REDEFINITION OF THE CODING SEQUENCE OF THE MXI1 GENE AND IDENTIFICATION OF A POLYMORPHIC REPEAT IN THE 3' NONCODING REGION THAT ALLOWS THE DETECTION OF LOSS OF HETEROZYGOSITY OF CHROMOSOME 10Q25 IN GLIOBLASTOMAS

The MXI1 gene encodes a protein interacting with Max, a regulatory fac tor of the Myc oncogene, and is located on chromosome 10q25, a region showing frequent loss of heterozygosity in malignant gliomas. We have reassessed the coding sequence of MXI1 and found that, at the 3' end, the open reading frame is 28 codons shorter than previously described. We have also found an AAAAC polymorphic repeat (two alleles, 45% hete rozygosity) in the 3' non-coding region of the gene. Six anaplastic as trocytomas and nine glioblastomas, the most malignant form of glioma, were informative for this polymorphism. Loss of heterozygosity was dem onstrated in all glioblastomas, but not in the remaining tumors.