Germline RET proto-oncogene mutations in two Taiwanese families with multiple endocrine neoplasia type 2A.

To elucidate the germline RET proto-oncogene mutations in Taiwanese families with multiple endocrine neoplasia type 2A (MEN 2A), we extracted DNA from peripheral blood leukocytes of 28 members of two families with MEN 2A. Oligonucleotide primers for exons 10 and 11 were used to analyze the nucleotide sequence of codons 609, 611, 618, and 620 of exon 10, and codon 634 of exon 11 of the RET proto-oncogene. Two fragments of genomic DNA were amplified by polymerase chain reaction (PCR). The amplified PCR products were separated and purified from primers and free nucleotides in agarose gels, and the expected 187-bp and 234-bp bands were cut from the gels and sequenced. Thirteen family members in the two MEN 2A kindreds had mutations in codon 634 of exon 11. In kindred 1 (15 members available for this study), a heterozygous codon 634 mutation in nine members and a homozygous codon 634 mutation in one member led to the substitution of Phe (TTC) for Cys (TGC). Three members of kindred 2 (13 members available for this study) had a heterozygous base pair change in codon 634, which led to the substitution of Arg (CGC) for Cys (TGC). In this study, we found two mutation events occurring in two MEN 2A kindreds and also discovered a homozygous point mutation in one woman that led to heterozygous mutations in all of her children.