Abstract
McCune–Albright syndrome (MAS) is a rare congenital disorder characterized by the association of endocrine and nonendocrine anomalies caused by somatic activating variants of GNAS. The mosaic state of variants makes the clinical presentation extremely heterogeneous depending on involved tissues. Biological samples bearing a low level of mosaicism frequently lead to false-negative results with an underestimation of causative molecular alterations, and the analysis of biopsies is often needed to obtain a molecular diagnosis. To date, no reliable analytical method for the noninvasive testing of blood is available. This study was aimed at validating a novel and highly sensitive technique, the digital PCR (dPCR), to increase the detection rate of GNAS alterations in patients with a clinical suspicion of MAS and, in particular, in blood. We screened different tissues (blood, bone, cutis, ovary, and ovarian cyst) collected from 54 MAS patients by different technical approaches. Considering blood, Sanger was unable to detect mutations, the allele-specific PCR and the co-amplification at lower denaturation temperature had a 9.1% and 18.1% detection rate, respectively, whereas the dPCR reached a 37.8% detection rate. In conclusion, the dPCR resulted in a cost-effective, reliable, and rapid method allowing the selective amplification of low-frequency variants and able to improve GNAS mutant allele detection, especially in the blood.
Highlights
The McCune–Albright syndrome (MAS, MIM #174800) is a rare congenital disorder that comprises the clinical triad of endocrinopathies, cafè-au-lait pigmented skin lesions (SP), and fibrous dysplasia of bone (FD)
For 41 patients, a single tissue only was available for the analysis [24 blood samples (BL) and 17 biopsies: 10 bone (BO), 4 cutis (CB), 3 ovarian tissue (OT), and/or ovarian cyst (OC)], whereas for 13 patients, we investigated and compared the DNA extracted from different tissues (2 BL+BO, 6 BL+CB/ fibroblasts from cutaneous biopsy, and 4 BL+OT/OC)
The bulk of experiments performed allowed to obtain a molecular diagnosis in MAS/FD subjects that were still missing because of the low detection rate of the Sanger sequencing, thanks to the setup of the digital PCR (dPCR), a highly sensitive and specific technique to detect low-abundance somatic single-nucleotide GNAS alterations
Summary
The McCune–Albright syndrome (MAS, MIM #174800) is a rare congenital disorder that comprises the clinical triad of endocrinopathies, cafè-au-lait pigmented skin lesions (SP), and fibrous dysplasia of bone (FD). The disease demonstrated sporadic occurrence, phenotypic heterogeneity, variable involvement of different endocrine glands, and a pattern of skin and bone lesions following the lines of the embryologic development, it was proposed that MAS derived from a postzygotic genetic defect, leading to a mosaic distribution of mutated cells. Such hypothesis was confirmed by the identification of somatic activating variants affecting the alpha subunit of the stimulatory G protein (Gsα, encoded by GNAS, MIM*139320) (Landis et al, 1989; Weinstein et al, 1991; Schwindinger et al, 1992; Candeliere et al, 1997). The tissue-by-tissue study by droplet digital PCR (ddPCR) of autopsy samples from a patient confirmed that MAS can affect a wider range of tissues, leading to extraskeletal manifestations, such as gastrointestinal reflux and/or polyps, pancreatitis, hepatobiliary disease, cardiac disease (sudden death, tachycardia, high output heart failure, and aortic root dilatation), platelet dysfunction, and cancer (bone, breast, testes, and thyroid) (Salpea and Stratakis, 2014; Vasilev et al, 2014)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
