title: No evidence for GNAS copy number variants in patients with features of Albright's hereditary osteodystrophy and abnormal platelet Gs activity.
abstract: Albright's hereditary osteodystrophy (AHO) is characterized by short stature, round face, calcifications, obesity, brachydactyly and intellectual disability. AHO without hormone resistance is called pseudopseudohypoparathyroidism (PPHP), a rare clinical condition difficult to diagnose with highly variable features. PPHP is caused by paternally inherited loss-of-function mutations in the GNAS. Patients with 2q37 microdeletions or HDAC4 mutations are also defined as having an AHO-like phenotype with normal stimulatory G (Gs) function. We have studied 256 patients with AHO features but no other diagnosis. Their platelet Gs activity was determined via the aggregation-inhibition test showing Gs hypo- or hyperfuncton in 24% and 15% of the patients, respectively. Before initiating with detailed (epi)genetic GNAS studies, we here wanted to excluded copy number variants (CNVs) in GNAS as cause of AHO with a novel large-scale screening technique. Multiplex amplicon quantification (MAQ) for CNVs screening was developed for the 20q13.3 region including GNAS and potential long-range imprinting control elements such as STX16. This is the first large-scale GNAS CNV study in patients with common AHO features but no CNVs were detected. In conclusion, CNVs in the GNAS region are not likely to cause an AHO-like phenotype with or without abnormal platelet Gs activity. Future studies will be undertaken to find out whether these AHO patients with abnormal Gs function are characterized by GNAS coding or methylation defects.
authors.affiliation: Center for Molecular and Vascular Biology, University of Leuven, Leuven, Belgium.
authors.forename: Benedetta
authors.initials: B
authors.lastname: Izzi
authors.forename: Francis
authors.initials: F
authors.lastname: de Zegher
authors.forename: Inge
authors.initials: I
authors.lastname: Francois
authors.forename: Jurgen
authors.initials: J
authors.lastname: del Favero
authors.forename: Dirk
authors.initials: D
authors.lastname: Goossens
authors.forename: Christine
authors.initials: C
authors.lastname: Wittevrongel
authors.forename: Chantal
authors.initials: C
authors.lastname: Thys
authors.forename: Chris
authors.initials: C
authors.lastname: Van Geet
authors.forename: Kathleen
authors.initials: K
authors.lastname: Freson
mesh_terms: D001792:Blood Platelets / Q000473:pathology; D002864:Chromogranins; D002872:Chromosome Deletion; D002890:Chromosomes, Human, Pair 20 / Q000235:genetics; D056915:DNA Copy Number Variations; D044127:Epigenesis, Genetic; D005359:Fibrous Dysplasia, Polyostotic / Q000235:genetics* / Q000473:pathology; D019205:GTP-Binding Protein alpha Subunits, Gs / Q000235:genetics*; D005820:Genetic Testing / Q000379:methods; D006801:Humans; D010641:Phenotype; D010974:Platelet Aggregation; D016133:Polymerase Chain Reaction / Q000379:methods; D011547:Pseudohypoparathyroidism; D051438:Syntaxin 16 / Q000235:genetics
chemical_list: D002864:Chromogranins; C496118:STX16 protein, human; D051438:Syntaxin 16; C406732:GNAS protein, human; D019205:GTP-Binding Protein alpha Subunits, Gs