title: Chromosome instability and nibrin protein variants in NBS heterozygotes.
abstract: The frequency of spontaneous chromosome abnormalities in peripheral blood lymphocytes and the X-ray G2 sensitivity in lymphoblastoid cell lines (LCL) have been evaluated in heterozygous subjects from three unrelated Nijmegen Breakage Syndrome (NBS) families, characterised by different mutations in the NBS1 gene. In all the 13 NBS heterozygotes analysed, we found spontaneous chromosome instability consisting in chromosome and chromatid breakages and rearrangements, while radiosensitivity was similar to that of control LCLs in seven out of eight tested NBS heterozygotes. The densitometric analysis of nibrin by immunoblotting indicated only a slight reduction in some of the LCLs from NBS carriers, whereas the immunoprecipitation assay appears a more reliable tool to detect NBS carriers. By means of immunoprecipitation, we investigated two homozygous and four heterozygous subjects. In the cells of the NBS patient 668, with the mutation 900del25, an alternative form of nibrin with a molecular weight of approximately 55 kDa has been detected. This variant protein, together with the normal p95, was also found in the LCL 34 established from a carrier of the same family. Signals of nibrin with a molecular weight lower than 95 kDa, but higher than that observed in LCLs 668 and 34, were detected also in three carriers from the family with mutation 835del4.
authors.affiliation: Universita degli Studi di Roma, Roma Tre, Rome, Italy.
authors.forename: Caterina
authors.initials: C
authors.lastname: Tanzanella
authors.forename: Antonio
authors.initials: A
authors.lastname: Antoccia
authors.forename: Emanuela
authors.initials: E
authors.lastname: Spadoni
authors.forename: Alessandra
authors.initials: A
authors.lastname: di Masi
authors.forename: Vanna
authors.initials: V
authors.lastname: Pecile
authors.forename: Eliana
authors.initials: E
authors.lastname: Demori
authors.forename: Raymonda
authors.initials: R
authors.lastname: Varon
authors.forename: Gian Luigi
authors.initials: GL
authors.lastname: Marseglia
authors.forename: Luciano
authors.initials: L
authors.lastname: Tiepolo
authors.forename: Paola
authors.initials: P
authors.lastname: Maraschio
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D015153:Blotting, Western; D018797:Cell Cycle Proteins / Q000737:chemistry / Q000235:genetics*; D002648:Child; D002675:Child, Preschool; D019457:Chromosome Breakage / Q000235:genetics*; D002873:Chromosome Fragility / Q000235:genetics*; D005260:Female; D014644:Genetic Variation; D006801:Humans; D015151:Immunoblotting; D008214:Lymphocytes / Q000097:blood / Q000737:chemistry / Q000000981:diagnostic imaging*; D008297:Male; D008875:Middle Aged; D009687:Nuclear Proteins / Q000737:chemistry / Q000235:genetics*; D011233:Precipitin Tests; D011859:Radiography
chemical_list: D018797:Cell Cycle Proteins; C112156:NBN protein, human; D009687:Nuclear Proteins