[Detection of a non-standard mutation in the ret protoncogene by site directed mutagenesis]

Area of Science:

• Genetics
• Oncology
• Endocrinology

Background:

• Multiple Endocrine Neoplasia type 2A (MEN2A) is an autosomal dominant disorder associated with medullary thyroid cancer, pheochromocytoma, and parathyroid hyperplasia.
• Mutations in the ret proto-oncogene are the primary cause of MEN2A, exhibiting nearly complete penetrance.
• Codon 634 in the ret gene is a known hot-spot mutation site, implicated in 85% of MEN2A families.

Purpose of the Study:

• To develop and implement a cost-effective, family-specific genetic diagnostic strategy for MEN2A.
• To enable presymptomatic diagnosis and intervention in a family with a suspected MEN2A mutation.
• To confirm a novel ret proto-oncogene mutation site in a MEN2A-affected family.

Main Methods:

• Initial application of a previously developed indirect PCR-based strategy targeting the codon 634 hot-spot.
• Sequencing of exons 10 and 11 of the ret proto-oncogene to identify the specific mutation.
• Development of a new, cost-effective family-specific strategy using mutagenic PCR and enzymatic digestion for diagnosis.

Main Results:

• The index patient's DNA showed no mutation at the codon 634 hot-spot.
• Sequencing revealed a novel mutation in codon 611 of the ret proto-oncogene within the family.
• The newly developed family-specific strategy successfully diagnosed all family members.
• A seven-year-old boy with the identified mutation underwent a preventive thyroidectomy.

Conclusions:

• A combined approach of indirect testing for known hot-spots and family-specific mutation detection is effective for MEN2A diagnosis.
• Presymptomatic diagnosis and intervention, such as thyroidectomy, can be achieved through targeted genetic strategies.
• The developed methods offer a cost-effective alternative to sending samples for genetic analysis abroad, facilitating timely clinical management.