The loss of a polymorphic glycosylation site caused by Thr-927-->Ile is linked to a second polymorphic Val-816-->Ile substitution in lysosomal alpha-glucosidase of American blacks

The 1396del A mutation and a missense mutation or a rare polymorphism of the WRN gene detected in a French Werner family with a severe phenotype and a case of an unusual vulvar cancer. Mutations in brief no. 136. Online

The Werner's syndrome (WS) is a rare recessive disease characterized by an early onset of geriatric disorders. The Werner's syndrome gene (WRN) recently cloned, encodes for an helicase and therefore plays a role in DNA metabolism and DNA repair. Here, we report the study of a French family with two affected members and numerous cancers. Using the protein truncation test and sequencing, we identified a homozygous mutation in the WRN gene. This mutation generates a frame shift leading to a very short 391 amino acids truncated protein without the helicase motif. A particularly severe phenotype of the affected patient was associated with an unusual vulvar cancer traditionaly observed in elderly patients and therefore likely to be related to the Werner's syndrome. An additional substitution of G for A at nucleotidic position 1392 was also described. We suggest that a relation between genotype and phenotype could exist in the studied family.

Molecular genetic study of Pompe disease in Chinese patients in Taiwan

Pompe disease is caused by mutations in the acid alpha-glucosidase (GAA) gene. Multiple kinds of mutations in the GAA gene have been reported worldwide. In order to elucidate the molecular basis of the disease in Taiwanese patients of Chinese origin, we have recruited 11 unrelated families who had at least one member with Pompe disease for study. We used 16 pairs of oligonucleotide primers to amplify all the coding regions from exon 2 to 20 in the family members. The coding regions were sequenced on both the sense and antisense strands. We identified 7 different mutations in 17 alleles but failed to identify the defects in the other 5 alleles. The most common defect was D645E (Asp645Glu), accounting for 36% (8/22 alleles) of mutations, followed by G615R (Gly615Arg) (3 alleles); 1411del4 (Glu471-shift) (2 alleles); and one allele each of R600H (Arg600His); deltaN675 (deltaAsn675); 2380delC (Arg794-shift) and 2815delGT (Val939-shift). The molecular defects of Pompe disease are highly heterogeneous in Chinese. Characterization of the molecular defects of the disease is useful for a genotype-phenotype correlation and for genetic counseling and prenatal diagnosis.

Genetic defects in patients with glycogenosis type II (acid maltase deficiency)

Inherited deficiency of acid alpha-glucosidase (acid maltase, GAA) leads to glycogen storage disease type II. Clinical manifestations and prognosis of the disease depend on the age of onset and tissue involvement. GAA deficiency is extremely heterogeneous, ranging from a rapidly progressive fatal infantile-onset form to a slowly progressive adult-onset myopathy associated with respiratory insufficiency. Biochemical and immunochemical studies of the biosynthesis of the enzyme in GAA-deficient patients established the molecular diversity of the disease. Cloning and sequencing of the cDNA and the gene provided the basis for genetic analysis of the patients with different phenotypes. In this article, we summarize the data on mutations in the GAA gene and discuss the correlation between the genotype and phenotypic expression of the disease.