Dystonia as a prominent presenting feature in developmental and epileptic encephalopathies: A case series

Dyskinetic crisis in GNAO1-related disorders: clinical perspectives and management strategies

Background

GNAO1-related disorders (GNAO1-RD) encompass a diverse spectrum of neurodevelopmental and movement disorders arising from variants in the GNAO1 gene. Dyskinetic crises, marked by sudden and intense exacerbations of abnormal involuntary movements, present a significant challenge in GNAO1-RD.

Objectives

This study aimed to establish a standardized framework for understanding dyskinetic crises, addressing crucial aspects such as definition, triggers, diagnostic criteria, complications, and management strategies.

Methods

A Delphi consensus process was conducted involving international experts in GNAO1-RD. The panel of thirteen experts participated in three voting rounds, discussing 90 statements generated through a literature review and clinical expertise.

Results

Consensus was achieved on 31 statements, defining dyskinetic crises as abrupt, paroxysmal episodes involving distinct abnormal movements in multiple body regions, triggered by emotional stress or infections. Dyskinetic crises may lead to functional impairment and complications, emphasizing the need for prompt recognition. While individualized pharmacological recommendations were not provided, benzodiazepines and clonidine were suggested for acute crisis management. Chronic treatment options included tetrabenazine, benzodiazepines, gabapentin, and clonidine. Deep brain stimulation should be considered early in the treatment of refractory or prolonged dyskinetic crisis.

Conclusion

This consensus provides a foundation for understanding and managing dyskinetic crises in GNAO1-RD for clinicians, caregivers, and researchers. The study emphasizes the importance of targeted parental and caregiver education, which enables early recognition and intervention, thereby potentially minimizing both short- and long-term complications. Future research should concentrate on differentiating dyskinetic crises from other neurological events and investigating potential risk factors that influence their occurrence and nature. The proposed standardized framework improves clinical management, stakeholder communication, and future GNAO1-RD research.

Epilepsies

Recent advances in genetic diagnosis have revealed the underlying etiology of many epilepsies and have identified pathogenic, causative variants in numerous ion and ligand-gated channel genes. This chapter describes the clinical presentations of epilepsy associated with different channelopathies including classic electroclinical syndromes and emerging gene-specific phenotypes. Also discussed are the archetypal epilepsy channelopathy, SCN1A-Dravet syndrome, considering the expanding phenotype. Clinical presentations where a channelopathy is suspected, such as sleep-related hypermotor epilepsy and epilepsy in association with movement disorders, are reviewed. Channelopathies pose an intriguing problem for the development of gene therapies. Design of targeted therapies requires physiologic insights into the often multifaceted impact of a pathogenic variant, coupled with an understanding of the phenotypic spectrum of a gene. As gene-specific novel therapies come online for the channelopathies, it is essential that clinicians are able to recognize epilepsy phenotypes likely to be due to channelopathy and institute early genetic testing in both children and adults. These findings are likely to have immediate management implications and to inform prognostic and reproductive counseling.

Diverse WGBS profiles of longissimus dorsi muscle in Hainan black goats and hybrid goats

BACKGROUND

Goat products have played a crucial role in meeting the dietary demands of people since the Neolithic era, giving rise to a multitude of goat breeds globally with varying characteristics and meat qualities. The primary objective of this study is to pinpoint the pivotal genes and their functions responsible for regulating muscle fiber growth in the longissimus dorsi muscle (LDM) through DNA methylation modifications in Hainan black goats and hybrid goats.

METHODS

Whole-genome bisulfite sequencing (WGBS) was employed to scrutinize the impact of methylation on LDM growth. This was accomplished by comparing methylation differences, gene expression, and their associations with growth-related traits.

RESULTS

In this study, we identified a total of 3,269 genes from differentially methylated regions (DMR), and detected 189 differentially expressed genes (DEGs) through RNA-seq analysis. Hypo DMR genes were primarily enriched in KEGG terms associated with muscle development, such as MAPK and PI3K-Akt signaling pathways. We selected 11 hub genes from the network that intersected the gene sets within DMR and DEGs, and nine genes exhibited significant correlation with one or more of the three LDM growth traits, namely area, height, and weight of loin eye muscle. Particularly, PRKG1 demonstrated a negative correlation with all three traits. The top five most crucial genes played vital roles in muscle fiber growth: FOXO3 safeguarded the myofiber's immune environment, FOXO6 was involved in myotube development and differentiation, and PRKG1 facilitated vasodilatation to release more glucose. This, in turn, accelerated the transfer of glucose from blood vessels to myofibers, regulated by ADCY5 and AKT2, ultimately ensuring glycogen storage and energy provision in muscle fibers.

CONCLUSION

This study delved into the diverse methylation modifications affecting critical genes, which collectively contribute to the maintenance of glycogen storage around myofibers, ultimately supporting muscle fiber growth.

Movement Disorders in Patients With Genetic Developmental and Epileptic Encephalopathies

BACKGROUND AND OBJECTIVES

Movement disorders (MDs) are underrecognized in the developmental and epileptic encephalopathies (DEEs). There are now more than 800 genes implicated in causing the DEEs; relatively few of these rare genetic diseases are known to be associated with MDs. We identified patients with genetic DEEs who had MDs, classified the nature of their MDs, and asked whether specific patterns correlated with the underlying mechanism.

METHODS

We classified the type of MDs associated with specific genetic DEEs in a large international cohort of patients and analyzed whether specific patterns of MDs reflected the underlying biological dysfunction.

RESULTS

Our cohort comprised 77 patients with a genetic DEE with a median age of 9 (range 1-38) years. Stereotypies (37/77, 48%) and dystonia (34/77, 44%) were the most frequent MDs, followed by chorea (18/77, 23%), myoclonus (14/77, 18%), ataxia (9/77, 12%), tremor (7/77, 9%), and hypokinesia (6/77, 8%). In 47% of patients, a combination of MDs was seen. The MDs were first observed at a median age of 18 months (range day 2-35 years). Dystonia was more likely to be observed in nonambulatory patients, while ataxia was less likely. In 46% of patients, therapy was initiated with medication (34/77, 44%), deep brain stimulation (1/77, 1%), or intrathecal baclofen (1/77, 1%). We found that patients with channelopathies or synaptic vesicle trafficking defects were more likely to experience dystonia; whereas, stereotypies were most frequent in individuals with transcriptional defects.

DISCUSSION

MDs are often underrecognized in patients with genetic DEEs, but recognition is critical for the management of these complex neurologic diseases. Distinguishing MDs from epileptic seizures is important in tailoring patient treatment. Understanding which MDs occur with different biological mechanisms will inform early diagnosis and management.

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.

GNAO1-related neurodevelopmental disorder: Literature review and caregiver survey

Background

GNAO1-related neurodevelopmental disorder is a heterogeneous condition characterized by hypotonia, developmental delay, epilepsy, and movement disorder. This study aims to better understand the spectrum of epilepsy associated with GNAO1 variants and experience with anti-seizure medications, and to review published epilepsy phenotypes in GNAO1.

Methods

An online survey was distributed to caregivers of individuals diagnosed with GNAO1 pathogenic variants, and a literature review was conducted.

Results

Fifteen respondents completed the survey with the median age of 39 months, including a novel variant p.Q52P. Nine had epilepsy - six had onset in the first week of life, three in the first year of life - but two reported no ongoing seizures. Seizure types varied. Individuals were taking a median of 3 seizure medications without a single best treatment. Our cohort was compared to a literature review of epilepsy in GNAO1. In 86 cases, 38 discrete variants were described; epilepsy is reported in 53 % cases, and a developmental and epileptic encephalopathy in 36 %.

Conclusions

While GNAO1-related epilepsy is most often early-onset and severe, seizures may not always be drug resistant or lifelong. Experience with anti-seizure medications is varied. Certain variant "hotspots" may correlate with epilepsy phenotype though genotype-phenotype correlation is poorly understood.

Genetic overlap between dystonia and other neurologic disorders: A study of 1,100 exomes

INTRODUCTION

Although shared genetic factors have been previously reported between dystonia and other neurologic conditions, no sequencing study exploring such links is available. In a large dystonic cohort, we aimed at analyzing the proportions of causative variants in genes associated with disease categories other than dystonia.

METHODS

Gene findings related to whole-exome sequencing-derived diagnoses in 1100 dystonia index cases were compared with expert-curated molecular testing panels for ataxia, parkinsonism, spastic paraplegia, neuropathy, epilepsy, and intellectual disability.

RESULTS

Among 220 diagnosed patients, 21% had variants in ataxia-linked genes; 15% in parkinsonism-linked genes; 15% in spastic-paraplegia-linked genes; 12% in neuropathy-linked genes; 32% in epilepsy-linked genes; and 65% in intellectual-disability-linked genes. Most diagnosed presentations (80%) were related to genes listed in ≥1 studied panel; 71% of the involved loci were found in the non-dystonia panels but not in an expert-curated gene list for dystonia.

CONCLUSIONS

Our study indicates a convergence in the genetics of dystonia and other neurologic phenotypes, informing diagnostic evaluation strategies and pathophysiological considerations.

Pediatric Encephalopathy: Clinical, Biochemical and Cellular Insights into the Role of Gln52 of GNAO1 and GNAI1 for the Dominant Disease

Heterotrimeric G proteins are immediate transducers of G protein-coupled receptors-the biggest receptor family in metazoans-and play innumerate functions in health and disease. A set of de novo point mutations in GNAO1 and GNAI1, the genes encoding the α-subunits (Gαo and Gαi1, respectively) of the heterotrimeric G proteins, have been described to cause pediatric encephalopathies represented by epileptic seizures, movement disorders, developmental delay, intellectual disability, and signs of neurodegeneration. Among such mutations, the Gln52Pro substitutions have been previously identified in GNAO1 and GNAI1. Here, we describe the case of an infant with another mutation in the same site, Gln52Arg. The patient manifested epileptic and movement disorders and a developmental delay, at the onset of 1.5 weeks after birth. We have analyzed biochemical and cellular properties of the three types of dominant pathogenic mutants in the Gln52 position described so far: Gαo[Gln52Pro], Gαi1[Gln52Pro], and the novel Gαo[Gln52Arg]. At the biochemical level, the three mutant proteins are deficient in binding and hydrolyzing GTP, which is the fundamental function of the healthy G proteins. At the cellular level, the mutants are defective in the interaction with partner proteins recognizing either the GDP-loaded or the GTP-loaded forms of Gαo. Further, of the two intracellular sites of Gαo localization, plasma membrane and Golgi, the former is strongly reduced for the mutant proteins. We conclude that the point mutations at Gln52 inactivate the Gαo and Gαi1 proteins leading to aberrant intracellular localization and partner protein interactions. These features likely lie at the core of the molecular etiology of pediatric encephalopathies associated with the codon 52 mutations in GNAO1/GNAI1.