Identification and characterization of the multiple endocrine neoplasia type 1 (MEN1) gene

For nearly a decade since the mapping of the multiple endocrine neoplasia type 1 (MEN1) locus to 11q13 and the suggestion that it is a tumour suppressor gene, efforts have been made to identify the gene responsible for this familial cancer syndrome. Recently, we have identified the MEN1 gene by the positional cloning approach. This effort involved construction of a 2.8- Mb physical map (D11S480-D11S913) based primarily on a bacterial clone contig. Using these resources, 20 new polymorphic markers were isolated which helped to reduce the interval for candidate genes by haplotype analysis in families and by loss of heterozygosity (LOH) studies in approximately 200 tumours, utilizing laser-assisted microdissection to obtain tumour cells with minimal or no admixture by normal cells. The interval was narrowed by LOH to only 300 kb, and nearly 20 new transcripts that map to this region of 11q13 were isolated and characterized. One of the transcripts was found by dideoxyfingerprinting and cycle sequencing to harbour deleterious germline mutations in affected individuals from MEN-1 kindreds and therefore identified as the MEN1 gene. The type of germline mutations and the identification of mutations in sporadic tumours support the Knudson's two- hit model of tumorigenesis for MEN1. Efforts are being made to identify the function of the MEN1 gene-encoded protein, menin, and to study its role in tumorigenesis.