Sexually Dimorphic,Developmental, and Chronobiological Behavioral Profiles of a Mouse Mania Model

Bipolar disorders are heritable psychiatric conditions often abstracted by separate animal models for mania and depression. The principal mania models involve transgenic manipulations or treatment with stimulants. An additional approach involves analysis of naturally occurring mania models including an inbred strain our lab has recently characterized, the Madison (MSN) mouse strain. These mice show a suite of behavioral and neural genetic alterations analogous to manic aspects of bipolar disorders. In the current study, we extended the MSN strain''s behavioral phenotype in new directions by examining in-cage locomotor activity. We found that MSN activity presentation is sexually dimorphic, with MSN females showing higher in-cage activity than MSN males. When investigating development, we found that MSN mice display stable locomotor hyperactivity already observable when first assayed at 28 days postnatal. Using continuous monitoring and analysis for 1 month, we did not find evidence of spontaneous bipolarism in MSN mice. However, we did find that the MSN strain displayed an altered diurnal activity profile, getting up earlier and going to sleep earlier than control mice. Long photoperiods were associated with increased in-cage activity in MSN, but not in the control strain. The results of these experiments reinforce the face validity of the MSN strain as a complex mania model, adding sexual dimorphism, an altered diurnal activity profile, and seasonality to the suite of interesting dispositional phenomena related to mania seen in MSN mice.     

Molecular genetics of bipolar disorder

Bipolar disorder (BPD) is an often devastating illness characterized by extreme mood dysregulation. Although family, twin and adoption studies consistently indicate a strong genetic component, specific genes that contribute to the illness remain unclear. This study gives an overview of linkage studies of BPD, concluding that the regions with the best evidence for linkage include areas on chromosomes 2p, 4p, 4q, 6q, 8q, 11p, 12q, 13q, 16p, 16q, 18p, 18q, 21q, 22q and Xq. Association studies are summarized, which support a possible role for numerous candidate genes in BPD including COMT, DAT, HTR4, DRD4, DRD2, HTR2A, 5-HTT, the G72/G30 complex, DISC1, P2RX7, MAOA and BDNF. Animal models related to bipolar illness are also reviewed, with special attention paid to those with clear genetic implications. We conclude with suggestions for strategies that may help clarify the genetic bases of this complex illness.     

Cross‐species genetics converge to TLL2 for mouse avoidance behavior and human bipolar disorder

Interspecies genetic analysis of neurobehavioral traits is critical for identifying neurobiological mechanisms underlying psychiatric disorders, and for developing models for translational research. Recently, after screening a chromosome substitution strain panel in an automated home cage environment, chromosomes 15 and 19 were identified in female mice for carrying genetic loci that contribute to increased avoidance behavior (sheltering preference). Furthermore, we showed that the quantitative trait locus (QTL) for baseline avoidance behavior on chromosome 15 is homologous with a human linkage region for bipolar disorder (8q24). Similarly, we now performed comparative analysis on the QTL for avoidance behavior found on chromosome 19 and correspondingly revealed an overlap of the mouse interval and human homologous region 10q23‐24, which has been previously linked to bipolar disorders. By means of a comparative genetic strategy within the human homologous region, we describe an association for TLL2 with bipolar disorder using the genome‐wide association study (GWAS) data set generated by the Wellcome Trust Case Control Consortium (WTCCC). On the basis of genetic homology and mood stabilizer sensitivity, our data indicate the intriguing possibility that mouse home cage avoidance behavior may translate to a common biochemical mechanisms underlying bipolar disorder susceptibility. These findings pave new roads for the identification of the molecular mechanisms and novel treatment possibilities for this psychiatric disorder, as well as for the validity of translational research of associated psychiatric endophenotypes .     

Borderline typical symptoms in adult patients with attention deficit/hyperactivity disorder

Adult attention deficit/hyperactivity disorder (ADHD) and borderline personality disorder (BPD) share several clinical features, e.g. emotional lability and impulsivity. This study aimed to delineate differences and similarities between ADHD and BPD with respect to borderline typical symptomatology and gender specifics. Borderline symptomatology was assessed in 60 adult patients with ADHD with the borderline symptom list (BSL) and compared to both 60 gender- and age-matched BPD patients and control subjects. The BSL is a standardized instrument including 95 items on 7 subscales (self-perception, affect regulation, self-destruction, dysphoria, loneliness, intrusions and hostility). Adult ADHD patients showed significantly higher BSL total scores and all of the seven subscales compared to healthy controls (p < 0.001) but lower scores than BPD patients (p < 0.001). With respect to the seven subscales, the largest differences between ADHD and BPD patients were found with respect to self-destruction (d = 1.12) and affect dysregulation (d = 0.90), whereas the smallest difference was found with respect to loneliness (d = 0.36). In females, the BSL subscales "loneliness" and "hostility" did not differentiate between BPD and ADHD. Borderline typical symptoms are common in adult patients with ADHD but seem to be less pronounced than in patients with BPD. Females with ADHD and BPD share more clinical features than males. However, symptoms of self-destruction and affect dysregulation appear to be more severe in BPD patients.     

Analysis of TBX1 variation in patients with psychotic and affective disorders

A significant portion of patients with 22q11 deletion syndrome (22q11DS) develop psychiatric disorders, including schizophrenia and other psychotic and affective symptoms, and the responsible gene/s are assumed to also play a significant role in the etiology of nonsyndromic psychiatric disease. The most common psychiatric diagnosis among patients with 22q11DS is schizophrenia, thought to result from neurotransmitter imbalances and also from disturbed brain development. Several genes in the 22q11 region with known or suspected roles in neurotransmitter metabolism have been analyzed in patients with isolated schizophrenia; however, their contribution to the disease remains controversial. Haploinsufficiency of the TBX1 gene has been shown to be sufficient to cause the core physical malformations associated with 22q11DS in mice and humans and via abnormal brain development could contribute to 22q11DS-related and isolated psychiatric disease. 22q11DS populations also have increased rates of psychiatric conditions other than schizophrenia, including mood disorders. We therefore analyzed variations at the TBX1 locus in a cohort of 446 white patients with psychiatric disorders relevant to 22q11DS and 436 ethnically matched controls. The main diagnoses included schizophrenia (n = 226), schizoaffective disorder (n = 67), bipolar disorder (n = 82), and major depressive disorder (n = 29). We genotyped nine tag SNPs in this sample but did not observe significant differences in allele or haplotype frequencies in any of the analyzed groups (all affected, schizophrenia and schizoaffective disorder, schizophrenia alone, and bipolar disorder and major depressive disorder) compared with the control group. Based on these results we conclude that TBX1 variation does not make a strong contribution to the genetic etiology of nonsyndromic forms of psychiatric disorders commonly seen in patients with 22q11DS.     

Aberrant Methylation of Gene Associated CpG Sites Occurs in Borderline Personality Disorder

Borderline personality disorder (BPD) is a complex psychiatric disease with an increased impact in the last years. While the diagnosis and therapy are well established, little is known on the pathogenesis of borderline personality disorder. Previously, a significant increase in DNA methylation of relevant neuropsychiatric genes in BPD patients has been reported. In our study we performed genome wide methylation analysis and revealed specific CpG sites that exhibited increased methylation in 24 female BPD patients compared to 11 female healthy controls. Bead chip technology and quantitative bisulfite pyrosequencing showed a significantly increased methylation at CpG sites of APBA2 (1.1 fold) and APBA3 (1.1 fold), KCNQ1 (1.5 fold), MCF2 (1.1 fold) and NINJ2 (1.2 fold) in BPD patients. For the CpG sites of GATA4 and HLCS an increase in DNA methylation was observed, but was only significant in the bead chip assay. Moreover genome wide methylation levels of blood samples of BPD patients and control samples are similar. In summary, our results show a significant 1.26 fold average increase in methylation at the analyzed gene associated CpG sites in the blood of BPD patients compared to controls samples (p<0.001). This data may provide new insights into epigenetic mechanisms underlying the pathogenesis of BPD.     

Genome scan meta-analysis of schizophrenia and bipolar disorder,part III: Bipolar disorder

Genome scans of bipolar disorder (BPD) have not produced consistent evidence for linkage. The rank-based genome scan meta-analysis (GSMA) method was applied to 18 BPD genome scan data sets in an effort to identify regions with significant support for linkage in the combined data. The two primary analyses considered available linkage data for “very narrow” (i.e., BP-I and schizoaffective disorder–BP) and “narrow” (i.e., adding BP-II disorder) disease models, with the ranks weighted for sample size. A “broad” model (i.e., adding recurrent major depression) and unweighted analyses were also performed. No region achieved genomewide statistical significance by several simulation-based criteria. The most significant P values (<.01) were observed on chromosomes 9p22.3-21.1 (very narrow), 10q11.21-22.1 (very narrow), and 14q24.1-32.12 (narrow). Nominally significant P values were observed in adjacent bins on chromosomes 9p and 18p-q, across all three disease models on chromosomes 14q and 18p-q, and across two models on chromosome 8q. Relatively few BPD pedigrees have been studied under narrow disease models relative to the schizophrenia GSMA data set, which produced more significant results. There was no overlap of the highest-ranked regions for the two disorders. The present results for the very narrow model are promising but suggest that more and larger data sets are needed. Alternatively, linkage might be detected in certain populations or subsets of pedigrees. The narrow and broad data sets had considerable power, according to simulation studies, but did not produce more highly significant evidence for linkage. We note that meta-analysis can sometimes provide support for linkage but cannot disprove linkage in any candidate region.     

Characterization and Modeling of Intermittent Locomotor Dynamics in Clock Gene-Deficient Mice

The scale-invariant and intermittent dynamics of animal behavior are attracting scientific interest. Recent findings concerning the statistical laws of behavioral organization shared between healthy humans and wild-type mice (WT) and their alterations in human depression patients and circadian clock gene (Period 2; Per2) mutant mice indicate that clock genes play functional roles in intermittent, ultradian locomotor dynamics. They also claim the clinical and biological importance of the laws as objective biobehavioral measures or endophenotypes for psychiatric disorders. In this study, to elucidate the roles of breakdown of the broader circadian regulatory circuit in intermittent behavioral dynamics, we studied the statistical properties and rhythmicity of locomotor activity in Per2 mutants and mice deficient in other clock genes (Bmal1, Clock). We performed wavelet analysis to examine circadian and ultradian rhythms and estimated the cumulative distributions of resting period durations during which locomotor activity levels are continuously lower than a predefined threshold value. The wavelet analysis revealed significant amplification of ultradian rhythms in the BMAL1-deficient mice, and instability in the Per2 mutants. The resting period distributions followed a power-law form in all mice. While the distributions for the BMAL1-deficient and Clock mutant mice were almost identical to those for the WT mice, with no significant differences in their parameter (power-law scaling exponent), only the Per2 mutant mice showed consistently and significantly lower values of the scaling exponent, indicating the increased intermittency in ultradian locomotor dynamics. Furthermore, based on a stochastic priority queuing model, we explained the power-law nature of resting period distributions, as well as its alterations shared with human depressive patients and Per2 mutant mice. Our findings lead to the development of a novel mathematical model for abnormal behaviors in psychiatric disorders.     

Epigenetic deregulation of imprinting in congenital diseases of aberrant growth

Human chromosome 11p15 comprises two imprinted domains important in the control of fetal and postnatal growth. Novel studies establish that imprinting at one of these, the IGF2-H19 domain, is epigenetically deregulated (with loss of DNA methylation) in Silver-Russell Syndrome (SRS), a congenital disease of growth retardation and asymmetry. Previously, the exact opposite epigenetic alteration (gain of DNA methylation) had been detected at the domain's 'imprinting control region' (ICR) in patients with Beckwith-Wiedemann Syndrome (BWS), a complex disorder of fetal overgrowth. However, more frequently, BWS is caused by loss of DNA methylation at the ICR that regulates the second imprinted domain at 11p15. Interestingly, a similar epigenetic alteration (with loss of methylation) at a putative ICR on human chromosome 6q24, is involved in transient neonatal diabetes mellitus (TNDM), a congenital disease with intrauterine growth retardation and a transient lack of insulin. Thus, fetal and postnatal growth is epigenetically controlled by different ICRs, at 11p15 and other chromosomal regions.     

A Novel Analytical Framework for Dissecting the Genetic Architecture of Behavioral Symptoms in Neuropsychiatric Disorders

Background

For diagnosis of neuropsychiatric disorders, a categorical classification system is often utilized as a simple way for conceptualizing an often complex clinical picture. This approach provides an unsatisfactory model of mental illness, since in practice patients do not conform to these prototypical diagnostic categories. Family studies show notable familial co-aggregation between schizophrenia and bipolar illness and between schizoaffective disorders and both bipolar disorder and schizophrenia, revealing that mental illness does not conform to such categorical models and is likely to follow a continuum encompassing a spectrum of behavioral symptoms.

Results and Methodology

We introduce an analytic framework to dissect the phenotypic heterogeneity present in complex psychiatric disorders based on the conceptual paradigm of a continuum of psychosis. The approach identifies subgroups of behavioral symptoms that are likely to be phenotypically and genetically homogenous. We have evaluated this approach through analysis of simulated data with simulated behavioral traits and predisposing genetic factors. We also apply this approach to a psychiatric dataset of a genome scan for schizophrenia for which extensive behavioral information was collected for each individual patient and their families. With this approach, we identified significant evidence for linkage among depressed individuals with two distinct symptom profiles, that is individuals with sleep disturbance symptoms with linkage on chromosome 2q13 and also a mutually exclusive group of individuals with symptoms of concentration problems with linkage on chromosome 2q35. In addition we identified a subset of individuals with schizophrenia defined by language disturbances with linkage to chromosome 2p25.1 and a group of patients with a phenotype intermediate between those of schizophrenia and schizoaffective disorder with linkage to chromosome 2p21.

Conclusions

The findings presented are novel and demonstrate the efficacy of this approach in detection of genes underlying such complex human disorders as schizophrenia and depression.     

Identification of Chromosomal Bands Replicating Early in the S Phase of Normal Human Fibroblasts

Normal human fibroblasts (NHF1) were released from confluence arrest (G₀) and replated in medium containing bromodeoxyuridine (BrdU) and aphidicolin. Despite severe reduction in the rate of DNA synthesis by aphidicolin, cells reentering the cell cycle incorporated BrdU at regions of the human genome that replicated very early in S phase. After removal of aphidicolin and BrdU from the tissue culture medium, cells were collected in mitosis. Q-banding with 4′,6-diamidino-2-phenylindole/actinomycin D was used to identify metaphase chromosomes. A monoclonal anti-BrdU antibody and a fluorescein isothiocyanate (FITC)-conjugated goat anti-mouse antibody were used to identify the BrdU-labeled sites. The criterion for scoring DNA replication sites was the detection of FITC fluorescence at homologous regions of both sister chromatids. Early replicating regions mapped within R-bands, but not all R-bands incorporated BrdU. Chromosomal bands 1p36.1, 8q24.1, 12q13, 15q15, 15q22, and 22q13 were labeled in 53% or more of the copies of these chromosomes in the data set, suggesting that these sites replicated very early in S phase. Chromosomal band 15q22 was the most frequently labeled site (64%), which indicates that it contains some of the earliest replicating sequences in normal human fibroblasts.     

Experimental Evidence for the Involvement of PDLIM5 in Mood Disorders in Hetero Knockout Mice

Background

Reports indicate that PDLIM5 is involved in mood disorders. The PDLIM5 (PDZ and LIM domain 5) gene has been genetically associated with mood disorders; it’s expression is upregulated in the postmortem brains of patients with bipolar disorder and downregulated in the peripheral lymphocytes of patients with major depression. Acute and chronic methamphetamine (METH) administration may model mania and the evolution of mania into psychotic mania or schizophrenia-like behavioral changes, respectively.

Methods

To address whether the downregulation of PDLIM5 protects against manic symptoms and cause susceptibility to depressive symptoms, we evaluated the effects of reduced Pdlim5 levels on acute and chronic METH-induced locomotor hyperactivity, prepulse inhibition, and forced swimming by using Pdlim5 hetero knockout (KO) mice.

Results

The homozygous KO of Pdlim5 is embryonic lethal. The effects of METH administration on locomotor hyperactivity and the impairment of prepulse inhibition were lower in Pdlim5 hetero KO mice than in wild-type mice. The transient inhibition of PDLIM5 (achieved by blocking the translocation of protein kinase C epsilon before the METH challenge) had a similar effect on behavior. Pdlim5 hetero KO mice showed increased immobility time in the forced swimming test, which was diminished after the chronic administration of imipramine. Chronic METH treatment increased, whereas chronic haloperidol treatment decreased, Pdlim5 mRNA levels in the prefrontal cortex. Imipramine increased Pdlim5 mRNA levels in the hippocampus.

Conclusion

These findings are partially compatible with reported observations in humans, indicating that PDLIM5 is involved in psychiatric disorders, including mood disorders.     

Evaluation of toluene dependence and cross-sensitization to diazepam

Acute effects of the abused inhalant toluene resemble those of CNS depressant drugs. Since abuse of toluene involves repeated use, the purpose of the present study was to evaluate the effects of repeated or continuous exposure to toluene and to compare these effects to those of other inhalants and depressants. In experiment 1, ICR mice exposed continuously to 250 ppm toluene via inhalation for four days developed mild dependence upon termination that was characterized by an increase in severity of handling-induced convulsions. However, administration of the convulsants, N-methyl-D-aspartate (NMDA) or pentylenetetrazole (PTZ), did not differentially affect toluene- vs. air-exposed mice. In experiment 2, CFW mice (but not ICR mice) developed cross-sensitization to the initial locomotor stimulatory effects of toluene following four days of injections with 10 mg/kg/day diazepam. Previous findings have shown that 1,1,1-trichloroethane (TCE) produced robust dependence and cross-sensitization to diazepam's locomotor effects when tested under similar conditions. The present results suggest that the dependence and cross-sensitization with diazepam produced by toluene are milder than those induced by TCE. Further, these studies add to increasing evidence that abused inhalants do not have identical pharmacological effects.