CGG expansion in NOTCH2NLC is associated with oculopharyngodistal myopathy with neurological manifestations

Abstract

Oculopharyngodistal myopathy (OPDM) is a rare hereditary muscle disease characterized by progressive distal limb weakness, ptosis, ophthalmoplegia, bulbar muscle weakness and rimmed vacuoles on muscle biopsy. Recently, CGG repeat expansions in the noncoding regions of two genes, LRP12 and GIPC1, have been reported to be causative for OPDM. Furthermore, neuronal intranuclear inclusion disease (NIID) has been recently reported to be caused by CGG repeat expansions in NOTCH2NLC. We aimed to identify and to clinicopathologically characterize patients with OPDM who have CGG repeat expansions in NOTCH2NLC (OPDM_NOTCH2NLC). Note that 211 patients from 201 families, who were clinically or clinicopathologically diagnosed with OPDM or oculopharyngeal muscular dystrophy, were screened for CGG expansions in NOTCH2NLC by repeat primed-PCR. Clinical information and muscle pathology slides of identified patients with OPDM_NOTCH2NLC were re-reviewed. Intra-myonuclear inclusions were evaluated using immunohistochemistry and electron microscopy (EM). Seven Japanese OPDM patients had CGG repeat expansions in NOTCH2NLC. All seven patients clinically demonstrated ptosis, ophthalmoplegia, dysarthria and muscle weakness; they myopathologically had intra-myonuclear inclusions stained with anti-poly-ubiquitinated proteins, anti-SUMO1 and anti-p62 antibodies, which were diagnostic of NIID (typically on skin biopsy), in addition to rimmed vacuoles. The sample for EM was available only from one patient, which demonstrated intranuclear inclusions of 12.6 ± 1.6 nm in diameter. We identified seven patients with OPDM_NOTCH2NLC. Our patients had various additional central and/or peripheral nervous system involvement, although all were clinicopathologically compatible; thus, they were diagnosed as having OPDM and expanding a phenotype of the neuromyodegenerative disease caused by CGG repeat expansions in NOTCH2NLC.

Keywords: CGG repeat expansion; NOTCH2NLC; Neuronal intranuclear inclusion disease; Oculopharyngeal muscular dystrophy; Oculopharyngodistal myopathy.

Fig. 1

Clinical information of patients with CGG expansion in NOTCH2NLC. a Family trees of seven families. White circles and squares show unaffected indivisuals. Black circles and squares show patients. * shows probands. b Repeat primed PCR and fragment analysis for patient 1 and control. c Southern blotting analysis for CGG expansion in NOTCH2NLC. The arrows and arrowheads indicate the expanded alleles in patients 2 and 3, respectively. M, DNA marker. d Imaging of muscle CT from patient 2 shows asymmetric muscle atrophy. Right gluteus maximus, left vastus lateralis, adductor magnus, and rectus femoris are severely affected. e DWI of patient 1. f FLAIR image of patient 1. g DWI of patient 5. h FLAIR image of patient 5. i Marked fiber size variation, moderate endomysial fibrosis, and fibers with internal nuclei are seen on H&E. j Rimmed vacuole is present in a muscle fiber on mGT. k Some myofibers express neonatal myosin heavy chain. i–k Scale bars denote 50 µm

Fig. 2

Pathology, revealed by electron microscopy and disease spectrum. Anti-poly-ubiquitinated protein antibody (a), anti-caveolin-3 antibody (b, f, j), DAPI (c, g, k), anti-SUMO-1 antibody (e), and anti-p62 (i) are stained. d, h, l show merged immunohistochemistry. a–l Scale bars denote 10 µm. On EM, a longitudinal section shows tubulofilamentous inclusions within the myonuclei together with markedly disorganized myofibrils (arrow) in the surrounding area (m, n). m Scale bar denotes 5 µm. n Scale bar shows 500 nm. o, q HE, p, r p62 are stained on serial sections of the skin sample in patient 1. Intranuclear inclusions with p62-positive in sweat gland cells (p) and adipocytes (r) are seen. o–r Scale bars denote 20 µm. s Disease spectrum caused by CGG expansion in NOTCH2NLC