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Lubs HA, Stevenson RE, Schwartz CE. Fragile X and X-linked intellectual disability: four decades of discovery. Am J Hum Genet 2012; 90:579-90. [PMID: 22482801 DOI: 10.1016/j.ajhg.2012.02.018] [Citation(s) in RCA: 165] [Impact Index Per Article: 13.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2011] [Revised: 01/03/2012] [Accepted: 02/17/2012] [Indexed: 01/18/2023] Open
Abstract
X-Linked intellectual disability (XLID) accounts for 5%-10% of intellectual disability in males. Over 150 syndromes, the most common of which is the fragile X syndrome, have been described. A large number of families with nonsyndromal XLID, 95 of which have been regionally mapped, have been described as well. Mutations in 102 X-linked genes have been associated with 81 of these XLID syndromes and with 35 of the regionally mapped families with nonsyndromal XLID. Identification of these genes has enabled considerable reclassification and better understanding of the biological basis of XLID. At the same time, it has improved the clinical diagnosis of XLID and allowed for carrier detection and prevention strategies through gamete donation, prenatal diagnosis, and genetic counseling. Progress in delineating XLID has far outpaced the efforts to understand the genetic basis for autosomal intellectual disability. In large measure, this has been because of the relative ease of identifying families with XLID and finding the responsible mutations, as well as the determined and interactive efforts of a small group of researchers worldwide.
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Affiliation(s)
- Herbert A Lubs
- Greenwood Genetic Center, JC Self Research Institute of Human Genetics, 113 Gregor Mendel Circle, Greenwood, SC 29646, USA
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2
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Abstract
X-linked mental retardation (XLMR) is a common cause of inherited intellectual disability with an estimated prevalence of approximately 1/1000 males. Most XLMR conditions are inherited as X-linked recessive traits, although female carriers may manifest usually milder symptoms. We have listed 215 XLMR conditions, subdivided according to their clinical presentation: 149 with specific clinical findings, including 98 syndromes and 51 neuromuscular conditions, and 66 nonspecific (MRX) forms. We also present a map of the 82 XLMR genes cloned to date (November 2007) and a map of the 97 conditions that have been positioned by linkage analysis or cytogenetic breakpoints. We briefly consider the molecular function of known XLMR proteins and discuss the possible strategies to identify the remaining XLMR genes. Final remarks are made on the natural history of XLMR conditions and on diagnostic issues.
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Affiliation(s)
- Pietro Chiurazzi
- Institute of Medical Genetics, Catholic University, Rome, Italy.
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3
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Zhang X, Liu Q, Chen B, Guo C, Li J, Gao G, Guo Y, Gong Y. A locus for nonspecific X-linked mental retardation mapped to a 22.3 cM region of Xp11.3-q22.3. Am J Med Genet A 2005; 129A:286-9. [PMID: 15326629 DOI: 10.1002/ajmg.a.30121] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
By using several microsatellite markers scattered along the X chromosome, we studied a Chinese family with nonspecific X-linked mental retardation (MRX84) to search for a region including the MRX84 locus that was linked to the markers. Two-point linkage analysis demonstrated linkage between the disorder and several markers located at Xq22.2, with maximum LOD score Z(max) = 2.41 at recombination fraction theta = 0 for DXS1191 and DXS1230, respectively. Recombination events were observed with flanking markers DXS8080 and DXS456, located at Xp11.3 and Xq22.3, respectively, and a region of approximately 22.3 cM was defined. Accordingly, markers distal to Xp11.3 and Xq22.3 segregated independently of the disease. The localized region observed in this Chinese family overlaps with 29 other MRX loci previously reported in Xp11.3-q22.3. These results should contribute to the identification of the disease gene for the MRX84 disorder.
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Affiliation(s)
- Xiyu Zhang
- Institute of Medical Genetics, Shandong University School of Medicine, Jinan, People's Republic of China
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Caspari R, Uhlhaas S, Friedl W, Knapp M, Propping P. Mapping of a gene for nonspecific X-linked mental retardation (MRX 75) to Xq24-q26. AMERICAN JOURNAL OF MEDICAL GENETICS 2000; 93:290-3. [PMID: 10946355 DOI: 10.1002/1096-8628(20000814)93:4<290::aid-ajmg7>3.0.co;2-m] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Nonspecific X-linked mental retardation is a heterogeneous condition consisting of nonsyndromal mental retardation in males. It is caused by mutation in one of several genes on the X chromosome (MRX genes). Here we report on the localization of a presumptive MRX gene to chromosomal region Xq24-q26 in a German family with nonspecific X-linked mental retardation (MRX 75, HUGO Human Gene Nomenclature Committee). Two point linkage analysis with 23 informative markers gave a lod score of 2.53 at theta = 0 for markers DXS425, DXS1254, DXS1114, and HPRT.
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Affiliation(s)
- R Caspari
- Medizinische Klinik I, Universität Bonn, Germany.
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5
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Gendrot C, Ronce N, Raynaud M, Ayrault AD, Dourlens J, Castelnau P, Muh JP, Chelly J, Moraine C. X-linked nonspecific mental retardation (MRX16) mapping to distal Xq28: Linkage study and neuropsychological data in a large family. ACTA ACUST UNITED AC 1999. [DOI: 10.1002/(sici)1096-8628(19990423)83:5<411::aid-ajmg14>3.0.co;2-b] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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Sloan-Béna F, Philippe C, LeHeup B, Wuilque F, Levy ER, Chéry M, Jonveaux P, Monaco AP. Characterisation of an inverted X chromosome (p11.2q21.3) associated with mental retardation using FISH. J Med Genet 1998; 35:146-50. [PMID: 9507395 PMCID: PMC1051220 DOI: 10.1136/jmg.35.2.146] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
We report on a patient with a pericentric inversion of the X chromosome, 46,Y,inv(X) (p11.2q21.3), who was referred for cytogenetic analysis because of mild mental retardation, short stature, prepubescent macro-orchidism, and submucous cleft palate. The same chromosomal abnormality was found in the proband's mother. The inverted X chromosome was late replicating in all the mother's lymphocytes studied, indicative of a likely unbalanced inversion. We show, by fluorescence in situ hybridisation (FISH) using a panel of ordered yeast artificial chromosome (YAC) clones, that the Xp breakpoint is localised in Xp11.23 between DXS146 and DXS255 and that the Xq breakpoint is assigned to the X-Y homologous region in Xq21.3. YACs crossing the Xp and Xq breakpoints have been identified. One of these two breakpoints could be linked to the mental retardation in this patient as many non-specific mental retardation (MRX) loci have previously been located in the pericentromeric region of the X chromosome. Morever, the elucidation at the molecular level of this rearrangement will also indicate if cleft palate or prepubescent macro-orchidism, or both, in this boy are related to one of the two X breakpoints.
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Affiliation(s)
- F Sloan-Béna
- Laboratoire de Génétique Médicale, CHU Nancy-Brabois, France
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8
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Nakae J, Abe S, Tajima T, Shinohara N, Murashita M, Igarashi Y, Kusuda S, Suzuki J, Fujieda K. Three novel mutations and a de novo deletion mutation of the DAX-1 gene in patients with X-linked adrenal hypoplasia congenita. J Clin Endocrinol Metab 1997; 82:3835-41. [PMID: 9360549 DOI: 10.1210/jcem.82.11.4342] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
The DAX-1 [DSS (dosage sensitive sex)-AHC critical region on the X, gene 1] gene is responsible for X-linked adrenal hypoplasia congenita (AHC). However, DAX-1 protein structure-function relationships are not well understood. Identification of missense mutations may help to reveal these relationships. We analyzed the DAX-1 gene from seven patients in six kindreds with X-linked AHC and identified one frameshift mutation, two missense mutations, and three deletion mutations. Case 1 had a 388delAG frameshift mutation, inducing a premature stop codon at position 70. Case 2 had a missense mutation, Lys382Asn, which encodes an asparagine (Asn) for lysine (Lys) at position 382. Sibling cases of 3-1 and 3-2 had a missense mutation of Trp291 Cys, which encodes a substitution of cysteine (Cys) for tryptophan (Try) at position 291. The tryptophan (Trp) at position 291 and lysine (Lys) at position 382 in human DAX-1 protein are highly conserved among other related orphan nuclear receptor superfamily members. Cases 4, 5, and 6 showed deletion mutation. In case 6, a de novo deletion mutation was revealed by both southern hybridization and polymerase chain reaction (PCR) of a GGAA tetranucleotide tandem repeat. These findings suggest that: 1) Trp at position 291 and Lys at position 382, located in the C-terminal presumptive ligand binding domain, are important to the functional role of the DAX-1 protein in adrenal embryogenesis and/or in hypothalamic-pituitary activity; and 2) molecular analysis of the DAX-1 gene may help genetic counseling, even in cases with deletion mutation, because a detection of de novo deletion may exclude another affected or carrier child.
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Affiliation(s)
- J Nakae
- Department of Pediatrics, Hokkaido University School of Medicine, Sapporo, Japan
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9
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Toutain A, Ayrault AD, Moraine C. Mental retardation in Nance-Horan syndrome: clinical and neuropsychological assessment in four families. AMERICAN JOURNAL OF MEDICAL GENETICS 1997; 71:305-14. [PMID: 9268101 DOI: 10.1002/(sici)1096-8628(19970822)71:3<305::aid-ajmg11>3.0.co;2-o] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Nance-Horan syndrome (NHS) is a rare X-linked condition comprising congenital cataract with microcornea, distinctive dental, and evocative facial anomalies. Intellectual handicap was mentioned in seven published NHS patients. We performed a clinical study focused on psychomotor development, intellectual abilities, and behavior in 13 affected males in four NHS families, and present the results of a neuropsychological evaluation in 7 of them. Our study confirms that mental retardation (MR) can be a major component of the NHS. Combining our data with those from the literature leads to a frequency of MR in NHS of around 30%. In most cases, MR is mild or moderate (80%) and not associated with motor delay. Conversely, a profound mental handicap associated with autistic traits may be observed. MR has intra- and inter-familial variability but does not appear to be expressed in carriers. Awareness of MR in NHS may be of importance in the management of the patients, especially in terms of education. Cloning and characterization of the gene and analysis of mutations will be an important step towards understanding the molecular basis of mental deficiency in NHS, and in delineation from the other XLMR conditions at Xp22.
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Affiliation(s)
- A Toutain
- Service de Génétique, Hôpital Bretonneau, Centre Hospitalo-Universitaire, Tours, France
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Häne B, Schroer RJ, Arena JF, Lubs HA, Schwartz CE, Stevenson RE. Nonsyndromic X-linked mental retardation: review and mapping of MRX29 to Xp21. Clin Genet 1996; 50:176-83. [PMID: 9001795 DOI: 10.1111/j.1399-0004.1996.tb02622.x] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
The gene responsible for nonsyndromic mental retardation in a family with 7 affected males has been localized to Xp21. The maximal two-point lod score was 3.31 for tight linkage to marker DXS1202 in Xp21.3-p22.3 with crossovers between the 3' portion of the DMD gene (DXS1234) proximally and locus DXS989 distally. The XLMR gene in this family has been assigned the designation MRX29. The localization overlaps with at least six other MRX entities linked to the distal short arm of the X chromosome.
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Affiliation(s)
- B Häne
- J. C. Self Research Institute, Greenwood Genetic Center, South Carolina 29646, USA
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11
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Baron-Cohen S, Burt L, Smith-Laittan F, Harrison J, Bolton P. Synaesthesia: prevalence and familiality. Perception 1996; 25:1073-9. [PMID: 8983047 DOI: 10.1068/p251073] [Citation(s) in RCA: 150] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Synaesthesia is a condition in which a mixing of the senses occurs; for example, sounds trigger the experience of colour. Previous reports suggest this may be familial, but no systematic studies exist. In addition, there are no reliable prevalence or sex-ratio figures for the condition, which is essential for establishing if the reported sex ratio (female bias) is reliable, and if this implicates a sex-linked genetic mechanism. Two independent population studies were conducted in the city of Cambridge, England (studies 1 and 2 here), as necessary background to the family genetic study of synaesthesia (study 3). Studies 1 and 2 arrived at an almost identical prevalence rate for synaesthesia: approximately 1 case in 2000. The sex ratio found was 6:1 (female:male). A third of cases also reported familial aggregation. In study 3 six families were examined, and first-degree relatives were tested for genuineness of the condition. All six families were indeed multiplex for synaesthesia. Alternative modes of inheritance are discussed.
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Affiliation(s)
- S Baron-Cohen
- Department of Environmental Psychology, University of Cambridge, UK
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12
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Hamel BC, Kremer H, Wesby-van Swaay E, van den Helm B, Smits AP, Oostra BA, Ropers HH, Mariman EC. A gene for nonspecific X-linked mental retardation (MRX41) is located in the distal segment of Xq28. AMERICAN JOURNAL OF MEDICAL GENETICS 1996; 64:131-3. [PMID: 8826463 DOI: 10.1002/(sici)1096-8628(19960712)64:1<131::aid-ajmg22>3.0.co;2-n] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
We report on a family in which nonsyndromal mild to moderate mental retardation segregates as an X-linked trait (MRX41). Two point linkage analysis demonstrated linkage between the disorder and marker DXS3 in Xq21.33 with a lod score of 2.56 at theta = 0.0 and marker DXS1108 in Xq28 with a lod score of 3.82 at theta = 0.0. Multipoint linkage analysis showed that the odds for a location of the gene in Xq28 vs Xq21.33 are 100:1. This is the fourth family with non-specific X-linked mental retardation with Xq28-qter as the most likely gene localization.
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Affiliation(s)
- B C Hamel
- Department of Human Genetics, University Hospital, Nijmegen, The Netherlands
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13
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Bar-David S, Lerer I, Sarfaty CK, Kohan ZG, Meiner V, Zlotogora J, Abeliovich D. Localization of two X-linked mental retardation (XLMR) genes to Xp: MRX37 gene at Xp22.31-p22.32 and a putative MRX gene on Xp22.11-p22.2. AMERICAN JOURNAL OF MEDICAL GENETICS 1996; 64:83-8. [PMID: 8826456 DOI: 10.1002/(sici)1096-8628(19960712)64:1<83::aid-ajmg15>3.0.co;2-o] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
MRX genes of 2 families with X-linked mental retardation (XLMR) were localized by linkage analysis. In family A, the gene was mapped to Xp22.31-p22.32, with significant LOD scores to various Xp22 markers within a distance of 6 Mb between DXS1223 and DXS1224. The MRX gene of this family was designated MRX37. In a mentally retarded female who is a carrier of the MRX37 gene, a random pattern of X inactivation was demonstrated. In family B, a positive LOD score, although not significant (< + 2), was found with the marker DXS1202 at Xp22.11-p22.2.
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Affiliation(s)
- S Bar-David
- Department of Human Genetics, Hadassah Hebrew University Hospital, Jerusalem, Israel
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14
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Donnelly AJ, Partington MW, Ryan AK, Mulley JC. Regional localisation of two non-specific X-linked mental retardation genes (MRX30 and MRX31). AMERICAN JOURNAL OF MEDICAL GENETICS 1996; 64:113-20. [PMID: 8826460 DOI: 10.1002/(sici)1096-8628(19960712)64:1<113::aid-ajmg19>3.0.co;2-q] [Citation(s) in RCA: 26] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Two genes responsible for X-linked mental retardation have been localised by linkage analysis. MRX30 maps to a 28 cM region flanked by the loci DXS990 (Xq21.3) and DXS424 (Xq24). A significant multipoint lod score of 2.78 was detected between the loci DXS1120 and DXS456. MRX31 maps to a 12 cM region that spans the centromere from DXS1126 (Xp11.23) to DXS1124 (Xq13.3). Significant two-point lod scores, at a recombination fraction of zero, were obtained with the loci DXS991 (Zmax = 2.06), AR (Zmax = 3.44), PGK1P1 (Zmax = 2.06) and DXS453 (Zmax = 3.31). The MRX30 localisation overlaps that of MRX8, 13, 20 and 26 and defines the position of a new MRX gene on the basis of a set of non-overlapping regional localisations. The MRX31 localisation overlaps the localisations of many of the pericentromeric MRX loci (MRX 1, 4, 5, 7, 8, 9, 12, 13, 14, 15, 17, 20, 22 and 26). There are now at least 8 distinct loci associated with non-specific mental retardation on the X chromosome defined, in order from pter to qter, by localisation for MRX24, MRX2, MRX10, MRX1, MRX30, MRX27, FRAXE and MRX3.
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Affiliation(s)
- A J Donnelly
- Department of Cytogenetics and Molecular Genetics, Women's and Children's Hospital, Adelaide, Australia
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Hamel BC, Smits AP, Otten BJ, van den Helm B, Ropers HH, Mariman EC. Familial X-linked mental retardation and isolated growth hormone deficiency: clinical and molecular findings. AMERICAN JOURNAL OF MEDICAL GENETICS 1996; 64:35-41. [PMID: 8826446 DOI: 10.1002/(sici)1096-8628(19960712)64:1<35::aid-ajmg5>3.0.co;2-q] [Citation(s) in RCA: 47] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
We report on several members of a family with varying degrees of X-linked mental retardation (XLMR), isolated growth hormone deficiency (IGHD), and infantile behaviour but without other consistent phenotypic abnormalities. Male patients continued to grow until well into their twenties and reached a height ranging from 135 to 159 cm. Except one, all female carriers were mentally normal; their adult height ranged from 159 to 168 cm. By linkage studies we have assigned the underlying genetic defect to the Xq24-q27.3 region, with a maximum lod score of Z = 3.26 at theta = 0.0 for the DXS294 locus. The XLMR-IGHD phenotype in these patients may be due to pleiotropic effects of a single gene or it may represent a contiguous gene syndrome.
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Affiliation(s)
- B C Hamel
- Department of Human Genetics, University Hospital, Nijmegen, The Netherlands
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des Portes V, Bachner L, Brüls T, Beldjord C, Billuart P, Soufir N, Bienvenu T, Vinet MC, Malaspina E, Marchiani V, Bertini E, Kahn A, Franzoni E, Chelly J. X-linked neurodegenerative syndrome with congenital ataxia, late-onset progressive myoclonic encephalopathy and selective macular degeneration, linked to Xp22.33-pter. AMERICAN JOURNAL OF MEDICAL GENETICS 1996; 64:69-72. [PMID: 8826451 DOI: 10.1002/(sici)1096-8628(19960712)64:1<69::aid-ajmg10>3.0.co;2-q] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Linkage analysis was performed in a previously described family segregating for an X-linked progressive neurological disorder [Bertini et al., 1992]. In three generations, the disease was inherited from the mothers in seven affected males (Fig. 1). Five had severe congenital hypotonia and died during the first year of life. Two other boys (maternal cousins) were found to have severe congenital ataxia, late-onset progressive myoclonic encephalopathy, and selective macular degeneration; brain CT-scan showed moderate cerebellar vermis hypoplasia. Linkage analysis was carried out in 12 informative relatives using 35 microsatellite markers (Généthon) evenly distributed on the X chromosome. A multipoint analysis showed a significant linkage (Z > 2) between the disease and three markers in the Xp22.33 region: DYS403 (Z = 2.37, theta = 0) which maps in the pseudoautosomal region, DXS7099 (Z = 2.45, theta = 0), and DXS7100 (Z = 2.48, theta = 0). Further linkage analysis with more telomeric markers will refine the location of this severe X-linked encephalopathy.
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Affiliation(s)
- V des Portes
- Unité INSERM 129 de Recherche en Génétique et Pathologie Moléculaires, Faculté de Médecine Cochin, Paris, France
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Schutz CK, Ives EJ, Chalifoux M, MacLaren L, Farrell S, Robinson PD, White BN, Holden JJ. Regional localization of an X-linked mental retardation gene to Xp21.1-Xp22.13 (MRX38). AMERICAN JOURNAL OF MEDICAL GENETICS 1996; 64:89-96. [PMID: 8826457 DOI: 10.1002/(sici)1096-8628(19960712)64:1<89::aid-ajmg16>3.0.co;2-o] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
A gene responsible for X-linked mental retardation with macrocephaly and seizures (MRX38) in a family with five affected males in three generations was localized to Xp21.1-p22.13 by linkage analysis. Recombination events placed the gene between DXS1226 distally and DXS1238 proximally, defining an interval of approximately 14 cM. A peak lod score of 2.71 was found with several loci in Xp21.1 (DXS992, DXS1236, DXS997, and DXS1036) at a recombination fraction of zero. The map intervals of 5 X-linked mental retardation loci, MRX2 (Xp22.1-p22.2), MRX19 (Xp22), MRX21 (Xp21.1-p22.3), MRX29 (Xp21.2-p22.1), and MRX32 (Xp21.2-p22.1), and two syndromal mental retardation loci, Partington syndrome (PRTS; Xp22) and Coffin-Lowry syndrome (CLS; Xp22.13-p22.2), overlap this region. As none of these display the same phenotype seen in the family reported here, this X-linked mental retardation locus may represent a new entity.
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Affiliation(s)
- C K Schutz
- Department of Biology McMaster University, Hamilton, Ontario, Canada
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Robledo R, Melis P, Laficara F, Marchi J, Rinaldi A, Siniscalco M, Filippi G. Further linkage evidence for localization of mutational sites for nonsyndromic types of X-linked mental retardation at the pericentromeric region. AMERICAN JOURNAL OF MEDICAL GENETICS 1996; 64:107-12. [PMID: 8826459 DOI: 10.1002/(sici)1096-8628(19960712)64:1<107::aid-ajmg18>3.0.co;2-r] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
We used several microsatellite markers scattered along the X chromosome to search for linkage relationships in a large Sardinian pedigree segregating for nonspecific X-linked mental retardation (MRX). Markers DXS573 and AR, located at chromosomal subregions Xp11.4-p11.22 and Xq11.2-q12, respectively, were found to segregate in full concordance with the disease, leading to a LOD score of 4.21 at zero recombination value. Recombination with the disease was found with markers MAOB and DXS454 located at Xp11.4-p11.3 and Xq21.1-q22, respectively; accordingly, markers distal to Xp11.4 and Xq22 also segregated independently of the disease. These findings provide strong linkage evidence in favor of the localization of one MRX mutational site in the pericentromeric region of the human X chromosome, justifying the assignment of a new symbol (MRX26) to our pedigree. Finally, on the basis of the recombinational events observed in the Xq21-q22 region, we have been able to refine the assignment of marker DXS456 to Xq21.33-q22.
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Affiliation(s)
- R Robledo
- Istituto di Genetica Molecolare del CNR, Alghero, Italy
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Gedeon AK, Glass IA, Connor JM, Mulley JC. Genetic localisation of MRX27 to Xq24-26 defines another discrete gene for non-specific X-linked mental retardation. AMERICAN JOURNAL OF MEDICAL GENETICS 1996; 64:121-4. [PMID: 8826461 DOI: 10.1002/(sici)1096-8628(19960712)64:1<121::aid-ajmg20>3.0.co;2-o] [Citation(s) in RCA: 25] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
A large family with non-specific X-linked mental retardation (MRX) was first described in 1991 [Glass et al., 1991], with a suggestion of linkage to Xq26-27. The maximum lod score was 1.60 (theta = 0.10) with the F9 locus. The localisation of this MRX gene has now been established by linkage to microsatellite markers. Peak pairwise lod scores of 4.02 and 4.01 (theta = 0.00) were attained at the DXS1114 and DXS994 loci respectively. This MRX gene is now designated MRX27 and is localised to Xq24-26 by recombination events detected by DXS424 and DXS102. This regional localisation spans 26.2 cM on the genetic background map and defines another distinct MRX interval by linkage to a specific region of the X chromosome.
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Affiliation(s)
- A K Gedeon
- Department of Cytogenetics and Molecular Genetics, Women's and Children's Hospital, Adelaide, Australia
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Gedeon AK, Donnelly AJ, Mulley JC, Kerr B, Turner G. How many X-linked genes for non-specific mental retardation (MRX) are there? AMERICAN JOURNAL OF MEDICAL GENETICS 1996; 64:158-62. [PMID: 8826466 DOI: 10.1002/(sici)1096-8628(19960712)64:1<158::aid-ajmg26>3.0.co;2-l] [Citation(s) in RCA: 52] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
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22
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Claes S, Gu XX, Legius E, Lorenzetti E, Marynen P, Fryns JP, Cassiman JJ, Raeymaekers P. Linkage analysis in three families with nonspecific X-linked mental retardation. AMERICAN JOURNAL OF MEDICAL GENETICS 1996; 64:137-46. [PMID: 8826464 DOI: 10.1002/(sici)1096-8628(19960712)64:1<137::aid-ajmg24>3.0.co;2-n] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Nonspecific X-linked mental retardation (XLMR) is a common disorder. The number of genes involved in this condition is not known, but it is estimated to be more than 10. We present a clinical and linkage study on 3 families with XLMR. All families were analyzed using highly polymorphic markers covering the X chromosome; screening for the fragile X mutation was negative. The first family (MRX 36) consisted of 1 female and 4 male patients in 3 generations and 7 healthy individuals. Considering the female as an expressing heterozygous carrier, a maximum LOD score of 3.41 was reached in region Xp21.2-Xp22.1. Considering her phenotype to be unknown, a LODmax of 1.97 was reached in the same region. The second family consisted of 5 affected and 6 healthy males with mild to borderline mental retardation. Linkage analysis using an X-linked recessive model with full penetrance and no phenocopies excluded linkage over almost the entire X chromosome. Using alternative models, including an affecteds-only analysis, a LODmax of 1.49 was found in region Xq24-28. The third family, consisting of 4 male patients with moderate mental retardation in 1 generation yielded a LODmax of 0.9 in region Xp22.13-11.3. However, even in this small pedigree, exclusion mapping was able to exclude very large parts of the X chromosome and in this way identify a likely candidate region.
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Affiliation(s)
- S Claes
- Center for Human Genetics, University of Leuven, Belgium
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23
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Abstract
A current list of all known forms of X-linked mental retardation (XLMR) and a slightly revised classification are presented. The number of known disorders has not increased because 6 disorders have been combined based on new molecular data or on clinical grounds and only 6 newly described XLMR disorders have been reported. Of the current 105 XLMR disorders, 34 have been mapped, and 18 disorders and 1 nonspecific XLMR (FRAXE) have been cloned. The number of families with nonspecific XLMR with a LOD score of > or = 2.0 has more than doubled, with 42 (including FRAXE) now being known. a summary of the localization of presumed nonspecific mental retardation (MR) genes from well-studied X-chromosomal translocations and deletions is also included. Only 10-12 nonoverlapping loci are required to explain all localizations of nonspecific MR from both approaches. These new trends mark the beginning of a significantly improved understanding of the role of genes on the X chromosome in producing MR. Continued close collaboration between clinical and molecular investigators will be required to complete the process.
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Affiliation(s)
- H A Lubs
- Department of Medical Genetics, University Hospital of Tromsø, Norway
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24
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Morava E, Storcz J, Kosztolányi G. X-linked mental retardation syndrome: three brothers with the Brooks-Wisniewski-Brown syndrome. AMERICAN JOURNAL OF MEDICAL GENETICS 1996; 64:59-62. [PMID: 8826449 DOI: 10.1002/(sici)1096-8628(19960712)64:1<59::aid-ajmg8>3.0.co;2-m] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
We report on 3 brothers with growth and mental retardation, bifrontal narrowness, short palpebral fissures, deeply set eyes with entropion, wide bulbous nose, small mouth, myopia, and spastic diplegia. The patients were born to normal and non-consanguineous parents. The similarity of our cases with those recently reported by Brooks et al. [Am J Med Genet 51:586-590, 1994] supports their suggestion that these patients are representative of a distinct entity.
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Affiliation(s)
- E Morava
- Department of Pediatrics, University Medical School, Pécs, Hungary
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25
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Abstract
The expression of X-linked genes in females heterozygous for X-linked defects can be modulated by epigenetic control mechanisms that constitute the X chromosome inactivation pathway. At least four different effects have been found to influence, in females, the phenotypic expression of genes responsible for X-linked mental retardation (XLMR). First, non-random X inactivation, due either to stochastic or genetic factors, can result in tissues in which one cell type (for example, that in which the X chromosome carrying a mutant XLMR gene is active) dominates, instead of the normal mosaic cell population expected as a result of random X inactivation. Second, skewed inactivation of the normal X in individuals carrying a deletion of part of the X chromosome has been documented in a number of mentally retarded females. Third, functional disomy of X-linked genes that are expressed inappropriately due to the absence of X inactivation has been found in mentally retarded females with structurally abnormal X chromosomes that do not contain the X inactivation center. And fourth, dose-dependent overexpression of X-linked genes that normally "escape" X inactivation may account for the mental and developmental delay associated with increasing numbers of otherwise inactive X chromosomes in individuals with X chromosome aneuploidy.
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Affiliation(s)
- H F Willard
- Department of Genetics, Case Western Reserve University School of Medicine and University Hospitals of Cleveland, OH 44106, USA
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26
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Raynaud M, Gendrot C, Dessay B, Moncla A, Ayrault AD, Moizard MP, Toutain A, Briault S, Villard L, Ronce N, Moraine C. X-linked mental retardation with neonatal hypotonia in a French family (MRX15): gene assignment to Xp11.22-Xp21.1. AMERICAN JOURNAL OF MEDICAL GENETICS 1996; 64:97-106. [PMID: 8826458 DOI: 10.1002/(sici)1096-8628(19960712)64:1<97::aid-ajmg17>3.0.co;2-n] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Linkage analysis was performed in a family with non-specific X-linked mental retardation (MRX 15). Hypotonia in infancy was the most remarkable physical manifestation. The severity of mental deficiency was variable among the patients, but all of them had poor or absent speech. Significant lod scores at a recombination fraction of zero were detected with the marker loci DXS1126, DXS255, and DXS573 (Zmax = 2.01) and recombination was observed with the two flanking loci DXS164 (Xp21.1) and DXS988 (Xp11.22), identifying a 17 cM interval. This result suggests a new gene localization in the proximal Xp region. In numerous families with non-specific X-linked mental retardation (MRX), the corresponding gene has been localized to the paracentromeric region in which a low recombination rate impairs the precision of mapping.
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Affiliation(s)
- M Raynaud
- Unité de Génétique Hospital Bretonneau, Tours, France
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27
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Wittwer B, Kircheisen R, Leutelt J, Orth U, Gal A. New X-linked mental retardation syndrome with the gene mapped tentatively in Xp22.3. AMERICAN JOURNAL OF MEDICAL GENETICS 1996; 64:42-9. [PMID: 8826447 DOI: 10.1002/(sici)1096-8628(19960712)64:1<42::aid-ajmg6>3.0.co;2-t] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
X-linked mental retardation (XLMR) is genetically heterogeneous and clinically variable. We describe a new XLMR syndrome of severe mental retardation and multiple congenital anomalies. Two sisters have (with 3 different partners) 3 severely handicapped sons. In 2 cases, oligohydramnios and intrauterine growth retardation were noted. Common anomalies included a square-shaped face, high and broad forehead, frontal bossing, downward slant of palpebral fissures, hypertelorism, epicanthic folds, long philtrum, thin upper lip, and apparently low-set ears. One boy has bilateral microphthalmos and sclerocornea, and his cousin has atrophy of the optic nerve. All 3 patients are blind and have profound statomotor and mental retardation, seizures, and a grossly abnormal electroencephalographic pattern. Additional findings are short stature, delayed bone maturation, hydronephrosis, vesicorenal reflux, cryptorchidism, clinodactyly of the 5th fingers, and transverse palmar creases. The karyotype is normal (46,XY). Segregation analysis showed perfect coinheritance between the clinical phenotype and alleles at several loci in Xp22.3, whereas recombinants were identified with marker loci from Xp22.2-qter. Analysis of multiple informative meioses suggests that the disease locus maps in Xp22.3 distal to DXS16.
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Affiliation(s)
- B Wittwer
- Institut für Humangenetik der Universität, Münster, Germany
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28
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Holinski-Feder E, Golla A, Rost I, Seidel H, Rittinger O, Meindl A. Regional localization of two MRX genes to Xq28 (MRX28) and to Xp11.4-Xp22.12 (MRX33). AMERICAN JOURNAL OF MEDICAL GENETICS 1996; 64:125-30. [PMID: 8826462 DOI: 10.1002/(sici)1096-8628(19960712)64:1<125::aid-ajmg21>3.0.co;2-o] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Two genes responsible for a nonspecific form of X-linked mental retardation (MRX28 and MRX33) were localized by linkage analysis with 40 highly polymorphic DNA markers situated along the entire the X chromosome. In family 1, the gene could be mapped within a 14-cM interval at Xq28, distal to the recombining marker DXS1113 (MRX28). The maximum LOD score was 2.75, with DXS52 at phi = .0. In family 2, the gene was localized within a 30-cM interval at Xp11.4-22.12 between the recombining markers DXS365 and MAOB, including the DMD gene (MRX33). Maximum LOD scores of 2.82 were obtained with markers DMD-STR49, DMD-DysII, CYBB, and DXS1068.
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Affiliation(s)
- E Holinski-Feder
- Abteilung Pädiatrische Genetik an der Kinderpoliklinik der Ludwig-Maximilians-Universität München, Germany
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29
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Colleaux L, May M, Belougne J, Lepaslier D, Schwartz C, Fontes M. Localisation of two candidate genes for mental retardation using a YAC physical map of the Xq21.1-21.2 subbands. J Med Genet 1996; 33:353-7. [PMID: 8733041 PMCID: PMC1050600 DOI: 10.1136/jmg.33.5.353] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
Genetic studies in families with X linked mental retardation have suggested the location of several MR genes in the human q21 region. Since the establishment of cloned resources is an essential step towards the cloning of genes involved in inherited diseases, we built a yeast artificial chromosome (YAC) contig and an STS map of this part of the X chromosome. The contig, which extends from PGK1 in Xq13.3 to DXS1002 in Xq21.2, consists of 30 YACs mapped with 21 markers and spans about 6 Mb. The YAC contig was used as a framework to localise several previously known genes and CEPH/Genethon polymorphic markers, as well as to construct a physical map of the region surrounding one of these genes. We recently localised a presumed MR locus to the region flanked by DXS233 (proximal) and CHM (distal). In the present work, the zinc finger gene, ZNF6, has been shown to lie within this region and to be highly expressed in brain, making it a good candidate MR gene. Similarly the VDAC1 gene has been mapped between DXS986 and DXS72 and its candidate gene status for the Allan-Herndon-Dudley syndrome is discussed.
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Affiliation(s)
- L Colleaux
- INSERM U406, Faculté de Médecine de La Timone, Marseille, France
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30
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De Hert M, Steemans D, Theys P, Fryns JP, Peuskens J. Lujan-Fryns syndrome in the differential diagnosis of schizophrenia. AMERICAN JOURNAL OF MEDICAL GENETICS 1996; 67:212-4. [PMID: 8723050 DOI: 10.1002/(sici)1096-8628(19960409)67:2<212::aid-ajmg13>3.0.co;2-m] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
Schizophrenia is considered to be a heterogenous disorder. Different etiopathological mechanism can be attributed to a similar clinical picture as described in DSM-III-R criteria. We present a case of a young man diagnosed on different occasions as schizophrenic with mild mental retardation. Clinical examination revealed signs and symptoms most compatible with the diagnosis of Lujan-Fryns syndrome, an X-linked mental retardation syndrome with marfanoid features, frequently associated with psychotic or other psychiatric symptoms. In all patients with symptoms of schizophrenia and mental retardation Lujan-Fryns syndrome should be considered in the differential diagnosis.
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Affiliation(s)
- M De Hert
- University Psychiatric Center St. Jozef, Kortenberg, Belgium
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31
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Simonoff E, Bolton P, Rutter M. Mental retardation: genetic findings, clinical implications and research agenda. J Child Psychol Psychiatry 1996; 37:259-80. [PMID: 8707910 DOI: 10.1111/j.1469-7610.1996.tb01404.x] [Citation(s) in RCA: 43] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
The most important genetic advances in the field of mental retardation include the discovery of the novel genetic mechanism responsible for the Fragile X syndrome, and the imprinting involved in the Prader-Willi and Angelman syndromes, but there have also been advances in our understanding of the pathogenesis of Down syndrome and phenylketonuria. Genetic defects (both single gene Mendelizing disorders and cytogenetic abnormalities) are involved in a substantial proportion of cases of mild as well as severe mental retardation, indicating that the previous equating of severe mental retardation with pathology, and of mild retardation with normal variation, is a misleading over-simplication. Within the group in which no pathological cause can be detected, behaviour genetic studies indicate that genetic influences are important, but that their interplay with environmental factors, which are also important, is at present poorly understood. Research into the joint action of genetic and environmental influences in this group will be an important research area in the future.
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Affiliation(s)
- E Simonoff
- MRC Child Psychiatry Unit and Centre for Social, Genetic and Developmental Psychiatry, Institute of Psychiatry, London, U.K
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32
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Jurenka SB, Van Allen MI. Additional case of craniofacial and digital anomalies as reported by Harrod et al. AMERICAN JOURNAL OF MEDICAL GENETICS 1996; 61:168-70. [PMID: 8669446 DOI: 10.1002/(sici)1096-8628(19960111)61:2<168::aid-ajmg13>3.0.co;2-s] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
In 1977 Harrod et al. [BD:OAS XIII (3B): 111-115] reported 2 brothers with an unusual syndrome of mental retardation, unusual facial appearance, large protruding ears, arachnodactyly, hypogenitalism, failure to thrive, and minor anomalies. We report on a 46-year-old man with striking resemblance to the children described by Harrod who also has secondary megacolon and varicose veins, suggesting a connective tissue disorder.
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Affiliation(s)
- S B Jurenka
- Provincial Institution for the Mentally Retarded, New Westminster, British Columbia, Canada
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33
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Gu XX, Decorte R, Marynen P, Fryns JP, Cassiman JJ, Raeymaekers P. Localisation of a new gene for non-specific mental retardation to Xq22-q26 (MRX35). J Med Genet 1996; 33:52-5. [PMID: 8825049 PMCID: PMC1051812 DOI: 10.1136/jmg.33.1.52] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Non-specific mental retardation (MR) is a condition in which MR appears to be the only consistent manifestation. The X linked form (MRX) is genetically heterogeneous. We report clinical, cytogenetic, and linkage data on a family with X linked non-specific MR. Two point and multi-point linkage analysis with 18 polymorphic markers, covering the entire chromosome, showed close linkage to DXS1001 and DXS425 with a maximal lod score of 2.41 at 0% recombination. DXS178 and the gene for hypoxanthine phosphoribosyl-transferase (HPRT), located in Xq22 and Xq26 respectively, flank the mutation. All other chromosomal regions could be excluded with odds of at least 100:1. To our knowledge there is currently no other non-specific MR gene mapped to this region. Therefore, the gene causing MR in this family can be considered to be a new, independent MRX locus (MRX35).
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Affiliation(s)
- X X Gu
- Centre for Human Genetics, University of Leuven, Campus Gasthuisberg, Belgium
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34
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Abstract
Knowledge of the molecular causes for genetic diseases that affect the nervous system is rapidly expanding. Especially striking has been the finding in several autosomal dominant neurodegenerative disorders that unstable expansions of trinucleotide repeats are responsible for the genetic disorder and that the length of the repeat can be correlated with the age of onset and the severity of symptoms. Phenotypic heterogeneity in many disorders associated with enzyme deficiencies can often be linked to the amount of residual enzyme activity occurring with different gene mutations. Making a specific diagnosis of a neurological disorder associated with genetically determined metabolic defects requires access to a laboratory that can assist in arranging for appropriate testing to be carried out. In some disorders such as the aminoacidurias diagnostic metabolic studies can be performed in hospital clinical chemistry laboratories. In others, such as the lysosomal storage diseases, a laboratory that carries out special lipid analyses and white blood cell enzyme assays will be necessary. DNA mutational analyses are becoming commercially available for diagnosing many disorders such as mitochondrial diseases and those conditions associated with expanded trinucleotide repeats. It may be necessary to contact individual research laboratories when confronted with a disorder that has been newly discovered or that is very rare. A computerised directory of specialised laboratories that perform disease specific testing for genetic disorders should be useful in choosing the appropriate diagnostic or research laboratory.
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Affiliation(s)
- P D Swanson
- Department of Neurology, University of Washington School of Medicine, Seattle 98195, USA
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35
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Lazzarini A, Stenroos ES, Lehner T, McKoy V, Gold B, McCormack MK, Reid CS, Ott J, Johnson WG. Short tandem repeat polymorphism linkage studies in a new family with X-linked mental retardation (MRX20). AMERICAN JOURNAL OF MEDICAL GENETICS 1995; 57:552-7. [PMID: 7573127 DOI: 10.1002/ajmg.1320570407] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
A family with X-linked recessive mental retardation (XLMR) without other obvious manifestations (MRX20) was studied with 14 short tandem repeat polymorphism (STRP) markers. Two-point lod scores above 3 were obtained with DXS1003, DXYS1, DXS3, and DXS458. A multipoint lod score of 4.25 was obtained with peak at DXS1003. Recombination events identify a 55.6 cM interval between DXS1068 and DXS454, while a one unit support interval identifies 40 cM between MAOA and DXS458.
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Affiliation(s)
- A Lazzarini
- Department of Neurology, University of Medicine and Dentistry of New Jersey, Robert Wood Johnson Medical School, New Brunswick 08903, USA
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36
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Schrander-Stumpel C, Höweler C, Jones M, Sommer A, Stevens C, Tinschert S, Israel J, Fryns JP. Spectrum of X-linked hydrocephalus (HSAS), MASA syndrome, and complicated spastic paraplegia (SPG1): Clinical review with six additional families. AMERICAN JOURNAL OF MEDICAL GENETICS 1995; 57:107-16. [PMID: 7645588 DOI: 10.1002/ajmg.1320570122] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
X-linked hydrocephalus (HSAS) (MIM *307000), MASA syndrome (MIM *303350), and complicated spastic paraplegia (SPG1) (MIM *312900) are closely related. Soon after delineation, SPG1 was incorporated into the spectrum of MASA syndrome. HSAS and MASA syndrome show great clinical overlap; DNA linkage analysis places the loci at Xq28. In an increasing number of families with MASA syndrome or HSAS, mutations in L1CAM, a gene located at Xq28, have been reported. In order to further delineate the clinical spectrum, we studied 6 families with male patients presenting with MASA syndrome, HSAS, or a mixed phenotype. We summarized data from previous reports and compared them with our data. Clinical variability appears to be great, even within families. Problems in genetic counseling and prenatal diagnosis, the possible overlap with X-linked corpus callosum agenesis and FG syndrome, and the different forms of X-linked complicated spastic paraplegia are discussed. Since adducted thumbs and spastic paraplegia are found in 90% of the patients, the condition may be present in males with nonspecific mental retardation. We propose to abandon the designation MASA syndrome and use the term HSAS/MASA spectrum, incorporating SPG1.
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Affiliation(s)
- C Schrander-Stumpel
- Division of Clinical Genetics, University of Limburg, Maastricht, The Netherlands
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37
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Gibbons RJ, Picketts DJ, Villard L, Higgs DR. Mutations in a putative global transcriptional regulator cause X-linked mental retardation with alpha-thalassemia (ATR-X syndrome). Cell 1995; 80:837-45. [PMID: 7697714 DOI: 10.1016/0092-8674(95)90287-2] [Citation(s) in RCA: 416] [Impact Index Per Article: 14.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
The ATR-X syndrome is an X-linked disorder comprising severe psychomotor retardation, characteristic facial features, genital abnormalities, and alpha-thalassemia. We have shown that ATR-X results from diverse mutations of XH2, a member of a subgroup of the helicase superfamily that includes proteins involved in a wide range of cellular functions, including DNA recombination and repair (RAD16, RAD54, and ERCC6) and regulation of transcription (SW12/SNF2, MOT1, and brahma). The complex ATR-X phenotype suggests that XH2, when mutated, down-regulates expression of several genes, including the alpha-globin genes, indicating that it could be a global transcriptional regulator. In addition to its role in the ATR-X syndrome, XH2 may be a good candidate for other forms of X-linked mental retardation mapping to Xq13.
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Affiliation(s)
- R J Gibbons
- Medical Research Council Molecular Haematology Unit, John Radcliffe Hospital, Headington, Oxford, England
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38
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Villard L, Gecz J, Colleaux L, Lossi AM, Chelly J, Ishikawa-Brush Y, Monaco AP, Fontes M. Construction of a YAC contig spanning the Xq13.3 subband. Genomics 1995; 26:115-22. [PMID: 7782069 DOI: 10.1016/0888-7543(95)80089-5] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
The loci involved in several X-linked mental retardation syndromes have been linked to the pericentromeric region of the X chromosome long arm (Xq12-q21). To isolate candidate genes for these diseases, we set up the construction of YAC contigs spanning this region. Two of these syndromes (the Juberg-Marsidi syndrome and the alpha-thalessemia mental retardation syndrome) have been recently linked, with high lod scores, to polymorphic probes previously assigned to Xq13.3. We therefore constructed a first YAC contig, encompassing this band, from DXS441 to PGK1. The physical map, deduced from the isolated clones, extends over 2.1 Mb of genomic DNA. Restriction analysis of the YAC contig allowed us to map precisely the loci previously assigned to that chromosomal region and to define their relative order. The validity of this physical map has been checked by comparing Sfi I digests of the YACs to genomic fragments obtained with the same enzyme. A cDNA selection approach, already performed with a previous partial contig, has been extended to cover the whole region.
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Affiliation(s)
- L Villard
- INSERM U406, Faculté de Médecine de La Timone, Marseille, France
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