2 NOVEL MUTATIONS IN EXON-19A AND EXON-20 AND A BSAL POLYMORPHISM IN A NEWLY CHARACTERIZED INTRON OF THE NEUROFIBROMATOSIS TYPE-1 GENE

Neurofibromatosis type 1 (NF1) is a common autosomal dominant disorder . It is caused by mutations in the NF1 gene, which comprises 60 exons and is located on chromosome 17q11.2. A total of 170 unrelated NF1 pat ients were screened for mutations in four exons by temperature-gradien t gel electrophoresis. Preparatory work revealed the presence of a pre viously uncharacterized intron (19a) in what was previously designated exon 19; this allowed us to develop assays for genomic mutation scree ning in the newly defined exons 19a and 19b. Two novel NF1 mutations w ere detected: a single-base insertion in exon 19a creating a frameshif t, and a second mutation affecting the splice donor site of intron 20 and leading to skipping of exon 20. A novel BsaBI polymorphism was ide ntified in intron 19a.