Association of Per3 length polymorphism with bipolar I disorder and schizophrenia

The influence of PER3 VNTR genotypes on the age of onset in a group of bipolar I disorder patients: an exploratory study

BACKGROUND

PER3 is a circadian gene that contains a variable number of tandem repeats (VNTR) which codifies for three genotypes: 4/4; 4/5; and 5/5 and is involved in non-visual response to light, a critical process associated with bipolar disorder onset. Benedetti et al. (Neurosci Lett 445(2):184-7) related this VNTR with bipolar disorder age of onset and linked genotype 5/5 with an earlier onset. In this study, we aimed to investigate these associations of PER3 VNTR genotypes with age of onset in a homogenous sample of German patients with bipolar I disorder through Kaplan-Meier curves.

METHODS

45 patients were enrolled and divided into three groups according to PER3 VNTR genotypes. Recognizing common biological features, we built a combined group of -5 allele carriers (4/5 + 5/5). As a primary outcome, Kaplan-Meier analysis was conducted to delineate the three genotypes' influence on age of onset. The secondary Kaplan-Meier analysis aimed to evaluate the relation between the 4/4 homozygotes group and the combined group (4/5 + 5/5) with age of onset. Finally, we proceeded to compare groups through a Log Rank Test and performed an analysis of covariance (ANCOVA).

RESULTS

The Kaplan-Meier analysis with three separate genotypes didn't replicate the findings of Benedetti's study. The analysis comparing genotype 4/4 with the combined group showed the influence of PER3 VNTR variants on the age of onset and relates genotype 4/4 to an earlier onset. ANCOVA between the combined and the 4/4 genotype groups, correlated genotype 4/4 with an increased number of depressive episodes.

CONCLUSION

This study showed no significant effect of PER3 VNTR genotypes on the age of onset and in linking genotype 5/5 with an earlier onset age. Contrasting results may arise from intrinsic differences between the two studies but also shed light on hypothetically different levels of functioning of PER3 VNTR genotypes in the context of bipolar pathology. Further studies will require bigger and more homogeneous clinical samples.

The circadian system: A neglected player in neurodevelopmental disorders

Patients with neurodevelopmental disorders, such as autism spectrum disorder, often display abnormal circadian rhythms. The role of the circadian system in these disorders has gained considerable attention over the last decades. Yet, it remains largely unknown how these disruptions occur and to what extent they contribute to the disorders' development. In this review, we examine circadian system dysregulation as observed in patients and animal models of neurodevelopmental disorders. Second, we explore whether circadian rhythm disruptions constitute a risk factor for neurodevelopmental disorders from studies in humans and model organisms. Lastly, we focus on the impact of psychiatric medications on circadian rhythms and the potential benefits of chronotherapy. The literature reveals that patients with neurodevelopmental disorders display altered sleep-wake cycles and melatonin rhythms/levels in a heterogeneous manner, and model organisms used to study these disorders appear to support that circadian dysfunction may be an inherent characteristic of neurodevelopmental disorders. Furthermore, the pre-clinical and clinical evidence indicates that circadian disruption at the environmental and genetic levels may contribute to the behavioural changes observed in these disorders. Finally, studies suggest that psychiatric medications, particularly those prescribed for attention-deficit/hyperactivity disorder and schizophrenia, can have direct effects on the circadian system and that chronotherapy may be leveraged to offset some of these side effects. This review highlights that circadian system dysfunction is likely a core pathological feature of neurodevelopmental disorders and that further research is required to elucidate this relationship.

Lack of association between VNTR variant of the circadian gene (PER3) and major depressive disorder in a sample of a Turkish population

Major depressive disorder (MDD), which is a prevalent psychiatric disorder, is characterized by sleep-wake disturbances. An underlying circadian rhythm disorder mainly may cause these disturbances. The study presented here was designed to investigate the existence of Period Circadian Regulator 3 (PER3) gene VNTR variant in MDD patients in Turkish population. A sample of 118 patients with MDD and 150 healthy volunteers were included in the study. The PER3 VNTR genotyping was performed on DNA by polymerase chain reaction (PCR) using specific primers. The prevalence rates of genotypes of 5/5, 5/4, and 4/4 profiles for the PER3 variant were 30.5%, 55.9%, and 13.6%, respectively, in patients with MDD, and 23.3%, 57.3%, and 19.3%, respectively in the control group. No significant difference was observed between the two groups in terms of either genotype distributions or allele frequencies of the VNTR variant of the PER3 gene (p > 0.05). There was no statistically significant association between the patients and the controls in terms of 5/5 + 4/5 versus 4/4 and 5/5 versus 4/5 + 4/4 (p > 0.05). The present results suggest that the PER3 VNTR variant was not associated with MDD in the Turkish population. However, further studies with other gene variants in different ethnic populations are needed to address the exact role of this variant in MDD.

Insomnia and circadian rhythm: a bibliometrics study and visualization analysis via CiteSpace

Objective

The present study aimed to use CiteSpace to analyze the status of insomnia and circadian rhythm, identify the hot spots and trends, and provide a basis for future study.

Method

The Web of Science database was searched for studies related to insomnia and circadian from its inception to 14 April 2023. CiteSpace was used to generate online maps of collaboration between countries and authors and revealed hot spots and frontiers in insomnia and circadian rhythm.

Results

We searched 4,696 publications related to insomnia and circadian rhythm. Bruno Etain was the most prolific author with most publications, i.e., with 24 articles. The USA and the University of California were the leading country and the top institution in this field of study, with 1,672 and 269 articles, respectively. There was active cooperation between institutions, countries, and authors. Hot topics focused on circadian rhythm sleep disorders, circadian clock, light therapy, melatonin, and bipolar disorder.

Conclusion

Based on the CiteSpace results, we recommend a more active collaboration between various countries, institutions, and authors to conduct clinical and basic research related to insomnia and circadian rhythm. Ongoing research focuses on the interaction of insomnia with circadian rhythms and the corresponding pathways of clock genes and by extension, the role of circadian rhythms in disorders such as bipolar disorder. Modulation of circadian rhythms may be a hot spot for future insomnia therapies (such as light therapy and melatonin).

A circadian rhythm gene (PER3) VNTR variant as possible risk factor in cohort of Turkish females with primary dysmenorrhea

Primary dysmenorrhea (PDM), which is the most prevalent problem related to the menstrual cycle in women of reproductive age, is due to sleep disorders and negative moods. Circadian rhythms, which are the immediate 24-h processes, enable an organism to adapt the suitable physiological responses to the environmental light-dark changes. Disturbed circadian rhythms are closely associated with several diseases, including sleep disorders. It has been reported that variable number tandem repeat (VNTR) variant in the coding region of circadian rhythm gene PERIOD 3 (PER3) affects sleep. Therefore, in the present study, we investigated the association between PDM and PER3 VNTR variant in Turkish females. A sample of 122 females with PDM and 150 healthy females were included in the study. Genoytyping of PER3 VNTR variant was performed on DNA by polymerase chain reaction (PCR) analysis using specific primers. We evaluated the relation between PER3 VNTR variant and PDM by calculating the odds ratios (ORs) and 95% confidence intervals (CIs). In our analyses of genotype data collected from total 272 subjects, we found that the PER3 VNTR variant was associated with development of PDM [codominant model (5/5 vs. 4/4 + 4/5): OR = 0.664; 95% CI, 0.39-1.10; p = 0.05). The three genotypes of the VNTR variant (4/4, 4/5, and 5/5) and their allelic frequencies showed nonsignificant differences between patients and control group (p > 0.05). In summary, PER3 VNTR variant may be associated with PDM in a Turkish female. However, further studies in different ethnic populations are needed to address the full role of this variant in PDM.

For whom the circadian clock ticks? Investigation of PERIOD and CLOCK gene variants in bipolar disorder

Clock genes play significant roles in the regulation of circadian rhythms, which are thought to be involved in the pathophysiology of neurodegenerative and psychiatric diseases. We aimed to investigate the association of five gene polymorphisms (PER3 VNTR (rs57875989), PER2 rs2304672, CLOCK rs1801260, CLOCK rs10462028, CLOCK rs11932595) with PCR-based methods as potential risk factors in bipolar disorder (BD). We used a multiple testing methodology in BD patients (n = 121) and healthy control individuals (n = 121) of Turkish descent to analyze the effects of these gene variants both as risk factors for the disorder and for the evaluation of these variants in the patient group with multiple subscales. We evaluated the circadian rhythm disturbances and seasonal variations in mood and behavior in BD patients using the Biological Rhythms Interview of Assessment in Neuropsychiatry (BRIAN) and Seasonal Pattern Assessment Questionnaire (SPAQ) to enlighten the possible links between these scores and the studied circadian gene variants. The results of our study revealed significant associations: PER3 VNTR (rs57875989) 5/5 repeat genotype displayed a protective effect against BD when compared with 4/4 repeat genotype. Moreover, patients with PER3 VNTR 5/5 repeat genotype displayed a higher ratio of hypomania. PER2 rs2304672 G allele frequency increased the risk for BD. There was no association in terms of genotype/allele frequency comparisons between patients and controls for CLOCK gene variants. However, significant associations were found in patients in terms of clinical and behavioral patterns such as mean age at disease onset and BRIAN total scores enabling some risk stratifications for patients. Our results indicate the significance of circadian gene variants in BD, which need to be confirmed in different studies with larger samples. Thus, the possible endophenotypes of BD can be enlightened and advanced chronotherapeutics approaches can be manipulated in the future for clinical benefit.

Chronobiology Revisited in Psychiatric Disorders: From a Translational Perspective

OBJECTIVE

Several lines of evidence support a relationship between circadian rhythms disruption in the onset, course, and maintenance of mental disorders. Despite the study of circadian phenotypes promising a decent understanding of the pathophysiologic or etiologic mechanisms of psychiatric entities, several questions still need to be addressed. In this review, we aimed to synthesize the literature investigating chronobiologic theories and their associations with psychiatric entities.

METHODS

The Medline, Embase, PsycInfo, and Scopus databases were comprehensively and systematically searched and articles published between January 1990 and October 2019 were reviewed. Different combinations of the relevant keywords were polled. We first introduced molecular elements and mechanisms of the circadian system to promote a better understanding of the chronobiologic implications of mental disorders. Then, we comprehensively and systematically reviewed circadian system studies in mood disorders, schizophrenia, and anxiety disorders.

RESULTS

Although subject characteristics and study designs vary across studies, current research has demonstrated that circadian pathologies, including genetic and neurohumoral alterations, represent the neural substrates of the pathophysiology of many psychiatric disorders. Impaired HPA-axis function-related glucocorticoid rhythm and disrupted melatonin homeostasis have been prominently demonstrated in schizophrenia and other psychotic disorders, while alterations of molecular expressions of circadian rhythm genes including CLOCK, PER, and CRY have been reported to be involved in the pathogenesis of mood disorders.

CONCLUSION

Further translational work is needed to identify the causal relationship between circadian physiology abnormalities and mental disorders and related psychopathology, and to develop sound pharmacologic interventions.

A Topological Cluster of Differentially Regulated Genes in Mice Lacking PER3

Polymorphisms in the human circadian clock gene PERIOD3 (PER3) are associated with a wide variety of phenotypes such as diurnal preference, delayed sleep phase disorder, sleep homeostasis, cognitive performance, bipolar disorder, type 2 diabetes, cardiac regulation, cancer, light sensitivity, hormone and cytokine secretion, and addiction. However, the molecular mechanisms underlying these phenotypic associations remain unknown. Per3 knockout mice (Per3^-/- ) have phenotypes related to activity, sleep homeostasis, anhedonia, metabolism, and behavioral responses to light. Using a protocol that induces behavioral differences in response to light in wild type and Per3^-/- mice, we compared genome-wide expression in the eye and hypothalamus in the two genotypes. Differentially expressed transcripts were related to inflammation, taste, olfactory and melatonin receptors, lipid metabolism, cell cycle, ubiquitination, and hormones, as well as receptors and channels related to sleep regulation. Differentially expressed transcripts in both tissues co-localized with Per3 on an ∼8Mbp region of distal chromosome 4. The most down-regulated transcript is Prdm16, which is involved in adipocyte differentiation and may mediate altered body mass accumulation in Per3^-/- mice. eQTL analysis with BXD mouse strains showed that the expression of some of these transcripts and also others co-localized at distal chromosome 4, is correlated with brain tissue expression levels of Per3 with a highly significant linkage to genetic variation in that region. These data identify a cluster of transcripts on mouse distal chromosome 4 that are co-regulated with Per3 and whose expression levels correlate with those of Per3. This locus lies within a topologically associating domain island that contains many genes with functional links to several of the diverse non-circadian phenotypes associated with polymorphisms in human PER3.

Sleep and Circadian Rhythm Disorder in Bipolar Affective Disorder

Symptoms of affective disorders encompass a range of changes to biological processes such as sleep and appetite. These processes are regulated over a 24-h cycle known as the circadian rhythm. Sleep is a particularly useful marker of this rhythm as it is readily measurable and functionally significant. Sleep disturbance is common in bipolar affective disorder and may act as a marker, and precipitant, of relapse. Circadian rhythms are modulated by environmental and social cues and have been shown to be influenced by treatment in BPAD. As such understanding of circadian rhythms may lead to a better understanding of the pathophysiology of BPAD and its treatment. This chapter will explore the neurobiology of the circadian clock and the putative role of circadian rhythm dysregulation in the pathophysiology and treatment of bipolar affective disorder (BPAD).

Genetic influence alters the brain synchronism in perception and timing

Background

Studies at the molecular level aim to integrate genetic and neurobiological data to provide an increasingly detailed understanding of phenotypes related to the ability in time perception.

Main Text

This study suggests that the polymorphisms genetic SLC6A4 5-HTTLPR, 5HTR2A T102C, DRD2/ANKK1-Taq1A, SLC6A3 3’-UTR VNTR, COMT Val158Met, CLOCK genes and GABRB2 A/C as modification factor at neurochemical levels associated with several neurofunctional aspects, modifying the circadian rhythm and built-in cognitive functions in the timing. We conducted a literature review with 102 studies that met inclusion criteria to synthesize findings on genetic polymorphisms and their influence on the timing.

Conclusion

The findings suggest an association of genetic polymorphisms on behavioral aspects related in timing. However, order to confirm the paradigm of association in the timing as a function of the molecular level, still need to be addressed future research.

Potential biomarkers for bipolar disorder: Where do we stand?

Bipolar disorder (BD) is a severe, recurrent mood disorder, associated with a significant morbidity and mortality, with high rates of suicides and medical comorbidities. There is a high risk of mood disorders among the first-degree relatives of patients with BD. In the current clinical practice, the diagnosis of BD is made by history taking, interview and behavioural observations, thereby lacking an objective, biological validation. This approach may result in underdiagnosis, misdiagnosis and eventually poorer outcomes. Due to the heterogeneity of BD, the possibility of developing a single, specific biomarker is still remote; however, there is a set of promising biomarkers which may serve as predictive, prognostic or treatment markers in the future. The review presents a critical appraisal and update on some of the most promising candidates for biomarkers, namely, neuroimaging markers, peripheral biomarkers and genetic markers, including a brief discussion on cognitive endophenotypes as indicative of genetic risk. The lessons learnt from other fields and specialties in medicine need to be applied to psychiatry to translate the knowledge from ‘bench to bedside’ by means of clinically useful biomarkers. Overall, the biomarkers may help in pushing the shift towards personalized medicine for psychiatric patients.

Genetic Association of the PERIOD3 (Per3) Clock Gene with Bipolar Disorder

OBJECTIVE

Circadian rhythms have been linked to psychiatric disorders such as Depression and Bipolar Disorder (BD). Given previous evidences of sleep/circadian disturbances as well as the genetic susceptibility for BD, we decided to investigate the possible link between the PERIOD3 (Per3) circadian gene and BD.

METHODS

This is a genetic association case (BD) vs. control study of the Per3 gene. We further subdivided our BD sample into "good sleepers" (PSQI ≤5) and "poor sleepers" (PSQI>5) according to the Pittsburgh Sleep Quality Index (PSQI) global score, and then we assessed genetic association of the Per3 gene with sleep quality in the BD group.

RESULTS

There were 209 cases and 213 controls in our sample. The GT genotype of the SNP rs707467 significantly associated with BD (χ²=8.80; p-value=0.01; adjusted residual=±2.6). We also found significant association of the SNP rs10462020 allele T with BD (χ²=5.81; p-value=0.01) as well as the genotype TT (χ²= 6.01; p-value=0.04; adjusted residual=±2.4).

CONCLUSION

In this study we demonstrated evidences of genetic association between the Per3 gene and BD. The results of association between the Per3 gene and BD in our sample may bring additional evidence to the former findings of association between the Per3 gene and BD.

Circadian Clock Model Supports Molecular Link Between PER3 and Human Anxiety

Generalized anxiety and major depression have become increasingly common in the United States, affecting 18.6 percent of the adult population. Mood disorders can be debilitating, and are often correlated with poor general health, life dissatisfaction, and the need for disability benefits due to inability to work. Recent evidence suggests that some mood disorders have a circadian component, and disruptions in circadian rhythms may even trigger the development of these disorders. However, the molecular mechanisms of this interaction are not well understood. Polymorphisms in a circadian clock-related gene, PER3, are associated with behavioral phenotypes (extreme diurnal preference in arousal and activity) and sleep/mood disorders, including seasonal affective disorder (SAD). Here we show that two PER3 mutations, a variable number tandem repeat (VNTR) allele and a single-nucleotide polymorphism (SNP), are associated with diurnal preference and higher Trait-Anxiety scores, supporting a role for PER3 in mood modulation. In addition, we explore a potential mechanism for how PER3 influences mood by utilizing a comprehensive circadian clock model that accurately predicts the changes in circadian period evident in knock-out phenotypes and individuals with PER3-related clock disorders.

Clock Genes and Altered Sleep-Wake Rhythms: Their Role in the Development of Psychiatric Disorders

In mammals, the circadian clocks network (central and peripheral oscillators) controls circadian rhythms and orchestrates the expression of a range of downstream genes, allowing the organism to anticipate and adapt to environmental changes. Beyond their role in circadian rhythms, several studies have highlighted that circadian clock genes may have a more widespread physiological effect on cognition, mood, and reward-related behaviors. Furthermore, single nucleotide polymorphisms in core circadian clock genes have been associated with psychiatric disorders (such as autism spectrum disorder, schizophrenia, anxiety disorders, major depressive disorder, bipolar disorder, and attention deficit hyperactivity disorder). However, the underlying mechanisms of these associations remain to be ascertained and the cause–effect relationships are not clearly established. The objective of this article is to clarify the role of clock genes and altered sleep–wake rhythms in the development of psychiatric disorders (sleep problems are often observed at early onset of psychiatric disorders). First, the molecular mechanisms of circadian rhythms are described. Then, the relationships between disrupted circadian rhythms, including sleep–wake rhythms, and psychiatric disorders are discussed. Further research may open interesting perspectives with promising avenues for early detection and therapeutic intervention in psychiatric disorders.

Human genetics and sleep behavior

Why we sleep remains one of the greatest mysteries in science. In the past few years, great advances have been made to better understand this phenomenon. Human genetics has contributed significantly to this movement, as many features of sleep have been found to be heritable. Discoveries about these genetic variations that affect human sleep will aid us in understanding the underlying mechanism of sleep. Here we summarize recent discoveries about the genetic variations affecting the timing of sleep, duration of sleep and EEG patterns. To conclude, we also discuss some of the sleep-related neurological disorders such as Autism Spectrum Disorder (ASD) and Alzheimer's Disease (AD) and the potential challenges and future directions of human genetics in sleep research.

Analysis of 23andMe antidepressant efficacy survey data: implication of circadian rhythm and neuroplasticity in bupropion response

Genetic predisposition may contribute to the differences in drug-specific, class-specific or antidepressant-wide treatment resistance. Clinical studies with the genetic data are often limited in sample sizes. Drug response obtained from self-reports may offer an alternative approach to conduct a study with much larger sample size. Using the phenotype data collected from 23andMe 'Antidepressant Efficacy and Side Effects' survey and genotype data from 23andMe's research participants, we conducted genome-wide association study (GWAS) on subjects of European ancestry using four groups of phenotypes (a) non-treatment-resistant depression (n=7795) vs treatment-resistant depression (TRD, n=1311), (b) selective serotonin reuptake inhibitors (SSRI) responders (n=6348) vs non-responders (n=3340), (c) citalopram/escitalopram responders (n=2963) vs non-responders (n=2005), and (d) norepinephrine-dopamine reuptake inhibitor (NDRI, bupropion) responders (n=2675) vs non-responders (n=1861). Each of these subgroups was also compared with controls (n ~ 190 000). The most significant association was from bupropion responders vs non-responders analysis. Variant rs1908557 (P=2.6 × 10(-8), OR=1.35) passed the conventional genome-wide significance threshold (P=5 × 10(-8)) and was located within the intron of human spliced expressed sequence tags in chromosome 4. Gene sets associated with long-term depression, circadian rhythm and vascular endothelial growth factor (VEGF) pathway were enriched in the bupropion analysis. No single-nucleotide polymorphism passed genome-wide significance threshold in other analyses. The heritability estimates for each response group compared with controls were between 0.15 and 0.25, consistent with the known heritability for major depressive disorder.

Evidences of Polymorphism Associated with Circadian System and Risk of Pathologies: A Review of the Literature

The circadian system is a supraphysiological system that modulates different biological functions such as metabolism, sleep-wake, cellular proliferation, and body temperature. Different chronodisruptors have been identified, such as shift work, feeding time, long days, and stress. The environmental changes and our modern lifestyle can alter the circadian system and increase the risk of developing pathologies such as cancer, preeclampsia, diabetes, and mood disorder. This system is organized by transcriptional/tranductional feedback loops of clock genes Clock, Bmal1, Per1-3, and Cry1-2. How molecular components of the clock are able to influence the development of diseases and their risk relation with genetic components of polymorphism of clock genes is unknown. This research describes different genetic variations in the population and how these are associated with risk of cancer, metabolic diseases such as diabetes, obesity, and dyslipidemias, and also mood disorders such as depression, bipolar disease, excessive alcohol intake, and infertility. Finally, these findings will need to be implemented and evaluated at the level of genetic interaction and how the environment factors trigger the expression of these pathologies will be examined.

Personalized medicine for pathological circadian dysfunctions

The recent approval of a therapeutic for a circadian disorder has increased interest in developing additional medicines for disorders characterized by circadian disruption. However, previous experience demonstrates that drug development for central nervous system (CNS) disorders has a high failure rate. Personalized medicine, or the approach to identifying the right treatment for the right patient, has recently become the standard for drug development in the oncology field. In addition to utilizing Companion Diagnostics (CDx) that identify specific genetic biomarkers to prescribe certain targeted therapies, patient profiling is regularly used to enrich for a responsive patient population during clinical trials, resulting in fewer patients required for statistical significance and a higher rate of success for demonstrating efficacy and hence receiving approval for the drug. This personalized medicine approach may be one mechanism that could reduce the high clinical trial failure rate in the development of CNS drugs. This review will discuss current circadian trials, the history of personalized medicine in oncology, lessons learned from a recently approved circadian therapeutic, and how personalized medicine can be tailored for use in future clinical trials for circadian disorders to ultimately lead to the approval of more therapeutics for patients suffering from circadian abnormalities.