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Oculopharyngodistal myopathy (OPDM) is an adult-onset neuromuscular disease characterized by progressive ocular, facial, pharyngeal and distal limb muscle involvement. Trinucleotide repeat expansions in LRP12 or GIPC1 were recently reported to be associated with OPDM. However, a significant portion of OPDM patients have unknown genetic causes. In this study long-read whole-genome sequencing and repeat-primed polymerase chain reaction were performed and we identified GGC repeat expansions in the NOTCH2NLC gene in 16.7% (4/24) of a cohort of Chinese OPDM patients, designated as OPDM type 3 (OPDM3). Methylation analysis indicated that methylation levels of the NOTCH2NLC gene were unaltered in OPDM3 patients, but increased significantly in asymptomatic carriers. Quantitative real-time PCR analysis indicated that NOTCH2NLC mRNA levels were increased in muscle but not in blood of OPDM3 patients. Immunofluorescence on OPDM muscle samples and expressing mutant NOTCH2NLC with (GGC)69 repeat expansions in HEK293 cells indicated that mutant NOTCH2NLC-polyGlycine protein might be a major component of intranuclear inclusions, and contribute to toxicity in cultured cells. In addition, two RNA-binding proteins, hnRNP A/B and MBNL1, were both co-localized with p62 in intranuclear inclusions in OPDM muscle samples. These results indicated that a toxic protein gain-of-function mechanism and RNA gain-of-function mechanism may both play a vital role in the pathogenic processes of OPDM3. This study extended the spectrum of NOTCH2NLC repeat expansion related diseases to a predominant myopathy phenotype presenting as OPDM, and provided evidence for possible pathogenesis of these diseases.

Background Erythrocytes are a major source of peripheral α-synuclein (α-Syn). The goal of the current investigation is to evaluate erythrocytic total, oligomeric/aggregated, and phosphorylated α-Syn species as biomarkers of Parkinson’s disease (PD). PD and healthy control blood samples were collected along with extensive clinical history to determine whether total, phosphorylated, or aggregated α-Syn derived from erythrocytes (the major source of blood α-Syn) are more promising and consistent biomarkers for PD than are free α-Syn species in serum or plasma. Methods Using newly developed electrochemiluminescence assays, concentrations of erythrocytic total, aggregated and phosphorylated at Ser129 (pS129) α-Syn, separated into membrane and cytosolic components, were measured in 225 PD patients and 133 healthy controls and analyzed with extensive clinical measures. Results The total and aggregated α-Syn levels were significantly higher in the membrane fraction of PD patients compared to healthy controls, but without alterations in the cytosolic component. The pS129 level was remarkably higher in PD subjects than in controls in the cytosolic fraction, and to a lesser extent, higher in the membrane fraction. Combining age, erythrocytic membrane aggregated α-Syn, and cytosolic pS129 levels, a model generated by using logistic regression analysis was able to discriminate patients with PD from neurologically normal controls, with a sensitivity and a specificity of 72 and 68%, respectively. Conclusions These results suggest that total, aggregated and phosphorylated α-Syn levels are altered in PD erythrocytes and peripheral erythrocytic α-Syn is a potential PD biomarker that needs further validation. Electronic supplementary material The online version of this article (10.1186/s40035-019-0155-y) contains supplementary material, which is available to authorized users.

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