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Juchniewicz P, Kloska A, Portalska K, Jakóbkiewicz-Banecka J, Węgrzyn G, Liss J, Głodek P, Tukaj S, Piotrowska E. X-chromosome inactivation patterns depend on age and tissue but not conception method in humans. Chromosome Res 2023; 31:4. [PMID: 36695960 PMCID: PMC9877087 DOI: 10.1007/s10577-023-09717-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2022] [Revised: 11/27/2022] [Accepted: 12/06/2022] [Indexed: 01/26/2023]
Abstract
Female somatic X-chromosome inactivation (XCI) balances the X-linked transcriptional dosages between the sexes, randomly silencing the maternal or paternal X chromosome in each cell of 46,XX females. Skewed XCI toward one parental X has been observed in association with ageing and in some female carriers of X-linked diseases. To address the problem of non-random XCI, we quantified the XCI skew in different biological samples of naturally conceived females of different age groups and girls conceived after in vitro fertilization (IVF). Generally, XCI skew differed between saliva, blood, and buccal swabs, while saliva and blood had the most similar XCI patterns in individual females. XCI skew increased with age in saliva, but not in other tissues. We showed no significant differences in the XCI patterns in tissues of naturally conceived and IVF females. The gene expression profile of the placenta and umbilical cord blood was determined depending on the XCI pattern. The increased XCI skewing in the placental tissue was associated with the differential expression of several genes out of 40 considered herein. Notably, skewed XCI patterns (> 80:20) were identified with significantly increased expression levels of four genes: CD44, KDM6A, PHLDA2, and ZRSR2. The differences in gene expression patterns between samples with random and non-random XCI may shed new light on factors contributing to the XCI pattern outcome and indicate new paths in future research on the phenomenon of XCI skewing.
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Affiliation(s)
- Patrycja Juchniewicz
- Department of Medical Biology and Genetics, Faculty of Biology, University of Gdańsk, Wita Stwosza 59, 80-308 Gdańsk, Poland
| | - Anna Kloska
- Department of Medical Biology and Genetics, Faculty of Biology, University of Gdańsk, Wita Stwosza 59, 80-308 Gdańsk, Poland
| | - Karolina Portalska
- Department of Molecular Biology, Faculty of Biology, University of Gdańsk, Wita Stwosza 59, 80-308 Gdańsk, Poland
| | - Joanna Jakóbkiewicz-Banecka
- Department of Medical Biology and Genetics, Faculty of Biology, University of Gdańsk, Wita Stwosza 59, 80-308 Gdańsk, Poland
| | - Grzegorz Węgrzyn
- Department of Molecular Biology, Faculty of Biology, University of Gdańsk, Wita Stwosza 59, 80-308 Gdańsk, Poland
| | - Joanna Liss
- Department of Medical Biology and Genetics, Faculty of Biology, University of Gdańsk, Wita Stwosza 59, 80-308 Gdańsk, Poland ,Research and Development Center, INVICTA, Sopot, Poland
| | - Piotr Głodek
- Research and Development Center, INVICTA, Sopot, Poland
| | - Stefan Tukaj
- Department of Molecular Biology, Faculty of Biology, University of Gdańsk, Wita Stwosza 59, 80-308 Gdańsk, Poland
| | - Ewa Piotrowska
- Department of Molecular Biology, Faculty of Biology, University of Gdańsk, Wita Stwosza 59, 80-308 Gdańsk, Poland
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2
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Skewed X-Chromosome Inactivation and Parental Gonadal Mosaicism Are Implicated in X-Linked Recessive Female Hemophilia Patients. Diagnostics (Basel) 2022; 12:diagnostics12102267. [PMID: 36291957 PMCID: PMC9600608 DOI: 10.3390/diagnostics12102267] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2022] [Revised: 09/09/2022] [Accepted: 09/17/2022] [Indexed: 11/16/2022] Open
Abstract
Background: Hemophilia A (HA) and B (HB) are X-linked recessive disorders that mainly affect males born from a mother carrier. Females are rarely affected but a number of mechanisms have been suggested in symptomatic females, such as skewed X-chromosome inactivation (XCI), chromosomal rearrangements, and hermaphrodites. Different methodologies are required to elucidate the underlying causes of such diseases in female patients. Methods: Three families with female hemophilia patients, including two HA and one HB, were enrolled for genetic analyses. Cytogenetics, molecular examinations on F8 and F9 genes, XCI assay, and linkage analysis were performed. Results: All three female patients are demonstrated to be heterozygous for an F8, or F9 mutation: one patient is inherited from her unaffected mother and the other two are sporadic cases. All three patients exhibit skewed XCI. The inherited patient is found to be unmethylated in the maternal X chromosome, which increases the potential for the expression of the mutant allele. The two sporadic cases are hypomethylated or unmethylated in the paternal X chromosome, suggesting that paternal gonadal mosaicism may exist in these families. Conclusions: In addition to screening for coagulation function, different genetic analyses are mandatory to explore the nature of mechanisms responsible for the X-linked recessive disorders in female patients as shown in this study. Our results confirm that skewed XCI is responsible for hemophilia in heterozygous female patients. Likewise, our results implicate that parental gonadal mosaicism, followed by skewed XCI, contributes to hemophilia in “sporadic” female patients.
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Salvetti AP, Nanda A, MacLaren RE. RPGR-Related X-Linked Retinitis Pigmentosa Carriers with a Severe "Male Pattern". Ophthalmologica 2020; 244:60-67. [PMID: 32434206 DOI: 10.1159/000503687] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2019] [Accepted: 09/25/2019] [Indexed: 11/19/2022]
Abstract
BACKGROUND X-linked retinitis pigmentosa (XLRP) due to mutations in the RPGR gene is a very severe form of RP, resulting in rapid disease progression and retinal dysfunction. Female carriers do not usually report symptoms. However, it has reported that carriers of XLRP can have a significant visual and retinal impairment. OBJECTIVES To report a detailed description of 3 cases of severely affected females who presented with a "male" phenotype and have posed challenges at diagnosis, due to the apparent autosomal dominant family history. METHOD Autofluorescence imaging (AF), colour imaging and optical coherence tomography (OCT) were performed. Confirmation of the genetic mutation was obtained by Sanger genetic sequencing. In 1 patient an X-inactivation analysis was performed to detect the X-inactivation ratio, as the percentage of cells tested in which each allele is active. RESULTS All the patients started suffering from night blindness in early childhood. Colour, fundus AF and OCT images showed the typical pattern of degeneration reported in men. One patient underwent retina implant surgery due to the severe atrophy. CONCLUSIONS This is a small selection of females with a severe phenotype that do not differ from the typical male phenotype. In our opinion gene therapy surgery should be warranted in this scenario.
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Affiliation(s)
- Anna Paola Salvetti
- Oxford Eye Hospital, Oxford University Hospitals NHS Foundation Trust, and Nuffield Laboratory of Ophthalmology, Department of Clinical Neurosciences, University of Oxford, Oxford, United Kingdom
| | - Anika Nanda
- Oxford Eye Hospital, Oxford University Hospitals NHS Foundation Trust, and Nuffield Laboratory of Ophthalmology, Department of Clinical Neurosciences, University of Oxford, Oxford, United Kingdom
| | - Robert E MacLaren
- Oxford Eye Hospital, Oxford University Hospitals NHS Foundation Trust, and Nuffield Laboratory of Ophthalmology, Department of Clinical Neurosciences, University of Oxford, Oxford, United Kingdom,
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4
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Cho RY, Peñaherrera MS, Du Souich C, Huang L, Mwenifumbo J, Nelson TN, Elliott AM, Adam S, Eydoux P, Yang GX, Chijiwa C, Van Allen MI, Friedman JM, Robinson WP, Lehman A. Renpenning syndrome in a female. Am J Med Genet A 2019; 182:498-503. [PMID: 31840929 DOI: 10.1002/ajmg.a.61451] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2019] [Revised: 10/26/2019] [Accepted: 10/29/2019] [Indexed: 01/03/2023]
Abstract
Renpenning syndrome (OMIM: 309500) is a rare X-linked disorder that causes intellectual disability, microcephaly, short stature, a variety of eye anomalies, and characteristic craniofacial features. This condition results from pathogenic variation of PQBP1, a polyglutamine-binding protein involved in transcription and pre-mRNA splicing. Renpenning syndrome has only been reported in affected males. Carrier females do not usually have clinical features, and in reported families with Renpenning syndrome, most female carriers exhibit favorable skewing of X-chromosome inactivation. We describe a female with syndromic features typical of Renpenning syndrome. She was identified by exome sequencing to have a de novo heterozygous c.459_462delAGAG mutation in PQBP1 (Xp11.23), affecting the AG hexamer in exon 4, which is the most common causative mutation in this syndrome. Streaky hypopigmentation of the skin was observed, supporting a hypothesized presence of an actively expressed, PQBP1 mutation-bearing X-chromosome in some cells. X-inactivation studies on peripheral blood cells demonstrated complete skewing in both the proband and her mother with preferential inactivation of the maternal X chromosome in the child. We demonstrated expression of the PQBP1 mutant transcript in leukocytes of the affected girl. Therefore, it is highly likely that the PQBP1 mutation arose from the paternal X chromosome.
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Affiliation(s)
- Raymond Y Cho
- Department of Medical Genetics, University of British Columbia, Vancouver, British Columbia, Canada
| | - Maria S Peñaherrera
- Department of Medical Genetics, University of British Columbia, Vancouver, British Columbia, Canada.,BC Children's Hospital Research Institute, Vancouver, British Columbia, Canada
| | - Christele Du Souich
- Department of Medical Genetics, University of British Columbia, Vancouver, British Columbia, Canada.,BC Children's Hospital Research Institute, Vancouver, British Columbia, Canada
| | - Lijia Huang
- Department of Pathology and Laboratory Medicine, University of British Columbia, Vancouver, British Columbia, Canada
| | - Jill Mwenifumbo
- Department of Medical Genetics, University of British Columbia, Vancouver, British Columbia, Canada
| | - Tanya N Nelson
- Department of Medical Genetics, University of British Columbia, Vancouver, British Columbia, Canada.,Department of Pathology and Laboratory Medicine, University of British Columbia, Vancouver, British Columbia, Canada.,BC Children's Hospital Research Institute, Vancouver, British Columbia, Canada
| | - Alison M Elliott
- Department of Medical Genetics, University of British Columbia, Vancouver, British Columbia, Canada
| | - Shelin Adam
- Department of Medical Genetics, University of British Columbia, Vancouver, British Columbia, Canada
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- Department of Medical Genetics, University of British Columbia, Vancouver, British Columbia, Canada
| | - Patrice Eydoux
- Department of Medical Genetics, University of British Columbia, Vancouver, British Columbia, Canada.,Department of Pathology and Laboratory Medicine, University of British Columbia, Vancouver, British Columbia, Canada.,BC Children's Hospital Research Institute, Vancouver, British Columbia, Canada
| | - Gui X Yang
- Department of Medical Genetics, University of British Columbia, Vancouver, British Columbia, Canada
| | - Chieko Chijiwa
- Department of Medical Genetics, University of British Columbia, Vancouver, British Columbia, Canada
| | - Margot I Van Allen
- Department of Medical Genetics, University of British Columbia, Vancouver, British Columbia, Canada.,BC Children's Hospital Research Institute, Vancouver, British Columbia, Canada
| | - Jan M Friedman
- Department of Medical Genetics, University of British Columbia, Vancouver, British Columbia, Canada.,BC Children's Hospital Research Institute, Vancouver, British Columbia, Canada
| | - Wendy P Robinson
- Department of Medical Genetics, University of British Columbia, Vancouver, British Columbia, Canada.,BC Children's Hospital Research Institute, Vancouver, British Columbia, Canada
| | - Anna Lehman
- Department of Medical Genetics, University of British Columbia, Vancouver, British Columbia, Canada.,BC Children's Hospital Research Institute, Vancouver, British Columbia, Canada
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5
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Ouyang P, Li Y, Zhang F, Zhu C, Zou B, Le J, Zhang L. A frameshift mutation in the CHM gene causes choroideremia with acute angle‑closure glaucoma. Mol Med Rep 2018; 17:7918-7924. [PMID: 29620233 DOI: 10.3892/mmr.2018.8851] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2017] [Accepted: 03/22/2018] [Indexed: 11/06/2022] Open
Abstract
Choroideremia is an X‑linked recessive chorioretinal degenerative disease that is characterized by progressive centripetal loss of the photoreceptor, retinal pigment epithelium (RPE), and choriocapillaris layers. The CHM gene [choroideremia (Rab escort protein 1)] has been identified as the pathogenic gene in choroideremia. The aim of the present study was to describe the clinical and genetic characteristics of a family with choroideremia family. In the present study, a family with choroideremia presenting with serious chorioretinal atrophy and pigment proliferation, shallow anterior chambers, angle closure and high intraocular pressure (IOP) were recruited. The affected family members underwent a complete ophthalmologic examination. DNA samples obtained from the proband II:1 and the patient II:2 were used for targeted exome sequencing of the CHM gene. PCR amplification and Sanger sequencing were used to validate the variations exhibited in family members and controls. A novel frameshift mutation c.280delA (p.Thr94LeufsTer32), in CHM was identified in the male proband, the normal carrier I:2 and the phenotyped carrier II:2, which was absent in the normal individual II:3 as well as in 200 normal controls. Comparing the amino acid sequences of CHM between multiple species through Clustal Omega indicated conserved amino acids in these mutant sites. Additionally, an X‑chromosome inactivation (XCI) assay was performed in the female carriers in the family, in which DNA of the abnormal carrier II:2 and normal carrier I:2 showed a random XCI pattern. To conclude, the present findings strongly indicate that the c.280delA mutation is a disease‑causing mutation in our choroideremia pedigree with acute angle‑closure glaucoma.
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Affiliation(s)
- Pingbo Ouyang
- School of Information Science and Engineering, Central South University, Changsha, Hunan 410083, P.R. China
| | - Yun Li
- Department of Ophthalmology, The Second Xiangya Hospital, Central South University, Changsha, Hunan 410011, P.R. China
| | - Feng Zhang
- Department of Ophthalmology, The Second Xiangya Hospital, Central South University, Changsha, Hunan 410011, P.R. China
| | - Chengzhang Zhu
- School of Information Science and Engineering, Central South University, Changsha, Hunan 410083, P.R. China
| | - Beiji Zou
- School of Information Science and Engineering, Central South University, Changsha, Hunan 410083, P.R. China
| | - Jianlan Le
- Department of Ophthalmology, The Second Xiangya Hospital, Central South University, Changsha, Hunan 410011, P.R. China
| | - Lusi Zhang
- Department of Ophthalmology, The Second Xiangya Hospital, Central South University, Changsha, Hunan 410011, P.R. China
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6
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Yang C, Yu Z, Zhang W, Cao L, Ouyang W, Hu F, Zhang P, Bai X, Ruan C. A novel missense mutation, p.Phe360Cys, in FIX gene results in haemophilia B in a female patient with skewed X-inactivation. Haemophilia 2018; 24:e68-e70. [PMID: 29405493 DOI: 10.1111/hae.13423] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 12/20/2017] [Indexed: 11/30/2022]
Affiliation(s)
- C. Yang
- Jiangsu Institute of Hematology; Key Laboratory of Thrombosis and Hemostasis/Ministry of Health; The First Affiliated Hospital of Soochow University; Suzhou China
- Collaborative Innovation Center of Hematology; Soochow University; Suzhou China
| | - Z. Yu
- Jiangsu Institute of Hematology; Key Laboratory of Thrombosis and Hemostasis/Ministry of Health; The First Affiliated Hospital of Soochow University; Suzhou China
- Collaborative Innovation Center of Hematology; Soochow University; Suzhou China
| | - W. Zhang
- Jiangsu Institute of Hematology; Key Laboratory of Thrombosis and Hemostasis/Ministry of Health; The First Affiliated Hospital of Soochow University; Suzhou China
- Collaborative Innovation Center of Hematology; Soochow University; Suzhou China
| | - L. Cao
- Jiangsu Institute of Hematology; Key Laboratory of Thrombosis and Hemostasis/Ministry of Health; The First Affiliated Hospital of Soochow University; Suzhou China
- Collaborative Innovation Center of Hematology; Soochow University; Suzhou China
| | - W. Ouyang
- Jiangsu Institute of Hematology; Key Laboratory of Thrombosis and Hemostasis/Ministry of Health; The First Affiliated Hospital of Soochow University; Suzhou China
- Collaborative Innovation Center of Hematology; Soochow University; Suzhou China
| | - F. Hu
- Jiangsu Institute of Hematology; Key Laboratory of Thrombosis and Hemostasis/Ministry of Health; The First Affiliated Hospital of Soochow University; Suzhou China
- Collaborative Innovation Center of Hematology; Soochow University; Suzhou China
| | - P. Zhang
- Jiangsu Institute of Hematology; Key Laboratory of Thrombosis and Hemostasis/Ministry of Health; The First Affiliated Hospital of Soochow University; Suzhou China
- Collaborative Innovation Center of Hematology; Soochow University; Suzhou China
| | - X. Bai
- Jiangsu Institute of Hematology; Key Laboratory of Thrombosis and Hemostasis/Ministry of Health; The First Affiliated Hospital of Soochow University; Suzhou China
- Collaborative Innovation Center of Hematology; Soochow University; Suzhou China
| | - C. Ruan
- Jiangsu Institute of Hematology; Key Laboratory of Thrombosis and Hemostasis/Ministry of Health; The First Affiliated Hospital of Soochow University; Suzhou China
- Collaborative Innovation Center of Hematology; Soochow University; Suzhou China
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7
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Peng H, Xu X, Zhang L, Zhang X, Peng H, Zheng Y, Luo S, Guo H, Xia K, Li J, Yao H, Hu Z. GLA variation p.E66Q identified as the genetic etiology of Fabry disease using exome sequencing. Gene 2015; 575:363-7. [PMID: 26456105 DOI: 10.1016/j.gene.2015.09.088] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2015] [Revised: 09/04/2015] [Accepted: 09/09/2015] [Indexed: 12/01/2022]
Abstract
Fabry disease (FD) was an X-linked lysosomal storage disorder resulting from a deficiency in glycosphingolipid catabolism caused by mutations in the α-galactosidase A gene GLA. Variant FD patients did not present with classical symptoms during childhood and were undiagnosed or misdiagnosed with other kidney diseases, such as chronic glomerulonephritis (CGN). In this study, we utilized exome sequencing and Sanger sequencing identified the variation p.E66Q of GLA completely co-segregated with the disease phenotype in a Chinese family, which previously been diagnosed as possible CGN. Female patients exhibited preferential X-chromosome inactivation (XCI) of the normal p.E66 allele, as indicated by XCI analysis. By measuring α-Gal A activity, we found that male patients in the pedigree had just little enzymatic activity while female patients had residual enzymatic activity. These patients were diagnosed with renal variant FD in subsequent clinical review. Our results directly implicated the GLA mutation p.E66Q as the genetic etiology of the Chinese renal variant FD pedigree.
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Affiliation(s)
- Hao Peng
- The State Key Laboratory of Medical Genetics and School of Life Science, Central South University, Changsha, Hunan, China
| | - Xiaojuan Xu
- The Reproductive Medicine Hospital of the First Hospital of Lanzhou University, Lanzhou, Gansu, China.
| | - Lusi Zhang
- Department of Ophthalmology, Second Xiangya Hospital, Central South University, Changsha, Hunan, China
| | - Xuehong Zhang
- The Reproductive Medicine Hospital of the First Hospital of Lanzhou University, Lanzhou, Gansu, China
| | - Hexiang Peng
- The State Key Laboratory of Medical Genetics and School of Life Science, Central South University, Changsha, Hunan, China
| | - Yu Zheng
- The State Key Laboratory of Medical Genetics and School of Life Science, Central South University, Changsha, Hunan, China
| | - Sanchuan Luo
- The State Key Laboratory of Medical Genetics and School of Life Science, Central South University, Changsha, Hunan, China
| | - Hui Guo
- The State Key Laboratory of Medical Genetics and School of Life Science, Central South University, Changsha, Hunan, China
| | - Kun Xia
- The State Key Laboratory of Medical Genetics and School of Life Science, Central South University, Changsha, Hunan, China
| | - Jiada Li
- The State Key Laboratory of Medical Genetics and School of Life Science, Central South University, Changsha, Hunan, China
| | - Hongliang Yao
- Department of General Surgery, Second Xiangya Hospital, Central South University, Changsha, Hunan, China
| | - Zhengmao Hu
- The State Key Laboratory of Medical Genetics and School of Life Science, Central South University, Changsha, Hunan, China.
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8
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Tarailo-Graovac M, Sinclair G, Stockler-Ipsiroglu S, Van Allen M, Rozmus J, Shyr C, Biancheri R, Oh T, Sayson B, Lafek M, Ross CJ, Robinson WP, Wasserman WW, Rossi A, van Karnebeek CDM. The genotypic and phenotypic spectrum of PIGA deficiency. Orphanet J Rare Dis 2015; 10:23. [PMID: 25885527 PMCID: PMC4348372 DOI: 10.1186/s13023-015-0243-8] [Citation(s) in RCA: 60] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2014] [Accepted: 02/18/2015] [Indexed: 01/09/2023] Open
Abstract
BACKGROUND Phosphatidylinositol glycan biosynthesis class A protein (PIGA) is one of the enzymes involved in the biosynthesis of glycosylphosphatidylinositol (GPI) anchor proteins, which function as enzymes, adhesion molecules, complement regulators and co-receptors in signal transduction pathways. Until recently, only somatic PIGA mutations had been reported in patients with paroxysmal nocturnal hemoglobinuria (PNH), while germline mutations had not been observed, and were suspected to result in lethality. However, in just two years, whole exome sequencing (WES) analyses have identified germline PIGA mutations in male patients with XLIDD (X-linked intellectual developmental disorder) with a wide spectrum of clinical presentations. METHODS AND RESULTS Here, we report on a new missense PIGA germline mutation [g.15342986C>T (p.S330N)] identified via WES followed by Sanger sequencing, in a Chinese male infant presenting with developmental arrest, infantile spasms, a pattern of lesion distribution on brain MRI resembling that typical of maple syrup urine disease, contractures, dysmorphism, elevated alkaline phosphatase, mixed hearing loss (a combination of conductive and sensorineural), liver dysfunction, mitochondrial complex I and V deficiency, and therapy-responsive dyslipidemia with confirmed lipoprotein lipase deficiency. X-inactivation studies showed skewing in the clinically unaffected carrier mother, and CD109 surface expression in patient fibroblasts was 57% of that measured in controls; together these data support pathogenicity of this mutation. Furthermore, we review all reported germline PIGA mutations (1 nonsense, 1 frameshift, 1 in-frame deletion, five missense) in 8 unrelated families. CONCLUSIONS Our case further delineates the heterogeneous phenotype of this condition for which we propose the term 'PIGA deficiency'. While the phenotypic spectrum is wide, it could be classified into two types (severe and less severe) with shared hallmarks of infantile spasms with hypsarrhythmia on EEG and profound XLIDD. In severe PIGA deficiency, as described in our patient, patients also present with dysmorphic facial features, multiple CNS abnormalities, such as thin corpus callosum and delayed myelination, as well as hypotonia and elevated alkaline phosphatase along with liver, renal, and cardiac involvement; its course is often fatal. The less severe form of PIGA deficiency does not involve facial dysmorphism and multiple CNS abnormalities; instead, patients present with milder IDD, treatable seizures and generally a longer lifespan.
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Affiliation(s)
- Maja Tarailo-Graovac
- Centre for Molecular Medicine and Therapeutics, Vancouver, Canada. .,Department of Medical Genetics, University of British Columbia, Vancouver, Canada. .,Treatable Intellectual Disability Endeavour in British Columbia, Vancouver, Canada.
| | - Graham Sinclair
- Treatable Intellectual Disability Endeavour in British Columbia, Vancouver, Canada. .,Division of Biochemical Diseases, Department of Pediatrics, BC Children's Hospital, University of British Columbia, Vancouver, Canada. .,Biochemical Genetics Laboratory, Department of Pathology, BC Children's Hospital, University of British Columbia, Vancouver, Canada.
| | - Sylvia Stockler-Ipsiroglu
- Treatable Intellectual Disability Endeavour in British Columbia, Vancouver, Canada. .,Division of Biochemical Diseases, Department of Pediatrics, BC Children's Hospital, University of British Columbia, Vancouver, Canada. .,Child & Family Research Institute, Vancouver, BC, Canada.
| | - Margot Van Allen
- Department of Medical Genetics, University of British Columbia, Vancouver, Canada. .,Child & Family Research Institute, Vancouver, BC, Canada.
| | - Jacob Rozmus
- Division of Hematology, Oncology & BMT, Department of Pediatrics, BC Children's Hospital, University of British Columbia, Vancouver, Canada. .,Child & Family Research Institute, Vancouver, BC, Canada.
| | - Casper Shyr
- Centre for Molecular Medicine and Therapeutics, Vancouver, Canada. .,Department of Medical Genetics, University of British Columbia, Vancouver, Canada. .,Treatable Intellectual Disability Endeavour in British Columbia, Vancouver, Canada.
| | - Roberta Biancheri
- Department of Paediatric Neurology, Children's Hospital Oxford, John Radcliffe Hospital, Oxford, UK.
| | - Tracey Oh
- Department of Medical Genetics, University of British Columbia, Vancouver, Canada. .,Child & Family Research Institute, Vancouver, BC, Canada.
| | - Bryan Sayson
- Treatable Intellectual Disability Endeavour in British Columbia, Vancouver, Canada. .,Division of Biochemical Diseases, Department of Pediatrics, BC Children's Hospital, University of British Columbia, Vancouver, Canada.
| | - Mirafe Lafek
- Treatable Intellectual Disability Endeavour in British Columbia, Vancouver, Canada. .,Division of Biochemical Diseases, Department of Pediatrics, BC Children's Hospital, University of British Columbia, Vancouver, Canada.
| | - Colin J Ross
- Centre for Molecular Medicine and Therapeutics, Vancouver, Canada. .,Department of Medical Genetics, University of British Columbia, Vancouver, Canada. .,Treatable Intellectual Disability Endeavour in British Columbia, Vancouver, Canada. .,Child & Family Research Institute, Vancouver, BC, Canada.
| | - Wendy P Robinson
- Department of Medical Genetics, University of British Columbia, Vancouver, Canada. .,Child & Family Research Institute, Vancouver, BC, Canada.
| | - Wyeth W Wasserman
- Centre for Molecular Medicine and Therapeutics, Vancouver, Canada. .,Department of Medical Genetics, University of British Columbia, Vancouver, Canada. .,Treatable Intellectual Disability Endeavour in British Columbia, Vancouver, Canada. .,Child & Family Research Institute, Vancouver, BC, Canada.
| | - Andrea Rossi
- Department of Neuroradiology, Istituto Giannina Gaslini, Via Gerolamo Gaslini 5, I-16147, Genoa, Italy.
| | - Clara D M van Karnebeek
- Centre for Molecular Medicine and Therapeutics, Vancouver, Canada. .,Treatable Intellectual Disability Endeavour in British Columbia, Vancouver, Canada. .,Division of Biochemical Diseases, Department of Pediatrics, BC Children's Hospital, University of British Columbia, Vancouver, Canada. .,Child & Family Research Institute, Vancouver, BC, Canada.
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9
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Brancaleoni V, Balwani M, Granata F, Graziadei G, Missineo P, Fiorentino V, Fustinoni S, Cappellini MD, Naik H, Desnick RJ, Di Pierro E. X-chromosomal inactivation directly influences the phenotypic manifestation of X-linked protoporphyria. Clin Genet 2015; 89:20-6. [PMID: 25615817 DOI: 10.1111/cge.12562] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2014] [Revised: 01/09/2015] [Accepted: 01/20/2015] [Indexed: 11/29/2022]
Abstract
X-linked protoporphyria (XLP), a rare erythropoietic porphyria, results from terminal exon gain-of-function mutations in the ALAS2 gene causing increased ALAS2 activity and markedly increased erythrocyte protoporphyrin levels. Patients present with severe cutaneous photosensitivity and may develop liver dysfunction. XLP was originally reported as X-linked dominant with 100% penetrance in males and females. We characterized 11 heterozygous females from six unrelated XLP families and show markedly varying phenotypic and biochemical heterogeneity, reflecting the degree of X-chromosomal inactivation of the mutant gene. ALAS2 sequencing identified the specific mutation and confirmed heterozygosity among the females. Clinical history, plasma and erythrocyte protoporphyrin levels were determined. Methylation assays of the androgen receptor and zinc-finger MYM type 3 short tandem repeat polymorphisms estimated each heterozygotes X-chromosomal inactivation pattern. Heterozygotes with equal or increased skewing, favoring expression of the wild-type allele had no clinical symptoms and only slightly increased erythrocyte protoporphyrin concentrations and/or frequency of protoporphyrin-containing peripheral blood fluorocytes. When the wild-type allele was preferentially inactivated, heterozygous females manifested the disease phenotype and had both higher erythrocyte protoporphyrin levels and circulating fluorocytes. These findings confirm that the previous dominant classification of XLP is inappropriate and genetically misleading, as the disorder is more appropriately designated XLP.
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Affiliation(s)
- V Brancaleoni
- Fondazione IRCCS "Cà-Granda" Ospedale Maggiore Policlinico, U.O. di Medicina Interna, Milano, Italy
| | - M Balwani
- Department of Genetics and Genomic Sciences, Icahn School of Medicine at Mount Sinai, New York, NY, USA
| | - F Granata
- Fondazione IRCCS "Cà-Granda" Ospedale Maggiore Policlinico, U.O. di Medicina Interna, Milano, Italy
| | - G Graziadei
- Fondazione IRCCS "Cà-Granda" Ospedale Maggiore Policlinico, U.O. di Medicina Interna, Milano, Italy
| | - P Missineo
- Dipartimento di Scienze Cliniche e di Comunità, Università degli Studi di Milano, Milano, Italy
| | - V Fiorentino
- Fondazione IRCCS "Cà-Granda" Ospedale Maggiore Policlinico, U.O. di Medicina Interna, Milano, Italy
| | - S Fustinoni
- Dipartimento di Scienze Cliniche e di Comunità, Università degli Studi di Milano, Milano, Italy
| | - M D Cappellini
- Fondazione IRCCS "Cà-Granda" Ospedale Maggiore Policlinico, U.O. di Medicina Interna, Milano, Italy.,Dipartimento di Scienze Cliniche e di Comunità, Università degli Studi di Milano, Milano, Italy
| | - H Naik
- Department of Genetics and Genomic Sciences, Icahn School of Medicine at Mount Sinai, New York, NY, USA
| | - R J Desnick
- Department of Genetics and Genomic Sciences, Icahn School of Medicine at Mount Sinai, New York, NY, USA
| | - E Di Pierro
- Fondazione IRCCS "Cà-Granda" Ospedale Maggiore Policlinico, U.O. di Medicina Interna, Milano, Italy
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Musalkova D, Minks J, Storkanova G, Dvorakova L, Hrebicek M. Identification of novel informative loci for DNA-based X-inactivation analysis. Blood Cells Mol Dis 2014; 54:210-6. [PMID: 25455112 DOI: 10.1016/j.bcmd.2014.10.001] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Revised: 02/23/2014] [Accepted: 04/23/2014] [Indexed: 01/19/2023]
Abstract
The HUMARA assay, the most common method for evaluation of X-inactivation skewing in blood cells, has been reported to be usable in only about 80% of females, emphasizing the need for alternative methods for testing of HUMARA-uninformative individuals. We conducted an in silico search for potentially polymorphic tri-to-hexanucleotide repeats in the proximity of CpG islands located in 5' regions of X-chromosome genes to design five candidate assays (numbered I, II, III, IV, and V) combining methylation-specific restriction digest with PCR amplification in a manner similar to the HUMARA assay. The results obtained by these assays in 100 healthy females were compared to X-inactivation skewing measured by the AR-MSP method which is based on methylation-specific PCR amplification of the first exon of the AR gene. On the basis of statistical evidence, three of the novel assays (II, IV, and V), which were informative in 18%, 61%, and 55% of females in the cohort, respectively, may be used as alternatives or conjointly with the HUMARA assay to improve its reliability. The three new assays were combined with the HUMARA assay into a novel X-inactivation test leading to the increase of informative females in the cohort from 67% to 96%.
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Affiliation(s)
- Dita Musalkova
- Institute of Inherited Metabolic Disorders, First Faculty of Medicine, Charles University in Prague and General University Hospital in Prague, Prague, Czech Republic
| | - Jakub Minks
- Institute of Inherited Metabolic Disorders, First Faculty of Medicine, Charles University in Prague and General University Hospital in Prague, Prague, Czech Republic
| | - Gabriela Storkanova
- Institute of Inherited Metabolic Disorders, First Faculty of Medicine, Charles University in Prague and General University Hospital in Prague, Prague, Czech Republic
| | - Lenka Dvorakova
- Institute of Inherited Metabolic Disorders, First Faculty of Medicine, Charles University in Prague and General University Hospital in Prague, Prague, Czech Republic
| | - Martin Hrebicek
- Institute of Inherited Metabolic Disorders, First Faculty of Medicine, Charles University in Prague and General University Hospital in Prague, Prague, Czech Republic.
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11
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Di Pierro E, Russo R, Karakas Z, Brancaleoni V, Gambale A, Kurt I, Winter SS, Granata F, Czuchlewski DR, Langella C, Iolascon A, Cappellini MD. Congenital erythropoietic porphyria linked to GATA1-R216W mutation: challenges for diagnosis. Eur J Haematol 2014; 94:491-7. [DOI: 10.1111/ejh.12452] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/17/2014] [Indexed: 02/02/2023]
Affiliation(s)
- Elena Di Pierro
- Fondazione IRCCS “Cà-Granda” Ospedale Maggiore Policlinico; U.O. di Medicina Interna; Milan Italy
| | - Roberta Russo
- Dipartimento di Medicina Molecolare e Biotecnologie Mediche; Università degli Studi di Napoli “Federico II”; Naples Italy
- CEINGE - Biotecnologie Avanzate; Naples Italy
| | - Zeynep Karakas
- Division of Hematology/Oncology; Department of Pediatrics; Istanbul Medical Faculty; Istanbul University; Istanbul Turkey
| | - Valentina Brancaleoni
- Fondazione IRCCS “Cà-Granda” Ospedale Maggiore Policlinico; U.O. di Medicina Interna; Milan Italy
| | - Antonella Gambale
- Dipartimento di Medicina Molecolare e Biotecnologie Mediche; Università degli Studi di Napoli “Federico II”; Naples Italy
- CEINGE - Biotecnologie Avanzate; Naples Italy
| | - Ismail Kurt
- Department of Biochemistry and Clinical Biochemistry - Laboratory of Porphiria; Gulhane Military Academy of Medicine; Ankara Turkey
| | - S. Stuart Winter
- Department of Pediatrics; University of New Mexico; Albuquerque NM USA
| | - Francesca Granata
- Fondazione IRCCS “Cà-Granda” Ospedale Maggiore Policlinico; U.O. di Medicina Interna; Milan Italy
| | | | - Concetta Langella
- Dipartimento di Medicina Molecolare e Biotecnologie Mediche; Università degli Studi di Napoli “Federico II”; Naples Italy
- CEINGE - Biotecnologie Avanzate; Naples Italy
| | - Achille Iolascon
- Dipartimento di Medicina Molecolare e Biotecnologie Mediche; Università degli Studi di Napoli “Federico II”; Naples Italy
- CEINGE - Biotecnologie Avanzate; Naples Italy
| | - Maria Domenica Cappellini
- Fondazione IRCCS “Cà-Granda” Ospedale Maggiore Policlinico; U.O. di Medicina Interna; Milan Italy
- Dipartimento di Scienze Cliniche e di Comunità; Università degli Studi di Milano; Milan Italy
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12
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Machado FB, Machado FB, Faria MA, Lovatel VL, Alves da Silva AF, Radic CP, De Brasi CD, Rios ÁFL, de Sousa Lopes SMC, da Silveira LS, Ruiz-Miranda CR, Ramos ES, Medina-Acosta E. 5meCpG epigenetic marks neighboring a primate-conserved core promoter short tandem repeat indicate X-chromosome inactivation. PLoS One 2014; 9:e103714. [PMID: 25078280 PMCID: PMC4117532 DOI: 10.1371/journal.pone.0103714] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2014] [Accepted: 07/04/2014] [Indexed: 12/31/2022] Open
Abstract
X-chromosome inactivation (XCI) is the epigenetic transcriptional silencing of an X-chromosome during the early stages of embryonic development in female eutherian mammals. XCI assures monoallelic expression in each cell and compensation for dosage-sensitive X-linked genes between females (XX) and males (XY). DNA methylation at the carbon-5 position of the cytosine pyrimidine ring in the context of a CpG dinucleotide sequence (5meCpG) in promoter regions is a key epigenetic marker for transcriptional gene silencing. Using computational analysis, we revealed an extragenic tandem GAAA repeat 230-bp from the landmark CpG island of the human X-linked retinitis pigmentosa 2 RP2 promoter whose 5meCpG status correlates with XCI. We used this RP2 onshore tandem GAAA repeat to develop an allele-specific 5meCpG-based PCR assay that is highly concordant with the human androgen receptor (AR) exonic tandem CAG repeat-based standard HUMARA assay in discriminating active (Xa) from inactive (Xi) X-chromosomes. The RP2 onshore tandem GAAA repeat contains neutral features that are lacking in the AR disease-linked tandem CAG repeat, is highly polymorphic (heterozygosity rates approximately 0.8) and shows minimal variation in the Xa/Xi ratio. The combined informativeness of RP2/AR is approximately 0.97, and this assay excels at determining the 5meCpG status of alleles at the Xp (RP2) and Xq (AR) chromosome arms in a single reaction. These findings are relevant and directly translatable to nonhuman primate models of XCI in which the AR CAG-repeat is monomorphic. We conducted the RP2 onshore tandem GAAA repeat assay in the naturally occurring chimeric New World monkey marmoset (Callitrichidae) and found it to be informative. The RP2 onshore tandem GAAA repeat will facilitate studies on the variable phenotypic expression of dominant and recessive X-linked diseases, epigenetic changes in twins, the physiology of aging hematopoiesis, the pathogenesis of age-related hematopoietic malignancies and the clonality of cancers in human and nonhuman primates.
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Affiliation(s)
- Filipe Brum Machado
- Department of Genetics, School of Medicine, University of São Paulo, Ribeirão Preto, São Paulo, Brazil
| | - Fabricio Brum Machado
- Laboratory of Biotechnology, Universidade Estadual do Norte Fluminense Darcy Ribeiro, Campos do Goytacazes, Rio de Janeiro, Brazil
| | - Milena Amendro Faria
- Laboratory of Biotechnology, Universidade Estadual do Norte Fluminense Darcy Ribeiro, Campos do Goytacazes, Rio de Janeiro, Brazil
| | - Viviane Lamim Lovatel
- Laboratory of Biotechnology, Universidade Estadual do Norte Fluminense Darcy Ribeiro, Campos do Goytacazes, Rio de Janeiro, Brazil
| | - Antonio Francisco Alves da Silva
- Laboratory of Biotechnology, Universidade Estadual do Norte Fluminense Darcy Ribeiro, Campos do Goytacazes, Rio de Janeiro, Brazil
- Molecular Identification and Diagnostics Unit, Hospital Escola Álvaro Alvim, Campos dos Goytacazes, Rio de Janeiro, Brazil
| | - Claudia Pamela Radic
- Laboratory of Molecular Genetics of Hemophilia, Institute of Experimental Medicine, National Academy of Medicine, Buenos Aires, Argentina
| | - Carlos Daniel De Brasi
- Laboratory of Molecular Genetics of Hemophilia, Institute of Experimental Medicine, National Academy of Medicine, Buenos Aires, Argentina
| | - Álvaro Fabricio Lopes Rios
- Laboratory of Biotechnology, Universidade Estadual do Norte Fluminense Darcy Ribeiro, Campos do Goytacazes, Rio de Janeiro, Brazil
| | | | - Leonardo Serafim da Silveira
- Laboratory of Animal Morphology and Pathology, Center for Studies and Research in Wildlife, Universidade Estadual do Norte Fluminense Darcy Ribeiro, Campos do Goytacazes, Rio de Janeiro, Brazil
| | - Carlos Ramon Ruiz-Miranda
- Laboratory of Environmental Sciences, Sector of Studies of Ethology, Reintroduction and Conservation of Wild Animals, Universidade Estadual do Norte Fluminense Darcy Ribeiro, Campos do Goytacazes, Rio de Janeiro, Brazil
| | - Ester Silveira Ramos
- Department of Genetics, School of Medicine, University of São Paulo, Ribeirão Preto, São Paulo, Brazil
- * E-mail: (ESR); (EM-A)
| | - Enrique Medina-Acosta
- Laboratory of Biotechnology, Universidade Estadual do Norte Fluminense Darcy Ribeiro, Campos do Goytacazes, Rio de Janeiro, Brazil
- Molecular Identification and Diagnostics Unit, Hospital Escola Álvaro Alvim, Campos dos Goytacazes, Rio de Janeiro, Brazil
- * E-mail: (ESR); (EM-A)
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13
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X-chromosome inactivation in female newborns conceived by assisted reproductive technologies. Fertil Steril 2014; 101:1718-23. [DOI: 10.1016/j.fertnstert.2014.03.010] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2013] [Revised: 03/05/2014] [Accepted: 03/06/2014] [Indexed: 02/02/2023]
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14
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Xu X, Zhang L, Tong P, Xun G, Su W, Xiong Z, Zhu T, Zheng Y, Luo S, Pan Y, Xia K, Hu Z. Exome sequencing identifiesUPF3Bas the causative gene for a Chinese non-syndrome mental retardation pedigree. Clin Genet 2012; 83:560-4. [DOI: 10.1111/cge.12014] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2012] [Revised: 09/04/2012] [Accepted: 09/04/2012] [Indexed: 01/04/2023]
Affiliation(s)
| | | | | | - G Xun
- Mental Health Center; Shandong Provincial Mental Health Center; Jinan; Shandong; China
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15
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Salsano E, Tabano S, Sirchia SM, Colapietro P, Castellotti B, Gellera C, Rimoldi M, Pensato V, Mariotti C, Pareyson D, Miozzo M, Uziel G. Preferential expression of mutant ABCD1 allele is common in adrenoleukodystrophy female carriers but unrelated to clinical symptoms. Orphanet J Rare Dis 2012; 7:10. [PMID: 22280810 PMCID: PMC3298485 DOI: 10.1186/1750-1172-7-10] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2011] [Accepted: 01/26/2012] [Indexed: 12/14/2022] Open
Abstract
Background Approximately 20% of adrenoleukodystrophy (X-ALD) female carriers may develop clinical manifestations, typically consisting of progressive spastic gait, sensory deficits and bladder dysfunctions. A skewing in X Chromosome Inactivation (XCI), leading to the preferential expression of the X chromosome carrying the mutant ABCD1 allele, has been proposed as a mechanism influencing X-linked adrenoleukodystrophy (X-ALD) carrier phenotype, but reported data so far are conflicting. Methods To shed light into this topic we assessed the XCI pattern in peripheral blood mononuclear cells (PBMCs) of 30 X-ALD carriers. Since a frequent problem with XCI studies is the underestimation of skewing due to an incomplete sample digestion by restriction enzymes, leading to variable results, we developed a pyrosequencing assay to identify samples completely digested, on which to perform the XCI assay. Pyrosequencing was also used to quantify ABCD1 allele-specific expression. Moreover, very long-chain fatty acid (VLCFA) levels were determined in the same patients. Results We found severely (≥90:10) or moderately (≥75:25) skewed XCI in 23 out of 30 (77%) X-ALD carriers and proved that preferential XCI is mainly associated with the preferential expression of the mutant ABCD1 allele, irrespective of the manifestation of symptoms. The expression of mutant ABCD1 allele also correlates with plasma VLCFA concentrations. Conclusions Our results indicate that preferential XCI leads to the favored expression of the mutant ABCD1 allele. This emerges as a general phenomenon in X-ALD carriers not related to the presence of symptoms. Our data support the postulated growth advantage of cells with the preferential expression of the mutant ABCD1 allele, but argue against the use of XCI pattern, ABCD1 allele-specific expression pattern and VLCFA plasma concentration as biomarkers to predict the development of symptoms in X-ALD carriers.
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Affiliation(s)
- Ettore Salsano
- Department of Medicine, Surgery and Dentistry, Università degli Studi di Milano, Milan, Italy
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16
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Nikolov M, Stützer A, Mosch K, Krasauskas A, Soeroes S, Stark H, Urlaub H, Fischle W. Chromatin affinity purification and quantitative mass spectrometry defining the interactome of histone modification patterns. Mol Cell Proteomics 2011; 10:M110.005371. [PMID: 21836164 PMCID: PMC3226395 DOI: 10.1074/mcp.m110.005371] [Citation(s) in RCA: 71] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
Abstract
DNA and histone modifications direct the functional state of chromatin and thereby the readout of the genome. Candidate approaches and histone peptide affinity purification experiments have identified several proteins that bind to chromatin marks. However, the complement of factors that is recruited by individual and combinations of DNA and histone modifications has not yet been defined. Here, we present a strategy based on recombinant, uniformly modified chromatin templates used in affinity purification experiments in conjunction with SILAC-based quantitative mass spectrometry for this purpose. On the prototypic H3K4me3 and H3K9me3 histone modification marks we compare our method with a histone N-terminal peptide affinity purification approach. Our analysis shows that only some factors associate with both, chromatin and peptide matrices but that a surprisingly large number of proteins differ in their association with these templates. Global analysis of the proteins identified implies specific domains mediating recruitment to the chromatin marks. Our proof-of-principle studies show that chromatin templates with defined modification patterns can be used to decipher how the histone code is read and translated.
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Affiliation(s)
- Miroslav Nikolov
- Bioanalytical Mass Spectrometry Group, Max Planck Institute for Biophysical Chemistry, 37077 Göttingen, Germany
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17
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Three new loci for determining x chromosome inactivation patterns. J Mol Diagn 2011; 13:537-40. [PMID: 21726665 DOI: 10.1016/j.jmoldx.2011.05.003] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2011] [Revised: 04/28/2011] [Accepted: 05/06/2011] [Indexed: 01/15/2023] Open
Abstract
The analysis of X chromosome inactivation (XCI) patterns is a widely used diagnostic tool in clinical practice when investigating X-linked diseases. The most commonly used assay to determine XCI patterns takes advantage of a locus within the androgen receptor (AR) gene. This PCR-based assay relies on two differentially methylated restriction enzyme sites (HpaII) and a polymorphic repeat located within this locus. Although highly informative, this locus is not always sufficient to evaluate the X-inactivation status in X-linked disorders. We have identified three new loci that can be used to determine XCI patterns in a methylation-sensitive PCR-based assay. All three loci contain polymorphic repeats and a methylation-sensitive restriction enzyme (HpaII) site, methylation of which was shown to correlate with XCI. DNA from 60 females was used to estimate the heterozygosity of these new loci. The reliability of the loci was validated by showing a high correlation between the results obtained by employing the new loci and the AR locus using DNA from 15 females who were informative for all four loci. Altogether, we show that these loci can be applied easily in molecular diagnostic laboratories, either as a supplement or as an alternative to the existing AR assay.
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18
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Spath MA, Nillesen WN, Smits APT, Feuth TB, Braat DDM, van Kessel AG, Yntema HG. X chromosome inactivation does not define the development of premature ovarian failure in fragile X premutation carriers. Am J Med Genet A 2010; 152A:387-93. [PMID: 20101683 DOI: 10.1002/ajmg.a.33243] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Since only 20% of female fragile X premutation carriers develop premature ovarian failure (POF, i.e., amenorrhea before age of 40 years), and since X chromosome inactivation (XCI) determines the phenotypic severity of full mutation women, we reasoned that the development of POF in fragile X premutation carriers could be due to skewed XCI (XCI ratio >80:20). To determine inactivation ratios and activities of the premutations, inactivation patterns were assessed in peripheral blood samples from 101 fragile X premutation carriers (mean age 47.1 years, range 12-72) through analysis of the AR and FMR1 loci, respectively. In addition, AR inactivation patterns were assessed in peripheral blood samples from 25 women with idiopathic POF (mean age 31.7 years, range 19-48). We addressed the association between age and skewed XCI because older women are prone to XCI skewness. The median XCI ratios were 68% for premutation carriers with POF (N = 37), 67% for premutation carriers without POF (N = 64) and 61% for women with idiopathic POF (N = 25). The incidence of skewing was similar in all groups, that is, 7 of 37 (18.9%) in premutation carriers with POF, 11 of 64 (17.2%) in premutation carriers without POF, and 3 of 25 (12%) in women with idiopathic POF. There was good concordance between inactivation ratios at the two loci tested in 62 premutation carriers (intraclass correlation coefficient = 0.86; P < 0.01). No age-specific skewing was observed. Skewed XCI and activity of the premutation are not associated with POF in fragile X premutation carriers.
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Affiliation(s)
- Marian A Spath
- Department of Obstetrics and Gynecology, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands.
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19
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Kuo PL, Huang SC, Chang LW, Lin CH, Tsai WH, Teng YN. Association of extremely skewed X-chromosome inactivation with Taiwanese women presenting with recurrent pregnancy loss. J Formos Med Assoc 2008; 107:340-3. [PMID: 18445549 DOI: 10.1016/s0929-6646(08)60096-0] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
X-chromosome inactivation (XCI) is a phenomenon that occurs in female mammals. Typically, maternally and paternally-derived X chromosomes are inactivated at approximately the same frequency. If preferential inactivation occurs, the person is considered to have skewed XCI. Skewed XCI has been reported to occur more frequently in women who experience recurrent pregnancy loss (RPL). In this study, we sought to investigate if there is an association between skewed XCI and unexplained RPL in Taiwanese women. A total of 194 women who had experienced unexplained RPL were recruited into the study. Human androgen receptor or DXS6673E and DX15-134 loci were used in the XCI assay. The results of our study suggested that a cut-off point less than 90% may not be justified for skewed XCI. Only extremely skewed (more than 95%) XCI is associated with RPL. Extremely skewed XCI occurs in a subset of Taiwanese women with RPL.
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Affiliation(s)
- Pao-Lin Kuo
- Department of Obstetrics and Gynecology, National Cheng Kung University College of Medicine, Tainan, Taiwan
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20
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Izumi K, Nakano M, Kosaki K, Kosaki R, Hosogai N, Matsumoto H, Hasegawa T, Takahashi T, Kosaki K. Two distinctive mechanisms leading to disruption of the SHOX transcription unit in a single family. Am J Med Genet A 2007; 143A:2838-42. [PMID: 17994568 DOI: 10.1002/ajmg.a.31870] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Affiliation(s)
- Kosuke Izumi
- Department of Pediatrics, Keio University School of Medicine, Tokyo, Japan
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21
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Hellenbroich Y, Grzeschik KH, Krapp M, Jarutat T, Lehrmann-Petersen C, Buiting K, Gillessen-Kaesbach G. Reduced penetrance in a family with X-linked dominant chondrodysplasia punctata. Eur J Med Genet 2007; 50:392-8. [PMID: 17625999 DOI: 10.1016/j.ejmg.2007.05.004] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2007] [Accepted: 05/19/2007] [Indexed: 10/23/2022]
Abstract
X-linked dominant chondrodysplasia punctata (Conradi-Hünermann disease, CDPX2) is characterised by short stature, stippled epiphyses, cataracts, ichthyosiform erythroderma and patchy alopecia of the scalp. The disorder is caused by mutations within the emopamil binding protein (EBP) gene encoding a 3beta-hydroxysteroid-Delta(8),Delta(7)-isomerase. The intrafamilial variation of disease severity is a known feature of CDPX2 probably caused by skewed X-inactivation. We report on a female fetus with typical symptoms of CDPX2 such as short limbs, postaxial polydactyly, ichthyotic skin lesions and punctate calcifications. Molecular genetic analysis of the EBP gene revealed a nonsense mutation (c.328C>T, p.R110X), which was previously detected in one CDPX2 patient and in a second female patient, who was only affected on one body side and erroneously diagnosed as CHILD syndrome. Surprisingly, the mother of our fetus carries the same mutation without having any signs of CDPX2. X-inactivation studies did not reveal any evidence of skewing neither in the mother nor in the fetus.
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Affiliation(s)
- Yorck Hellenbroich
- Institut für Humangenetik, Universität zu Lübeck, Ratzeburger Allee 160, 23538 Lübeck, Germany.
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22
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Bretherick KL, Metzger DL, Chanoine JP, Panagiotopoulos C, Watson SK, Lam WL, Fluker MR, Brown CJ, Robinson WP. Skewed X-chromosome inactivation is associated with primary but not secondary ovarian failure. Am J Med Genet A 2007; 143A:945-51. [PMID: 17431892 DOI: 10.1002/ajmg.a.31679] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Premature ovarian failure (POF) is the occurrence of menopause before the age of 40, and may present with either primary or secondary amenorrhea. Numerous cases of POF in women with X-chromosome deletions or translocations have been reported; thus, it is possible that smaller rearrangements undetectable by conventional cytogenetics may contribute to POF in some patients. In females with an abnormal X chromosome, cells with inactivation of the normal X may be selected against, causing skewed X-chromosome inactivation (XCI). We therefore assessed XCI by methylation sensitive restriction digestion and PCR amplification at the androgen receptor (AR) locus, in 4 primary and 55 secondary POF patients and 109 control women. In samples heterozygous at AR and therefore informative for the skewing assay, the frequency of skewed XCI among the women with secondary amenorrhea was identical to that in control women, with 4 out of 48 (8.3%) secondary ovarian failure patients and 8 out of 97 (8.2%) control women having > or =90% skewing. Notably, all three primary amenorrhea patients that were informative at AR had skewed XCI > or =90% (P = 0.001 vs. control women; Fisher's exact test). To investigate whether X-chromosome copy number alterations were responsible, DNA from selected patients with skewed XCI was examined by high resolution DNA microarray, however no potential regions of DNA addition or deletion were confirmed by FISH or PCR. X-chromosome abnormalities undetectable by array, or reduced follicular pool due to an early trisomic rescue event, may explain the skewed XCI observed in POF patients presenting with primary amenorrhea.
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Affiliation(s)
- Karla L Bretherick
- Department of Medical Genetics, University of British Columbia, Vancouver, British Columbia, Canada
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23
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Dayer AG, Bottani A, Bouchardy I, Fluss J, Antonarakis SE, Haenggeli CA, Morris MA. MECP2 mutant allele in a boy with Rett syndrome and his unaffected heterozygous mother. Brain Dev 2007; 29:47-50. [PMID: 16844334 DOI: 10.1016/j.braindev.2006.06.001] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/16/2006] [Revised: 05/31/2006] [Accepted: 06/09/2006] [Indexed: 11/30/2022]
Abstract
Rett syndrome is a severe neurodevelopmental disorder affecting principally females and characterized by a normal postnatal development followed by stagnation and regression of acquired skills. We report a 4-year-old boy with a Rett syndrome phenotype and his unaffected mother both carrying a 44 bp truncating deletion mutation (c.1158del44 or p.388X) in the MECP2 gene. The presence of a skewed X inactivation in the mother provides a possible explanation for the absence of penetrance. The finding of a MECP2 mutation in an unaffected female complicates genetic counseling and further confirms that it is essential to look for mutations in the mothers of all patients with MECP2 mutations.
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Affiliation(s)
- Alexandre G Dayer
- Service of Medical Genetics and Neuropediatric Unit, Geneva University Hospitals, 1 rue Michel-Servet 1211, Geneva Switzerland.
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Djuric U, El-Maarri O, Lamb B, Kuick R, Seoud M, Coullin P, Oldenburg J, Hanash S, Slim R. Familial molar tissues due to mutations in the inflammatory gene, NALP7, have normal postzygotic DNA methylation. Hum Genet 2006; 120:390-5. [PMID: 16874523 DOI: 10.1007/s00439-006-0192-3] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2006] [Accepted: 04/19/2006] [Indexed: 01/19/2023]
Abstract
An imprinting disorder has been believed to underlie the etiology of familial biparental hydatidiform moles (HMs) based on the abnormal methylation or expression of imprinted genes in molar tissues. However, the extent of the epigenetic defect in these tissues and the developmental stage at which the disorder begins have been poorly defined. In this study, we assessed the extent of abnormal DNA methylation in two HMs caused by mutations in the recently identified 19q13.4 gene, NALP7. We demonstrate normal postzygotic DNA methylation patterns at major repetitive and long interspersed nuclear elements (LINEs), genes on the inactive X-chromosome, three-cancer related genes, and CpG rich regions surrounding the PEG3 differentially methylated region (DMR). Our data provide a comprehensive assessment of DNA methylation in familial molar tissues and indicate that abnormal DNA methylation in these tissues is restricted to imprinted DMRs. The known role of NALP7 in apoptosis and inflammation pinpoints previously unrecognized pathways that could directly or indirectly underlie the abnormal methylation of imprinted genes in molar tissues.
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Affiliation(s)
- Ugljesa Djuric
- Departments of Human Genetics and Obstetrics and Gynecology, McGill University Health Center, Montreal, Canada, H3G 1A4
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25
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Bretherick K, Gair J, Robinson WP. The association of skewed X chromosome inactivation with aneuploidy in humans. Cytogenet Genome Res 2005; 111:260-5. [PMID: 16192703 DOI: 10.1159/000086898] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2004] [Accepted: 02/22/2005] [Indexed: 01/25/2023] Open
Abstract
Recently, we reported that skewed X chromosome inactivation (XCI) was more common in women who had experienced a trisomic pregnancy as compared to control women. Rather than an overall shift in the distribution of skewing there appears to only be an excess of extreme (= 95%) skewing. Further analysis of our data reveals that the increase in skewed XCI is dependent on which chromosome is involved in the trisomy and how many trisomies the woman has experienced, although sample sizes in each group are small. In this review we discuss limitations of the commonly used assays of XCI, which use measurements of DNA methylation to infer skewing patterns, and review the data based on current knowledge of the causes of XCI skewing. Gonadal mosaicism, premature aging, loss of methylation at some CpGs, and X-linked mutations can all be considered as potential mechanisms explaining both increased risk of trisomy and skewed XCI. While further research is needed to evaluate the role of each of these, the association of trisomy with apparent skewed XCI in the mother offers new opportunities to clarify the risk factors for and causes of the high incidence of aneuploidy in human females.
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Affiliation(s)
- K Bretherick
- Department of Medical Genetics, University of British Columbia, BC Research Institute for Children's and Women's Health, Vancouver, BC, Canada
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26
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Hatakeyama C, Anderson CL, Beever CL, Peñaherrera MS, Brown CJ, Robinson WP. The dynamics of X-inactivation skewing as women age. Clin Genet 2005; 66:327-32. [PMID: 15355435 DOI: 10.1111/j.1399-0004.2004.00310.x] [Citation(s) in RCA: 111] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Non-random X-chromosome inactivation (XCI) has been associated with X-linked diseases, neoplastic diseases, recurrent pregnancy loss, and trisomy risk. It also occurs more commonly in older female populations. To understand the etiology of non-random XCI and utilize this assay appropriately in clinical research and practice, the age-related alteration in XCI patterns in normal females needs to be clearly defined. In the present study, we evaluated the XCI status in 350 unselected women aged 0-88 years with unknown history of genetic disorders or abnormal pregnancies. DNA samples were extracted from peripheral blood and analyzed by a methylation-based assay at the androgen receptor locus. A weak but significant positive correlation was observed between age and degree of skewing in XCI over the whole age range (r = 0.23, p < 0.0001), and skewing values become non-normally distributed at older ages. However, the increase in skewed XCI appears to be more pronounced after age 30 than at younger ages. This trend supports the model of increased skewing with age as a consequence of hematopoietic stem cell senescence. An alternative possibility is that there is allele-specific loss of methylation with time that results in the appearance of increased XCI skewing using a methylation-based assay.
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Affiliation(s)
- C Hatakeyama
- Department of Medical Genetics, University of British Columbia, Vancouver, BC, Canada
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27
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Abstract
Between 0.5 and 1.0% of couples experience recurrent pregnancy loss (RPL), which is defined as three or more consecutive miscarriages. Losses are classified as pre-embryonic (<5 weeks), embryonic (5-10 weeks) or fetal (>10 weeks). Genetic abnormalities are responsible for RPL in 2-4% of these couples. Inadequate progesterone production has been proposed a cause of RPL and progesterone is given to prevent miscarriage, despite a lack of supportive evidence. The factor V Leiden and prothrombin G20210A mutations are common inherited thrombophilias also associated with RPL. Antenatal thromboprophylaxis is sometimes recommended although no data exist regarding efficacy. Antiphospholipid syndrome is known to cause RPL and antenatal thromboprophylaxis reduces the risk of miscarriage. Uterine abnormalities might also result in RPL. About 50% of cases of RPL have no identifiable cause. Alloimmune incompatibility has been proposed as a cause for RPL in these women. The concept of alloimmune-related RPL has not been scientifically validated.
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Affiliation(s)
- T Flint Porter
- Department of Obstetrics and Gynecology, University of Utah Health Sciences Center, Maternal-Fetal Medicine, LDS Hospital, 8th Avenue and C Street, Salt Lake City, Utah 84143, USA.
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28
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Sullivan AK, Marcus M, Epstein MP, Allen EG, Anido AE, Paquin JJ, Yadav-Shah M, Sherman SL. Association of FMR1 repeat size with ovarian dysfunction. Hum Reprod 2004; 20:402-12. [PMID: 15608041 DOI: 10.1093/humrep/deh635] [Citation(s) in RCA: 313] [Impact Index Per Article: 15.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
BACKGROUND Women who carry the FMR1 premutation allele have a significantly increased risk for ovarian dysfunction. We hypothesize that molecular characteristics of the FMR1 gene may explain this increased risk. METHODS Thus, we examined the effect of FMR1 CGG repeat size and related factors on measures of ovarian dysfunction using data from 507 women with a wide range of repeat sizes. RESULTS AND CONCLUSIONS We found a significant positive association of repeat size with ovarian dysfunction, but have preliminary evidence that this relationship is non-linear. We suggest that FMR1 repeat size in the lower range (<80 repeats) contributes to the variation in age at menopause; thus, FMR1 could be considered a quantitative trait locus. More importantly, when repeat size exceeds this threshold, the increase in risk for ovarian dysfunction is clinically significant. Intriguingly, this risk appears to plateau, or perhaps decrease, among women with very high repeats (> or =100 repeats).
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Affiliation(s)
- A K Sullivan
- Department of Human Genetics, Emory University School of Medicine, Atlanta, Georgia 30322, USA
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29
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Allen EG, He W, Yadav-Shah M, Sherman SL. A study of the distributional characteristics of FMR1 transcript levels in 238 individuals. Hum Genet 2004; 114:439-47. [PMID: 14758538 DOI: 10.1007/s00439-004-1086-x] [Citation(s) in RCA: 88] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2003] [Accepted: 01/12/2004] [Indexed: 11/30/2022]
Abstract
Fragile X syndrome, the most common form of inherited mental retardation, is caused by hyperexpansion and hypermethylation of a CGG repeat tract in the 5' untranslated region of the FMR1 gene. This methylation causes the gene to be transcriptionally silenced. In addition to the common allele form with less than 41 repeats, there are two other allelic forms of the FMR1 gene that are unmethylated: premutation (61-200 CGG repeats) and intermediate (41-60 CGG repeats). Recently, premutation-specific phenotypes not related to fragile X syndrome have been reported: a 20-fold increased risk for premature ovarian failure (POF) among female carriers and an increased risk for a tremor ataxia syndrome (TAS) primarily among older male carriers. At the molecular level, increased levels of FMR1 transcript have been observed among premutation carriers. Increased levels of transcript may be causally related to the POF or TAS phenotypes or may be a surrogate of some other allelic property. In this report, we have examined the distributional properties of transcript levels by repeat size and gender among 238 individuals. We have confirmed a significant linear relationship between transcript level and repeat size in males and females. The evidence for the linear effect is primarily within the premutation size alleles.
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Affiliation(s)
- Emily G Allen
- Department of Human Genetics, Emory University, Atlanta, GA 30322, USA
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30
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Beever CL, Peñaherrera MS, Langlois S, Robinson WR. X chromosome inactivation patterns in Russell-Silver syndrome patients and their mothers. Am J Med Genet A 2003; 123A:231-5. [PMID: 14608642 DOI: 10.1002/ajmg.a.20317] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Russell-Silver syndrome (RSS) is a disorder characterized by pre- and post-natal growth deficiency, triangular facies, relative macrocephaly, and body asymmetry. Maternal uniparental disomy for chromosome 7 has been found in approximately 10% of RSS cases, while the cause in the remaining cases is unknown. Although most cases of RSS are sporadic, at least 25 families have been reported with familial RSS and inheritance patterns of RSS consistent with an X-linked dominant mutation. Thus, we hypothesized that skewed X-chromosome inactivation (XCI) could be increased in some females with RSS as a consequence of a tendency to have the mutant allele on the predominantly active chromosome. Alternatively, unaffected mothers of children with RSS may tend to be skewed due to preferential inactivation of the mutant allele. In support of this last hypothesis, a significant increase in extremely skewed XCI (>95%) was found in mothers of children with RSS (4 of 21, 19%) compared to controls (2 of 101, 2%) (P = 0.008). However, an increase in skewed XCI was also observed in female patients who had unexplained short stature but did not fulfill the criteria for RSS (3 of 17, 18%) (P = 0.02), but not in those diagnosed as RSS (0 of 7, n.s.). Different mechanisms may underlie the increase in skewing in each group, possibly being due to different X-linked mutations or growth restriction during very early in utero development.
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Affiliation(s)
- Christy L Beever
- Department of Medical Genetics, University of British Columbia, Vancouver, British Columbia, Canada
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31
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Beever CL, Stephenson MD, Peñaherrera MS, Jiang RH, Kalousek DK, Hayden M, Field L, Brown CJ, Robinson WP. Skewed X-chromosome inactivation is associated with trisomy in women ascertained on the basis of recurrent spontaneous abortion or chromosomally abnormal pregnancies. Am J Hum Genet 2003; 72:399-407. [PMID: 12497247 PMCID: PMC379232 DOI: 10.1086/346119] [Citation(s) in RCA: 67] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2002] [Accepted: 11/11/2002] [Indexed: 11/03/2022] Open
Abstract
An increase in extremely skewed X-chromosome inactivation (XCI) (> or = 90%) among women who experienced recurrent spontaneous abortion (RSA) has been previously reported. To further delineate the etiology of this association, we have evaluated XCI status in 207 women who experience RSA. A significant excess of trisomic losses was observed among the women who had RSA with skewed XCI versus those without skewed XCI (P=.02). There was also a significant excess of boys among live births in this group (P=.04), which is contrary to expectations if the cause of skewed XCI was only that these women carried X-linked lethal mutations. To confirm the association between skewed XCI and the risk of trisomy, an independent group of 53 women, ascertained on the basis of a prenatal diagnosis of trisomy mosaicism, were investigated. Only cases for which the trisomy was shown to be of maternal meiotic origin were included. The results show a significantly higher level of extreme skewing (> or = 90%) in women whose pregnancies involved placental trisomy mosaicism (17%) than in either of two separate control populations (n=102 and 99) (P=.02 compared with total control subjects). An additional 11 cases were ascertained on the basis of one or more trisomic-pregnancy losses. When all women in the present study with a trisomic pregnancy (n=103) were considered together, skewed XCI was identified in 18%, as compared with 7% in all controls (n=201) (P=.005). This difference was more pronounced when a cutoff of extreme skewing of 95% was used (10% vs. 1.5% skewed; P=.002). Maternal age was not associated with skewing in either the patient or control populations and therefore cannot account for the association with trisomy. Previous studies have shown that a reduced ovarian reserve is associated with increased risk of trisomic pregnancies. We hypothesize that the association between skewed XCI and trisomic pregnancies is produced by a common mechanism that underlies both and that involves a reduction of the size of the follicular pool.
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Affiliation(s)
- C L Beever
- Department of Medical Genetics, University of British Columbia, Vancouver, BC, Canada
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