Mutations in FLNC for a long time are known in connection to neuromuscular disorders and only recently were described in association with various cardiomyopathies. Here, we report a new clinical phenotype of filaminopathy in four unrelated patients with early-onset restrictive cardiomyopathy (RCM) in combination with congenital myopathy due to FLNC mutations (NM_001458.4:c.3557C>T, p.A1186V, rs1114167361 in three probands and c.[3547G>C; 3548C>T], p.A1183L, rs1131692185 in one proband). In all cases, concurrent myopathy was confirmed by neurological examination, electromyography, and morphological studies. Three of the patients also presented with arthrogryposis. The pathogenicity of the described missense variants was verified by cellular and morphological studies and by in vivo modeling in zebrafish. Combination of in silico and experimental approaches revealed that FLNC missense variants localized in Ig-loop segments often lead to development of RCM. The described FLNC mutations associated with early-onset RCMP extend cardiac spectrum of filaminopathies and facilitate the differential diagnosis of restrictive cardiac phenotype associated with neuromuscular involvement in children.

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AlphoidtetO-type human artificial chromosome (HAC) has been recently synthetized as a novel class of gene delivery vectors for induced pluripotent stem cell (iPSC)-based tissue replacement therapeutic approach. This HAC vector was designed to deliver copies of genes into patients with genetic diseases caused by the loss of a particular gene function. The alphoidtetO-HAC vector has been successfully transferred into murine embryonic stem cells (ESCs) and maintained stably as an independent chromosome during the proliferation and differentiation of these cells. Human ESCs and iPSCs have significant differences in culturing conditions and pluripotency state in comparison with the murine naïve-type ESCs and iPSCs. To date, transferring alphoidtetO-HAC vector into human iPSCs (hiPSCs) remains a challenging task. In this study, we performed the microcell-mediated chromosome transfer (MMCT) of alphoidtetO-HAC expressing the green fluorescent protein into newly generated hiPSCs. We used a recently modified MMCT method that employs an envelope protein of amphotropic murine leukemia virus as a targeting cell fusion agent. Our data provide evidence that a totally artificial vector, alphoidtetO-HAC, can be transferred and maintained in human iPSCs as an independent autonomous chromosome without affecting pluripotent properties of the cells. These data also open new perspectives for implementing alphoidtetO-HAC as a gene therapy tool in future biomedical applications.

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Even though genetic studies of individuals with neuromuscular diseases have uncovered the molecular background of many cardiac disorders such as cardiomyopathies and inherited arrhythmic syndromes, the genetic cause of a proportion of cardiomyopathies associated with neuromuscular phenotype still remains unknown. Here, we present an individual with a combination of cardiomyopathy and limb-girdle type muscular dystrophy where whole exome sequencing identified myoferlin ( MYOF )—a member of the Ferlin protein family and close homolog of DYSF —as the most likely candidate gene. The disease-causative role of the identified variant c.[2576delG; 2575G>C], p.G859QfsTer8 is supported by functional studies in vitro using the primary patient’s skeletal muscle mesenchymal progenitor cells, including both RNA sequencing and morphological studies, as well as recapitulating the muscle phenotype in vivo in zebrafish. We provide the first evidence supporting a role of MYOF in human muscle disease.