Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0026827 (hypotonia)
 5,860 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

To determine which regions of chromosome 21 are involved in the pathogenesis of specific features of Down syndrome, we analysed, phenotypically and molecularly, 10 patients with partial trisomy 21. Six minimal regions for 24 features were defined by genotype-phenotype correlations. Nineteen of these features could be assigned to just 2 regions: short stature, joint hyperlaxity, hypotonia, major contribution to mental retardation and 9 anomalies of the face, hand and foot to the region D21S55, or Down syndrome chromosome region (DCR), located on q22.2 or very proximal q22.3, and spanning 0.4-3 Mb; 6 facial and dermatoglyphic anomalies to the region D21S55-MX1, including the DCR and spanning a maximum of 6 Mb on q22.2 and part of q22.3. Thus, the complex phenotype that constitutes Down syndrome may in large part simply result from the overdosage of only one or a few genes within the DCR and/or region D21S55-MX1.
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PMID:Molecular mapping of twenty-four features of Down syndrome on chromosome 21. 805 22

Down syndrome (DS) is a major cause of mental retardation and congenital heart disease. Besides a characteristic set of facial and physical features, DS is associated with congenital anomalies of the gastrointestinal tract, an increased risk of leukemia, immune system defects, and an Alzheimer-like dementia. Moreover, DS is a model for the study of human aneuploidy. Although usually caused by the presence of an extra chromosome 21, subsets of the phenotypic features of DS may be caused by the duplication of small regions of the chromosome. The physical map of chromosome 21 allows the molecular definition of the regions duplicated in these rare cases of partial trisomy. As a first step in identifying the genes responsible for individual DS features and their pathophysiology, a panel of cell lines derived from 16 such individuals has been established and the molecular break points have been determined using fluorescence in situ hybridization and Southern blot dosage analysis of 32 markers unique to human chromosome 21. Combining this information with detailed clinical evaluations of these patients, we have now constructed a "phenotypic map" that includes 25 features and assigns regions of 2-20 megabases as likely to contain the genes responsible. This study provides evidence for a significant contribution of genes outside the D21S55 region to the DS phenotypes, including the facies, microcephaly, short stature, hypotonia, abnormal dermatoglyphics, and mental retardation. This strongly suggests DS is a contiguous gene syndrome and augurs against a single DS chromosomal region responsible for most of the DS phenotypic features.
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PMID:Down syndrome phenotypes: the consequences of chromosomal imbalance. 819 71

A 3-year-old girl with Down syndrome was admitted to our hospital, associated with hypotonia and dyspnea. She presented frog-posture and shallow breathing. The blood gas analysis revealed hypercapnic acidosis with pH 7.371, PO2 74.6 mmHg, PCO2 52.6 mmHg, and BE 3.5. The cervical X-ray films with flexion and extension of head showed anterior dislocation of the atlanto-axial articulation. Magnetic resonance imaging clearly showed a severe cord compression between C1 and C2. In children, spinal cord compression induced by dislocation of the atlanto-axial articulation is very rare. However, we should take into consideration of this insidious risk associated often with Down syndrome.
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PMID:[A female child with Down syndrome complicated by spinal cord compression by atlanto-axial dislocation]. 841 98

We report on an aneuploidy syndrome due to the unbalanced segregation of a familial translocation (4;21)(p16.3;q22.1) causing a partial 4p monosomy and a partial 21q trisomy. The three affected children presented with severe failure to thrive, short stature, microcephaly, profound hypotonia, and mental retardation. The face, very similar in the three children, is characterized by frontal bossing, upslanting of the palpebral fissures, short nose, and deep set ears, giving the overall appearance of the Down syndrome. The molecular study has defined the aneuploid segment on both 4p and 21q. Most of the Down syndrome critical region was found to the trisomic, while only part of the candidate Wolf-Hirschhorn syndrome critical region was deleted, suggesting that this region is not critical for the major malformations characteristic for WHS.
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PMID:Molecular and cytogenetic characterization of a recurrent unbalanced translocation (4;21)(p16.3;q22.1): relevance to the Wolf-Hirschhorn and Down syndrome critical regions. 872 87

Most cases of Down syndrome (DS) result from a supernumerary chromosome 21; however, there are rare cases in which DS is due to partial trisomy of chromosome 21, involving various segments of the chromosome. The characterization of cases of DS that are due to partial trisomy 21 allows the phenotype to be correlated with the genotype. We present a case with features of DS and a partial trisomy of chromosome 21 inherited from a paternal balanced translocation involving chromosomes 13 and 21. Fluorescence in situ hybridization analysis using yeast artificial chromosome (YAC) probes mapped the breakpoint to 21q22.1, within YAC 230E8, which contains markers CBR, D21S333 and D21S334. Further mapping using cosmids positioned the breakpoint proximal to CBR. The patient was also monosomic for the distal portion of chromosome 13 (q33-qter). Many phenotypic features of DS were present including hypotonia, flat occiput, flat facies, up-slanted palpebral fissures, epicanthic folds, flat nasal bridge, macroglossia, open mouth, small ears and a heart murmur. This case further supports the contention that the majority of the phenotypic features of DS map to 21q22-qter and further refines the location of some of them. In addition to the DS phenotype, the patient had a prominent upper maxilla with protruding upper incisors, and low levels of the coagulation factors VII and X, consistent with a syndrome resulting from monosomy 13q33-qter. Since some features overlap between the two syndromes, including severe mental retardation, it is unclear to what extent monosmy for 13q33-qter, trisomy for 21q22.1-qter, or a combination of both, contributed to the common features of the phenotype.
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PMID:YAC and cosmid FISH mapping of an unbalanced chromosomal translocation causing partial trisomy 21 and Down syndrome. 879 23

The patient presented with the typical features of Down syndrome; hypotonia, brachycephaly, flattened occiput, bilateral prominent medical epicanthic folds, flat nasal bridge, protruding tongue, low-set dysplastic ears, short broad hands, bilateral clinodactyly and simian crease. The karyotype of this child was originally reported as normal. High-resolution chromosomes revealed extra material on the long arm of chromosome 18. The mother's karyotype showed a reciprocal translocation between the long arm of 18 and the long arm of 21 at band q23 and q22.1, respectively. FISH performed separately with two different 21q cosmid probes gave two signals on the mother's metaphases and three signals on the proband. These findings confirmed that the proband is trisomic for the long arm of chromosome 21 at loci D21S65 and D21S19.
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PMID:Subtle translocation (18;21) confirmed by FISH in a patient with Down syndrome. 900 38

The identification and functional characterization of genes on chromosome 21 is a necessary step to understand the pathogenesis of the various phenotypic anomalies that affect Down syndrome patients. Using direct cDNA selection we have identified a new gene, SH3BGR, that maps to 21q22.3, proximal to HMG14, and is differentially expressed in heart and skeletal muscle. SH3BGR encodes a novel protein that is characterized by the presence of a proline-rich region containing the consensus sequence for a SH3-binding domain and by an acidic carboxyl-terminal region containing a glutamic acid-rich domain predicted to assume a coiled coil. The presence of two functional domains involved in protein-protein interactions suggests that SH3BGR could be part of a multimeric complex. Its overexpression might alter specific functions of muscular tissue and therefore take part in the pathophysiology of muscular hypotonia in Down syndrome.
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PMID:Cloning a new human gene from chromosome 21q22.3 encoding a glutamic acid-rich protein expressed in heart and skeletal muscle. 905 Sep 28

The Down syndrome chromosome region-1 (DCR1) on subband q22.2 of chromosome 21 is thought to contain genes contributing to many features of the trisomy 21 phenotype, including dysmorphic features, hypotonia, and psychomotor delay. Isolation, mapping, and sequencing of trapped exons and captured cDNAs from cosmids of this region have revealed the presence of a gene (KCNJ15) encoding a potassium (K+) channel belonging to the family of inward rectifier K+ (Kir) channels. The amino acid sequence deduced from the 1125-bp open reading frame indicates that this gene is a member of the Kir4 subfamily; it has been named Kir4.2. It is expressed in kidney and lung during human development and in several adult tissues including kidney and brain. After Kir3.2 (GIRK2), Kir4.2 is the second K+ channel gene of this type described within the DCR1.
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PMID:A new inward rectifier potassium channel gene (KCNJ15) localized on chromosome 21 in the Down syndrome chromosome region 1 (DCR1). 929 42

We have isolated, mapped and sequenced the 5' promoter region of the human SH3BGR (SH3-Binding Glutamine Rich) gene located in the Down syndrome region-2, between markers D21S55 and MX1 of human chromosome 21. This region has been postulated as the minimal region for congenital heart disease and 6 facial and dermatoglyphic features present in Down syndrome. The SH3BGR gene is expressed in fetal and adult heart and in skeletal muscle and therefore it is a candidate gene for the congenital heart defect and muscle hypotonia. The 5' region of the gene has been positioned in a 115 kb PAC/cosmid contig with full EcoRI/SmaI restriction map covering cosmid pockets 122-123 as well as cosmid pocket 124 located between markers D21S268 and D21S220. Sequencing of the SH3BGR promoter region has allowed the identification of several potential regulatory elements of this candidate gene for the congenital heart disease and other potential DS features. Several of the elements identified are also present in other muscle-expressed genes.
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PMID:High-resolution physical map and identification of potentially regulatory sequences of the human SH3BGR located in the Down syndrome chromosomal region. 942 70

The region of chromosome 21 between genes CBR and ERG (CBR-ERG region), which spans 2.5 Mb on 21q22.2, has been defined by analysis of patients with partial trisomy 21. It contributes significantly to the pathogenesis of many characteristics of Down syndrome, including morphological features, hypotonia, and mental retardation. Cosmid contigs covering 80% of the region were constructed and EcoRI maps produced. These cosmids were used for exon trapping and cDNA selection from three cDNA libraries (fetal brain, fetal liver, and adult skeletal muscle). Isolated exons and cDNAs were mapped on the EcoRI map, organized into contigs, sequenced, and used as probes for Northern blot analysis of RNA from fetal and adult tissues. We identified 27 genuine or highly probable transcriptional units evenly distributed along the CBR-ERG region. Eight of the transcriptional units are known genes.
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PMID:Transcriptional map of the 2.5-Mb CBR-ERG region of chromosome 21 involved in Down syndrome. 950 11


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