Genetic Variants Involved in Bipolar Disorder, a Rough Road Ahead

Bipolar Patient-Specific In Vitro Diagnostic Test Reveals Underlying Cardiac Arrhythmia Phenotype Caused by Calcium Channel Genetic Risk Factor

A common genetic risk factor for bipolar disorder is CACNA1C, a gene that is also critical for cardiac rhythm. The impact of CACNA1C mutations on bipolar patient cardiac rhythm is unknown. Here, we report the cardiac electrophysiological implications of a bipolar disorder-associated genetic risk factor in CACNA1C using patient induced pluripotent stem cell-derived cardiomyocytes. Results indicate that the CACNA1C bipolar disorder-related mutation causes cardiac electrical impulse conduction slowing mediated by impaired intercellular coupling via connexin 43 gap junctions. In vitro gene therapy to restore connexin 43 expression increased cardiac electrical impulse conduction velocity and protected against thioridazine-induced QT prolongation. Patients positive for bipolar disorder CACNA1C genetic risk factors may have elevated proarrhythmic risk for adverse events in response to psychiatric medications that slow conduction or prolong the QT interval. This in vitro diagnostic tool enables cardiac testing specific to patients with psychiatric disorders to determine their sensitivity to off-target effects of psychiatric medications.

Bipolar disorder-iPSC derived neural progenitor cells exhibit dysregulation of store-operated Ca2+ entry and accelerated differentiation

While most of the efforts to uncover mechanisms contributing to bipolar disorder (BD) focused on phenotypes at the mature neuron stage, little research has considered events that may occur during earlier timepoints of neurodevelopment. Further, although aberrant calcium (Ca2+) signaling has been implicated in the etiology of this condition, the possible contribution of store-operated Ca2+ entry (SOCE) is not well understood. Here, we report Ca2+ and developmental dysregulations related to SOCE in BD patient induced pluripotent stem cell (iPSC)-derived neural progenitor cells (BD-NPCs) and cortical-like glutamatergic neurons. First, using a Ca2+ re-addition assay we found that BD-NPCs and neurons had attenuated SOCE. Intrigued by this finding, we then performed RNA-sequencing and uncovered a unique transcriptome profile in BD-NPCs suggesting accelerated neurodifferentiation. Consistent with these results, we measured a slower rate of proliferation, increased neurite outgrowth, and decreased size in neurosphere formations with BD-NPCs. Also, we observed decreased subventricular areas in developing BD cerebral organoids. Finally, BD NPCs demonstrated high expression of the let-7 family while BD neurons had increased miR-34a, both being microRNAs previously implicated in neurodevelopmental deviations and BD etiology. In summary, we present evidence supporting an accelerated transition towards the neuronal stage in BD-NPCs that may be indicative of early pathophysiological features of the disorder.

Is a Genetic Variant associated with Bipolar Disorder Frequent in People without Bipolar Disorder but with Characteristics of Hyperactivity and Novelty Seeking?

Objective

The objective is to verify whether a genetic condition associated with bipolar disorder (BD) is frequent in old adults adapted to their environment, without BD, but with aptitudes for hyperactivity and novelty seeking (H/NS).

Methods

In this cross-sectional study, the study sample included healthy elderly people (40 participants, aged 60 or older) living in an urban area and recruited from a previous study on physical exercise and active aging, who were compared with 21 old adults with BD from the same area. The genetic methodology consisted of blood sampling, DNA extraction, real-time PCR jointly with FRET probes, and the SANGER sequencing method. The genetic variant RS1006737 of CACNA1C, found to be associated with bipolar disorder diagnosis, was investigated.

Results

The frequency of the RS1006737 genetic variant in the study group (H/NS) is not higher than in the BD group and is statistically significantly higher than in all the control groups found in the literature. However, the familiarity for BD is higher in old adults with BD than in the H/NS sample without BD. The risk of BD in the family (also considering those without BD but with family members with BD) is not associated with the presence of the genetic variant examined.

Conclusion

The study suggests that the gene examined is associated with characteristics of hyperactivity rather than just BD. Nevertheless, choosing to participate in an exercise program is an excessively general way to identify H/NS. The next step would be to identify the old adults with well-defined H/NS features with an adequate tool.

Usefulness of salivary sampling for the molecular detection of a genetic variant associated with bipolar disorders

Under certain conditions, the hyperthymic temperament traits associated with an increased risk of developing bipolar disorders may in fact produce adaptive responses. The purpose of this study is to see if the type of biological material used for genetic analysis (saliva or blood) affects the detection of mutations in the CACNA1C (RS1006737) gene. The first experimental group consisted of Sardinian migrants (“volunteers”) in South American and European megacities. The second experimental group consisted of older healthy subjects with hyperactivity and novelty-seeking characteristics from Cagliari, Italy. The genetic procedure included DNA extraction, real-time PCR, and the Sanger method. Nonetheless, the authors believe that saliva is the most appropriate biological material, given its many advantages. In contrast to blood, saliva can be collected by any type of healthcare provider after following a few simple instructions.

Role of TNF-α -308G/A Polymorphism in Bipolar Disorder and its Relationship with Clinical and Demographic Variables

Objective

Gene-environment interactions might play a significant role in the development of bipolar disorder (BD). The objective of the current study was to investigate the association between tumor necrosis factor (TNF)-α -308 G/A polymorphism and BD and conduct a bioinformatics analysis of the protein-protein network of TNF-α. Gene-environment interactions and the relationship between stressful life events (SLEs) and substance abuse with TNF genotypes and other characteristics were analyzed.

Methods

The genomic deoxyribonucleic acid (DNA) of 400 patients with BD and 200 control subjects were extracted and genotyped for TNF-α -308 G/A polymorphism. SLEs and substance abuse were evaluated using the Life Event and Difficulty Schedule (LEDS) and a self-designed substance abuse questionnaire for the events six months prior to the onset of the disease, respectively. Gene-environment interactions were assessed by multiple statistical tools. Bioinformatics analysis of the TNF-α network and its interacting proteins was carried out using STRING and Cytoscape softwares.

Results

Genotyping analysis revealed a significant association between TNF-α -308 G/A polymorphism and BD (p<0.009). Furthermore, analysis of gene-environment interaction revealed a significant association between TNF-α -308 G/A and SLEs (p=0.001) and TNF-α -308 G/A and substance abuse (p=0.001). Three distinct proteins, RELA, RIPK1, and BIRC3, were identified through hub analysis of the protein network.

Conclusion

TNF-α -308 G/A polymorphism is positively associated with BD. SLEs and substance abuse might trigger the early onset of BD. Proteins identified through bioinformatics analysis might contribute to the TNF-α mediated pathophysiology of BD and can be the potential therapeutic targets.

Can an Investigation of a Single Gene be Effective in Differentiating Certain Features of the Bipolar Disorder Profile?

Bipolar disorder (BD) is amongst the most common heritable mental disorders, but the clarification of its genetic roots has proven to be very challenging. Many single nucleotide polymorphisms (SNPs) have been identified to be associated with BD. SNPs in the CACNA1C gene have emerged as the most significantly associated with the disease. The aim of the present study is to provide a concise description of SNP 1006737 variants identified by Real Time PCR and confirm sequencing analysis with the Sanger method in order to estimate the association with BD. The molecular method was tested on 47 Sardinian subjects of whom 23 were found to not be mutated, 1 was found to be a carrier of the homozygous A allele and 23 were found to be carriers of the heterozygous G allele. Moreover, the positive results of the preliminary application suggest that the development of the screener could be extended to the other 5 genetic variables identified as associated with BD.

The Relationship between rs534654 Polymorphism in TMEM165 Gene and Increased Risk of Bipolar Disorder Type 1

Bipolar disorder (BD) is a major health care concern worldwide. There are some reports showing an association between genes and their variants involved in circadian rhythm; clock and clock related genes function and development of BD in patients. Therefore, the aim of this study was to investigate the possible association of rs534654 variant on TMEM165 (transmembrane protein 165) gene with the risk of BD. Genotyping of the rs534654 was carried out using the tetra primers- amplification refractory mutation system-PCR (4P-ARMS-PCR) method in 203 patients with BD type 1 and their healthy and normal counterpart. The frequency of the G and A alleles of rs534654 polymorphism was 53% and 47%, respectively in patients. Genotype frequency in patients in comparison with control subjects was 5.4% vs 2.5% for the AA homozygous; 11.3% vs 80.8% for the GG homozygous; and 83.3% vs 16.7% for the heterozygous AG. Statistical analysis showed a significant difference in frequencies between the control and patient groups (P = 0.001). Based on this finding, it is possible to conclude that the impairment in the rs534654 single nucleotide polymorphism in TMEM165 gene is associated with the risk of BD development.

SERINC2 increases the risk of bipolar disorder in the Chinese population

BACKGROUND

Although common variants in a large collection of patients are associated with increased risk for bipolar disorder (BD), studies have only been able to predict 25%-45% of risks, suggesting that lots of variants that contribute to the risk for BD haven't been identified. Our study aims to identify novel BD risk genes.

METHODS

We performed whole-exome sequencing of 27 individuals from 6 BD multi-affected Chinese families to identify candidate variants. Targeted sequencing of one of the novel risk genes, SERINC2, in additional sporadic 717 BD patients and 312 healthy controls (HC) validated the association. Magnetic resonance imaging (MRI) were performed to evaluate the effect of the variant to brain structures from 213 subjects (4 BD subjects from a multi-affected family, 130 sporadic BD subjects and 79 HC control).

RESULTS

BD pedigrees had an increased burden of uncommon variants in extracellular matrix (ECM) and calcium ion binding. By large-scale sequencing we identified a novel recessive BD risk gene, SERINC2, which plays a role in synthesis of sphingolipid and phosphatidylserine (PS). MRI image results show the homozygous nonsense variant in SERINC2 affects the volume of white matter in cerebellum.

CONCLUSIONS

Our study identified SERINC2 as a risk gene of BD in the Chinese population.

Electrophysiological correlates of visual backward masking in patients with bipolar disorder

In visual backward masking (VBM), a target is followed by a mask that decreases target discriminability. Schizophrenia patients (SZ) show strong and reproducible masking impairments, which are associated with reduced EEG amplitudes. Patients with bipolar disorder (BP) show masking deficits, too. Here, we investigated the neural EEG correlates of VBM in BP. 122 SZ, 94 unaffected controls, and 38 BP joined a standard VBM experiment. 123 SZ, 94 unaffected controls and 16 BP joined a corresponding EEG experiment, analyzed in terms of global field power. As in previous studies, SZ and BP show strong masking deficits. Importantly and similarly to SZ, BP show decreased global field power amplitudes at approximately 200 ms after the target onset, compared to controls. These results suggest that VBM deficits are not specific for schizophrenia but for a broader range of functional psychoses. Potentially, both SZ and BP show deficient target enhancement.

Living With Bipolar Disorder in the Time of Covid-19: Biorhythms During the Severe Lockdown in Cagliari, Italy, and the Moderate Lockdown in Tunis, Tunisia

Background: Restrictions during Covid-19 pandemic lockdown, in which rhythms of life have been compromised, can influence the course of bipolar disorder (BD). This study follows patients with bipolar disorder living in two geographically close cities (Cagliari and Tunis), but with different lockdown conditions: less severe in Tunis. Methods: Two cohorts were evaluated during lockdown (April 2020, t0) and 2 months later with lockdown lifted for a month (t1). Individuals were: over 18 years old without gender exclusion, BD I or II, in care for at least 1 year, received a clinical interview in the month before the start of the lockdown, stable clinically before the lockdown. The assessment was conducted by telephone by a psychiatrist or psychologist with good knowledge of patients. Diagnoses were made according to DSM-5 criteria. Depressive symptoms were collected through the Hamilton Rating Scale for Depression; cut-off 14 indicative of depressive episode. Circadian rhythms were measured using the BRIAN scale. Results: Forty individuals in Cagliari (70%female, age 48.57 ± 11.64) and 30 in Tunis (53.3% Female, age 41.8 ± 13.22) were recruited. In Cagliari at t0 45% had depressive episodes against none in Tunis, a similar difference appeared at t1. At t0 and t1 the Cagliari sample had more dysfunctional scores in the overall BRIAN scale and in the areas of sleep, activities and social rhythms; no differences were found in nutrition, both samples had predominantly nocturnal rhythm. In Cagliari at t0 and t1, the depressive sub-group showed more dysfunctional scores in the BRIAN areas sleep, activity, and nutrition. However, the differences in biological rhythms resulted, through ANCOVA analysis, independent of the co-presence of depressive symptoms. Discussion: A rigid lockdown could expose people with BD to depressive relapse through dysregulation of biological rhythms. The return to more functional rhythms did not appear 1 month after lockdown. The rekindling of the pandemic and the restoration of new restrictive measures will prevent, at least in the short term, the beneficial effect of a return to normality of the two cohorts. This was a limited exploratory study; future studies with larger samples and longer observational time are needed to verify the hypothesis.

Genetic Advance in Depressive Disorder

Major depressive disorder (MDD) and bipolar disorder (BPD) are both chronic, severe mood disorder with high misdiagnosis rate, leading to substantial health and economic burdens to patients around the world. There is a high misdiagnosis rate of bipolar depression (BD) just based on symptomology in depressed patients whose previous manic or mixed episodes have not been well recognized. Therefore, it is important for psychiatrists to identify these two major psychiatric disorders. Recently, with the accumulation of clinical sample sizes and the advances of methodology and technology, certain progress in the genetics of major depression and bipolar disorder has been made. This article reviews the candidate genes for MDD and BD, genetic variation loci, chromosome structural variation, new technologies, and new methods.

Clinical phenotype and genetic risk factors for bipolar disorder with binge eating: an update

Introduction: Clinical and genetic study of psychiatric conditions has underscored the co-occurrence of complex phenotypes and the need to refine them. Bipolar Disorder (BD) and Binge Eating (BE) behavior are common psychiatric conditions that have high heritability and high co-occurrence, such that at least one quarter of BD patients have BE (BD + BE). Genetic studies of BD alone and of BE alone suggest complex polygenic risk models, with many genetic risk loci yet to be identified. Areas covered: We review studies of the epidemiology of BD+BE, its clinical features (cognitive traits, psychiatric comorbidity, and role of obesity), genomic studies (of BD, eating disorders (ED) defined by BE, and BD + BE), and therapeutic implications of BD + BE. Expert opinion: Subphenotyping of complex psychiatric disorders reduces heterogeneity and increases statistical power and effect size; thus, it enhances our capacity to find missing genetic (and other) risk factors. BD + BE has a severe clinical picture and genetic studies suggests a distinct genetic architecture. Differential therapeutic interventions may be needed for patients with BD + BE compared with BD patients without BE. Recognizing the BD + BE subphenotype is an example of moving towards more precise clinical and genetic entities.

A review on shared clinical and molecular mechanisms between bipolar disorder and frontotemporal dementia

Mental disorders are highly prevalent and important causes of medical burden worldwide. Co-occurrence of neurological and psychiatric symptoms are observed among mental disorders, representing a challenge for their differential diagnosis. Psychiatrists and neurologists have faced challenges in diagnosing old adults presenting behavioral changes. This is the case for early frontotemporal dementia (FTD) and bipolar disorder. In its initial stages, FTD is characterized by behavioral or language disturbances in the absence of cognitive symptoms. Consequently, patients with the behavioral subtype of FTD (bv-FTD) can be initially misdiagnosed as having a psychiatric disorder, typically major depression disorder (MDD) or bipolar disorder (BD). Bipolar disorder is associated with a higher risk of dementia in older adults and with cognitive impairment, with a subset of patients presents a neuroprogressive pattern during the disease course. No mendelian mutations were identified in BD, whereas three major genetic causes of FTD have been identified. Clinical similarities between BD and bv-FTD raise the question whether common molecular pathways might explain shared clinical symptoms. Here, we reviewed existing data on clinical and molecular similarities between BD and FTD to propose biological pathways that can be further investigated as common or specific markers of BD and FTD.

Psychological interventions for young people at risk for bipolar disorder: A systematic review

OBJECTIVES

Several studies have recently been conducted that have explored the benefits of psychological interventions in reducing symptomatology or improving outcomes in young people at-risk of developing bipolar disorder. The aim of this review was to explore if such interventions reduce current psychiatric symptoms and prevent the development of new symptoms.

METHODS

A systematic review was conducted using the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA). Databases searched were MEDLINE, EMBASE, PsychInfo, CINAHL and SCOPUS from January 1990 until August 2018. The inclusion criteria were young people aged under 30 years with a family history of bipolar disorder and any empirical studies that contained a psychological or psychoeducation intervention.

RESULTS

A total of 7 articles (N = 138, 55 males) were included (mean age ranged from 12 to 15 years). Interventions conducted included Family Focussed Therapy, Interpersonal and Social Rhythm Therapy, and Mindfulness-based Cognitive Therapy for Children. Significant results were found in some studies, depending on the sample's initial symptoms, with reduced time to relapse and reduced symptoms of anxiety, depression and hypo/mania being found.

LIMITATIONS

No studies have explored if interventions may delay the time to onset of first hypo/manic episodes and only two randomised controlled trials were identified.

CONCLUSIONS

Some significant results were noted with lower symptoms of anxiety, depression and hypo/mania being found in some studies. It is currently unclear if psychological interventions may prevent the development of bipolar disorder or other psychiatric symptoms over time; further longitudinal studies are required.

Can P300 aid in the differential diagnosis of unipolar disorder versus bipolar disorder depression? A meta-analysis of comparative studies

BACKGROUND

It is difficult to distinguish between bipolar disorder (BD) and unipolar disorder (UD) depression. Given the different pattern of cognitive impairments between BD and UD, P300 is potentially useful for the differential diagnosis. This meta-analysis was performed to estimate the extent of difference in P300 in patients with BD versus UD depression.

METHODS

Studies comparing P300 between depressed BD and UD patients with or without healthy controls (HCs) were retrieved from major English and Chinese databases. Studies with BD and UD samples that were comparable in terms of age, gender, and depression severity, were rated as having high quality. Standardized mean differences (SMDs) of P300 latency and amplitude were calculated.

RESULTS

In total, eight studies with a total of 397 depressed BD patients, 390 depressed UD patients, and 497 HCs, were included. Among included studies, six were rated as having good quality and three followed BD (n = 146) and UD (n = 144) patients during remission. BD patients had significantly longer P300 latency than UD patients during major depressive episode [SMD (95%CI): 0.580 (0.309, 0.850)] and remission [SMD (95%CI): 1.583 (1.322, 1.844)]. Compared to HCs, remitted BD patients still had significantly longer P300 latency [SMD (95%CI): 0.857 (0.059, 1.656)] but P300 latency of remitted UD patients had decreased to normal [SMD (95%CI): 0.536 (-0.272, 1.343)].

LIMITATIONS

Sample sizes of depressed and remitted patients with BD and UD of included studies are small.

CONCLUSIONS

P300 latency can be used as an auxiliary diagnostic marker for differentiating BD from UD depression.