A Cross-Species Neuroimaging Study of Sex Chromosome Dosage Effects on Human and Mouse Brain Anatomy.

All eutherian mammals show chromosomal sex determination with contrasting sex chromosome dosages (SCDs) between males (XY) and females (XX). Studies in transgenic mice and humans with sex chromosome trisomy (SCT) have revealed direct SCD effects on regional mammalian brain anatomy, but we lack a formal test for cross-species conservation of these effects. Here, we develop a harmonized framework for comparative structural neuroimaging and apply this to systematically profile SCD effects on regional brain anatomy in both humans and mice by contrasting groups with SCT (XXY and XYY) versus XY controls. Total brain size was substantially altered by SCT in humans (significantly decreased by XXY and increased by XYY), but not in mice. Robust and spatially convergent effects of XXY and XYY on regional brain volume were observed in humans, but not mice, when controlling for global volume differences. However, mice do show subtle effects of XXY and XYY on regional volume, although there is not a general spatial convergence in these effects within mice or between species. Notwithstanding this general lack of conservation in SCT effects, we detect several brain regions that show overlapping effects of XXY and XYY both within and between species (cerebellar, parietal, and orbitofrontal cortex), thereby nominating high priority targets for future translational dissection of SCD effects on the mammalian brain. Our study introduces a generalizable framework for comparative neuroimaging in humans and mice and applies this to achieve a cross-species comparison of SCD effects on the mammalian brain through the lens of SCT.SIGNIFICANCE STATEMENT Sex chromosome dosage (SCD) affects neuroanatomy and risk for psychopathology in humans. Performing mechanistic studies in the human brain is challenging but possible in mouse models. Here, we develop a framework for cross-species neuroimaging analysis and use this to show that an added X- or Y-chromosome significantly alters human brain anatomy but has muted effects in the mouse brain. However, we do find evidence for conserved cross-species impact of an added chromosome in the fronto-parietal cortices and cerebellum, which point to regions for future mechanistic dissection of sex chromosome dosage effects on brain development.

Incidence of sex chromosome aneuploidy in a prenatal population: 27-year longitudinal study in Northern Italy.

OBJECTIVES: The availability of cell-free (cf) DNA as a prenatal screening tool affords an opportunity for non-invasive identification of sex chromosome aneuploidy (SCA). The aims of this longitudinal study were to investigate the evolution and frequency of both invasive prenatal diagnostic testing, using amniocentesis and chorionic villus sampling (CVS), and the detection of SCA in cfDNA samples from a large unselected cohort in Northern Italy. METHODS: The results of genetic testing from CVS and amniotic fluid samples received from public and private centers in Italy from 1995 to 2021 were collected. Chromosomal analysis was performed by routine Q-banding karyotype. Regression analyses and descriptive statistics were used to determine population data trends regarding the frequency of prenatal diagnostic testing and the identification of SCA, and these were compared with the changes in indication for prenatal diagnostic tests and available screening options. RESULTS: Over a period of 27 years, there were 13 939 526 recorded births and 231 227 invasive procedures were performed, resulting in the prenatal diagnosis of 933 SCAs. After the commercial introduction of cfDNA use in 2015, the frequency of invasive procedures decreased significantly (P = 0.03), while the frequency of prenatal SCA detection increased significantly (P = 0.007). Between 2016 and 2021, a high-risk cfDNA result was the indication for 31.4% of detected sex chromosome trisomies, second only to advanced maternal age. CONCLUSIONS: Our findings suggest that the inclusion of SCA in prenatal cfDNA screening tests can increase the prenatal diagnosis of affected individuals. As the benefits of early ascertainment are increasingly recognized, it is essential that healthcare providers are equipped with comprehensive and evidence-based information regarding the associated phenotypic differences and the availability of targeted effective interventions to improve neurodevelopmental and health outcomes for affected individuals. © 2023 International Society of Ultrasound in Obstetrics and Gynecology.

Early symptoms of autism spectrum disorder (ASD) in 1-8 year old children with sex chromosome trisomies (XXX, XXY, XYY), and the predictive value of joint attention.

The objective of the present study is to investigate the impact of Sex Chromosome Trisomy (SCT; XXX, XXY, XYY) on the early appearance of Autism Spectrum Disorder (ASD) symptoms, and the predictive value of Joint Attention for symptoms of ASD. SCTs are specific genetic conditions that may serve as naturalistic 'at risk' models of neurodevelopment, as they are associated with increased risk for neurobehavioral vulnerabilities. A group of 82 children with SCT (aged 1-8 years) was included at baseline of this longitudinal study. Joint Attention was measured at baseline with structured behavior observations according to the Early Social Communication Scales. ASD symptoms were assessed with the Modified Checklist for Autism in Toddlers questionnaire and Autism Diagnostic Interview-Revised in a 1-year follow-up. Recruitment and assessment took place in the Netherlands and in the United States. The results demonstrate that ASD symptoms were substantially higher in children with SCT compared to the general population, with 22% of our cohort at clinical risk for ASD, especially in the domain of social interaction and communication. Second, a predictive value of Joint Attention was found for ASD symptoms at 1-year follow-up. In this cohort, no differences were found between karyotype-subtypes. In conclusion, from a very early age, SCT can be associated with an increased risk for vulnerabilities in adaptive social functioning. These findings show a neurodevelopmental impact of the extra X or Y chromosome on social adaptive development associated with risk for ASD already from early childhood onward. These findings advocate for close monitoring and early (preventive) support, aimed to optimize social development of young children with SCT.

The behavioral profile of children aged 1-5 years with sex chromosome trisomy (47,XXX, 47,XXY, 47,XYY).

Children with SCT have an increased risk of suboptimal neurodevelopment. Previous studies have shown an elevated risk for neurobehavioral problems in individuals with SCT. However, not much is known about neurobehavioral problems in very young children; knowledge that could help with early identification of children at risk for suboptimal development, and that could help establish targets for early intervention. This study addressed the question of what the behavioral profile of children with SCT aged 1-5 years looks like. In total, 182 children aged 1-5 years participated in this study (NSCT =87, Nnonclinical controls = 95). Recruitment and assessment took place in the Netherlands and the United States. The SCT group was recruited through prospective follow-up (50%), information seeking parents (31%), and clinical referral (18%). Behavioral profiles were assessed with the child behavior checklist and the ages-and-stages social-emotional questionnaire. Levels of parent-rated problem behavior were higher in children with SCT. Difficulties with overall social-emotional functioning were already present in 1-year-olds, and elevated scores were persistent across the full age range. Affective and pervasive developmental behaviors were seen in late toddlerhood and prominent at preschool age. Anxiety, attention deficit, and oppositional defiant behaviors were seen in preschool-aged children. Within this cross-sectional study, the developmental trajectory of affective, pervasive developmental, and oppositional defiant behaviors seemed to be different for SCT children than nonclinical controls. Collectively, these results demonstrate the importance of behavioral screening for behavioral problems in routine clinical care for children with SCT from a young age. Social-emotional problems may require special attention, as these problems seem most prominent, showing increased risk across the full age range, and with these problems occurring regardless of the timing of diagnosis, and across all three SCT karyotypes.

Copy number variation burden does not predict severity of neurodevelopmental phenotype in children with a sex chromosome trisomy.

Sex chromosome trisomies (SCTs) (XXX, XXY, and XYY karyotypes) are associated with an elevated risk of neurodevelopmental disorders. The range of severity of the phenotype is substantial. We considered whether this variable outcome was related to the presence of copy number variants (CNVs)-stretches of duplicated or deleted DNA. A sample of 125 children with an SCT were compared with 181 children of normal karyotype who had been given the same assessments. First, we compared the groups on measures of overall CNV burden: number of CNVs, total span of CNVs, and likely functional impact (probability of loss-of-function intolerance, pLI, summed over CNVs). Differences between groups were small relative to within-group variance and not statistically significant on overall test. Next, we considered whether a measure of general neurodevelopmental impairment was predicted by pLI summed score, SCT versus comparison group, or the interaction between them. There was a substantial effect of SCT/comparison status but the pLI score was not predictive of outcomes in either group. We conclude that variable presence of CNVs is not a likely explanation for the wide phenotypic variation in children with SCTs. We discuss methodological challenges of testing whether CNVs are implicated in causing neurodevelopmental problems.

Structural and pragmatic language in young children with sex chromosome trisomy (XXX, XXY, XYY): Predictive value for neurobehavioral problems one year later.

Objective: To investigate pragmatic language abilities in young children with an increased risk for adverse neurobehavioral and neurocognitive outcomes due to an extra X or Y chromosome (sex chromosome trisomy; SCT) and to investigate to what degree early structural and pragmatic language abilities are predictive of neurobehavioral problems one year later. Method: In total, 72 children with SCT and 71 controls aged 3-7 years were included. Language assessments included parent-reported pragmatic language skills and direct assessment of structural language abilities. Parent-reported behavioral outcomes were measured one year after the initial language assessment. Results: Children with SCT demonstrated weaker pragmatic language skills compared to controls. These differences were not driven by karyotype, time of diagnosis, or ascertainment bias and irrespective of the presence of structural language impairment. Odds of having pragmatic difficulties was 23 times higher in the SCT group, with 25% of the children not meeting age-expectations. In addition, language, in particular pragmatic language, was an important predictor for later affective, oppositional defiant, pervasive developmental, attention deficit, and social-emotional problems in young children with SCT. Conclusions: This study is one of the first studies that directly illustrates the relationship between language and behavioral outcomes in children with SCT. Our results stress the importance to closely monitor pragmatic language in addition to structural language in clinical care of children with SCT, as pragmatic language abilities could serve as an early marker for children at risk for developing behavioral problems.

Social Communication in Young Children With Sex Chromosome Trisomy (XXY, XXX, XYY): A Study With Eye Tracking and Heart Rate Measures.

OBJECTIVE: Children with sex chromosome trisomy (SCT) have an increased risk for suboptimal development. Difficulties with language are frequently reported, start from a very young age, and encompass various domains. This cross-sectional study examined social orientation with eye tracking and physiological arousal responses to gain more knowledge on how children perceive and respond to communicative bids and evaluated the associations between social orientation and language outcomes, concurrently and 1 year later. METHOD: In total, 107 children with SCT (33 XXX, 50 XXY, and 24 XYY) and 102 controls (58 girls and 44 boys) aged between 1 and 7 years were included. Assessments took place in the USA and Western Europe. A communicative bids eye tracking paradigm, physiological arousal measures, and receptive and expressive language outcomes were used. RESULTS: Compared to controls, children with SCT showed reduced attention to the face and eyes of the on-screen interaction partner and reduced physiological arousal sensitivity in response to direct versus averted gaze. In addition, social orientation to the mouth was related to concurrent receptive and expressive language abilities in 1-year-old children with SCT. CONCLUSIONS: Children with SCT may experience difficulties with social communication that extend past the well-recognized risk for early language delays. These difficulties may underlie social-behavioral problems that have been described in the SCT population and are an important target for early monitoring and support.

Does the autism phenotype differ when selecting groups by neurodevelopmental versus genetic diagnosis? An observational study comparing autism and sex chromosome trisomy.

Background: Autism is diagnosed on the basis of social and non-social behavioural features that are assumed to cluster together, and assumed to be distinct from other aspects of development, such as language ability. It is unclear, however, if these assumptions are valid. This study presents a novel approach to answering this question by investigating whether correlations between autism features are similar for groups selected on behavioural versus genetic diagnosis. Methods: The autism phenotype was assessed by diagnostic interview in young people aged 7 to 14 diagnosed with autism ( N=61) or sex chromosome trisomy (SCT; N=49). Data were analysed by confirmatory factor analysis and MANOVA. Results: Autism features showed a similar factor structure and were distinct from language ability in both groups. However, the SCT group was more likely to show clinically-significant difficulties in just some aspects of autism and a lower level of non-social autism features for their social-communication disabilities. Conclusions: We suggest the group differences emerged because autism diagnostic criteria do not map exactly on the autism phenotype as it manifests "naturally". Conventional diagnostic criteria for autism miss those with uneven profiles of difficulty and those with relatively low levels of restricted and repetitive behaviours and interests.

[Formula: see text]A cross-sectional study of early language abilities in children with sex chromosome trisomy (XXY, XXX, XYY) aged 1-6 years.

Children with sex chromosome trisomy (SCT) are at increased risk for developing language difficulties. Earlier studies have reported that as many as 70-80% of individuals with SCT show some form of language difficulties. Language develops rapidly in the first years of life; knowledge about language development at an early age is needed. The present study aims to identify the language abilities of young children with SCT across multiple language domains and to identify the percentage of children that, according to clinical guidelines, have language difficulties. Children between the ages of 1-6-years (NSCT = 103, Ncontrols = 102) were included. Nonverbal communication, early vocabulary, semantic, syntax, and phonological skills were assessed. Language difficulties were already present in 1-year-old children with SCT and across the age range in various language domains. Clinical classification showed that, depending on the assessed domain, 14.8-50.0% of the children scored below the 16th percentile. There was no effect of time of diagnosis, ascertainment bias, research site, nor SCT specific karyotype (XXX, XXY, XYY) on language outcomes. Overall, language difficulties can already be present in very young children with SCT within various language domains. These findings appear to be robust within the SCT group. These results highlight the importance of monitoring both receptive and expressive language development already at the earliest stages of nonverbal communication. Finally, as early language skills are the building blocks for later social communication, literacy, and self-expression, studies that investigate the effect of early interventions on later language outcomes are warranted.

The Impact of Sex Chromosome Trisomies (XXX, XXY, XYY) on Early Social Cognition: Social Orienting, Joint Attention, and Theory of Mind.

OBJECTIVE: About 1:650-1,000 children are born with an extra X or Y chromosome (XXX; XXY; XYY), which results in a sex chromosome trisomy (SCT). This study aims to cross-sectionally investigate the impact of SCT on early social cognitive skills. Basic orienting toward social cues, joint attention, and theory of mind (ToM) in young children with SCT were evaluated. METHOD: About 105 children with SCT (range: 1-7 years old) were included in this study, as well as 96 age-matched nonclinical controls. Eyetracking paradigms were used to investigate the eye gaze patterns indicative of joint attention skills and orienting to social interactions. The ToM abilities were measured using the subtest ToM of the Developmental NEuroPSYchological Assessment, second edition, neuropsychological test battery. Recruitment and assessment took place in the Netherlands and in the United States. RESULTS: Eyetracking results revealed difficulties in children with SCT in social orienting. These difficulties were more pronounced in children aged 3 years and older, and in boys with 47,XYY. Difficulties in joint attention were found over all age groups and karyotypes. Children with SCT showed impairments in ToM (26.3% in the [well] below expected level), increasing with age. These impairments did not differ between karyotypes. CONCLUSIONS: An impact of SCT on social cognitive abilities was found already at an early age, indicating the need for early monitoring and support of early social cognition. Future research should explore the longitudinal trajectories of social development in order to evaluate the predictive relationships between social cognition and outcome later in life in terms of social functioning and the risk for psychopathology.

Stage 1 Registered Report: Variation in neurodevelopmental outcomes in children with sex chromosome trisomies: protocol for a test of the double hit hypothesis.

Background: The presence of an extra sex chromosome is associated with an increased rate of neurodevelopmental difficulties involving language. Group averages, however, obscure a wide range of outcomes. Hypothesis: The 'double hit' hypothesis proposes that the adverse impact of the extra sex chromosome is amplified when genes that are expressed from the sex chromosomes interact with autosomal variants that usually have only mild effects. Neuroligin-4 genes are expressed from X and Y chromosomes; they play an important role in synaptic development and have been implicated in neurodevelopment. We predict that the impact of an additional sex chromosome on neurodevelopment will be correlated with common autosomal variants involved in related synaptic functions.  We describe here an analysis plan for testing this hypothesis using existing data. The analysis of genotype-phenotype associations will be conducted after this plan is published and peer-reviewed Methods: Neurodevelopmental data and DNA are available for 130 children with sex chromosome trisomies (SCTs: 42 girls with trisomy X, 43 boys with Klinefelter syndrome, and 45 boys with XYY). Children from a twin study using the same phenotype measures will form two comparison groups (Ns = 184 and 186). Three indicators of a neurodevelopment disorder phenotype will be used: (i) Standard score on a test of nonword repetition; (ii). A language factor score derived from a test battery; (iii) A general scale of neurodevelopmental challenges based on all available information. Autosomal genes were identified by literature search on the basis of prior association with (a) speech/language/reading phenotypes and (b) synaptic function. Preselected regions of two genes scoring high on both criteria, CNTNAP2 and NRXN1, will be tested for association with neurodevelopmental outcomes using Generalised Structural Component Analysis. We predict the association with one or both genes will be detectable in children with SCTs and stronger than in the comparison samples.

Stage 2 Registered Report: Variation in neurodevelopmental outcomes in children with sex chromosome trisomies: testing the double hit hypothesis.

Background: The presence of an extra sex chromosome is associated with an increased rate of neurodevelopmental difficulties involving language. The 'double hit' hypothesis proposes that the adverse impact of the extra sex chromosome is amplified when genes that are expressed from the sex chromosomes interact with autosomal variants that usually have only mild effects. We predicted that the impact of an additional sex chromosome on neurodevelopment would depend on common autosomal variants involved in synaptic functions.   Methods: We analysed data from 130 children with sex chromosome trisomies (SCTs: 42 girls with trisomy X, 43 boys with Klinefelter syndrome, and 45 boys with XYY). Two comparison groups were formed from 370 children from a twin study. Three indicators of phenotype were: (i) Standard score on a test of nonword repetition; (ii). A language factor score derived from a test battery; (iii) A general scale of neurodevelopmental challenges based on all available information. Preselected regions of two genes, CNTNAP2 and NRXN1, were tested for association with neurodevelopmental outcomes using Generalised Structural Component Analysis. Results: There was wide phenotypic variation in the SCT group, as well as overall impairment on all three phenotypic measures. There was no association of phenotype with CNTNAP2 or NRXN1 variants in either the SCT group or the comparison groups. Supplementary analyses found no indication of any impact of trisomy type on the results, and exploratory analyses of individual SNPs confirmed the lack of association. Conclusions: We cannot rule out that a double hit may be implicated in the phenotypic variability in children with SCTs, but our analysis does not find any support for the idea that common variants in CNTNAP2 or NRXN1 are associated with the severity of language and neurodevelopmental impairments that often accompany an extra X or Y chromosome. Stage 1 report: http://dx.doi.org/10.12688/wellcomeopenres.13828.2.