Brain morphological abnormalities in 49,XXXXY syndrome: A pediatric magnetic resonance imaging study

An Animal Model of Neonatal Intensive Care Unit Exposure to Light and Sound in the Preterm Infant

According to the World Health Organization, ∼15 million children are born prematurely each year. Many of these infants end up spending days to weeks in a neonatal intensive care unit (NICU). Infants who are born prematurely are often exposed to noise and light levels that affect their auditory and visual development. Children often have long-term impairments in cognition, visuospatial processing, hearing, and language. We have developed a rodent model of NICU exposure to light and sound using the Mongolian gerbil (Meriones unguiculatus), which has a low-frequency human-like audiogram and is altricial. To simulate preterm infancy, the eyes and ears were opened prematurely, and animals were exposed to the NICU-like sensory environment throughout the gerbil's cortical critical period of auditory development. After the animals matured into adults, auditory perceptual testing was carried out followed by auditory brainstem response recordings and then histology to assess the white matter morphology of various brain regions. Compared to normal hearing control animals, NICU sensory-exposed animals had significant impairments in learning at later stages of training, increased auditory thresholds reflecting hearing loss, and smaller cerebellar white matter volumes. These have all been reported in longitudinal studies of preterm infants. These preliminary results suggest that this animal model could provide researchers with an ethical way to explore the effects of the sensory environment in the NICU on the preterm infant's brain development.

Clinical, Cognitive and Neurodevelopmental Profile in Tetrasomies and Pentasomies: A Systematic Review

Background: Sex chromosome aneuploidies (SCAs) are a group of disorders characterised by an abnormal number of sex chromosomes. Collective prevalence rate of SCAs is estimated to be around 1 in 400-500 live births; sex chromosome trisomies (e.g., XXX, XXY, XYY) are most frequent, while tetra- and pentasomies (e.g., XXXX, XXXXX, XXXY, XXXXY) are rarer, and the most common is 48, XXYY syndrome. The presence of additional X and/or Y chromosomes is believed to cause neurodevelopmental differences, with increased risk for developmental delays, language-based learning disabilities, cognitive impairments, executive dysfunction, and behavioural and psychological disorders. Aim of the Study: Our review has the purpose of analysing the neurocognitive, linguistical and behavioural profile of patients affected by sex chromosomes supernumerary aneuploidies (tetrasomy and pentasomy) to better understand the specific areas of weakness, in order to provide specific rehabilitation therapy. Methods: The literature search was performed by two authors independently. We used MEDLINE, PubMed, and PsycINFO search engines to identify sources of interest, without year or language restrictions. At the end of an accurate selection, 16 articles fulfilled the inclusion and exclusion criteria. Results and Conclusions: International literature has described single aspects of the neuropsychological profile of 48, XXYY and 49, XXXXY patients. In 48, XXYY patients, various degrees of psychosocial/executive functioning issues have been reported and there is an increased frequency of behavioural problems in childhood. Developmental delay and behavioural problems are the most common presenting problems, even if anxiety, depression and oppositional defiant disorder are also reported. They also show generalized difficulties with socialization and communication. Cognitive abilities are lower in measures of verbal IQ than in measures of performance IQ. Visuospatial skills are a relative strength compared to verbal skills. In patients with 49, XXXXY, both intellectual and adaptive functioning skills fall into the disability range, with better non-verbal cognitive performance. Speech and language testing reveals more deficits in expressive language than receptive language and comprehension. Anxiety, thought problems, internalizing and externalizing problems, and deficits in social cognition and communication are reported. Behavioural symptoms lessen from school age to adolescence, with the exception of thought problems and anxiety. Individuals affected by sex chromosome aneuploidies show testosterone deficiency, microorchidism, lack of pubertal progression and infertility. Hormone replacement therapy (HRT) is usually recommended for these patients: different studies have found that testosterone-based HRT benefit a wide range of areas initiated in these disorders, affecting not only neuromotor, cognitive and behavioural profile but also structural anomalies of the brain (i.e., increase of volume of grey temporal lobe matter). In conclusion, further studies are needed to better understand the neuropsychological profile with a complete evaluation, including neurocognitive and psychosocial aspects and to establish the real impact of HRT on improving the cognitive and behavioural profile of these patients.

Regional White Matter Scaling in the Human Brain

Anatomical organization of the primate cortex varies as a function of total brain size, where possession of a larger brain is accompanied by disproportionate expansion of associative cortices alongside a relative contraction of sensorimotor systems. However, equivalent scaling maps are not yet available for regional white matter anatomy. Here, we use three large-scale neuroimaging datasets to examine how regional white matter volume (WMV) scales with interindividual variation in brain volume among typically developing humans (combined N = 2391: 1247 females, 1144 males). We show that WMV scaling is regionally heterogeneous: larger brains have relatively greater WMV in anterior and posterior regions of cortical white matter, as well as the genu and splenium of the corpus callosum, but relatively less WMV in most subcortical regions. Furthermore, regions of positive WMV scaling tend to connect previously-defined regions of positive gray matter scaling in the cortex, revealing a coordinated coupling of regional gray and white matter organization with naturally occurring variations in human brain size. However, we also show that two commonly studied measures of white matter microstructure, fractional anisotropy (FA) and magnetization transfer (MT), scale negatively with brain size, and do so in a manner that is spatially unlike WMV scaling. Collectively, these findings provide a more complete view of anatomic scaling in the human brain, and offer new contexts for the interpretation of regional white matter variation in health and disease.SIGNIFICANCE STATEMENT Recent work has shown that, in humans, regional cortical and subcortical anatomy show systematic changes as a function of brain size variation. Here, we show that regional white matter structures also show brain-size related changes in humans. Specifically, white matter regions connecting higher-order cortical systems are relatively expanded in larger human brains, while subcortical and cerebellar white matter tracts responsible for unimodal sensory or motor functions are relatively contracted. This regional scaling of white matter volume (WMV) is coordinated with regional scaling of cortical anatomy, but is distinct from scaling of white matter microstructure. These findings provide a more complete view of anatomic scaling of the human brain, with relevance for evolutionary, basic, and clinical neuroscience.

array-CGH revealed gain of Yp11.2 in 49,XXXXY and gain of Xp22.33 in 48,XXYY karyotypes of two rare klinefelter variants

Klinefelter syndrome (KS) variants often share common features with classical syndrome but some of these variants present with a distinct phenotype. The incidence of sex chromosome tetrasomy and pentasomy are very less and generally diagnosed after prepubertal age. The early diagnosis of complex and unclassified syndromes and it's correlation with genotype is necessary for personalized treatment as well as genetic counselling of the affected families. We describe clinical presentation, and genetic diagnosis of two cases of variant KS. Our first case, a 4 year old male child presented with generalized tonic-clonic seizures (GTCSs), delayed milestones and dysmorphic features while case 2, a-21 years old male who had history of seizures and delayed puberty came to our lab for genetic diagnosis. The chromosomal analysis of case 1 and 2 showed 49,XXXXY and 48,XXYY karyotype respectively. The karyotype results were confirmed with fluorescence in situ hybridization (FISH) and array-CGH analysis. The FISH results were found to be consistent with karyotype but the array-CGH results showed the extra gain of region Yp11.2 in case 1 while the extra gain of region Xp22.33 in case 2. The cases were confirmed as variant KS on the basis of additional sex chromosomes and clinical presentation of deteriorated brain development. The present study suggests that the high doses of sex chromosome linked genes including pseudoautosomal region (PAR) caused the abnormal brain development. The combination of molecular techniques should be utilized for the diagnosis of such complex cases to understand the genotype-phenotype correlation and appropriate genetic counseling.

Neurocognitive development and capabilities in boys with 49,XXXXY syndrome

49,XXXXY was previously associated with profound to severe intellectual deficits. However, prior research papers on the cognitive profiles of this population were confounded by small samples sizes, wide age spreads, and incomplete histories of testosterone replacement therapy. This study is the first comprehensive, international investigation of the neurocognitive aspects of 49,XXXXY, and the potential effects of biological treatment on this profile. Sixty-seven boys from infancy to 11 years of age were enrolled in this longitudinal study, with the majority of boys postnatally diagnosed though chromosomal analysis. These boys received a comprehensive neurocognitive evaluation tailored to specific language-based deficits and cognitive challenges. Results revealed higher neurocognitive capacities, both verbally and nonverbally, than previously reported in this disorder. Infant boys with 49,XXXXY who received early hormonal therapy (EHT) had significantly higher scores on the cognitive domain of the Bayley Scales of Infant Development than untreated infants (p = .013). In addition, treated school-aged participants had significantly better scaled scores than untreated boys in form completion (p = .042), a task that requires deductive reasoning, on nonverbal testing on the Leiter International Performance Scales. This study indicates greater cognitive capacities with a wide range of abilities in the child with 49,XXXXY, thus warranting further investigation to identify and understand the critical influences on the etiology and the variability of those capacities.

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.

Behavioral phenotype of 49,XXXXY syndrome: Presence of anxiety-related symptoms and intact social awareness

49,XXXXY is a rare X and Y chromosome variation that occurs in 1:85,000 to 1:100,000 live male births and is notable for variable motor, speech, and behavioral deficits. Case studies have described boys with this disorder as shy, impulsive, and aggressive with low frustration tolerances; however, previous studies have been limited due to cohort size. This study reports on the largest cohort of boys with 49,XXXXY to date with an emphasis on the prevalence of anxiety-related symptoms and sociability from preschool to adolescence. The Child Behavior Checklist, Behavior Rating Inventory of Executive Function, 2nd edition, and Social Responsiveness Scale, 2nd edition were completed by parents on a cohort of 69. The cohort demonstrated deficits in social cognition and communication beginning in preschool, however, presented with consistent social awareness and motivation for social activities not previously appreciated in this disorder. In addition, signs of anxiety presented during preschool years and increased in severity with age, particularly in internalizing problems. Boys with 49,XXXXY presented with wide behavioral variability across all ages and domains. Further research into the potential influences of culture, birth order, biological treatment, and frequency of services is needed to better define the behavioral phenotype of children with this disorder.

Clinical report of 8 patients with 49,XXXXY syndrome: Delineation of the facial gestalt and depiction of the clinical spectrum

49,XXXXY syndrome is a rare sex chromosome aneuploidy syndrome. Cognitive impairment with expressive language deficits in combination with developmental and speech dyspraxia are cardinal symptoms. Testicular insufficiency becomes apparent during adolescence. Neurological, musculoskeletal, genital, orthodontic and immunological anomalies are common and a higher incidence of congenital malformations has been described. Here we show the evolving clinical and facial phenotype of eight boys and men with 49,XXXXY, demonstrating an increasingly perceptible distinct facial gestalt over time. In addition, almost all patients had muscular hypotonia, radioulnar synostosis, white matter anomalies, fifth-finger clinodactyly, recurrent respiratory infections in early childhood and teeth anomalies. IQ scores ranged between 40 and 70. Though many boys showed short stature at some point in early childhood, most outgrew it. As more long term data of boys and men with 49,XXXXY become available, parents of affected boys can be counseled more specifically as to the expected course and spectrum of this rare chromosomal disorder. Moreover, the multidisciplinary support can be optimized und unnecessary diagnostics avoided.

Severe myelinopathy in 49,XXXXY syndrome

49,XXXXY is a rare aneuploidy with neuroanatomic findings scarcely reported in the literature. Given the fact that many of its phenotypic characteristics are similar to Klinefelter patients, 49,XXXXY has been treated as a variant of Klinefelter syndrome in the past. Newer studies have shown that intellectual disabilities and cardiac sequelae are more common in 49,XXXXY making the need for more precise characterization of the disorder essential. Prior case studies have demonstrated focal (and to a lesser extent confluent) white abnormalities as well as enlarged perivascular cysts (often in clustered arrangements) in the brains of these patients, but high resolution magnetic resonance images of severe myelinopathy are infrequently documented. Presented here is an exceptional manifestation of this rare disease with substantial findings in the brain exhibiting both confluent white matter changes and diffuse perivascular cysts. Cases such as this one serve to expand the differential considerations for confluent dysmyelinating disease and improve diagnostic efficacy.

An Allometric Analysis of Sex and Sex Chromosome Dosage Effects on Subcortical Anatomy in Humans

Structural neuroimaging of humans with typical and atypical sex-chromosome complements has established the marked influence of both Yand X-/Y-chromosome dosage on total brain volume (TBV) and identified potential cortical substrates for the psychiatric phenotypes associated with sex-chromosome aneuploidy (SCA). Here, in a cohort of 354 humans with varying karyotypes (XX, XY, XXX, XXY, XYY, XXYY, XXXXY), we investigate sex and SCA effects on subcortical size and shape; focusing on the striatum, pallidum and thalamus. We find large effect-size differences in the volume and shape of all three structures as a function of sex and SCA. We correct for TBV effects with a novel allometric method harnessing normative scaling rules for subcortical size and shape in humans, which we derive here for the first time. We show that all three subcortical volumes scale sublinearly with TBV among healthy humans, mirroring known relationships between subcortical volume and TBV among species. Traditional TBV correction methods assume linear scaling and can therefore invert or exaggerate sex and SCA effects on subcortical anatomy. Allometric analysis restricts sex-differences to: (1) greater pallidal volume (PV) in males, and (2) relative caudate head expansion and ventral striatum contraction in females. Allometric analysis of SCA reveals that supernumerary X- and Y-chromosomes both cause disproportionate reductions in PV, and coordinated deformations of striatopallidal shape. Our study provides a novel understanding of sex and sex-chromosome dosage effects on subcortical organization, using an allometric approach that can be generalized to other basic and clinical structural neuroimaging settings.

Frontal Aslant Tract Abnormality on Diffusion Tensor Imaging in an Aphasic Patient With 49, XXXXY Syndrome

BACKGROUND

The karyotype 49, XXXXY is one of the most severe forms of chromosome aneuploidy and is characterized clinically by developmental delay and profound language impairment, particularly involving expressive language functions. We describe the neurocognitive profile and structural anatomy of language pathway in a 2-year-old boy with 49, XXXXY syndrome with expressive aphasia.

METHODS

Retrospective chart review of the patient was performed. We characterized the language deficits using neuropsychologic testing. We further studied the language pathways using diffusion tensor imaging analytical technique.

RESULTS

The neurocognitive profile of the patient showed relative weakness of expressive language skills compared with other domains. Diffusion tensor imaging analysis demonstrated a poorly developed frontal aslant tract, a weak indirect segment of arcuate fasciculus, and normally developed direct segment of arcuate fasciculus. The frontal aslant tract is a novel pathway that connects the Broca's area with the anterior cingulate and presupplementary motor area and plays a role in the "motor stream" of language.

CONCLUSION

A poorly developed frontal aslant tract may underlie the expressive language deficits and provide some insight into the role of X chromosome in modulating the development of language tracts.

Leydig cell tumor in a patient with 49,XXXXY karyotype: a review of literature

49,XXXXY pentasomy or Fraccaro's syndrome is the most severe variant of Klinefelter's syndrome (KS) affecting about 1/85000 male births. The classical presentation is the triad: mental retardation, hypergonadotropic hypogonadism and radio ulnar synostosis. Indeed, the reproductive function of Fraccaro's syndrome is distinguished from KS. Besides, Leydig cell tumors are described in cases of KS, but never documented in the Klinefelter variants.We describe a young adult of 22 years old who presented with hyper gonadotropic hypogonadism, delayed puberty and bilateral micro-cryptorchidism. Chromosomal pentasomy was confirmed since infancy. Bilateral orchidectomy revealed a unilateral well-circumscribed Leydig cell tumor associated with bilateral Leydig cell hyperplasia.Inspired from reporting the first case of Leydig cell tumor in a 49,XXXXY patient, we summarize the particularities of testicular function in 49,XXXXY from one side, and the risk and mechanisms of Leydig cell tumorigenesis in Klinefelter variants on the other side. The histological destructions in 49,XXXXY testes and hypogonadism are more profound than in Klinefelter patients, with early Sertoli, Leydig and germ cell destruction. Furthermore, the risk of Leydigioma development in KS and its variants remains a dilemma. We believe that the risk of Leydigioma is much higher in KS than the general population. By contrast, the risk could be lower in the Klinefelter variants with more than 3 supplementary X chromosomes, owing to an earlier and more profound destruction of Leydig cells rendering them irresponsive to chronic Luteinizing hormone (LH) stimulation.

Genetic influences on brain developmental trajectories on neuroimaging studies: from infancy to young adulthood

Human brain development has been studied intensively with neuroimaging. However, little is known about how genes influence developmental brain trajectories, even though a significant number of genes (about 10,000, or approximately one-third) in the human genome are expressed primarily in the brain and during brain development. Interestingly, in addition to showing differential expression among tissues, many genes are differentially expressed across the ages (e.g., antagonistic pleiotropy). Age-specific gene expression plays an important role in several critical events in brain development, including neuronal cell migration, synaptogenesis and neurotransmitter receptor specificity, as well as in aging and neurodegenerative disorders (e.g., Alzheimer disease or amyotrophic lateral sclerosis). In addition, the majority of psychiatric and mental disorders are polygenic, and many have onsets during childhood and adolescence. In this review, we summarize the major findings from neuroimaging studies that link genetics with brain development, from infancy to young adulthood. Specifically, we focus on the heritability of brain structures across the ages, age-related genetic influences on brain development and sex-specific developmental trajectories.

Brain and behavior in 48, XXYY syndrome

The phenotype of 48, XXYY syndrome (referred to as XXYY) is associated with characteristic but variable developmental, cognitive, behavioral and physical abnormalities. To discern the neuroanatomical phenotype of the syndrome, we conducted quantitative and qualitative analyses on MRI brain scans from 25 males with XXYY and 92 age and SES matched typically developing XY males. Quantitatively, males in the XXYY group had smaller gray and white matter volumes of the frontal and temporal lobes. Conversely, both gray and white matter volumes of the parietal lobe as well as lateral ventricular volume were larger in the XXYY group. Qualitatively, males in the XXYY group had a higher incidence of colpocephaly (84% vs. 34%, p ≤ 0.001), white matter lesions (25% vs. 5%, p = 0.007), and thin posterior body of the corpus callosum (28% vs. 3%, p = 0.001). The specificity of these findings may shed light on the role of the X and Y chromosomes in typical and atypical brain development and help provide direction for future studies of brain-behavior relationships in males with XXYY syndrome.

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.

Epigenomic and transcriptomic signatures of a Klinefelter syndrome (47,XXY) karyotype in the brain

Klinefelter syndrome (KS) is the most common sex-chromosome aneuploidy in humans. Most affected individuals carry one extra X-chromosome (47,XXY karyotype) and the condition presents with a heterogeneous mix of reproductive, physical and psychiatric phenotypes. Although the mechanism(s) by which the supernumerary X-chromosome determines these features of KS are poorly understood, skewed X-chromosome inactivation (XCI), gene-dosage dysregulation, and the parental origin of the extra X-chromosome have all been implicated, suggesting an important role for epigenetic processes. We assessed genomic, methylomic and transcriptomic variation in matched prefrontal cortex and cerebellum samples identifying an individual with a 47,XXY karyotype who was comorbid for schizophrenia and had a notably reduced cerebellum mass compared with other individuals in the study (n = 49). We examined methylomic and transcriptomic differences in this individual relative to female and male samples with 46,XX or 46,XY karyotypes, respectively, and identified numerous locus-specific differences in DNA methylation and gene expression, with many differences being autosomal and tissue-specific. Furthermore, global DNA methylation, assessed via the interrogation of LINE-1 and Alu repetitive elements, was significantly altered in the 47,XXY patient in a tissue-specific manner with extreme hypomethylation detected in the prefrontal cortex and extreme hypermethylation in the cerebellum. This study provides the first detailed molecular characterization of the prefrontal cortex and cerebellum from an individual with a 47,XXY karyotype, identifying widespread tissue-specific epigenomic and transcriptomic alterations in the brain.