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

Ataxia with oculomotor apraxia (AOA) is characterized by early-onset cerebellar ataxia, ocular apraxia, early areflexia, late peripheral neuropathy, slow progression, severe motor handicap, and absence of both telangiectasias and immunodeficiency. We studied 13 Portuguese families with AOA and found that the two largest families show linkage to 9p, with LOD scores of 4.13 and 3.82, respectively, at a recombination fraction of 0. These and three smaller families, all from northern Portugal, showed homozygosity and haplotype sharing over a 2-cM region on 9p13, demonstrating the existence of both a founding event and linkage to this locus, AOA1, in the five families. Three other families were excluded from this locus, demonstrating nonallelic heterogeneity in AOA. Early-onset cerebellar ataxia with hypoalbuminemia (EOCA-HA), so far described only in Japan, is characterized by marked cerebellar atrophy, peripheral neuropathy, mental retardation, and, occasionally, oculomotor apraxia. Two unrelated Japanese families with EOCA-HA were analyzed and appeared to show linkage to the AOA1 locus. Subsequently, hypoalbuminemia was found in all five Portuguese patients with AOA1 with a long disease duration, suggesting that AOA1 and EOCA-HA correspond to the same entity that accounts for a significant proportion of all recessive ataxias. The narrow localization of AOA1 should prompt the identification of the defective gene.
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PMID:Homozygosity mapping of Portuguese and Japanese forms of ataxia-oculomotor apraxia to 9p13, and evidence for genetic heterogeneity. 1117 Aug 99

Leukocyte adhesion deficiency type II is an autosomal recessive syndrome characterized by generalized reduction of L-fucose in glycoconjugates; the specific molecular defect is still undefined. The most important clinical symptoms include severe growth and mental retardation and severe immunodeficiency. Patients from two ethnic groups have been reported, i.e. Arab and Turkish. We have observed that GDP-L-fucose transport into Golgi vesicles was specifically impaired in an Arab patient, with a significant reduction of the V:(max) but no significant differences in the K:(m) from control and parents. GDP-L-fucose transport showed simple saturation kinetics in all samples. Transport of UDP-galactose, UDP-N:-acetylglucosamine, and CMP-sialic acid was comparable into vesicles from the Arab patient, parents, and control. These kinetic parameters probably account for the failure to obtain any clinical and biochemical response to fucose therapy in Arab patients. This contrasts both with the distinctive kinetic properties of GDP-L-fucose transport and with the success of fucose therapy, which have been recently reported in one patient of Turkish origin. Accordingly, the biochemical properties of GDP-L-fucose transport into the Golgi are consistent with different variants of leukocyte adhesion deficiency type II that are probably the result of different molecular defects.
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PMID:Impairment of the Golgi GDP-L-fucose transport and unresponsiveness to fucose replacement therapy in LAD II patients. 1126 38

We report on an 11-year-old Japanese girl with combined immunodeficiency and chromosomal instability. She had postnatal growth deficiency and microcephaly, preaxial polydactyly of the left hand, and susceptibility to infections. Immunological studies showed marked lymphocytopenia (around 500/ll), reduced lymphocyte response to various mitogens, and reduced or absent serum IgA, IgG, and IgM. Cell biological studies of her primary skin fibroblasts demonstrated spontaneous chromosome aberrations and radiation hypersensitivity. The combination of immunodeficiency, chromosomal instability, and radiation hypersensitivity as seen in the girl is present in both ataxia-telangiectasia and Nijmegen breakage syndrome. Ataxia-telangiectasia was excluded because of differences in clinical features and laboratory data. Likewise, Nijmegen breakage syndrome is unlikely to be the case because the characteristic face, hyperpigmented spots, and mental retardation present in the syndrome were missing in the girl. Sequence analysis of a Nijmegen breakage syndrome responsible gene, NBS1, revealed no mutations. A normal NBS1 product was also demonstrated by immunoblot analysis using an anti-NBS1 antibody. We propose that the disorder in the girl represents a new combination of combined immunodeficiency and chromosomal instability.
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PMID:Combined immunodeficiency, chromosomal instability, and postnatal growth deficiency in a Japanese girl. 1133 42

Down syndrome (DS) is a frequent chromosomal aberration. Triplication of the fragment 21q22 of chromosome 21 is sufficient to cause the DS phenotype including immunodeficiency, premature aging, mental retardation, and an increased risk of leukemia. Chromosomal aberrations caused by X-ray irradiation were observed in DS lymphocytes and DS fibroblasts, but the correlation between chromosomal sensitivity, repair deficiency, and radioresistant DNA synthesis was not clear. Here some insight into the nature of this problem has been made. Besides, new arguments have been provided in favour of genetic heterogeneity of this genetic disorder.
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PMID:[Down syndrome: pathogenesis, radioresistant DNA synthesis and chromosomal instability]. 1214 83

ICF syndrome is a rare autosomal recessive disorder characterized by immunodeficiency, centromeric instability, and facial anomalies. It is caused by mutations in a de novo DNA methyltransferase gene, DNMT3B. We here report the first three Japanese cases of ICF syndrome from two unrelated families. All patients had typical facial dysmorphism and immunoglobulin A (IgA) deficiency, but none of them had apparent mental retardation. Cytogenetic analysis of peripheral blood lymphocytes showed chromosomal abnormalities, including multiradial configurations and a stretching of the pericentromeric heterochromatin of chromosomes 1 and 16. Hypomethylation of classical satellite 2 DNA was also observed. Mutation analyses of DNMT3B revealed three novel mutations: patient 1 from the first family was a compound heterozygote for a nonsense mutation (Q42Term) and a missense mutation (R832Q); patients 2 and 3 from the second family were both homozygous for a missense mutation (S282P). The R832Q mutation occurred within the conserved methyltransferase domain, and thus may affect the enzyme activity directly. The S282P mutation, on the other hand, occurred close to the PWWP domain, which is presumably involved in protein-protein interaction. This is the first missense mutation mapped to the N-terminal half of the protein, suggesting that the region plays an important role in the regulation of the DNMT3B enzyme.
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PMID:Three novel DNMT3B mutations in Japanese patients with ICF syndrome. 1223 17

Nijmegen breakage syndrome (NBS) is characterized by growth retardation, microcephaly, mental retardation, immunodeficiency, and predisposition to malignancies, especially B-cell lymphomas. In contrast, leukemia is rare. A 23-year-old NBS patient presented with anemia, thrombocytopenia, and hyperlymphocytosis. The diagnosis of T-cell prolymphocytic leukemia (T-PLL) was confirmed by cytological and immunological assays (TdT(-), CD2(+), CD5(+), CD3m, and CD7(+)). Biological assays also showed a hemolytic anemia and a clotting factor V decrease. The patient was first treated by methylprednisone for 3 weeks. During this period the lymphocyte count decreased. The simultaneous normalization of the hemolysis and of factor V suggested that both could be related to T-PLL. Since T-PLL is refractory to conventional therapies with a poor prognosis, an intensive chemotherapy such as 2'-deoxycoformycin with anti-CDw52 monoclonal antibodies is usually favored. In the present case, however, because of the specific context (i.e., NBS-induced immunodepression, severe hemolytic anemia, and acquired factor V deficiency), he received pentostatin weekly during 1 month and in maintenance during 6 months. At last follow-up (7 months) he showed a persistent control of the lymphocytosis with no side effect.
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PMID:T-cell prolymphocytic leukemia with autoimmune manifestations in Nijmegen breakage syndrome. 1284 81

Kabuki syndrome is a multiple congenital anomaly/mental retardation syndrome which often involves recurrent infections. There is cumulative evidence of an immunodeficiency in Kabuki patients. We report a 2-year-old girl with typical Kabuki syndrome, who developed acute lymphocytic leukemia. The patient showed low levels of immunoglobulins G and A and a history of recurrent infections, that might indicate an immunodeficiency leading to an increased susceptibility to cancer. The girl was treated according to BFM protocols adapted to the patient's impaired cardiac situation and severe underweight. She achieved continual complete remission. Classical and molecular cytogenetic analyzes did not detect any abnormality.
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PMID:Patient with Kabuki syndrome and acute leukemia. 1294 77

We describe a 34-year-old male patient with Jacobsen syndrome associated with a broad spectrum of anomalies and an increased susceptibility to infections. Features commonly seen in Jacobsen syndrome were short stature, mental retardation, congenital heart disease, cryptorchidism, strabismus, distal hypospadia glandis, and mild thrombocytopenia. Chromosome analysis disclosed a mosaic 46,XY,del(11)(q24.1)/46,XY karyotype with a very low percentage of normal cells. In addition, transverse upper limb defect, imperforate anus, and hearing impairment were noted. Cellular anomalies include functional impairment and deficiency of T-helper cells, and a low serum immunoglobulin M (IgM)-level. The presence of a transverse limb defect and primary immunodeficiency has not been reported previously in Jacobsen syndrome.
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PMID:Primary immunodeficiency in combination with transverse upper limb defect and anal atresia in a 34-year-old patient with Jacobsen syndrome. 1505 45

Ataxia-telangiectasia (A-T) is a progressive neurodegenerative disorder, with onset in early childhood and a frequency of approximately 1 in 40,000 births in the United States. A-T is seen among all races and is most prominent among ethnic groups with a high frequency of consanguinity. The syndrome includes: progressive cerebellar ataxia, dysarthric speech, oculomotor apraxia, choreoathetosis and, later, oculocutaneous telangiectasia. Immunodeficiency with sinopulmonary infections, cancer susceptibility (usually lymphoid), and sensitivity to ionizing radiation are also characteristic. Laboratory findings include: (1) elevated alphafetoprotein (AFP), (2) cerebellar atrophy on magnetic resonance imaging, (3) reciprocal translocations between chromosomes 7 and 14 in lymphocytes, (4) absence or dysfunction of the ATM protein, (5) radiosensitivity, as demonstrated by colony survival assay (CSA), and (6) mutations in the ATM gene. The latter are usually truncating or splicing mutations; approximately 10% are missense mutations. Mutations are found across the entire gene. Almost all recurring mutations are found on unique haplotypes that represent founder effects and ancestral relationships between patients. In addition to radiosensitivity and sensitivity to radiomimetic chemicals, the phenotype of A-T cells includes defective damage-induced activation of the cell cycle checkpoints at G1, S and G2/M. With the aid of molecular testing, A-T can now be distinguished from other autosomal recessive cerebellar ataxias (ARCAs) such as Friedreich ataxia, Mre11 deficiency (AT-like disease), and the oculomotor apraxias 1 (aprataxin deficiency) and 2 (senataxin deficiency). Other "A-T variants" include: (1) Nijmegen breakage syndrome (NBS) or nibrin/Nbs1 deficiency, with microcephaly and mental retardation but without ataxia, apraxia, or telangiectasia, and 2) A-T(Fresno), a phenotype that combines features of both NBS and A-T, with mutations in the ATM gene. The term "A-T variant" has a diminishing usefulness.
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PMID:Ataxia-telangiectasia, an evolving phenotype. 1527 7

The Immunodeficiency, Centromeric instability, and Facial (ICF) syndrome is a rare autosomal recessive disorder that results from mutations in the DNMT3B gene, encoding a DNA-methyltransferase that acts on GC-rich satellite DNAs. This syndrome is characterized by immunodeficiency, facial dysmorphy, mental retardation of variable severity and chromosomal abnormalities that essentially involve juxtacentromeric heterochromatin of chromosomes 1 and 16. These abnormalities demonstrate that hypomethylation of satellite DNA can induce alterations in the structure of heterochromatin. In order to investigate the effect of DNA hypomethylation on heterochromatin organization, we analyzed the in vivo distribution of HP1 proteins, essential components of heterochromatin, in three ICF patients. We observed that, in a large proportion of ICF G2 nuclei, all HP1 isoforms show an aberrant signal concentrated into a prominent bright focus that co-localizes with the undercondensed 1qh or 16qh heterochromatin. We found that SP100, SUMO-1 and other proteins from the promyelocytic leukemia nuclear bodies (NBs) form a large body that co-localizes with the HP1 signal. This is the first description of altered nuclear distribution of HP1 proteins in the constitutional ICF syndrome. Our results show that satellite DNA hypomethylation does not prevent HP1 proteins from associating with heterochromatin. They suggest that, at G2 phase, HP1 proteins are involved in the heterochromatin condensation and may therefore remain concentrated at these sites until the condensation is complete. They also indicate that proteins from the NB could play a role in this process. Finally, satellite DNA length polymorphism could affect the efficiency of heterochromatin condensation and thus contribute to the variability of the ICF phenotype.
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PMID:Subcellular distribution of HP1 proteins is altered in ICF syndrome. 1547 Mar 59


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