Two additional polymorphisms within the hypervariable MUC1 gene: association of alleles either side of the VNTR...

The gene MUC1 codes for a mucin-type glycoprotein and like most of the other mucin genes shows variable number tandem repeat (VNTR) polymorphism within the coding region. A polymorphism due to a G/A substitution in exon 2, responsible for a genetically determined variation in splicing of the MUC1 transcript, has also been reported (Ligtenberg et al. 1990, 1991). Here we describe the detection of this nucleotide substitution polymorphism by single stranded conformational analysis of genomic DNA and we also report a CA repeat polymorphism within intron 6 of the gene. Haplotypes were determined in a series of families and the common alleles of these two polymorphisms were found to be associated. These results support the notion that the VNTR polymorphism in the coding sequence of MUC1 is not caused by unequal reciprocal recombination at meiosis.