Three novel mutations of the NF1 gene detected by temperature gradient gel electrophoresis of exons 5 and 8.

We screened a total of 100 unrelated patients with neurofibromatosis type 1 (NF1) for mutations on exons 5 and 8 of the NF1 gene using temperature gradient gel electrophoresis (TGGE). Careful interpretation of exon 5 TGGE patterns was necessary due to interference by an exonic polymorphism. Three novel mutations were identified: a stop mutation in exon 5 (Q239X) caused by a C-->T transition at cDNA nucleotide position 715, a transition at the invariant G of the splice acceptor site in the intron 4c (G655-1A), and a transversion at the invariant G of the splice donor site in intron 8 (G1185 + 1T). Analysis of mRNA revealed the predicted abnormal splice products. While skipping of exon 5 causes a shift in the reading frame with a premature stop codon downstream in the middle of exon 6, skipping of exon 8 leads to an in-frame deletion with the predicted protein product being shortened by 41 amino acids.