Analysis of the NF1 gene by temperature gradient gel electrophoresis reveals a high incidence of mutations in exon 4b

Electrophoresis. 2000 Feb;21(3):541-4. doi: 10.1002/(SICI)1522-2683(20000201)21:3<541::AID-ELPS541>3.0.CO;2-L.


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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Base Sequence
  • DNA Primers
  • Electrophoresis, Polyacrylamide Gel / methods*
  • Exons*
  • Genes, Neurofibromatosis 1*
  • Humans
  • Mutation*
  • Sensitivity and Specificity
  • Temperature


  • DNA Primers