THE MUTATION STATUS OF PAX3 AND P53 GENES IN MEDULLOBLASTOMA

The p53 and PAX3 genes were examined by PCR, SSCP and DNA sequencing m ethods in 50 and 58 paraffin-embedded medullablastoma tissues, respect ively. Four novel mutations were identified among these samples in exo n 5 of the p53 gene. Two tumours showed a G to A transition. One heter ozygous mutation was located on codon 158 which changed the encoded am ino acid from Arg (CGC) to His (CAC). Another was located on codon 174 and replaced AGG (Arg) with AAG (Lys). There was a single base deleti on of guanine located on codon 160 in another two samples, causing a f rameshift. This is the first study of mutation status of PAX gene in m edulloblastoma wherein only one polymorphism was identified in this ge ne. The polymorphism changed codon 43 from GGC to GGT but both encoded glycine.