Mutations in the EXT1 and EXT2 genes in hereditary multiple exostoses

Area of Science:

• Genetics
• Oncology
• Skeletal Dysplasias

Background:

• Hereditary Multiple Exostoses (EXT) is an autosomal dominant bone disorder characterized by multiple benign cartilage-capped tumors.
• Patients with EXT face complications from tumor pressure and an elevated risk of developing malignant chondrosarcoma.
• Genetic heterogeneity exists, with identified loci including EXT1, EXT2, and EXT3.

Purpose of the Study:

• To identify disease-causing mutations in the EXT1 and EXT2 genes in families with Hereditary Multiple Exostoses.
• To analyze the nature, frequency, and distribution of all reported EXT1 and EXT2 mutations.
• To investigate the functional consequences of identified mutations and their relation to tumor suppressor activity.

Main Methods:

• Genetic analysis of the EXT1 and EXT2 genes in 26 EXT families from nine countries.
• Review and compilation of all previously reported mutations in EXT1 and EXT2.
• Classification of mutation types (e.g., premature termination, missense) and assessment of their impact on protein function.

Main Results:

• Mutations in EXT1 or EXT2 were identified in 20 out of 26 (77%) analyzed families.
• Twelve novel mutations in EXT1 and EXT2 were discovered.
• The majority of mutations identified in EXT1 and EXT2 result in premature protein termination, indicating a loss-of-function mechanism.

Conclusions:

• Mutations in the EXT1 and EXT2 genes account for the majority of Hereditary Multiple Exostoses cases.
• The predominant loss-of-function mutations support the hypothesis that EXT1 and EXT2 genes function as tumor suppressors.
• Understanding these genetic underpinnings is crucial for managing EXT complications and associated malignancy risks.