Genetic analysis demonstrated the absence of an usual FMTC mutation and the presence of a germline 9-bp duplication in RET exon 8 in the heterozygous state in all patients with MTC.
Mutations in nucleotide sequences encoding one of three specific cysteine residues in the extracellular domain of the RET protein were found in 33 of the 34 MEN2A patients and in five of the six FMTC patients examined.
Cys 618 Arg mutation in the RET proto-oncogene associated with familial medullary thyroid carcinoma and maternally transmitted Hirschsprung's disease suggesting a role for imprinting.
Because the new RET alleles described here involve cysteine residues in a region of protein previously associated with FMTC and MEN2A, it is very likely that they represent mutations that predispose to the development of MTC.
Identification of the RET mutation in the Dutch population with hereditary C-cell carcinoma facilitates genetic testing for families or individuals at risk for MEN 2A, FMTC, and MEN 2B.
Diagnosis of multiple endocrine neoplasia [MEN] 2A, 2B and familial medullary thyroid cancer [FMTC] by multiplex PCR and heteroduplex analyses of RET proto-oncogene mutations.
We now report a missense mutation in the intracellular tyrosine kinase domain of RET in the germline of a family with FMTC that does not have a cysteine codon mutation.
Six different missense germline mutations were identified at cysteine residues 618, 630, and 634 of the cysteine-rich extracellular RET domain encoded by exons 10 and 11 in all patients with FMTC and MEN 2A.
Although direct sequencing of RET exons 10 and 11 allows the identification of a constitutional mutation in a large proportion of MEN 2A and FMTC families, our data sustain the existence of other MTC predisposing mutations elsewhere in RET coding or regulating region.
The variants were observed only in the DNA of individuals who were either affected or who had inherited the MEN2A or FMTC allele as determined by haplotyping experiments.