The minisequencing method: a simple strategy for genetic screening of MEN 2 families

Using this mutation detection method we were able to reproduce in all cases, representative of 7 families, the information previously obtained by direct sequencing of PCR products. Depending on the number of primers used in the minisequencing reaction, we were able to interrogate either only one nucleotide of the target codon or the three nucleotides simultaneously.This technique appears as a simple, rapid and efficient method for genetic screening of MEN 2 families. It can be utilized to seek for unknown mutations at specific codons or to screen for previously identified mutations and is therefore of interest to study index cases or individuals at risk. Results suggest that complete sequencing is unnecessary.The multiple endocrine neoplasia (MEN) type 2 syndromes comprise three related autosomal dominant cancer syndromes [1]. MEN 2A is characterised by medullary thyroid carcinoma (MTC), pheochromocytoma and parathyroid hyperplasia or adenoma [2]. MEN 2B is similar to MEN 2A except that hyperparathyroidism is rare and characteristic abnormalities such as marfanoid habitus, mucocutaneous and intestinal tract ganglioneuromatosis are present [3]. In familial medullary thyroid carcinoma (FMTC), medullary thyroid carcinoma is the only manifestation [4].Germline mutations of the RET proto oncogene, which encodes for a receptor tyrosine kinase, are the underlying cause of MEN 2 [5-7].The majority of mutations in MEN 2A and FMTC families are found in 1 of 5 cysteine codons (609, 611, 618 and 620 in exon 10 and 634 in exon 11) that encode part of the extracellular cysteine rich domain [1,8,9]. Codon 634 mutations are the most common in MEN 2A families occurring in 85% of these families [1]. Mutations in FMTC families are evenly distributed among the 5 cysteine codons [1,8]. Less frequently, mutations are found elsewhere in the RET[10-13]. The great majority of MEN 2B families (95%) present the same mutation (ATG→ ACG) at codon 918 in exon 16 [1]. In a few cases of MEN 2B fam