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At least 1,225 records · Page 68Linked to original sources
PubMed2003

MLYCD mutation analysis: evidence for protein mistargeting as a cause of MLYCD deficiency.

Malonyl-CoA decarboxylase (MLYCD) deficiency is an autosomal recessive disorder characterized by malonic aciduria, developmental delay, seizure disorder, hypoglycemia, and cardiomyopathy. Genomic sequencing of MLYCD in nine unrelated patients identified 16 of 18 pathogenic alleles, which are documented in the newly created Human MLYCD Allelic Variant Database (http://mlycd.hgu.mrc.ac.uk/). Fibroblast cell lines were available from eight of these patients and two previously reported patients with homozygous MLYCD mutations. Western blot analysis using antisera raised to a C-terminal peptide detected a 66-kDa band that was absent in six patients and substantially reduced in three patients. One patient showed an increase in protein levels with a prominent smeary 68-l83-kDa band. Immunocytochemical analysis of MLYCD-expressing patient cell lines showed apparent intracellular mislocalization. An extreme N-terminal mutation c.8G>A (p.G3D) mislocalized to the plasma membrane, suggesting that a novel targeting signal may reside in a four-amino acid conserved N-terminal motif. A 25-base deletion between the putative mitochondrial and peroxisomal initiating codons (M1 and M40) and a point mutation ablating the second of these (c.119T>C, p.M40T) both showed punctate perinuclear staining. As none of the three mislocalizing mutations are predicted to alter the catalytic function of the peptide, it seems likely that correct subcellular localization of MLYCD is critical for it to function normally.

Adolescent↗
PubMed2002

Infrequent p53 gene mutations and lack of p53 protein expression in clear cell sarcoma of the kidney: immunohistochemical study and mutation analysis of p53 in renal tumors of unfavorable prognosis.

A high prevalence of p53 gene mutation and protein expression has been found in the anaplastic variant of Wilms' tumor (WT), known to be associated with poor outcome. However, there are very few studies of p53 alterations in the other two rare and highly malignant renal tumors in childhood, in other words, clear cell sarcoma of the kidney (CCSK) and malignant rhabdoid tumor of the kidney (MRTK). Overexpression of p53 protein has been detected in eight CCSKs in one study, and in two in another, yet no molecular correlation with p53 gene mutations has been carried out. Our study is the first molecular analysis concerning p53 in CCSK. We investigated eight cases of CCSK and one case of MRTK for p53 protein expression by immunohistochemical staining. All were analyzed for p53 mutations in the region of exons 4 to 8 by polymerase chain reaction-single-strand conformational polymorphism (PCR-SSCP) method and DNA sequencing analysis. By histological study, no CCSK showed anaplastic features. None expressed p53 protein, but two harbored p53 mutations. One was in exon 5, with a base pair insertion between codons 162 to 163 causing frameshift alteration in amino acid. Another was a silent CTC-->CTT transversion in codon 289 of exon 8. The case of MRTK did not show any alterations of p53 protein or gene. Our result indicates that p53 alterations are infrequent in CCSK and do not seem to be primary genetic events in the pathogenesis of CCSK.

Adolescent↗
PubMed2006

Mutational analysis of the KIT gene in myelodysplastic syndrome (MDS) and MDS-derived leukemia.

The progenitor cells of myelodysplastic syndrome (MDS) are thought to undergo a multistep process during their transformation into overt acute leukemia. In this study, the role of mutation of the KIT gene in the extracellular membrane, juxtamembrane and tyrosine kinase domains was investigated in 75 patients with MDS or MDS-derived leukemia (MDS-AML). Mutation was detected in 2 of 15 (13.3%) patients with refractory anemia with excess blasts transformation (RAEB-T), in 1 of 15 (6.6%) patients with chronic myelomonocytic leukemia (CMML), and in 5 of 26 (19.2%) patients with MDS-AML. However, no mutation was found in any of the nine patients with refractory anemia (RA) or the 10 patients with refractory anemia with excess blasts (RAEB). Of the mutations, five patients had changes at the same codon in tyrosine kinase domain, Asp816, while the remainder had unique mutations. These observations suggest that KIT gene mutations identified in the advanced stage of MDS, and genetic abnormality in the KIT gene, particularly at codon 816, might be additional events that contribute to the progression of MDS to AML.

Adult↗
PubMed1996

Mutational analysis of the nucleotide binding domain of the mismatch repair enzyme hMSH-2.

The genes involved in postreplicative DNA mismatch repair are a highly conserved family of proteins. In humans, germline mutations in these genes (hMSH-2, hMLH-1, hPMS-1, and hPMS-2) have been implicated in hereditary nonpolyposis colorectal cancer (HNPCC). We have previously shown that a region of high homology between the members of this class of proteins in different species contains a type A nucleotide binding site consensus sequence which has ATPase activity and is sufficient to bind DNA containing specific mismatched residues (1). To identify residues which are necessary for this activity, we have created a range of mutants containing amino acid substitutions within the nucleotide binding domain of hMSH-2. These mutants have been expressed and assessed for ATPase activity and their ability to identify mismatch-containing DNA. Here we demonstrate that a variant protein which has the conserved residue Lys 675 within the nucleotide binding consensus sequence altered to an alanine has severely impaired ATPase activity and is unable to bind DNA containing specific mismatched residues.

Adenosine Triphosphatases↗
PubMed2001

Mutation analysis of the NMDAR2B (GRIN2B) gene in schizophrenia.

NMDA receptor dysfunction may be involved in the pathophysiology of schizophrenia. Based on this hypothesis, we screened 48 Japanese patients with schizophrenia for mutations in the coding region of the NMDAR2B subunit gene (GRIN2B). An association study between the identified DNA sequence variants and schizophrenia was performed in 268 Japanese patients with schizophrenia and 337 Japanese control subjects. Eight single nucleotide polymorphisms were detected, all of which were synonymous. The association sample showed statistically significant excesses of homozygosity for the polymorphisms in the 3' region of the last exon in the patients with schizophrenia (P = 0.004) and higher frequency of the G allele of the 366C/G polymorphism (corrected P = 0.04) in the patients than in the controls. Although we did not detect NMDAR2B protein variants, our findings support the possibility that the GRIN2B gene or a locus in linkage disequilibrium with it may confer susceptibility to schizophrenia. Replication studies in independent samples are warranted.

Adult↗
PubMed2006

Mutational analysis of Norrin-Frizzled4 recognition.

Norrin and Frizzled4 (Fz4) function as a ligand-receptor pair to control vascular development in the retina and inner ear. In mice and humans, mutations in either of the corresponding genes lead to defects in vascular development. The present work is aimed at defining the sequence determinants of binding specificity between Norrin and the Fz4 amino-terminal ligand-binding domain (the "cysteine-rich domain" (CRD)). The principal conclusions are as follows: 1) Norrin binds to the Fz4 CRD and does not detectably bind to the 14 other mammalian Frizzled and secreted Frizzled-related protein CRDs; 2) Norrin and Xenopus Wnt8 recognize largely overlapping regions of the Fz4 CRD; 3) surface determinants on the Fz4 and Fz8 CRDs that allow Norrin to distinguish between these two CRDs reside within several small regions on one face of the CRD; 4) Norrin function depends critically on three pairs of cysteines that form the highly conserved trio of disulfide bonds shared among all cystine knot proteins, but the remaining two putative disulfide bonds are less important; 5) Norrin-CRD binding depends on a largely contiguous group of amino acids in the extended beta-sheet domain of Norrin that are predicted to face away from the interface between the two monomers in the Norrin homodimer; 6) Norrin-CRD binding is strongly modulated by interactions involving charged amino acid side chains; and 7) Norrin-CRD binding is enhanced approximately 10-fold by the addition of heparin. These observations are discussed in the context of Frizzled signaling and the structure and function of other cystine knot proteins.

Amino Acid Sequence↗
PubMed1998

Prenatal diagnosis of Machado-Joseph disease by direct mutation analysis.

MJD is the most frequent dominant ataxia and an incapacitating disorder. Onset is most frequently during the reproductive years, and genetic counseling is its only means of prevention. The causative mutation--an expansion of a (CAG)n on chromosome 14q32.1--can now be directly detected. We now report the first two cases of prenatal diagnosis (PND). The first presented as a simultaneous request for predictive testing and PND at 14 weeks of pregnancy. Owing to time constraints, we performed a full protocol of counseling with shorter inter between sessions, while psycho-social evaluation of the other parent obstetric consults were also begun. We ensured that the couple wished termination if the fetus was a carrier, to avoid a presymptomatic test for the unborn child. We were thus able to deliver test results two weeks before PND. As the fetus carried an expanded allele (77 CAGs) inherited from his father, termination was performed and the couple received counselling, psychological and social support. The second case was the fetus of a carrier-mother that was diagnosed as non-carrier, also after amniocentesis.

Adult↗
PubMed1995

Mutation analysis of the ROM1 gene in retinitis pigmentosa.

To examine the role of ROM1, a homologue of peripherin/RDS, in autosomal dominant retinitis pigmentosa (adRP), we screened 224 adRP and 29 simplex RP probands for ROM1 mutations. Four ROM1 alleles were designated as potentially pathogenic because they were found only in RP patients but not in 50-100 controls nor in 249 other RP probands. The substitutions P60T and T108M were present in a single allele in a subject with typical adRP, and this allele cosegregated with the disease in the small family. The putative null allele L114 [1 bp] was present in an individual with atypical RP but not in three unaffected siblings. This insertion has been previously reported to cause RP only when accompanied by a peripherin/RDS mutation, but no peripherin/RDS mutations were found in any of the four probands reported here. Two substitutions (G75D, R242Q) were present in two other probands with simplex RP. These data suggest that potentially pathogenic ROM1 mutations occur in 1% or less of patients with adRP or simplex RP. The absence of detectable peripherin/RDS mutations in these families suggests either that: (i) mutations in other digenic partners are required for pathogenic ROM1 alleles to cause retinal degeneration; (ii) these ROM1 mutations do not cause RP; or (iii) peripherin/RDS mutations are present but were not identified in these patients.

Adult↗
PubMed1995

Mutational analysis of the estrogen-receptor gene in endometrial carcinoma.

OBJECTIVE: To determine whether mutation in the DNA of the estrogen-receptor gene occurs in endometrial cancer. METHODS: Polymerase chain reaction amplification and single-stranded conformation polymorphism analysis of the entire coding region (exons 1-8) of the human estrogen-receptor gene, as well as an untranslated region (exon I*) in the gene, were performed on genomic DNA extracted from 56 snap-frozen endometrial cancers. All cancers demonstrating mobility shifts on single-stranded conformation polymorphism suggestive of DNA sequence alteration were subjected to definitive DNA sequencing of the relevant portion of the estrogen-receptor gene. RESULTS: In addition to detecting a frequent, previously described polymorphism in exon 1, single-stranded conformation polymorphism analysis of the 56 endometrial cancers identified seven cancers with mobility shifts. Three cancers shifted in exon 3, one cancer each shifted in exons 4 and 7, and two shifted in exon 8. Deoxyribonucleic acid sequencing revealed sequence alterations in all seven cases demonstrating mobility shifts. In six of these seven cases, these alterations were consistent with infrequent silent polymorphisms; in the seventh cancer, the sequence alteration proved to be a somatic missense mutation at codon 537 in the region of the estrogen-receptor gene encoding the hormone-binding domain of the receptor protein. CONCLUSION: The infrequent DNA mutation in the estrogen-receptor gene is unlikely to account for the variation in estrogen-receptor expression observed in endometrial cancer.

Adult↗
PubMed1997

Mutation analysis and loss of heterozygosity of PEDF in central nervous system primitive neuroectodermal tumors.

Deletion of 17p is the most frequent abnormality observed in central nervous system (CNS) primitive neuroectodermal tumors (PNETs), implicating the presence of a tumor suppressor gene which maps to 17p. The gene for pigment epithelium-derived factor (PEDF) has been cloned and mapped to 17p13. PEDF belongs to the serine protease inhibitor (SERPIN) gene family. The PEDF protein has neurotrophic and neuronal-survival activities and is expressed in the CNS. Twenty tumor and matched normal DNA samples from patients with PNETs were screened by single-strand conformation polymorphism (SSCP) analysis to determine loss of heterozygosity (LOH) and to identify potential mutations within the 8 exons of the PEDF gene. Ten of the 20 tumors demonstrated LOH, consistent with the deletion status of 17p determined by cytogenetic or fluorescence in situ hybridization studies. SSCP analysis of the genomic DNA from the 10 cases with LOH demonstrated several polymorphisms in exons 4 and 7, but no mutations. Our results are consistent with a loss of alleles on 17p in 50% of CNS PNETs, but do not suggest that PEDF is a candidate for the PNET suppressor gene in 17p13.

Adolescent↗
PubMed2001

Fine mapping of the PTGFR gene to 1p31 region and mutation analysis in human breast cancer.

The 1p31 chromosomal region shows loss of heterozygosity (LOH) in up to 50% of human breast cancer, indicating the presence of a tumor suppressor gene at this location. Many efforts have been made to identify candidate genes responsible for breast cancer on the short arm of chromosome 1. It was shown that prostaglandins have been implicated in the tumorigenesis pathway, perhaps via interactions with their cell surface receptors. The prostaglandin F2 receptor gene (PTGFR) was tentatively mapped to 1p31 adjacent to the region undergoing LOH in human breast cancer. We undertook a mutation study in 34 sporadic human breast tumors using a variant of SSCP, incorporation PCR SSCP (IPS). Several nucleotide variants were detected in different tumors. Here we report the nature of these nucleotide changes and the possible involvement of the PTGFR gene in the etiology of human cancer.

Base Sequence↗
PubMed1995

Mutational analysis of familial and sporadic hyperekplexia.

Hyperekplexia is a rare, autosomal dominant neurological disorder characterized by hypertonia, especially in infancy, and by an exaggerated startle response. This disorder is caused by mutations in the alpha 1 subunit of the inhibitory glycine receptor (GLRA1). We previously reported two GLRA1 point mutations detected in 4 unrelated hyperekplexia families; both mutations were at nucleotide 1192 and resulted in the replacement of Arg271 by a glutamine (R271Q) in one case and a leucine (R271L) in the other. Here, 5 additional hyperekplexia families are shown to have the most common G-to-A transition mutation at nucleotide 1192. Haplotype analysis using polymorphisms within and close to the GLRA1 locus suggests that this mutation has arisen at least twice (and possibly four times). In 2 additional families, a third mutation is also presented that changes a tyrosine at amino acid 279 to a cysteine (Y279C). Five patients with atypical clinical features and equivocal or absent family history of hyperekplexia and 1 patient with a classical presentation but not family history are presented in whom a mutation in the GLRA1 gene was not detected. Thus, only clinically typical hyperekplexia appears to be consistently associated with GLRA1 mutations, and these affect a specific extracellular domain of the protein.

Base Sequence↗