POPDC1S201F causes muscular dystrophy and arrhythmia by affecting protein trafficking
Roland F.R. Schindler, … , Thomas Brand, Alessandra Ferlini
Roland F.R. Schindler, … , Thomas Brand, Alessandra Ferlini
Published December 7, 2015
Citation Information: J Clin Invest. 2016;126(1):239-253. https://doi.org/10.1172/JCI79562.
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Research Article Muscle biology

POPDC1S201F causes muscular dystrophy and arrhythmia by affecting protein trafficking

Abstract

The Popeye domain–containing 1 (POPDC1) gene encodes a plasma membrane–localized cAMP-binding protein that is abundantly expressed in striated muscle. In animal models, POPDC1 is an essential regulator of structure and function of cardiac and skeletal muscle; however, POPDC1 mutations have not been associated with human cardiac and muscular diseases. Here, we have described a homozygous missense variant (c.602C>T, p.S201F) in POPDC1, identified by whole-exome sequencing, in a family of 4 with cardiac arrhythmia and limb-girdle muscular dystrophy (LGMD). This allele was absent in known databases and segregated with the pathological phenotype in this family. We did not find the allele in a further screen of 104 patients with a similar phenotype, suggesting this mutation to be family specific. Compared with WT protein, POPDC1S201F displayed a 50% reduction in cAMP affinity, and in skeletal muscle from patients, both POPDC1S201F and WT POPDC2 displayed impaired membrane trafficking. Forced expression of POPDC1S201F in a murine cardiac muscle cell line (HL-1) increased hyperpolarization and upstroke velocity of the action potential. In zebrafish, expression of the homologous mutation (popdc1S191F) caused heart and skeletal muscle phenotypes that resembled those observed in patients. Our study therefore identifies POPDC1 as a disease gene causing a very rare autosomal recessive cardiac arrhythmia and LGMD, expanding the genetic causes of this heterogeneous group of inherited rare diseases.

Authors

Roland F.R. Schindler, Chiara Scotton, Jianguo Zhang, Chiara Passarelli, Beatriz Ortiz-Bonnin, Subreena Simrick, Thorsten Schwerte, Kar-Lai Poon, Mingyan Fang, Susanne Rinné, Alexander Froese, Viacheslav O. Nikolaev, Christiane Grunert, Thomas Müller, Giorgio Tasca, Padmini Sarathchandra, Fabrizio Drago, Bruno Dallapiccola, Claudio Rapezzi, Eloisa Arbustini, Francesca Romana Di Raimo, Marcella Neri, Rita Selvatici, Francesca Gualandi, Fabiana Fattori, Antonello Pietrangelo, Wenyan Li, Hui Jiang, Xun Xu, Enrico Bertini, Niels Decher, Jun Wang, Thomas Brand, Alessandra Ferlini

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Figure 4

The POPDC1S201F mutant protein displays a reduced cAMP affinity.

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The POPDC1S201F mutant protein displays a reduced cAMP affinity. (A) cAM...
(A) cAMP affinity precipitation of WT or POPDC1S201F protein. Left panel: precipitated proteins, unbound fraction, and input samples as well as protein subjected to control precipitation using ethanolamine-agarose (agarose) were subjected to Western blot detection of POPDC1. Right panel: quantification of cAMP affinity, calculating the ratios between input and cAMP agarose–bound protein fractions. (B) Left: example of a FRET measurement of 293A cells transfected with YFP–TREK-1 together with POPDC1-CFP or POPDC1S201F-CFP. Right: relative change in FRET signal as a measure of cAMP affinity. (C) Chemiluminescence assay in Xenopus oocytes analyzing the surface expression of extracellularly HA-tagged TREK-1 in the absence or presence of POPDC1 or POPDC1S201F. Control, noninjected oocytes. Measurements after incubation with 0.5 mM theophylline are illustrated with white bars. (D) Representative 2-electrode voltage clamp measurements in oocytes injected with TREK-1 alone (black) or coinjected with Popdc1 (gray) or POPDC1S201F (red). Voltage was ramped from –110 to +35 mV. (E) Relative current amplitudes at 0 mV. (F) 2-Electrode voltage clamp measurements in oocytes injected with TREK-1 or coinjected with POPDC1 or POPDC1S201F bathed after cRNA injection in a storage solution containing 1 mM 8-Br-cAMP. (G) Relative current amplitudes of TREK-1 coinjected with POPDC1, measured in recording solution or directly after 10 minutes of perfusion with 2 mM 8-Br-cAMP. (A–C and E–G) Numbers of experiments are included in the bars. Results are presented as mean ± SEM. Two groups of measurements in A were compared by paired 2-tailed Student’s t test. One-way ANOVA was used for the data presented in B, C, and E–G. *P < 0.05; ***P < 0.001.