title: Analysis of the NF1 gene by temperature gradient gel electrophoresis reveals a high incidence of mutations in exon 4b.
abstract: A total of 196 unrelated patients with neurofibromatosis type 1 (NF1) was screened for mutations in exons 4a-c of the NF1 gene by temperature gradient gel electrophoresis (TGGE) of polymerase chain reaction (PCR)-amplified genomic DNA fragments using intron-based primers. DNA samples with abnormal TGGE band patterns were subjected to sequence analysis. Sequence alterations were identified in ten patients (5.1%): 496delGT (1), 499delTGTT (4), T528A = D176E (2), T539A = L180X (1), 540insA (1), C574T = R192X (1). Thus, a total of six different mutations was identified in exon 4b but none in exons 4a and 4c. Only the missense mutation D176E, which we assume to be a nonpathogenic polymorphism, and the 4-base pair (bp) deletion 499delTGTT have been described before. The reason for the high incidence of mutations in exon 4b is obviously a tetranucleotide tandem repeat comprising nucleotides 495-502 (TGTTTGTT) that may give rise to slipped mispairing and subsequent deletion of one repeat unit during replication. Additionally, the recurrent 4 bp deletion was found as a second hit in a malignant schwannoma of a further NF1 patient, suggesting that microlesions may be as frequent among somatic as among germline mutations. This is the first report of a systematic study of NF1 exons 4a-c in a large group of NF1 patients.
authors.affiliation: Institut für Medizinische Genetik, Universitätsklinikum Charité, Berlin, Germany.
authors.forename: M R
authors.initials: MR
authors.lastname: Toliat
authors.forename: F
authors.initials: F
authors.lastname: Erdogan
authors.forename: A
authors.initials: A
authors.lastname: Gewies
authors.forename: R
authors.initials: R
authors.lastname: Fahsold
authors.forename: A
authors.initials: A
authors.lastname: Buske
authors.forename: S
authors.initials: S
authors.lastname: Tinschert
authors.forename: P
authors.initials: P
authors.lastname: Nürnberg
mesh_terms: D001483:Base Sequence; D017931:DNA Primers; D004591:Electrophoresis, Polyacrylamide Gel / Q000379:methods*; D005091:Exons; D016514:Genes, Neurofibromatosis 1; D006801:Humans; D009154:Mutation; D012680:Sensitivity and Specificity; D013696:Temperature
chemical_list: D017931:DNA Primers