Gene Function & Disease最新文献

We studied a girl with severe mental retardation, dysmorphic features (metopic ridging, mongoloid slant of palpebral fissures, short nose, thin vermilion, retrogenia, and deep-set ears) and multiple congenital abnormalities (microcephaly, agenesis of corpus callosum, flattened gyri, postaxial hexadactyly, and gastro-oesophageal reflux) for subtelomeric deletions using fluorescent in-situ-hybridization (FISH). Only one signal was found with the 1q probe and three signals with the 18q probe. Two of the 18q signals hybridized to the normal chromosome 18 and the third was found on 1q. Therefore, the patient has an unbalanced translocation t(1;18) resulting in monosomy 1q44 and trisomy 18q23-qter. The translocation was not detectable with classical cytogenetics. Comparison of the phenoytpe of patients with the 1q42→qter and 1q43→qter deletion syndrome, respectively, and our patient with a much smaller deletion revealed phenotypical and neurological similarities. This would suggest that the 1q- syndrome phenotype is due to deletions of genes present in the smaller deletion described here. Therefore, patients with a similar phenotype should be analyzed for submicroscopic deletions with the 1qtel probe.

The aim of this study was to identify the specific interactions between child characteristics, parental stress and coping, as well as intervening variables in families with a child with a fragile X syndrome (FXS). 49 boys with a FXS aged 5;7 to 16;10 years (x = 8.6) and a control group of 16 boys with tuberous sclerosis (TSC) aged 5;0 to 17;7 (x = 9.5) were recruited mainly through parental support groups. They were examined regarding: intelligence, comorbid psychopathology, social support of the family, parental stress, and coping. The mean IQ equivalents for the FXS (and the TSC patients) were between 46.1 and 48.8 (58.9 and 60.8) with a relatively homogeneous profile. The psychiatric comorbidity was higher for the FXS patients: 18.4% (25%) had no, 46.7% (25%) multiple diagnoses (DSM-IV), 89.8% (68.8%) had a CBCL (Child Behavior Checklist) total score in the clinical and borderline range. Families with an FXS child had a significantly higher total stress level and a lower degree of resources than the those with a TSC child (QRS; p < .01), especially regarding the ‘child characteristics’ (p < .001) and the ‘physical incapacitation’ (p < .01) scales. The higher stress in the FXS parents was significantly influenced by the higher rate of psychiatric diagnoses of the FXS children, but not by the general level of intelligence. Social support was high in both groups and inversely correlated with stress. Coping abilities did not differ between the two groups. The higher the stress was perceived in the FXS families, the less parents were able to cope actively and resorted to more passive forms of coping.In conclusion, parents of FXS boys have high level of social support and coping abilities. They experience significantly more stress, which is influenced by the child's behavioral problems. This stress negatively affects active parental coping.

Celiac disease (CD) susceptibility is strongly associated with the HLA alleles DQA1 0501 and DQB1 02*. To investigate this, we performed a study which included thirty celiac children and sixty-five first-degree relatives of them. DQB1 genotyping was performed by PCR (polymerase chain reaction) amplification. The allele frequencies in each group were compared by Chi-square test (χ²) using Yates correction and Fisher test. Most patients (70%) were positive for DQB1 0201. HLA-DQB1 0201 was found in 61% of the first-degree relatives. 58% of the patients showed heterozygosity for DQB1 0201, whereas 12% of the celiac patients were homozygous for DQB1 0201. These findings support the role of DQB1 0201 alleles as a risk factor for celiac disease. No significant differences could be detected in the HLA-DQB1 allele distribution between celiac patients and their first-degree relatives.

My laboratory has been interested in the consequences of the insertion of foreign DNA into established mammalian genomes and has studied this problem in adenovirus type 12 (Ad12)-transformed cells or in Ad12-induced hamster tumors. Ad12 is a potent oncogenic agent in newborn Syrian hamsters. Since integrated foreign genomes are frequently de novo methylated, it appears that they might be modified by an ancient defense mechanism against foreign DNA. In cells transgenic for the DNA of Ad12 or for the DNA of bacteriophage λ, changes in cellular methylation and transcription patterns have been observed. Thus, the insertion of foreign DNA can have important functional consequences which are not limited to the site of foreign DNA insertion. These findings appear to be relevant also for viral oncology, tumor biology and for the interpretation of data derived from transgenic organisms. For most animals, the main portal of entry for foreign DNA is the gastrointestinal tract. We have investigated the fate of orally ingested foreign DNA in mice. Naked DNA of bacteriophage M13 or the cloned gene for the green fluorescent protein (GFP) of Aequorea victoria have been used as test molecules. At least transiently, food-ingested DNA can be traced to different organs and, after transplacental transmission, to fetuses and newborns. There is no evidence for germ line transmission or for the expression of orally administered GFP DNA.

The state of methylation of the 5′-CpG-3′ sites is known to be linked to the regulation of promoter function by modulating DNA-protein interactions and to the structure of chromatin. As part of a project to determine methylation patterns in the human genome, the methylation profiles were examined in genes for the human erythroid membrane proteins; protein 4.2 (P4.2), gene (ELB42), band 3 (B3), gene (EPB3), and β-spectrin (β-Sp), gene (SPTB). The bisulfite protocol of the genomic sequencing method was applied.(1) In the DNA from peripheral white blood cells, the promoter regions of EPB3 and ELB42 were extensively methylated, but the promoter of SPTB was totally unmethylated. (2) During erythroid differentiation, (i) ELB42 was unmethylated in DNAs from the cell line UT-7/EPO, but became methylated (55−93 %) in cultured erythroblasts from peripheral BFU-E. The mRNA from ELB42 was first detected in early erythroblasts and protein 4.2 was expressed in late erythroblasts. (ii) EPB3 was consistently methylated in UT-7/EPO and also in cultured erythroblasts from burst forming unit erythroid (BFU-E) from peripheral blood. EPB3 and ELB42 were efficiently transcribed in UT-7 cells only after erythropoietin stimulation. (iii) SPTB remained unmethylated in DNAs from UT-7/EPO and cultured erythroblasts. (3) We also investigated methylation profiles in peripheral white blood cells from patients with erythroid diseases, like complete P4.2 deficiency due to ELB42 mutations, hereditary spherocytosis with EPB3 mutations, and hereditary elliptocytosis with SPTB mutations. The methylation profiles of the promoter regions of these three genes were essentially identical to those in healthy individuals.

Glutamine synthetase (GS) constitutes an endogenous mechanism for protection against glutamate neurotoxicity in neural tissues by catalyzing the amidation of the neurotoxic amino acid glutamate to the non-toxic amino acid glutamine. Expression of GS is regulated by systemic glucocorticoids, which induce transcription of the GS gene in glial cells only. This cell type specificity is established through the mutual activity of positive and negative regulatory elements, the glucocorticoid response element (GRE) and the neural restrictive silencing element (NRSE), respectively. Glial cell proliferation, which often occurs at the site of neural injury (gliosis), results in a marked decline in GS expression. This decline is mediated by the c-Jun protein, which accumulates in the proliferating cells and blocks the transcriptional activity of the glucocorticoid receptor. Disruption of glia-neuron cell contacts or supply of bFGF can also cause a decline in GS by a mechanism that involves the activation of the c-Jun signaling pathway in glial cells. Considering the detoxificating role of GS, stimulation of glial cell proliferation at the site of injury may exacerbate glutamate-mediated neurotoxicity through direct downregulation of GS.

Prion diseases are characterized by the propagation of an abnormally folded protein, denoted scrapie prion protein (PrP^Sc). Here we review results from our group which reveale different possibilities to interfere with the propagation and accumulation of PrP^Sc in scrapie-infected cell lines and animal models.

Red cell membrane proteins are composed of cytoskeletal proteins (spectrins, actin, and protein 4.1), integral proteins (band 3, and glycophorins), and anchoring proteins (ankyrin and protein 4.2). In disease states, abnormalities of α-spectrin, β-spectrin and protein 4.1 are now known as pathognomonic for hereditary elliptocytosis. The positions affected in these membrane protein genes were well correlated with the severity of the clinical findings and of the anomalies of their membrane ultrastructure and functions, as shown at best in three independent traits of β-spectrin anomalies; β-spectrin Lel'uy, β-spectrin Tokyo, and β-spectrin Nagoya. It should also be noted that the gene mutations of the C-terminal region of α-spectrin was strictly associated with hereditary elliptocytosis, contrary to the gene mutations all other regions, especially at the N-terminal region of α-spectrin which were associated with hereditary pherocytosis. In hereditary spherocytosis, which is most common in red cell membrane disorders, the gene mutations of ankyrin, band 3, and protein 4.2 were predominant. This disorder was found nearly exclusively in heterozygous states, rarely in homozygous states. It is also important to note that the incidence of the gene mutations pathognomonic for this disorder demonstrated great differences among various ethnic groups. The phenotypic characteristics of red cell membrane structure examined by electron microscopy demonstrated that total deficiency of band 3 proteins due to a homozygous nonsense mutation of the band 3 gene showed extremely unstable membrane ultrastructure, contrary to the total deficiency of protein 4.2 due to homozygous missense mutations with a moderate instability of the cytoskeletal network and the integral protein. Even in total deficiencies of protein 4.2, the phenotypic expressions were variable. Genotypic and phenotypic expressions in red cell membrane disorders are reviewed as based on the results from our laboratory for the recent 25 years.

DNA methylation in mammals is known to play a role in gene silencing and to be critical in embryo development. Here we describe how methylation makes use of histone deacetylase repressory complexes in stable gene silencing and perhaps also in stable inheritance of chromatin structure. If DNA methylation is an evolutionary more recent addition to the mechanisms regulating the mammalian genome, it certainly takes advantage of existing histone deacetylase repressory complexes that are observed in methylation deficient organisms, such as Drosophila, yeast, and C. elegans.

From the nuclei of human HeLa cells, we have isolated a 20 kDa protein which binds specifically to 5′-d(CGG)_n-3′ repeats, either in synthetic oligodeoxyribonucleotides or in the 5′-untranslated region of the FMR1 (fragile X mental retardation 1) gene on human chromosome Xq27.3. The loss of the FMR1 gene product has been implicated in the causation of the fragile X syndrome in humans. In electrophoretic mobility shift assays, the sequence specificity and methylation sensitivity of the 5′-d(CGG)_n-3′-binding protein (CGGBP1) were documented. When the CGGBP1 was overexpressed in HeLa cells, the FMR1-promoter in constructs carrying this promoter and the endogenous FMR1 promoter were inhibited. The inhibition depended on the length of a 5′-d(CGG)_n-3′ repeat in the FMR1-promoter constructs. A fusion protein consisting of the green fluorescent protein (GFP) and the CGGBP1 associated preferentially with the telomers of the short arms of the acrocentric human chromosomes 13, 14, 15, 21 and 22. Their telomers carry the genes for the 28S rRNA which contain 5′-d(CGG)_n-3′ repeats. We currently search for additional targets for CGGBP1 binding in the human genome by using the DNA microarray technique. The amino acid sequence of three peptides in the CGGBP1 gene was determined and an available EST clone was used for cloning the human and murine CGGBP1 genes. Protein database searches did not reveal any related sequences. The nucleotide sequence of the translated region of the CGGBP1 gene from healthy, premutation and full mutation carrying fragile X individuals was determined, but mutations were not detected.