Mutational analysis and functional correlation with phenotype in German patients with childhood-type hypophosphatasia

Citation
H. Orimo et al., Mutational analysis and functional correlation with phenotype in German patients with childhood-type hypophosphatasia, J BONE MIN, 16(12), 2001, pp. 2313-2319
Citations number
32
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Endocrinology, Nutrition & Metabolism
Journal title
JOURNAL OF BONE AND MINERAL RESEARCH
ISSN journal
0884-0431 → ACNP
Volume
16
Issue
12
Year of publication
2001
Pages
2313 - 2319
Database
ISI
SICI code
0884-0431(200112)16:12<2313:MAAFCW>2.0.ZU;2-6
Abstract
The tissue-nonspecific alkaline phosphatase (TNSALP) gene from five German family members with childhood-type hypophosphatasia (HOPS) was analyzed usi ng the polymerase chain reaction-single strand conformation polymorphism (P CR-SSCP)-direct sequencing method. Four novel missense mutations (T51M, R54 S, L258P, and R374H) and two that had been described previously (A160T and R206W) were detected in the respective patients. Mutation A160T was detecte d in 3 distinct patients, and a polymorphism V505A that had been described previously was detected in the same allele as L258P mutation in 1 patient a nd in 2 fathers whose V505A alleles were not transmitted to the probands. N o other mutations were found in 2 patients. Transient expression of the mut ant proteins in COS-1 cells showed that the four novel mutations and R206W were severe alleles, whereas A160T was a moderate allele. Analysis of its e nzymatic activity and genetic transmission patterns confirmed that V505A wa s a polymorphism. Immunoprecipitation of the transiently expressed proteins showed that levels of the 80-kDa mature form of the enzyme were diminished or absent with the severe alleles; instead, levels of high-molecular mass disulfide-linked aggregates were increased. These results suggest that in c ompound heterozygotes, the combination of severe and moderate alleles may c ombine to cause the mild phenotype seen in childhood-type HOPS.