3 NOVEL MUTATIONS OF THE NF1 GENE DETECTED BY TEMPERATURE-GRADIENT GEL-ELECTROPHORESIS OF EXON-5 AND EXON-8

We screened a total of 100 unrelated patients with neurofibromatosis t ype 1 (NF1) for mutations in exons 5 and 8 of the NF1 gene using tempe rature gradient gel electrophoresis (TGGE). Careful interpretation of exon 5 TGGE patterns was necessary due to interference by an exonic po lymorphism. Three novel mutations were identified: a stop mutation in exon 5 (Q239X) caused by a C-->T transition at cDNA nucleotide positio n 715, a transition at the invariant G of the splice acceptor site in intron 4c (G655-1A), and a transversion at the invariant G of the spli ce donor site in intron 8 (G1185+1T). Analysis of mRNA revealed the pr edicted abnormal splice products. While skipping of exon 5 causes a sh ift 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 wi th the predicted protein product being shortened by 41 amino acids.