Deep proteomics identifies shared molecular pathway alterations in synapses of patients with schizophrenia and bipolar disorder and mouse model

Recent Advances in Schizophrenia Genomics and Emerging Clinical Implications

The conceptualization of schizophrenia has evolved from Emil Kraepelin's identification of "dementia praecox" as a distinct illness characterized by cognitive and functional deficits to the modern understanding of its complex nature. Recent research, including the "deficit syndrome," highlights enduring negative symptoms that correlate with poor functional outcomes. Genetic epidemiologic studies reveal a strong heritable basis (60%-80%) for schizophrenia, with its polygenic architecture overlapping with various mental health disorders. This complexity raises questions about targeted precision medicine. Recent advancements in biobanks and neurogenomics research are providing valuable insights that aim to improve patient outcomes through enhanced genomic understanding.

Schizophrenia-Related Synaptic Dysfunction and Abnormal Sensorimotor Gating in Akap11-Deficient Mice

BACKGROUND AND HYPOTHESIS

Large-scale whole exome sequencing (WES) analyses have implicated rare protein-truncating variants (PTVs) in the AKAP11 gene contributing to schizophrenia risk. Previous studies reported alterations of EEG characteristics and synaptic proteome in Akap11 mutant mice. We hypothesize that synaptic dysfunction contributes to AKAP11 deficiency in the pathogenesis of schizophrenia.

STUDY DESIGN

We generated an Akap11 knockout mouse and employed a series of behavioral evaluations, neuronal sparse labeling assays, electron microscopy, and immunoprecipitation mass spectrometry (IP-MS) to elucidate the impacts of Akap11 on schizophrenia-relevant phenotypes.

STUDY RESULTS

Our behavioral paradigm evaluations revealed that Akap11 deficient mice exhibited impaired prepulse inhibition and anxiety-like behaviors compared with their wild-type littermates. Neuronal sparse labeling assays indicated a significant reduction in the density of total and thin spines in Akap11 deficient mice, and ultrastructural analysis via electron microscopy disclosed marked alterations in synaptogenesis after suppressing Akap11, including the reduced density of typical synapses, synaptic vesicle density, and postsynaptic density (PSD) length. IP-MS identified 222 high-confidence interaction proteins of Akap11, encompassing synapses-related proteins (eg, Exoc4, Ncam1, Picalm, Vapb) and actin-related proteins (Actb, Diaph1), and enrichment analyses further showed that Akap11 may contribute to RNA splicing, extracellular matrix organization, axon guidance, post-NMDA receptor activation events, GPER1 signaling and PKA activation pathways.

CONCLUSIONS

Together, these findings delineated the synaptic and behavioral phenotypes in Akap11 deficient mice, shedding light on the potential mechanisms underlying the role of rare PTVs in schizophrenia and substantiating the significance of AKAP11 as a risk gene for this illness.

Transcriptomic and epigenomic consequences of heterozygous loss-of-function mutations in AKAP11, a shared risk gene for bipolar disorder and schizophrenia

The gene A-kinase anchoring protein 11 (AKAP11) recently emerged as a shared risk factor between bipolar disorder and schizophrenia, driven by large-effect loss-of-function (LoF) variants. Recent research has uncovered the neurophysiological characteristics and synapse proteomics profile of Akap11-mutant mouse models. Considering the role of AKAP11 in binding cAMP-dependent protein kinase A (PKA) and mediating phosphorylation of numerous substrates, such as transcription factors and epigenetic regulators, and given that chromatin alterations have been implicated in the brains of patients with bipolar disorder and schizophrenia, it is crucial to uncover the transcriptomic and chromatin dysregulations following the heterozygous knockout of AKAP11, particularly in human neurons. This study uses genome-wide approaches to investigate such aberrations in human induced pluripotent stem cell (iPSC)-derived neurons. We show the impact of heterozygous AKAP11 LoF mutations on the gene expression landscape and profile the DNA methylation and histone acetylation modifications. Altogether we highlight the involvement of aberrant activity of intergenic and intronic enhancers, which are enriched in PBX homeobox 2 (PBX2) and Nuclear Factor-1 (NF1) known binding motifs, respectively, in transcription dysregulations of genes mainly involved in DNA-binding transcription factor activity, actin binding and cytoskeleton regulation, and cytokine receptor binding. We also show significant downregulation of pathways related to ribosome structure and function, a pathway also altered in BD and SCZ post-mortem brain tissues and heterozygous Akap11-KO mice synapse proteomics. A better understanding of the dysregulations resulting from haploinsufficiency in AKAP11 improves our knowledge of the biological roots and pathophysiology of BD and SCZ, paving the way for better therapeutic approaches.

Hippocampal transcriptome analysis in ClockΔ19 mice identifies pathways associated with glial cell differentiation and myelination

BACKGROUND

ClockΔ19 mice demonstrate behavioral characteristics and neurobiological changes that closely resemble those observed in bipolar disorder (BD). Notably, abnormalities in the hippocampus have been observed in patients with BD, yet direct molecular investigation of human hippocampal tissue remains challenging due to its limited accessibility.

METHODS

To model BD, ClockΔ19 mice were employed. Weighted gene co-expression network analysis (WGCNA) was utilized to identify mutation-related modules, and changes in cell populations were determined using the computational deconvolution CIBERSORTx. Furthermore, GeneMANIA and protein-protein interactions (PPIs) were leveraged to construct a comprehensive interaction network.

RESULTS

174 differentially expressed genes (DEGs) were identified, revealing abnormalities in rhythmic processes, mitochondrial metabolism, and various cell functions including morphology, differentiation, and receptor activity. Analysis identified 5 modules correlated with the mutation, with functional enrichment highlighting disturbances in rhythmic processes and neural cell differentiation due to the mutation. Furthermore, a decrease in neural stem cells (NSC), and an increase in astrocyte-restricted precursors (ARP), ependymocytes (EPC), and hemoglobin-expressing vascular cells (Hb-VC) in the mutant mice were observed. A network comprising 12 genes that link rhythmic processes to neural cell differentiation in the hippocampus was also identified.

LIMITATIONS

This study focused on the hippocampus of mice, hence the applicability of these findings to human patients warrants further exploration.

CONCLUSION

The ClockΔ19 mutation may disrupt circadian rhythm, myelination, and the differentiation of neural stem cells (NSCs) into glial cells. These abnormalities are linked to altered expression of key genes, including DPB, CIART, NR1D1, GFAP, SLC20A2, and KL. Furthermore, interactions between SLC20A2 and KL might provide a connection between circadian rhythm regulation and cell type transitions.

Autophagosomes anchor an AKAP11-dependent regulatory checkpoint that shapes neuronal PKA signaling

Protein Kinase A (PKA) is regulated spatially and temporally via scaffolding of its catalytic (Cα) and regulatory (RI/RII) subunits by the A-kinase-anchoring proteins (AKAP). By binding to an AKAP11 scaffold, PKA engages in poorly understood interactions with autophagy, a key degradation pathway for neuronal cell homeostasis. Mutations in AKAP11 promote schizophrenia and bipolar disorders (SZ-BP) through unknown mechanisms. Here, through proteomic-based analyses of immunopurified lysosomes, we identify the Cα-RIα-AKAP11 holocomplex as a prominent autophagy-associated protein-kinase complex. AKAP11 scaffolds Cα-RIα interaction with the autophagic machinery via its LC3-interacting region (LIR), enabling both PKA regulation by upstream signals, and its autophagy-dependent degradation. We identify Ser83 on the RIα linker-hinge region as an AKAP11-dependent phospho-residue that modulates RIα-Cα binding to the autophagosome and cAMP-induced PKA activation. Decoupling AKAP11-PKA from autophagy alters downstream phosphorylation events, supporting an autophagy-dependent checkpoint for PKA signaling. Ablating AKAP11 in induced pluripotent stem cell-derived neurons reveals dysregulation of multiple pathways for neuronal homeostasis. Thus, the autophagosome is a platform that modulates PKA signaling, providing a possible mechanistic link to SZ/BP pathophysiology.

Identifying proteins and pathways associated with multimorbidity in 53,026 adults

BACKGROUND AND AIMS

Multimorbidity, the coexistence of multiple chronic diseases, is a rapidly expanding global health challenge, carrying profound implications for patients, caregivers, healthcare systems, and society. Investigating the determinants and drivers underlying multiple chronic diseases is a priority for disease management and prevention.

METHOD

This prospective cohort study analyzed data from the 53,026 participants in the UK Biobank from baseline (2006 to 2010) across 13.3 years of follow-up. Using Cox proportional hazards regression model, we characterized shared and unique associations across 38 incident outcomes (31 chronic diseases, 6 system mortality and all-cause mortality). Furthermore, ordinal regression models were used to assess the association between protein levels and multimorbidity (0-1, 2, 3-4, or ≥ 5 chronic diseases). Functional and tissue enrichment analysis were employed for multimorbidity-associated proteins. The upstream regulators of above proteins were identified.

RESULTS

We demonstrated 972 (33.3 %) proteins were shared across at least two incident chronic diseases after Bonferroni correction (P < 3.42 × 10-7, 93.3 % of those had consistent effects directions), while 345 (11.8 %) proteins were uniquely linked to a single chronic disease. Remarkably, GDF15, PLAUR, WFDC2 and AREG were positively associated with 20-24 incident chronic diseases (hazards ratios: 1.21-3.77) and showed strong associations with multimorbidity (odds ratios: 1.33-1.89). We further identified that protein levels are explained by common risk factors, especially renal function, liver function, inflammation, and obesity, providing potential intervention targets. Pathway analysis has underscored the pivotal role of the immune response, with the top three transcription factors associated with proteomics being NFKB1, JUN and RELA.

CONCLUSIONS

Our results enhance the understanding of the biological basis underlying multimorbidity, offering biomarkers for disease identification and novel targets for therapeutic intervention.

Bipolar and schizophrenia risk gene AKAP11 encodes an autophagy receptor coupling the regulation of PKA kinase network homeostasis to synaptic transmission

Human genomic studies have identified protein-truncating variants in AKAP11 associated with both bipolar disorder and schizophrenia, implicating a shared disease mechanism driven by loss-of-function. AKAP11, a protein kinase A (PKA) adaptor, plays a key role in degrading the PKA-RI complex through selective autophagy. However, the neuronal functions of AKAP11 and the impact of its loss-of-function remains largely uncharacterized. Through multi-omics approaches, cell biology, and electrophysiology analysis in mouse models and human induced neurons, we delineated a central role of AKAP11 in coupling PKA kinase network regulation to synaptic transmission. Loss of AKAP11 disrupted PKA activity and impaired cellular functions that significantly overlap with pathways associated with the psychiatric disease. Moreover, we identified interactions between AKAP11, the PKA-RI adaptor SPHKAP, and the ER-resident autophagy-related proteins VAPA/B, which co-adapt and mediate PKA-RI degradation. Notably, AKAP11 deficiency impaired neurotransmission and decreased presynaptic protein levels in neurons, providing key insights into the mechanism underlying AKAP11-associated psychiatric diseases.

Mapping the Cerebrospinal Fluid Proteome in Bipolar Disorder

BACKGROUND

Bipolar disorder (BD) is a severe psychiatric condition with unclear etiology and no established biomarkers. Here, we aimed to characterize the cerebrospinal fluid (CSF) proteome in euthymic individuals with BD to identify potential protein biomarkers.

METHODS

We used nano-flow liquid chromatography coupled to high-resolution mass spectrometry to quantify over 2000 CSF proteins in 374 individuals from two independent clinical cohorts (n = 164 cases + 89 controls and 66 cases + 55 controls, respectively). A subset of the cases was followed longitudinally and reexamined after a median of 6.5 years.

RESULTS

Differential abundance analysis revealed 41 proteins with robust case-control association in both cohorts. These included lower levels of synaptic proteins (e.g., APP, CLSTN1, NPTX2, NRXN1) and axon guidance and cell adhesion molecules (e.g., NEO1, NCAM1, SEMA7A) and higher levels of blood-brain barrier integrity proteins (e.g., VTN, SERPIN3) and complement components (e.g., C1RL, C3, C5). The findings were consistently driven by the BD type 1 subtype. Comparing BD type 1 participants with control participants increased discoverability, revealing 86 replicated associations despite a loss of statistical power. Moreover, longitudinal analyses of coexpression modules revealed dynamic changes in the CSF proteome composition that correlated with clinical outcomes, including disease severity, future manic episodes, and symptom improvement. Finally, we conducted association analyses of CSF proteins with genetic risk loci for BD and schizophrenia.

CONCLUSIONS

This study represents the first large-scale untargeted profiling of the CSF proteome in BD, unveiling potential biomarkers and providing in vivo support for altered synaptic and brain connectivity processes, impaired neurovascular integrity, and complement activation in the pathology of BD.

Brain 18FDG-PET pattern in cognitively impaired elderly patients with bipolar disorder

BACKGROUND

Patients with bipolar disorder (BD) are at increased risk of dementia. The underlying mechanisms are debated. FDG-PET elucidates glucose metabolic reductions due to altered neuronal activity in the cerebral cortex, allowing detection and identification of neurodegenerative processes. This study aims to investigate cerebral glucose metabolism in cognitively impaired elderly patients with BD using FDG-PET imaging, to elucidate potential underlying mechanisms and improve diagnostic accuracy.

METHODS

We conducted a retrospective analysis of FDG-PET scans from 32 cognitively impaired elderly patients with BD (mean age 70.4 years). These were compared with scans from 35 non-degenerative controls (NDC) and patients diagnosed with Alzheimer's disease (AD, n = 27), frontotemporal dementia (FTD, n = 26), and dementia with Lewy bodies (DLB, n = 18). Voxel-wise statistical analysis was performed using SPM software, adjusting for age and sex.

RESULTS

No significant cortical hypometabolism was found in patients with BD compared to NDC. In contrast, typical patterns of hypometabolism were observed in the AD, FTD, and DLB groups. The findings suggest that late-life cognitive impairment in patients with BD is not due to a single common neurodegenerative process.

CONCLUSION

The absence of abnormal cortical metabolism in cognitively impaired elderly patients with BD suggests that cognitive impairment in this population may not be driven by a common neurodegenerative pathway. Further studies using other biomarkers are needed to investigate the brain processes involved, which could lead to improved understanding and management of cognitive impairment in patients with BD.

Analyzing the potential of neuronal pentraxin 2 as a biomarker in neurological disorders: A literature review

Neuronal pentraxin 2 (NP2) plays a significant role in synaptic plasticity, neuronal survival, and excitatory synapse regulation. Emerging research suggests that NP2 is implicated in the pathogenesis of various neurological disorders, including neurodegenerative diseases, neuropsychiatric disorders, and neuropathies. This literature review extensively analyzes NP2's role in these conditions, thereby highlighting its contributions to synaptic dysfunction, neuroinflammation, and neurotoxic protein aggregation. In Alzheimer's and Parkinson's diseases, NP2 is linked to amyloid-beta aggregation and dopaminergic neuron degeneration, respectively. Additionally, altered NP2 expression is observed in schizophrenia and bipolar disorder, thus suggesting its involvement in synaptic dysfunction and neurotransmitter imbalance. In neuropathic pain and epilepsy, NP2 modulates the synaptic plasticity and inflammatory responses, with altered levels correlating with disease severity. Furthermore, NP2's involvement in amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD) emphasizes its broad impact on neuronal health. Understanding NP2's multifaceted roles may reveal novel therapeutic targets and improve the clinical outcomes for these neurological disorders. Though the precise role of NP2 remains uncertain, its clinical potential and initial findings justify further investigations into neuronal pentraxins and other related neuroproteins.

Calcium Signaling and Molecular Adhesion Processes May Hold the Key to Genetic Risk for Autism: A Molecular Pathway Analysis on Two Independent Samples

BACKGROUND

Autism spectrum disorder (ASD) is a neurodevelopmental disorder characterized by limited interests, difficulties in social interactions, repetitive behaviors, and impairments in social communication. ASD tends to run in families, and twin studies suggest a strong genetic basis for the disorder. However, the definition of a genetic profile that indicates a risk for ASD remains unclear.

METHODS

This analysis includes an investigation (Autism Dataset 4 from the NIMH repository, n = 2890) and a replication (Autism Dataset 3 from the NIMH repository, n = 1233) of trio samples with GWAS data. In Phase 1, a molecular pathway analysis is conducted on the investigation sample to test for the enrichment of specific Gene Ontology (GO) terms associated with autism. In Phase 2, the identified pathways are tested for enrichment in the replication sample. Permutation tests are performed to reduce the risk of false-positive findings. Quality assessment is conducted using QQ-plots and λ values, with Plink and R utilized for the Transmission Disequilibrium Test (TDT) and permutation tests.

RESULTS

The GO term GO:0007417 was found to be enriched in both the investigation and replication samples. SNPs associated with this pathway were observed at a frequency higher than expected in the replication sample.

CONCLUSIONS

The GO term GO:0007417 (development of the nervous system) was associated with autism in both trio samples. Variations in the genes TMPRSS4, TRPC4, and PCDH9 were consistently linked to autism across the two independent samples, highlighting the role of calcium signaling and cell adhesion molecules in the risk of autism-related disorders. The pathways and variations associated with autism are described in detail, which can contribute to the engineering of new pharmacological treatments for ASD.

Synaptic composition, activity, mRNA translation and dynamics in combined single-synapse profiling using multimodal imaging

The function of neuronal circuits, and its perturbation by psychoactive molecules or disease-associated genetic variants, is governed by the interplay between synapse activity and synaptic protein localization and synthesis across a heterogeneous synapse population. Here, we combine in situ measurement of synaptic multiprotein compositions and activation states, synapse activity in calcium traces or glutamate spiking, and local translation of specific genes, across the same individual synapses. We demonstrate how this high-dimensional data enables identification of interdependencies in the multiprotein-activity network, and causal dissection of complex synaptic phenotypes in disease-relevant chemical and genetic NMDAR loss of function that translate in vivo . We show how this method generalizes to other subcellular systems by deriving mitochondrial protein networks, and, using support vector machines, its value in overcoming animal variability in phenotyping. Integrating multiple synapse information modalities enables deep structure-function characterization of synapse populations and their responses to genetic and chemical perturbations.

Schizophrenia genomics: genetic complexity and functional insights

Determining the causes of schizophrenia has been a notoriously intractable problem, resistant to a multitude of investigative approaches over centuries. In recent decades, genomic studies have delivered hundreds of robust findings that implicate nearly 300 common genetic variants (via genome-wide association studies) and more than 20 rare variants (via whole-exome sequencing and copy number variant studies) as risk factors for schizophrenia. In parallel, functional genomic and neurobiological studies have provided exceptionally detailed information about the cellular composition of the brain and its interconnections in neurotypical individuals and, increasingly, in those with schizophrenia. Taken together, these results suggest unexpected complexity in the mechanisms that drive schizophrenia, pointing to the involvement of ensembles of genes (polygenicity) rather than single-gene causation. In this Review, we describe what we now know about the genetics of schizophrenia and consider the neurobiological implications of this information.

Autophagosomes coordinate an AKAP11-dependent regulatory checkpoint that shapes neuronal PKA signaling

Protein Kinase A (PKA) is regulated spatially and temporally via scaffolding of its catalytic (Cα/β) and regulatory (RI/RII) subunits by the A-kinase-anchoring proteins (AKAP). PKA engages in poorly understood interactions with autophagy, a key degradation pathway for neuronal cell homeostasis, partly via its AKAP11 scaffold. Mutations in AKAP11 drive schizophrenia and bipolar disorders (SZ-BP) through unknown mechanisms. Through proteomic-based analysis of immunopurified lysosomes, we identify the Cα-RIα-AKAP11 holocomplex as a prominent autophagy-associated protein kinase complex. AKAP11 scaffolds Cα-RIα to the autophagic machinery via its LC3-interacting region (LIR), enabling both PKA regulation by upstream signals, and its autophagy-dependent degradation. We identify Ser83 on the RIα linker-hinge region as an AKAP11-dependent phospho-residue that modulates RIα-Cα binding and cAMP-induced PKA activation. Decoupling AKAP11-PKA from autophagy alters Ser83 phosphorylation, supporting an autophagy-dependent checkpoint for PKA signaling. Ablating AKAP11 in induced pluripotent stem cell-derived neurons reveals dysregulation of multiple pathways for neuronal homeostasis. Thus, the autophagosome is a novel platform that modulate PKA signaling, providing a possible mechanistic link to SZ/BP pathophysiology.

Uncovering novel drug targets for bipolar disorder: a Mendelian randomization analysis of brain, cerebrospinal fluid, and plasma proteomes

BACKGROUND

There is a clear demand for innovative therapeutics for bipolar disorder (BD).

METHODS

We integrated the largest BD genome-wide association study (GWAS) dataset (NCase = 41 917, NControl = 371 549) with protein quantitative trait loci from brain, cerebrospinal fluid, and plasma. Using a range of integrative analyses, including Mendelian randomization (MR), Steiger filter analysis, Bayesian colocalization, and phenome-wide MR analysis, we prioritized novel drug targets for BD. Additionally, we incorporated data from the UK Biobank (NCase = 1064, NControl = 365 476) and the FinnGen study (NCase = 7006, NControl = 329 192) for robust biological validation.

RESULTS

Through MR analysis, we found that in the brain, downregulation of DNM3, MCTP1, ABCB8 and elevation of DFNA5 and PDF were risk factors for BD. In cerebrospinal fluid, increased BD risk was associated with increased levels of FRZB, AGRP, and IL36A and decreased CTSF and LRP8. Plasma analysis revealed that decreased LMAN2L, CX3CL1, PI3, NCAM1, and TIMP4 correlated with increased BD risk, but ITIH1 did not. All these proteins passed Steiger filtering, and Bayesian colocalization confirmed that 12 proteins were colocalized with BD. Phenome-wide MR analysis revealed no significant side effects for potential drug targets, except for LRP8. External validation further underscored the concordance between the primary and validation cohorts, confirming MCTP1, DNM3, PDF, CTSF, AGRP, FRZB, LMAN2L, NCAM1, and TIMP4 are intriguing targets for BD.

CONCLUSIONS

Our study identified druggable proteins for BD, including MCTP1, DNM3, and PDF in the brain; CTSF, AGRP, and FRZB in cerebrospinal fluid; and LMAN2L, NCAM1, and TIMP4 in plasma, delineating promising avenues to development of novel therapies.

Cerebrospinal fluid synaptic biomarker changes in bipolar disorder - A longitudinal case-control study

BACKGROUND

This exploratory study investigated cerebrospinal fluid (CSF) synaptic protein biomarkers in bipolar disorder (BD), aiming to highlight the neurobiological basis of the disorder. With shared cognitive impairment features between BD and Alzheimer's disease, and considering increased dementia risk in BD patients, the study explores potential connections.

METHODS

Fifty-nine well-characterized patients with BD and thirty-seven healthy control individuals were examined and followed for one year. Synaptic proteins encompassing neuronal pentraxins (NPTX)1, NPTX2, and NPTX-receptor, 14-3-3 protein family epsilon, and zeta/delta, activating protein-2 complex subunit beta, synucleins beta-synuclein and gamma-synuclein, complexin-2, phosphatidylethanolamine-binding protein 1, rab GDP dissociation inhibitor alpha, and syntaxins 1B and 7 were measured in CSF using a microflow liquid chromatography-mass spectrometric multiple reaction monitoring set-up. Biomarker levels were compared between BD and HC and in BD before, during, and after mood episodes.

RESULTS

The synaptic proteins revealed no statistically significant differences between BD and HC, neither at baseline, one-year follow-up, or in terms of changes from baseline to follow-up. Moreover, the CSF synaptic protein levels in patients with BD were unaltered compared to baseline when they stabilized in euthymia following an affective episode and at one-year follow-up.

LIMITATION

It is uncertain what the CSF biomarker concentrations reflect since we yet do not know the mechanisms of release of these proteins, and we are uncertain of what increased or decreased levels reflect.

CONCLUSION

This first-ever investigation of a panel of CSF protein biomarkers of synaptic dysfunction in patients with BD and HC individuals found no statistically significant differences cross-sectionally or longitudinally.

Assessment of symptom severity in psychotic disorder patients based on heart rate variability and accelerometer mobility data

BACKGROUND

Advancement in mental health care requires easily accessible, efficient diagnostic and treatment assessment tools. Viable biomarkers could enable objectification and automation of the diagnostic and treatment process, currently dependent on a psychiatric interview. Available wearable technology and computational methods make it possible to incorporate heart rate variability (HRV), an indicator of autonomic nervous system (ANS) activity, into potential diagnostic and treatment assessment frameworks as a biomarker of disease severity in mental disorders, including schizophrenia and bipolar disorder (BD).

METHOD

We used a commercially available electrocardiography (ECG) chest strap with a built-in accelerometer, i.e. Polar H10, to record R-R intervals and physical activity of 30 hospitalized schizophrenia or BD patients and 30 control participants through ca. 1.5-2 h time periods. We validated a novel approach to data acquisition based on a flexible, patient-friendly and cost-effective setting. We analyzed the relationship between HRV and the Positive and Negative Syndrome Scale (PANSS) test scores, as well as the HRV and mobility coefficient. We also proposed a method of rest period selection based on R-R intervals and mobility data. The source code for reproducing all experiments is available on GitHub, while the dataset is published on Zenodo.

RESULTS

Mean HRV values were lower in the patient compared to the control group and negatively correlated with the results of the PANSS general subcategory. For the control group, we also discovered the inversely proportional dependency between the mobility coefficient, based on accelerometer data, and HRV. This relationship was less pronounced for the treatment group.

CONCLUSIONS

HRV value itself, as well as the relationship between HRV and mobility, may be promising biomarkers in disease diagnostics. These findings can be used to develop a flexible monitoring system for symptom severity assessment.

Targeting synapse function and loss for treatment of neurodegenerative diseases

Synapse dysfunction and loss are hallmarks of neurodegenerative diseases that correlate with cognitive decline. However, the mechanisms and therapeutic strategies to prevent or reverse synaptic damage remain elusive. In this Review, we discuss recent advances in understanding the molecular and cellular pathways that impair synapses in neurodegenerative diseases, including the effects of protein aggregation and neuroinflammation. We also highlight emerging therapeutic approaches that aim to restore synaptic function and integrity, such as enhancing synaptic plasticity, preventing synaptotoxicity, modulating neuronal network activity and targeting immune signalling. We discuss the preclinical and clinical evidence for each strategy, as well as the challenges and opportunities for developing effective synapse-targeting therapeutics for neurodegenerative diseases.

Bipolar Disorder

This review focuses on recent advances made towards understanding the neurobiology of bipolar disorder (BD), a chronic neuropsychiatric illness characterized by altered mood and energy states. The past few years have seen the completion of the largest genetic studies by far, which have emphasized the polygenic nature of BD as well as it's connection to other psychiatric illnesses. Furthermore, the use of inducible pluripotent stem cells has rapidly expanded. These studies support previous work that implicates dysregulation of neurodevelopment, mitochondria, and calcium homeostasis, while also allowing for investigation into the underlying mechanisms of individual responsivity to lithium. Sleep and circadian rhythms have also been heavily implicated in BD, from disruptions in activity patterns to molecular abnormalities.

Brain-region-specific changes in neurons and glia and dysregulation of dopamine signaling in Grin2a mutant mice

A genetically valid animal model could transform our understanding of schizophrenia (SCZ) disease mechanisms. Rare heterozygous loss-of-function (LoF) mutations in GRIN2A, encoding a subunit of the NMDA receptor, greatly increase the risk of SCZ. By transcriptomic, proteomic, and behavioral analyses, we report that heterozygous Grin2a mutant mice show (1) large-scale gene expression changes across multiple brain regions and in neuronal (excitatory and inhibitory) and non-neuronal cells (astrocytes and oligodendrocytes), (2) evidence of hypoactivity in the prefrontal cortex (PFC) and hyperactivity in the hippocampus and striatum, (3) an elevated dopamine signaling in the striatum and hypersensitivity to amphetamine-induced hyperlocomotion (AIH), (4) altered cholesterol biosynthesis in astrocytes, (5) a reduction in glutamatergic receptor signaling proteins in the synapse, and (6) an aberrant locomotor pattern opposite of that induced by antipsychotic drugs. These findings reveal potential pathophysiologic mechanisms, provide support for both the "hypo-glutamate" and "hyper-dopamine" hypotheses of SCZ, and underscore the utility of Grin2a-deficient mice as a genetic model of SCZ.

Sleep and circadian rhythm disruption by NPTX2 loss of function

Sleep and circadian rhythm disruption (SCRD) is commonly observed in aging, especially in individuals who experience progressive cognitive decline to mild cognitive impairment (MCI) and Alzheimer's disease (AD). However, precise molecular mechanisms underlying the association between SCRD and aging are not fully understood. Orexin A is a well-characterized "sleep neuropeptide" that is expressed in hypothalamic neurons and evokes wake behavior. The importance of Orexin is exemplified in narcolepsy where it is profoundly down-regulated. Interestingly, the synaptic immediate early gene NPTX2 is co-expressed in Orexin neurons and is similarly reduced in narcolepsy. NPTX2 is also down-regulated in CSF of some cognitively normal older individuals and predicts the time of transition from normal cognition to MCI. The association between Orexin and NPTX2 is further evinced here where we observe that Orexin A and NPTX2 are highly correlated in CSF of cognitively normal aged individuals and raises the question of whether SCRD that are typically attributed to Orexin A loss of function may be modified by concomitant NPTX2 down-regulation. Is NPTX2 an effector of sleep or simply a reporter of orexin-dependent SCRD? To address this question, we examined NPTX2 KO mice and found they retain Orexin expression in the brain and so provide an opportunity to examine the specific contribution of NPTX2 to SCRD. Our results reveal that NPTX2 KO mice exhibit a disrupted circadian onset time, coupled with increased activity during the sleep phase, suggesting difficulties in maintaining states. Sleep EEG indicates distinct temporal allocation shifts across vigilance states, characterized by reduced wake and increased NREM time. Evident sleep fragmentation manifests through alterations of event occurrences during Wake and NREM, notably during light transition periods, in conjunction with an increased frequency of sleep transitions in NPTX2 KO mice, particularly between Wake and NREM. EEG spectral analysis indicated significant shifts in power across various frequency bands in the wake, NREM, and REM states, suggestive of disrupted neuronal synchronicity. An intriguing observation is the diminished occurrence of sleep spindles, one of the earliest measures of human sleep disruption, in NPTX2 KO mice. These findings highlight the effector role of NPTX2 loss of function as an instigator of SCRD and a potential mediator of sleep disruption in aging.

Molecular mechanisms of schizophrenia: Insights from human genetics

Schizophrenia is a debilitating psychiatric disorder that affects millions of people worldwide; however, its etiology is poorly understood at the molecular and neurobiological levels. A particularly important advance in recent years is the discovery of rare genetic variants associated with a greatly increased risk of developing schizophrenia. These primarily loss-of-function variants are found in genes that overlap with those implicated by common variants and are involved in the regulation of glutamate signaling, synaptic function, DNA transcription, and chromatin remodeling. Animal models harboring mutations in these large-effect schizophrenia risk genes show promise in providing additional insights into the molecular mechanisms of the disease.