Paroxysmal kinesigenic dyskinesias is a paroxysmal movement disorder characterized by recurrent, brief attacks of abnormal involuntary movements induced by sudden voluntary movements. Although several loci, including the pericentromeric region of chromosome 16, have been linked to paroxysmal kinesigenic dyskinesias, the causative gene has not yet been identified. Here, we identified proline-rich transmembrane protein 2 (PRRT2) as a causative gene of paroxysmal kinesigenic dyskinesias by using a combination of exome sequencing and linkage analysis. Genetic linkage mapping with 11 markers that encompassed the pericentromeric of chromosome 16 was performed in 27 members of two families with autosomal dominant paroxysmal kinesigenic dyskinesias. Then, the whole-exome sequencing was performed in three patients from these two families. By combining the defined linkage region (16p12.1–q12.1) and the results of exome sequencing, we identified an insertion mutation c.649_650InsC (p.P217fsX7) in one family and a nonsense mutation c.487C>T (p.Q163X) in another family. To confirm our findings, we sequenced the exons and flanking introns of PRRT2 in another three families with paroxysmal kinesigenic dyskinesias. The c.649_650InsC (p.P217fsX7) mutation was identified in two of these families, whereas a missense mutation, c.796C>T (R266W), was identified in another family with paroxysmal kinesigenic dyskinesias. All of these mutations completely co-segregated with the phenotype in each family. None of these mutations was identified in 500 normal unaffected individuals of matched geographical ancestry. Thus, we have identified PRRT2 as the first causative gene of paroxysmal kinesigenic dyskinesias, warranting further investigations to understand the pathogenesis of this disorder.

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 PCR 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.

Colony-stimulating factor 1 receptor ( CSF1R ) is primarily expressed in microglia. Its monoallelic mutation causes CSF1R-associated microgliopathy (CAMP), a major form of adult-onset leukoencephalopathy with axonal spheroids and pigmented glia (ALSP) and a fatal neurological disease without clinical cure. We developed mouse models harboring human hotspot mutations of CAMP and replaced CSF1R-deficient microglia with CSF1R-normal cells through microglia replacement by bone marrow transplantation (Mr BMT), which attenuated pathology in mice. We further demonstrated that, in the context of CSF1R deficiency, traditional bone marrow transplantation (tBMT) in ALSP functions similarly to Mr BMT, efficiently replacing microglia and reducing disease progression. We then replaced CSF1R-deficient microglia in eight patients by tBMT. The disease progression was halted during the 24-month follow-up. Together, microglia replacement corrects pathogenic mutations and halts disease progression in mice and humans.

Objective: We aimed to investigate the clinical and genetic features of paroxysmal kinesigenic dyskinesia (PKD) in a large population and to analyze the genotype–phenotype correlation of PKD. Methods: We analyzed clinical manifestations and conducted PRRT2 screening in 110 patients with PKD. Clinical data were compared between 91 probands with and without PRRT2 mutations. Results: Among the enrolled participants (45 from 26 families, 65 sporadic cases), 8 PRRT2 mutations were detected in 20 PKD families (76.9%) and 14 sporadic cases (21.5%), accounting for 37.4% (34/91) of the study population. Five mutations (c.649dupC, c.649delC, c.487C>T, c.573dupT, c.796C>T) were already reported, while 3 mutations (c.787C>T, c.797G>A, c.931C>T) were undocumented. A patient harboring a homozygous c.931C>T mutation was shown to have inherited the mutation via uniparental disomy. Compared with non-PRRT2 mutation carriers, the PRRT2 mutation carriers were younger at onset, experienced longer attacks, and tended to present with complicated PKD, combined phenotypes of dystonia and chorea, and a positive family history. A good response was shown in 98.4% of the patients prescribed with carbamazepine. Conclusions: PRRT2 mutations are common in patients with PKD and are significantly associated with an earlier age at onset, longer duration of attacks, a complicated form of PKD, combined phenotypes of dystonia and chorea, and a tendency for a family history of PKD. A patient with uniparental disomy resulting in a homozygous c.931C>T mutation is identified in the present study. Carbamazepine is the first-choice drug for patients with PKD, but an individualized treatment regimen should be developed.