Novel and recurrent mutations in the TAT gene in Tunisian families affected with Richner–Hanhart Syndrome

Tyrosinemia type II, also designated as oculocutaneous tyrosinemia or Richner–Hanhart syndrome (RHS), is a very rare autosomal recessive disorder. In the present study, we report clinical features and molecular genetic investigation of the tyrosine aminotransferase (TAT) gene in two young patients, both born to consanguineous unions between first-degree cousins. These two unrelated families originated from Northern and Southern Tunisia. The clinical diagnosis was based on the observation of several complications related to Richner–Hanhart syndrome: recurrent eye redness, tearing and burning pain, photophobia, bilateral pseudodendritic keratitis, an erythematous and painful focal palmo-plantar hyperkeratosis and a mild delay of mental development. The diagnosis was confirmed by biochemical analysis. Sequencing of the TAT gene revealed the presence of a previously reported missense mutation (c.452G > A, p.Cys151Tyr) in a Tunisian family, and a novel G duplication (c.869dupG, p.Trp291Leufs*6). Early diagnosis of RHS and protein-restricted diet are crucial to reduce the risk and the severity of long-term complications of hypertyrosinemia such as intellectual disability.     

β-thalassemia mutations in the Portuguese population

Summary In this study we have carried out haplotype analysis on the -globin gene cluster and characterized the -thalassemia mutation by oligonucleotide hybridization in 14 patients with thalassemia major and 5 with sickle cell/-thalassemia originating from southern Portugal. We found that three mutations, namely the °-39, ° IVS-1 nt 1 and ⁺ IVS-1 nt 110 are prevalent accounting for 53%, 32% and 10% of the -thalassemia chromosomes respectively. In general each mutation was associated with a specific chromosomal haplotype; the ° mutation, however, was linked to three different haplotypes. These results indicate that three oligo-probes complementary to the most common mutations allow prenatal diagnosis by oligonucleotide analysis in 96% of the couples at risk of having offspring with thalassemia major in southern Portugal.     

A high proportion of mutations in the BRCA1 gene in German breast/ovarian cancer families with clustering of mutations in the 3′ third of the gene

We have analyzed 61 German breast and breast/ovarian cancer families for BRCA1 mutations using single-strand conformation polymorphism analysis (SSCP) followed by sequencing. Forty-seven of the families had at least three cases (at least two under 60 years) and 14 families had only two cases of breast/ovarian cancer (at least one under 50 years). Twenty-eight families were breast/ovarian and 33 were breast cancer-only families. Eighteen mutations in BRCA1 were detected in 11/28 breast/ovarian cancer families and 7/33 breast cancer families and none in the families with only two cases. We identified 17 truncation mutations (8 frameshift, 7 nonsense and 2 splice variants) and one missense mutation. Seven of these are novel and two, the 5382insC and 5622C→T mutations, occurred in two apparently unrelated families. The genotype of the two families with the 5382insC mutation is compatible with the rare haplotype segregating with the 5382insC mutation in different populations, further supporting its European origin. One unclassified missense alteration, R841W, was found in one family but did not segregate with the disease, suggesting that it is more likely a polymorphism. We also report and discuss the sequence of several new unclassified single-nucleotide changes first identified by SSCP. Of the 18 mutations, 13 occurred in the 3′ third of the gene (end of exon 11–24) and ovarian cancers were found in eight of these families. Received: 5 February 1998 / Accepted: 7 April 1998     

Mediterranean types of β-thalassemia in the German population

Summary Forty -thalassemia genes from unrelated German heterozygotes with no known foreign ancestry were examined using the oligonucleotide technique and DNA restriction analysis, with the aim of determining the contribution of Mediterranean -thalassemia mutations to the prevalence of this trait in the German population. Of the 40 -thalassemia genes, 26 were identified as Mediterranean types (20 39 nonsense, 3 IVS2 nt 110, 2 IVS2 nt1, 1 IVS1 ntl GA). The geographic distribution of the birthplaces of the probands' grandparents revealed no difference in the proportion of Mediterranean and unidentified -thalassemia genes in the west and the north of Germany.     

Heterogeneous mutations in the glycogen-debranching enzyme gene are responsible for glycogen storage disease type IIIa in Japan

Glycogen storage disease type IIIa (GSD IIIa) is an autosomal recessive disorder caused by deficiency of the glycogen-debranching enzyme (AGL). Recent studies of the AGL gene have revealed the prevalent mutations in North African Jewish and Caucasian populations, but whether these common mutations are present in other ethnic groups remains unclear. We have investigated eight Japanese GSD IIIa patients from seven families and identified seven mutations, including one splicing mutation (IVS 14+1G-->T) previously reported by us, together with six novel ones: a nonsense mutation (L124X), a splice site mutation (IVS29-1G-->C), a 1-bp deletion (587delC), a 2-bp deletion (4216-4217delAG), a 1-bp insertion (2072-2073insA), and a 3-bp insertion (4735-4736insTAT). The last mutation results in insertion of a tyrosine residue at a putative glycogen-binding site, and the rest are predicted to cause synthesis of truncated proteins lacking the glycogen-binding site at the carboxyl terminal. Thirteen novel polymorphisms have also been revealed in this study: three amino acid substitutions (R387Q, G1115R, and E1343 K), one silent point mutation (L298L), one nucleotide change in the 5'-noncoding region, and eight nucleotide changes in introns. Haplotype analysis with combinations of these polymorphic markers showed L124X, IVS14+1G-->T, and 4216-4217delAG to be on different haplotypes. These results demonstrate the importance of the integrity of the carboxy terminal domain in the AGL protein and the molecular heterogeneity of GSD IIIa in Japan.     

β-Globin gene polymorphism in the Saudi Arab population

Summary DNA mapping with the restriction endonucleases, Hpa I and Mst II, has been used to investigate -globin gene polymorphism in the Saudi Arab population. Using Hpa I digestion, 13.0kb and 7.6kb fragments were found in association with the ^A and ^S genes. The frequency of the polymorphic forms in two regions investigated vary significantly. In Al-Hafouf and the surrounding villages, situated in the Eastern Province of Saudi Arabia, the frequencies of association of the ^S gene with the Hpa I 7.6kb, 7.0kb, and 13.0kb fragments were 0.866, 0.043, and 0.071, respectively. The frequency of association of ^A with the 7.6kb and 13.0kb fragments resulting from the Hpa I digestion were 0.875 and 0.125. In Khaiber, Tehamat-Aseer, and surrounding villages, in the Western Province, the frequency of association of ^S with 7.6kb, 7.0kb, and 13.0kb fragments were 0.836, 0.027, and 0.0136, respectively, while that of ^S was 0.250 and 0.750 with 7.0kb and 13.0kb Hpa I fragments, respectively. Using Mst II digestion, ^A was found to be linked to a 1.15kb fragment, while ^s was linked to a 1.35kb fragment. The normal (Hb AA), heterozygotes (Hb AS), and homozygotes (Hb SS) gave 1.15, 1.15/1.35, and 1.35kb fragments, respectively. The results of this study show extensive polymorphism at the Hpa I restriction site of the ^A and ^S globin genes with the different polymorphic forms existing at a variable frequency in different regions of Saudi Arabia.     

Connexin 26 (GJB2) mutations in the Turkish population: implications for the origin and high frequency of the 35delG mutation in Caucasians

Mutations in the Connexin 26 (GJB2/Cx26) gene are responsible for more than half of all cases of prelingual non-syndromic recessive deafness in many Caucasian populations. To determine the importance of Cx26 mutations as a cause of deafness in Turks we screened 11 families with prelingual non-syndromic deafness, seven (64%) of which were found to carry the 35delG mutation. We subsequently screened 674 Turkish subjects with no known hearing loss and found twelve 35delG heterozygotes (1.78%; 95% confidence interval: 0.9%-3%) but no examples of the 167delT mutation. To search for possible founder effects, we typed chromosomes carrying the 35delG mutation for closely linked polymorphic markers in samples from Turkey and United States and compared the allele frequencies with those of hearing subjects. The data showed a modest degree of disequilibrium in both populations. Analyses of two pedigrees from Turkey demonstrated both conserved and different haplotypes, suggesting possible founder effects and multiple origins of the 35delG mutation.     

Epstein syndrome: another renal disorder with mutations in the nonmuscle myosin heavy chain 9 gene

Epstein syndrome (EPTS) is an autosomal dominant disease characterized by nephritis, mild hearing loss, and thrombocytopenia with giant platelets. Renal and hearing abnormalities are indistinguishable from those observed in Fechtner syndrome (FTNS), an Alport-like variant. EPTS macrothrombocytopenia is similar to that described in FTNS, May-Hegglin anomaly (MHA), and Sebastian syndrome (SBS), three disorders caused by mutations in the nonmuscle heavy chain myosin IIA ( MYH9). Unlike FTNS, MHA, and SBS, EPTS does not show inclusion bodies in the leukocytes. The clinical features of EPTS and the chromosomal localization of the respective gene in the same region as MYH9 suggest that this disorder is allelic with the other giant platelet disorders. We identified a MYH9 missense mutation in two EPTS familial cases. In both families, an R702H substitution was found, probably inducing conformational changes to the myosin head. A different amino acid substitution at the same codon (R702C) has been previously identified in FTNS. On the basis of predictions from molecular modeling of the X-ray crystallographic structure of chick smooth muscle myosin, the mutated thiol reactive group of R702C may lead to intermolecular disulfide bridges, with the consequent formation of the inclusions typical of FTNS. On the contrary, the R702H mutation does not allow the protein to aggregate and thus to generate "D?hle-like" bodies, which are indeed absent in EPTS. In conclusion, our results extend the allelic heterogeneity of MYH9 mutations to another clinical syndrome and contribute to the clarification of the pathogenesis of the various inherited giant platelet disorders.     

Identification of novel Asian Indian and Japanese mutations causing β-thalassaemia in the Egyptian population

β-thalassaemia is a major health problem in Egypt. It has been estimated that of the 1.5 million live births, 1000 children with β-thalassaemia major are born annually. Although the available treatment has increased the life expectancy of patients, it is still unsatisfactory and represents a significant drain on the country’s resources. National screening and prenatal diagnosis programmes can be provided in Egypt once the spectrum of β-thalassaemia mutations has been identified within the Egyptian population. We have examined 16 DNA samples with 21 β-thalassaemia mutations that remained unidentified in a study of 54 patients reported by Rady and colleagues in 1996. Using the polymerase chain reaction and single strand conformation analysis we identified the following changes: frameshift (FS) codon (CD) 8/9 (+G), 4 FS CD 29 (–G) and 2 novel mutations in exon I (15 CD 22 A-C and 1 FS CD 28 –C). In addition, a silent, probably polymorphic mutation, CD 17 G-A was present in all chromosomes. Received: 19 August 1996 / Revised: 21 September 1996     

Tyrosinase gene mutations in oculocutaneous albinism 1 (OCA1): definition of the phenotype

Oculocutaneous albinism (OCA) is a common human genetic condition resulting from mutations in at least twelve different genes. OCA1 results from mutations of the tyrosinase gene and presents with the life-long absence of melanin pigment after birth (OCA1A) or with the development of minimal-to-moderate amounts of cutaneous and ocular pigment (OCA1B). Other types of OCA have variable amounts of cutaneous and ocular pigment. We hypothesized that white hair at birth indicates OCA1 and tested this in a sample of 120 probands with OCA and white hair at birth. We found that 102 (85%) of the probands had OCA1 with one or two identifiable tyrosinase gene mutations, with 169 (83%) of the 204 OCA1 tyrosinase gene alleles having identifiable mutations and 35 (17%) having no identifiable change in the coding, splice junction, or proximal promoter regions of the gene. The inability to identify the mutation was more common with OCA1B (24/35, 69%) than with OCA1A (11/35, 31%) alleles. Seven probands with no tyrosinase gene mutations were found to have OCA2 with one or two P gene mutations, and in eleven, no mutations were detected in either gene. We conclude that (1) the presence of white hair at birth is a useful clinical tool suggesting OCA1 in a child or adult with OCA, although OCA2 may also have this presentation; (2) the molecular analysis of the tyrosinase and P genes are necessary for precise diagnosis; and (3) the presence of alleles without identifiable mutations of the tyrosinase gene, particularly in OCA1B, suggests that more complex mutation mechanisms of this gene are common in OCA.Electronic database Information: accession numbers and URLs for data presented in this article are as follows:Albinism Database, , for a list of published mutations of the tyrosinase geneOnline Mendelian Inheritance in Man (OMIM), , for OCA1 (MIM 203100), OCA2 (MIM 203200)     

Fine mapping and candidate gene analysis of a green-revertible albino gene gra（t） in rice

Green-revertible albino is a novel type of chlorophyll deficiency in rice （Oryza sativa L.）, which is helpful for further research in chlorophyll synthesis and chloroplast development to illuminate their molecular mechanism. In the previous study, we had reported a single recessive gene, gra（t）, controlling this trait on the long arm of chromosome 2. In this paper, we mapped the gra（t） gene using 1,936 recessive individuals with albino phenotype in the F2 population derived from the cross between themo-photoperiod-sensitive genic male-sterile （T/PGMS） line Pei＇ai 64S and the spontaneous mutant Qiufeng M. Eventually, it was located to a confined region of 42.4 kb flanked by two microsatellite markers RM2-97 and RM13553. Based on the annotation results of RiceGAAS system, 11 open reading frames （ORFs） were predicted in this region. Among them, ORF6 was the most possible gene related to chloroplast development, which encoded the chloroplast protein synthesis elongation factor Tu in rice. Therefore, we designated it as the candidate gene of gra（t）. Sequence analysis indicated that only one base substitution C to T occurred in the coding region, which caused a missense mutation （Thr to Ile） in gra（t） mutant. These results are very valuable for further study on gra（t） gene.     

NPC1 gene mutations in Japanese patients with Niemann-Pick disease type C

Complementary and genomic DNAs isolated from the fibroblasts of 10 Japanese (7 late infantile, 2 juvenile, and 1 adult form of the disease) and one Caucasian patient with Niemann-Pick disease type C were analyzed for mutations in the NPC1 gene. Fourteen novel mutations were found including small deletions and point mutations. A one-base deletion and a point mutation caused splicing errors. The mutations were not clustered in any particular region of the gene and were found both in and out of the transmembrane domains. Three patients were homozygous, five were compound heterozygous, and the remaining three were suspected of being compound hetrozygous with an unknown error in one of their NPC1 alleles. Of the 14 mutations, the G1553A substitution that caused a splicing error of exon 9 appeared to be relatively common in Japanese patients, because two patients were homozygous and one patient was compound heterozygous for this mutation. Electronic Publication     

New mutations in the human p53 gene — a regulator of the cell cycle and carcinogenesis

Mutations in the tumor suppressor gene p53 often lead to disarrangement of the cell cycle and of genetic integrity control of cells that may contribute to tumor development. We studied p53 gene mutations in 26 primary tumors of colorectal cancer patients. Mutations in p53 were found in 17 tumors (65.4%). All point mutations affected the DNA binding domain of p53 and were localized in exons 4-8 of the gene. Mutant p53 isoforms with altered domain structure and/or with alternative C-terminus arising from frameshift mutations or abnormal splicing were found in six tumors. Mutations Leu111Gln and Ser127Phe were shown in colorectal cancer for the first time. Isoforms p53-305 with C(4) insertion in codons 300/301 and p53i9* including an additional 44 nucleotides of the 3 -end of intron 9 were discovered for the first time. Mutations of p53 were associated with lymph node metastases and III/IV stage of tumors that are signs of unfavorable prognosis in colorectal cancer.     

Two novel missense mutations in the cystathionine β-synthase gene in homocystinuric patients

Direct sequencing of the coding region of the cystathionine -synthase (CBS) gene in two homocystinuric patients revealed the presence of two novel missense mutations. The first mutation, a 1111G A transition, resulted in the substitution of the evolutionary conserved valine-371 by a methionine residue (V371M) and created a new NlaIII restriction site. The second mutation, a GA transition at base-pair 494, resulted in an amino acid change from cysteine to tyrosine (C165Y) and abolished a BsoFI restriction site. Both mutations were found in a compound heterozygous state with the previously described 833T C transition.     

Novel mutations in β-tubulin gene in Trichoderma harzianum mutants resistant to methyl benzimidazol-2-YL carbamate

Twelve low resistant (LR) mutants of Trichoderma harzianum with the capability of grow fast at 0.8 μg/mL methyl benzimidazol-2-yl carbamate (MBC) were obtained using UV mutagenesis. MR and HR mutants which could grow fast at 10 and 100 μg/mL MBC, respectively, were isolated by step-up selection protocols in which UV-treated mutants were induced and mycelial sector screening was made in plates with growth medium. Subsequently, β-tubulin genes of 14 mutants were cloned to describe the molecular lesion likely to be responsible for MBC resistance. Comparison of the β-tubulin sequences of the mutant and sensitive strains of T. harzianum revealed 2 new MBC-binding sites differed from those in other plant pathogens. A single mutation at amino acid 168, having Phe (TTC) instead of Ser (TCC), was demonstrated for the HR mutant; a double mutation in amino acid 13 resulting in the substitution of Gly (GGC) by Val (GTG) was observed in β-tubulin gene of MR mutant. On the other hand, no substitutions were identified in the β-tubulin gene and its 5’-flanking regions in 12 LR mutants of T. harzianum.     

Screening of mitochondrial mutations and insertion–deletion polymorphism in gestational diabetes mellitus in the Asian Indian population

In this study we scrutinized the association between the A8344G/A3243G mutations and a 9-bp deletion polymorphism with gestational diabetes mellitus (GDM) in an Asian Indian population. The A3243G mutation in the mitochondrial tRNA^Leu(UUR) causes mitochondrial encephalopathy myopathy, lactic acidosis, and stroke-like episodes (MELAS), while the A8344G mutation in tRNA^Lys causes myoclonus epilepsy with ragged red fibers (MERRF). We screened 140 pregnant women diagnosed with GDM and 140 non-GDM participants for these mutations by PCR-RFLP analysis. Both A3243G and A8344G were associated with GDM (A3243: OR-3.667, 95% CI = 1.001–13.43, p = 0.03; A8344G: OR-11.00, 95% CI = 0.6026–200.8, p = 0.04). Mitochondrial DNA mutations contribute to the development of GDM. Our results conclude that mitochondrial mutations are associated with the GDM women in our population. Thus it is important to screen other mitochondrial mutations in the GDM women.