Research Article RYR1 Sequence Variants in Myopathies: Expression and Functional Studies in Two Families Alberto Zullo 1,2 , Giuseppa Perrotta 1 , Rossana D*Angelo 1 , Lucia Ruggiero 3 , Elvira Gravino 3 , Luigi Del Vecchio 1,4† , Lucio Santoro 3 , Francesco Salvatore 1,4 , and Antonella Carsana 1,4 1 CEINGE-Advanced Biotechnologies, Via Gaetano Salvatore 486, 80145 Naples, Italy 2 Department of Sciences and Technologies, University of Sannio, Via Port’Arsa 11, 82100 Benevento, Italy 3 Department of Neuroscience, Reproductive Sciences and Dentistry, University of Naples Federico II, Via Pansini 5, 80131 Naples, Italy 4 Department of Molecular Medicine and Medical Biotechnologies, University of Naples Federico II, Via Pansini 5, 80131 Naples, Italy † Deceased Correspondence should be addressed to Francesco Salvatore; salvator@unina.it and Antonella Carsana; carsana@unina.it Received 14 December 2018; Accepted 19 March 2019; Published 21 April 2019 Academic Editor: Richard Tucker Copyright © 2019 Alberto Zullo et al. Tis is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Te skeletal muscle ryanodine receptor (RyR1), i.e., the Ca 2+ channel of the sarco/endoplasmic reticulum (S/ER), and the voltage-dependent calcium channel Cav1.1 are the principal channels involved in excitation-contraction coupling in skeletal muscle. RYR1 gene variants are linked to distinct skeletal muscle disorders, including malignant hyperthermia susceptibility and central core disease (CCD), mainly with autosomal dominant inheritance, and autosomal recessive myopathies with a broad phenotypic and histopathological spectrum. Te age at onset of RYR1-related myopathies varies from infancy to adulthood. We report the identifcation of four RYR1 variants in two Italian families: one with myopathy and vari- ants c.4003C>T (p.R1335C) and c.7035C>A (p.S2345R), and another with CCD and variants c.9293G>T (p.S3098I) and c.14771 14772insTAGACAGGGTGTTGCTCTGTTGCCCTTCTT (p.F4924 V4925insRQGVALLPFF). We demonstrate that, in patient-specifc lymphoblastoid cells, the c.4003C>T (p.R1335C) variant is not expressed and the in-frame 30-nucleotide insertion variant is expressed at a low level. Moreover, Ca 2+ release in response to the RyR1 agonist 4-chloro-m-cresol and to thapsigargin showed that the c.7035C>A (p.S2345R) variant causes depletion of S/ER Ca 2+ stores and that the compound heterozygosity for variant c.9293G>T (p.S3098I) and the 30-nucleotide insertion increases RyR1-dependent Ca 2+ release without afecting ER Ca 2+ stores. In conclusion, we detected and functionally characterized disease-causing variants of the RyR1 channel in patient-specifc lymphoblastoid cells. Tis paper is dedicated to the memory and contribution of Luigi Del Vecchio. 1. Introduction Te RYR1 gene (OMIM ∗180901) encodes the skeletal mus- cle ryanodine receptor (RyR1), which is the Ca 2+ release channel of the sarcoplasmic reticulum (SR). RyR1 and the voltage-dependent L-type calcium channel Cav1.1 are the two principal channels involved in excitation-contraction coupling in skeletal muscle and are mechanically coupled. Te activation of Cav1.1 by depolarization induces RyR1 to open and release calcium from the SR; this mechanism is called “depolarization-induced Ca 2+ release.” RyR1 is also regulated by specifc proteins, Ca 2+ , Mg 2+ , and ATP, and by pharmacological ligands. Mutations in the RYR1 gene are linked to several dis- tinct skeletal muscle disorders, i.e., malignant hyperthermia susceptibility (MHS), central core disease (CCD), exer- tional rhabdomyolysis, King Denborough syndrome, late- onset axial myopathy, and congenital “core-rod myopa- thy,” all mainly with an autosomal dominant inheritance, whereas it is linked to subgroups of multiminicore disease Hindawi BioMed Research International Volume 2019, Article ID 7638946, 13 pages https://doi.org/10.1155/2019/7638946