Abstract
IntroductionMutations of the PRRT2 gene are the most common cause for paroxysmal kinesigenic dyskinesia. However, patients with negative PRRT2 mutations are not rare. The aim of this study is to determine whether copy number variant of PRRT2 gene is another potential pathogenic mechanism in the patients with paroxysmal kinesigenic dyskinesia with negative PRRT2 point and frameshift mutations.MethodsWe screened PRRT2 copy number variants using the AccuCopy™ method in 29 patients with paroxysmal kinesigenic dyskinesia with negative PRRT2 point and frameshift mutations. Next‐generation sequencing was used to determine the chromosomal deletion sites in patients with PRRT2 copy number variants, and to exclude mutations in other known causative genes for paroxysmal kinesigenic dyskinesia.ResultsTwo sporadic patients with negative PRRT2 point and frameshift mutations (6.9%) were identified to have de novo PRRT2 copy number deletions (591 and 832 Kb deletions located in 16p11.2). The two patients presented with pure paroxysmal kinesigenic dyskinesia and paroxysmal kinesigenic dyskinesia and benign infantile convulsions, respectively. They had normal intelligence and neuropsychiatric development, in contrast to those previously reported with 16p11.2 deletions complicated with neuropsychiatric disorders. No correlation between the deletion ranges and phenotypic variations was found.Conclusion16p11.2 deletions play causative roles in paroxysmal kinesigenic dyskinesia, especially for sporadic cases. Our findings extend the phenotype of 16p11.2 deletions to pure paroxysmal kinesigenic dyskinesia. Screening for 16p11.2 deletions should thus be included in genetic evaluations for patients with paroxysmal kinesigenic dyskinesia.
Highlights
Mutations of the PRRT2 gene are the most common cause for paroxys‐ mal kinesigenic dyskinesia
Paroxysmal kinesigenic dyskinesia (PKD) is an autosomal dominant inheritance disorder characterized by paroxysmal involuntary dys‐ tonic, choreoathetoid, and ballistic attacks triggered by sudden movements (Jankovic & Demirkiran, 2002)
Since the majority of PRRT2 mutations are truncating mu‐ tations that lead to loss of function or haploinsufficiency of PRRT2, copy number deletions of this gene are suspected to cause PKD
Summary
Mutations of the PRRT2 gene are the most common cause for paroxys‐ mal kinesigenic dyskinesia. The aim of this study is to determine whether copy number variant of PRRT2 gene is another potential pathogenic mechanism in the patients with paroxysmal ki‐ nesigenic dyskinesia with negative PRRT2 point and frameshift mutations. Paroxysmal kinesigenic dyskinesia (PKD) is an autosomal dominant inheritance disorder characterized by paroxysmal involuntary dys‐ tonic, choreoathetoid, and ballistic attacks triggered by sudden movements (Jankovic & Demirkiran, 2002) It has been demon‐ strated to be associated with mutations in several genes, includ‐ ing PRRT2 (proline‐rich region transmembrane protein‐2) (Chen et al, 2011), SLC2A1 (solute carrier family 2, member 1), MR‐1 (myo‐ fibrillogenesis regulator 1), CLCN1 (chloride voltage‐gated channel 1) (Wang, Li, Liu, Wen, & Wu, 2016), SCN8A (sodium voltage‐gated channel alpha subunit 8) (Chen et al, 2015), and ADCY5 (adenylyl cyclase 5) (Gardella et al, 2016). Since the majority of PRRT2 mutations are truncating mu‐ tations that lead to loss of function or haploinsufficiency of PRRT2, copy number deletions of this gene are suspected to cause PKD
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