Klinefelter's syndrome (XXY) as a genetic model for psychotic disorders

Klinefelter Syndrome: A Genetic Disorder Leading to Neuroendocrine Modifications and Psychopathological Vulnerabilities in Children-A Literature Review and Case Report

Klinefelter syndrome (KS), characterized by an additional X-chromosome in males, manifests in a wide range of neuroendocrine and psychiatric symptoms. Individuals with KS often face increased risks of hormonal dysfunction, leading to depression and anxiety, although extended research during pediatric and adolescent age is still limited. This critical phase, decisive for KS children, is influenced by a combination of genetic, environmental and familial factors, which impact brain plasticity. In this report, we reviewed, in a narrative form, the crucial KS psychopathological hallmarks in children. To better describe neuroendocrine and neuropsychiatric outcomes in children with KS, we presented the case of an 11-year-old prepubertal child with mosaic KS who was referred to our Center of Developmental Psychopathology due to a decline in his academic performance, excessive daytime fatigue and increased distractibility over the past few months. Family history revealed psychiatric conditions among first- and second-degree relatives, including recently divorced parents and a 15-year-old sister. Early-onset persistent depressive disorder and anxious traits were diagnosed. Timely identification of susceptible children, with thorough examination of familial psychiatric history, environmental influences and neurocognitive profile, alongside targeted interventions, could potentially mitigate lifelong psychopathology-related disabilities in pediatric and adolescent KS cases, including those with mosaic KS.

Tatton-Brown-Rahman syndrome: Novel pathogenic variants and new neuroimaging findings

Tatton-Brown-Rahman syndrome (TBRS) or DNMT3A-overgrowth syndrome is characterized by overgrowth and intellectual disability associated with minor dysmorphic features, obesity, and behavioral problems. It is caused by variants of the DNMT3A gene. We report four patients with this syndrome due to de novo DNMT3A pathogenic variants, contributing to a deeper understanding of the genetic basis and pathophysiology of this autosomal dominant syndrome. Clinical and magnetic resonance imaging assessments were also performed. All patients showed corpus callosum anomalies, small posterior fossa, and a deep left Sylvian fissure; as well as asymmetry of the uncinate and arcuate fascicles and marked increased cortical thickness. These results suggest that structural neuroimaging anomalies have been previously overlooked, where corpus callosum and brain tract alterations might be unrecognized neuroimaging traits of TBRS syndrome caused by DNMT3A variants.

Executive Dysfunction in Klinefelter Syndrome: Associations With Brain Activation and Testicular Failure

CONTEXT

Executive dysfunction is a well-recognized component of the cognitive phenotype of Klinefelter syndrome (KS), yet the neural basis of KS-associated cognitive weaknesses, and their association with testicular failure is unknown.

OBJECTIVE

We investigated executive function, brain activation, and pubertal development in adolescents with and without KS.

METHODS

Forty-three adolescents with KS (mean age 12.3 ± 2.3 years) and 41 typically developing boys (mean age 11.9 ± 1.8 years) underwent pubertal evaluation, behavioral assessment, and completed functional magnetic resonance imaging (fMRI) as they performed an executive function task, the go/no-go task. Group differences in activation were examined. Associations among activation, executive function, and pubertal development measures were tested in secondary analyses.

RESULTS

Boys with KS exhibited reduced executive function, as well as lower activation in brain regions subserving executive function, including the inferior frontal gyrus, anterior insula, dorsal anterior cingulate cortex, and caudate nucleus. Secondary analyses indicated that the magnitude of activation differences in boys with KS was associated with severity of pubertal developmental delay, as indexed by lower testosterone (t(36) = 2.285; P = .028) and lower testes volume (t(36) = 2.238; P = .031). Greater parent-reported attention difficulties were additionally associated with lower testicular volume (t(36) = -2.028; P = .050).

CONCLUSION

These findings indicate a neural basis for executive dysfunction in KS and suggest alterations in pubertal development may contribute to increased severity of this cognitive weakness. Future studies that examine whether these patterns change with testosterone replacement therapy are warranted.

Biological hypotheses, risk factors, and biomarkers of schizophrenia

Both the discovery of biomarkers of schizophrenia and the verification of biological hypotheses of schizophrenia are an essential part of the process of understanding the etiology of this mental disorder. Schizophrenia has long been considered a neurodevelopmental disease whose symptoms are caused by impaired synaptic signal transduction and brain neuroplasticity. Both the onset and chronic course of schizophrenia are associated with risk factors-induced disruption of brain function and the establishment of a new homeostatic setpoint characterized by biomarkers. Different risk factors and biomarkers can converge to the same symptoms of schizophrenia, suggesting that the primary cause of the disease can be highly individual. Schizophrenia-related biomarkers include measurable biochemical changes induced by stress (elevated allostatic load), mitochondrial dysfunction, neuroinflammation, oxidative and nitrosative stress, and circadian rhythm disturbances. Here is a summary of selected valid biological hypotheses of schizophrenia formulated based on risk factors and biomarkers, neurodevelopment, neuroplasticity, brain chemistry, and antipsychotic medication. The integrative neurodevelopmental-vulnerability-neurochemical model is based on current knowledge of the neurobiology of the onset and progression of the disease and the effects of antipsychotics and psychotomimetics and reflects the complex and multifactorial nature of schizophrenia.

Triple X syndrome: Psychiatric disorders and impaired social functioning as a risk factor

BACKGROUND

Women with triple X syndrome (TXS) have an extra X chromosome. TXS appeared to be associated with psychiatric disorders in biased or underpowered studies.

AIM

This study aims to describe the prevalence of psychiatric disorders in adults with TXS in a relatively large and less biased group of participants.

METHOD

In this cross-sectional study, data were collected from 34 women with TXS (mean age = 32.9; s.d. = 13.1) and 31 controls (mean age = 34.9; s.d. = 13.7). Psychiatric disorders were assessed using the MINI International Neuropsychiatric Interview (MINI) and the adult behavior checklist (ABCL). Trait and state anxiety were assessed using the State-Trait Anxiety Inventory.

RESULTS

In the TXS group, MINI results showed a higher prevalence of major depressive episodes (43.3%), psychotic disorders (29.4%), and suicidality (23.5%). Only 50% of the TXS group earned a normal score for the total syndrome score using the ABCL. In addition, levels of trait anxiety were higher in the TXS group. Only three women in each group received psychotropic medication. Impaired social functioning appeared to represent a major risk factor in TXS as regards psychotic, affective disorders, trait anxiety, and low self-esteem.

CONCLUSIONS

Women with TXS are vulnerable to developing psychiatric disorders, and women with both TXS and impaired social functioning are even more vulnerable.

Klinefelter syndrome mosaicism in boys with neurodevelopmental disorders: a cohort study and an extension of the hypothesis

Background

Klinefelter syndrome is a common chromosomal (aneuploidy) disorder associated with an extra X chromosome in males. Regardless of numerous studies dedicated to somatic gonosomal mosaicism, Klinefelter syndrome mosaicism (KSM) has not been systematically addressed in clinical cohorts. Here, we report on the evaluation of KSM in a large cohort of boys with neurodevelopmental disorders. Furthermore, these data have been used for an extension of the hypothesis, which we have recently proposed in a report on Turner’s syndrome mosaicism in girls with neurodevelopmental disorders.

Results

Klinefelter syndrome-associated karyotypes were revealed in 49 (1.1%) of 4535 boys. Twenty one boys (0.5%) were non-mosaic 47,XXY individuals. KSM was found in 28 cases (0.6%) and manifested as mosaic aneuploidy (50,XXXXXY; 49,XXXXY; 48,XXXY; 48,XXYY; 47,XXY; and 45,X were detected in addition to 47,XXY/46,XY) and mosaic supernumerary marker chromosomes derived from chromosome X (ring chromosomes X and rearranged chromosomes X). It is noteworthy that KSM was concomitant with Rett-syndrome-like phenotypes caused by MECP2 mutations in 5 boys (0.1%).

Conclusion

Our study provides data on the occurrence of KSM in neurodevelopmental disorders among males. Accordingly, it is proposed that KSM may be a possible element of pathogenic cascades in psychiatric and neurodegenerative diseases. These observations allowed us to extend the hypothesis proposed in our previous report on the contribution of somatic gonosomal mosaicism (Turner’s syndrome mosaicism) to the etiology of neurodevelopmental disorders. Thus, it seems to be important to monitor KSM (a possible risk factor or a biomarker for adult-onset multifactorial brain diseases) and analysis of neuromarkers for aging in individuals with Klinefelter syndrome. Cases of two or more supernumerary chromosomes X were all associated with KSM. Finally, Rett syndrome-like phenotypes associated with KSM appear to be more common in males with neurodevelopmental disorders than previously recognized.

Intelligence Quotient Variability in Klinefelter Syndrome Is Associated With GTPBP6 Expression Under Regulation of X-Chromosome Inactivation Pattern

Klinefelter syndrome (KS) displays a broad dysmorphological, endocrinological, and neuropsychological clinical spectrum. We hypothesized that the neurocognitive dysfunction present in KS relies on an imbalance in X-chromosome gene expression. Thus, the X-chromosome inactivation (XCI) pattern and neurocognitive X-linked gene expression were tested and correlated with intelligence quotient (IQ) scores. We evaluated 11 KS patients by (a) IQ assessment, (b) analyzing the XCI patterns using both HUMARA and ZDHHC15 gene assays, and (c) blood RT-qPCR to investigate seven X-linked genes related to neurocognitive development (GTPBP6, EIF2S3, ITM2A, HUWE1, KDM5C, GDI1, and VAMP7) and XIST in comparison with 14 (male and female) controls. Considering IQ 80 as the standard minimum reference, we verified that the variability in IQ scores in KS patients seemed to be associated with the XCI pattern. Seven individuals in the KS group presented a random X-inactivation (RXI) and lower average IQ than the four individuals who presented a skewed X-inactivation (SXI) pattern. The evaluation of gene expression showed higher GTPBP6 expression in KS patients with RXI than in controls (p = 0.0059). Interestingly, the expression of GTPBP6 in KS patients with SXI did not differ from that observed in controls. Therefore, our data suggest for the first time that GTPBP6 expression is negatively associated with full-scale IQ under the regulation of the type of XCI pattern. The SXI pattern may regulate GTPBP6 expression, thereby dampening the impairment in cognitive performance and playing a role in intelligence variability in individuals with KS, which warrants further mechanistic investigations.

Cortical gray matter structure in boys with Klinefelter syndrome

Klinefelter syndrome (KS, 47,XXY) is a common sex chromosome aneuploidy in males that is associated with a wide range of cognitive, social and emotional characteristics. The neural bases of these symptoms, however, are unclear. Brain structure in 19 pre- or early-pubertal boys with KS (11.5 ± 1.8 years) and 22 typically developing (control) boys (8.1 ± 2.3 years) was examined using surface-based analyses of cortical gray matter volume, thickness and surface area. Boys in the KS group were treatment-naïve with respect to testosterone replacement therapy. Reduced volume in the insula and dorsomedial prefrontal cortex was observed in the KS relative to the TD group, as well as increased volume in the parietal, occipital and motor regions. Further inspection of surface-based metrics indicated that whereas KS-associated increases in volume were driven by differences in thickness, KS-associated reductions in volume were associated with decreases in surface area. Exploratory analyses additionally indicated several correlations between brain structure and behavior, providing initial support for a neural basis of cognitive and emotional symptoms of this condition. Taken together, these data add support for a neuroanatomical phenotype of KS and extend previous studies through clarifying the precise neuroanatomical structural characteristics of that give rise to volumetric alterations.

Social Management Training in Males With 47,XXY (Klinefelter Syndrome): A Pilot Study of a Neurocognitive-Behavioral Treatment Targeting Social, Emotional, and Behavioral Problems

Klinefelter syndrome (47,XXY) is associated with problems in social interaction and behavioral adaptation. Sixteen adolescents and adult men with 47,XXY enrolled in a pilot-study evaluating the effectiveness of Social Management Training (SMT), a novel neurocognitive-behavioral treatment program targeted at improving social, emotional, and behavioral functioning. Participants reported improved emotional stability from pre- to post-test (5 months). Informants reported reductions in internalizing and externalizing symptoms, including improvement in self-regulation. Although informants did not report changes in autism-like symptoms, increased awareness of social challenges was found. SMT may improve emotional stability, self-regulation, and self-reflection in people males with Klinefelter syndrome. This potentially efficacious treatment approach may prove to be a promising psychosocial therapeutic intervention for this population.

Klinefelter syndrome or testicular dysgenesis: Genetics, endocrinology, and neuropsychology

Klinefelter syndrome (47,XXY) is a frequent chromosomal disorder among males, often presenting with hypergonadotropic hypogonadism, small firm testicles, metabolic disorders, neurocognitive challenges, and increased height. Neurologic disorders such as epilepsy, seizures, and tremor as well as psychiatric disorders are also seen more frequently. The neurocognitive deficits seen are present in many areas of cognition, typically affecting general cognitive abilities, language, and executive functioning. Also, social dysfunction is frequent. Dyslexia is present in more than half of all males. Brain imaging studies generally show a typical pattern, with many nuclei and brain areas being smaller than among controls. However, it has not been possible to link the brain alterations found in imaging studies with the neurocognitive profile. The genetics underlying the phenotypic traits found among males with Klinefelter syndrome still remains to be elucidated; however, recent studies have described pervasive changes in the methylome and transcriptome and new and interesting candidate genes have been pinpointed, but their involvement in the phenotype of Klinefelter syndrome has not been proven.

Executive function in XXY: Comparison of performance-based measures and rating scales

Few studies have systematically assessed executive functioning (EF) skills in boys with XXY, and these are limited by small samples and restricted EF assessment. This study used a broader battery of performance-based measures as well as parent-rating scales of EF in 77 boys and adolescents with XXY (mean age = 12.5 years), recruited from a clinical trial and an outpatient clinic. Exploratory factor analyses were used to create EF domains from performance-based measures, and similar domains were measured using the Behavior Rating Inventory of Executive Function and Conners Parent-Rating Scales. The boys with XXY showed a distinct EF profile, with the greatest deficit in attention and more moderate deficits in working memory, switching, and planning/problem solving. Parent ratings showed similar challenges, as well as impaired inhibition. Independent sample t-tests showed no difference on performance measures between boys diagnosed or not diagnosed with attention-deficit/hyperactivity disorder (ADHD), although parents of boys diagnosed with ADHD reported more difficulties. There were no differences on performance-based tests between those diagnosed pre- and postnatally, although parents of postnatally diagnosed boys reported more metacognitive problems. Language deficits, cognition, and socio-economic status did not account for EF deficits.

Sex chromosome aneuploidy alters the relationship between neuroanatomy and cognition

Sex chromosome aneuploidy (SCA) increases the risk for cognitive deficits, and confers changes in regional cortical thickness (CT) and surface area (SA). Neuroanatomical correlates of inter-individual variation in cognitive ability have been described in health, but are not well-characterized in SCA. Here, we modeled relationships between general cognitive ability (estimated using full-scale IQ [FSIQ] from Wechsler scales) and regional estimates of SA and CT (from structural MRI scans) in both aneuploid (28 XXX, 55 XXY, 22 XYY, 19 XXYY) and typically-developing euploid (79 XX, 85 XY) individuals. Results indicated widespread decoupling of normative anatomical-cognitive relationships in SCA: we found five regions where SCA significantly altered SA-FSIQ relationships, and five regions where SCA significantly altered CT-FSIQ relationships. The majority of areas were characterized by the presence of positive anatomy-IQ relationships in health, but no or slightly negative anatomy-IQ relationships in SCA. Disrupted anatomical-cognitive relationships generalized from the full cohort to karyotypically defined subcohorts (i.e., XX-XXX; XY-XYY; XY-XXY), demonstrating continuity across multiple supernumerary SCA conditions. As the first direct evidence of altered regional neuroanatomical-cognitive relationships in supernumerary SCA, our findings shed light on potential genetic and structural correlates of the cognitive phenotype in SCA, and may have implications for other neurogenetic disorders.

Lost in translational biology: Understanding sex differences to inform studies of diseases of the nervous system

Female and male humans are different. As simple and obvious as that statement is, in biomedical research there has been an historical tendency to either not consider sex at all or to only use males in clinical and in preclinical model system studies. The result is a large volume of research that reflects the average biology and pathology of males even though we know that disease risk, presentation, and response to therapies can be different between females and males. This is true, albeit to differing degrees, for virtually all neurological and psychiatric diseases. However, the days of ignoring sex as a biological variable are over - both because of the realization that genetic sex impacts brain function, and because of the 2014 mandate by the U.S. National Institutes of Health that requires that "sex as a biological variable" be addressed in each grant application. This review is written for neuroscientists who may not have considered sex as a biological variable previously but who now are navigating the best way to adapt their research programs to consider this important biology. We first provide a brief overview of the evidence that male versus female differences in the brain are biologically and clinically meaningful. We then present some fundamental principles that have been forged by a dedicated but small group of ground-breaking researchers along with a description of tools and model systems for incorporating a sex differences component into a research project. Finally, we will highlight some key technologies that, in the coming years, are likely to provide critical information about sex differences in the human brain.

Neuropsychiatric Aspects in Men with Klinefelter Syndrome

BACKGROUND AND OBJECTIVE

Klinefelter Syndrome (KS) is the most common sex chromosome aneuploidy (47, XXY) and cause of male hypergonadotropic hypogonadism. It is characterized by an extreme clinical heterogeneity in presentation, including infertility, hypogonadism, language delay, metabolic comorbidities, and neurocognitive and psychiatric disorders. Since testosterone is known to have organizational, neurotrophic and neuroprotective effects on brain, the condition of primary hypogonadism could play a role. Moreover, given that KS subjects have an additional X, genes on the extra-chromosome could also exert a significant impact. The aim of this narrative review is to analyze the available literature on the relationship between KS and neuropsychiatric disorders.

METHODS

To extend to the best of published literature on the topic, appropriate keywords and MeSH terms were identified and searched in Pubmed. Finally, references of original articles and reviews were examined.

RESULTS

Both morphological and functional studies focusing on the brain showed that there were important differences in brain structure of KS subjects. Different psychiatric disorders such as Schizophrenia, autism, attention deficit hyperactivity disorder, depression and anxiety were frequently reported in KS patients according to a broad spectrum of phenotypes. T supplementation (TRT) was not able to improve the psychotic disorders in KS men with or without overt hypogonadism.

CONCLUSION

Although the risk of psychosis, depression and autism is increased in subjects with KS, no definitive evidence has been found in studies aiming at identifying the relationship between aneuploidy, T deficit and the risk of psychiatric and cognitive disorders in subjects affected by KS.

Androgen treatment effects on hippocampus structure in boys with Klinefelter syndrome

Klinefelter syndrome (KS, 47,XXY) is the most common sex chromosome aneuploidy in males. A variety of complex clinical needs is associated with KS, including physical, cognitive and psychosocial impairments. Standard treatment for KS consists of androgen replacement therapy in adolescence to offset testosterone deficiency. Such treatment has a beneficial effect on the physical and behavioral manifestations of this syndrome. Whether androgen supplementation has a significant influence on the brain, however, is unknown. In the current study, we examined regional gray matter volume in boys with KS to assess whether treatment with oxandrolone, a synthetic hormone analog of testosterone, was associated with structural changes in the brain. Specifically, we focused our investigation on the hippocampus, given (1) its involvement in KS, and (2) the high concentration of androgen receptors found in this region. Structural magnetic resonance imaging data was acquired from a subsample of boys who completed a 2-year double-blind clinical trial in which patients were randomized to treatment with oxandrolone or to placebo, as well as from a sample of typically developing (TD) boys. Group differences in hippocampal volume were examined. A significant main effect of group was observed. Pairwise comparisons indicated smaller hippocampal volume in the placebo group relative to the oxandrolone group, as well as smaller volume in the placebo group relative to the TD control group. No difference in volume was observed between the treatment and TD groups. Moreover, across KS subgroups, a significant positive association was observed between hippocampus volume and performance on a spatial memory task, indicating treatment-based changes in brain structure may underlie cognitive change. These findings confirm prior reports implicating a role of the hippocampus in KS and are important in extending previous research by demonstrating a significant effect of androgens on brain structure.

The Sex Chromosome Hypothesis of Schizophrenia: Alive, Dead, or Forgotten? A Commentary and Review

The X chromosome has long been an intriguing site for harboring genes that have importance in brain development and function. It has received the most attention for having specific genes underlying the X-linked inherited intellectual disabilities, but has also been associated with schizophrenia in a number of early studies. An X chromosome hypothesis for a genetic predisposition for schizophrenia initially came from the X chromosome anomaly population data showing an excess of schizophrenia in Klinefelter's (XXY) males and triple X (XXX) females. Crow and colleagues later expanded the X chromosome hypothesis to include the possibility of a locus on the Y chromosome and, specifically, genes on X that escaped inactivation and are X-Y homologous loci. Some new information about possible risk loci on these chromosomes has come from the current large genetic consortia genome-wide association studies, suggesting that perhaps this hypothesis needs to be revisited for some schizophrenias. The following commentary reviews the early and more recent literature supporting or refuting this dormant hypothesis and emphasizes the possible candidate genes still of interest that could be explored in further studies.

Sex chromosome trisomies are not associated with atypical lateralization for language

AIM

To test the hypothesis that sex chromosome trisomies (SCTs) are associated with reduced left lateralization for language.

METHOD

Using a cross-sectional design, language laterality was measured during an animation description task using functional transcranial Doppler ultrasonography. Data were available for 75 children with an SCT (47,XXX females [n=26], 47,XXY males [n=25], 47,XYY males [n=24]; mean age 11y 4mo [SD 3y 10mo]) and 132 comparison children with typical karyotypes (69 males, 63 females; mean age 9y 1mo [SD 1y 7mo]).

RESULTS

Lateralization for language did not differ between the SCT and comparison groups, either in mean laterality index or relative frequency of each laterality category. There were no differences when splitting the group with an SCT by trisomy. Handedness showed no group effects.

INTERPRETATION

Our data provide no evidence for disrupted lateralization for language in SCTs. The brain basis of the cognitive phenotype in SCTs is unlikely to be a failure of the left hemisphere to specialize for language, as previously suggested.

WHAT THIS PAPER ADDS

Children with a sex chromosome trisomy (SCT) have typically lateralized language. This disproves theories linking language problems to hemispheric specialization in SCTs.

Like father like daughter: sex-specific parent-of-origin effects in the transmission of liability for psychotic symptoms to offspring

Children of parents with major mood and psychotic disorders are at increased risk of psychopathology, including psychotic symptoms. It has been suggested that the risk of psychosis may be more often transmitted from parent to opposite-sex offspring (e.g., from father to daughter) than to same-sex offspring (e.g., from father to son). To test whether sex-specific transmission extends to early manifestations of psychosis, we examined sex-specific contributions to psychotic symptoms among offspring of mothers and fathers with depression, bipolar disorder and schizophrenia. We assessed psychotic symptoms in 309 offspring (160 daughters and 149 sons) aged 8-24 years (mean=13.1, s.d.=4.3), of whom 113 had a mother with schizophrenia, bipolar disorder or major depression and 43 had a father with schizophrenia, bipolar disorder or major depression. In semi-structured interviews, 130 (42%) offspring had definite psychotic symptoms established and confirmed by psychiatrists on one or more assessments. We tested the effects of mental illness in parents on same-sex and opposite-sex offspring psychotic symptoms in mixed-effect logistic regression models. Psychotic symptoms were more prevalent among daughters of affected fathers and sons of affected mothers than among offspring of the same sex as their affected parent. Mental illness in the opposite-sex parent increased the odds of psychotic symptoms (odds ratio (OR)=2.65, 95% confidence interval (CI) 1.43-4.91, P=0.002), but mental illness in the same-sex parent did not have a significant effect on psychotic symptoms in offspring (OR=1.13, 95% CI 0.61-2.07, P=0.697). The opposite-sex-specific parent-of-origin effects may suggest X chromosome-linked genetic transmission or inherited chromosomal modifications in the etiology of psychotic symptoms.

Behavioral and psychological features in girls and women with triple-X syndrome

Triple-X syndrome is a common sex chromosome aneuploidy, which appears in 1 out of 1,000 females. The aim of our study was to describe the behavioral features of a large group of girls and women with triple-X in comparison to a control group. A total of 72 subjects with triple-X and 69 subjects of an age-matched control group were included. Psychological and behavioral questionnaires were allocated to three age groups, representing a range of ages from young childhood to adulthood. Regarding the females between 4 and 7 years of age, we found significant differences for social problems, attention problems, and school performance. For the age group 8-17 years, we found larger significant differences for the majority of the scales listed in the child behavior checklist. The most significant differences (p < .001) were from total behavior problems, internalizing problems, and four other scales. Young females with triple-X have significantly lower general self-esteem, especially concerning school and family. In the adults, there were significant differences concerning psychological symptoms and distress, with higher scores in the triple-X subjects. Regardless, their mean scores were still in the normal range. We did not find clinical evidence for more than 50% of the triple-X females in any age group, indicating that approximately half of them do not have behavioral problems, and that more than 60% do not differ in their competence from the control group. However, our findings suggest that triple-X influences mental health and the overall well-being of the individuals across their whole life spans.

Klinefelter Syndrome: Integrating Genetics, Neuropsychology, and Endocrinology

Although first identified over 70 years ago, Klinefelter syndrome (KS) continues to pose substantial diagnostic challenges, as many patients are still misdiagnosed, or remain undiagnosed. In fact, as few as 25% of patients with KS are accurately diagnosed and most of these diagnoses are not made until adulthood. Classic characteristics of KS include small testes, infertility, hypergonadothropic hypogonadism, and cognitive impairment. However, the pathophysiology behind KS is not well understood, although genetic effects are also thought to play a role. For example, recent developments in genetics and genomics point to a fundamental change in our understanding of KS, with global epigenetic and RNA expression changes playing a central role for the phenotype. KS is also associated with more general health markers, including higher morbidity and mortality rates and lower socioeconomic status (which likely affect both morbidity and mortality). In addition, hypogonadism is associated with greater risk of metabolic syndrome, type 2 diabetes, cardiovascular disease, breast cancer, and extragonadal germ cell tumors. Medical treatment typically focuses on testosterone replacement therapy (TRT), although the effects of this therapy have not been studied rigorously, and future studies need to evaluate the effects of TRT on metabolic risk and neurocognitive outcomes. This review presents a comprehensive interdisciplinary examination of recent developments in genetic, endocrine, and neurocognitive science, including the study of animal models. It provides a number of recommendations for improving the effectiveness of research and clinical practice, including neonatal KS screening programs, and a multidisciplinary approach to KS treatment from childhood until senescence.

Sex Differences in White Matter Microstructure in the Human Brain Predominantly Reflect Differences in Sex Hormone Exposure

Sex differences have been described regarding several aspects of human brain morphology; however, the exact biological mechanisms underlying these differences remain unclear in humans. Women with the complete androgen insensitivity syndrome (CAIS), who lack androgen action in the presence of a 46,XY karyotype, offer the unique opportunity to study isolated effects of sex hormones and sex chromosomes on human neural sexual differentiation. In the present study, we used diffusion tensor imaging to investigate white matter (WM) microstructure in 46,XY women with CAIS (n = 20), 46,XY comparison men (n = 30), and 46,XX comparison women (n = 30). Widespread sex differences in fractional anisotropy (FA), with higher FA in comparison men than in comparison women, were observed. Women with CAIS showed female-typical FA throughout extended WM regions, predominantly due to female-typical radial diffusivity. These findings indicate a predominant role of sex hormones in the sexual differentiation of WM microstructure, although sex chromosome genes and/or masculinizing androgen effects not mediated by the androgen receptor might also play a role.

Sex chromosome aneuploidies

Sex chromosome aneuploidies comprise a relatively common group of chromosome disorders characterized by the loss or gain of one or more sex chromosomes. We discuss five of the better-known sex aneuploidies: Turner syndrome (XO), Klinefelter syndrome (XXY), trisomy X (XXX), XYY, and XXYY. Despite their prevalence in the general population, these disorders are underdiagnosed and the specific genetic mechanisms underlying their phenotypes are poorly understood. Although there is considerable variation between them in terms of associated functional impairment, each disorder has a characteristic physical, cognitive, and neurologic profile. The most common cause of sex chromosome aneuploidies is nondisjunction, which can occur during meiosis or during the early stages of postzygotic development. The loss or gain of genetic material can affect all daughter cells or it may be partial, leading to tissue mosaicism. In both typical and atypical sex chromosome karyotypes, there is random inactivation of all but one X chromosome. The mechanisms by which a phenotype results from sex chromosome aneuploidies are twofold: dosage imbalance arising from a small number of genes that escape inactivation, and their endocrinologic consequences.

The Sexual Differentiation of the Human Brain: Role of Sex Hormones Versus Sex Chromosomes

Men and women differ, not only in their anatomy but also in their behavior. Research using animal models has convincingly shown that sex differences in the brain and behavior are induced by sex hormones during a specific, hormone-sensitive period during early development. Thus, male-typical psychosexual characteristics seem to develop under the influence of testosterone, mostly acting during early development. By contrast, female-typical psychosexual characteristics may actually be organized under the influence of estradiol during a specific prepubertal period. The sexual differentiation of the human brain also seems to proceed predominantly under the influence of sex hormones. Recent studies using magnetic resonance imaging have shown that several sexually differentiated aspects of brain structure and function are female-typical in women with complete androgen insensitivity syndrome (CAIS), who have a 46 XY karyotype but a female phenotype due to complete androgen resistance, suggesting that these sex differences most likely reflect androgen action, although feminizing effects of estrogens or female-typical socialization cannot be ruled out. By contrast, some male-typical neural characteristics were also observed in women with CAIS suggesting direct effects of sex chromosome genes in the sexual differentiation of the human brain. In conclusion, the sexual differentiation of the human brain is most likely a multifactorial process including both sex hormone and sex chromosome effects, acting in parallel or in combination.

Cognitive, behavioral, and neural consequences of sex chromosome aneuploidy

The X chromosome has played a critical role in the development of sexually selected characteristics for over 300 million years, and during that time it has accumulated a disproportionate number of genes concerned with mental functions. There are relatively specific effects of X-linked genes on social cognition, language, emotional regulation, visuospatial, and numerical skills. Many human X-linked genes outside the X-Y pairing pseudoautosomal regions escape X-inactivation. Dosage differences in the expression of such genes (which constitute at least 15% of the total) are likely to play an important role in male-female neural differentiation, and in cognitive deficits and behavioral characteristics, particularly in the realm of social communication, that are associated with sex chromosome aneuploidies. © 2016 Wiley Periodicals, Inc.

White matter microstructure in a genetically defined group at increased risk of autism symptoms, and a comparison with idiopathic autism: an exploratory study

Klinefelter syndrome (47,XXY) is associated with physical, behavioral, and cognitive consequences. Deviations in brain structure and function have been reported, but structural characteristics of white matter have barely been assessed. This exploratory diffusion tensor imaging study assessed white matter microstructure in boys with 47,XXY compared with non-clinical, male controls. Additionally, both similarities and differences between 47,XXY and autism spectrum disorders (ASD) have been reported in cognition, behavior and neural architecture. To further investigate these brain-behavior pathways, white matter microstructure in boys with 47,XXY was compared to that of boys with ASD. Fractional anisotropy (FA), radial diffusivity (Dr), axial diffusivity (Da), and mean diffusivity (MD) were assessed in 47,XXY (n = 9), ASD (n = 18), and controls (n = 14), using tract-based spatial statistics. Compared with controls, boys with 47,XXY have reduced FA, coupled with reduced Da, in the corpus callosum. Boys with 47,XXY also have reduced Dr. in the left anterior corona radiata and sagittal striatum compared with controls. Compared with boys with ASD, boys with 47,XXY show reduced Da in the right inferior fronto-occipital fasciculus. Although this study is preliminary considering the small sample size, reduced white matter integrity in the corpus callosum may be a contributing factor in the cognitive and behavioral problems associated with 47,XXY. In addition, the differences in white matter microstructure between 47,XXY and ASD may be important for our understanding of the mechanisms that are fundamental to behavioral outcome in social dysfunction, and may be targeted through intervention.

Klinefelter syndrome comorbidities linked to increased X chromosome gene dosage and altered protein interactome activity

Klinefelter syndrome (KS) (47,XXY) is the most common male sex chromosome aneuploidy. Diagnosis and clinical supervision remain a challenge due to varying phenotypic presentation and insufficient characterization of the syndrome. Here we combine health data-driven epidemiology and molecular level systems biology to improve the understanding of KS and the molecular interplay influencing its comorbidities. In total, 78 overrepresented KS comorbidities were identified using in- and out-patient registry data from the entire Danish population covering 6.8 million individuals. The comorbidities extracted included both clinically well-known (e.g. infertility and osteoporosis) and still less established KS comorbidities (e.g. pituitary gland hypofunction and dental caries). Several systems biology approaches were applied to identify key molecular players underlying KS comorbidities: Identification of co-expressed modules as well as central hubs and gene dosage perturbed protein complexes in a KS comorbidity network build from known disease proteins and their protein–protein interactions. The systems biology approaches together pointed to novel aspects of KS disease phenotypes including perturbed Jak-STAT pathway, dysregulated genes important for disturbed immune system (IL4), energy balance (POMC and LEP) and erythropoietin signalling in KS. We present an extended epidemiological study that links KS comorbidities to the molecular level and identify potential causal players in the disease biology underlying the identified comorbidities.

Genetic Consideration of Schizotypal Traits: A Review

Schizotypal traits are of interest and importance in their own right and also have theoretical and clinical associations with schizophrenia. These traits comprise attenuated psychotic symptoms, social withdrawal, reduced cognitive capacity, and affective dysregulation. The link between schizotypal traits and psychotic disorders has long since been debated. The status of knowledge at this point is such schizotypal traits are a risk for psychotic disorders, but in and of themselves only confer liability, with other risk factors needing to be present before a transition to psychosis occurs. Investigation of schizotypal traits also has the possibility to inform clinical and research pursuits concerning those who do not make a transition to psychotic disorders. A growing body of literature has investigated the genetic underpinnings of schizotypal traits. Here, we review association, family studies and describe genetic disorders where the expression of schizotypal traits has been investigated. We conducted a thorough review of the existing literature, with multiple search engines, references, and linked articles being searched for relevance to the current review. All articles and book chapters in English were sourced and reviewed for inclusion. Family studies demonstrate that schizotypal traits are elevated with increasing genetic proximity to schizophrenia and some chromosomal regions have been associated with schizotypy. Genes associated with schizophrenia have provided the initial start point for the investigation of candidate genes for schizotypal traits; neurobiological pathways of significance have guided selection of genes of interest. Given the chromosomal regions associated with schizophrenia, some genetic disorders have also considered the expression of schizotypal traits. Genetic disorders considered all comprise a profile of cognitive deficits and over representation of psychotic disorders compared to the general population. We conclude that genetic variations associated with schizotypal traits require further investigation, perhaps with targeted phenotypes narrowed to assist in refining the clinical end point of significance.

Do the presence of Barr bodies in male jail inmates indicates criminality: A pilot study

Background:

Cytogenetic studies from past decades have shown that interphase cells of female cats contain a densely stained chromatin mass in their nuclei called as Barr bodies (BBs) named after the scientist Murray Barr. BBs are unique chromatin structures formed due to the condensation of the X-chromosome. Many psychopathic disorders originate from defective genes including the multiple X syndromes. Males with extra X-chromosome generally present with severe personality disorder. The present study was conducted to determine the presence of extra X-chromosome in male jail inmates through the detection of BB in peripheral blood and buccal smear.

Materials and Methods:

Study included 100 male subjects (fifty jail inmates and fifty controls), after obtaining the consent, peripheral blood smears (PBS) and buccal smears (BS) were prepared and stained using Leishman's and cresyl violet stain respectively. One hundred neutrophils in PBS and epithelial cells in BS were screened for detection of the BB; accumulated data were tabulated and statistically analyzed using t-test and Chi-square test.

Results:

60% of cases in PBS and 36% in BS showed positivity for the presence of BB in jail inmates as compared to 14% of cases in PBS and none in BS were positive for BB in controls.

Conclusion:

Presence of BB in male suggests increased likelihood of criminal tendencies. Further studies are to be carried out to compare the results with karyotyping.

Anatomical and clinical aspects of Klinefelter's syndrome

Klinefelter's syndrome, the most common sex disorder associated with chromosomal aberrations, is characterized by a plethora of clinical features. Parameters for diagnosis of the syndrome are constantly expanding as new anatomical and hormonal abnormalities are noted, yet Klinefelter's remains underdiagnosed and underreported. This review outlines the key anatomical characteristics associated with the syndrome, which are currently used for clinical diagnosis, or may provide means for improving diagnosis in the future. Clin. Anat. 29:606-619, 2016. © 2016 Wiley Periodicals, Inc.

Klinefelter syndrome has increased brain responses to auditory stimuli and motor output, but not to visual stimuli or Stroop adaptation

Klinefelter syndrome (47, XXY) (KS) is a genetic syndrome characterized by the presence of an extra X chromosome and low level of testosterone, resulting in a number of neurocognitive abnormalities, yet little is known about brain function. This study investigated the fMRI-BOLD response from KS relative to a group of Controls to basic motor, perceptual, executive and adaptation tasks. Participants (N: KS = 49; Controls = 49) responded to whether the words "GREEN" or "RED" were displayed in green or red (incongruent versus congruent colors). One of the colors was presented three times as often as the other, making it possible to study both congruency and adaptation effects independently. Auditory stimuli saying "GREEN" or "RED" had the same distribution, making it possible to study effects of perceptual modality as well as Frequency effects across modalities. We found that KS had an increased response to motor output in primary motor cortex and an increased response to auditory stimuli in auditory cortices, but no difference in primary visual cortices. KS displayed a diminished response to written visual stimuli in secondary visual regions near the Visual Word Form Area, consistent with the widespread dyslexia in the group. No neural differences were found in inhibitory control (Stroop) or in adaptation to differences in stimulus frequencies. Across groups we found a strong positive correlation between age and BOLD response in the brain's motor network with no difference between groups. No effects of testosterone level or brain volume were found. In sum, the present findings suggest that auditory and motor systems in KS are selectively affected, perhaps as a compensatory strategy, and that this is not a systemic effect as it is not seen in the visual system.

Neural systems for social cognition: gray matter volume abnormalities in boys at high genetic risk of autism symptoms, and a comparison with idiopathic autism spectrum disorder

Klinefelter syndrome (47, XXY) is associated with several physical, cognitive, and behavioral consequences. In terms of social development, there is an increased risk of autism symptomatology. However, it remains unclear how social deficits are related to abnormal brain development and to what degree underlying mechanisms of social dysfunction in 47, XXY are similar to, or different from, those in idiopathic autism (ASD). This study was aimed at investigating the neural architecture of brain structures related to social information processing in boys with 47, XXY, also in comparison with boys with idiopathic ASD. MRI scans of 16 boys with 47, XXY, 16 with ASD, and 16 nonclinical, male controls were analyzed using voxel-based morphometry (VBM). A region of interest mask containing the superior temporal cortex, amygdala, orbitofrontal cortex (OFC), insular cortex, and medial frontal cortex was used. The Social Responsiveness Scale (SRS) was used to assess degree of autism spectrum symptoms. The 47, XXY group could not be distinguished from the ASD group on mean SRS scores, and their scores were significantly higher than in controls. VBM showed that boys with 47, XXY have significant gray matter volume reductions in the left and right insula, and the left OFC, compared with controls and boys with ASD. Additionally, boys with 47, XXY had significantly less gray matter in the right superior temporal gyrus than controls. These results imply social challenges associated with 47, XXY may be rooted in neural anatomy, and autism symptoms in boys with 47, XXY and boys with ASD might have, at least partially, different underlying etiologies.

Sex/gender differences in the brain and cognition in schizophrenia

The early conceptualizations of schizophrenia have noted some sex/gender differences in epidemiology and clinical expression of the disorder. Over the past few decades, the interest in differences between male and female patients has expanded to encompass brain morphology and neurocognitive function. Despite some variability and methodological shortcomings, a few patterns emerge from the available literature. Most studies of gross neuroanatomy show more enlarged ventricles and smaller frontal lobes in men than in women with schizophrenia; finding reflecting normal sexual dimorphism. In comparison, studies of brain asymmetry and specific corticolimbic structures, suggest a disturbance in normal sexual dimorphism. The neurocognitive findings are somewhat consistent with this picture. Studies of cognitive functions mediated by the lateral frontal network tend to show sex differences in patients which are in the same direction as those observed in the general population, whereas studies of processes mediated by the corticolimbic system more frequently reveal reversal of normal sexual dimorphisms. These trends are faint and future research would need to delineate neurocognitive differences between men and women with various subtypes of schizophrenia (e.g., early versus late onset), while taking into consideration hormonal status and gender of tested participants.

Review of endocrine disorders associated with environmental toxicants and possible involved mechanisms

Endocrine disrupting chemicals (EDC) are released into environment from different sources. They are mainly used in packaging industries, pesticides and food constituents. Clinical evidence, experimental models, and epidemiological studies suggest that EDC have major risks for human by targeting different organs and systems in the body. Multiple mechanisms are involved in targeting the normal system, through estrogen receptors, nuclear receptors and steroidal receptors activation. In this review, different methods by which xenobiotics stimulate signaling pathways and genetic mutation or DNA methylation have been discussed. These methods help to understand the results of xenobiotic action on the endocrine system. Endocrine disturbances in the human body result in breast cancer, ovarian problems, thyroid eruptions, testicular carcinoma, Alzheimer disease, schizophrenia, nerve damage and obesity. EDC characterize a wide class of compounds such as organochlorinated pesticides, industrial wastes, plastics and plasticizers, fuels and numerous other elements that exist in the environment or are in high use during daily life. The interactions and mechanism of toxicity in relation to human general health problems, especially endocrine disturbances with particular reference to reproductive problems, diabetes, and breast, testicular and ovarian cancers should be deeply investigated. There should also be a focus on public awareness of these EDC risks and their use in routine life. Therefore, the aim of this review is to summarize all evidence regarding different physiological disruptions in the body and possible involved mechanisms, to prove the association between endocrine disruptions and human diseases.

A Role for the X Chromosome in Sex Differences in Variability in General Intelligence?

There is substantial evidence that males are more variable than females in general intelligence. In recent years, researchers have presented this as a reason that, although there is little, if any, mean sex difference in general intelligence, males tend to be overrepresented at both ends of its overall distribution. Part of the explanation could be the presence of genes on the X chromosome related both to syndromal disorders involving mental retardation and to population variation in general intelligence occurring normally. Genes on the X chromosome appear overrepresented among genes with known involvement in mental retardation, which is consistent with a model we developed of the population distribution of general intelligence as a mixture of two normal distributions. Using this model, we explored the expected ratios of males to females at various points in the distribution and estimated the proportion of variance in general intelligence potentially due to genes on the X chromosome. These estimates provide clues to the extent to which biologically based sex differences could be manifested in the environment as sex differences in displayed intellectual abilities. We discuss these observations in the context of sex differences in specific cognitive abilities and evolutionary theories of sexual selection.

A Case Report of Klinefelter Syndrome with Schizophrenia-Like Psychosis and Seizure Disorder

Klinefelter syndrome is a disorder of variation of sex chromosome, the most common karyotype being 47XXY. Multiple case reports and articles have been published linking the increased prevalence of psychiatric disorders like Schizophrenia, Schizophreniform psychosis, Attention deficit hyperkinetic disorder, Learning disorder, etc. and seizure disorder in Klinefelter syndrome than in general population, attributing to the extra X chromosome. Here is a case of a 45-year-old gentleman with Klinefelter syndrome with schizophrenia-like psychosis and seizure disorder. He was diagnosed as Klinefelter syndrome 15 years back by genetic testing (47XXY) when he was investigated for infertility. His luteinizing hormone (LH) (32.04 mIU/ml) and follicle-stimulating hormone (FSH) (50.70 mIU/ml) levels were high and his testosterone level was low (1.76 ng/ml). He had four episodes of seizures in 2004 for which he was started on phenytoin and sodium valproate, and was seizure-free for past 10 years. He was brought to our hospital in July 2014 with complaints of talking and laughing to self, suspicion, hearing voices and aggressive behaviour, which were persistent mildly for past 15 years and aggravated for past 6 months. He was not going for work for past 15 years, does not mingle with relatives or friends.

Over-expression of XIST, the Master Gene for X Chromosome Inactivation, in Females With Major Affective Disorders

Background

Psychiatric disorders are common mental disorders without a pathological biomarker. Classic genetic studies found that an extra X chromosome frequently causes psychiatric symptoms in patients with either Klinefelter syndrome (XXY) or Triple X syndrome (XXX). Over-dosage of some X-linked escapee genes was suggested to cause psychiatric disorders. However, relevance of these rare genetic diseases to the pathogenesis of psychiatric disorders in the general population of psychiatric patients is unknown.

Methods

XIST and several X-linked genes were studied in 36 lymphoblastoid cell lines from healthy females and 60 lymphoblastoid cell lines from female patients with either bipolar disorder or recurrent major depression. XIST and KDM5C expression was also quantified in 48 RNA samples from postmortem human brains of healthy female controls and female psychiatric patients.

Findings

We found that the XIST gene, a master in control of X chromosome inactivation (XCI), is significantly over-expressed (p = 1 × 10^− 7, corrected after multiple comparisons) in the lymphoblastoid cells of female patients with either bipolar disorder or major depression. The X-linked escapee gene KDM5C also displays significant up-regulation (p = 5.3 × 10^− 7, corrected after multiple comparisons) in the patients' cells. Expression of XIST and KDM5C is highly correlated (Pearson's coefficient, r = 0.78, p = 1.3 × 10^− 13). Studies on human postmortem brains supported over-expression of the XIST gene in female psychiatric patients.

Interpretations

We propose that over-expression of XIST may cause or result from subtle alteration of XCI, which up-regulates the expression of some X-linked escapee genes including KDM5C. Over-expression of X-linked genes could be a common mechanism for the development of psychiatric disorders between patients with those rare genetic diseases and the general population of female psychiatric patients with XIST over-expression. Our studies suggest that XIST and KDM5C expression could be used as a biological marker for diagnosis of psychiatric disorders in a significantly large subset of female patients.

Research in context

Due to lack of biological markers, diagnosis and treatment of psychiatric disorders are subjective. There is utmost urgency to identify biomarkers for clinics, research, and drug development. We found that XIST and KDM5C gene expression may be used as a biological marker for diagnosis of major affective disorders in a significantly large subset of female patients from the general population. Our studies show that over-expression of XIST and some X-linked escapee genes may be a common mechanism for development of psychiatric disorders between the patients with rare genetic diseases (XXY or XXX) and the general population of female psychiatric patients.

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XIST and KDM5C genes are over-expressed in a large subset of female patients with major affective disorders.

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Over-expression of XIST and KDM5C genes could be used as a biomarker for diagnosis of individual patients.

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Over-expression of XIST and X-linked escapee genes including KDM5C may cause major affective disorders.

Neuropsychology and socioeconomic aspects of Klinefelter syndrome: new developments

PURPOSE OF REVIEW

To summarize recent important studies on neuropsychology and epidemiology of Klinefelter syndrome. PubMed was searched for 'Klinefelter', 'Klinefelter's' and 'XXY' in titles and abstracts. Relevant studies were obtained and reviewed, as well as other articles selected by the authors.

RECENT FINDINGS

Klinefelter syndrome is the most common sex-chromosome disorder in humans, affecting one in 660 men. The key findings in Klinefelter syndrome are small testes, hypergonadotropic hypogonadism and cognitive impairment. Klinefelter syndrome scores significantly below education matched controls on a range of cognitive tests with verbal skills displaying the largest effects. Boys with Klinefelter syndrome are often in the need of speech therapy and many suffer from learning disability and may benefit from special education. New studies are elucidating aspects of cognitive functioning and suggesting that neuropsychological treatment may be of value. The socioeconomic status and educational level of Klinefelter syndrome is severely affected with many struggling to achieve any or only shorter education, resulting in low-income levels and early retirement. In addition, few become fathers and fewer live with a partner compared with controls. Medical treatment is mainly testosterone replacement therapy in order to alleviate acute and long-term consequences of hypogonadism, as well as, treating or preventing the frequent comorbidity.

SUMMARY

The neurocognitive phenotype of Klinefelter syndrome is being unraveled and the need for psychological and cognitive treatment in many cases is evident. The neurocognitive deficits no doubt influence the socioeconomic status of many Klinefelter syndrome patients, which is clearly inferior to age-matched controls.

Cognitive performances associate with measures of white matter integrity in bipolar disorder

BACKGROUND

Neuropsychological deficits constitute enduring trait-like features in bipolar disorder (BD), and persist in euthymia. White matter (WM) abnormalities are one of the most consistently reported findings in neuroimaging studies of BD. We hypothesized that neuropsychological performances could correlate with WM integrity in a sample of bipolar patients in core WM tracts.

METHODS

Seventy-eight patients affected by BD were evaluated for verbal memory, working memory, psychomotor coordination, executive functions, attention and information processing, and verbal fluency through the Brief Assessment of Cognition in Schizophrenia. White matter integrity was evaluated using DTI and tract-based spatial statistics with threshold free cluster enhancement (p>0.949).

RESULTS

We observed that cognitive performances in attention and information processing, working memory, executive functions and psychomotor coordination were associated with DTI measures of WM integrity in several association fibres: inferior and superior longitudinal fasciculus, inferior fronto-occipital fasciculus, cingulum bundle, corpus callosum, and corona radiata.

LIMITATION

The drug treatments administered during the course of the illness could have influenced DTI measures and neurocognitive function. Other limitations include issues such as generalizability due to the lack of a control group, possible undetected past comorbidities, population stratification, and the presence of a 28% of patients which previously experienced delusions.

CONCLUSIONS

This is the first study to use a validated cognitive battery to investigate the principal cognitive domains in BD. Our data confirm the importance of WM integrity as a neurobiological underpinning of cognitive deficits.

Effects of sex chromosome dosage on corpus callosum morphology in supernumerary sex chromosome aneuploidies

Background

Supernumerary sex chromosome aneuploidies (sSCA) are characterized by the presence of one or more additional sex chromosomes in an individual’s karyotype; they affect around 1 in 400 individuals. Although there is high variability, each sSCA subtype has a characteristic set of cognitive and physical phenotypes. Here, we investigated the differences in the morphometry of the human corpus callosum (CC) between sex-matched controls 46,XY (N =99), 46,XX (N =93), and six unique sSCA karyotypes: 47,XYY (N =29), 47,XXY (N =58), 48,XXYY (N =20), 47,XXX (N =30), 48,XXXY (N =5), and 49,XXXXY (N =6).

Methods

We investigated CC morphometry using local and global area, local curvature of the CC boundary, and between-landmark distance analysis (BLDA). We hypothesized that CC morphometry would vary differentially along a proposed spectrum of Y:X chromosome ratio with supernumerary Y karyotypes having the largest CC areas and supernumerary X karyotypes having significantly smaller CC areas. To investigate this, we defined an sSCA spectrum based on a descending Y:X karyotype ratio: 47,XYY, 46,XY, 48,XXYY, 47,XXY, 48,XXXY, 49,XXXXY, 46,XX, 47,XXX. We similarly explored the effects of both X and Y chromosome numbers within sex. Results of shape-based metrics were analyzed using permutation tests consisting of 5,000 iterations.

Results

Several subregional areas, local curvature, and BLDs differed between groups.

Moderate associations were found between area and curvature in relation to the spectrum and X and Y chromosome counts. BLD was strongly associated with X chromosome count in both male and female groups.

Conclusions

Our results suggest that X- and Y-linked genes have differential effects on CC morphometry. To our knowledge, this is the first study to compare CC morphometry across these extremely rare groups.

Mouse model systems to study sex chromosome genes and behavior: relevance to humans

Sex chromosome genes directly influence sex differences in behavior. The discovery of the Sry gene on the Y chromosome (Gubbay et al., 1990; Koopman et al., 1990) substantiated the sex chromosome mechanistic link to sex differences. Moreover, the pronounced connection between X chromosome gene mutations and mental illness produces a strong sex bias in these diseases. Yet, the dominant explanation for sex differences continues to be the gonadal hormones. Here we review progress made on behavioral differences in mouse models that uncouple sex chromosome complement from gonadal sex. We conclude that many social and cognitive behaviors are modified by sex chromosome complement, and discuss the implications for human research. Future directions need to include identification of the genes involved and interactions with these genes and gonadal hormones.

Influence of the X-chromosome on neuroanatomy: evidence from Turner and Klinefelter syndromes

Studies of sex effects on neurodevelopment have traditionally focused on animal models investigating hormonal influences on brain anatomy. However, more recent evidence suggests that sex chromosomes may also have direct upstream effects that act independently of hormones. Sex chromosome aneuploidies provide ideal models to examine this framework in humans, including Turner syndrome (TS), where females are missing one X-chromosome (45X), and Klinefelter syndrome (KS), where males have an additional X-chromosome (47XXY). As these disorders essentially represent copy number variants of the sex chromosomes, investigation of brain structure across these disorders allows us to determine whether sex chromosome gene dosage effects exist. We used voxel-based morphometry to investigate this hypothesis in a large sample of children in early puberty, to compare regional gray matter volumes among individuals with one (45X), two (typically developing 46XX females and 46XY males), and three (47XXY) sex chromosomes. Between-group contrasts of TS and KS groups relative to respective sex-matched controls demonstrated highly convergent patterns of volumetric differences with the presence of an additional sex chromosome being associated with relatively decreased parieto-occipital gray matter volume and relatively increased temporo-insular gray matter volumes. Furthermore, z-score map comparisons between TS and KS cohorts also suggested that this effect occurs in a linear dose-dependent fashion. We infer that sex chromosome gene expression directly influences brain structure in children during early stages of puberty, extending our understanding of genotype-phenotype mechanisms underlying sex differences in the brain.

The role of hypogonadism in Klinefelter syndrome

Klinefelter syndrome (KS) (47, XXY) is the most abundant sex-chromosome disorder, and is a common cause of infertility and hypogonadism in men. Most men with KS go through life without knowing the diagnosis, as only 25% are diagnosed and only a few of these before puberty. Apart from hypogonadism and azoospermia, most men with KS suffer from some degree of learning disability and may have various kinds of psychiatric problems. The effects of long-term hypogonadism may be diffi cult to discern from the gene dose effect of the extra X-chromosome. Whatever the cause, alterations in body composition, with more fat and less muscle mass and diminished bone mineral mass, as well as increased risk of metabolic consequences, such as type 2 diabetes and the metabolic syndrome are all common in KS. These findings should be a concern as they are not simply laboratory findings; epidemiological studies in KS populations show an increased risk of both hospitalization and death from various diseases. Testosterone treatment should be offered to KS patients from early puberty, to secure a proper masculine development, nonetheless the evidence is weak or nonexisting, since no randomized controlled trials have ever been published. Here, we will review the current knowledge of hypogonadism in KS and the rationale for testosterone treatment and try to give our best recommendations for surveillance of this rather common, but often ignored, syndrome.

Mosaic Turner syndrome associated with schizophrenia

Turner syndrome is a sex-chromosome disorder; occurring in 1 in 2,500 female births. There are sporadic few case reports of concomitant Turner syndrome with schizophrenia worldwide. Most Turner females had a 45,X monosomy, whereas the majority of comorbidity between Turner syndrome and schizophrenia had a mosaic karyotype (45,X/46,XX). We present a case of a 21-year-old woman with Turner syndrome, mosaic karyotype (45,X/46,XX), showing mental retardation, hypothyroidism, and schizophrenia. HOPA gene within Xq13 is related to mental retardation, hypothyroidism, and schizophrenia. Our case may be a potential clue which supports the hypothesis for involvement of genes on X chromosome in development of schizophrenia. Further studies including comorbid cases reports are need in order to discern the cause of schizophrenia in patients having Turner syndrome.