A cytogenetic and molecular study of a series of 45,X fetuses and their parents

Sex at the interface: the origin and impact of sex differences in the developing human placenta

The fetal placenta is a source of hormones and immune factors that play a vital role in maintaining pregnancy and facilitating fetal growth. Cells in this extraembryonic compartment match the chromosomal sex of the embryo itself. Sex differences have been observed in common gestational pathologies, highlighting the importance of maternal immune tolerance to the fetal compartment. Over the past decade, several studies examining placentas from term pregnancies have revealed widespread sex differences in hormone signaling, immune signaling, and metabolic functions. Given the rapid and dynamic development of the human placenta, sex differences that exist at term (37–42 weeks gestation) are unlikely to align precisely with those present at earlier stages when the fetal–maternal interface is being formed and the foundations of a healthy or diseased pregnancy are established. While fetal sex as a variable is often left unreported in studies performing transcriptomic profiling of the first-trimester human placenta, four recent studies have specifically examined fetal sex in early human placental development. In this review, we discuss the findings from these publications and consider the evidence for the genetic, hormonal, and immune mechanisms that are theorized to account for sex differences in early human placenta. We also highlight the cellular and molecular processes that are most likely to be impacted by fetal sex and the evolutionary pressures that may have given rise to these differences. With growing recognition of the fetal origins of health and disease, it is important to shed light on sex differences in early prenatal development, as these observations may unlock insight into the foundations of sex-biased pathologies that emerge later in life.

Placental sex differences exist from early prenatal development, and may help explain sex differences in pregnancy outcomes.

Transcriptome profiling of early to mid-gestation placenta reveals that immune signaling is a hub of early prenatal sex differences.

Differentially expressed genes between male and female placenta fall into the following functional associations: chromatin modification, transcription, splicing, translation, signal transduction, metabolic regulation, cell death and autophagy regulation, ubiquitination, cell adhesion and cell–cell interaction.

Placental sex differences likely reflect the interaction of cell-intrinsic chromosome complement with extrinsic endocrine signals from the fetal compartment that accompany gonadal differentiation.

Understanding the mechanisms behind sex differences in placental development and function will provide key insight into molecular targets that can be modulated to improve sex-biased obstetrical complications.

A Review of Recent Developments in Turner Syndrome Research

Turner syndrome is a rare disorder resulting from complete or partial loss of the second sex chromosome. Common manifestations include delayed growth, premature ovarian failure, congenital heart defects, endocrine disorders, lymphedema, and webbed neck. People with Turner syndrome have significantly increased mortality risk primarily due to cardiovascular abnormalities. The mechanisms that lead to these defects are not completely understood and are obscured by the significant variability of both karyotype and phenotype without consistent correlation between the two. This paper presents a review of the recent literature surrounding the symptoms, mechanisms, diagnosis, and treatment of Turner syndrome with a focus on cardiovascular manifestations. With technological advancements in genetics, the molecular processes of Turner syndrome have begun to be dissected. Certain genes on the X chromosome that typically escape inactivation have been implicated in both specific manifestations and broader risk categories. Recently identified genome-wide epigenetic changes may help explain the variability in presentation. It remains unclear as to how the combination of these factors results in the overall clinical picture, but advances in genomic, genetic, epigenetic, and -omics technology hold promise for providing insights that will improve the medical management of individuals with Turner syndrome.

Functional and regulatory aspects of oxidative stress response in X monosomy

The partial/complete loss of one X chromosome in a human female leads to Turner syndrome (TS). TS individuals display a range of phenotypes including short stature, osteoporosis, ovarian malfunction, diabetes, and thyroid dysfunction. Epigenetic factors and regulatory networks are distinctly different in X monosomy (45, X). In a lifetime, an individual is exposed to a variety of stress conditions. To study whether X monosomy cells display a differential response upon exposure to mild stress as compared to normal 46, XX cells and whether this may contribute to various co-morbidities in aneuploid individuals, we have carried out a transcriptomic analysis of human fibroblasts 45, X and 46, XX after exposure to mild oxidative stress. Under these conditions, over 350 transcripts were seen to be differentially expressed in 45, X and 46, XX cells. Pathways associated with oxidative stress were differentially expressed highlighting the differential regulation of genes and associated phenotypes. It could be seen that X monosomy cells are more susceptible to oxidative stress as compared to normal cells and have altered molecular pathways both in normal conditions and also upon exposure to mild oxidative stress. To explore this aspect in detail, we have mapped the expressions of transcription factors (TFs) in 45, X and 46, XX cells. The network of transcription activating factors is differentially regulated in 45, X and 46, XX cells under stress exposure. It is tempting to speculate that the altered ability of 45, X (Turner) cells to respond to stress may play a significant role in the physiological function and altered phenotypes in Turner syndrome.

Hemodynamic Abnormalities in the Aorta of Turner Syndrome Girls

Congenital abnormalities in girls and women with Turner syndrome (TS), alongside an underlying predisposition to obesity and hypertension, contribute to an increased risk of cardiovascular disease and ultimately reduced life expectancy. We observe that children with TS present a greater variance in aortic arch morphology than their healthy counterparts, and hypothesize that their hemodynamics is also different. In this study, computational fluid dynamic (CFD) simulations were performed for four TS girls, and three age-matched healthy girls, using patient-specific inlet boundary conditions, obtained from phase-contrast MRI data. The visualization of multidirectional blood flow revealed an increase in vortical flow in the arch, supra-aortic vessels, and descending aorta, and a correlation between the presence of aortic abnormalities and disturbed flow. Compared to the relatively homogeneous pattern of time-averaged wall shear stress (TAWSS) on the healthy aortae, a highly heterogeneous distribution with elevated TAWSS values was observed in the TS geometries. Visualization of further shear stress parameters, such as oscillatory shear index (OSI), normalized relative residence time (RRTn), and transverse WSS (transWSS), revealed dissimilar heterogeneity in the oscillatory and multidirectional nature of the aortic flow. Taking into account the young age of our TS cohort (average age 13 ± 2 years) and their obesity level (75% were obese or overweight), which is believed to accelerate the initiation and progression of endothelial dysfunction, these findings may be an indication of atherosclerotic disease manifesting earlier in life in TS patients. Age, obesity and aortic morphology may, therefore, play a key role in assessing cardiovascular risk in TS children.

The nuclear functions of long noncoding RNAs come into focus

Long noncoding RNAs (lncRNAs), defined as untranslated and tightly-regulated transcripts with a length exceeding 200 nt, are common outputs of the eukaryotic genome. It is becoming increasingly apparent that many lncRNAs likely serve as important regulators in a variety of biological processes. In particular, some of them accumulate in the nucleus and function in diverse nuclear events, including chromatin remodeling, transcriptional regulation, RNA processing, DNA damage repair, etc. Here, we unite recent progresses on the functions of nuclear lncRNAs and provide insights into the future research directions of this field.

Dosage-sensitive functions in embryonic development drove the survival of genes on sex-specific chromosomes in snakes, birds, and mammals

Different ancestral autosomes independently evolved into sex chromosomes in snakes, birds, and mammals. In snakes and birds, females are ZW and males are ZZ; in mammals, females are XX and males are XY. Although X and Z Chromosomes retain nearly all ancestral genes, sex-specific W and Y Chromosomes suffered extensive genetic decay. In both birds and mammals, the genes that survived on sex-specific chromosomes are enriched for broadly expressed, dosage-sensitive regulators of gene expression, subject to strong purifying selection. To gain deeper insight into the processes that govern survival on sex-specific chromosomes, we carried out a meta-analysis of survival across 41 species-three snakes, 24 birds, and 14 mammals-doubling the number of ancestral genes under investigation and increasing our power to detect enrichments among survivors relative to nonsurvivors. Of 2564 ancestral genes, representing an eighth of the ancestral amniote genome, only 324 survive on present-day sex-specific chromosomes. Survivors are enriched for dosage-sensitive developmental processes, particularly development of neural crest-derived structures, such as the face. However, there was no enrichment for expression in sex-specific tissues, involvement in sex determination or gonadogenesis pathways, or conserved sex-biased expression. Broad expression and dosage sensitivity contributed independently to gene survival, suggesting that pleiotropy imposes additional constraints on the evolution of dosage compensation. We propose that maintaining the viability of the heterogametic sex drove gene survival on amniote sex-specific chromosomes, and that subtle modulation of the expression of survivor genes and their autosomal orthologs has disproportionately large effects on development and disease.

Pubertal induction in girls with Turner Syndrome

Turner Syndrome (TS) is the most common female sex chromosome aneuploidy in females, and patients may present with hypergonadotropic hypogonadism due to gonadal dysgenesis. Timing and modalities of pubertal induction in these patients is still a matter of debate. Aim of this review was to focus on the latest update on pubertal induction in TS. Based on literature data, the following practical approach to this issue is recommended. Pubertal induction should begin between 11 and 12 years of age, starting with low doses of estradiol to preserve height potential. Transdermal 17β-Estradiol (17β-E2) could represent the first-choice induction regimen as it is more physiologic compared to an oral regimen and avoids the first-pass mechanism in the liver. In the case of poor compliance, administration of oral 17β-E2 or ethinyl estradiol could be offered. Incremental dose increases, approximately every 6 months, can contribute to mimic normal pubertal progression until adult dosing is reached over a 2- to 3-year period. Progestin should be added once breakthrough bleeding occurs or after 2 to 3 years of estrogen therapy or if ultrasound shows a mature uterus with thick endometrium. Treatment needs to be individualized and monitored by clinical assessment in relation to patient compliance and satisfaction. Well-designed prospective randomized clinical trials aimed to identify the best estrogen regimen for pubertal induction in TS girls are needed.

An extremely rare combination of acute intermittent porphyria and Turner syndrome

A very rare case of acute intermittent porphyria (AIP) co-existing Turner syndrome (TS) is reported for the first time. A 32-year-old woman was diagnosed with AIP due to recurrent acute abdominal pain, red urine and pathogenic mutation of Hydroxymethyl synthetase (HMBS) gene. At the same time, TS was confirmed by Karyotype analysis results of 46,X,i(X)(q10), which accompanied by primary amenorrhea, elevated serum concentrations of follicle-stimulating hormone (FSH). Since the first attack of AIP, the patient has been increasingly depressed, and Psychiatry identified major depression. Duloxetine was chosen after careful deliberation, and the patient's mood stabilized. AIP had not recurred after half a year. Since sex hormones are the exacerbating factor of acute attack of AIP, sex hormone replacement therapy for TS was not administered. In conclusion, the conditions of AIP co-existing TS are complicate, and the treatment still needs to be improved by multiple disciplines in the follow-up.

Sexual differentiation of brain and other tissues: Five questions for the next 50 years

This paper is part of the celebration of the 50th anniversary of founding of the journal Hormones and Behavior, the official journal of the Society for Behavioral Neuroendocrinology. All sex differences in phenotypic development stem from the sexual imbalance in X and Y chromosomes, which are the only known differences in XX and XY zygotes. The sex chromosome genes act within cells to cause differences in phenotypes of XX and XY cells throughout the body. In the gonad, they determine the type of gonad, leading to differences in secretion of testicular vs. ovarian hormones, which cause further sex differences in tissue function. These current ideas of sexual differentiation are briefly contrasted with a hormones-only view of sexual differentiation of the last century. The multiple, independent action of diverse sex-biasing agents means that sex-biased factors can be synergistic, increasing sex differences, or compensatory, making the two sexes more equal. Several animal models have been fruitful in demonstrating sex chromosome effects, and interactions with gonadal hormones. MRI studies of human brains demonstrate variation in brain structure associated with both differences in gonadal hormones, and in the number of X and Y chromosomes. Five unanswered questions are posed as a challenge to future investigators to improve understanding of sexual differentiation throughout the body.

Xist RNA in action: Past, present, and future

In mammals, dosage compensation of sex chromosomal genes between females (XX) and males (XY) is achieved through X-chromosome inactivation (XCI). The X-linked X-inactive-specific transcript (Xist) long noncoding RNA is indispensable for XCI and initiates the process early during development by spreading in cis across the X chromosome from which it is transcribed. During XCI, Xist RNA triggers gene silencing, recruits a plethora of chromatin modifying factors, and drives a major structural reorganization of the X chromosome. Here, we review our knowledge of the multitude of epigenetic events orchestrated by Xist RNA to allow female mammals to survive through embryonic development by establishing and maintaining proper dosage compensation. In particular, we focus on recent studies characterizing the interaction partners of Xist RNA, and we discuss how they have affected the field by addressing long-standing controversies or by giving rise to new research perspectives that are currently being explored. This review is dedicated to the memory of Denise Barlow, pioneer of genomic imprinting and functional long noncoding RNAs (lncRNAs), whose work has revolutionized the epigenetics field and continues to inspire generations of scientists.

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

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

Report of Spontaneous Internal Carotid Dissection in a Patient with Turner Syndrome with a Systematic Review of the Literature

BACKGROUND

Spontaneous isolated carotid artery (CA) or vertebral artery (VA) dissection in the absence of coarctation has rarely been reported in the literature. We report the case of a 20-year-old woman with Turner syndrome (TS) who developed an acute left middle cerebral artery territory ischemic stroke from a spontaneous left internal carotid artery (ICA) dissection. We also conducted a systematic review of the literature to identify prior studies establishing an association or other case reports of isolated CA or VA dissection in TS. We queried 5 databases: MEDLINE (PubMed), Scopus, Embase, Cochrane Central, and CINAHL EBSCO. We used a standardized search clause across databases. Inclusion and exclusion criteria were applied to articles retrieved. Studies were excluded based on title alone, abstract, or after vetting the data presented in the paper.

CASE DESCRIPTION

Three case reports of patients with TS presenting with spontaneous intracranial and/or extracranial dissection of the ICA or VA were identified and included in this review.

CONCLUSIONS

We present a case of bilateral spontaneous dissection of the ICA in a patient with TS. Only 3 reported cases of spontaneous extra- or intracranial dissection of the CA or VA were identified via a systematic review of the literature. Arterial dissection of the CA or VA, especially in absence of aortic coarctation, in individuals affected with TS suggest the possibility of systemic vasculopathy. More research is needed to establish a better understanding of the phenotypic effects of TS in macro- and microvascular structures.

The mouse as a model of fundamental concepts related to Turner syndrome

Although XO mice do not show many of the overt phenotypic features of Turner syndrome (TS; 45,X or XO), mice and humans share different classes of genes on the X chromosome that are more or less likely to cause TS phenotypes. Based on the evolutionary history of the sex chromosomes, and the pattern of dosage balancing among sex chromosomal and autosomal genes in functional gene networks, it is possible to prioritize types of X genes for study as potential causes of features of TS. For example, X-Y gene pairs are among the most interesting because of the convergent effects of X and Y genes that both are likely to prevent the effects of TS in XX and XY individuals. Many of the high-priority genes are shared by mouse and human X chromosomes, but are easier to study in genetically tractable mouse models. Several mouse models, used primarily for the study of sex differences in physiology and disease, also produce XO mice that can be investigated to understand the effects of X monosomy. Using these models will lead to the identification of specific X genes that make a difference when present in one or two copies. These studies will help to achieve a better appreciation of the contribution of these specific X genes to the syndromic features of TS.

Epigenetics in Turner syndrome

Background

Monosomy of the X chromosome is the most frequent genetic abnormality in human as it is present in approximately 2% of all conceptions, although 99% of these embryos are spontaneously miscarried. In postnatal life, clinical features of Turner syndrome may include typical dysmorphic stigmata, short stature, sexual infantilism, and renal, cardiac, skeletal, endocrine and metabolic abnormalities.

Main text

Turner syndrome is due to a partial or total loss of the second sexual chromosome, resulting in the development of highly variable clinical features. This phenotype may not merely be due to genomic imbalance from deleted genes but may also result from additive influences on associated genes within a given gene network, with an altered regulation of gene expression triggered by the absence of the second sex chromosome. Current studies in human and mouse models have demonstrated that this chromosomal abnormality leads to epigenetic changes, including differential DNA methylation in specific groups of downstream target genes in pathways associated with several clinical and metabolic features, mostly on autosomal chromosomes. In this article, we begin exploring the potential involvement of both genetic and epigenetic factors in the origin of X chromosome monosomy. We review the dispute between the meiotic and post-zygotic origins of 45,X monosomy, by mainly analyzing the findings from several studies that compare gene expression of the 45,X monosomy to their euploid and/or 47,XXX trisomic cell counterparts on peripheral blood mononuclear cells, amniotic fluid, human fibroblast cells, and induced pluripotent human cell lines. From these studies, a profile of epigenetic changes seems to emerge in response to chromosomal imbalance. An interesting finding of all these studies is that methylation-based and expression-based pathway analyses are complementary, rather than overlapping, and are correlated with the clinical picture displayed by TS subjects.

Conclusions

The clarification of these possible causal pathways may have future implications in increasing the life expectancy of these patients and may provide informative targets for early pharmaceutical intervention.

At Term, XmO and XpO Mouse Placentas Show Differences in Glucose Metabolism in the Trophectoderm-Derived Outer Zone

Genetic mouse model (39,XO) for human Turner Syndrome (45,XO) harboring either a single maternally inherited (Xm) or paternally inherited (Xp) chromosome show a pronounced difference in survival rate at term. However, a detailed comparison of XmO and XpO placentas to explain this difference is lacking. We aimed to investigate the morphological and molecular differences between XmO and XpO term mouse placentas. We observed that XpO placentas at term contained a significantly larger area of glycogen cells (GCs) in their outer zone, compared to XmO, XX, and XY placentas. In addition, the outer zone of XpO placentas showed higher expression levels of lactate dehydrogenase (Ldha) than XmO, XX, and XY placentas, suggestive of increased anaerobic glycolysis. In the labyrinth, we detected significantly lower expression level of trophectoderm (TE)-marker keratin 19 (Krt19) in XpO placentas than in XX placentas. The expression of other TE-markers was comparable as well as the area of TE-derived cells between XO and wild-type labyrinths. XpO placentas exhibited specific defects in the amount of GCs and glucose metabolism in the outer zone, suggestive of increased anaerobic glycolysis, as a consequence of having inherited a single Xp chromosome. In conclusion, the XpO genotype results in a more severe placental phenotype at term, with distinct abnormalities regarding glucose metabolism in the outer zone.

Avian W and mammalian Y chromosomes convergently retained dosage-sensitive regulators

After birds diverged from mammals, different ancestral autosomes evolved into sex chromosomes in each lineage. In birds, females are ZW and males ZZ, but in mammals females are XX and males XY. We sequenced the chicken W chromosome, compared its gene content with our reconstruction of the ancestral autosomes, and followed the evolutionary trajectory of ancestral W-linked genes across birds. Avian W chromosomes evolved in parallel with mammalian Y chromosomes, preserving ancestral genes through selection to maintain the dosage of broadly-expressed regulators of key cellular processes. We propose that, like the human Y chromosome, the chicken W chromosome is essential for embryonic viability of the heterogametic sex. Unlike other sequenced sex chromosomes, the chicken W did not acquire and amplify genes specifically expressed in reproductive tissues. We speculate that the pressures that drive the acquisition of reproduction related genes on sex chromosomes may be specific to the male germ line.

Anatomy of turner syndrome

Turner syndrome (TS) is one of the most common sex chromosome abnormalities and results from total or partial monosomy of the X chromosome. It occurs in 1 in 2000 newborn girls and is also believed to be present in a larger proportion of conceptuses. There are various anatomic anomalies that have been associated with TS and the consequences of late recognition of these anomalies can be devastating. Aortic dilation and dissection occur at increased rates in TS patients and contribute to the decreased life expectancy of these patients. Such cases have prompted the need for early identification and continuous monitoring. Other anatomic variations increase morbidity in this population, and negatively impact the social and reproductive aspects of their lives. In this review, we summarize the cardiovascular, neurological, genitourinary, otolaryngolical, craniofacial, and skeletal defects associated with TS. To elucidate these morphological variations, novel illustrations have also been constructed. Clin. Anat. 29:638-642, 2016. © 2016 Wiley Periodicals, Inc.

The Biology and Evolution of Mammalian Y Chromosomes

Mammals have the oldest sex chromosome system known: the mammalian X and Y chromosomes evolved from ordinary autosomes beginning at least 180 million years ago. Despite their shared ancestry, mammalian Y chromosomes display enormous variation among species in size, gene content, and structural complexity. Several unique features of the Y chromosome--its lack of a homologous partner for crossing over, its functional specialization for spermatogenesis, and its high degree of sequence amplification--contribute to this extreme variation. However, amid this evolutionary turmoil many commonalities have been revealed that have contributed to our understanding of the selective pressures driving the evolution and biology of the Y chromosome. Two biological themes have defined Y-chromosome research over the past six decades: testis determination and spermatogenesis. A third biological theme begins to emerge from recent insights into the Y chromosome's roles beyond the reproductive tract--a theme that promises to broaden the reach of Y-chromosome research by shedding light on fundamental sex differences in human health and disease.

Turner syndrome: update on biology and management across the life span

PURPOSE OF REVIEW

We review recent understanding of the pathophysiology, molecular biology, and management of Turner syndrome.

RECENT FINDINGS

Sophisticated genetic techniques are able to detect mosaicism in one-third of individuals previously thought to have monosomy X. Prenatal detection using maternal blood should permit noninvasive detection of most fetuses with an X chromosome abnormality. Disproportionate growth with short limbs has been documented in this condition, and a target gene of short stature homeobox, connective tissue growth factor (Ctgf), has been described. Liver disease is more common in Turner syndrome than previously recognized. Most girls have gonadal failure. Spontaneous puberty and menarche is more commonly seen in girls with XX mosaicism. Low-dose estrogen replacement therapy may be given early to induce a more normal onset and tempo of puberty. Oocyte donation for assisted reproduction carries a substantial risk, particularly if the woman has known cardiac or aortic disease. Neurodevelopmental differences in Turner syndrome are beginning to be correlated with differences in brain anatomy.

SUMMARY

An increased understanding of the molecular basis for aspects of this disorder is now developing. In addition, a renewed focus on health maintenance through the life span should provide better general and targeted healthcare for these girls and women.

Sonographic Prenatal Diagnosis of Turner Syndrome

Turner syndrome is the most common sex chromosome abnormality in female fetuses, in which all or part of one of the X chromosomes is absent or has some other abnormality. The syndrome has a number of characteristic sonographic findings such as diffuse fetal edema, cystic hygroma with septations, renal and cardiac anomalies, increased nuchal translucency, and growth retardation. A case is presented of Turner syndrome diagnosed by cytogenic testing after a number of anatomic anomalies, including diffuse edema, cystic hygroma and growth retardation, were found by sonography.

Mammalian Y chromosomes retain widely expressed dosage-sensitive regulators

The human X and Y chromosomes evolved from an ordinary pair of autosomes, but millions of years ago genetic decay ravaged the Y chromosome, and only three percent of its ancestral genes survived. We reconstructed the evolution of the Y chromosome across eight mammals to identify biases in gene content and the selective pressures that preserved the surviving ancestral genes. Our findings indicate that survival was non-random, and in two cases, convergent across placental and marsupial mammals. We conclude that the Y chromosome's gene content became specialized through selection to maintain the ancestral dosage of homologous X-Y gene pairs that function as broadly expressed regulators of transcription, translation and protein stability. We propose that beyond its roles in testis determination and spermatogenesis, the Y chromosome is essential for male viability, and plays unappreciated roles in Turner syndrome and in phenotypic differences between the sexes in health and disease.

Comparative cytogenetic analysis in two tissues with different lineage in Turner's syndrome patients: correlation with phenotype

OBJECTIVE

To analyze karyotype of Turner's syndrome (TS) patients in two tissues of different lineage, and to correlate them with phenotype.

STUDY DESIGN

An observational study was designed at the Gynaecological Endocrinology Unit of Hospital Clinic in Barcelona. Patients diagnosed with TS by blood karyotype were included, between 20 and 50 years of age. A new 50-cell count blood karyotype and a urethral cell karyotype from urine samples were performed. Data on some TS-related comorbidities were collected.

RESULTS

Twenty-seven TS patients were included. Urine cultures of 12 patients were contaminated by microorganisms. With 50-cell count blood karyotype, three cryptic mosaicisms were found. Six patients with mosaicism in blood karyotype showed pure monosomy in urine karyotype. Correlations exist between blood karyotype and phenotype where spontaneous menarche, height, dysmorphology, congenital malformations and hypothyroidism are concerned, whereas they did not appear in urine analysis.

CONCLUSIONS

Karyotyping T-lymphocytes in blood samples is the gold standard technique. 50-cell count may be considered if TS or ovarian failure is suspected, in order to detect cryptic mosaicisms. Urethral cell culture from urine samples presents technical difficulties and some limitations, due to the easier lost of abnormal X-chromosome. A partial correlation between blood karyotype and phenotype exists.

[Fertility on women with Turner syndrome]

Spontaneous pregnancies occur in 1.8 to 7.6% among women with Turner syndrome. A genetic counseling is required before conception because only 30 to 40% of these pregnancies lead to the birth of a healthy child. A check-up has to be done before pregnancy, and if authorized, it will be tightly followed-up. Pregnancy is contraindicated if cardiac or aortic malformations exist, except for bicuspid aortic valve. Teams advice single embryo transfer. Rates of pregnancies of 45 to 60% after oocyte donation, but 40 to 60% of spontaneous abortions are noted, due to uterine factors. A study is trying to define patients who could postulate to cryopreservation of ovarian tissue.

Bicuspid aortic valve and aortic coarctation are linked to deletion of the X chromosome short arm in Turner syndrome

Background

Congenital heart disease (CHD) is a cardinal feature of X chromosome monosomy, or Turner syndrome (TS). Haploinsufficiency for gene(s) located on Xp have been implicated in the short stature characteristic of the syndrome, but the chromosomal region related to the CHD phenotype has not been established.

Design

We used cardiac MRI to diagnose cardiovascular abnormalities in four non-mosaic karyotype groups based on 50-metaphase analyses: 45,X (n=152); 46,X,del(Xp) (n=15); 46,X,del(Xq) (n=4); and 46,X,i(Xq) (n=14) from peripheral blood cells.

Results

Bicuspid aortic valves (BAV) were found in 52/152 (34%) 45,X study subjects and aortic coarctation (COA) in 19/152 (12.5%). Isolated anomalous pulmonary veins (APV) were detected in 15/152 (10%) for the 45,X study group, and this defect was not correlated with the presence of BAV or COA. BAVs were present in 28.6% of subjects with Xp deletions and COA in 6.7%. APV were not found in subjects with Xp deletions. The most distal break associated with the BAV/COA trait was at cytologic band Xp11.4 and ChrX:41,500 000. One of 14 subjects (7%) with the 46,X,i(Xq) karyotype had a BAV and no cases of COA or APV were found in this group. No cardiovascular defects were found among four patients with Xq deletions.

Conclusions

The high prevalence of BAV and COA in subjects missing only the X chromosome short arm indicates that haploinsufficiency for Xp genes contributes to abnormal aortic valve and aortic arch development in TS.

FISH with whole chromosome and telomeric probes demonstrates huge karyotypic reorganization with ITS between two species of Oryzomyini (Sigmodontinae, Rodentia): Hylaeamys megacephalus probes on Cerradomys langguthi karyotype

Rodentia comprises 42 % of living mammalian species. The taxonomic identification can be difficult, the number of species currently known probably being underestimated, since many species show only slight morphological variations. Few studies surveyed the biodiversity of species, especially in the Amazon region. Cytogenetic studies show great chromosomal variability in rodents, with diploid numbers ranging from 10 to 102, making it difficult to find chromosomal homologies by comparative G banding. Chromosome painting is useful, but only a few species of rodents have been studied by this technique. In this study, we sorted whole chromosome probes by fluorescence-activated cell sorting from two Hylaeamys megacephalus individuals, an adult female (2n = 54) and a fetus (2n = 50). We made reciprocal chromosome painting between these karyotypes and cross-species hybridization on Cerradomys langguthi (2n = 46). Both species belong to the tribe Oryzomyini (Sigmodontinae), which is restricted to South America and were collected in the Amazon region. Twenty-four chromosome-specific probes from the female and 25 from the fetus were sorted. Reciprocal chromosome painting shows that the karyotype of the fetus does not represent a new cytotype, but an unbalanced karyotype with multiple rearrangements. Cross-species hybridization of H. megacephalus probes on metaphases of C. langguthi shows that 11 chromosomes of H. megacephalus revealed conserved synteny, 10 H. megacephalus probes hybridized to two chromosomal regions and three hybridized to three regions. Associations were observed on chromosomes pairs 1-4 and 11. Fluorescence in situ hybridization with a telomeric probe revealed interstitial regions in three pairs (1, 3, and 4) of C. langguthi chromosomes. We discuss the genomic reorganization of the C. langguthi karyotype.

Noninvasive prenatal aneuploidy testing of chromosomes 13, 18, 21, X, and Y, using targeted sequencing of polymorphic loci

OBJECTIVE

This study aims to develop a noninvasive prenatal test on the basis of the analysis of cell-free DNA in maternal blood to detect fetal aneuploidy at chromosomes 13, 18, 21, X, and Y.

METHODS

A total of 166 samples from pregnant women, including 11 trisomy 21, three trisomy 18, two trisomy 13, two 45,X, and two 47,XXY samples, were analyzed using an informatics-based method. Cell-free DNA from maternal blood was isolated, amplified using a multiplex polymerase chain reaction (PCR) assay targeting 11,000 single nucleotide polymorphisms on chromosomes 13, 18, 21, X, and Y in a single reaction, and sequenced. A Bayesian-based maximum likelihood statistical method was applied to determine the chromosomal count of the five chromosomes interrogated in each sample, along with a sample-specific calculated accuracy for each test result.

RESULTS

The algorithm correctly reported the chromosome copy number at all five chromosomes in 145 samples that passed a DNA quality test, for a total of 725/725 correct calls. The average calculated accuracy for these samples was 99.92%. Twenty-one samples did not pass the DNA quality test.

CONCLUSIONS

This informatics-based method noninvasively detected fetuses with trisomy 13, 18, and 21, 45,X, and 47,XXY with high sample-specific calculated accuracies for each individual chromosome and across all five chromosomes.

Aneuploid human embryonic stem cells: origins and potential for modeling chromosomal disorders

Chromosomal aneuploidies are widely recognized genetic disorders in humans that often lead to spontaneous abortion. Aneuploid fetuses that survive to term commonly exhibit impaired developmental growth and mental retardation in addition to multiple congenital malformations. Preimplantation genetic screening is used to detect chromosomal aneuploidies in early embryos. Human embryonic stem cell (ESC) cell lines generated from aneuploid embryos created a unique repository of cell lines. The spectrum of aneuploidies in these ESC lines reflects the range of common embryonic chromosomal aberrations and significantly differs from the spectrum of aneuploid human ESC lines generated by cell adaptation in culture. The aneuploid human ESC lines represent an excellent model to study human chromosomal abnormalities especially in the early stages of development.

[Klinefelter's syndrome and Turner's syndrome. For a better management]

Klinefelter's syndrome (KS) affects one in 600 men and Turner's syndrome (TS), one in 2500 women. These 2 diseases are the most sex chromosome disorders characterized by one extra X in the SK male (47XXY) and the loss of an X in the girls with ST (45 X). Their common characteristic is the gonadal dysgenesis, which is the main cause of male or female infertility. Called "the forgotten syndrome", KS is under-diagnosed because apart from the large size, there are no dysmorphic features, along with a great ignorance of cognitive and language disorders in children. There are often comorbidities that lead to diagnosis such as autoimmune diseases or metabolic syndrome. TS is often diagnosed by the short stature. Management of Turner's girls has profoundly changed with Growth hormone therapy. There is an international consensus for a better management of associated diseases such as ORL, cardiac, renal, hepatic, autoimmune and metabolic diseases. Prenatal diagnosis allows early detection and management of cognitive deficiencies and of associated diseases.

DNMT3L is a regulator of X chromosome compaction and post-meiotic gene transcription

Previous studies on the epigenetic regulator DNA methyltransferase 3-Like (DNMT3L), have demonstrated it is an essential regulator of paternal imprinting and early male meiosis. Dnmt3L is also a paternal effect gene, i.e., wild type offspring of heterozygous mutant sires display abnormal phenotypes suggesting the inheritance of aberrant epigenetic marks on the paternal chromosomes. In order to reveal the mechanisms underlying these paternal effects, we have assessed X chromosome meiotic compaction, XY chromosome aneuploidy rates and global transcription in meiotic and haploid germ cells from male mice heterozygous for Dnmt3L. XY bodies from Dnmt3L heterozygous males were significantly longer than those from wild types, and were associated with a three-fold increase in XY bearing sperm. Loss of a Dnmt3L allele resulted in deregulated expression of a large number of both X-linked and autosomal genes within meiotic cells, but more prominently in haploid germ cells. Data demonstrate that similar to embryonic stem cells, DNMT3L is involved in an auto-regulatory loop in germ cells wherein the loss of a Dnmt3L allele resulted in increased transcription from the remaining wild type allele. In contrast, however, within round spermatids, this auto-regulatory loop incorporated the alternative non-coding alternative transcripts. Consistent with the mRNA data, we have localized DNMT3L within spermatids and sperm and shown that the loss of a Dnmt3L allele results in a decreased DNMT3L content within sperm. These data demonstrate previously unrecognised roles for DNMT3L in late meiosis and in the transcriptional regulation of meiotic and post-meiotic germ cells. These data provide a potential mechanism for some cases of human Klinefelter's and Turner's syndromes.

Human embryonic stem cells as models for aneuploid chromosomal syndromes

Syndromes caused by chromosomal aneuploidies are widely recognized genetic disorders in humans and often lead to spontaneous miscarriage. Preimplantation genetic screening is used to detect chromosomal aneuploidies in early embryos. Our aim was to derive aneuploid human embryonic stem cell (hESC) lines that may serve as models for human syndromes caused by aneuploidies. We have established 25 hESC lines from blastocysts diagnosed as aneuploid on day 3 of their in vitro development. The hESC lines exhibited morphology and expressed markers typical of hESCs. They demonstrated long-term proliferation capacity and pluripotent differentiation. Karyotype analysis revealed that two-third of the cell lines carry a normal euploid karyotype, while one-third remained aneuploid throughout the derivation, resulting in eight hESC lines carrying either trisomy 13 (Patau syndrome), 16, 17, 21 (Down syndrome), X (Triple X syndrome), or monosomy X (Turner syndrome). On the basis of the level of single nucleotide polymorphism heterozygosity in the aneuploid chromosomes, we determined whether the aneuploidy originated from meiotic or mitotic chromosomal nondisjunction. Gene expression profiles of the trisomic cell lines suggested that all three chromosomes are actively transcribed. Our analysis allowed us to determine which tissues are most affected by the presence of a third copy of either chromosome 13, 16, 17 or 21 and highlighted the effects of trisomies on embryonic development. The results presented here suggest that aneuploid embryos can serve as an alternative source for either normal euploid or aneuploid hESC lines, which represent an invaluable tool to study developmental aspects of chromosomal abnormalities in humans.

Cardiovascular Disorders of Turner's Syndrome: A Review

A series of cardiovascular abnormalities may be associated with Turner's Syndrome (TS). Over 50% of the reported cardiovascular malformations have been bicuspid aortic valve or coarctation of the aorta alone. or in a combination, which may lead to a higher risk for infective endocarditis. Isolated dilation of the ascending aorta was often seen in TS, while aortic dissection has been increasingly observed in recent years. The aortic root dilation was found more likely to be due to a mesenchymal defect rather than atherosclerotic changes. Women with TS are often hypertensive as a result of aortic abnormality or renal vascular disorder. They have an increased risk of developing neoplasms, such as gonadoblastoma and dysgerminoma, and therefore they may require regular monitoring while receiving hormone therapy. In patients with gonadal dysgenesis, exogenous estrogen treatment poses a problem of connective tissue disorders of the great vessels. To resolve the contradiction between exogenous estrogen therapies and the hold-up of the progression of the connective tissue abnormality is a topic to be coped with. Careful clinical assessment is mandatory in the evaluation of patients with TS with cardiovascular abnormalities.

Studying early lethality of 45,XO (Turner's syndrome) embryos using human embryonic stem cells

Turner's syndrome (caused by monosomy of chromosome X) is one of the most common chromosomal abnormalities in females. Although 3% of all pregnancies start with XO embryos, 99% of these pregnancies terminate spontaneously during the first trimester. The common genetic explanation for the early lethality of monosomy X embryos, as well as the phenotype of surviving individuals is haploinsufficiency of pseudoautosomal genes on the X chromosome. Another possible mechanism is null expression of imprinted genes on the X chromosome due to the loss of the expressed allele. In contrast to humans, XO mice are viable, and fertile. Thus, neither cells from patients nor mouse models can be used in order to study the cause of early lethality in XO embryos. Human embryonic stem cells (HESCs) can differentiate in culture into cells from the three embryonic germ layers as well as into extraembryonic cells. These cells have been shown to have great value in modeling human developmental genetic disorders. In order to study the reasons for the early lethality of 45,XO embryos we have isolated HESCs that have spontaneously lost one of their sex chromosomes. To examine the possibility that imprinted genes on the X chromosome play a role in the phenotype of XO embryos, we have identified genes that were no longer expressed in the mutant cells. None of these genes showed a monoallelic expression in XX cells, implying that imprinting is not playing a major role in the phenotype of XO embryos. To suggest an explanation for the embryonic lethality caused by monosomy X, we have differentiated the XO HESCs in vitro an in vivo. DNA microarray analysis of the differentiated cells enabled us to compare the expression of tissue specific genes in XO and XX cells. The tissue that showed the most significant differences between the clones was the placenta. Many placental genes are expressed at much higher levels in XX cells in compare to XO cells. Thus, we suggest that abnormal placental differentiation as a result of haploinsufficiency of X-linked pseudoautosomal genes causes the early lethality in XO human embryos.

Healthcare for adolescents with Turner syndrome

This review paper highlights important healthcare issues for adolescents with Turner Syndrome. Turner Syndrome potentially affects multiple organ systems including: cardiovascular, renal, endocrine, neurologic, gastrointestinal, skin, skeletal, auditory, and reproductive systems. Congenital and acquired cardiac defects remain the most significant health problem faced by women with Turner Syndrome.

Optimising management in Turner syndrome: from infancy to adult transfer

Turner syndrome can be defined as loss or abnormality of the second X chromosome in at least one cell line in a phenotypic female. The condition occurs in approximately 1 in every 2000 live female births,(1) so that in the UK the prevalence for any year of life is in the region of 200 girls. The condition is much more common in utero, it being estimated that 1-2% of all conceptuses are affected, of whom only 1% will survive to term.

Turner syndrome: Evaluation of prenatal diagnosis in 19 European registries

This study evaluated the prenatal diagnosis of Turner syndrome by ultrasound examination in an unselected population from all over Europe. Data from 19 congenital malformation registries from 11 European countries were analyzed. Turner syndrome was diagnosed in 125 cases (7.2%) in a total of 1,738 chromosome abnormalities. Sixty-seven percent of cases were detected prenatally by ultrasound examination due to the presence of congenital defects. The most frequent anomalies were cystic hygroma (59.5%) and hydrops fetalis (19%). The most frequent karyotype was 45,X (81.6%) followed by different types of mosaicism (16.8%). Significant differences in congenital defects (P = 0.0003) were observed between 45,X karyotypes and 45,X mosaicism cases. Prenatal counseling for 45,X mosaicism should take into account the expectation of a milder phenotype. In 78.6% of cases diagnosed by ultrasound examination due to congenital anomalies, the pregnancy was terminated. Prenatal detection of Turner syndrome by ultrasound examination was high in this unselected population.

Turner syndrome in adolescence

The management of a patient with Turner syndrome is complex and multi-faceted. It is best accomplished by an interdisciplinary approach. Initial diagnosis is generally prenatal or suggested by physical characteristics. Diagnosis should include karyotype analysis and potentially a probe for Y-chromosome centromeric material to assess the risk for the development of germ cell tumors. At the time of initial diagnosis, the patient should be thoroughly investigated for associated medical conditions. Ongoing surveillance for the development of complications is of paramount importance. The interdisciplinary team should include an endocrinologist; cardiologist; nephrologist; reproductive endocrinologist; audiological physician; ear, nose and throat surgeon; plastic surgeon; dentist; and psychologist . It is important to provide to girls and women with Turner syndrome, and their families, comprehensive information about the syndrome and to advise them about the availability of Turner syndrome societies that can provide information and support.

Aortic dissection in a young woman with Turner's syndrome

Aortic dissection is an extremely rare occurrence often associated with fatal consequences. Among women suffering from Turner's syndrome, a mosaic of cardiovascular anomalies, some congenital, are often reported. Among these abnormalities, the conjunction of dilatation of the aorta with hypertension may lead to aortic dissection. A high level of clinical follow-up is necessary on a lifetime basis in order to diagnose such patients on time, which will allow preventive surgical intervention. Successive echocardiographic surveillance of these patients is recommended in addition to aggressive antihypertensive therapy in order to minimize potential morbidity and mortality as much as possible. If aortic dissection is diagnosed on time, surgical intervention can be lifesaving. In this communication, we report on a patient whose diagnosis was missed and consequently expired due to severe aortic dissection.

Parental origin of normal X chromosomes in Turner syndrome patients with various karyotypes: implications for the mechanism leading to generation of a 45,X karyotype

The parental origin of the X chromosome of 45,X females has been the subject of many studies, and most of them have shown that the majority (60-80%) of the X chromosomes are maternal in origin. However, studies on the parental origin of normal X chromosomes are relatively limited for Turner syndrome (TS) females with sex chromosome aberrations. In this study, we used PCR-based typing of highly polymorphic markers and an assay of methylation status of the androgen receptor gene to determine the parental origin of normal X chromosomes in 50 unbiased TS females with a variety of karyotypes. Our results showed a higher paternal meiotic error rate leading to the generation of abnormal sex chromosomes, especially in the case of del(Xp) and abnormal Y chromosomes. Isochromosome Xq and ring/marker X chromosomes, on the other hand, were equally likely the result of both maternal and paternal meiotic errors. A thorough review of previous results, together with our data suggests, that the majority of TS karyotype are caused by paternal meiotic errors that generate abnormal sex chromosomes, and that most 45,X cells are generated by mitotic loss of these abnormal sex chromosomes, resulting in maternal X dominance in these cells.

The impact and management of Turner's syndrome in adult life

Turner's syndrome (TS), caused by an absent or structurally abnormal X chromosome, affects 1 in 2500 live female births. Most medical attention has focused on the attainment of final height in childhood and, when this has been achieved, many women are discharged to primary care. It has become increasingly evident that adults with Turner's syndrome are susceptible to a range of disorders such as osteoporosis, hypothyroidism and diabetes. Because of these, and because of the need for long-term oestrogen replacement, it seems most practical for adult health surveillance in TS to come under the remit of the endocrinologist. It must be accepted, however, that the reduced life expectancy in women with TS is largely accounted for by cardiovascular disease. Also, the commonly observed social isolation in adults with TS can be linked to deafness that is increasingly prevalent in an ageing group. Co-ordination of all these issues requires a dedicated multidisciplinary clinic along the lines of those in place in diabetes.

Microsatellite analysis in Turner syndrome: parental origin of X chromosomes and possible mechanism of formation of abnormal chromosomes

Turner syndrome is a chromosomal disorder in which all or part of one X chromosome is missing. The meiotic or mitotic origin of most cases remains unknown due to the difficulty in detecting hidden mosaicism and to the lack of meiotic segregation studies. We analyzed 15 Turner patients, 10 with a 45,X whereas the rest had a second cell line with abnormal X-chromosomes: a pseudodicentric, an isochromosome, one large and one small ring, and the last with a long arm deletion. Our aims were: to detect X cryptic mosaicism in patients with a 45,X constitution; to determine the parental origin of the abnormality; to infer the zygotic origin of the karyotype and to suggest the timing and mechanism of the error(s) leading to the formation of abnormal X chromosomes from maternal origin. Molecular investigation did not revealed heterozygosity for any microsatellite, excluding X mosaicism in the 45,X cases. Parental origin of the single X chromosome was maternal in 90% of these patients. Three of the structurally abnormal Xs were maternally derived whereas the other two were paternal. These results allowed us to corroborate breakpoints in these abnormal X chromosomes and suggest that the pseudodicentric chromosome originated from post-zygotic sister chromatid exchange, whereas the Xq deleted chromosome probably arose after a recombination event during maternal meiosis.

Retarded postimplantation development of X0 mouse embryos: impact of the parental origin of the monosomic X chromosome

About 12-17% of the embryos obtained by mating mice carrying the In(X)1H or Paf mutations are of the 39,X (X0) genotype. Depending on the mutant mice used for mating, the monosomic X chromosome can be inherited from the paternal (XP) or the maternal (XM) parent. The XP0 embryos display developmental retardation at gastrulation and early organogenesis. XP0 embryos also display poor development of the ectoplacental cone, which is significantly smaller in size and contains fewer trophoblasts than XX siblings. In contrast, XM0 embryos develop normally and are indistinguishable from XX littermates. In both types of X0 embryos, an X-linked lacZ transgene is expressed in nearly all cells in both the embryonic and the extraembryonic tissues, suggesting that X inactivation does not occur when only one X is present. Of particular significance is the maintenance of an active XP chromosome in the extraembryonic tissues where normally the paternal X chromosome is preferentially inactivated in XX embryos. The differential impact of the inheritance of X chromosomes from different parents on the development of the X0 embryos raises the possibility that the XP is less capable than the XM in providing the appropriate dosage of X-linked activity that is necessary to support normal development of the embryo and the ectoplacental cone. Alternatively, the development of the XP0 embryo may be compromised by the lack of activity of one or several X-linked genes which are expressed only from the maternal X chromosome. Without the activity of these genes, embryonic development may be curtailed even though all other loci on the XP chromosome are actively transcribed.

Characterisation of the coding sequence and fine mapping of the human DFFRY gene and comparative expression analysis and mapping to the Sxrb interval of the mouse Y chromosome of the Dffry gene

DFFRY (the Y-linked homologue of the DFFRX Drosophila fat-facets related X gene) maps to proximal Yq11.2 within the interval defining the AZFa spermatogenic phenotype. The complete coding region of DFFRY has been sequenced and shows 89% identity to the X-linked gene at the nucleotide level. In common with DFFRX , the potential amino acid sequence contains the conserved Cys and His domains characteristic of ubiquitin C-terminal hydrolases. The human DFFRY mRNA is expressed in a wide range of adult and embryonic tissues, including testis, whereas the homologous mouse Dffry gene is expressed specifically in the testis. Analysis of three azoospermic male patients has shown that DFFRY is deleted from the Y chromosome in these individuals. Two patients have a testicular phenotype which resembles Sertoli cell-only syndrome, and the third diminished spermatogenesis. In all three patients, the deletions extend from close to the 3' end into the gene, removing the entire coding sequence of DFFRY. The mouse Dffry gene maps to the Sxrb deletion interval on the short arm of the mouse Y chromosome and its expression in mouse testis can first be detected between 7.5 and 10.5 days after birth when type A and B spermatogonia and pre-leptotene and leptotene spermatocytes are present.