Screening of Nijmegen Breakage Syndrome 1 Mutations in Four Unrelated Families by Polymerase Chain Reaction Using Sequence-Specific Primers

Abstract

Nijmegen breakage syndrome (NBS) is an autosomal recessive disorder characterized by a marked predisposition to lymphoreticular malignancies. The rarity of the disease and the presence, in several cases, of a mild clinical phenotype make diagnosis difficult. The underlying gene, NBS1, consists of 16 exons and encodes nibrin, a member of the hMRE11/hRAD50/hNBS1 protein complex. In addition to the "Slavic mutation," 657del5, identified in more than 100 patients with NBS, 9 other mutations have been found in families of different ethnic origin. We have developed a polymerase chain reaction (PCR) method to rapidly detect the private mutations, 742insGG and 835del4, in exon 7 and the 900del25 mutation in exon 8 of the NBS1 gene. In particular, we designed NBS1-specific primers for wild-type and mutated alleles, and optimized a specific PCR protocol for each mutation. We used this method to analyze 4 unrelated NBS families, 3 from Italy and 1 from Morocco. We believe it could be a useful tool for: (1) confirming the NBS diagnosis in the presence of clinical signs of the disease; (2) identifying NBS heterozygotes and performing prenatal diagnosis in families with affected members; and (3) screening selected populations in which the frequency of NBS might be higher because of a founder effect.

Mutations in the Nijmegen Breakage Syndrome Gene in Medulloblastomas

“…Thus, the NBS1 mutations identified in the present study are likely to play significant roles in the pathogenesis of medulloblastomas. It is notable that any of the NBS1 mutations detected in medulloblastomas in the present study are novel mutations and have not been reported previously as germ-line mutations in NBS patients (10,12,51). The absence of a common mutation in exon 6 (657del5) reported previously in NBS patients (10) in any of the medulloblastomas in the present study suggests the importance of screening the whole NBS1 gene in human neoplasms.…”