Sex differences in amygdala shape: Insights from Turner syndrome

White matter microstructure and functional connectivity in the brains of infants with Turner syndrome

Turner syndrome, caused by complete or partial loss of an X-chromosome, is often accompanied by specific cognitive challenges. Magnetic resonance imaging studies of adults and children with Turner syndrome suggest these deficits reflect differences in anatomical and functional connectivity. However, no imaging studies have explored connectivity in infants with Turner syndrome. Consequently, it is unclear when in development connectivity differences emerge. To address this gap, we compared functional connectivity and white matter microstructure of 1-year-old infants with Turner syndrome to typically developing 1-year-old boys and girls. We examined functional connectivity between the right precentral gyrus and five regions that show reduced volume in 1-year old infants with Turner syndrome compared to controls and found no differences. However, exploratory analyses suggested infants with Turner syndrome have altered connectivity between right supramarginal gyrus and left insula and right putamen. To assess anatomical connectivity, we examined diffusivity indices along the superior longitudinal fasciculus and found no differences. However, an exploratory analysis of 46 additional white matter tracts revealed significant group differences in nine tracts. Results suggest that the first year of life is a window in which interventions might prevent connectivity differences observed at later ages, and by extension, some of the cognitive challenges associated with Turner syndrome.

Syndrome-Specific Neuroanatomical Phenotypes in Girls With Turner and Noonan Syndromes

BACKGROUND

Turner syndrome (TS) and Noonan syndrome (NS) are distinct genetic conditions with highly similar physical and neurodevelopmental phenotypes. TS is caused by X chromosome absence, whereas NS results from genetic mutations activating the Ras-mitogen-activated protein kinase signaling pathway. Previous neuroimaging studies in individuals with TS and NS have shown neuroanatomical variations relative to typically developing individuals, a standard comparison group when initially examining a clinical group of interest. However, none of these studies included a second clinical comparison group, limiting their ability to identify syndrome-specific neuroanatomical phenotypes.

METHODS

In this study, we compared the behavioral and brain phenotypes of 37 girls with TS, 26 girls with NS, and 37 typically developing girls, all ages 5 to 12 years, using univariate and multivariate data-driven analyses.

RESULTS

We found divergent neuroanatomical phenotypes between groups, despite high behavioral similarities. Relative to the typically developing group, TS was associated with smaller whole-brain cortical surface area (p ≤ .0001), whereas NS was associated with smaller whole-brain cortical thickness (p = .013). TS was associated with larger subcortical volumes (left amygdala, p = .002; right hippocampus, p = .002), whereas NS was associated with smaller subcortical volumes (bilateral caudate, p ≤ .003; putamen, p < .001; pallidum, p < .001; right hippocampus, p = .015). Multivariate analyses also showed diverging brain phenotypes in terms of surface area and cortical thickness, with surface area outperforming cortical thickness at group separation.

CONCLUSIONS

TS and NS have syndrome-specific brain phenotypes, despite their behavioral similarities. Our observations suggest that neuroanatomical phenotypes better reflect the different genetic etiologies of TS and NS and may be superior biomarkers relative to behavioral phenotypes.

Adolescent brain development in girls with Turner syndrome

Turner syndrome (TS) is a common sex chromosome aneuploidy in females associated with various physical, cognitive, and socio-emotional phenotypes. However, few studies have examined TS-associated alterations in the development of cortical gray matter volume and the two components that comprise this measure-surface area and thickness. Moreover, the longitudinal direct (i.e., genetic) and indirect (i.e., hormonal) effects of X-monosomy on the brain are unclear. Brain structure was assessed in 61 girls with TS (11.3 ± 2.8 years) and 55 typically developing girls (10.8 ± 2.3 years) for up to 4 timepoints. Surface-based analyses of cortical gray matter volume, thickness, and surface area were conducted to examine the direct effects of X-monosomy present before pubertal onset and indirect hormonal effects of estrogen deficiency/X-monosomy emerging after pubertal onset. Longitudinal analyses revealed that, whereas typically developing girls exhibited normative declines in gray matter structure during adolescence, this pattern was reduced or inverted in TS. Further, girls with TS demonstrated smaller total surface area and larger average cortical thickness overall. Regionally, the TS group exhibited decreased volume and surface area in the pericalcarine, postcentral, and parietal regions relative to typically developing girls, as well as larger volume in the caudate, amygdala, and temporal lobe regions and increased thickness in parietal and temporal regions. Surface area alterations were predominant by age 8, while maturational differences in thickness emerged by age 10 or later. Taken together, these results suggest the involvement of both direct and indirect effects of X-chromosome haploinsufficiency on brain development in TS.

Quality of Life and Psychosocial Well-Being among Intersex-Identifying Individuals in Puerto Rico: An Exploratory Study

PURPOSE

Intersex is an umbrella term used to describe the diversity or differences in the characteristics of physical sexual development. Approximately 1.7% of the population are born intersex, and 1 in every 2000 babies at birth presents genital variation. Unfortunately, there is a lack of research on the health of intersex-identifying persons in Latin America. This study aimed to document experiences of discrimination and violence among self-identifying intersex individuals in Puerto Rico and to determine if there is a significant difference in the quality of life, psychological well-being, and social well-being between intersex-identifying and endosex individuals.

METHODS

This was a quantitative method pilot study with a cross-sectional approach and exploratory comparative group design. An online survey was used, where a total of 12 self-identifying intersex adult participants were recruited, and 126 endosex adult participants served as a comparative group.

RESULTS

The findings show that 83% of the participants reported experiences of discrimination and different types of violence due to their intersexuality. There was a significant difference between the intersex-identifying and endosex groups in psychological well-being, including in three of its dimensions (positives relations, autonomy, and environmental mastery). However, there were no significant differences between the groups in quality of life or social well-being.

CONCLUSION

The findings of this study provide a preliminary understanding of the health disparities of intersex-identifying individuals in Puerto Rico and suggest the need for more profound research, especially the inclusion of other Caribbean and Hispanic countries. The findings also preliminarily imply the need for local and global interventions to reduce physical and mental health disparities and to improve health, quality of life, and well-being among intersex-identifying individuals.

Effect of sex chromosome number variation on attention-deficit/hyperactivity disorder symptoms, executive function, and processing speed

AIM

To study sex differences in attention-deficit/hyperactivity disorder (ADHD) symptoms, we explored whether X chromosome absence or excess is independently associated with deficits in attention and hyperactivity, executive function, and processing speed.

METHOD

We assessed 116 children (ages 3y 10mo-11y 11mo, mean 8y 5mo, SD 1y 11mo) with a variable number of sex chromosomes: 36 females with Turner syndrome (45, X0), 20 males with Klinefelter syndrome (47, XXY), 37 typically developing females (XX), and 23 typically developing males (XY).

RESULTS

X chromosome absence was associated with increased attention problems, hyperactivity, and deficits in inhibitory control, compared with female children with XX (all p<0.003). Conversely, X chromosome excess was associated with weakness in working memory (p=0.018) and approached significance for attention problems (p=0.071) but not with hyperactivity, or weakness in inhibitory control relative to male children with XY. Using non-parametric effect size to quantify the clinical effect revealed that X chromosome absence affected attention, hyperactivity, executive function, and processing speed (all r>0.4), while X excess affected in-laboratory as well as parent-reported working memory (all r>0.4).

INTERPRETATION

Our observations provide compelling evidence that the absence or excess of an X chromosome distinctly affects cognition and behaviors associated with ADHD.

Deep learning identifies morphological determinants of sex differences in the pre-adolescent brain

The application of data-driven deep learning to identify sex differences in developing brain structures of pre-adolescents has heretofore not been accomplished. Here, the approach identifies sex differences by analyzing the minimally processed MRIs of the first 8144 participants (age 9 and 10 years) recruited by the Adolescent Brain Cognitive Development (ABCD) study. The identified pattern accounted for confounding factors (i.e., head size, age, puberty development, socioeconomic status) and comprised cerebellar (corpus medullare, lobules III, IV/V, and VI) and subcortical (pallidum, amygdala, hippocampus, parahippocampus, insula, putamen) structures. While these have been individually linked to expressing sex differences, a novel discovery was that their grouping accurately predicted the sex in individual pre-adolescents. Another novelty was relating differences specific to the cerebellum to pubertal development. Finally, we found that reducing the pattern to a single score not only accurately predicted sex but also correlated with cognitive behavior linked to working memory. The predictive power of this score and the constellation of identified brain structures provide evidence for sex differences in pre-adolescent neurodevelopment and may augment understanding of sex-specific vulnerability or resilience to psychiatric disorders and presage sex-linked learning disabilities.

Emotional state, cognitive functioning and quality of life of adult women with Turner syndrome in Lithuania

AIM

The aim was to analyze emotional state, cognitive functioning and quality of life (QoL) of adult women with Turner syndrome (TS) in Lithuania.

PATIENTS AND METHODS

Of all invited adult TS patients from Lithuanian TS database (n = 150), 68 (age 18-60, average 30.2 ± 9.0 years) agreed and were recruited for the study, as well as 68 age-matched healthy control women. Emotional state was evaluated by Profile of Mood States (POMS) questionnaire, cognitive functioning by Trail Making Test and Digit Span Test (DST) of Wechsler Adult Intelligence Scale, and QoL by WHO Brief Quality of Life Questionnaire (WHO QoL).

RESULTS

Patients with TS were of a significantly shorter stature (p < .001) than age-matched control women and than the 3rd percentile of the National Standards of Lithuania. After the adjustment for height, weight and body mass index (BMI), no significant differences in emotional state were detected, though without the adjustment, depression-dejection (p = .004) score was significantly higher in TS women than in age-matched controls. Significantly worse cognitive functioning (attention capacity, visual scanning abilities, executive function and psychomotor speed, p < .001), as well as worse psychological (p = .002) and social (p = .006) aspects of QoL were found after the adjustment for height, weight and BMI in adult women with TS than in age-matched controls.

CONCLUSION

In conclusion, after the adjustment for height, weight and BMI, adult women with Turner syndrome in Lithuania have impaired cognitive functioning and worse psychological and social aspects of QoL, but not emotional state and physical and environmental aspects of QoL in comparison to age-matched healthy women.

Carriage of Supernumerary Sex Chromosomes Decreases the Volume and Alters the Shape of Limbic Structures

Sex chromosome aneuploidy (SCA) increases risk for several psychiatric disorders associated with the limbic system, including mood and autism spectrum disorders. Thus, SCA offers a genetics-first model for understanding the biological basis of psychopathology. Additionally, the sex-biased prevalence of many psychiatric disorders could potentially reflect sex chromosome dosage effects on brain development. To clarify how limbic anatomy varies across sex and sex chromosome complement, we characterized amygdala and hippocampus structure in a uniquely large sample of patients carrying supernumerary sex chromosomes (n = 132) and typically developing controls (n = 166). After adjustment for sex-differences in brain size, karyotypically normal males (XY) and females (XX) did not differ in volume or shape of either structure. In contrast, all SCAs were associated with lowered amygdala volume relative to gonadally-matched controls. This effect was robust to three different methods for total brain volume adjustment, including an allometric analysis that derived normative scaling rules for these structures in a separate, typically developing population (n = 79). Hippocampal volume was insensitive to SCA after adjustment for total brain volume. However, surface-based analysis revealed that SCA, regardless of specific karyotype, was consistently associated with a spatially specific pattern of shape change in both amygdala and hippocampus. In particular, SCA was accompanied by contraction around the basomedial nucleus of the amygdala and an area crossing the hippocampal tail. These results demonstrate the power of SCA as a model to understand how copy number variation can precipitate changes in brain systems relevant to psychiatric disease.

Normal Performance in Non-Visual Social Cognition Tasks in Women with Turner Syndrome

Turner syndrome (TS) is a chromosomal disorder in women resulting from a partial or complete absence of the X chromosome. In addition to physical and hormonal dysfunctions, along with a unique neurocognitive profile, women with TS are reported to suffer from social functioning difficulties. Yet, it is unclear whether these difficulties stem from impairments in social cognition per se or from other deficits that characterize TS but are not specific to social cognition. Previous research that has probed social functioning in TS is equivocal regarding the source of these psychosocial problems since they have mainly used tasks that were dependent on visual-spatial skills, which are known to be compromised in TS. In the present study, we tested 26 women with TS and 26 matched participants on three social cognition tasks that did not require any visual-spatial capacities but rather relied on auditory-verbal skills. The results revealed that in all three tasks the TS participants did not differ from their control counterparts. The same TS cohort was found, in an earlier study, to be impaired, relative to controls, in other social cognition tasks that were dependent on visual-spatial skills. Taken together these findings suggest that the social problems, documented in TS, may be related to non-specific spatial-visual factors that affect their social cognition skills.

Clinical practice guidelines for the care of girls and women with Turner syndrome: proceedings from the 2016 Cincinnati International Turner Syndrome Meeting

Turner syndrome affects 25-50 per 100,000 females and can involve multiple organs through all stages of life, necessitating multidisciplinary approach to care. Previous guidelines have highlighted this, but numerous important advances have been noted recently. These advances cover all specialty fields involved in the care of girls and women with TS. This paper is based on an international effort that started with exploratory meetings in 2014 in both Europe and the USA, and culminated with a Consensus Meeting held in Cincinnati, Ohio, USA in July 2016. Prior to this meeting, five groups each addressed important areas in TS care: 1) diagnostic and genetic issues, 2) growth and development during childhood and adolescence, 3) congenital and acquired cardiovascular disease, 4) transition and adult care, and 5) other comorbidities and neurocognitive issues. These groups produced proposals for the present guidelines. Additionally, four pertinent questions were submitted for formal GRADE (Grading of Recommendations, Assessment, Development and Evaluation) evaluation with a separate systematic review of the literature. These four questions related to the efficacy and most optimal treatment of short stature, infertility, hypertension, and hormonal replacement therapy. The guidelines project was initiated by the European Society for Endocrinology and the Pediatric Endocrine Society, in collaboration with The European Society for Pediatric Endocrinology, The Endocrine Society, European Society of Human Reproduction and Embryology, The American Heart Association, The Society for Endocrinology, and the European Society of Cardiology. The guideline has been formally endorsed by the European Society for Endocrinology, the Pediatric Endocrine Society, the European Society for Pediatric Endocrinology, the European Society of Human Reproduction and Embryology and the Endocrine Society. Advocacy groups appointed representatives who participated in pre-meeting discussions and in the consensus meeting.

Mapping the effect of the X chromosome on the human brain: Neuroimaging evidence from Turner syndrome

In addition to determining sex, the X chromosome has long been considered to play a crucial role in brain development and intelligence. Turner syndrome (TS) is caused by the congenital absence of all or part of one of the X chromosomes in females. Thus, Turner syndrome provides a unique "knock-out model" for investigating how the X chromosome influences the human brain in vivo. Numerous cutting-edge neuroimaging techniques and analyses have been applied to investigate various brain phenotypes in women with TS, which have yielded valuable evidence toward elucidating the causal relationship between the X chromosome and human brain structure and function. In this review, we comprehensively summarize the recent progress made in TS-related neuroimaging studies and emphasize how these findings have enhanced our understanding of X chromosome function with respect to the human brain. Future investigations are encouraged to address the issues of previous TS neuroimaging studies and to further identify the biological mechanisms that underlie the function of specific X-linked genes in the human brain.