Cortical myoclonus and epilepsy in a family with a new SLC20A2 mutation

Hippocampal transcriptome analysis in ClockΔ19 mice identifies pathways associated with glial cell differentiation and myelination

BACKGROUND

ClockΔ19 mice demonstrate behavioral characteristics and neurobiological changes that closely resemble those observed in bipolar disorder (BD). Notably, abnormalities in the hippocampus have been observed in patients with BD, yet direct molecular investigation of human hippocampal tissue remains challenging due to its limited accessibility.

METHODS

To model BD, ClockΔ19 mice were employed. Weighted gene co-expression network analysis (WGCNA) was utilized to identify mutation-related modules, and changes in cell populations were determined using the computational deconvolution CIBERSORTx. Furthermore, GeneMANIA and protein-protein interactions (PPIs) were leveraged to construct a comprehensive interaction network.

RESULTS

174 differentially expressed genes (DEGs) were identified, revealing abnormalities in rhythmic processes, mitochondrial metabolism, and various cell functions including morphology, differentiation, and receptor activity. Analysis identified 5 modules correlated with the mutation, with functional enrichment highlighting disturbances in rhythmic processes and neural cell differentiation due to the mutation. Furthermore, a decrease in neural stem cells (NSC), and an increase in astrocyte-restricted precursors (ARP), ependymocytes (EPC), and hemoglobin-expressing vascular cells (Hb-VC) in the mutant mice were observed. A network comprising 12 genes that link rhythmic processes to neural cell differentiation in the hippocampus was also identified.

LIMITATIONS

This study focused on the hippocampus of mice, hence the applicability of these findings to human patients warrants further exploration.

CONCLUSION

The ClockΔ19 mutation may disrupt circadian rhythm, myelination, and the differentiation of neural stem cells (NSCs) into glial cells. These abnormalities are linked to altered expression of key genes, including DPB, CIART, NR1D1, GFAP, SLC20A2, and KL. Furthermore, interactions between SLC20A2 and KL might provide a connection between circadian rhythm regulation and cell type transitions.

Unveiling distinct clinical manifestations of primary familial brain calcifications in Asian and European patients: A study based on 10-year individual-level data

BACKGROUND

Primary Familial Brain Calcification (PFBC) can manifest clinically with a complex and heterogeneous array of symptoms, including parkinsonism, dysarthria, and cognitive impairment. However, the distinct presentations of PFBC in Asian and European populations remain unclear.

METHODS

We conducted a systematic search of PubMed for studies involving genetically confirmed PFBC patients. Demographic data, genetic information, radiological examinations, and clinical characteristics were extracted for each case.

RESULTS

The study included 120 publications and 564 genetically confirmed PFBC patients. Asian and European PFBC populations represented 54 % and 37 % of global patients, respectively. While calcification patterns showed no significant differences between Asian and European PFBC patients, European autosomal dominant PFBC variant carriers were more likely to exhibit clinical symptoms compared to their Asian counterparts (OR = 2.90, 95 % CI 1.55-5.60) and had an earlier estimated age of onset (median age 42 vs 58).

CONCLUSION

The interaction between regional differences and genetically determined calcification severity may collectively influence PFBC symptom progression. Future research should further explore the potential roles of gene modifiers, ethnic background, socioeconomic and environmental exposure factors underlying regional differences in PFBC progression.

Migraine With Aura Accompanied by Myoclonus: A Case Report

Migraine is a condition characterized by pulsating headaches, often accompanied by photophobia, phonophobia, and/or gastrointestinal symptoms such as nausea and vomiting. Approximately 15% to one-third of migraine patients experience an aura either before or during the headache. To the best of our knowledge, the occurrence of migraine with myoclonus is extremely rare. This report describes a rare case of migraine with aura accompanied by myoclonus. The patient is a 46-year-old man who developed a visual aura followed by vomiting and a throbbing headache on the right side. As the headache intensified, involuntary movements of the left lower extremity appeared. Brain magnetic resonance imaging (MRI) revealed no structural abnormalities or stroke lesions; however, arterial spin labeling MRI showed hypoperfusion in the right cerebral hemisphere. An ophthalmological evaluation was unremarkable. He was diagnosed with migraine with myoclonus, and the intravenous administration of diazepam and sumatriptan resulted in the cessation of the myoclonus and mild relief of the headache. By the day after admission, the myoclonus and visual symptoms had completely disappeared. The headache resolved by the third day of admission.

The Genetics of Primary Familial Brain Calcification: A Literature Review

Primary familial brain calcification (PFBC), also known as Fahr's disease, is a rare inherited disorder characterized by bilateral calcification in the basal ganglia according to neuroimaging. Other brain regions, such as the thalamus, cerebellum, and subcortical white matter, can also be affected. Among the diverse clinical phenotypes, the most common manifestations are movement disorders, cognitive deficits, and psychiatric disturbances. Although patients with PFBC always exhibit brain calcification, nearly one-third of cases remain clinically asymptomatic. Due to advances in the genetics of PFBC, the diagnostic criteria of PFBC may need to be modified. Hitherto, seven genes have been associated with PFBC, including four dominant inherited genes (SLC20A2, PDGFRB, PDGFB, and XPR1) and three recessive inherited genes (MYORG, JAM2, and CMPK2). Nevertheless, around 50% of patients with PFBC do not have pathogenic variants in these genes, and further PFBC-associated genes are waiting to be identified. The function of currently known genes suggests that PFBC could be caused by the dysfunction of the neurovascular unit, the dysregulation of phosphate homeostasis, or mitochondrial dysfunction. An improved understanding of the underlying pathogenic mechanisms for PFBC may facilitate the development of novel therapies.

Brain Calcifications: Genetic, Molecular, and Clinical Aspects

Many conditions can present with accumulation of calcium in the brain and manifest with a variety of neurological symptoms. Brain calcifications can be primary (idiopathic or genetic) or secondary to various pathological conditions (e.g., calcium-phosphate metabolism derangement, autoimmune disorders and infections, among others). A set of causative genes associated with primary familial brain calcification (PFBC) has now been identified, and include genes such as SLC20A2, PDGFB, PDGFRB, XPR1, MYORG, and JAM2. However, many more genes are known to be linked with complex syndromes characterized by brain calcifications and additional neurologic and systemic manifestations. Of note, many of these genes encode for proteins involved in cerebrovascular and blood-brain barrier functions, which both represent key anatomical structures related to these pathological phenomena. As a growing number of genes associated with brain calcifications is identified, pathways involved in these conditions are beginning to be understood. Our comprehensive review of the genetic, molecular, and clinical aspects of brain calcifications offers a framework for clinicians and researchers in the field.

Autosomal dominant hypocalcemia type 1 (ADH1) associated with myoclonus and intracerebral calcifications

Autosomal dominant hypocalcemia type 1 (ADH1) is a disorder of extracellular calcium homeostasis caused by germline gain-of-function mutations of the calcium-sensing receptor (CaSR). Over 35% of ADH1 patients have intracerebral calcifications predominantly affecting the basal ganglia. The clinical consequences of such calcifications remain to be fully characterized, although the majority of patients with these calcifications are considered to be asymptomatic. We report a 20-year-old female proband with a severe form of ADH1 associated with recurrent hypocalcemic and hypercalcemic episodes, persistent childhood hyperphosphatemia, and a low calcium/phosphate ratio. From the age of 18 years, she had experienced recurrent myoclonic jerks affecting the upper limbs that were not associated with epileptic seizures, extra-pyramidal features, cognitive impairment, or alterations in serum calcium concentrations. Computerised tomography (CT) scans revealed calcifications of the globus pallidus regions of the basal ganglia bilaterally, and also the frontal lobes at the grey-white matter junction, and posterior horn choroid plexuses. The patient’s myoclonus resolved following treatment with levetiracetam. CASR mutational analysis identified a reported germline gain-of-function heterozygous missense mutation, c.2363T>G; p.(Phe788Cys), which affects an evolutionarily conserved phenylalanine residue located in transmembrane domain helix 5 of the CaSR protein. Analysis of the cryo-electron microscopy CaSR structure predicted the wild-type Phe788 residue to form interactions with neighbouring phenylalanine residues, which likely maintain the CaSR in an inactive state. The p.(Phe788Cys) mutation was predicted to disrupt these interactions, thereby leading to CaSR activation. These findings reveal myoclonus as a novel finding in an ADH1 patient with intracerebral calcifications.