics Simulations

Disrupted-in-schizophrenia-1 (DISC1) is a scaffold protein of significant importance for neuro-development and a prominent candidate protein in the etiology of mental disorders. In this work, we investigate the role of conformational heterogeneity and local structural disorder in the oligomerization pathway of the full-length DISC1 and of two truncation variants. Through extensive coarse-grained molecular dynamics simulations with a predictive energy landscape-based model, we shed light on the interplay of local and global disorder which lead to different oligomerization pathways. We found that both global conformational heterogeneity and local structural disorder play an important role in shaping distinct oligomerization trends of DISC1. This study also sheds light on the differences in oligomerization pathways of the full-length protein compared to the truncated variants produced by a chromosomal translocation associated with schizophrenia. We report that oligomerization of full-length DISC1 sequence works in a nonadditive manner with respect to truncated fragments that do not mirror the conformational landscape or binding affinities of the full-length unit.