TMEM151A variants cause paroxysmal kinesigenic dyskinesia

A new genetic diagnosis strategy for paroxysmal kinesigenic dyskinesia: Targeted high-throughput detection of PRRT2 gene c.649 locus

BACKGROUND

Paroxysmal kinesigenic dyskinesia (PKD) is the most prevalent kind type of paroxysmal Dyskinesia, characterized by recurrent and transient episodes of involuntary movements. Most PKD cases were attributed to the proline-rich transmembrane protein 2 (PRRT2) gene, in which the c.649 region is a hotspot for known mutations. Even though some patients with PKD have been genetically diagnosed using whole-exome sequencing (WES) and Sanger sequencing, there are still cases of missed diagnoses due to the limitations of sequencing technology and analytic methods on throughput.

METHODS

Patients meeting the diagnosis criteria of PKD with negative results of PRRT2-Sanger sequencing and WES were included in this study. Mutation screening and targeted high-throughput sequencing were performed to analyze and verify the sequencing results of the potential mutations.

RESULTS

Six patients with PKD with high mutation ratios of c.649dupC were screened using our targeted high-throughput sequencing from 26 PKD patients with negative results of PRRT2-Sanger sequencing and WES (frequency = 23.1%), which compensated for the comparatively shallow sequencing depth and statistical flaws in this region. Compared with the local normal population and other patients with PKD, the mutation ratios of c.649dupC of these six patients with PKD were much higher and also had truncated protein structures and differentially altered mRNA expression.

CONCLUSION

Based on the above studies, we emphasize the routine targeted high-throughput sequencing of the c.649 site in the PRRT2 gene in so-called genetic-testing-negative patients with PKD, and manually calculate the deletion and duplication mutations depth and ratios to lower the rate of clinical misdiagnosis.

Rare Missense Variants in KCNJ10 Are Associated with Paroxysmal Kinesigenic Dyskinesia

BACKGROUND

Although the group of paroxysmal kinesigenic dyskinesia (PKD) genes is expanding, the molecular cause remains elusive in more than 50% of cases.

OBJECTIVE

The aim is to identify the missing genetic causes of PKD.

METHODS

Phenotypic characterization, whole exome sequencing and association test were performed among 53 PKD cases.

RESULTS

We identified four causative variants in KCNJ10, already associated with EAST syndrome (epilepsy, cerebellar ataxia, sensorineural hearing impairment and renal tubulopathy). Homozygous p.(Ile209Thr) variant was found in two brothers from a single autosomal recessive PKD family, whereas heterozygous p.(Cys294Tyr) and p.(Thr178Ile) variants were found in six patients from two autosomal dominant PKD families. Heterozygous p.(Arg180His) variant was identified in one additional sporadic PKD case. Compared to the Genome Aggregation Database v2.1.1, our PKD cohort was significantly enriched in both rare heterozygous (odds ratio, 21.6; P = 9.7 × 10-8) and rare homozygous (odds ratio, 2047; P = 1.65 × 10-6) missense variants in KCNJ10.

CONCLUSIONS

We demonstrated that both rare monoallelic and biallelic missense variants in KCNJ10 are associated with PKD. © 2024 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

Identification of a de novo CACNA1B variant and a start-loss ADRA2B variant in paroxysmal kinesigenic dyskinesia

Paroxysmal kinesigenic dyskinesia (PKD) represents the most prevalent form of paroxysmal dyskinesia, characterized by recurrent and transient attacks of involuntary movements triggered by a sudden voluntary action. In this study, whole-exome sequencing was conducted on a cohort of Chinese patients to identify causal mutations. In one young female case, a de novo CACNA1B variant (NM_000718.3:exon3:c.479C > T:p.S160F) was identified as the causative lesion. This finding may broaden the phenotypic spectrum of CACNA1B mutations and provide a prospective cause of primary PKD. Additionally, a novel start-loss variant (NM_000682.7:c.3G > A) within ADRA2B further denied its association with benign adult familial myoclonic epilepsy, and a KCNQ2 E515D variant that was reported as a genetic susceptibility factor for seizures had no damaging effect in this family. In sum, this study established a correlation between CACNA1B and primary PKD, and found valid evidence that further negates the pathogenic role of ADRA2B in benign adult familial myoclonic epilepsy.

Both gain- and loss-of-function variants of KCNA1 are associated with paroxysmal kinesigenic dyskinesia

KCNA1 is the coding gene for Kv1.1 voltage-gated potassium-channel α subunit. Three variants of KCNA1 have been reported to manifest as paroxysmal kinesigenic dyskinesia (PKD), but the correlation between them remains unclear due to the phenotypic complexity of KCNA1 variants as well as the rarity of PKD cases. Using the whole exome sequencing followed by Sanger sequencing, we screen for potential pathogenic KCNA1 variants in patients clinically diagnosed with paroxysmal movement disorders and identify three previously unreported missense variants of KCNA1 in three unrelated Chinese families. The proband of one family (c.496G>A, p.A166T) manifests as episodic ataxia type 1, and the other two (c.877G>A, p.V293I and c.1112C>A, p.T371A) manifest as PKD. The pathogenicity of these variants is confirmed by functional studies, suggesting that p.A166T and p.T371A cause a loss-of-function of the channel, while p.V293I leads to a gain-of-function with the property of voltage-dependent gating and activation kinetic affected. By reviewing the locations of PKD-manifested KCNA1 variants in Kv1.1 protein, we find that these variants tend to cluster around the pore domain, which is similar to epilepsy. Thus, our study strengthens the correlation between KCNA1 variants and PKD and provides more information on genotype-phenotype correlations of KCNA1 channelopathy.

An Electroencephalography Profile of Paroxysmal Kinesigenic Dyskinesia

Paroxysmal kinesigenic dyskinesia (PKD) is associated with a disturbance of neural circuit and network activities, while its neurophysiological characteristics have not been fully elucidated. This study utilized the high-density electroencephalogram (hd-EEG) signals to detect abnormal brain activity of PKD and provide a neural biomarker for its clinical diagnosis and PKD progression monitoring. The resting hd-EEGs are recorded from two independent datasets and then source-localized for measuring the oscillatory activities and function connectivity (FC) patterns of cortical and subcortical regions. The abnormal elevation of theta oscillation in wildly brain regions represents the most remarkable physiological feature for PKD and these changes returned to healthy control level in remission patients. Another remarkable feature of PKD is the decreased high-gamma FCs in non-remission patients. Subtype analyses report that increased theta oscillations may be related to the emotional factors of PKD, while the decreased high-gamma FCs are related to the motor symptoms. Finally, the authors established connectome-based predictive modelling and successfully identified the remission state in PKD patients in dataset 1 and dataset 2. The findings establish a clinically relevant electroencephalography profile of PKD and indicate that hd-EEG can provide robust neural biomarkers to evaluate the prognosis of PKD.

TMEM151A variants associated with paroxysmal kinesigenic dyskinesia

TMEM151A, located at 11q13.2 and encoding transmembrane protein 151A, was recently reported as causative for autosomal dominant paroxysmal kinesigenic dyskinesia (PKD). Here, through comprehensive analysis of sporadic and familial cases, we expand the clinical and mutation spectrum of PKD. In doing so, we clarify the clinical and genetic features of Chinese PKD patients harboring TMEM151A variants and further explore the relationship between TMEM151A mutations and PKD. Whole exome sequencing was performed on 26 sporadic PKD patients and nine familial PKD pedigrees without PRRT2 variants. Quantitative real-time PCR was used to assess the gene expression of frameshift mutant TMEM151A in a PKD patient. TMEM151A variants reported to date were reviewed. Four TMEM151A variants were detected in four unrelated families with 12 individuals, including a frameshift mutation [c.606_607insA (p.Val203fs)], two missense mutations [c.166G > A (p.Gly56Arg) and c.791T > C (p.Val264Ala)], and a non-pathogenic variant [c.994G > A (p.Gly332Arg)]. The monoallelic frameshift mutation [c.606_607insA (p.Val203fs)] may cause TMEM151A mRNA decay, suggesting a potential pathogenic mechanism of haploinsufficiency. Patients with TMEM151A variants had short-duration attacks and presented with dystonia. Our study provides a detailed clinical description of PKD patients with TMEM151A mutations and reports a new disease-causing mutation, expanding the known phenotypes caused by TMEM151A mutations and providing further detail about the pathoetiology of PKD.

Translating Genetic Discovery into a Mechanistic Understanding of Pediatric Movement Disorders: Lessons from Genetic Dystonias and Related Disorders

The era of next-generation sequencing has increased the pace of gene discovery in the field of pediatric movement disorders. Following the identification of novel disease-causing genes, several studies have aimed to link the molecular and clinical aspects of these disorders. This perspective presents the developing stories of several childhood-onset movement disorders, including paroxysmal kinesigenic dyskinesia, myoclonus-dystonia syndrome, and other monogenic dystonias. These stories illustrate how gene discovery helps focus the research efforts of scientists trying to understand the mechanisms of disease. The genetic diagnosis of these clinical syndromes also helps clarify the associated phenotypic spectra and aids the search for additional disease-causing genes. Collectively, the findings of previous studies have led to increased recognition of the role of the cerebellum in the physiology and pathophysiology of motor control-a common theme in many pediatric movement disorders. To fully exploit the genetic information garnered in the clinical and research arenas, it is crucial that corresponding multi-omics analyses and functional studies also be performed at scale. Hopefully, these integrated efforts will provide us with a more comprehensive understanding of the genetic and neurobiological bases of movement disorders in childhood.

Novel missense variant in the TMEM151A gene causing paroxysmal kinesigenic dyskinesia: a case report with literature review

BACKGROUND

Paroxysmal kinesigenic dyskinesia (PKD) is a rare movement disorder with high clinical and genetic heterogeneity. Proline-rich transmembrane protein 2 (PRRT2) was identified as the first causative gene for PKD in 2011. Recently, heterozygous variants in transmembrane protein 151A (TMEM151A) were identified as another pathogenic cause of PKD.

CASE DESCRIPTION

A 16-year-old man diagnosed with PKD exhibited hemidystonia triggered by sudden voluntary movements. His mother also had similar symptoms since the age of 20. Whole-exome sequencing revealed a likely pathogenic missense variant (c.892 T > C) in the TMEM151A gene. At the same time, we reviewed the literature focusing on the molecular characteristics and the clinical phenotypes in patients with TMEM151A variants, especially within the same family.

CONCLUSION

This case further validated the pathogenic role of TMEM151A variants in PKD. The findings of interfamilial and intrafamilial variability in the phenotypes expanded our understanding of TMEM151A-related PKD.

TMEM151A as an alternative to PRRT2 in paroxysmal kinesigenic dyskinesia: About three new cases

Paroxysmal kinesigenic dyskinesia (PKD) are movement disorders triggered by sudden voluntary movement. Variants in the TMEM151A gene have recently been associated with the development of PKD. We report three patients presenting PKD with different TMEM151A mutations, two of which have not been described yet.

The Pathogenesis of Paroxysmal Kinesigenic Dyskinesia: Current Concepts

Paroxysmal kinesigenic dyskinesia (PKD) is a movement disorder characterized by recurrent and transient episodes of involuntary movements, including dystonia, chorea, ballism, or a combination of these, which are typically triggered by sudden voluntary movement. Disturbance of the basal ganglia-thalamo-cortical circuit has long been considered the cause of involuntary movements. Impairment of the gating function of the basal ganglia can cause an aberrant output toward the thalamus, which in turn leads to excessive activation of the cerebral cortex. Structural and functional abnormalities in the basal ganglia, thalamus, and cortex and abnormal connections between these brain regions have been found in patients with PKD. Recent studies have highlighted the role of the cerebellum in PKD. Insufficient suppression from the cerebellar cortex to the deep cerebellar nuclei could lead to overexcitation of the thalamocortical pathway. Therefore, this literature review aims to provide a comprehensive overview of the current research progress to explore the neural circuits and pathogenesis of PKD and promote further understanding and outlook on the pathophysiological mechanism of movement disorders. © 2023 International Parkinson and Movement Disorder Society.

Genetic Links to Episodic Movement Disorders: Current Insights

Episodic or paroxysmal movement disorders (PxMD) are conditions, which occur episodically, are transient, usually have normal interictal periods, and are characterized by hyperkinetic disorders, including ataxia, chorea, dystonia, and ballism. Broadly, these comprise paroxysmal dyskinesias (paroxysmal kinesigenic and non-kinesigenic dyskinesia [PKD/PNKD], paroxysmal exercise-induced dyskinesias [PED]) and episodic ataxias (EA) types 1-9. Classification of paroxysmal dyskinesias has traditionally been clinical. However, with advancement in genetics and the discovery of the molecular basis of several of these disorders, it is becoming clear that phenotypic pleiotropy exists, that is, the same variant may give rise to a variety of phenotypes, and the classical understanding of these disorders requires a new paradigm. Based on molecular pathogenesis, paroxysmal disorders are now categorized as synaptopathies, transportopathies, channelopathies, second-messenger related disorders, mitochondrial or others. A genetic paradigm also has an advantage of identifying potentially treatable disorders, such as glucose transporter 1 deficiency syndromes, which necessitates a ketogenic diet, and ADCY5-related disorders, which may respond to caffeine. Clues for a primary etiology include age at onset below 18 years, presence of family history and fixed triggers and attack duration. Paroxysmal movement disorder is a network disorder, with both the basal ganglia and the cerebellum implicated in pathogenesis. Abnormalities in the striatal cAMP turnover pathway may also be contributory. Although next-generation sequencing has restructured the approach to paroxysmal movement disorders, the genetic underpinnings of several entities remain undiscovered. As more genes and variants continue to be reported, these will lead to enhanced understanding of pathophysiological mechanisms and precise treatment.

Paroxysmal movement disorders: Paroxysmal dyskinesia and episodic ataxia

Paroxysmal movement disorders have traditionally been classified into paroxysmal dyskinesia (PxD), which consists in attacks of involuntary movements (mainly dystonia and/or chorea) without loss of consciousness, and episodic ataxia (EA), which features spells of cerebellar dysfunction with or without interictal neurological manifestations. In this chapter, PxD will be discussed first according to the trigger-based classification, thus reviewing clinical, genetic, and molecular features of paroxysmal kinesigenic dyskinesia, paroxysmal nonkinesigenic dyskinesia, and paroxysmal exercise-induced dyskinesia. EA will be presented thereafter according to their designated gene or genetic locus. Clinicogenetic similarities among paroxysmal movement disorders have progressively emerged, which are herein highlighted along with growing evidence that their pathomechanisms overlap those of epilepsy and migraine. Advances in our comprehension of the biological pathways underlying paroxysmal movement disorders, which involve ion channels as well as proteins associated with the vesical synaptic cycle or implicated in neuronal energy metabolism, may represent the cornerstone for defining a shared pathophysiologic framework and developing target-specific therapies.

Aberrant Neuregulin 1/ErbB Signaling in Charcot-Marie-Tooth Type 4D Disease

Charcot-Marie-Tooth type 4D (CMT4D) is an autosomal recessive demyelinating form of CMT characterized by progressive motor and sensory neuropathy. N-myc downstream regulated gene 1 (NDRG1) is the causative gene for CMT4D. Although more CMT4D cases have been reported, the comprehensive molecular mechanism underlying CMT4D remains elusive. Here, we generated a novel knockout mouse model in which the fourth and fifth exons of the Ndrg1 gene were removed. Ndrg1-deficient mice develop early progressive demyelinating neuropathy and limb muscle weakness. The expression pattern of myelination-related transcriptional factors, including SOX10, OCT6, and EGR2, was abnormal in Ndrg1-deficient mice. We further investigated the activation of the ErbB2/3 receptor tyrosine kinases in Ndrg1-deficient sciatic nerves, as these proteins play essential roles in Schwann cell myelination. In the absence of NDRG1, although the total ErbB2/3 receptors expressed by Schwann cells were significantly increased, levels of the phosphorylated forms of ErbB2/3 and their downstream signaling cascades were decreased. This change was not associated with the level of the neuregulin 1 ligand, which was increased in Ndrg1-deficient mice. In addition, the integrin β4 receptor, which interacts with ErbB2/3 and positively regulates neuregulin 1/ErbB signaling, was significantly reduced in the Ndrg1-deficient nerve. In conclusion, our data suggest that the demyelinating phenotype of CMT4D disease is at least in part a consequence of molecular defects in neuregulin 1/ErbB signaling.

Screening of the TMEM151A Gene in Patients With Paroxysmal Kinesigenic Dyskinesia and Other Movement Disorders

Background

Paroxysmal kinesigenic dyskinesia (PKD) is a rare neurological disorder characterized by recurrent involuntary movements usually triggered by sudden movements. Mutations in the TMEM151A gene were found to be the causative factor of PKD in recent studies. It has also been revealed that loss-of-function is the mechanism by which TMEM151A mutations cause PKD.

Methods

To investigate the genetic basis of PKD and broaden the clinical spectrum of the TMEM151A mutations, we recruited 181 patients of Chinese origin with movement disorders (MDs), including 39 PRRT2-negative PKD, 3 paroxysmal exercise-induced dyskinesia (PED), 2 paroxysmal non-kinesigenic dyskinesia (PNKD), 127 isolated dystonia, 8 choreas, and 2 myoclonus-dystonia syndromes. Whole-exome sequencing was applied to identify their possible disease-causing mutations. Then, Sanger sequencing was performed for validation and co-segregation analysis. Genetic analysis was also performed on additional family members of patients with TMEM151A mutations. Clinical manifestations of all PKD cases with mutations in TMEM151A reported, so far, were reviewed.

Results

Two novel variants of the TMEM151A gene (NM_153266.4, NP_694998.1), c.627_643dup (p.A215Gfs^*53) and c.627delG (p.L210Wfs^*52), were identified in 2 patients with PKD by whole-exome sequencing and further Sanger sequencing. Both variants were inherited by the patients from their respective mothers. No mutation of the TMEM151A gene was found in the other type of movement disorders. In reviewing the clinical presentation of TMEM151A-related PKD, no statistically significant difference in the age of onset, family history, duration of attacks, laterality, and phenotype was found between genders. More male patients received treatment and had a good response. A higher proportion of female patients did not receive any treatment, possibly because they had a milder condition of the disease.

Conclusions

This study further validated the role of TMEM151A in PKD. Future studies on protein function will be needed to ascertain the pathogenesis of TMEM151A in PKD.

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

BACKGROUND

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.

OBJECTIVE

We aimed to explore the potential causative gene for PKD.

METHODS

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.

RESULTS

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.

CONCLUSIONS

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.

Features Differ Between Paroxysmal Kinesigenic Dyskinesia Patients with PRRT2 and TMEM151A Variants

BACKGROUND

Mutations in proline-rich transmembrane protein 2 (PRRT2) are the major cause of paroxysmal kinesigenic dyskinesia (PKD). We recently reported transmembrane protein 151A (TMEM151A) mutations caused PKD. Herein, we aimed to conduct phenotypic comparisons of patients with PKD carrying PRRT2 variants, carrying TMEM151A variants, and carrying neither the PRRT2 nor TMEM151A variant.

METHODS

Sanger sequencing of PRRT2 and TMEM151A was performed, and phenotypic characteristics were analyzed.

RESULTS

In a cohort of 131 PKD probands (108 without PRRT2 variants and 23 newly recruited), five novel TMEM151A variants were identified and one (c.647C > A) occurred de novo. Together with our previous studies, PRRT2 and TMEM151A variants accounted for 34.7% (85/245) and 6.9% (17/245) of PKD probands, respectively. Compared with patients carrying PRRT2 variants, those with TMEM151A variants tended to exbibit dystonia with shorter durations, have no history of benign infantile epilepsy, and have residual attacks/aura when treated with carbamazepine/oxcarbazepine.

CONCLUSIONS

Patients with TMEM151A variants have different features from patients with PRRT2 variants. © 2022 International Parkinson and Movement Disorder Society.

Paroxysmal Kinesigenic Dyskinesia Caused by 16p11.2 Microdeletion and Related Clinical Features

Background and Objectives

Isolated paroxysmal kinesigenic dyskinesia (PKD) is mainly caused by PRRT2 variants and TMEM151A variants. Patients with proximal 16p11.2 microdeletion (16p11.2MD) (including PRRT2) often have neurodevelopmental phenotypes, whereas a few patients have PKD. Here, we aimed to identify 16p11.2MD in patients with PKD and describe the related phenotypes.

Methods

Whole-exome sequencing and bioinformatics analysis of copy number variant (CNV) were performed in patients with PKD carrying neither PRRT2 nor TMEM151A variant. Quantitative PCR and low-coverage whole-genome sequencing verified the CNV.

Results

We identified 9 sporadic patients with PKD and 16p11.2MD (∼535 kb), accounting for 9.6% (9/94) of our patients. Together with 9 previously reported patients with PKD and 16p11.2MD, we found that 16p11.2MD was de novo in 11 of 12 tested patients and inherited from a parent in the other patient. And 80% (12/15) of these patients had a mild language delay, 64.3% (9/14) had compromised learning ability, 42.9% (6/14) had a mild motor delay, and 50% (6/12) had abnormal neuroimaging findings. No severe autism disorders were observed.

Discussion

Mild developmental problems may be overlooked. A detailed inquiry of developmental history and CNV testing are necessary to distinguish patients with 16p11.2MD from isolated PKD.