Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UMLS:C0025362 (mental retardation)
 15,878 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A service has been developed in Saskatchewan to make available the results of studies of human chromosomes, the material being forwarded to the laboratory by local transport facilities. During the first year of this project chromosome studies were requested for five doubtful cases of trisomy-21 (two were found to be normal) and for 20 definite cases of trisomy-21 in young patients (two had translocations but the parents of both these children had normal karyotypes). Eleven confirmed cases of Turner's syndrome, two of Klinefelter's syndrome, and one each of the D and E syndromes were also studied. The largest group for which studies were requested comprised 36 patients with mental retardation; only two abnormal karyotypes were encountered in this group.
 ...
PMID:A service for human chromosome studies in Saskatchewan. 590 45

A balanced de novo (X;9) translocation was observed in a patient with progressive muscular dystrophy of Duchenne's type (DMD), Turner's syndrome, epilepsy and mental retardation. The involvement of the paternal X is suggested. The assignment of the gene locus for DMD is confirmed on Xp21.
 ...
PMID:Turner's syndrome and Duchenne muscular dystrophy in a girl with an X; autosome translocation. 633 82

Small ring X chromosomes were first described in mosaic karyotypes of females with the relatively benign phenotype of Turner syndrome. The presence of these rings in association with more severe phenotypes including mental retardation has raised the possibility that they lack sequences necessary for X chromosome inactivation, specifically genes within the X inactivation center (XIC) essential for cis X-inactivation. We recently showed that ring X chromosomes ascertained because of the severe phenotype do not express XIST, a candidate for the relevant gene, and that they are in fact active chromosomes. We now report studies of the genetic content of 11 of these ring X chromosomes (9 associated with severe phenotypes). Our results indicate that these chromosomes contain contiguous segments of DNA and have variable proximal and distal breakpoints and some include mainly long arm or mainly short arm sequences. As expected for ring chromosomes, they lack telomeric sequences. Many of the ring chromosomes lack the XIST locus, consistent with XIST being necessary for cis inactivation. However, the breakpoints in four ring chromosomes that have XIST sequences but do not express XIST suggest that other sequences within the XIC distal to XIST as it is now defined are also needed.
 ...
PMID:Molecular characterization of tiny ring X chromosomes from females with functional X chromosome disomy and lack of cis X inactivation. 766 67

We present a large review of 446 cases of paracentric inversions (PAI), including 120 new cases, to assess their incidence, distribution, inheritance, modes of ascertainment, interchromosomal effects, viable recombinant offspring, and clinical relevance. All 23 autosomes and sex chromosomes had inversions. However, none were identified in chromosome arms 18p, 19q, 20q, and Yp. PAI were most commonly reported in chromosomes 1, 3, 5, 6, 7, 11, and 14 and less frequently in chromosomes 4, 16, 17, 18, 19, 20, 21, 22, and Y. Inversions were most common in chromosome arms 6p, 7q, 11q, and 14q and observed least in chromosome arms 2p, 2q, 3q, 4q, and 6q. Frequently encountered breakpoints included 3(p13p25), 6(p12p23), 6(p12p25), 7(q11q22), and 11(q21q23). Ascertainment was primarily incidental (54.5%), mental retardation and/or congenital anomalies (22.2%), spontaneous abortions (11.4%), associations with syndromes (3.0%), and infertility (2.0%) accounted for the remainder. Ascertainment was neither related to the length of the inverted segment nor to specific inversions except for PAI of Xq which often presented with manifestations of Ullrich-Turner syndrome. Sixty-six percent of PAI were inherited while 8.5% were de novo. Recombination was observed in 17 cases, 15 of which resulted in a monocentric chromosomal deletion or duplication. No common factors were identified that suggested a tendency towards recombination. The incidence of viable recombinants was estimated to be 3.8%. This review documents that PAI are perhaps more commonly identified than suggested in previous reviews. Despite the possible bias of ascertainment in some cases, there may be associated risks with PAI that require further examination. Our data suggest that PAI carriers do not appear to be free of risks of abnormalities or abnormal progeny and caution is recommended when counseling.
 ...
PMID:Paracentric inversions in humans: a review of 446 paracentric inversions with presentation of 120 new cases. 905 65

Small marker chromosomes (SMC) associated with severe Turner syndrome (TS) variants often represent reduced X chromosomes lacking the X inactivation center (XIC), perturbed dosage compensation, and unbalanced gene expression. A TS patient with mental retardation (MR), unusually short stature, facial and limb malformations, and karyotypic mosaicism involving SMCs is described. Cytogenetic and fluorescence in situ hybridization (FISH) studies of blood and lymphoblastoid cells showed that the SMC was X-chromosome derived, contained a functional centromere, and had ring formation. Karyotypes of 45/46,X,r(X) in blood cells and 45,X/46,-XX/46,X,r(X)/47,X,r(X), + r(X) in fibroblasts were found. Late-replication of the SMC was inconclusive, but the X inactivation specific transcript (XIST) locus within XIC was demonstrated by fluorescent in situ hybridization (FISH). Mechanisms are reviewed that can account for our patient's unusual TS phenotype.
 ...
PMID:An atypical Turner syndrome patient with ring X chromosome mosaicism. 776 70

Four cases having mosaicism for a small marker or ring [45,X/46,X,+mar or 45,X/46,X,+r] chromosome were ascertained following cytogenetic studies requested because of minor anomalies (cases 1, 3, and 4) and/or short stature (cases 2 and 4). While all 4 cases had traits typical of Ullrich-Turner syndrome (UTS), cases 1, 3, and 4 had manifestations not usually present in UTS, including unusual facial appearance, mental retardation/developmental delay (MR/DD) (cases 3 and 4), and syndactylies (case 1). The facial appearances of cases 1 and 3 were similar yet distinct from that of case 4. Using fluorescence in situ hybridization (FISH), each of the markers in these 4 cases was identified as having been derived from an X chromosome. The level of mosaicism for the mar/r(X) cell line in these cases varied from 70% (case 1) to 16% (case 4) but was not apparently correlated with the presence of MR/DD. Replication studies demonstrated a probable early replication pattern for the mar/r(X) in cases 1, 3, and 4, while the marker in case 2 was apparently late replicating. To date, 41 individuals having mosaicism for a small mar/r(X) chromosome have been described. Interestingly, most of the 14 individuals having a presumedly active mar/r(X) demonstrated clinical findings atypical of UTS, including abnormal facial changes (11) and MR/DD (13). MR was noted most frequently in those cases having at least 50% mosaicism for the marker or ring. In contrast, atypical UTS facial appearance or MR/DD was not noted in 14 of the 16 cases with UTS who carried a probable late replicating marker or ring. In conclusion, although the phenotype of 45,X/46,X,mar/r(X) individuals appears to be influenced by the genetic content and degree of mosaicism for the mar/r(X), the most significant factor associated with MR/DD appears to be the activity status of the mar/r(X) chromosome. Thus, our 4 cases provide further support for the hypothesis that a lack of inactivation of a small mar/r(X) chromosome may be a factor leading to the MR and other phenotypic abnormalities seen in this subset of individuals having atypical UTS.
 ...
PMID:Mental retardation and Ullrich-Turner syndrome in cases with 45,X/46X,+mar: additional support for the loss of the X-inactivation center hypothesis. 780 98

Mental retardation and a constellation of congenital malformations not usually associated with Turner syndrome are seen in some females with a mosaic 45,X/46,X,r(X) karyotype. Studies of these females show that the XIST locus on their tiny ring X chromosomes is either not present or not expressed. As XIST transcription is well correlated with inactivation of the X chromosome in female somatic cells and spermatogonia, nonexpression of the locus even when it is present suggests that these chromosomes are transcriptionally active. We examined the transcriptional activity of ring X chromosomes lacking XIST expression (XISTE-), from three females with severe phenotypes. The two tiny ring X chromosomes studied with an antibody specific for the acetylated isoforms of histone H4 marking transcribed chromatin domains were labeled at a level consistent with their being active. We also examined tow of the XISTE- ring chromosomes to determine whether genes that are normally silent on an inactive X are expressed from these chromosomes. Analyses of hybrid cells show that TIMP, ZXDA, and ZXDB loci on the proximal short arm, and AR and PHKA1 loci on the long arm, are well expressed from the tiny ring X chromosome lacking XIST DNA. Studies of the ring chromosome that has XIST DNA but does not transcribe it show that its AR allele is transcribed along with the one on the normal X allele.(ABSTRACT TRUNCATED AT 250 WORDS)
 ...
PMID:The severe phenotype of females with tiny ring X chromosomes is associated with inability of these chromosomes to undergo X inactivation. 807 92

The molecular characterisation of chromosomal aberrations in Xp22.3 has established the map position of several genes with mutations resulting in diverse phenotypes such as short stature (SS), chondrodysplasia punctata (CDPX), mental retardation (MRX), ichthyosis (XLI), and Kallmann syndrome (KAL). We describe the clinical symptoms of a patient with a complex syndrome compatible with all these conditions plus ocular albinism (OA1). He has a terminal Xp deletion of at least 10 Mb of DNA. Both the mother and sister of the patient are carriers of the deletion and show a number of traits seen in Turner's syndrome. The diagnosis of ocular albinism was confirmed in the patient and his mother, who shows iris translucency, patches and streaks of hypopigmentation in the fundus, and macromelanosomes in epidermal melanocytes. By comparative deletion mapping we can define a deletion interval, which locates the OA1 gene proximal to DXS143 and distal to DXS85, with the breakpoints providing valuable starting points for cloning strategies.
 ...
PMID:Analysis of a terminal Xp22.3 deletion in a patient with six monogenic disorders: implications for the mapping of X linked ocular albinism. 823 Jan 60

In a description of 8 girls who had Ullrich-Turner syndrome (UTS) with a small r(X), mental retardation, and other unusual findings, it was hypothesized that the distinctive phenotype was associated with the loss of the X inactivation center from the r(X) and lack of genetic inactivation of the ring [Van Dyke et al., 1992]. Here, we present a 17-year-old young woman with 45,X/46,X,r(X)(?p11q13) mosaicism, Ullrich-Turner syndrome, and normal intelligence. In situ hybridization with the X-centromere DNA probe DXZ1 (Oncor, Inc., Gaithersburg, MD) was performed on previously G-banded slides, and the probe hybridized to the centromere regions of the normal X and the ring. The r(X) appears to be inactivated since a buccal smear demonstrated 5% Barr bodies. Furthermore, DAPI stain and FISH analysis with the X-centromere DNA probe DXZ1 was employed to distinguish the inactive X from the active X, and verified the presence of a sex chromatin mass in fibroblasts. These observations are consistent with the active-ring-X-and-mental-retardation hypothesis since the ring in this patient, although very small, appears to be normally inactivated and she has normal intelligence.
 ...
PMID:X-inactivation pattern in an Ullrich-Turner syndrome patient with a small ring X and normal intelligence. 825 12

Three patients with mosaicism and a cell line containing a small ring (X) chromosome are described. Their phenotype is similar to several previously reported patients with a 45,X/46,X,r(X) karyotype and a phenotype far more severely affected than expected in Turner's syndrome. The clinical picture includes mental retardation, a facial appearance reminiscent of the Kabuki make up syndrome, and limb anomalies. Some of the patients also had streaky hyperpigmentation of the skin in a pattern suggesting dermal mosaicism. It has been hypothesised that the severe phenotype might be the result of the small r(X) chromosome remaining active. However, there is little critical evidence to support this suggestion, while there is considerable evidence against it, including (1) a similar phenotype in 45,X/46,X,r(Y) patients, (2) the late replication of some of the small r(X) chromosomes associated with this phenotype, and (3) the expression of XIST in some of the affected patients.
 ...
PMID:Three patients with ring (X) chromosomes and a severe phenotype. 832 92


<< Previous 1 2 3 4 5 6 7 Next >>