POPDC3 Gene Variants Associate with a New Form of Limb Girdle Muscular Dystrophy

• Published in: Annals of neurology 2019-12, Vol.86 (6), p.832-843
• Main Authors: Vissing, John, Johnson, Katherine, Töpf, Ana, Nafissi, Shahriar, Díaz‐Manera, Jordi, French, Vanessa M., Schindler, Roland F., Sarathchandra, Padmini, Løkken, Nicoline, Rinné, Susanne, Freund, Max, Decher, Niels, Müller, Thomas, Duno, Morten, Krag, Thomas, Brand, Thomas, Straub, Volker
• Format: Article
• Language: English
• Subjects: Adenosine monophosphate; Adult; Animals; Biopsy; Cell Adhesion Molecules - chemistry; Cell Adhesion Molecules - genetics; Cohort Studies; Creatine; Creatine kinase; Cyclic AMP; Danio rerio; Domains; Dystrophy; Female; Gametocytes; Gastric cancer; Gene Knockdown Techniques - methods; Genetic Variation - genetics; Humans; Kinases; Larvae; Magnetic resonance imaging; Male; Membrane proteins; Middle Aged; Muscle Proteins - chemistry; Muscle Proteins - genetics; Muscle, Skeletal - diagnostic imaging; Muscle, Skeletal - physiology; Muscles; Muscular Dystrophies, Limb-Girdle - diagnostic imaging; Muscular Dystrophies, Limb-Girdle - genetics; Muscular dystrophy; Mutants; NMR; Nuclear magnetic resonance; Oocytes; Pedigree; Potassium; Protein Structure, Secondary; Proteins; Serum levels; Skeletal muscle; Xenopus laevis; Zebrafish
• ISSN: 0364-5134; 1531-8249
• DOI: 10.1002/ana.25620

Objective The Popeye domain containing 3 (POPDC3) gene encodes a membrane protein involved in cyclic adenosine monophosphate (cAMP) signaling. Besides gastric cancer, no disease association has been described. We describe a new muscular dystrophy associated with this gene. Methods We screened 1,500 patients with unclassified limb girdle weakness or hyperCKemia for pathogenic POPDC3 variants. Five patients carrying POPDC3 variants were examined by muscle magnetic resonance imaging (MRI), muscle biopsy, and cardiac examination. We performed functional analyses in a zebrafish popdc3 knockdown model and heterologous expression of the mutant proteins in Xenopus laevis oocytes to measure TREK‐1 current. Results We identified homozygous POPDC3 missense variants (p.Leu155His, p.Leu217Phe, and p.Arg261Gln) in 5 patients from 3 ethnically distinct families. Variants affected highly conserved residues in the Popeye (p.Leu155 and p.Leu217) and carboxy‐terminal (p.Arg261) domains. The variants were almost absent from control populations. Probands’ muscle biopsies were dystrophic, and serum creatine kinase levels were 1,050 to 9,200U/l. Muscle weakness was proximal with adulthood onset in most patients and affected lower earlier than upper limbs. Muscle MRI revealed fat replacement of paraspinal and proximal leg muscles; cardiac investigations were unremarkable. Knockdown of popdc3 in zebrafish, using 2 different splice‐site blocking morpholinos, resulted in larvae with tail curling and dystrophic muscle features. All 3 mutants cloned in Xenopus oocytes caused an aberrant modulation of the mechano‐gated potassium channel, TREK‐1. Interpretation Our findings point to an important role of POPDC3 for skeletal muscle function and suggest that pathogenic variants in POPDC3 are responsible for a novel type of autosomal recessive limb girdle muscular dystrophy. ANN NEUROL 2019;86:832–843