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

The testicular microvasculature in Klinefelter syndrome is immature with compromised integrity and characterized by excessive inflammatory cross-talk

STUDY QUESTION

Does Klinefelter syndrome (KS) lead to a distinct gene expression pattern at single-cell level in the testes that could provide insight into the reported microvascular dysfunction in the testes?

SUMMARY ANSWER

A distinct gene expression pattern within microvascular-associated cells of males with KS suggests excessive endothelial cell (EC) activation, disorganized vessel formation, and the presence of immature vessels with compromised integrity.

WHAT IS KNOWN ALREADY

Recent studies show that males with KS exhibit microvascular dysfunction in their testes, which affects blood flow and is associated with lower circulating levels of testosterone.

STUDY DESIGN, SIZE, DURATION

A comparative cross-sectional study of males with KS (n = 6), non-obstructive azoospermia (NOA) (n = 5), cryptozoospermia (n = 3), and controls (n = 15) was carried out.

PARTICIPANTS/MATERIALS, SETTING, METHODS

We analyzed publicly available single-cell RNA sequencing data of testicular cells from males with KS, males with NOA, males with cryptozoospermia, and controls. The integration of these datasets allowed us to analyze gene expression profiles and communication patterns among the cell types within the testis and to identify capillary ECs to investigate changes at the microvascular level.

MAIN RESULTS AND THE ROLE OF CHANCE

Rooted in changes at the single-cell level, our study demonstrates a shift in gene expression forming the foundation for altered cellular communication, microvascular remodeling, and pro-inflammatory responses within the testes of males with KS. We identified genes that were dysregulated in capillary ECs from males with KS (Padj < 0.05). Specifically, the unique microvascular gene expression in males with KS indicated enhanced capillary EC activation and increased inflammatory cross-talk, leading to impaired vessel maturation and increased EC barrier permeability.

LIMITATIONS, REASONS FOR CAUTION

Our study is constrained by an unbalanced design, with varying sample sizes and number of cells within each group. We acknowledge the restricted access to clinical information. In addition, our findings were deduced from changes in gene expression, which limits us to infer potential biological consequences arising from these alterations. Furthermore, the absence of a pre-pubertal age group limits the generalizability of our findings and warrants further investigation.

WIDER IMPLICATIONS OF THE FINDINGS

This study offers novel insights into the testicular pathophysiology in KS and underscores the potential contribution of microvascular dysfunction to the hypogonadism and infertility observed in males with KS. While this study aims to better understand the microvascular dysfunction in KS, the precise connections to testosterone deficiency and testicular atrophy remain to be fully elucidated.

STUDY FUNDING/COMPETING INTEREST(S)

A.S. was supported by the Independent Research Fund Denmark (0134-00130B). C.H.G. was supported by Novo Nordisk Foundation (NNF15OC0016474, NNF20OC0060610), 'Fonden til lægevidenskabens fremme', the Familien Hede Nielsen foundation and the Independent Research Fund Denmark (0134-00406A). E.B.J. was supported by Aarhus University and E.B.J. and C.H.G by the Independent Research Fund Denmark (2096-00165A). J.M.K. was supported by Lundbeckfonden (R307-2018-3667), Carlsberg Fonden (CF19-0687), Novo Nordisk Fonden (0073440) and Steno Diabetes Center Aarhus (SDCA). The authors declare no conflicts of interest.

TRIAL REGISTRATION NUMBER

N/A.

The multi-omic landscape of sex chromosome abnormalities: current status and future directions

Sex chromosome abnormalities (SCAs) are chromosomal disorders with either a complete or partial loss or gain of sex chromosomes. The most frequent SCAs include Turner syndrome (45,X), Klinefelter syndrome (47,XXY), Trisomy X syndrome (47,XXX), and Double Y syndrome (47,XYY). The phenotype seen in SCAs is highly variable and may not merely be due to the direct genomic imbalance from altered sex chromosome gene dosage but also due to additive alterations in gene networks and regulatory pathways across the genome as well as individual genetic modifiers. This review summarizes the current insight into the genomics of SCAs. In addition, future directions of research that can contribute to decipher the genomics of SCA are discussed such as single-cell omics, spatial transcriptomics, system biology thinking, human-induced pluripotent stem cells, and animal models, and how these data may be combined to bridge the gap between genomics and the clinical phenotype.

Dosage of the pseudoautosomal gene SLC25A6 is implicated in QTc interval duration

The genetic architecture of the QT interval, defined as the period from onset of depolarisation to completion of repolarisation of the ventricular myocardium, is incompletely understood. Only a minor part of the QT interval variation in the general population has been linked to autosomal variant loci. Altered X chromosome dosage in humans, as seen in sex chromosome aneuploidies such as Turner syndrome (TS) and Klinefelter syndrome (KS), is associated with altered QTc interval (heart rate corrected QT), indicating that genes, located in the pseudoautosomal region 1 of the X and Y chromosomes may contribute to QT interval variation. We investigate the dosage effect of the pseudoautosomal gene SLC25A6, encoding the membrane ADP/ATP translocase 3 in the inner mitochondrial membrane, on QTc interval duration. To this end we used human participants and in vivo zebrafish models. Analyses in humans, based on 44 patients with KS, 44 patients with TS, 59 male and 22 females, revealed a significant negative correlation between SLC25A6 expression level and QTc interval duration. Similarly, downregulation of slc25a6 in zebrafish increased QTc interval duration with pharmacological inhibition of K_ATP channels restoring the systolic duration, whereas overexpression of SLC25A6 shortened QTc, which was normalized by pharmacological activation of K_ATP channels. Our study demonstrate an inverse relationship between SLC25A6 dosage and QTc interval indicating that SLC25A6 contributes to QT interval variation.

Reproductive hormones, bone mineral content, body composition, and testosterone therapy in boys and adolescents with Klinefelter syndrome

Adult patients with Klinefelter syndrome (KS) are characterized by a highly variable phenotype, including tall stature, obesity, and hypergonadotropic hypogonadism, as well as an increased risk of developing insulin resistance, metabolic syndrome, and osteoporosis. Most adults need testosterone replacement therapy (TRT), whereas the use of TRT during puberty has been debated. In this retrospective, observational study, reproductive hormones and whole-body dual-energy x-ray absorptiometry-derived body composition and bone mineral content were standardized to age-related standard deviation scores in 62 patients with KS aged 5.9-20.6 years. Serum concentrations of total testosterone and inhibin B were low, whereas luteinizing hormone and follicle-stimulating hormone were high in patients before TRT. Despite normal body mass index, body fat percentage and the ratio between android fat percentage and gynoid fat percentage were significantly higher in the entire group irrespective of treatment status. In patients evaluated before and during TRT, a tendency toward a more beneficial body composition with a significant reduction in the ratio between android fat percentage and gynoid fat percentage during TRT was found. Bone mineral content (BMC) did not differ from the reference, but BMC corrected for bone area was significantly lower when compared to the reference. This study confirms that patients with KS have an unfavorable body composition and an impaired bone mineral status already during childhood and adolescence. Systematic studies are needed to evaluate whether TRT during puberty will improve these parameters.

Individuals with numerical and structural variations of sex chromosomes: interdisciplinary management with focus on fertility potential

Diagnosis and management of individuals who have differences of sex development (DSD) due to numerical or structural variations of sex chromosomes (NSVSC) remains challenging. Girls who have Turner syndrome (45X) may present with varying phenotypic features, from classical/severe to minor, and some remain undiagnosed. Boys and girls who have 45,X/46,XY chromosomal mosaicism may have Turner syndrome-like features and short stature; therefore, unexplained short stature during childhood requires karyotype analysis in both sexes, particularly if characteristic features or atypical genitalia are present. Many individuals with Klinefelter syndrome (47XXY) remain undiagnosed or are only diagnosed as adults due to fertility problems. Newborn screening by heel prick tests could potentially identify sex chromosome variations but would have ethical and financial implications, and in-depth cost-benefit analyses are needed before nationwide screening can be introduced. Most individuals who have NSVSC have lifelong co-morbidities and healthcare should be holistic, personalized and centralized, with a focus on information, psychosocial support and shared decision-making. Fertility potential should be assessed individually and discussed at an appropriate age. Oocyte or ovarian tissue cryopreservation is possible in some women who have Turner syndrome and live births have been reported following assisted reproductive technology (ART). Testicular sperm cell extraction (TESE) is possible in some men who have 45,X/46,XY mosaicism, but there is no established protocol and no reported fathering of children. Some men with Klinefelter syndrome can now father a child following TESE and ART, with multiple reports of healthy live births. Children who have NSVSC, their parents and DSD team members need to address possibilities and ethical questions relating to potential fertility preservation, with guidelines and international studies still needed.

Integrative epigenome profiling of 47XXY provides insights into whole genomic DNA hypermethylation and active chromatin accessibility

Klinefelter syndrome (KS, 47XXY) is a disorder characterized by sex chromosomal aneuploidy, which may lead to changes in epigenetic regulations of gene expression. To define epigenetic architectures in 47XXY, we annotated DNA methylation in euploid males (46XY) and females (46XX), and 47XXY individuals using whole genome bisulfite sequencing (WGBS) and integrated chromatin accessbilty, and detected abnormal hypermethylation in 47XXY. Furthermore, we detected altered chromatin accessibility in 47XXY, in particular in chromosome X, using Assay for Transposase-Accessible Chromatin sequencing (ATAC-seq) in cultured amniotic cells. Our results construct the whole genome-wide DNA methylation map in 47XXY, and provide new insights into the early epigenomic dysregulation resulting from an extra chromosome X in 47XXY.

Transcriptomic differences between fibrotic and non-fibrotic testicular tissue reveal possible key players in Klinefelter syndrome-related testicular fibrosis

Klinefelter syndrome (KS; 47,XXY) affects 1-2 in 1000 males. Most men with KS suffer from an early germ cell loss and testicular fibrosis from puberty onwards. Mechanisms responsible for these processes remain unknown. Previous genomics studies on testis tissue from men with KS focused on germ cell loss, while a transcriptomic analysis focused on testicular fibrosis has not yet been performed. This study aimed to identify factors involved in the fibrotic remodelling of KS testes by analysing the transcriptome of fibrotic and non-fibrotic testicular tissue. RNA sequencing was performed to compare the genes expressed in testicular samples with (KS and testis atrophy) and without (Sertoli cell-only syndrome and fertile controls) fibrosis (n = 5, each). Additionally, differentially expressed genes (DEGs) between KS and testis atrophy samples were studied to reveal KS-specific fibrotic genes. DEGs were considered significant when p < 0.01 and log2FC > 2. Next, downstream analyses (GO and KEGG) were performed. Lastly, RNA in situ hybridization was performed to validate the results. The first analysis (fibrotic vs non-fibrotic) resulted in 734 significant DEGs (167 up- and 567 down-regulated). Genes involved in the extracellular structure organization (e.g. VCAM1) were found up-regulated. KEGG analysis showed an up-regulation of genes involved in the TGF-β pathway. The KS vs testis atrophy analysis resulted in 539 significant DEGs (59 up- and 480 down-regulated). Chronic inflammatory response genes were found up-regulated. The overlap of X-linked DEGs from the two analyses revealed three genes: matrix-remodelling associated 5 (MXRA5), doublecortin (DCX) and variable charge X-Linked 3B (VCX3B). RNA in situ hybridization showed an overexpression of VCAM1, MXRA5 and DCX within the fibrotic group compared with the non-fibrotic group. To summarize, this study revealed DEGs between fibrotic and non-fibrotic testis tissue, including VCAM1. In addition, X-linked fibrotic genes were revealed, e.g. MXRA5, DCX and VCX3B. Their potential role in KS-related testicular fibrosis needs further study.

Sex chromosome aneuploidies give rise to changes in the circular RNA profile: A circular transcriptome-wide study of Turner and Klinefelter syndrome across different tissues

Purpose: The landscape of circular RNAs (circRNAs), an important class of non-coding RNAs that regulate gene expression, has never been described in human disorders of sex chromosome aneuploidies. We profiled circRNAs in Turner syndrome females (45,X; TS) and Klinefelter syndrome males (47,XXY; KS) to investigate how circRNAs respond to a missing or an extra X chromosome.

Methods: Samples of blood, muscle and fat were collected from individuals with TS (n = 33) and KS (n = 22) and from male (n = 16) and female (n = 44) controls. CircRNAs were identified using a combination of circRNA identification pipelines (CIRI2, CIRCexplorer2 and circRNA_finder).

Results: Differential expression of circRNAs was observed throughout the genome in TS and KS, in all tissues. The host-genes from which several of these circRNAs were derived, were associated with known phenotypic traits. Furthermore, several differentially expressed circRNAs had the potential to capture micro RNAs that targeted protein-coding genes with altered expression in TS and KS.

Conclusion: Sex chromosome aneuploidies introduce changes in the circRNA transcriptome, demonstrating that the genomic changes in these syndromes are more complex than hitherto thought. CircRNAs may help explain some of the genomic and phenotypic traits observed in these syndromes.

KIF2C affects sperm cell differentiation in patients with Klinefelter syndrome, as revealed by RNA-Seq and scRNA-Seq data

Klinefelter syndrome (KS) is a leading contributor to male infertility and is characterised by complex and diverse clinical features; however, genetic changes in the KS transcriptome remain largely unknown. We therefore used transcriptomic and single‐cell RNA sequencing (scRNA‐seq) datasets from KS versus normal populations through the Gene Expression Omnibus (GEO) database to identify gene biomarkers associated with the occurrence of KS. We identified a total of 700 differentially expressed genes (DEGs) and completed Gene Ontology (GO), Kyoto Encyclopedia of Genes and Genomes (KEGG), enrichment pathway analysis and protein‐protein interaction (PPI) network analysis. A total of four unreported KS‐related hub genes (KIF2C, MRPS2, RPS15 and TSFM) were identified. Validation of the single‐cell sequencing dataset showed that only KIF2C and RPS15 were expressed in spermatocytes and that they were differentially expressed in sperm cells. Further construction of the developmental trajectories of these two genes in sperm cells showed that the KIF2C gene showed an upward trend throughout the differentiation and development of sperm cells. In conclusion, we report here that KIF2C may be closely related to the differentiation and development of sperm cells in KS patients, which is important for revealing the molecular mechanism of KS and conducting further studies.

Rapidly Progressing to ESRD in an Individual with Coexisting ADPKD and Masked Klinefelter and Gitelman Syndromes

Autosomal dominant polycystic kidney disease (ADPKD) is the most common monogenetic hereditary renal disease, promoting end-stage renal disease (ESRD). Klinefelter syndrome (KS) is a consequence of an extra copy of the X chromosome in males. Main symptoms in KS include hypogonadism, tall stature, azoospermia, and a risk of cardiovascular diseases, among others. Gitelman syndrome (GS) is an autosomal recessive disorder caused by SLC12A3 variants, and is associated with hypokalemia, hypomagnesemia, hypocalciuria, normal or low blood pressure, and salt loss. The three disorders have distinct and well-delineated clinical, biochemical, and genetic findings. We here report a male patient with ADPKD who developed early chronic renal failure leading to ESRD, presenting with an intracranial aneurysm and infertility. NGS identified two de novo PKD1 variants, one known (likely pathogenic), and a previously unreported variant of uncertain significance, together with two SLC12A3 pathogenic variants. In addition, cytogenetic analysis showed a 47, XXY karyotype. We investigated the putative impact of this rare association by analyzing possible clinical, biochemical, and/or genetic interactions and by comparing the evolution of renal size and function in the proband with three age-matched ADPKD (by variants in PKD1) cohorts. We hypothesize that the coexistence of these three genetic disorders may act as modifiers with possible synergistic actions that could lead, in our patient, to a rapid ADPKD progression.

Pseudoautosomal Region 1 Overdosage Affects the Global Transcriptome in iPSCs From Patients With Klinefelter Syndrome and High-Grade X Chromosome Aneuploidies

Klinefelter syndrome (KS) is the most prevalent aneuploidy in males and is characterized by a 47,XXY karyotype. Less frequently, higher grade sex chromosome aneuploidies (HGAs) can also occur. Here, using a paradigmatic cohort of KS and HGA induced pluripotent stem cells (iPSCs) carrying 49,XXXXY, 48,XXXY, and 47,XXY karyotypes, we identified the genes within the pseudoautosomal region 1 (PAR1) as the most susceptible to dosage-dependent transcriptional dysregulation and therefore potentially responsible for the progressively worsening phenotype in higher grade X aneuploidies. By contrast, the biallelically expressed non-PAR escape genes displayed high interclonal and interpatient variability in iPSCs and differentiated derivatives, suggesting that these genes could be associated with variable KS traits. By interrogating KS and HGA iPSCs at the single-cell resolution we showed that PAR1 and non-PAR escape genes are not only resilient to the X-inactive specific transcript (XIST)-mediated inactivation but also that their transcriptional regulation is disjointed from the absolute XIST expression level. Finally, we explored the transcriptional effects of X chromosome overdosage on autosomes and identified the nuclear respiratory factor 1 (NRF1) as a key regulator of the zinc finger protein X-linked (ZFX). Our study provides the first evidence of an X-dosage-sensitive autosomal transcription factor regulating an X-linked gene in low- and high-grade X aneuploidies.

Update on genetic screening and treatment for infertile men with genetic disorders in the era of assisted reproductive technology

A genetic etiology of male infertility is identified in fewer than 25% of infertile men, while 30% of infertile men lack a clear etiology, resulting in a diagnosis of idiopathic male infertility. Advances in reproductive genetics have provided insights into the mechanisms of male infertility, and a characterization of the genetic basis of male infertility may have broad implications for understanding the causes of infertility and determining the prognosis, optimal treatment, and management of couples. In a substantial proportion of patients with azoospermia, known genetic factors contribute to male infertility. Additionally, the number of identified genetic anomalies in other etiologies of male infertility is growing through advances in whole-genome amplification and next-generation sequencing. In this review, we present an up-to-date overview of the indications for appropriate genetic tests, summarize the characteristics of chromosomal and genetic diseases, and discuss the treatment of couples with genetic infertility by microdissection-testicular sperm extraction, personalized hormone therapy, and in vitro fertilization with pre-implantation genetic testing.

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.

Medulla oblongata germinoma with Klinefelter syndrome

Intracranial germinomas mostly occur in teenagers and young adults. The common sites are pineal and suprasellar regions. Males with Klinefelter syndrome, compared with males without chromosomal abnormalities, are known to have a higher incidence of developing pineal or suprasellar germinomas. As for germinoma in the medulla oblongata, this is rare, with only 21 previous cases reported. Due to the rarities, any relationship between people with Klinefelter syndrome and medulla oblongata germinomas remains undetermined. We present a rare case of medulla oblongata germinoma in a 25-year-old man. It is the second case of medulla oblongata germinoma in association with Klinefelter syndrome. We emphasize the importance of karyotyping in every case of germinoma, especially those with intracranial germinomas at atypical locations.

Chromosome Xq23 is associated with lower atherogenic lipid concentrations and favorable cardiometabolic indices

Autosomal genetic analyses of blood lipids have yielded key insights for coronary heart disease (CHD). However, X chromosome genetic variation is understudied for blood lipids in large sample sizes. We now analyze genetic and blood lipid data in a high-coverage whole X chromosome sequencing study of 65,322 multi-ancestry participants and perform replication among 456,893 European participants. Common alleles on chromosome Xq23 are strongly associated with reduced total cholesterol, LDL cholesterol, and triglycerides (min P = 8.5 × 10-72), with similar effects for males and females. Chromosome Xq23 lipid-lowering alleles are associated with reduced odds for CHD among 42,545 cases and 591,247 controls (P = 1.7 × 10-4), and reduced odds for diabetes mellitus type 2 among 54,095 cases and 573,885 controls (P = 1.4 × 10-5). Although we observe an association with increased BMI, waist-to-hip ratio adjusted for BMI is reduced, bioimpedance analyses indicate increased gluteofemoral fat, and abdominal MRI analyses indicate reduced visceral adiposity. Co-localization analyses strongly correlate increased CHRDL1 gene expression, particularly in adipose tissue, with reduced concentrations of blood lipids.

Erosion of human X chromosome inactivation causes major remodeling of the iPSC proteome

X chromosome inactivation (XCI) is a dosage compensation mechanism in female mammals whereby transcription from one X chromosome is repressed. Analysis of human induced pluripotent stem cells (iPSCs) derived from female donors identified that low levels of XIST RNA correlated strongly with erosion of XCI. Proteomic analysis, RNA sequencing (RNA-seq), and polysome profiling showed that XCI erosion resulted in amplified RNA and protein expression from X-linked genes, providing a proteomic characterization of skewed dosage compensation. Increased protein expression was also detected from autosomal genes without an mRNA increase, thus altering the protein-RNA correlation between the X chromosome and autosomes. XCI-eroded lines display an ∼13% increase in total cell protein content, with increased ribosomal proteins, ribosome biogenesis and translation factors, and polysome levels. We conclude that XCI erosion in iPSCs causes a remodeling of the proteome, affecting the expression of a much wider range of proteins and disease-linked loci than previously realized.

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iPSCs with eroded XCI show defective dosage compensation at the protein level

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iPSCs with eroded XCI display elevated total protein content

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iPSCs with eroded XCI show increased ribosome and polysome levels

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Eroded XCI increases protein but not mRNA expression for 21% of autosomal genes

Genetics of Azoospermia

Azoospermia affects 1% of men, and it can be due to: (i) hypothalamic-pituitary dysfunction, (ii) primary quantitative spermatogenic disturbances, (iii) urogenital duct obstruction. Known genetic factors contribute to all these categories, and genetic testing is part of the routine diagnostic workup of azoospermic men. The diagnostic yield of genetic tests in azoospermia is different in the different etiological categories, with the highest in Congenital Bilateral Absence of Vas Deferens (90%) and the lowest in Non-Obstructive Azoospermia (NOA) due to primary testicular failure (~30%). Whole-Exome Sequencing allowed the discovery of an increasing number of monogenic defects of NOA with a current list of 38 candidate genes. These genes are of potential clinical relevance for future gene panel-based screening. We classified these genes according to the associated-testicular histology underlying the NOA phenotype. The validation and the discovery of novel NOA genes will radically improve patient management. Interestingly, approximately 37% of candidate genes are shared in human male and female gonadal failure, implying that genetic counselling should be extended also to female family members of NOA patients.

Hashimoto's Thyroiditis and Graves' Disease in Genetic Syndromes in Pediatric Age

Autoimmune thyroid diseases (AITDs), including Hashimoto’s thyroiditis (HT) and Graves’ disease (GD), are the most common cause of acquired thyroid disorder during childhood and adolescence. Our purpose was to assess the main features of AITDs when they occur in association with genetic syndromes. We conducted a systematic review of the literature, covering the last 20 years, through MEDLINE via PubMed and EMBASE databases, in order to identify studies focused on the relation between AITDs and genetic syndromes in children and adolescents. From the 1654 references initially identified, 90 articles were selected for our final evaluation. Turner syndrome, Down syndrome, Klinefelter syndrome, neurofibromatosis type 1, Noonan syndrome, 22q11.2 deletion syndrome, Prader–Willi syndrome, Williams syndrome and 18q deletion syndrome were evaluated. Our analysis confirmed that AITDs show peculiar phenotypic patterns when they occur in association with some genetic disorders, especially chromosomopathies. To improve clinical practice and healthcare in children and adolescents with genetic syndromes, an accurate screening and monitoring of thyroid function and autoimmunity should be performed. Furthermore, maintaining adequate thyroid hormone levels is important to avoid aggravating growth and cognitive deficits that are not infrequently present in the syndromes analyzed.

Male Infertility in Humans: An Update on Non-obstructive Azoospermia (NOA) and Obstructive Azoospermia (OA)

Non-obstructive azoospermia (NOA) and obstructive azoospermia (OA) are two common causes of infertility that affect a considerable number of men. However, few studies were performed to understand the molecular etiology of these disorders. Studies based on bioinformatics and genetic analyses in recent years, however, have yielded insightful information and have identified a number of genes that are involved in these disorders. In this review, we briefly summarize and evaluate these findings. We also discuss findings based on epigenetic modifications of sperm DNAs that affect a number of genes pertinent to NOA and OA. The information summarized in this Chapter should be helpful to investigators in future functional studies of NOA and OA.

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.

CHROMOSOMAL DISEASES IN THE HUMAN PATHOLOGY

Background. Chromosomal diseases are the cause of 45-50 % of multiple birth defects. Basic research on mutations is performed using genomic technologies to identify a correlation between genotype and phenotype in aneuploidies and to understand its pathogenesis. Objective. The aim of the research is to study the etiology, pathogenesis of symptoms and diagnostics for patients with Down, Klinefelter, Turner syndromes and double aneuploidies by 21 and sex chromosomes. Methods. A literature review by the keywords “Down syndrome”, “Klinefelter syndrome”, “Turner syndrome”, “double aneuploidy” for the period of 2000-2020 was carried out. Results. Down, Klinefelter and Turner syndromes are the most common aneuploidy among viable newborns. Frequency of meiotic non-disjunction events causing these aneuploidies increases with the age of a woman. Identified genes are responsible for pathogenesis of symptoms in trisomy 21, Turner and Klinefelter syndromes. Diagnostics of chromosomal diseases includes prenatal screening programs and postnatal testing. Conclusions. Cytogenetic variants of Down syndrome are simple complete trisomy 21, translocation form and mosaicism. Trisomy 21 is associated with advanced maternal age. Phenotypic manifestations of Down syndrome are associated with the locus 21q22. The maternal and parental nondisjunction of X-chromosomes in meiosis causes Klinefelter and Turner syndromes. These chromosomal diseases are variants of intersexualism with intermediate chromosomal sex. Down-Klinefelter and Down-Turner syndromes are double aneuploidies. Patients have a Down syndrome phenotype at birth, and signs of Klinefelter and Turner syndromes occur during puberty. Diagnosis of aneuploidy is based on the cytogenetic investigation (karyotyping), DNA analysis, ultrasonography and biochemical markers of chromosomal pathology.

Modeling Klinefelter Syndrome Using Induced Pluripotent Stem Cells Reveals Impaired Germ Cell Differentiation

Klinefelter syndrome (KS), with an incidence between 1/600 and 1/1,000, is the main genetic cause of male infertility. Due to the lack of an accurate study model, the detailed pathogenic mechanisms by which this X chromosome aneuploidy leads to KS features remain unknown. Here, we report the generation and characterization of induced pluripotent stem cells (iPSCs) derived from a patient with KS: 47XXY-iPSCs. In order to compare the potentials of both 47XXY-iPSCs and 46XY-iPSCs to differentiate into the germ cell lineage, we developed a directed differentiation protocol by testing different combinations of factors including bone morphogenetic protein 4 (BMP4), glial-derived neurotrophic factor (GDNF), retinoic acid (RA) and stem cell factor (SCF) for 42 days. Importantly, we found a reduced ability of 47XXY-iPSCs to differentiate into germ cells when compared to 46XY-iPSCs. In particular, upon germ cell differentiation of 47XXY-iPSCs, we found a reduced proportion of cells positive for BOLL, a protein required for germ cell development and spermatogenesis, as well as a reduced proportion of cells positive for MAGEA4, a spermatogonia marker. This reduced ability to generate germ cells was not associated with a decrease of proliferation of 47XXY-iPSC-derived cells but rather with an increase of cell death upon germ cell differentiation as revealed by an increase of LDH release and of capase-3 expression in 47XXY-iPSC-derived cells. Our study supports the idea that 47XXY-iPSCs provides an excellent in vitro model to unravel the pathophysiology and to design potential treatments for KS patients.

European academy of andrology guidelines on Klinefelter Syndrome Endorsing Organization: European Society of Endocrinology

BACKGROUND

Knowledge about Klinefelter syndrome (KS) has increased substantially since its first description almost 80 years ago. A variety of treatment options concerning the spectrum of symptoms associated with KS exists, also regarding aspects beyond testicular dysfunction. Nevertheless, the diagnostic rate is still low in relation to prevalence and no international guidelines are available for KS.

OBJECTIVE

To create the first European Academy of Andrology (EAA) guidelines on KS.

METHODS

An expert group of academicians appointed by the EAA generated a consensus guideline according to the GRADE (Grading of Recommendations, Assessment, Development and Evaluation) system.

RESULTS

Clinical features are highly variable among patients with KS, although common characteristics are severely attenuated spermatogenesis and Leydig cell impairment, resulting in azoospermia and hypergonadotropic hypogonadism. In addition, various manifestations of neurocognitive and psychosocial phenotypes have been described as well as an increased prevalence of adverse cardiovascular, metabolic and bone-related conditions which might explain the increased morbidity/mortality in KS. Moreover, compared to the general male population, a higher prevalence of dental, coagulation and autoimmune disorders is likely to exist in patients with KS. Both genetic and epigenetic effects due to the supernumerary X chromosome as well as testosterone deficiency contribute to this pathological pattern. The majority of patients with KS is diagnosed during adulthood, but symptoms can already become obvious during infancy, childhood or adolescence. The paediatric and juvenile patients with KS require specific attention regarding their development and fertility.

CONCLUSION

These guidelines provide recommendations and suggestions to care for patients with KS in various developmental stages ranging from childhood and adolescence to adulthood. This advice is based on recent research data and respective evaluations as well as validations performed by a group of experts.

Human induced pluripotent stem cells from two azoospermic patients with Klinefelter syndrome show similar X chromosome inactivation behavior to female pluripotent stem cells

STUDY QUESTION

Does the X chromosome inactivation (XCI) of Klinefelter syndrome (KS)-derived human induced pluripotent stem cells (hiPSCs) correspond to female human pluripotent stem cells (hPSCs) and reflect the KS genotype?

SUMMARY ANSWER

Our results demonstrate for the first time that KS-derived hiPSCs show similar XCI behavior to female hPSCs in culture and show biological relevance to KS genotype-related clinical features.

WHAT IS KNOWN ALREADY

So far, assessment of XCI of KS-derived hiPSCs was based on H3K27me3 staining and X-inactive specific transcript gene expression disregarding the at least three XCI states (XaXi with XIST coating, XaXi lacking XIST coating, and XaXe (partially eroded XCI)) that female hPSCs display in culture.

STUDY DESIGN, SIZE, DURATION

The study used hiPSC lines generated from two azoospermic patients with KS and included two healthy male (HM) and one healthy female donor.

PARTICIPANTS/MATERIALS, SETTING, METHODS

In this study, we derived hiPSCs by reprograming fibroblasts with episomal plasmids and applying laminin 521 as culture substrate. hiPSCs were characterized by karyotyping, immunocytochemistry, immunohistochemistry, quantitative PCR, teratoma formation, and embryoid body differentiation. XCI and KS hiPSC relevance were assessed by whole genome transcriptomics analysis and immunocytochemistry plus FISH of KS, HM and female fibroblast, and their hiPSC derivatives.

MAIN RESULTS AND THE ROLE OF CHANCE

Applying whole genome transcriptomics analysis, we could identify differentially expressed genes (DEGs) between KS and HM donors with enrichment in gene ontology terms associated with fertility, cardiovascular development, ossification, and brain development, all associated with KS genotype-related clinical features. Furthermore, XCI analysis based on transcriptomics data, RNA FISH, and H3K27me3 staining revealed variable XCI states of KS hiPSCs similar to female hiPSCs, showing either normal (XaXi) or eroded (XaXe) XCI. KS hiPSCs with normal XCI showed nevertheless upregulated X-linked genes involved in nervous system development as well as synaptic transmission, supporting the potential use of KS-derived hiPSCs as an in vitro model for KS.

LIMITATIONS, REASONS FOR CAUTION

Detailed clinical information for patients included in this study was not available. Although a correlation between DEGs and the KS genotype could be observed, the biological relevance of these cells has to be confirmed with further experiments. In addition, karyotype analysis for two hiPSC lines was performed at passage 12 but not repeated at a later passage. Nevertheless, since all XCI experiments for those lines were performed between passage 11 and 15 the authors expect no karyotypic changes for those experiments.

WIDER IMPLICATIONS OF THE FINDINGS

As KS patients have variable clinical phenotypes that are influenced by the grade of aneuploidy, mosaicism, origin of the X chromosome, and XCI ‘escapee’ genes, which vary not only among individuals but also among different tissues within the same individual, differentiated KS hiPSCs could be used for a better understanding of KS pathogenesis.

STUDY FUNDING/COMPETING INTEREST(S)

This study was supported by grants from the Knut and Alice Wallenberg Foundation (2016.0121 and 2015.0096), Ming Wai Lau Centre for Reparative Medicine (2-343/2016), Ragnar Söderberg Foundation (M67/13), Swedish Research Council (2013-32485-100360-69), the Centre for Innovative Medicine (2–388/2016–40), Kronprinsessan Lovisas Förening För Barnasjukvård/Stiftelsen Axel Tielmans Minnesfond, Samariten Foundation, Jonasson Center at the Royal Institute of Technology, Sweden, and Initial Training Network Marie Curie Program ‘Growsperm’ (EU-FP7-PEOPLE-2013-ITN 603568). The authors declare no conflicts of interest.

Sex chromosome complement affects multiple aspects of reversal-learning task performance in mice

Determining the mechanisms by which the sex-chromosome complement (SCC) affects learning, attention, and impulsivity has implications for observed sex differences in prevalence, severity, and prognosis of psychiatric/neurodevelopmental disorders and syndromes associated with sex-chromosome aneuploidy. Here, Four Core Genotypes (FCG) mice were evaluated in order to assess the separable and/or interacting effects of gonads (testes vs. ovaries) and their secretions and/or SCC (XX vs. XY) acting via non-gonadal mechanisms on behavior. We tested FCG mice on a reversal-learning task that enables the quantification of aspects of learning, attention and impulsivity. Across testing phases (involving the initial acquisition of a spatial discrimination and subsequent reversal learning), overall error rate was larger in XY compared with XX mice. Although XX and XY groups did not differ in the total number of trials required in order to reach a preset performance criterion, analyses of reversal error types showed more perseverative errors in XY than XX mice, with no difference in regressive errors. Additionally, prepotent-response latencies during the reversal phase were shorter in XY males, as compared with both XX gonadal males and females of either SCC, and failures to sustain the observing response were more frequent in XY mice than XX mice during the acquisition phase. These results indicate that SCC affects the characteristic pattern of response selection during acquisition and reversal performance without affecting the overall learning rate. More broadly, these results show direct effects of the SCC on cognitive processes that are relevant to psychiatric/neurodevelopmental disorders and syndromes associated with sex-chromosome aneuploidies.

Epigenetics and genomics in Klinefelter syndrome

Since the first description of Klinefelter syndrome (KS) was published in 1942 in The Journal of Clinical Endocrinology, large inter-individual variability in the phenotypic presentation has been demonstrated. However, our understanding of the global impact of the additional X chromosome on the genome remains an enigma. Evidence from the existing literature of KS indicates that not just one single genetic mechanism can explain the phenotype and the variable expressivity, but several mechanisms may be at play concurrently. In this review, we describe different genetic mechanisms and recent advances in the understanding of the genome, epigenome, and transcriptome of KS and the link to the phenotype and clinical heterogeneity. Future studies are needed to unite clinical data, genomic data, and basic research attempting to understand the genetics behind KS. Unraveling the genetics of KS will be of clinical relevance as it may enable the use of polygenic risk scores to predict future disease susceptibility and enable clinical risk stratification of KS patients in the future.

Integration and reanalysis of transcriptomics and methylomics data derived from blood and testis tissue of men with 47,XXY Klinefelter syndrome indicates the primary involvement of Sertoli cells in the testicular pathogenesis

Klinefelter syndrome (KS; 47,XXY) is the most common sex chromosomal anomaly and causes a multitude of symptoms. Often the most noticeable symptom is infertility caused by azoospermia with testicular histology showing hyalinization of tubules, germ cells loss, and Leydig cell hyperplasia. The germ cell loss begins early in life leading to partial hyalinization of the testis at puberty, but the mechanistic drivers behind this remain poorly understood. In this systematic review, we summarize the current knowledge on developmental changes in the cellularity of KS gonads supplemented by a comparative analysis of the fetal and adult gonadal transcriptome, and blood transcriptome and methylome of men with KS. We identified a high fraction of upregulated genes that escape X-chromosome inactivation, thus supporting previous hypotheses that these are the main drivers of the testicular phenotype in KS. Enrichment analysis showed overrepresentation of genes from the X- and Y-chromosome and testicular transcription factors. Furthermore, by re-evaluation of recent single cell RNA-sequencing data originating from adult KS testis, we found novel evidence that the Sertoli cell is the most affected cell type. Our results are consistent with disturbed cross-talk between somatic and germ cells in the KS testis, and with X-escapee genes acting as mediators.

Genes that escape from X-chromosome inactivation: Potential contributors to Klinefelter syndrome

One of the two X chromosomes in females is epigenetically inactivated, thereby compensating for the dosage difference in X-linked genes between XX females and XY males. Not all X-linked genes are completely inactivated, however, with 12% of genes escaping X chromosome inactivation and another 15% of genes varying in their X chromosome inactivation status across individuals, tissues or cells. Expression of these genes from the second and otherwise inactive X chromosome may underlie sex differences between males and females, and feature in many of the symptoms of XXY Klinefelter males, who have both an inactive X and a Y chromosome. We review the approaches used to identify genes that escape from X-chromosome inactivation and discuss the nature of their sex-biased expression. These genes are enriched on the short arm of the X chromosome, and, in addition to genes in the pseudoautosomal regions, include genes with and without Y-chromosomal counterparts. We highlight candidate escape genes for some of the features of Klinefelter syndrome and discuss our current understanding of the mechanisms underlying silencing and escape on the X chromosome as well as additional differences between the X in males and females that may contribute to Klinefelter syndrome.

Germ cell loss in Klinefelter syndrome: When and why?

Klinefelter syndrome (KS) is a quite common disorder with an incidence of 1-2 in 1,000 new-born males. Most patients are diagnosed in the light of a clinical checkup when consulting a fertility clinic with an unfulfilled child wish. Infertility in KS patients is caused by a massive germ cell loss, leading to azoospermia in more than 90% of the adult patients. Most seminiferous tubules in the adult KS testis are degenerated or hyalinized and testicular fibrosis can be observed, starting from puberty. However, focal spermatogenesis can be found in the testis of some patients. This offers the opportunity to extract spermatozoa from the testis by testicular sperm extraction (TESE). Nevertheless, TESE is only successful in about half of the KS adults seeking to father children. The reason for the germ cell loss remains unclear. To date, it is still debated whether the testicular tissue changes and the germ cell loss seen in KS is directly caused by an altered X-linked gene expression, the altered somatic environment, or a deficiency in the germ cells. In this review, we provide an overview of the current knowledge about the germ cell loss in KS patients.

Molecular Aging Markers in Patients with Klinefelter Syndrome

Molecular aging markers provide the opportunity for biological age determination in humans and to study factors, such as genetic determinants, affecting the ageing process. In males with Klinefelter syndrome (KS, non-mosaic karyotype 47, XXY), which is the most common sex chromosome aneuploidy, age-related morbidity and mortality are increased, and a significantly reduced life span has been observed. The aim of this study was to investigate whether Klinefelter patients exhibit molecular signs of premature ageing. We studied, specifically, age-associated DNA methylation patterns (by pyrosequencing) and relative telomere length (TL; by quantitative polymerase chain reaction) in blood in a cohort of Klinefelter patients (n=178 and 266 for DNA methylation and TL, respectively) aged 18-71 years and compared them to the data of age-matched healthy male (n = 184 and 196 for DNA methylation and TL, respectively) and female controls (n = 50). Age-associated DNA methylation patterns were not indicative of accelerated ageing in Klinefelter men. Significantly longer telomeres were found in the young Klinefelter subjects aged 18-24 years (mean=1.51 vs. 1.09 and 1.26 in female and male controls, respectively). However, telomere length in subsequent age groups showed no difference to controls. Gonosomal aneuploidy in Klinefelter syndrome is associated with higher baseline TL at adolescent age, but comparable TL with progressive age in other age groups.

Autoimmune Thyroid Disease in Specific Genetic Syndromes in Childhood and Adolescence

Autoimmune thyroid disease (ATD) is the most frequent cause of acquired thyroid dysfunction, most commonly presenting either as Hashimoto's thyroiditis or Graves' Disease. Hashimoto's thyroiditis is characterized by the presence of thyroid-specific autoantibodies, more commonly anti-thyroperoxidase antibodies in the serum and the typical inhomogeneous echostructure of the thyroid on a thyroid ultrasound examination. Hashimoto's thyroiditis can for a long time be accompanied by normal thyroid function and hypothyroidism can only progressively be established. Graves' disease is much less frequent in childhood and adolescence and presents with overt hyperthyroidism. After the onset of puberty, ATD affects females with a higher incidence than males, while during the prepubertal period there is not such a clear preponderance of affected females. ATD can occur either isolated or in the context of other autoimmune disorders, such as type 1 Diabetes mellitus (T1D), celiac disease, alopecia areata, vitiligo, etc. Especially at the pediatric age, a higher incidence of ATD is also observed in the context of specific genetic syndromes, such as trisomy 21 (Down syndrome), Klinefelter syndrome, Turner syndrome, or 22q11.2 deletion syndrome. Nevertheless, although thyroid dysfunction may also be observed in other genetic syndromes, such as Prader-Willi or Williams syndrome, the thyroid dysfunction in these syndromes is not the result of thyroid autoimmunity. Interestingly, there is emerging evidence supporting a possible link between autoimmunity and RASopathies. In this review article the incidence, as well as the clinical manifestation and accompanied pathologies of ATD in specific genetic syndromes will be presented and regular follow-up for the early identification of the disorder will be proposed.

Single-Cell Sequencing Reveals the Relationship between Phenotypes and Genotypes of Klinefelter Syndrome

Klinefelter syndrome (KS) is one of the most common congenital disorders of male infertility. Given its high heterogeneity in clinical and genetic presentation, the relationship between transcriptome, clinical phenotype, and associated co-morbidities seen in KS has not been fully clarified. Here, we report a 47,XXY Chinese male with infertility and analyzed the differences in gene expression patterns of peripheral blood mononuclear cells (PBMCs) with regard to a Chinese male and a female control with normal karyotype by single-cell sequencing. A total of 24,439 cells were analyzed and divided into 5 immune cell types (including B cells, T cells, macrophage cells, dendritic cells, and natural killer cells) according to marker genes. Using unsupervised dimensionality reduction and clustering algorithms, we identified molecularly distinct subpopulations of cells between the KS patient and both controls. Gene ontology enrichment analyses yielded terms associated with well-known comorbidities seen in KS as well as an affected immune system and type I diabetes mellitus. Based on our data, we identified several candidate genes which may be implicated in regulating the phenotype of KS. Overall, this analysis provides a comprehensive map of the cell types of PBMCs in a KS patient at the single-cell level, which will contribute to the prevention of comorbidity and improvement of the life quality of KS patients.

Thyroid function in Klinefelter syndrome: a multicentre study from KING group

PURPOSE

The prevalence and the etiopathogenesis of thyroid dysfunctions in Klinefelter syndrome (KS) are still unclear. The primary aim of this study was to evaluate the pathogenetic role of hypogonadism in the thyroid disorders described in KS, with the scope to distinguish between patients with KS and hypogonadism due to other causes (Kallmann syndrome, idiopathic hypogonadotropic hypogonadism, iatrogenic hypogonadism and acquired hypogonadotropic hypogonadism after surgical removal of pituitary adenomas) called non-KS. Therefore, we evaluated thyroid function in KS and in non-KS hypogonadal patients.

METHODS

This is a case-control multicentre study from KING group: Endocrinology clinics in university-affiliated medical centres. One hundred and seventy four KS, and sixty-two non-KS hypogonadal men were enrolled. The primary outcome was the prevalence of thyroid diseases in KS and in non-KS. Changes in hormonal parameters were evaluated. Exclusion criterion was secondary hypothyroidism. Analyses were performed using Student's t test. Mann-Whitney test and Chi-square test.

RESULTS

FT4 was significantly lower in KS vs non-KS. KS and non-KS presented similar TSH and testosterone levels. Hashimoto's thyroiditis (HT) was diagnosed in 7% of KS. Five KS developed hypothyroidism. The ratio FT3/FT4 was similar in both groups. TSH index was 1.9 in KS and 2.3 in non-KS. Adjustment for differences in age, sample size and concomitant disease in multivariate models did not alter the results.

CONCLUSIONS

We demonstrated in KS no etiopathogenic link to hypogonadism or change in the set point of thyrotrophic control in the altered FT4 production. The prevalence of HT in KS was similar to normal male population, showing absence of increased risk of HT associated with the XXY karyotype.

Genetics of male infertility

Male infertility is a multifactorial pathological condition affecting approximately 7% of the male population. The genetic landscape of male infertility is highly complex as semen and testis histological phenotypes are extremely heterogeneous, and at least 2,000 genes are involved in spermatogenesis. The highest frequency of known genetic factors contributing to male infertility (25%) is in azoospermia, but the number of identified genetic anomalies in other semen and aetiological categories is constantly growing. Genetic screening is relevant for its diagnostic value, clinical decision making, and appropriate genetic counselling. Anomalies in sex chromosomes have major roles in severe spermatogenic impairment. Autosome-linked gene mutations are mainly involved in central hypogonadism, monomorphic teratozoospermia or asthenozoospermia, congenital obstructive azoospermia, and familial cases of quantitative spermatogenic disturbances. Results from whole-genome association studies suggest a marginal role for common variants as causative factors; however, some of these variants can be important for pharmacogenetic purposes. Results of studies on copy number variations (CNVs) demonstrate a considerably higher CNV load in infertile patients than in normozoospermic men, whereas whole-exome analysis has proved to be a highly successful diagnostic tool in familial cases of male infertility. Despite such efforts, the aetiology of infertility remains unknown in about 40% of patients, and the discovery of novel genetic factors in idiopathic infertility is a major challenge for the field of androgenetics. Large, international, and consortium-based whole-exome and whole-genome studies are the most promising approach for the discovery of the missing genetic aetiology of idiopathic male infertility.

Reversal Learning Performance in the XY∗ Mouse Model of Klinefelter and Turner Syndromes

Klinefelter syndrome (KS; 47, XXY) and Turner syndrome (TS; 45, XO) are caused by two relatively common sex chromosome aneuploidies. These conditions are associated with an increased odds of neuropsychiatric disorders, including attention deficit/hyperactivity disorder (ADHD), as well as impairments in cognition that include learning delays, attentional dysfunction and impulsivity. We studied cognitive functions in the XY^∗ mouse model, which allows comparison of XXY to XY males (KS model), and XO to XX females (TS model). We evaluated adult mice with and without gonads, using a version of an operant reversal-learning task (RLT) that can be used to measure various facets of learning, impulsivity and attention. In the KS model, only one measure related to impulsivity – perseverative responding under reversal conditions – reliably discriminated gonadally intact XXY and XY mice. In contrast, a fundamental learning impairment (more trials to criterion in acquisition phase) in XXY mice, as compared to XY, was observed in gonadectomized subjects. No other task measures showed differences consistent with KS. In the TS mouse model, XO mice did not show a pattern of results consistent with TS, similar to past observations. Thus, the application of this RLT to these XY^∗ models reveals only limited behavioral impairments relevant to KS.

Distinct signatures of lung cancer types: aberrant mucin O-glycosylation and compromised immune response

BACKGROUND

Genomic initiatives such as The Cancer Genome Atlas (TCGA) contain data from -omics profiling of thousands of tumor samples, which may be used to decipher cancer signaling, and related alterations. Managing and analyzing data from large-scale projects, such as TCGA, is a demanding task. It is difficult to dissect the high complexity hidden in genomic data and to account for inter-tumor heterogeneity adequately.

METHODS

In this study, we used a robust statistical framework along with the integration of diverse bioinformatic tools to analyze next-generation sequencing data from more than 1000 patients from two different lung cancer subtypes, i.e., the lung adenocarcinoma (LUAD) and the squamous cell carcinoma (LUSC).

RESULTS

We used the gene expression data to identify co-expression modules and differentially expressed genes to discriminate between LUAD and LUSC. We identified a group of genes which could act as specific oncogenes or tumor suppressor genes in one of the two lung cancer types, along with two dual role genes. Our results have been validated against other transcriptomics data of lung cancer patients.

CONCLUSIONS

Our integrative approach allowed us to identify two key features: a substantial up-regulation of genes involved in O-glycosylation of mucins in LUAD, and a compromised immune response in LUSC. The immune-profile associated with LUSC might be linked to the activation of three oncogenic pathways, which promote the evasion of the antitumor immune response. Collectively, our results provide new future directions for the design of target therapies in lung cancer.

Treatment of Hidradenitis Suppurativa Patient with Klinefelter Syndrome by Adalimumab

Hidradenitis suppurativa (HS) is a chronic, inflammatory and painful skin disease with recurrent nodules and tracts involving the intertriginous regions. It is known that the patient with HS shows an increased risk of metabolic disorders such as diabetes, metabolic syndrome and autoimmune diseases. Klinefelter syndrome (KS) is a sex chromosomal disorder occurring in males due to an abnormality of sexual differentiation, characterized by 47, XXY karyotype. Also, KS is related with somatic comorbidities such as metabolic syndrome, autoimmune and rheumatologic disorders as HS is. We report a HS patient with KS who shows a big improvement while on tumor necrosis factor-alpha inhibitor treatment.

Klinefelter Syndrome and Diabetes

PURPOSE OF REVIEW

Klinefelter syndrome (KS) is associated with increased insulin resistance and high rates of type 2 diabetes (T2DM). Our aim was to review what is known about the prevalence of diabetes in men with KS, potential mechanisms underlying the observed metabolic phenotype, and the data that are available to guide treatment decisions.

RECENT FINDINGS

The increased prevalence of T2DM seen in men with KS appears to be the result of multiple mechanisms including increased truncal adiposity and socioeconomic disadvantages, but it is likely not a direct consequence of hypogonadism alone. No randomized trials have been conducted to evaluate the impact of testosterone replacement therapy on T2DM in men with KS, but observational data suggest that testosterone replacement is not associated with lower rates of diabetes or improved glycemic control. Metabolic derangements are common in KS, but treatment strategies specific to this population are lacking. Early lifestyle and dietary interventions are likely important. Additional research is needed to dissect the complex interaction between genotype and metabolic phenotype. Collaboration between academic centers caring for men with KS is needed to facilitate the development of evidence-based clinical practice guidelines, which would inform optimal screening and treatment strategies for this patient population.

Paediatric and adult-onset male hypogonadism

The hypothalamic-pituitary-gonadal axis is of relevance in many processes related to the development, maturation and ageing of the male. Through this axis, a cascade of coordinated activities is carried out leading to sustained testicular endocrine function, with gonadal testosterone production, as well as exocrine function, with spermatogenesis. Conditions impairing the hypothalamic-pituitary-gonadal axis during paediatric or pubertal life may result in delayed puberty. Late-onset hypogonadism is a clinical condition in the ageing male combining low concentrations of circulating testosterone and specific symptoms associated with impaired hormone production. Testosterone therapy for congenital forms of hypogonadism must be lifelong, whereas testosterone treatment of late-onset hypogonadism remains a matter of debate because of unclear indications for replacement, uncertain efficacy and potential risks. This Primer focuses on a reappraisal of the physiological role of testosterone, with emphasis on the critical interpretation of the hypogonadal conditions throughout the lifespan of the male individual, with the exception of hypogonadal states resulting from congenital disorders of sex development.

Comorbidity landscape of the Danish patient population affected by chromosome abnormalities

PURPOSE

Most chromosome abnormality patients require long-term clinical care. Awareness of mosaicism and comorbidities can potentially guide such health care. Here we present a population-wide analysis of direct and inverse comorbidities affecting patients with chromosome abnormalities.

METHODS

We extracted direct and inverse comorbidities for the 11 most prevalent chromosome abnormalities from the Danish National Patient Registry (covering 6.9 million patients hospitalized between 1994 and 2015): trisomy 13, 18, and 21, Klinefelter (47,XXY), triple X, XYY, Turner (45,X), Wolf-Hirschhorn, Cri-du-chat, Angelman, and Fragile X syndromes (FXS). We also performed four sub-analyses for male/female Down syndrome (DS) and FXS and non-mosaic/mosaic DS and Turner syndrome.

RESULTS

Our data cover 9,003 patients diagnosed with at least one chromosome abnormality. Each abnormality showed a unique comorbidity signature, but clustering of their profiles underlined common risk profiles for chromosome abnormalities with similar genetic backgrounds. We found that DS had a decreased risk for three inverse cancer comorbidities (lung, breast, and skin) and that male FXS and non-mosaic patients have a much more severe phenotype than female FXS and mosaic patients, respectively.

CONCLUSION

Our study underlines the importance of considering mosaicism, sex, and the associated comorbidity profiles of chromosome abnormalities to guide long-term health care of affected patients.

Human genes escaping X-inactivation revealed by single cell expression data

BACKGROUND

In mammals, sex chromosomes pose an inherent imbalance of gene expression between sexes. In each female somatic cell, random inactivation of one of the X-chromosomes restores this balance. While most genes from the inactivated X-chromosome are silenced, 15-25% are known to escape X-inactivation (termed escapees). The expression levels of these genes are attributed to sex-dependent phenotypic variability.

RESULTS

We used single-cell RNA-Seq to detect escapees in somatic cells. As only one X-chromosome is inactivated in each cell, the origin of expression from the active or inactive chromosome can be determined from the variation of sequenced RNAs. We analyzed primary, healthy fibroblasts (n = 104), and clonal lymphoblasts with sequenced parental genomes (n = 25) by measuring the degree of allelic-specific expression (ASE) from heterozygous sites. We identified 24 and 49 candidate escapees, at varying degree of confidence, from the fibroblast and lymphoblast transcriptomes, respectively. We critically test the validity of escapee annotations by comparing our findings with a large collection of independent studies. We find that most genes (66%) from the unified set were previously reported as escapees. Furthermore, out of the overlooked escapees, 11 are long noncoding RNA (lncRNAs).

CONCLUSIONS

X-chromosome inactivation and escaping from it are robust, permanent phenomena that are best studies at a single-cell resolution. The cumulative information from individual cells increases the potential of identifying escapees. Moreover, despite the use of a limited number of cells, clonal cells (i.e., same X- chromosomes are coordinately inhibited) with genomic phasing are valuable for detecting escapees at high confidence. Generalizing the method to uncharacterized genomic loci resulted in lncRNAs escapees which account for 20% of the listed candidates. By confirming genes as escapees and propose others as candidates from two different cell types, we contribute to the cumulative knowledge and reliability of human escapees.

Recent advances in managing and understanding Klinefelter syndrome

Klinefelter syndrome can present as a wide spectrum of clinical manifestations at various stages in life, making it a chromosomal disorder with no standardized set of guidelines for appropriate management. Understanding the genetic and hormonal causes of this syndrome can allow physicians to treat each patient on a more individualized basis. The timing of diagnosis and degree of symptoms can guide management. This report will provide an updated review of the clinical presentation at various stages in life and the implications for management.

Transcriptome profiling of fetal Klinefelter testis tissue reveals a possible involvement of long non-coding RNAs in gonocyte maturation

In humans, the most common sex chromosomal disorder is Klinefelter syndrome (KS), caused by the presence of one or more extra X-chromosomes. KS patients display a varying adult phenotype but usually present with azoospermia due to testicular degeneration, which accelerates at puberty. The timing of the germ cell loss and whether it is caused by dysgenetic fetal development of the testes is not known. We investigated eight fetal KS testes and found a marked reduction in MAGE-A4-positive pre-spermatogonia compared with testes from 15 age-matched controls, indicating a failure of the gonocytes to differentiate into pre-spermatogonia. Transcriptome analysis by RNA-sequencing of formalin-fixed, paraffin-embedded testes originating from four fetal KS and five age-matched controls revealed 211 differentially expressed transcripts in the fetal KS testis. We found a significant enrichment of upregulated X-chromosomal transcripts and validated the expression of the pseudoautosomal region 1 (PAR1) gene, AKAP17A. Moreover, we found enrichment of long non-coding RNAs in the KS testes (e.g. LINC01569 and RP11-485F13.1). In conclusion, our data indicate that the testicular phenotype observed among adult men with KS is initiated already in fetal life by failure of the gonocyte differentiation into pre-spermatogonia, which could be due to aberrant expression of long non-coding RNAs.

Effects of human sex chromosome dosage on spatial chromosome organization

Sex chromosome aneuploidies (SCAs) are common genetic syndromes characterized by the presence of an aberrant number of X and Y chromosomes due to meiotic defects. These conditions impact the structure and function of diverse tissues, but the proximal effects of SCAs on genome organization are unknown. Here, to determine the consequences of SCAs on global genome organization, we have analyzed multiple architectural features of chromosome organization in a comprehensive set of primary cells from SCA patients with various ratios of X and Y chromosomes by use of imaging-based high-throughput chromosome territory mapping (HiCTMap). We find that X chromosome supernumeracy does not affect the size, volume, or nuclear position of the Y chromosome or an autosomal chromosome. In contrast, the active X chromosome undergoes architectural changes as a function of increasing X copy number as measured by a decrease in size and an increase in circularity, which is indicative of chromatin compaction. In Y chromosome supernumeracy, Y chromosome size is reduced suggesting higher chromatin condensation. The radial positioning of chromosomes is unaffected in SCA karyotypes. Taken together, these observations document changes in genome architecture in response to alterations in sex chromosome numbers and point to trans-effects of dosage compensation on chromosome organization.

DNA hypermethylation and differential gene expression associated with Klinefelter syndrome

Klinefelter syndrome (KS) has a prevalence ranging from 85 to 250 per 100.000 newborn boys making it the most frequent sex chromosome aneuploidy in the general population. The molecular basis for the phenotypic traits and morbidity in KS are not clarified. We performed genome-wide DNA methylation profiling of leucocytes from peripheral blood samples from 67 KS patients, 67 male controls and 33 female controls, in addition to genome-wide RNA-sequencing profiling in a subset of 9 KS patients, 9 control males and 13 female controls. Characterization of the methylome as well as the transcriptome of both coding and non-coding genes identified a unique epigenetic and genetic landscape of both autosomal chromosomes as well as the X chromosome in KS. A subset of genes show significant correlation between methylation values and expression values. Gene set enrichment analysis of differentially methylated positions yielded terms associated with well-known comorbidities seen in KS. In addition, differentially expressed genes revealed enrichment for genes involved in the immune system, wnt-signaling pathway and neuron development. Based on our data we point towards new candidate genes, which may be implicated in the phenotype and further point towards non-coding genes, which may be involved in X chromosome inactivation in KS.

Klinefelter syndrome: more than hypogonadism

Klinefelter syndrome (KS) is the most frequent chromosome disorder in males (1:650 newborn males), defined by 47,XXY karyotype. The classical phenotype is that of a tall male with relatively long legs, small, firm testes and gynecomastia. Azoospermia and infertility are almost inevitably present, but may be overcome by TESE and ICSI. Nevertheless, a broad spectrum of phenotypes has been described and more than 70% of the actually existing KS men may remain undiagnosed throughout their lifespan. Accordingly, hypogonadism is usually not evident until early adulthood and progresses with ageing. KS patients present a series of comorbidities that increase morbidity and mortality by 40%. Such disturbances are the impaired metabolic profile (obesity, dyslipidemia, insulin resistance) and a tendency to thrombosis, which all favor cardiovascular disease. They also present susceptibility for specific neoplasias (breast cancer, extragonadal germ cell tumors), autoimmune diseases as well as osteoporosis and bone fractures. Moreover, KS has been associated with verbal processing and attention deficits as well as social skill impairments, leading KS individuals to academic and professional achievements inferior to those of their peers of comparable socio-economic status. Nevertheless, the majority fall within the average range regarding their intellectual abilities and adaptive functioning. Testosterone replacement therapy (TRT) is the mainstay of treatment in hypogonadal KS patients; however, randomized trials are needed to determine optimal therapeutic regimens and follow-up schedules.

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-chromosome dosage effects on gene expression in humans

A fundamental question in the biology of sex differences has eluded direct study in humans: How does sex-chromosome dosage (SCD) shape genome function? To address this, we developed a systematic map of SCD effects on gene function by analyzing genome-wide expression data in humans with diverse sex-chromosome aneuploidies (XO, XXX, XXY, XYY, and XXYY). For sex chromosomes, we demonstrate a pattern of obligate dosage sensitivity among evolutionarily preserved X-Y homologs and update prevailing theoretical models for SCD compensation by detecting X-linked genes that increase expression with decreasing X- and/or Y-chromosome dosage. We further show that SCD-sensitive sex-chromosome genes regulate specific coexpression networks of SCD-sensitive autosomal genes with critical cellular functions and a demonstrable potential to mediate previously documented SCD effects on disease. These gene coexpression results converge with analysis of transcription factor binding site enrichment and measures of gene expression in murine knockout models to spotlight the dosage-sensitive X-linked transcription factor ZFX as a key mediator of SCD effects on wider genome expression. Our findings characterize the effects of SCD broadly across the genome, with potential implications for human phenotypic variation.

Transcriptome analysis of the adult human Klinefelter testis and cellularity-matched controls reveals disturbed differentiation of Sertoli- and Leydig cells

The most common human sex chromosomal disorder is Klinefelter syndrome (KS; 47,XXY). Adult patients with KS display a diverse phenotype but are nearly always infertile, due to testicular degeneration at puberty. To identify mechanisms causing the selective destruction of the seminiferous epithelium, we performed RNA-sequencing of 24 fixed paraffin-embedded testicular tissue samples. Analysis of informative transcriptomes revealed 235 differentially expressed transcripts (DETs) in the adult KS testis showing enrichment of long non-coding RNAs, but surprisingly not of X-chromosomal transcripts. Comparison to 46,XY samples with complete spermatogenesis and Sertoli cell-only-syndrome allowed prediction of the cellular origin of 71 of the DETs. DACH2 and FAM9A were validated by immunohistochemistry and found to mark apparently undifferentiated somatic cell populations in the KS testes. Moreover, transcriptomes from fetal, pre-pubertal, and adult KS testes showed a limited overlap, indicating that different mechanisms are likely to operate at each developmental stage. Based on our data, we propose that testicular degeneration in men with KS is a consequence of germ cells loss initiated during early development in combination with disturbed maturation of Sertoli- and Leydig cells.