Genetic analysis of seven Mediterranean families with multiple endocrine neoplasia type 2A.
OBJECTIVE
Genetic analysis is now essential for the accurate screening of families with multiple endocrine neoplasia type 2 (MEN2). We present the genetic analyses by both haplotype and direct RET proto-oncogene mutation analysis in seven Mediterranean MEN 2A families and have compared these results with biochemical screening tests and pathological examinations.


METHODS
Total DNA was extracted from leucocytes. Linkage analysis was performed using five RFLP systems from three loci that flank the MEN2A locus (FNRB, RBP3, D10S15). RET proto-oncogene analysis was carried out by automatic DNA sequencing and adequate digestion of PCR amplified products for exons 10 and 11. Screening for medullary thyroid carcinoma or C-cell hyperplasia was performed by the pentagastrin provocation test. Adrenal medullary function was assessed by measurements of 24-hour urinary excretion of catecholamines and their metabolites. Serum calcium and phosphate measurements were the initial screen for hyperparathyroidism. Serum PTH was determined only if hyperparathyroidism was suggested by the former determinations.


METHODS
Genetic study was performed in 59 individuals (39 at risk) from seven kindreds of Mediterranean origin with MEN 2A.


RESULTS
Diagnosis by linkage analysis was not possible in 30% of individuals at risk, but RET proto-oncogene analysis identified all these individuals. Mutations of the RET proto-oncogene were detected in exon 10 (codon 618) in one MEN 2A kindred and in exon 11 (codon 634) in the others. The results of direct analysis were concordant with linkage studies in each case. Three individuals from different MEN 2A kindreds, who were subsequently shown not to be gene carriers, had false positive pentagastrin stimulation tests.


CONCLUSIONS
Biochemical tests can be replaced by direct DNA mutation analysis as the first line screening test in order to identify gene carriers of MEN 2A.
Oriola
J
J
Servei d'Hormonologia, Hospital Clinic i Provincial de Barcelona, Spain.
Hernandez
C
C
Simo
R
R
Barcelo
A
A
Casamitjana
R
R
Vilardell
E
E
Rivera-Fillat
F
F
D001483:Base Sequence; D002874:Chromosome Mapping; D004252:DNA Mutational Analysis; D017931:DNA Primers / Q000235:genetics; D029721:Drosophila Proteins; D005260:Female; D006580:Genetic Carrier Screening; D006801:Humans; D008297:Male; D008969:Molecular Sequence Data; D018813:Multiple Endocrine Neoplasia Type 2a / Q000235:genetics*; D012150:Polymorphism, Restriction Fragment Length; D000090063:Proto-Oncogene Mas; D011518:Proto-Oncogene Proteins / Q000235:genetics; D051096:Proto-Oncogene Proteins c-ret; D020794:Receptor Protein-Tyrosine Kinases / Q000235:genetics
D017931:DNA Primers; D029721:Drosophila Proteins; C000715470:MAS1 protein, human; D000090063:Proto-Oncogene Mas; D011518:Proto-Oncogene Proteins; D051096:Proto-Oncogene Proteins c-ret; D020794:Receptor Protein-Tyrosine Kinases; C416649:Ret protein, Drosophila