PABPN1 gene therapy for oculopharyngeal muscular dystrophy

Abstract

Oculopharyngeal muscular dystrophy (OPMD) is an autosomal dominant, late-onset muscle disorder characterized by ptosis, swallowing difficulties, proximal limb weakness and nuclear aggregates in skeletal muscles. OPMD is caused by a trinucleotide repeat expansion in the PABPN1 gene that results in an N-terminal expanded polyalanine tract in polyA-binding protein nuclear 1 (PABPN1). Here we show that the treatment of a mouse model of OPMD with an adeno-associated virus-based gene therapy combining complete knockdown of endogenous PABPN1 and its replacement by a wild-type PABPN1 substantially reduces the amount of insoluble aggregates, decreases muscle fibrosis, reverts muscle strength to the level of healthy muscles and normalizes the muscle transcriptome. The efficacy of the combined treatment is further confirmed in cells derived from OPMD patients. These results pave the way towards a gene replacement approach for OPMD treatment.

Inhibition of myostatin improves muscle atrophy in oculopharyngeal muscular dystrophy (OPMD)

“…The A17 transgenic mouse over‐expresses bovine expPABPN1 specifically in skeletal muscle, and it is the most commonly used murine model of OPMD. This mouse exhibits loss of body mass, muscle atrophy, decreased muscle strength, transcriptomic dysregulation, and accumulation of insoluble aggregates in myonuclei . Here, we show that treatment of OPMD mice with the murine anti‐myostatin monoclonal antibody RK35, while not affecting accumulation of intranuclear aggregates, prevents loss of body mass, muscle atrophy, and muscle strength and reduces deposition of fibrotic collagen proteins, which are relevant endpoints for a therapy targeting OPMD.…”

“…The specific force (N/cm 2 ) was calculated by dividing P o by TA muscle cross‐sectional area. Overall cross‐sectional area was estimated using previously established protocols …”

“…Transverse sections of the tissue were sectioned at 10 to 12 different intervals at a thickness of 10 μm, along the length of the muscle, allowing the maximal cross‐sectional area to be determined, and the sections mounted on coated slides (VWR International, Leicestershire, UK), and stored at −80°C. Transverse sections of the TA and EDL were air‐dried, fixed, and stained with anti‐PABPN1 (rabbit monoclonal, diluted 1:100, Abcam ab75855, overnight at 4°C), anti‐laminin (rat monoclonal, diluted 1:800, Sigma‐Aldrich L0663, 1 h at room temperature), and anti‐collagen VI (rabbit polyclonal, Abcam ab6588, 1:200, 1 h room temperature) antibodies or with picosirius red using previously established protocols . Slides were stained with DAPI (4′,6‐diamidino‐2‐phenylindole, 1μg/ml) to visualize nuclei, and coverslips were mounted using mounting medium (Vector Labs, California, USA).…”

“…Repeat alanine expansions with 11–18 repeats lead to a mutant expanded PABPN1 protein (expPABPN1), which causes misfolding, and subsequent accumulation of intranuclear aggregates in muscles . The aggregates sequester wild‐type PABPN1 among other essential components of the cell, thereby dysregulating essential functions of the cell . Interestingly, it has been shown that PABPN1 expression in muscles declines with age in healthy individuals, with OPMD patients presenting molecular signatures of premature ageing .…”

Not Just Another Aspiration Pneumonia: Oculopharyngeal Muscular Dystrophy

“…The efficacy of this gene therapy was further confirmed in cells derived from OPMD patients. These findings show a promising pathway towards a gene replacement approach for OPMD treatment in future [8].…”