Autosomal and X chromosome structural variants are associated with congenital heart defects in Turner syndrome: The NHLBI GenTAC registry.

Turner Syndrome (TS) is a developmental disorder caused by partial or complete loss of one sex chromosome. Bicuspid aortic valve and other left-sided congenital heart lesions (LSL), including thoracic aortic aneurysms and acute aortic dissections, are 30-50 times more frequent in TS than in the general population. In 454 TS subjects, we found that LSL are significantly associated with reduced dosage of Xp genes and increased dosage of Xq genes. We also showed that genome-wide copy number variation is increased in TS and identify a common copy number variant (CNV) in chromosome 12p13.31 that is associated with LSL with an odds ratio of 3.7. This CNV contains three protein-coding genes (SLC2A3, SLC2A14, and NANOGP1) and was previously implicated in congenital heart defects in the 22q11 deletion syndrome. In addition, we identified a subset of rare and recurrent CNVs that are also enriched in non-syndromic BAV cases. These observations support our hypothesis that X chromosome and autosomal variants affecting cardiac developmental genes may interact to cause the increased prevalence of LSL in TS. © 2016 Wiley Periodicals, Inc.

Proceedings from the Turner Resource Network symposium: the crossroads of health care research and health care delivery.

Turner syndrome, a congenital condition that affects ∼1/2,500 births, results from absence or structural alteration of the second sex chromosome. There has been substantial effort by numerous clinical and genetic research groups to delineate the clinical, pathophysiological, cytogenetic, and molecular features of this multisystem condition. Questions about the molecular-genetic and biological basis of many of the clinical features remain unanswered, and health care providers and families seek improved care for affected individuals. The inaugural "Turner Resource Network (TRN) Symposium" brought together individuals with Turner syndrome and their families, advocacy group leaders, clinicians, basic scientists, physician-scientists, trainees and other stakeholders with interest in the well-being of individuals and families living with the condition. The goal of this symposium was to establish a structure for a TRN that will be a patient-powered organization involving those living with Turner syndrome, their families, clinicians, and scientists. The TRN will identify basic and clinical questions that might be answered with registries, clinical trials, or through bench research to promote and advocate for best practices and improved care for individuals with Turner syndrome. The symposium concluded with the consensus that two rationales justify the creation of a TRN: inadequate attention has been paid to the health and psychosocial issues facing girls and women who live with Turner syndrome; investigations into the susceptibility to common disorders such as cardiovascular or autoimmune diseases caused by sex chromosome deficiencies will increase understanding of disease susceptibilities in the general population.

Single-nucleotide polymorphism array genotyping is equivalent to metaphase cytogenetics for diagnosis of Turner syndrome.

PURPOSE: Turner syndrome is a developmental disorder caused by partial or complete monosomy for the X chromosome in 1 in 2,500 females. We hypothesized that single-nucleotide polymorphism (SNP) array genotyping could provide superior resolution in comparison to metaphase karyotype analysis to facilitate genotype-phenotype correlations. METHODS: We genotyped 187 Turner syndrome patients with 733,000 SNP marker arrays. All cases met diagnostic criteria for Turner syndrome based on karyotypes (60%) or characteristic physical features. The SNP array results confirmed the diagnosis of Turner syndrome in 100% of cases. RESULTS: We identified a single X chromosome (45,X) in 113 cases. In 58 additional cases (31%), other mosaic cell lines were present, including isochromosomes (16%), rings (5%), and Xp deletions (8%). The remaining cases were mosaic for monosomy X and normal male or female cell lines. Array-based models of X chromosome structure were compatible with karyotypes in 104 of 116 comparable cases (90%). We found that the SNP array data did not detect X-autosome translocations (three cases) but did identify two derivative Y chromosomes and 13 large copy-number variants that were not detected by karyotyping. CONCLUSION: Our study is the first systematic comparison between the two methods and supports the utility of SNP array genotyping to address clinical and research questions in Turner syndrome.

X chromosome parental origin and aortic stiffness in turner syndrome.

INTRODUCTION: Aortic abnormalities contribute to increased morbidity and mortality of women with Turner syndrome (TS). Impaired aortic stiffness may prove to have clinical prognostic value in TS as is the case in other diseases such as Marfan syndrome, diabetes and hypertension. Additionally, the parental origin of the X chromosome in TS may influence aortic stiffness. OBJECTIVE: To assess the relation between X chromosome parental origin and aortic stiffness in TS patients. METHODS: Twenty-four subjects with TS participated in this cross-sectional study at a tertiary care centre. The parental origin of the X chromosome was determined. Cardiac-gated multidetector computerized tomography (MDCT) was performed and distensibility of the ascending aorta (AA), a measure of aortic stiffness, was calculated. RESULTS: Fourteen women were Xm (maternal origin) and 10 were Xp (paternal origin) for their inheritance of the single X chromosome. Age, body size, blood pressure and AA areas were similar in the two groups. However, the calculated AA distensibility was significantly lower in the Xm group (2·8 ± 1·1 mm/Hg) than in the Xp group (4·1 ± 1·5 mm/Hg); P < 0·05. Conclusion This study demonstrates that TS subjects that inherit their single X chromosome from their mother (Xm) have a significantly stiffer aorta compared with the TS with a paternally originating X chromosome (Xp), consistent with a potentially greater risk for cardiovascular complications. These findings suggest that parental chromosomal analysis and aortic stiffness measurements would be useful for the risk assessment and clinical management of TS patients.

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.

Serious aortic complications in a patient with Turner syndrome.

An asymptomatic young woman was discovered to have life-threatening aneurysms and dissection of the thoracic aorta during routine evaluation in a Turner syndrome (TS) study. The presence of a heart murmur and hypertension had led to diagnosis and surgical repair of an atrial septal defect at age 5 and of aortic coarctation at age 12. The diagnosis of TS was made at 16 years of age due to short stature and delayed pubertal development. She was treated with growth hormone from age 16 to 18 and with atenolol, thyroid hormone, and estrogen. She discontinued her medications and was lost to medical follow-up at age 20. Upon presenting here at age 26, she reported a very active lifestyle, including vigorous exercise and an acting career, with no symptoms of chest or back pain or shortness of breath. Cardiovascular imaging revealed aortic regurgitation, an unsuspected dissection of a severely dilated ascending aorta, and a large descending aortic aneurysm. She required surgical replacement of her aortic valve and ascending aorta, followed by endovascular repair of the descending aortic aneurysm. This patient illustrates the importance of considering the diagnosis of TS in girls with congenital aortic defects and the absolute necessity for close, expert follow-up of these patients who are at high risk for complications after surgical repair due to an underlying aortopathy, hypertension, and metabolic disorders. This patient also emphasizes the need to publicize and follow screening guidelines as there is an increasing number of patients with congenital defects who need transition to adult care.

N-terminal pro-brain natriuretic peptide levels and aortic diameters.

BACKGROUND: Women with X-chromosome monosomy or Turner syndrome (TS) are at increased risk for aortic dilation and dissection. To better understand the pathology and develop tools to monitor the risk of aortic disease, we investigated N-terminal pro-brain natriuretic peptide (BNP) (NT-proBNP) levels in women with TS and healthy female controls. METHODS: We evaluated NT-proBNP levels in women with karyotype-proven TS and healthy female volunteers in relation to ascending aortic diameter and descending aortic diameter measured by cardiovascular magnetic resonance imaging. RESULTS: The NT-proBNP levels were strongly and positively correlated with ascending aortic diameter and descending aortic diameter in both cohorts. The TS group (n = 114, age 37.4 ± 12 yr) had greater body surface area-indexed aortic diameters and higher NT-proBNP levels than the control group (n = 27, age 46.4 ± 11 years): 88.3 ± 62.7 versus 53.5 ± 35 pg/mL, P = .0003. Within the TS group, NT-proBNP levels were higher in those with dilated ascending aorta (n = 42, 112.4 ± 75.7 pg/mL) compared with those with normal aortic dimensions (n = 72, 74.2 ± 49 pg/mL, P = .0014). Abnormally high NT-pro BNP levels were seen in 3 of 4 TS women who presented with previously undetected aortic aneurysm and/or dissection. CONCLUSIONS: The NT-proBNP levels are positively associated with aortic diameters in women with and without TS, suggesting a role for BNP in arterial wall homeostasis. Further study is necessary to determine whether NT-proBNP measurement may be used to monitor aortic diameter and/or detect aortic pathology in individuals at risk for aortic disease.

Autoimmune disorders in women with turner syndrome and women with karyotypically normal primary ovarian insufficiency.

The higher prevalence of autoimmune diseases in women compared to men could be due to effects of ovarian hormones, pregnancy and/or the presence of a second X chromosome. To elucidate the role of these factors, we investigated the prevalence and spectrum of autoimmune diagnoses in women with primary ovarian insufficiency associated with X chromosome monosomy (Turner syndrome, TS, n = 244) and women with karyotypically normal (46,XX) primary ovarian insufficiency (POI, n = 457) in a prospective study, conducted at the National Institutes of Health. We compared the study group prevalence to normative data for the U.S. population of women. Chronic lymphocytic (Hashimoto's) thyroiditis (HT) occurred in 37% of women with TS vs. 15% with POI (P < 0.0001); HT prevalence in both ovarian insufficiency groups significantly exceeded that in U.S. population of women (5.8%). Inflammatory bowel (IBD, 4%) and celiac disease (CD, 2.7%) were significantly increased in TS, but not in POI. No other autoimmune diagnosis, including Graves' disease or Type 1 diabetes appears to be significantly increased in either group. Women with TS had higher pro-inflammatory IL6 and TGF ß1 levels (p < 0.0001 for both), and lower anti-inflammatory IL10 and TGF ß2 levels (p < 0.005 for both) compared to POI and to normal volunteers. Lifetime estrogen exposure and parity were significantly lower in TS compared to POI, which were in turn lower than the general population of women. The finding that lymphocytic thyroiditis is greatly increased in both women with TS and POI suggests that factors associated with ovarian insufficiency per se promote this form of autoimmunity. The absence of a normal second X-chromosome further contributes to increased autoimmunity in TS.

Trends in GH use in a Turner syndrome natural history study.

The present observations are derived from 273 girls and women aged 7-40 years participating in the National Institutes of Health natural history study of Turner syndrome (TS) in the interval 2001-2011. There was a higher percentage of GH use among individuals in the pediatric age group (7-17, n = 118, 83%) compared to young adult women with prior GH use (18-40, n = 155, 61%). The major factor in this divergence seems to be a trend toward earlier diagnosis of TS in the younger age group. We find a striking association between history of GH use and lower total body and abdominal fat mass in young adults with TS approximately one decade after discontinuation of GH treatment. The interpretation of this observation is limited by the fact that our study subjects were not randomly assigned to GH treatment. There may be a bias involving poor health care, childhood obesity, delayed diagnosis, absent GH treatment and persistent adult obesity. Further studies on the socioeconomic factors implicated in patterns of GH use and non-use for girls with TS are needed to illuminate this important issue.

Genomic imprinting and Turner syndrome.

The term 'genomic imprinting' refers to selective repression of transcription from distinct chromosomal regions determined by their maternal or paternal inheritance. There are two potentially important aspects of imprinting that may manifest in individuals with X monosomy, or Turner syndrome (TS). Given that men are monosomic for Xm while women are mosaic for Xm:Xp, genomic imprinting of important X-linked genes should be associated with sexually dimorphic traits, e.g., social skills, regional fat deposition and adult height. Such X-imprinted traits are predicted to differ in Turner groups monosomic for Xm vs. Xp. We review relevant studies of psychosocial attributes, regional fat distribution and height in TS related to parent of origin for the single normal X chromosome. In addition, we review recent evidence that monosomy for the X chromosome per se, regardless of the parental origin, may disrupt the normal distribution of autosomal imprint patterns. This may contribute to a high rate of fetal loss in human monosomy via impaired placentation in the most severe cases, and to loss of paternal contribution to growth in the mildest manifestation.

Perturbation of the transforming growth factor ß system in Turner syndrome.

OBJECTIVE: To measure components of the circulating transforming growth factor ß (TGFß) system in patients with Turner syndrome (TS) compared to relevant controls and to ascertain correlation with endocrine and cardiovascular parameters. METHODS: TGFß1, TGFß2 and endoglin (a vascular TGF receptor component) were measured using enzyme-linked immunoassays in the sera of 40 subjects with TS and 40 healthy volunteer women. The cardiovascular phenotype in TS subjects was extensively characterized by cardiac magnetic resonance (MR) and echo. RESULTS: TGFß1 levels were about 3-fold higher in TS while TGFß2 levels were about 3.5-fold higher in controls (P<0.000 1 for both). Soluble endoglin levels were 25% higher in TS (P<0.000 1). Variation in TGFß system components was not explained by age, blood pressure, platelet count, thyroid function, body proportions or cardiovascular phenotype. CONCLUSION: There is profound perturbation of the TGFß system evident in the circulation of individuals with TS.

Monosomy for the X chromosome.

Dosage compensation serves to equalize X chromosome gene expression in mammalian males and females and involves extensive silencing of the 2nd X chromosome in females. If dosage compensation mechanisms completely suppressed the 2nd X chromosome, then actual physical loss of this "eXtra" chromosome should have few consequences. However, X monosomy has major effects upon normal development, fertility and longevity in humans and some other species. This article reviews observations and arguments attempting to explain the phenotypic effects of X monosomy in humans and other mammals in terms of X chromosome gene dosage.

Androgens and the breast.

Androgens have important physiological effects in women while at the same time they may be implicated in breast cancer pathologies. However, data on the effects of androgens on mammary epithelial proliferation and/or breast cancer incidence are not in full agreement. We performed a literature review evaluating current clinical, genetic and epidemiological data regarding the role of androgens in mammary growth and neoplasia. Epidemiological studies appear to have significant methodological limitations and thus provide inconclusive results. The study of molecular defects involving androgenic pathways in breast cancer is still in its infancy. Clinical and nonhuman primate studies suggest that androgens inhibit mammary epithelial proliferation and breast growth while conventional estrogen treatment suppresses endogenous androgens. Abundant clinical evidence suggests that androgens normally inhibit mammary epithelial proliferation and breast growth. Suppression of androgens using conventional estrogen treatment may thus enhance estrogenic breast stimulation and possibly breast cancer risk. Addition of testosterone to the usual hormone therapy regimen may diminish the estrogen/progestin increase in breast cancer risk but the impact of this combined use on mammary gland homeostasis still needs evaluation.

Turner syndrome 2008.

BACKGROUND: Fetuses with prenatal diagnoses of 45,X Turner syndrome (TS) and abnormal fetal ultrasounds have poor prognoses for survival, but with modern medical management, those that do survive to birth may have good clinical outcomes. Fetuses with incidental diagnoses of mosaicism for 45,X associated with normal ultrasounds have a high survival rate and may have no or only mild features of TS. CURRENT GUIDELINES: At present, appropriate treatment for girls with TS may include growth-promoting therapy and pubertal induction with the dual aims of optimizing adult height and facilitating psychosocial adjustment. Current recommendations advocate mimicking normal physiology as much as possible, with use of microdose estradiol to initiate puberty. Healthcare providers should play a role in helping girls psychosocially adapt to ovarian failure. We now recognize there is an unacceptably high rate of premature mortality in adults with TS, mainly because of complications from congenital heart disease. Cardiac magnetic resonance imaging is recommended to screen for individuals at high risk for serious complications.

Aortic dilatation and dissection in Turner syndrome.

BACKGROUND: The risk for aortic dissection is increased among relatively young women with Turner syndrome (TS). It is unknown whether aortic dilatation precedes acute aortic dissection in TS and, if so, what specific diameter predicts impending deterioration. METHODS AND RESULTS: Study subjects included 166 adult volunteers with TS (average age, 36.2 years) who were not selected for cardiovascular disease and 26 healthy female control subjects. Ascending and descending aortic diameters were measured by magnetic resonance imaging at the right pulmonary artery. TS women were on average 20 cm shorter, yet average aortic diameters were identical in the 2 groups. Ascending aortic diameters normalized to body surface area (aortic size index) were significantly greater in TS, and approximately 32% of TS women had values greater than the 95th percentile of 2.0 cm/m2. Ascending diameter/descending diameter ratios also were significantly greater in the TS group. During approximately 3 years of follow-up, aortic dissections occurred in 3 women with TS, for an annualized rate of 618 cases/100,000 woman-years. These 3 subjects had ascending aortic diameters of 3.7 to 4.8 cm and aortic size indices > 2.5 cm/m2. CONCLUSIONS: The risk for aortic dissection is greatly increased in young women with TS. Because of their small stature, ascending aortic diameters of < 5 cm may represent significant dilatation; thus, the use of aortic size index is preferred. Individuals with a dilated ascending aorta defined as aortic size index > 2.0 cm/m2 require close cardiovascular surveillance. Those with aortic size index > or = 2.5 cm/m2 are at highest risk for aortic dissection.

Reduced abdominal adiposity and improved glucose tolerance in growth hormone-treated girls with Turner syndrome.

BACKGROUND: Individuals with Turner syndrome (TS) are at increased risk for impaired glucose tolerance and diabetes mellitus. It is unknown whether pharmacological GH treatment commonly used to treat short stature in TS alters this risk. OBJECTIVE: Our objective was to compare adiposity and glucose tolerance in GH-treated vs. untreated girls with TS. METHODS: In a cross sectional study, GH-treated girls with TS (n = 76; age 13.6 +/- 3.7 yr) were compared to girls with TS that never received GH (n = 26; age 13.8 +/- 3.5 yr). Protocol studies took place in the NIH Clinical Research Center from 2001-2006 and included oral glucose tolerance tests, body composition analysis by dual-energy x-ray absorptiometry, and abdominal fat quantification by magnetic resonance imaging. GH was not given during testing. RESULTS: Total body fat (35 +/- 8 vs. 28 +/- 8%, P < 0.0001), sc abdominal fat (183 vs. 100 ml, P = 0.001), and intraabdominal fat (50 vs. 33 ml, P < 0.0001) were significantly greater in untreated girls. Fasting glucose and insulin were similar, but the response to oral glucose was significantly impaired in the untreated group (28 vs. 7% with impaired glucose tolerance, P = 0.006). A specific excess of visceral fat and insulin resistance was apparent only in postpubertal girls that had never received GH. GH-treated girls demonstrated lower adiposity compared with untreated girls for an average of 2 yr after discontinuation of GH. CONCLUSIONS: Abdominal adiposity is significantly lower and glucose tolerance significantly better in GH-treated vs. untreated girls with TS, suggesting that beneficial effects upon body composition and regional fat deposition outweigh transient insulin antagonism associated with GH administration.

Facilitative glucose transporters in articular chondrocytes. Expression, distribution and functional regulation of GLUT isoforms by hypoxia, hypoxia mimetics, growth factors and pro-inflammatory cytokines.

Articular cartilage is a unique and highly specialized avascular connective tissue in which the availability of oxygen and glucose is significantly lower than synovial fluid and plasma. Glucose is an essential source of energy during embryonic growth and fetal development and is vital for mesenchymal cell differentiation, chondrogenesis, and skeletal morphogenesis. Glucose is an important metabolic fuel for differentiated chondrocytes during postnatal development and in adult articular cartilage and is a common structural precursor for the synthesis of extracellular matrix glycosaminoglycans. Glucose metabolism is critical for growth plate chondrocytes which participate in long bone growth. Glucose concentrations in articular cartilage can fluctuate depending on age, physical activity, and endocrine status. Chondrocytes are glycolytic cells and must be able to sense the concentration of oxygen and glucose in the extracellular matrix and respond appropriately by adjusting cellular metabolism. Consequently chondrocytes must have the capacity to survive in an extracellular matrix with limited nutrients and low oxygen tensions. Published data from our laboratories suggest that chondrocytes express multiple isoforms of the GLUT/SLC2A family of glucose/polyol transporters. In other tissues GLUT proteins are expressed in a cell-specific manner, exhibit distinct kinetic properties, and are developmentally regulated. Several GLUTs expressed in chondrocytes are regulated by hypoxia, hypoxia mimetics, metabolic hormones, and proinflammatory cytokines. In this multidisciplinary text we review the molecular and morphological aspects of GLUT expression and function in chondrocytes and their mesenchymal and embryonic stem cell precursors and propose key roles for these proteins in glucose sensing and metabolic regulation in cartilage.