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The Use of Real Time PCR Genotyping to Detect Activating GNAS Mutations in McCune-Albright Syndrome

Mariani BMP, Trarbach EB, Toledo RA, Lerario AM, Latronico AC, Mendonca BB and Fragoso MCBV

Introduction: The McCune-Albright syndrome (MAS) is a genetic disease clinically characterized by the triad: bone fibrous dysplasia café-au-lait skin spots and endocrine hyperfunction, such as precocious puberty. MAS is due to activating mutations of GNAS, the gene encoding Gs alpha and mutations analysis of this gene could increase the definitive diagnosis of MAS and atypical and partial. Objectives: To identify the p.R201H and p. R201C GNAS activating mutations in multiple tissues derived from patients with MAS using real time PCR genotyping. Material and methods: Genomic DNA was isolated from blood from 31 patients (28 females) with typical and atypical forms of MAS. Skin, adrenal gland or bone tissue samples were also available from six different patients. Genotyping based on PCR real time assay using TaqMan probes was performed for identification of p.R201H and p. R201C GNAS mutations. Cloning and sequencing were used as assenting techniques. Results: Using real time PCR genotyping, no mutations in GNAS were identified in blood samples of MAS patients, only in bone sample of a patient with a previously identified p.R201H. Cloning and sequencing from blood of this same patient revealed that 5/150 clones harboring the p. R201H. Conclusion: The real time PCR genotyping proved to be efficient for the molecular diagnosis of MAS in affected patient's tissues. Advantages of this technique are rapidity, accuracy, it is generally easy to perform and could be used routinely. Nevertheless, optimization of GNAS detection mutation is still necessary to considerer this technique to earlier diagnosis of non-classical forms of MAS using peripheral blood.