Proline-rich Transmembrane Protein 2 Mutations Research Articles

Proline-rich transmembrane protein 2 knock-in mice present dopamine-dependent motor deficits.

Mutations of proline-rich transmembrane protein 2 (PRRT2) lead to dyskinetic disorders such as paroxysmal kinesigenic dyskinesia (PKD), which is characterized by attacks of involuntary movements precipitated by suddenly initiated motion, and some convulsive disorders. Although previous studies have shown that PKD might be caused by cerebellar dysfunction, PRRT2 has not been sufficiently analyzed in some motor-related regions, including the basal ganglia, where dopaminergic neurons are most abundant in the brain. Here, we generated several types of Prrt2 knock-in (KI) mice harboring mutations, such as c.672dupG, that mimics the human pathological mutation c.649dupC and investigated the contribution of Prrt2 to dopaminergic regulation. Regardless of differences in the frameshift sites, all truncating mutations abolished Prrt2 expression within the striatum and cerebral cortex, consistent with previous reports of similar Prrt2 mutant rodents, confirming the loss-of-function nature of these mutations. Importantly, administration of l-dopa, a precursor of dopamine, exacerbated rotarod performance, especially in Prrt2-KI mice. These findings suggest that dopaminergic dysfunction in the brain by the PRRT2 mutation might be implicated in a part of motor symptoms of PKD and related disorders.

PRRT2 Gene Analysis of Paroxysmal Kinesigenic Dyskinesia (PKD) in Thai Children

Objective: To examine the frequency of the proline-rich transmembrane protein-2 (PRRT2) gene mutation in Thai patients with paroxysmal kinesigenic dyskinesia (PKD). Material and Methods: A retrospective study of children aged 0-18 years with a diagnosis of PKD at Siriraj Hospital. The genetic analyses of the PRRT2 gene were done by bidirectional Sanger sequencing.Results: Twelve patients with PKD were included. The known PRRT2 mutation, c.649dupC (p.Arg217Profs*8), was identified in three of the patients (25.0%), one of the nine sporadic cases (11.1%) and two of the three familial cases (66.6%), all from different families. PKD had a complete response to carbamazepine treatment regardless of PRRT2 mutation status. Conclusion: Our study provided the new details of the clinical phenotypes and PRRT2 gene analysis findings for Thai PKD. PRRT2 mutations were identified in our Thai PKD patients with increased detection rates in the familial PKD cases. The c.649dupC (p.Arg217Profs*8) was also found to be a hot-spot mutation in our Thai PKD patients. Furthermore, this study demonstrates the importance of PRRT2 gene analysis in order to properly diagnose and treat these patients.

TMEM151A Variants Cause Paroxysmal Kinesigenic Dyskinesia: A Large-Sample Study.

Paroxysmal kinesigenic dyskinesia (PKD) is the most common type of paroxysmal dyskinesias. Only one-third of PKD patients are attributed to proline-rich transmembrane protein 2 (PRRT2) mutations. We aimed to explore the potential causative gene for PKD. A cohort of 196 PRRT2-negative PKD probands were enrolled for whole-exome sequencing (WES). Gene Ranking, Identification and Prediction Tool, a method of case-control analysis, was applied to identify the candidate genes. Another 325 PRRT2-negative PKD probands were subsequently screened with Sanger sequencing. Transmembrane Protein 151 (TMEM151A) variants were mainly clustered in PKD patients compared with the control groups. 24 heterozygous variants were detected in 25 of 521 probands (frequency=4.80%), including 18 missense and 6 nonsense mutations. In 29 patients with TMEM151A variants, the ratio of male to female was 2.63:1 and the mean age of onset was 12.93 ± 3.15 years. Compared with PRRT2 mutation carriers, TMEM151A-related PKD were more common in sporadic PKD patients with pure phenotype. There was no significant difference in types of attack and treatment outcome between TMEM151A-positive and PRRT2-positive groups. We consolidated mutations in TMEM151A causing PKD with the aid of case-control analysis of a large-scale WES data, which broadens the genotypic spectrum of PKD. TMEM151A-related PKD were more common in sporadic cases and tended to present as pure phenotype with a late onset. Extensive functional studies are needed to enhance our understanding of the pathogenesis of TMEM151A-related PKD. © 2021 International Parkinson and Movement Disorder Society.

Increased responsiveness at the cerebellar input stage in the PRRT2 knockout model of paroxysmal kinesigenic dyskinesia

PRoline-Rich Transmembrane protein-2 (PRRT2) is a recently described neuron-specific type-2 integral membrane protein with a large cytosolic N-terminal domain that distributes in presynaptic and axonal domains where it interacts with several presynaptic proteins and voltage-gated Na+ channels. Several PRRT2 mutations are the main cause of a wide and heterogeneous spectrum of paroxysmal disorders with a loss-of-function pathomechanism. The highest expression levels of PRRT2 in brain occurs in cerebellar granule cells (GCs) and cerebellar dysfunctions participate in the dyskinetic phenotype of PRRT2 knockout (KO) mice. We have investigated the effects of PRRT2 deficiency on the intrinsic excitability of GCs and the input-output relationships at the mossy fiber-GC synapses. We show that PRRT2 KO primary GCs display increased expression of Na+ channels, increased amplitude of Na+ currents and increased length of the axon initial segment, leading to an overall enhancement of intrinsic excitability. In acute PRRT2 KO cerebellar slices, GCs were more prone to action potential discharge in response to mossy fiber activation and exhibited an enhancement of transient and persistent Na+ currents, in the absence of changes at the mossy fiber-GC synapses. The results support a key role of PRRT2 expressed in GCs in the physiological regulation of the excitatory input to the cerebellum and are consistent with a major role of a cerebellar dysfunction in the pathogenesis of the PRRT2-linked paroxysmal pathologies.

Co-existence of Mutations in PRRT2 and ABCC6 Genes in a Turkish Family

Paroxysmal kinesigenic choreoathetosis (PKC) is an inherited disorder with an autosomal dominant mode of inheritance, caused mostly by the mutations in PRRT2 (proline-rich transmembrane protein-2) gene, located on chromosome 16. Pseudoxanthoma elasticum (PXE) is a hereditary metabolic disease with autosomal recessive inheritance resulting from the mutations in the ABCC6 (ATP-Binding Cassette, Subfamily C, Member 6) gene, located also on chromosome 16. Here we present a female patient with familial paroxysmal kinesigenic dyskinesia and benign familial infantile convulsions (BFIC), in whom both a heterozygous truncating frameshift mutation in the PRRT2 gene and a heterozygous missense mutation in the ABCC6 gene were demonstrated. The co-existence of these two mutations has not been reported in the literature. Although the clinical symptomatology of PXE was not present in our patient, some family members of our index case had. Here we present a Turkish family with two different mutations on the same chromosome, namely PRRT2 and ABCC6 mutations. However, because these two mutations have separate parental inheritance and are not in linkage disequilibrium, the co-existence was reported as co-incidental.

Clinical features of patients with paroxysmal kinesigenic dyskinesia, mutation screening of PRRT2 and the effects of morning draughts of oxcarbazepine

BackgroundThe objective of this study was to summarize clinical features and PRRT2 mutations of paediatric paroxysmal kinesigenic dyskinesia (PKD) patients and observe the tolerability and effects of morning draughts of oxcarbazepine.MethodsTwenty patients diagnosed with PKD at Children’s Hospital of Fudan University between January 2011 and December 2015 were enrolled. These patients’ medical records were reviewed. Peripheral venous blood was obtained from all enrolled patients, and polymerase chain reaction (PCR) and Sanger sequencing were used to sequence proline-rich transmembrane protein 2 (PRRT2) gene mutations. Clinical features of PKD patients with and without PRRT2 mutations were compared. All enrolled patients were treated with morning draughts of oxcarbazepine (OXC). The starting dose was 5 mg/kg·d, and the dose was increased by 5 mg/kg·d each week until attacks stopped. Effective doses and adverse effects were recorded.ResultsFor all enrolled patients, dyskinesia was triggered by sudden movement. Dyskinetic movement usually involved the limbs and was bilateral; the majority of enrolled patients exhibited both dystonia and choreoathetosis. We identified PRRT2 mutations in 5 patients, including 4 familial patients and 1 sporadic patient. All 20 patients took low doses of OXC (5–20 mg/kg·d) as draughts in the morning, and dyskinesia attacks stopped in 19 patients.ConclusionsPaediatric PKD patients have various phenotypes. PRRT2 mutations are common in familial cases. OXC taken as morning draughts can be a treatment option for paediatric PKD patients.

Constitutive Inactivation of the PRRT2 Gene Alters Short-Term Synaptic Plasticity and Promotes Network Hyperexcitability in Hippocampal Neurons.

Mutations in PRoline-Rich Transmembrane protein 2 (PRRT2) underlie a group of paroxysmal disorders including epilepsy, kinesigenic dyskinesia and migraine. Most of the mutations lead to impaired PRRT2 expression and/or function, emphasizing the pathogenic role of the PRRT2 deficiency. In this work, we investigated the phenotype of primary hippocampal neurons obtained from mouse embryos in which the PRRT2 gene was constitutively inactivated. Although PRRT2 is expressed by both excitatory and inhibitory neurons, its deletion decreases the number of excitatory synapses without significantly affecting the number of inhibitory synapses or the nerve terminal ultrastructure. Analysis of synaptic function in primary PRRT2 knockout excitatory neurons by live imaging and electrophysiology showed slowdown of the kinetics of exocytosis, weakened spontaneous and evoked synaptic transmission and markedly increased facilitation. Inhibitory neurons showed strengthening of basal synaptic transmission, accompanied by faster depression. At the network level these complex synaptic effects resulted in a state of heightened spontaneous and evoked activity that was associated with increased excitability of excitatory neurons in both PRRT2 knockout primary cultures and acute hippocampal slices. The data indicate the existence of network instability/hyperexcitability as the possible basis of the paroxysmal phenotypes associated with PRRT2 mutations.

PRRT2 mutations in a cohort of Chinese families with paroxysmal kinesigenic dyskinesia and genotype–phenotype correlation reanalysis in literatures

ABSTRACTPurpose of the study: Though rare, children are susceptible to paroxysmal dyskinesias such as paroxysmal kinesigenic dyskinesia, and infantile convulsions and choreoathetosis. Recent studies showed that the cause of paroxysmal kinesigenic dyskinesia or infantile convulsions and choreoathetosis could be proline-rich transmembrane protein 2 (PRRT2) gene mutations.Material and methods: This study analysed PRRT2 gene mutations in 51 families with paroxysmal kinesigenic dyskinesia or infantile convulsions and choreoathetosis by direct sequencing. In particular, we characterize the genotype–phenotype correlation between age at onset and the types of PRRT2 mutations in all published cases.Results: Direct sequencing showed that 12 out of the 51 families had three different pathogenic mutations (c.649dupC, c.776dupG, c.649C>T) in the PRRT2 gene. No significant difference of age at onset between the patients with and without PRRT2 mutations was found in this cohort of patients. A total of 97 different PRRT2 mutations have been reported in 87 studies till now. The PRRT2 mutation classes are wide, and most mutations are frameshift mutations but the most common mutation remains c.649dupC. Comparisons of the age at onset in paroxysmal kinesigenic dyskinesia or infantile convulsions patients with different types of mutations showed no significant difference.Conclusions: This study expands the clinical and genetic spectrums of Chinese patients with paroxysmal kinesigenic dyskinesia and infantile convulsions and choreoathetosis. No clear genotype–phenotype correlation between the age at onset and the types of mutations has been determined.

The PRRT2 knockout mouse recapitulates the neurological diseases associated with PRRT2 mutations

Heterozygous and rare homozygous mutations in PRoline-Rich Transmembrane protein 2 (PRRT2) underlie a group of paroxysmal disorders including epilepsy, kinesigenic dyskinesia episodic ataxia and migraine. Most of the mutations lead to impaired PRRT2 expression and/or function. Recently, an important role for PRTT2 in the neurotransmitter release machinery, brain development and synapse formation has been uncovered. In this work, we have characterized the phenotype of a mouse in which the PRRT2 gene has been constitutively inactivated (PRRT2 KO). β-galactosidase staining allowed to map the regional expression of PRRT2 that was more intense in the cerebellum, hindbrain and spinal cord, while it was localized to restricted areas in the forebrain. PRRT2 KO mice are normal at birth, but display paroxysmal movements at the onset of locomotion that persist in the adulthood. In addition, adult PRRT2 KO mice present abnormal motor behaviors characterized by wild running and jumping in response to audiogenic stimuli that are ineffective in wild type mice and an increased sensitivity to the convulsive effects of pentylentetrazol. Patch-clamp electrophysiology in hippocampal and cerebellar slices revealed specific effects in the cerebellum, where PRRT2 is highly expressed, consisting in a higher excitatory strength at parallel fiber-Purkinje cell synapses during high frequency stimulation. The results show that the PRRT2 KO mouse reproduces the motor paroxysms present in the human PRRT2-linked pathology and can be proposed as an experimental model for the study of the pathogenesis of the disease as well as for testing personalized therapeutic approaches.

Case report: Homozygous PRRT2 mutation in ICCA Egyptian family with reduced penetrance

Infantile convulsions and choreoathetosis (ICCA) syndrome is a rare neurological genetic disorder inherited in an autosomal dominant manner with incomplete penetrance. It is characterized by the association of benign infantile seizures (BIS) at age 3–12months with paroxysmal kinesigenic choreoathetosis (PKC) later in life. Mutations in proline-rich transmembrane protein 2 (PRRT2) gene have been recently identified as the main cause of ICCA and other related disorders. Few ICCA cases with homozygous mutations have been reported, where they exhibited more severe clinical phenotype including intellectual disability. Here we report two Egyptian siblings with ICCA whose molecular analysis of PRRT2 revealed homozygous c.649dupC mutation. However, they have not developed any physical or cognitive disabilities. Moreover, their parents, who found to be heterozygous for the mutation, did not display any of the disease phenotype during their infancy and childhood. Low penetrance and variable expressivity of ICCA could be attributed to specific genetic modifiers and/or environmental factors that require further investigations to be identified.

PRRT2 mutations lead to neuronal dysfunction and neurodevelopmental defects.

Mutations in the proline-rich transmembrane protein 2 (PRRT2) gene cause a wide spectrum of neurological diseases, ranging from paroxysmal kinesigenic dyskinesia (PKD) to mental retardation and epilepsy. Previously, seven PKD-related PRRT2 heterozygous mutations were identified in the Taiwanese population: P91QfsX, E199X, S202HfsX, R217PfsX, R217EfsX, R240X and R308C. This study aimed to investigate the disease-causing mechanisms of these PRRT2 mutations. We first documented that Prrt2 was localized at the pre- and post-synaptic membranes with a close spatial association with SNAP25 by synaptic membrane fractionation and immunostaining of the rat neurons. Our results then revealed that the six truncating Prrt2 mutants were accumulated in the cytoplasm and thus failed to target to the cell membrane; the R308C missense mutant had significantly reduced protein expression, suggesting loss-of function effects generated by these mutations. Using in utero electroporation of shRNA into cortical neurons, we further found that knocking down Prrt2 expression in vivo resulted in a delay in neuronal migration during embryonic development and a marked decrease in synaptic density after birth. These pathologic effects and novel disease-causing mechanisms may contribute to the severe clinical symptoms in PRRT2–related diseases.

Novel Locus for Paroxysmal Kinesigenic Dyskinesia Mapped to Chromosome 3q28-29.

Paroxysmal kinesigenic dyskinesia (PKD) is characterized by recurrent and brief attacks of dystonia or chorea precipitated by sudden movements. It can be sporadic or familial. Proline-Rich Transmembrane Protein 2 (PRRT2) has been shown to be a common causative gene of PKD. However, less than 50% of patients with primary PKD harbor mutations in PRRT2. The aim of this study is to use eight families with PKD to identify the pathogenic PRRT2 mutations, or possible novel genetic cause of PKD phenotypes. After extensive clinical investigation, direct sequencing and mutation analysis of PRRT2 were performed on patients from eight PKD families. A genome-wide STR and SNP based linkage analysis was performed in one large family that is negative for pathogenic PRRT2 mutations. Using additional polymorphic markers, we identified a novel gene locus on chromosome 3q in this PRRT2-mutation-negative PKD family. The LOD score for the region between markers D3S1314 and D3S1256 is 3.02 and we proposed to designate this locus as Episodic Kinesigenic Dyskinesia (EKD3). Further studies are needed to identify the causative gene within this locus.

The evolving spectrum of PRRT2-associated paroxysmal diseases.

Next-generation sequencing has identified mutations in the PRRT2 (proline-rich transmembrane protein 2) gene as the leading cause for a wide and yet evolving spectrum of paroxysmal diseases. PRRT2 mutations are found in the majority of patients with benign familial infantile epilepsy, infantile convulsions and choreoathetosis and paroxysmal kinesigenic dyskinesia, confirming a common disease spectrum that had previously been suggested based on gene linkage analyses and shared clinical features. Beyond these clinical entities, PRRT2 mutations have been described in other childhood-onset movement disorders, different forms of seizures, headache disorders, and intellectual disability. PRRT2 encodes a protein that is expressed in the central nervous system and is thought to be involved in the modulation of synaptic neurotransmitter release. The vast majority of mutations lead to a truncated protein or no protein at all and thus to a haploinsufficient state. The subsequent reduction of PRRT2 protein may lead to altered synaptic neurotransmitter release and dysregulated neuronal excitability in various regions of the brain, resulting in paroxysmal movement disorders and seizure phenotypes. In this review, we examine the genetics and neurobiology of PRRT2 and summarize the evolving clinical and molecular spectrum of PRRT2-associated diseases. Through a comprehensive review of 1444 published cases, we provide a detailed assessment of the demographics, disease characteristics and genetic findings of patients with PRRT2 mutations. Benign familial infantile epilepsy (41.7%; n = 602), paroxysmal kinesigenic dyskinesia (38.7%; n = 560) and infantile convulsions and choreoathetosis (14.3%; n = 206) constitute the vast majority of PRRT2-associated diseases, leaving 76 patients (5.3%) with a different primary diagnosis. A positive family history is present in 89.1% of patients; and PRRT2 mutations are familial in 87.1% of reported cases. Seventy-three different disease-associated PRRT2 mutations (35 truncating, 22 missense, three extension mutations, six putative splice site changes, and seven changes that lead to a complete PRRT2 deletion) have been described to date, with the c.649dupC frameshift mutation accounting for the majority of cases (78.5%). Expanding the genetic landscape, 15 patients with biallelic PRRT2 mutations and six patients with 16p11.2 microdeletions and a paroxysmal kinesigenic dyskinesia phenotype have been reported. Probing the phenotypic boundaries of PRRT2-associated disorders, several movement, seizure and headache disorders have been linked to PRRT2 mutations in a subset of patients. Of these, hemiplegic migraine emerges as a novel PRRT2-associated phenotype. With this comprehensive review of PRRT2-associated diseases, we hope to provide a scientific resource for informing future research, both in laboratory models and in clinical studies.

Clinical features and PRRT2 gene mutation in paroxysmal kinesigenic dyskinesia

To investigate the clinical features and proline-rich transmembrane protein 2 (PRRT2) gene mutation in patients with paroxysmal kinesigenic dyskinesia (PKD). Clinical information was collected at Peking University First Hospital from January 2004 to July 2014. In total, 10 patients with PKD were recruited, and all were males. Among them, four patients were the probands from four PKD families and the other six patients were sporadic cases. Clinical information was analyzed. Peripheral blood samples for DNA study were collected from PKD patients and their family members. Genomic DNA was extracted using standard procedures. Mutation analysis of PRRT2 was performed by Sanger sequencing after PCR. Of the 10 patients, the median age of dyskinesias onset was 10 years, ranging from 4 to 13 years. The description of their attacks were abnormal involuntary movements provoked by sudden movements, without loss of consciousness. Five patients exhibited dystonia, two patients exhibited choreoathetosis, and three patients had mixed (dystonia and choreoathetosis) dyskinesias. The duration of the attacks lasted for 3 to 30 seconds. The frequency ranged from once per month to twenty times per day. PRRT2 mutations, c. 649_650insC (p. R217PfsX8), were found in all the four PKD families. Mutation c. 649_650insC was also detected in two of the six sporadic PKD cases, inheriting from their asymptomatic mother. The onset age of PKD could be in the early childhood. The clinical features of the familial cases and sporadic cases showed no difference. The attacks manifested as dystonia, choreathetosis, or mixed. PRR2 mutations could be identified in familial or sporadic cases with PKD. Mutation c. 649_650insC is the hotspot mutation of PRRT2 gene.

Single nucleotide variations in CLCN6 identified in patients with benign partial epilepsies in infancy and/or febrile seizures.

Nucleotide alterations in the gene encoding proline-rich transmembrane protein 2 (PRRT2) have been identified in most patients with benign partial epilepsies in infancy (BPEI)/benign familial infantile epilepsy (BFIE). However, not all patients harbor these PRRT2 mutations, indicating the involvement of genes other than PRRT2. In this study, we performed whole exome sequencing analysis for a large family affected with PRRT2-unrelated BPEI. We identified a non-synonymous single nucleotide variation (SNV) in the voltage-sensitive chloride channel 6 gene (CLCN6). A cohort study of 48 BPEI patients without PRRT2 mutations revealed a different CLCN6 SNV in a patient, his sibling and his father who had a history of febrile seizures (FS) but not BPEI. Another study of 48 patients with FS identified an additional SNV in CLCN6. Chloride channels (CLCs) are involved in a multitude of physiologic processes and some members of the CLC family have been linked to inherited diseases. However, a phenotypic correlation has not been confirmed for CLCN6. Although we could not detect significant biological effects linked to the identified CLCN6 SNVs, further studies should investigate potential CLCN6 variants that may underlie the genetic susceptibility to convulsive disorders.

PRRT2 mutations are related to febrile seizures in epileptic patients.

Previous studies reported that the proline-rich transmembrane protein 2 (PRRT2) gene was identified to be related to paroxysmal kinesigenic dyskinesia (PKD), infantile convulsions with PKD, PKD with migraine and benign familial infantile epilepsy (BFIE). The present study explores whether the PRRT2 mutation is a potential cause of febrile seizures, including febrile seizures plus (FS+), generalized epilepsy with febrile seizures plus (GEFS+) and Dravet syndrome (DS); thus, it may provide a new drug target for personalized medicine for febrile seizure patients. We screened PRRT2 exons in a cohort of 136 epileptic patients with febrile seizures, including FS+, GEFS+ and DS. PRRT2 genetic mutations were identified in 25 out of 136 (18.4%) febrile seizures in epileptic patients. Five loss-of-function and coding missense mutations were identified: c.649delC (p.R217Efs*12), c.649_650insC (p.R217Pfs*8), c.412C>G (p.Pro138Ala), c.439G>C (p.Asp147His) and c.623C>A (p.Ser208Tyr). PRRT2 variants were probably involved in the etiology of febrile seizures in epileptic patients.

Phenotypes and PRRT2 mutation analysis in families with benign familial infantile epilepsy

To study the phenotypes and proline-rich transmembrane protein 2 (PRRT2) mutations in families with benign familial infantile epilepsy (BFIE). Data of all BFIE probands and their family members were collected from Peking University First Hospital between September 2006 and August 2013. Clinical phenotypes of affected members were analyzed. Genomic DNA was extracted from peripheral blood samples with standard protocol. Mutations in PRRT2 were screened using PCR amplification and Sanger sequencing. Twenty-nine BFIE families were recruited in this study. In total, 110 family members were affected. The age of seizure onset of these affected members was between 2 and 12 months (median: 4.5 months). All probands presented with clusters of seizures. Two probands had one seizure induced by diarrhea respectively at 25 months and 31 months. In four BFIE families, four family members had a history of febrile seizures. PRRT2 mutations were found in 17 of the 29 (58.6%) BFIE families. Mutation c.649_650insC was detected in 12 of the 17 families with PRRT2 mutations. Mutation c.649delC (p.R217EfsX12) was identified in three families. Mutation c.323_324delCA (p. T108SfsX25) and c.904_ 905insG (p. D302GfsX39) were detected in one family, respectively. The minimum seizure onset age of affected members in BFIE families was 2 months of age. The seizures often occur in clusters. PRRT2 is the major causative gene of BFIE in Chinese families. Mutation c.649_650insC is the hotspot mutation of PRRT2. A novel mutation c.323_324delCA was first reported in BFIE family. Few affected members with PRRT2 mutation presented with febrile seizures phenotype.

PRRT2 truncated mutations lead to nonsense-mediated mRNA decay in Paroxysmal Kinesigenic Dyskinesia.

Paroxysmal Kinesigenic Dyskinesia (PKD) is an episodic involuntary movement disorder characterized by recurrent and brief involuntary movements. Proline-rich transmembrane protein 2 (PRRT2) has been identified as the causative gene for PKD, Benign familial infantile convulsions (BFIC) and Infantile convulsions with choreoathetosis (ICCA). As well, PRRT2 mutations have been detected in patients with PED or PNKD. To date, most of the mutations have been found to be nonsense. We used inhibitors of nonsense-mediated mRNA decay (NMD) pathway --emetine dihydrochloride hydrate and cycloheximide and silencing regulator of nonsense transcripts 1(UPF1) with immortalized lymphoblasts to detect whether the truncated mutations lead to NMD, a type of mRNA surveillance in every eukaryotic cell proved so far and that generally degrades mRNA containing premature translation termination codons (PTCs). In addition, we transfected the SH-SY5Y cells with wild-type and mutant PRRT2 plasmids to identify the PRRT2 protein's subcellular localization. We detected, low expression of truncated PRRT2 and was further rescued by applying the inhibitor of NMD pathway, suggesting that NMD plays an important role in the pathogenesis of PKD by haplo-insufficiency. Moreover, for the small portion of undegraded mutant PRRT2 that was translated into truncated proteins, their cellular localization changed from membrane to cytoplasm and nuclear, which might lead to a functional loss. We suggest that the NMD of truncated mutation of PRRT2 and altered cellular localization of undegraded of PRRT2, might lead to PKD.

Novel loss-of-function PRRT2 mutation causes paroxysmal kinesigenic dyskinesia in a Han Chinese family.

BackgroundMutations in proline-rich transmembrane protein 2 (PRRT2) are a cause of paroxysmal kinesigenic dyskinesia (PKD). In this study, we investigated the PRRT2 gene mutation in a Chinese Han family with PKD and study the pathogenesis of the mutation with PRRT2 gene.MethodsPeripheral venous blood was taken from the family members. Sanger sequencing was used for novel mutation sequencing. For the pathogenesis with the novel mutation was analyzed by bioinformatics, real-time PCR, subcellular localization and Western blot.ResultsThe Sanger sequencing showed a novel mutation, c.186-187delGC, a deletion mutation, in exon 2 of the PRRT2 gene, the frameshift mutation generated a truncated protein that was stably expressed in transfected Human embryonic kidney (HEK) 293 cells. A subcellular localization assay in COS-7 cells with GFP-tagged protein showed nuclear localization for the mutant protein while the wild-type protein was localized in membranes. Co-transfection of HEK293 cells with wild-type and mutant expression plasmids cells did not influence mRNA or protein expression from the wild-type plasmid.ConclusionsOur findings demonstrated that the c.186-187delGC mutation resulted in a truncated protein from the PRRT2 gene to involve in PKD pathogenesis with haploinsufficiency. The results extend the mutation spectrum of the PRRT2 gene and provide a new example for studying the pathogenesis of the mutated PRRT2 gene.

Successful control with carbamazepine of family with paroxysmal kinesigenic dyskinesia of PRRT2 mutation.

Paroxysmal kinesigenic dyskinesia (PKD), a rare paroxysmal movement disorder often misdiagnosed as epilepsy, is characterized by recurrent, brief dyskinesia attacks triggered by sudden voluntary movement. Pathophysiological mechanism of PKD remains not well understood. Ion channelopathy has been suggested, since the disease responds well to ion channel blockers. Mutations in proline-rich transmembrane protein 2 (PRRT2) were recently identified in patients with familial PKD. To extend these genetic reports, we studied a family with clinical manifestations of familial PKD responding well to low dose carbamazepine. Therapeutic dose ranged from 1.5 to 2.0 mg/ kg/day, below that in seizure control. One insertion mutation c.649_650insC (p.P217fsX7) was identified in three patients of the family. This study avers PRRT2’s high sensitivity for PKD phenotype. Identification of genes underlying pathogenesis will enhance diagnosis and treatment. Function of PRRT2 and its role in PKD warrant further investigation.