scholarly journals Molecular Mechanisms of Skewed X-Chromosome Inactivation in Female Hemophilia Patients—Lessons from Wide Genome Analyses

2021 ◽  
Vol 22 (16) ◽  
pp. 9074
Author(s):  
Rima Dardik ◽  
Einat Avishai ◽  
Shadan Lalezari ◽  
Assaf A. Barg ◽  
Sarina Levy-Mendelovich ◽  
...  
Keyword(s):  
X Chromosome ◽  
Molecular Mechanisms ◽  
Gene Mutations ◽  
Bioinformatic Analysis ◽  
Pathogenic Mutation ◽  
X Chromosome Inactivation ◽  
Cag Repeat ◽  
Chromosome Inactivation ◽  
Pcr Analysis ◽  
Two Generations

Introduction: Hemophilia A (HA) is an X-linked bleeding disorder caused by factor VIII (FVIII) deficiency or dysfunction due to F8 gene mutations. HA carriers are usually asymptomatic because their FVIII levels correspond to approximately half of the concentration found in healthy individuals. However, in rare cases, a carrier may exhibit symptoms of moderate to severe HA primarily due to skewed inactivation of her non-hemophilic X chromosome. Aim: The aim of the study was to investigate X-chromosome inactivation (XCI) patterns in HA carriers, with special emphasis on three karyotypically normal HA carriers presenting with moderate to severe HA phenotype due to skewed XCI, in an attempt to elucidate the molecular mechanism underlying skewed XCI in these symptomatic HA carriers. The study was based on the hypothesis that the presence of a pathogenic mutation on the non-hemophilic X chromosome is the cause of extreme inactivation of that X chromosome. Methods: XCI patterns were studied by PCR analysis of the CAG repeat region in the HUMARA gene. HA carriers that demonstrated skewed XCI were further studied by whole-exome sequencing (WES) followed by X chromosome-targeted bioinformatic analysis. Results: All three HA carriers presenting with the moderate to severe HA phenotype due to skewed XCI were found to carry pathogenic mutations on their non-hemophilic X chromosomes. Patient 1 was diagnosed with a frameshift mutation in the PGK1 gene that was associated with familial XCI skewing in three generations. Patient 2 was diagnosed with a missense mutation in the SYTL4 gene that was associated with familial XCI skewing in two generations. Patient 3 was diagnosed with a nonsense mutation in the NKAP gene that was associated with familial XCI skewing in two generations. Conclusion: Our results indicate that the main reason for skewed XCI in our female HA patients was negative selection against cells with a disadvantage caused by an additional deleterious mutation on the silenced X chromosome, thus complicating the phenotype of a monogenic X-linked disease. Based on our study, we are currently offering the X inactivation test to symptomatic hemophilia carriers and plan to expand this approach to symptomatic carriers of other X-linked diseases, which can be further used in pregnancy planning.

X Chromosome Inactivation Pattern is not Associated With Interindividual Variations in Thyroid Volume: A Study of Euthyroid Danish Female Twins

2009 ◽  
Vol 12 (5) ◽  
pp. 502-506 ◽  
Author(s):  
Thomas Heiberg Brix ◽  
Pia Skov Hansen ◽  
Finn Noe Bennedbæk ◽  
Steen Joop Bonnema ◽  
Kirsten Ohm Kyvik ◽  
...  
Keyword(s):  
X Chromosome ◽  
Twin Pair ◽  
Receptor Gene ◽  
Thyroid Volume ◽  
X Chromosome Inactivation ◽  
Cag Repeat ◽  
Chromosome Inactivation ◽  
Pcr Analysis ◽  
Autoimmune Thyroid ◽  
The Impact

AbstractAhigher frequency of skewed X chromosome inactivation (XCI) is found in patients with autoimmune thyroid disease (AITD) than in controls. Although goitre is often present in AITD, a recent study failed to show an association between XCI and clinically overt nontoxic goitre. However, the etiology of overt goitre is complex, and the mechanisms influencing thyroid volume may involve fewer factors than the mechanisms underlying overt goitre. In order to examine the impact of XCI on thyroid volume in euthyroid females, we studied whether within cohort (n= 138) and within twin pair (n= 69) differences in XCI are correlated with differences in thyroid volume. XCI was determined by PCR analysis of a polymorphic CAG repeat in the first exon of the androgen receptor gene. Thyroid volume was determined by ultrasound. Neither in the within cohort nor in the within twin pair analysis could we demonstrate a statistically significant association between XCI and thyroid volume: Regression coefficient (β) = 0.023 (95% confidence interval, –0.062–0.108),p= 0.592 and β = 0.038 (–0.080–0.156),p= 0.521, respectively. Controlling for potential confounders such as zygosity, age, TSH, smoking habits and use of oral contraceptives did not change the findings. In conclusion, in a sample of euthyroid Danish female twins, we found no evidence of a relationship between XCI pattern and thyroid volume.

scholarly journals Frequency of somatic MEN1 gene mutations in monoclonal parathyroid tumours of patients with primary hyperparathyroidism

2000 ◽  
pp. 47-54 ◽  
Author(s):  
S Miedlich ◽  
K Krohn ◽  
P Lamesch ◽  
A Muller ◽  
R Paschke
Keyword(s):  
Primary Hyperparathyroidism ◽  
Gene Mutation ◽  
X Chromosome ◽  
Somatic Mutations ◽  
Genetic Defect ◽  
Gene Mutations ◽  
X Chromosome Inactivation ◽  
Chromosome Inactivation ◽  
Men1 Gene ◽  
Parathyroid Tumours

OBJECTIVES: Investigation of small numbers of parathyroid tumours by X-chromosome inactivation analysis suggests that the majority of them are monoclonal lesions most likely caused by a somatic mutation. Somatic mutations in the MEN1 gene located on chromosome 11q13 have recently been identified in 12-17% of solitary parathyroid tumours in patients with sporadic primary hyperparathyroidism, and they may be the precipitating genetic defect leading to monoclonal cell proliferation in these tumours. DESIGN: To determine the prevalence of MEN1 gene mutations in monoclonal parathyroid neoplasias we investigated 33 parathyroid tumours of patients with primary hyperparathyroidism for clonality and mutations in the MEN1 gene. METHODS: X-chromosome inactivation analysis was used to assess the clonal status of the tumours, direct sequencing of the complete coding region was applied to identify mutations in the MEN1 gene. RESULTS: Twenty-eight female patients (26 patients with solitary adenoma, 2 patients with hyperplasia) were informative for the polymorphism of the androgen receptor on the X-chromosome and could be tested for inactivation pattern. Nineteen of twenty-six (73%) solitary adenomas were monoclonal. Somatic mutations in the MEN1 gene were identified in nine cases. Six of them were found in the relatively large second exon of the MEN1 gene (A49D, 193del36, 402delC, 482del22, 547delT, W126X). One was found in exon 5 (904del9), one in exon 7 (Y327X) and one in exon 9 (R415X). Of the monoclonal tumours, 5 out of 19 (26%) harboured a somatic MEN1 gene mutation. CONCLUSIONS: In summary, 73% of the solitary parathyroid adenomas were monoclonal. In 26% of the monoclonal tumours a somatic MEN1 gene mutation has been identified. However, for 74% of monoclonal tumours of the parathyroids the underlying genetic defects are still not known.

scholarly journals X-Chromosome Inactivation and Autosomal Random Monoallelic Expression as “Faux Amis”

2021 ◽  
Vol 9 ◽  
Author(s):  
Vasco M. Barreto ◽  
Nadiya Kubasova ◽  
Clara F. Alves-Pereira ◽  
Anne-Valerie Gendrel
Keyword(s):  
X Chromosome ◽  
Molecular Mechanisms ◽  
Gene Expression Regulation ◽  
Phenotypic Diversity ◽  
X Chromosome Inactivation ◽  
Cellular Level ◽  
Chromosome Inactivation ◽  
Monoallelic Expression ◽  
Distinctive Features ◽  
Faux Amis

X-chromosome inactivation (XCI) and random monoallelic expression of autosomal genes (RMAE) are two paradigms of gene expression regulation where, at the single cell level, genes can be expressed from either the maternal or paternal alleles. X-chromosome inactivation takes place in female marsupial and placental mammals, while RMAE has been described in mammals and also other species. Although the outcome of both processes results in random monoallelic expression and mosaicism at the cellular level, there are many important differences. We provide here a brief sketch of the history behind the discovery of XCI and RMAE. Moreover, we review some of the distinctive features of these two phenomena, with respect to when in development they are established, their roles in dosage compensation and cellular phenotypic diversity, and the molecular mechanisms underlying their initiation and stability.

Genes that Escape X Chromosome Inactivation Modulate Sex Differences in Valve Myofibroblasts

Circulation ◽  
2022 ◽  
Author(s):  
Brian A. Aguado ◽  
Cierra J. Walker ◽  
Joseph C. Grim ◽  
Megan E. Schroeder ◽  
Dilara Batan ◽  
...  
Keyword(s):  
Sex Differences ◽  
X Chromosome ◽  
Molecular Mechanisms ◽  
Smooth Muscle Actin ◽  
X Chromosome Inactivation ◽  
Chromosome Inactivation ◽  
Matrix Stiffness ◽  
Alpha Smooth Muscle Actin ◽  
Male And Female ◽  
Hydrogel Matrix

Background: Aortic valve stenosis (AVS) is a sexually dimorphic disease, with women often presenting with sustained fibrosis and men with more extensive calcification. However, the intracellular molecular mechanisms that drive these clinically important sex differences remain under explored. Methods: Hydrogel scaffolds were designed to recapitulate key aspects of the valve tissue microenvironment and serve as a culture platform for sex-specific valvular interstitial cells (VICs; precursors to pro-fibrotic myofibroblasts). The hydrogel culture system was used to interrogate intracellular pathways involved in sex-dependent VIC-to-myofibroblast activation and deactivation. RNA-sequencing was used to define pathways involved in driving sex-dependent activation. Interventions using small molecule inhibitors and small interfering RNA (siRNA) transfections were performed to provide mechanistic insight into sex-specific cellular responses to microenvironmental cues, including matrix stiffness and exogenously delivered biochemical factors. Results: In both healthy porcine and human aortic valves, female leaflets had higher baseline activation of the myofibroblast marker, alpha-smooth muscle actin (α-SMA), compared to male leaflets. When isolated and cultured, female porcine and human VICs had higher levels of basal α-SMA stress fibers that further increased in response to the hydrogel matrix stiffness, both of which were higher than male VICs. A transcriptomic analysis of male and female porcine VICs revealed Rho-associated protein kinase (RhoA/ROCK) signaling as a potential driver of this sex-dependent myofibroblast activation. Further, we found that genes that escape X-chromosome inactivation, such as BMX and STS (encoding for Bmx non-receptor tyrosine kinase and steroid sulfatase, respectively) partially regulate the elevated female myofibroblast activation via RhoA/ROCK signaling. This finding was confirmed by treating male and female VICs with endothelin-1 and plasminogen activator inhibitor-1, factors that are secreted by endothelial cells and known to drive myofibroblast activation via RhoA/ROCK signaling. Conclusions: Together, in vivo and in vitro results confirm sex-dependencies in myofibroblast activation pathways and implicate genes that escape X-chromosome inactivation in regulating sex differences in myofibroblast activation and subsequent AVS progression. Our results underscore the importance of considering sex as a biological variable to understand the molecular mechanisms of AVS and help guide sex-based precision therapies.

scholarly journals X-Chromosome Inactivation Patterns and Androgen Receptor Functionality Influence Phenotype and Social Characteristics as Well as Pharmacogenetics of Testosterone Therapy in Klinefelter Patients

2004 ◽  
Vol 89 (12) ◽  
pp. 6208-6217 ◽  
Author(s):  
Michael Zitzmann ◽  
Marion Depenbusch ◽  
Jörg Gromoll ◽  
Eberhard Nieschlag
Keyword(s):  
Androgen Receptor ◽  
X Chromosome ◽  
Body Height ◽  
X Chromosome Inactivation ◽  
Cag Repeat ◽  
Chromosome Inactivation ◽  
Social Characteristics ◽  
Social Traits ◽  
Arm Span ◽  
Androgen Effects

Abstract Klinefelter syndrome is characterized by a vast range of phenotypes related to androgen effects. Testosterone (T) acts via the X-linked androgen receptor gene carrying the CAG repeat (CAGn) polymorphism, the length of which is inversely associated with androgen action and might account for the marked variation in phenotypes. In 77 newly diagnosed and untreated Klinefelter patients with a 47,XXY karyotype we assessed phenotype and social traits in relation to X-weighted biallelic CAGn length using X-chromosome inactivation analysis after digestion of leukocyte DNA with methylation-sensitive HpaII. Forty-eight men were hypogonadal and received T substitution therapy; in these, pharmacogenetic effects were investigated. The shorter CAGn allele was preferentially inactive. CAGn length was positively associated with body height. Bone density and the relation of arm span to body height were inversely related to CAGn length. The presence of long CAGn was predictive for gynecomastia and smaller testes, whereas short CAGn were associated with a stable partnership and professions requiring higher standards of education also when corrected for family background. There was a trend for men with longer CAGn to be diagnosed earlier in life. Under T substitution, men with shorter CAGn exhibited a more profound suppression of LH levels, augmented prostate growth, and higher hemoglobin concentrations. A significant genotype-phenotype association exists in Klinefelter patients: androgen effects on appearance and social characteristics are modulated by the androgen receptor CAGn polymorphism. The effects of T substitution are pharmacogenetically modified. This finding is magnified by preferential inactivation of the more functional short CAGn allele.

scholarly journals Clonality Analysis of Hematopoiesis in Essential Thrombocythemia: Advantages of Studying T Lymphocytes and Platelets

Blood ◽  
1997 ◽  
Vol 89 (1) ◽  
pp. 128-134 ◽  
Author(s):  
Nahed El-Kassar ◽  
Gilles Hetet ◽  
Jean Brière ◽  
Bernard Grandchamp
Keyword(s):  
T Lymphocytes ◽  
X Chromosome ◽  
Essential Thrombocythemia ◽  
Hematopoietic Cells ◽  
X Chromosome Inactivation ◽  
Chromosome Inactivation ◽  
Pcr Analysis ◽  
Clonal Hematopoiesis ◽  
Control Tissue ◽  
Clonality Analysis

Abstract Essential thrombocythemia (ET) is a myeloproliferative disorder characterized by a sustained elevation of the platelet count in the absence of other causes of thrombocytosis. ET is difficult to diagnose, and the demonstration of clonal hematopoiesis may be of value. However, clonality analysis of hematopoietic cells based on the study of the X-chromosome inactivation pattern is complicated by the observation that some normal females present skewed lyonization. Moreover, DNA methylation of X-linked genes in hematopoietic cells may differ from that in other tissues. Appropriate controls for skewed lyonization are therefore critical for the study of clonality. We developed two techniques based on X-chromosome inactivation and polymerase chain reaction (PCR) analysis of polymorphisms, to study clonality in ET patients. Reverse transcriptase-PCR analysis of IDS, P55, and G6PD mRNAs was used to examine the different hematopoietic cell lineages including platelets in patients heterozygous for these polymorphisms and analysis of the HUMARA gene methylation pattern permitted us to study clonality in all nucleated cell fractions of the other patients. Using both types of assay and T lymphocytes as a control tissue for lyonization, clonal hematopoiesis was demonstrated in 28 patients. In 14 patients, the granulocytes were polyclonal; among these patients, platelets were monoclonal in 3 cases, polyclonal in 7 cases, and in the remaining 4 cases this fraction could not be studied because the patients were homozygotes for all RNA markers. No conclusion about clonality could be drawn in 6 cases. Polyclonal hematopoiesis was found in all the cases of reactive thrombocytosis. These findings confirm the high frequency of monoclonal hematopoiesis in ET, the utility of studying platelets, and the possibility of using T lymphocytes as a control tissue for X-chromosome inactivation patterns.

scholarly journals A Functional Mutation in HDAC8 Gene as Novel Diagnostic Marker for Cornelia De Lange Syndrome

2018 ◽  
Vol 47 (6) ◽  
pp. 2388-2395 ◽  
Author(s):  
Xueren Gao ◽  
Zhuo Huang ◽  
Yanjie Fan ◽  
Yu Sun ◽  
Huili Liu ◽  
...  
Keyword(s):  
Missense Mutation ◽  
X Chromosome ◽  
Genetic Disorder ◽  
Sodium Dodecyl ◽  
Pathogenic Mutation ◽  
X Chromosome Inactivation ◽  
Chromosome Inactivation ◽  
Cornelia De Lange Syndrome ◽  
Cornelia De Lange

Background/Aims: Cornelia de Lange Syndrome (CdLS) is a rare genetic disorder classically characterized by distinctive facies, growth retardation, intellectual disability, feeding difficulties, and multiple organ system anomalies. Previously, the diagnosis of CdLS was based mainly on identifying the typical phenotype in patients. However, with the advances in clinical molecular genetic diagnostic techniques, more patients, especially patients with milder phenotypes, are being diagnosed from detecting pathogenic mutation. Methods: Pathogenic mutation in a female patient with a milder phenotype was detected using whole-exome sequencing (WES), and was further characterized using bioinformatic analysis and in vitro functional experiments, including X-chromosome inactivation analysis, sodium dodecyl sulfate-polyacrylamide gel electrophoresis, and enzyme activity assay. Results: This patient was found to harbor a novel missense mutation (c.806T>G, p.I269R) in the coding region of the HDAC8 gene, which was predicted to be pathogenic. Compared with other CdLS patients with HDAC8 mutation, the patient lacked typical facies, including synophrys and arched eyebrows. In vitro functional experiments showed the presence of skewed X-chromosome inactivation. Furthermore, the novel mutation decreased the dissolubility and enzymatic activity of HDAC8 protein. Conclusions: The present study identified a novel missense mutation (c.806T>G, p.I269R) in the HDAC8 gene leading to CdLS, which not only provided strong evidence for diagnosis in this present patient, but also expanded the spectrum of pathogenic mutations for CdLS.

STATISTICAL MECHANICS MODELS FOR X-CHROMOSOME INACTIVATION

2010 ◽  
Vol 13 (03) ◽  
pp. 367-376
Author(s):  
ANTONIO SCIALDONE ◽  
MARIO NICODEMI
Keyword(s):  
Statistical Mechanics ◽  
X Chromosome ◽  
Molecular Mechanisms ◽  
X Chromosome Inactivation ◽  
Chromosome Inactivation ◽  
Regulatory Mechanisms ◽  
Random Choice ◽  
X Chromosomes ◽  
Cellular Processes ◽  
Regulatory Processes

We present statistical mechanics models to understand the physical and molecular mechanisms of X-Chromosome Inactivation (XCI), the process whereby a female mammal cell inactivates one of its two X-chromosomes. During XCI, X-chromosomes undergo a series of complex regulatory processes. At the beginning of XCI, the X's recognize and pair, then only one X which is randomly chosen is inactivated. Afterwards, the two X's move to different positions in the cell nucleus according to their different status (active/silenced). Our models illustrate about the still mysterious physical bases underlying all these regulatory steps, i.e., X-chromosome pairing, random choice of inactive X, and "shuttling" of the X's to their post-XCI locations. Our models are based on general and robust thermodynamic roots, and their validity can go beyond XCI, to explain analogous regulatory mechanisms in a variety of cellular processes.

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