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PubMed2004

Oculocutaneous albinism type 4 is one of the most common types of albinism in Japan.

Oculocutaneous albinism (OCA) is a complex genetic disease with great clinical heterogeneity. Four different types of OCA have been reported to date (OCA1, OCA2, OCA3, and OCA4). MATP was recently reported in a single Turkish OCA patient as the fourth pathological gene, but no other patients with OCA4 have been reported. Here, we report the mutational profile of OCA4, determined by genetic analysis of the MATP gene in a large Japanese population with OCA. Of 75 unrelated patients that were screened, 18 individuals (24%) were identified as having OCA4; they harbored seven novel mutations, including four missense mutations (P58S, D157N, G188V, and V507L) and three frameshift mutations (S90CGGCCA-->GC, V144insAAGT, and V469delG), showing that MATP is the most frequent locus for tyrosinase-positive OCA in Japanese patients. We discuss the functional melanogenic activity of each mutant allele, judging from the relationship between the phenotypes and genotypes of the patients. This is the first report on a large group of patients with OCA4.

Adolescent↗
PubMed1995

Mutation analysis of the TSC2 gene in an African-American family.

Tuberous sclerosis complex is an autosomal dominant disorder with loci on chromosome 9q34 (TSC1) and chromosome 16p13.3 (TSC2). The TSC2 gene has been isolated. To date, only a small number of intragenic deletional and point mutations have been detected, almost exclusively in sporadic (no family history) cases. With the exception of a single parent/offspring pair, there have been no published reports of mutations in extended multigenerational chromosome 16-linked TSC2 families. For our TSC studies we ascertained and sampled a four-generation African-American TSC family that shows a high likelihood for linkage to chromosome 16 (z=1.53). Using single-strand conformation polymorphism analysis we identified a 4590/4591delC mutation in exon 34. The 4590/4591delC causes a frameshift mutation resulting in the creation of a premature stop codon. In addition, we have detected a 542del4 polymorphism in the two partially overlapping polyadenylation signals in exon 40 that segregates in the family. The polymorphism has been detected in six of 72 African-American control chromosomes examined, and has not been detected in 80 Caucasian control chromosomes examined.

Amino Acid Sequence↗
PubMed1999

Global sequence diversity of BRCA2: analysis of 71 breast cancer families and 95 control individuals of worldwide populations.

The aim of this study was to evaluate the prevalence of simple sequence variation in the BRCA2 gene. To this end, 71 breast and breast-ovarian cancer (HBC/HBOC) families along with 95 control individuals from a wide range of ethnicities were analyzed by means of denaturing high-performance liquid chromatography (DHPLC) and direct sequence analysis. In the coding (10 257 bp) and non-coding (2799 bp) sequences of BRCA2, 82 sequence variants were identified. Three different, apparently disease-associated BRCA2 mutations were found in six HBC/HBOC families (8%): two splice site mutations in introns 5 and 21, and one frameshift mutation in exon 11. In the coding region, 53 simple sequence variants were found: 35 missense mutations, one 2 bp deletion (CT) resulting in a stop at codon 3364, one nonsense mutation with a stop at codon 3326, one deletion of a complete codon (AAA) resulting in the loss of leucine, and 15 silent mutations. In the non-coding region, 26 polymorphisms were detected. Of the 79 sequence variants that were not obviously disease-associated, eight were detected only in HBC/HBOC families. The remaining 71 variants were identified in both HBC/HBOC families and control individuals. Sixty three sequence variants (80%) were specific for a continent. Forty two percent (33 out of 79) of the sequence variants were detected exclusively in Africa, though only 13% of the 332 chromosomes screened were of African origin. Our data indicate that, in BRCA2, simple sequence variation is frequent [in the coding region 1 in 194 bp (straight theta = 2.2 x 10(-4)), and in the non-coding region 1 in 108 bp (straight theta = 4.4 x 10(-4)), respectively].

Africa↗
PubMed2003

Mutations in a novel gene Dymeclin (FLJ20071) are responsible for Dyggve-Melchior-Clausen syndrome.

Dyggve-Melchior-Clausen syndrome (DMC) is a rare autosomal-recessive disorder, the gene for which maps to chromosome 18q21.1. DMC is characterized by the association of a spondylo-epi-metaphyseal dysplasia and mental retardation. Electron microscopic study of cutaneous cells of an affected child showed dilated rough endoplasmic reticulum, enlarged and aberrant vacuoles and numerous vesicles. As the etiology of the disorder is unknown, we have used a positional cloning strategy to identify the DMC gene. We detected seven deleterious mutations within a gene predicted from a human transcript (FLJ20071) in 10 DMC families. The mutations were nonsense mutations (R194X, R204X, L219X, Q483X), splice site or frameshift mutations (K626N+92aa to stop). The DMC gene transcript is widely distributed but appears abundant in chondrocytes and fetal brain. The predicted protein product of the DMC gene yields little insight into its likely function, showing no significant homology to any known protein family. However, the carboxy terminal end comprises a cluster of dileucine motifs, highly conserved across species. We conclude that DMC syndrome is consequent upon loss of function of a gene that we propose to name Dymeclin, which may have a role in process of intracellular digestion of proteins.

Abnormalities, Multiple↗
PubMed2004

Identification of the cylindromatosis tumor-suppressor gene responsible for multiple familial trichoepithelioma.

Multiple familial trichoepithelioma (MFT) is an autosomal dominant skin disease characterized by the presence of many small benign tumors with pilar differentiation predominantly on the face. The first locus has been previously mapped to chromosome 9p21, but no gene for MFT has been identified to date. To identify the disease gene in a large Chinese family, we initially performed linkage analysis with microsatellite markers from 9p21, but failed to confirm the linkage to this region. Previous publications showed MFT and familial cylindromatosis (FC) can occur within one family and in a single person. Therefore, we speculated that the cylindromatosis gene (CYLDI gene) responsible for FC may be related to the pathogenesis of MFT. In view of that, we genotyped all available individuals using 11 microsatellite markers spanning the CYLDI gene region at 16q12-q13. We identified the linkage of MFT to this region. Mutation analysis in the CYLDI gene detected a frameshift mutation, designated as c.2355-2358delCAGA. The study firstly identified the cylindromatosis gene responsible for MFT and showed that different mutations of the CYLDI gene can give rise to distinct clinical and histological expression such as FC and MFT.

Adolescent↗
PubMed2003

Melanocortin receptor variants with phenotypic effects in horse, pig, and chicken.

The melanocortin system is of considerable interest in domestic animals because their energy metabolism and pigmentation have been under strong selection. This article reviews our work on MC1R variants in horse, pig, and chicken, as well as a study on MC4R polymorphism in the pig. The chestnut coat color in horses is caused by an MC1R missense mutation (S83F). In the pig, we have described seven MC1R alleles controlling four different coat color phenotypes (wild type, dominant black, black spotting, and recessive red). The most interesting allele is the one causing black spotting because it carries two causative mutations, a frameshift and a missense mutation. The frameshift mutation is somatically unstable, and the black spots reflect somatic reversion events restoring the reading frame. Classic genetics have established eight alleles at the Extended black locus in chicken, which is assumed to correspond to the Extension locus in mammals. We have analyzed the co-segregation of alleles at MC1R and Extended black using a red jungle fowl x White Leghorn intercross and provide compelling evidence that these loci are identical. A previous study indicated that a missense mutation (D298N) in pig MC4R has an effect on fatness, growth, and feed intake. We could not confirm this association using an intercross between the wild boar and Large White domestic pigs, but it is possible that our F(2) generation was too small to detect the rather modest effect reported for this polymorphism.

Alleles↗
PubMed1990

Mutational analysis of a native substrate of the human immunodeficiency virus type 1 proteinase.

Proteolytic processing of the gag/pol precursor by the human immunodeficiency virus type 1 proteinase is essential for the production of infectious viral particles. Although the sites of virus-specific cleavages have been determined, the primary amino acid sequences surrounding these sites are heterogeneous and the determinants that direct the cleavage specificity exhibited by human immunodeficiency virus type 1 proteinase remain largely undefined. We performed mutational analysis of the Tyr/Pro site, which produces the amino terminus of the viral capsid protein, and the Phe/Pro site, which produces the amino terminus of the proteinase. Mutations were made in a clone encoding a frameshift mutation that results in the expression of equimolar amounts of the substrate and proteinase in the form of a truncated gag/pol precursor. After single-amino-acid substitutions were made, their effects on proteolytic processing were examined by in vitro transcription and in vitro translation of the synthetic mRNA; translation products were then processed by exogenously added purified proteinase. Single-amino-acid substitutions yielded both substrates which were processed with wild-type efficiency and substrates on which processing was impaired. At the Tyr/Pro site in gag, processing was severely inhibited by substitutions within the P4, P2, P1, and P2' positions. The Phe/Pro site in pol, however, demonstrated far greater tolerance to amino acid substitution. These data suggest that the primary amino acid sequence around a scissile bond is more critical for cleavage of the Tyr/Pro site than the Phe/Pro site.

Amino Acid Sequence↗
PubMed2003

Variable expression of cerebral cavernous malformations in carriers of a premature termination codon in exon 17 of the Krit1 gene.

BACKGROUND: Cerebral cavernous malformations (CCM) present as either sporadic or autosomal dominant conditions with incomplete penetrance of symptoms. Differences in genetic and environmental factors might be minimized among first-degree relatives. We therefore studied clinical expression in a family with several affected members. METHODS: We studied a three-generation family with the onset of CCM as a cerebral haemorrhage in the younger (four-year-old) sibling. Identification and enumeration of CCMs were performed in T2-weighted or gradient-echo MRIs of the whole brains. Genetic analysis comprised SCCP, sequencing and restriction polymorphism of the Krit1 gene in the proband and at risk relatives. RESULTS: The phenotypes of cerebral cavernous malformations (CCMs) in carriers of Krit1 mutations were very variable. We identified a novel frameshift mutation caused by a 1902A insertion in exon 17 of the Krit1 gene, which leads to a premature TAA triplet and predicts the truncating phenotype Y634X. A very striking finding was the absence of both clinical symptoms and CCMs in the eldest sibling harbouring the 1902insA. CONCLUSIONS: Patients in this family, harbouring the same mutation, illustrate the very variable clinical and radiological expression of a Krit1 mutation. The early and critical onset in the proband contrasts with minor clinical findings in affected relatives. This consideration is important in genetic counselling.

Cerebral Hemorrhage↗
PubMed1997

Mutations in the hepatocyte nuclear factor-1alpha/MODY3 gene in Japanese subjects with early- and late-onset NIDDM.

Recent studies have shown that mutations in the hepatocyte nuclear factor (HNF)-1alpha gene are the cause of maturity-onset diabetes of the young type 3 (MODY3). We have screened 193 unrelated Japanese subjects with NIDDM for mutations in this gene: 83 with early-onset NIDDM (diagnosis at <30 years of age) and 110 with late-onset NIDDM (diagnosis > or = 30 years of age). All of the members of the latter group also had at least one sibling with NIDDM. The 10 exons, flanking introns, and promoter region were amplified using polymerase chain reaction and were sequenced directly. Mutations were found in 7 of the 83 (8%) unrelated subjects with early-onset NIDDM. The mutations were each different and included four missense mutations (L12H, R131Q, K205Q, and R263C) and three frameshift mutations (P379fsdelCT, T392fsdelA, and L584S585fsinsTC). One of the 110 subjects with late-onset NIDDM was heterozygous for the missense mutation G191D. This subject, who was diagnosed with NIDDM at 64 years of age, also had a brother with NIDDM (age at diagnosis, 54 years) who carried the same mutation, suggesting that this mutation contributed to the development of NIDDM in these two siblings. None of these mutations were present in 50 unrelated subjects with normal glucose tolerance (100 normal chromosomes). Mutations in the HNF-1alpha gene occur in Japanese subjects with NIDDM and appear to be an important cause of early-onset NIDDM in this population. In addition, they are present in about 1% of subjects with late-onset NIDDM.

Age Factors↗
PubMed1999

Germline mutations in NF1 patients with malignancies.

We have analyzed 98.5% of the coding region of the NF1 gene at the cDNA level in seven NF1 patients who developed malignant peripheral nerve sheath tumors. Seven germline mutations were detected in six individuals: a 6-bp in-frame deletion in exon 28, a splice acceptor mutation in intron 31 resulting in a premature stop of translation, a missense mutation in exon 38, and three total NF1 gene deletions. In one of the patients with a total NF1 gene deletion, a missense mutation in exon 16 on the other NF1 allele was detected. These data indicate that NF1 patients developing malignant neoplasms can have any type of NF1 germline mutation such as a total gene deletion, a frameshift mutation, an in-frame deletion, or a missense mutation. We conclude that in our series no specific type of NF1 germline mutation was found in NF1 individuals with malignancies, but that large NF1 gene deletions were more frequently found in this group than reported for the general population of NF1 individuals. Genes Chromosomes Cancer 26:376-380, 1999.

Adolescent↗
PubMed2001

[Phenotyping and genotyping studies in a family with the compound heterozygosity for a deletional delta beta-thalassemia and a beta-thalassemia].

OBJECTIVE: To investigate the relationship between genotype and phenotype of a deletional delta beta-thalassemia and explore an approach to rapid prenatal diagnosis for compound heterozygotes of this defect and a beta-thalassemia. METHODS: A total of ten members in a Chinese family who had a 5-year-old propositus with thalassemia major and requested prenatal diagnosis for the second pregnancy were investigated. For genotyping analysis, the deletional delta beta-thalassemia was characterized by gap-PCR method and beta-thalassemia mutations were defined by reverse dot blot(RDB). For phenotyping analysis, hematological data including the RBC indices, quantification of HbF and HbA2 by Hb electrophoresis and the ratio of globin chain Ggamma/(Ggamma+Agamma) analyzed by capillary electrophoresis (CE) were obtained. RESULTS: The propositus inherited her mother's delta beta-thalassemia gene mutation and her father's CD41-42(-CTTT) frameshift mutation. Of nine members in this family screened for this type of deletion, four were positive and the phenotype could be explained satisfactorily by genotype. The results of prenatal diagnosis showed that the fetus was normal and had no beta-globin gene defects in both chromosomes. CONCLUSION: This is the first time to have performed prenatal diagnosis in Chinese family at-risk of compound heterozygotes for beta-thalassemia and delta beta-thalassemia in mailand China. The strategy to analyze the disease presented here may be a valuable reference to the similar problem.

Adolescent↗
PubMed1977

[Mutagenicity of the metabolites of the epoxide-diol pathway of safrole and its analogs. Study on Salmonella typhimurium].

Mutagenicity of the metabolites of the expoxide-diol pathway of safrole and analogues was studied on Ames' strains with Ames' method. Safrole, eugenol, eugenolmethylether, estragol, allylbenzene and 1'-hydroxysafrole, are not mutagen on TA 1535, TA 100 (point mutation) and TA 1537, TA 1538, TA 98 (frameshift mutations) without activation system. The corresponding epoxides that we have synthetized, are mutagens and inducers of point mutation in TA 1535 and TA 100. Dose-effect curves show differences between the mutagen efficiencies of these epoxides probably in relation with their electrophilic properties. On the other hand the 2', 3'-dihydro-2',3'-dihydroxisafrole was not mutagen in Ames' test. These results confirm the promutagen character of safrole and analogues and the role of the epoxides as proximate carcinogens.

Carcinogens↗
PubMed2004

[Double heterozygous mutations of non-canonical splice (IVS1a + 5g > a) and His348Gln caused inherited coagulation factor VII deficiency].

OBJECTIVE: To investigate the pathogenesis of inherited coagulation factor VII (FVII) deficiency. METHODS: The diagnosis was validated by coagulant parameter assay. FVII gene mutations were analysed in the proband by DNA direct sequencing of PCR products of all exons, exon-intron boundaries and the 3', 5'untranslated sequences. The mutations were confirmed by reverse sequencing. The ectopic transcripts of RT-PCR were used to confirm the characteristics of the mutation in non-canonical splice site (IVS1a + 5g > a). RESULTS: Double heterozygous mutations in the propositus were identified: a T to G mutation at position 10961, resulting in His348Gln substitution, a non-canonical splice site (IVS1a + 5g > a) mutation, causing the new model of splice and frameshift mutation. CONCLUSION: Double heterozygous mutations of His348Gln and IVS1a + 5g > a were identified in a propositus, the splicing pattern of the IVS1a + 5g > a mutation was reported for the first time.

Amino Acid Sequence↗
PubMed2004

[Experimental study on p53 gene mutation in keloid fibroblasts].

OBJECTIVE: To explore the significance and the role of the p53 gene mutation in the exon 4 to 8 in keloid fibroblasts. METHODS: Tissue samples from twelve patients with keloid and twelve hyperplastic scar respectively were harvested for in vitro culture of fibroblasts, and normal skin samples from the same patients were employed as the control. Polymerase chain reaction-based single-strained conformational polymorphism (PCR-SSCP) and DNA sequencing were employed to detect p53 gene mutations of the fibroblasts. RESULTS: The points and frameshift mutations in the exon 4, 5, 6, 7 of p53 gene were identified in 9 of the 12 keloid tissue samples. No p53 gene mutation was detected in all hyperplastic scar and normal skin samples. CONCLUSION: p53 gene mutation might play an important role in the formation and development of keloids.

Female↗
PubMed1993

p53 and Ki-ras gene mutations in epithelial ovarian neoplasms.

In an effort to define the pathogenic relationship between ovarian neoplasms spanning the clinicopathological spectrum from benign to malignant, the incidence of Ki-ras and p53 mutations was determined in 20 ovarian cystadenomas, 20 low malignant potential (LMP) tumors of the ovary, and 23 ovarian carcinomas. Using DNA extracted from paraffin embedded tissue, polymerase chain reaction amplification, designed restriction fragment length polymorphism analysis, and DNA sequencing, 1 cystadenoma (5%), 6 LMP tumors (30%), and 1 ovarian carcinoma (4%) demonstrated an activated Ki-ras gene. All of the Ki-ras mutations identified except one were GGT to GAT transversions at codon 12. One LMP tumor demonstrated a CAA to CAC transversion at codon 61. Using polymerase chain reaction/single strand conformational polymorphism, DNA sequencing, and immunohistochemistry, 11 ovarian carcinomas (48%) demonstrated a p53 mutation. These mutations included 5 missense, 2 nonsense, and 1 frameshift mutation located within exons 6-8 and 3 mutations that were identified only by immunohistochemical staining. No p53 mutations could be identified in cystadenomas or LMP tumors. Clinically, the presence of either a Ki-ras or p53 mutation was associated with advanced stage disease. The pattern of Ki-ras and p53 mutations appears to distinguish LMP tumors from invasive carcinomas and suggests that they may be separate biological entities.

Adolescent↗
PubMed1995

Adaptive mutation sequences reproduced by mismatch repair deficiency.

Adaptive reversions of a lac frameshift mutation in Escherichia coli are -1 deletions in small mononucleotide repeats, whereas growth-dependent reversions are heterogeneous. The adaptive mutations resemble instability of simple repeats, which, in hereditary colon cancer, in yeast, and in E. coli occurs in the absence of mismatch repair. The postulate that mismatch repair is disabled transiently during adaptive mutation in E. coli is supported here by the demonstration that the growth-dependent mutation spectrum can be made indistinguishable from adaptive mutations by disallowing mismatch repair during growth. Physiologically induced mismatch repair deficiency could be an important mutagenic mechanism in cancers and in evolution.

Bacterial Proteins↗
PubMed2005

Sequence variants in SLITRK1 are associated with Tourette's syndrome.

Tourette's syndrome (TS) is a genetically influenced developmental neuropsychiatric disorder characterized by chronic vocal and motor tics. We studied Slit and Trk-like 1 (SLITRK1) as a candidate gene on chromosome 13q31.1 because of its proximity to a de novo chromosomal inversion in a child with TS. Among 174 unrelated probands, we identified a frameshift mutation and two independent occurrences of the identical variant in the binding site for microRNA hsa-miR-189. These variants were absent from 3600 control chromosomes. SLITRK1 mRNA and hsa-miR-189 showed an overlapping expression pattern in brain regions previously implicated in TS. Wild-type SLITRK1, but not the frameshift mutant, enhanced dendritic growth in primary neuronal cultures. Collectively, these findings support the association of rare SLITRK1 sequence variants with TS.

3' Untranslated Regions↗