title: Synonymous Mutations Add a Layer of Complexity in the Diagnosis of Human Osteopetrosis.
abstract: Autosomal recessive osteopetroses (AROs) are rare, genetically heterogeneous skeletal diseases with increased bone density that are often lethal if left untreated. A precise molecular classification is relevant for the patient's management, because in some subgroups hematopoietic stem cell transplantation (HSCT), which is the only curative therapy, is contraindicated. In two unrelated ARO patients, the molecular analysis revealed the presence of a synonymous variant in known ARO genes, namely in the TCIRG1 gene in one patient and in the CLCN7 in the other patient, predicted to impact on the splicing process. In the latter case, sequencing of the transcript confirmed the splicing defect, whereas in the former, for whom an RNA sample was not available, the defect was reconstructed in vitro by the minigene technology. These results strongly suggest that these synonymous changes were responsible for the disease in our patients. Our findings are novel with respect to ARO and add to the few reports in literature dealing with different diseases, underlining the importance of cDNA analysis for the correct assessment of exonic changes, even when exome sequencing is performed. In particular, we highlight the possibility that at least in some cases ARO is due to synonymous changes, erroneously considered clinically silent, in the genes already described in literature, and suggest carefully reevaluating the sequencing results of these genes when mutations are not found at a first analysis. In addition, with respect to the CLCN7 gene, we suggest that synonymous variants might also contribute to the large spectrum of severity typical of CLCN7-dependent osteopetrosis through more subtle, but not negligible, effects on protein availability and functionality. © 2016 American Society for Bone and Mineral Research.
authors.affiliation: Humanitas Clinical and Research Institute, Rozzano, Italy.|Department of Medical Biotechnologies and Translational Medicine, University of Milan, Milan, Italy.
authors.forename: Eleonora
authors.initials: E
authors.lastname: Palagano
authors.affiliation: Humanitas Clinical and Research Institute, Rozzano, Italy.|National Research Council-Institute of Genetics and Biomedical Research (CNR-IRGB), Milan Unit, Milan, Italy.
authors.forename: Lucia
authors.initials: L
authors.lastname: Susani
authors.affiliation: Humanitas Clinical and Research Institute, Rozzano, Italy.|National Research Council-Institute of Genetics and Biomedical Research (CNR-IRGB), Milan Unit, Milan, Italy.
authors.forename: Ciro
authors.initials: C
authors.lastname: Menale
authors.affiliation: Department of Public Health and Pediatric Sciences, University of Turin, Turin, Italy.
authors.forename: Ugo
authors.initials: U
authors.lastname: Ramenghi
authors.affiliation: Pediatric Onco-Hematology and Stem Cell Transplant Division, Regina Margherita Children Hospital, City of Health and Science, Turin, Italy.
authors.forename: Massimo
authors.initials: M
authors.lastname: Berger
authors.affiliation: CRS4, Science and Technology Park Polaris, Pula, Italy.
authors.forename: Paolo
authors.initials: P
authors.lastname: Uva
authors.affiliation: CRS4, Science and Technology Park Polaris, Pula, Italy.|Department of Biomedical Sciences, University of Sassari, Sassari, Italy.
authors.forename: Manuela
authors.initials: M
authors.lastname: Oppo
authors.affiliation: Humanitas Clinical and Research Institute, Rozzano, Italy.|National Research Council-Institute of Genetics and Biomedical Research (CNR-IRGB), Milan Unit, Milan, Italy.
authors.forename: Paolo
authors.initials: P
authors.lastname: Vezzoni
authors.affiliation: Humanitas Clinical and Research Institute, Rozzano, Italy.|National Research Council-Institute of Genetics and Biomedical Research (CNR-IRGB), Milan Unit, Milan, Italy.
authors.forename: Anna
authors.initials: A
authors.lastname: Villa
authors.affiliation: Humanitas Clinical and Research Institute, Rozzano, Italy.|National Research Council-Institute of Genetics and Biomedical Research (CNR-IRGB), Milan Unit, Milan, Italy.
authors.forename: Cristina
authors.initials: C
authors.lastname: Sobacchi
mesh_terms: D000595:Amino Acid Sequence; D001483:Base Sequence; D018118:Chloride Channels / Q000235:genetics; D017809:Fatal Outcome; D005260:Female; D006801:Humans; D007223:Infant; D008297:Male; D010022:Osteopetrosis / Q000175:diagnosis* / Q000000981:diagnostic imaging / Q000235:genetics*; D011247:Pregnancy; D016415:Sequence Alignment; D000069456:Silent Mutation / Q000235:genetics*; D025262:Vacuolar Proton-Translocating ATPases / Q000737:chemistry / Q000235:genetics
chemical_list: C097540:CLCN7 protein, human; D018118:Chloride Channels; C472421:TCIRG1 protein, human; D025262:Vacuolar Proton-Translocating ATPases
keywords: CLCN7; MINIGENE; OSTEOPETROSIS; SYNONYMOUS MUTATION; TCIRG1