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Results for “X-Linked Intellectual Disability”

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At least 181 records · Page 10Linked to original sources
PubMed1992

X-linked alpha-thalassemia/mental retardation (ATR-X) syndrome: localization to Xq12-q21.31 by X inactivation and linkage analysis.

We have examined seven pedigrees that include individuals with a recently described X-linked form of severe mental retardation associated with alpha-thalassemia (ATR-X syndrome). Using hematologic and molecular approaches, we have shown that intellectually normal female carriers of this syndrome may be identified by the presence of rare cells containing HbH inclusions in their peripheral blood and by an extremely skewed pattern of X inactivation seen in cells from a variety of tissues. Linkage analysis has localized the ATR-X locus to an interval of approximately 11 cM between the loci DXS106 and DXYS1X (Xq12-q21.31), with a peak LOD score of 5.4 (recombination fraction of 0) at DXS72. These findings provide the basis for genetic counseling, assessment of carrier risk, and prenatal diagnosis of the ATR-X syndrome. Furthermore, they represent an important step in developing strategies to understand how the mutant ATR-X allele causes mental handicap, dysmorphism, and down-regulation of the alpha-globin genes.

Dosage Compensation, Genetic↗
PubMed1991

Linkage of the gene for an X-linked mental retardation disorder to a hypervariable (AGAT)n repeat motif within the human hypoxanthine phosphoribosyltransferase (HPRT) locus (Xq26).

We recently reported a new X-linked mental retardation (XLMR) disorder in a four-generation family of Dutch descent. Features included Dandy-Walker malformation, basal ganglia disease, and seizures. Twenty-six family members, including two living affected males and two obligate carriers, were available for study. No evidence of linkage was observed between the disease locus and RFLPs from several X-chromosome regions, including Xp21-p22 (13 markers), proximal Xq (four markers), and Xq28 (three markers). However, a new hypervariable short tandem repeat (STR) within the HPRT gene at Xq26 showed positive linkage to the disease locus, with a maximum lod score of 2.19 at a recombination fraction of 0. A second hypervariable marker in Xq26, the dinucleotide repeat XL90A3 (DXS425), showed a lod score of .84 at a recombination fraction of .11. Both the HPRT and DXS425 markers were typed in 40 CEPH families, and subsequent multipoint linkage analysis showed the following order: Xcen-DXS425-(HPRT,XLMR)-F9-qter. HPRT and these flanking markers are therefore useful for carrier detection and prenatal diagnosis in this family. This study illustrates that hypervariable STRs will be powerful tools for linkage analysis and genetic diagnosis, particularly when relatively small families are involved.

Adenine Nucleotides↗
PubMed1991

Abnormal protein in the cerebrospinal fluid of patients with a submicroscopic X-chromosomal deletion associated with Norrie disease: preliminary report.

Norrie disease is an X-linked recessive disorder characterized by congenital blindness and, in many cases, mental retardation. Some Norrie disease cases have been shown to be associated with a submicroscopic deletion in chromosomal region Xp11.3. Cerebrospinal fluid (CSF) was collected from four male patients with an X-chromosomal deletion associated with Norrie disease. CSF proteins were resolved using two-dimensional gel electrophoresis and then analyzed by computer using the Elsie V program. Our analysis revealed a protein that appears to be altered in patients with Norrie disease deletion.

Blindness↗
PubMed1990

On the nosology of moderate mental retardation with special attention to X-linked mental retardation. A diagnostic genetic survey of 274 institutionalized moderately mentally retarded men.

In this paper we report the results of a genetic-diagnostic survey of 274 institutionalized moderately mentally retarded adult males and compare these data with those from our previous studies in the severely mentally retarded and from a comparable population of 262 institutionalized moderately mentally retarded males and females (The Borgenstein experience). Special attention is paid to the nosology of X-linked mental retardation and familial mental retardation in general.

Belgium↗
PubMed1990

Allan-Herndon syndrome. II. Linkage to DNA markers in Xq21.

The original family with the Allan-Herndon type of X-linked mental retardation has been investigated for linkage by using DNA probes spanning the length of the X chromosome. Available for study, over 3 generations, were 13 affected males, three obligate carriers, and three normal sons of the obligate carriers. Initial disease-to-marker analysis suggested linkage to three markers (DXYS2 [7b], DXS250 [GMGX22], and DXS3 [p19-2]) located in Xq21. All three exhibited the same maximum lod score of 2.3 at a maximum theta of .05. Multipoint analysis using LINKMAP and a set of four DNA markers (DXYS1-DXYS2-DXS3-DXS94) gave a multipoint lod score of 3.58 for a location of the Allan-Herndon syndrome near locus DXYS1 (pDP34). Therefore, our data indicate that the gene for the Allan-Herndon syndrome is likely located in Xq21.

Abnormalities, Multiple↗
PubMed1989

[Genetic mapping of chromosome X: known localizations].

To be a linkage between the clinician and the molecular biologist is the aim of this paper. All the known genes on the X chromosome are usually reported in most of the human gene mapping catalogs. Here, X-linked diseases precisely mapped on the X chromosome are classified by systems. Gene mapping of the phenotypes is given for each system.

Bone Diseases↗
PubMed1987

Efficient isolation of X chromosome-specific single-copy probes from a cosmid library of a human X/hamster hybrid-cell line: mapping of new probes close to the locus for X-linked mental retardation.

We isolated X-chromosomal DNA probes from a cosmid library constructed from a single human X/hamster hybrid-cell line (C12D). One hundred human clones were isolated and used to construct a pool of X-chromosomal DNA. This DNA was digested into 0.15-2-kb fragments and subcloned into plasmids allowing the rapid characterization of new single-copy probes. These were regionally mapped and used for the detection of restriction-site polymorphisms. Together with a series of subcloned probes from individually isolated cosmids, we found seven polymorphic probes among 53 tested. Thirty-one of the probes were physically localized to different regions of the X chromosome. Four polymorphic probes map to Xq27-Xq28: DXS102 (cX38.1), DXS105(cX55.7), DXS107(cpX234), and DXS134(cpX67). These were genetically mapped by multipoint analysis relative to previously characterized loci, a mapping that resulted in the following order: DXYS1, DXS107, DXS51/DXS102, F9, DXS105, Fra-X, F8/DXS52, DXS15, DXS134. The mapping of DXS105 between F9 and Fra-X makes this probe useful for Fra-X analysis. For the linkage between FraX and DXS105, a maximum lod score of 5.01 at 4 cMorgans has been obtained in one large Dutch pedigree.

Animals↗
PubMed1987

DNA studies of X-linked mental retardation associated with a fragile site at Xq27.3.

The fragile-X mental retardation syndrome (FRAX-MR) is one of the most prevalent X-linked diseases. In affected males and in a proportion of carrier females a fragile site at Xq27.3 [fra (X)] is detected when the lymphocytes are cultured under conditions of thymidine deprivation. The fra (X) analysis can be used in the diagnosis of only 56% of carrier females (13, 14) and prenatal diagnosis by this method is not always feasible, thus making genetic counselling of affected families difficult, and sometimes impossible. We have analysed FRAX-MR families using RFLP and four DNA probes from Xq27-Xq28. Estimation of the recombination fraction indicates that the proximal probe F9 is not significantly linked to the FRAX-MR locus while the three distal probes F8, DXS52 and DXS15 show linkage. These probes could be used in the diagnosis of FRAX-MR in those families that do not show evidence for recombination. Used in conjunction with the fra (X) analysis, the segregation studies with these probes should improve the genetic counselling of the FRAX-MR syndrome and should be useful for the genetic and molecular analysis of this unique disease.

Chromosome Fragile Sites↗
PubMed1988

A systematic cytogenetic study of a population of 1170 mentally retarded and/or behaviourly disturbed patients including fragile X-screening. The Hondsberg experience.

A cytogenetic study was performed in a population of 1170 mentally retarded and/or behaviourly disturbed patients of the Hondsberg Institute in the south of the Netherlands. The cytogenetic data are presented and discussed. In all patients chromosomal evaluation was performed with Giemsa-banding and Quinacrine fluorescence, and additional banding techniques were performed whenever they were necessary to clarify the chromosomal abnormality. A fragile X screening with M199 cultures was performed in 311 males. In 22.1% of the patients a chromosomal basis was found for their developmental retardation: 14.3% Down syndrome patients, 6.1% other chromosomal abnormalities (mainly partial autosomal trisomies and monosomies and sex-chromosome abnormalities). In 24 males, through 21 index patients, a positive fragile X screening was found, i.e. 6.7% of the screened population and 1.8% of the total population. These results indicate that the diagnostic contribution of the fragile X screening is numerically of equal importance as are advanced chromosome banding techniques, and its contribution to the diagnosis of fragile X syndrome in one index male patient in general leads to the detection of several female relatives at risk to be carrier of this X-linked recessively inherited condition. The causal relationship between the occurrence of mental retardation and chromosomal aberration in genera i.e. autosomal trisomies, partial autosomal trisomies and monosomies, and Xq27-28 fragility is well established and is, to some extent, easy to understand. Whether carriers of other chromosomal rearrangements, mainly of balanced reciprocal and Robertsonian translocations, small extra chromosomes, paracentric inversions and chromosomal variants, have increased risk for mental handicap and/or congenital malformations in their progeny, remains unclear at the present time. Some of these residual problems and questions are discussed in the perspective of their importance for genetic counseling. Detailed data will be presented about the mental development and psychological profile of patients with these different types of chromosomal abnormalities and rearrangements.

Chromosome Aberrations↗
PubMed1977

X-linked recessively inherited non-specific mental retardation. Report of a large family.

A large kindred is described in which 22 males and 3 females show non-specific mental retardation with impaired speech. An X-linked recessive is the most likely mode of inheritance of this condition. Similar families have been described in the literature, characteristic physical abnormalities are absent and performance I.Q. tends to be higher than verbal I.Q. This possible heterogenous condition may be a major individual cause of mental deficiency in males, and may account for the excess of male retardates in the population.

Adolescent↗
PubMed1979

Familial X-linked mental retardation, verbal disability, and marker X chromosomes.

Cytogenetic and verbal studies were done on members of four families with non-specific X-linked mental retardation. Cytogenetic analysis was done using media 199 and GTG-banding; one family had a marker X with a fragile site in band Xq27 or 28. Preliminary results indicate variation of culture conditions can effect the frequency of the marker X. A generalized language disability was found which tended to concentrate in the areas of auditory reception, auditory sequential memory, visual closure and grammatic closure. Articulation errors involved the same sounds which are late in normal development and occur most frequently in both the general population and a Down syndrome population.

Chromosome Banding↗