Exploring the Biological Overlapping Between Brain Calcifications and Tumorgenesis.

This article discusses a rare case of coexistent meningiomas and Primary familial brain calcification (PFBC). PFBC is a neurodegenerative disease characterized by brain calcifications and a variety of neuropsychiatric symptoms and signs, with pathogenic variants in specific genes. The study explores the potential link between PFBC and meningiomas, highlighting shared features like intralesional calcifications and common genes such as MEA6. The article also revisits PFBC patients developing other brain tumors, particularly gliomas, emphasizing the intersection of oncogenes like PDGFB and PDGFRB in both calcifications and tumor progression. In recent investigations, attention has extended beyond brain tumors to breast cancer metastasis, unveiling a noteworthy connection. These findings suggest a broader connection between brain calcifications and tumors, encouraging a reevaluation of therapeutic approaches for PFBC.

Novel findings in a Swedish primary familial brain calcification cohort.

INTRODUCTION: Brain calcifications are frequent findings on imaging. In a small proportion of cases, these calcifications are associated with pathogenic gene variants, hence termed primary familial brain calcification (PFBC). The clinical penetrance is incomplete and phenotypic variability is substantial. This paper aims to characterize a Swedish PFBC cohort including 25 patients: 20 from seven families and five sporadic cases. METHODS: Longitudinal clinical assessment and CT imaging were conducted, abnormalities were assessed using the total calcification score (TCS). Genetic analyses, including a panel of six known PFBC genes, were performed in all index and sporadic cases. Additionally, three patients carrying a novel pathogenic copy number variant in SLC20A2 had their cerebrospinal fluid phosphate (CSF-Pi) levels measured. RESULTS: Among the 25 patients, the majority (76%) displayed varying symptoms during the initial assessment including motor (60%), psychiatric (40%), and/or cognitive abnormalities (24%). Clinical progression was observed in most patients (78.6%), but there was no significant difference in calcification between the first and second scans, with mean scores of 27.3 and 32.8, respectively. In three families and two sporadic cases, pathogenic genetic variants were identified, including a novel finding, in the SLC20A2 gene. In the three tested patients, the CSF-Pi levels were normal. CONCLUSIONS: This report demonstrates the variable expressivity seen in PFBC and includes a novel pathogenic variant in the SLC20A2 gene. In four families and three sporadic cases, no pathogenic variants were found, suggesting that new PFBC genes remain to be discovered.

Biallelic NAA60 variants with impaired n-terminal acetylation capacity cause autosomal recessive primary familial brain calcifications.

Primary familial brain calcification (PFBC) is characterized by calcium deposition in the brain, causing progressive movement disorders, psychiatric symptoms, and cognitive decline. PFBC is a heterogeneous disorder currently linked to variants in six different genes, but most patients remain genetically undiagnosed. Here, we identify biallelic NAA60 variants in ten individuals from seven families with autosomal recessive PFBC. The NAA60 variants lead to loss-of-function with lack of protein N-terminal (Nt)-acetylation activity. We show that the phosphate importer SLC20A2 is a substrate of NAA60 in vitro. In cells, loss of NAA60 caused reduced surface levels of SLC20A2 and a reduction in extracellular phosphate uptake. This study establishes NAA60 as a causal gene for PFBC, provides a possible biochemical explanation of its disease-causing mechanisms and underscores NAA60-mediated Nt-acetylation of transmembrane proteins as a fundamental process for healthy neurobiological functioning.

RNA Interference Effectors Selectively Silence the Pathogenic Variant GNAO1 c.607 G > A In Vitro.

RNA interference (RNAi)-based therapeutics hold the potential for dominant genetic disorders, enabling sequence-specific inhibition of pathogenic gene products. We aimed to direct RNAi for the selective suppression of the heterozygous GNAO1 c.607 G > A variant causing GNAO1 encephalopathy. By screening short interfering RNA (siRNA), we showed that GNAO1 c.607G>A is a druggable target for RNAi. The si1488 candidate achieved at least twofold allelic discrimination and downregulated mutant protein to 35%. We created vectorized RNAi by incorporating the si1488 sequence into the short hairpin RNA (shRNA) in the adeno-associated virus (AAV) vector. The shRNA stem and loop were modified to improve the transcription, processing, and guide strand selection. All tested shRNA constructs demonstrated selectivity toward mutant GNAO1, while tweaking hairpin structure only marginally affected the silencing efficiency. The selectivity of shRNA-mediated silencing was confirmed in the context of AAV vector transduction. To conclude, RNAi effectors ranging from siRNA to AAV-RNAi achieve suppression of the pathogenic GNAO1 c.607G>A and discriminate alleles by the single-nucleotide substitution. For gene therapy development, it is crucial to demonstrate the benefit of these RNAi effectors in patient-specific neurons and animal models of the GNAO1 encephalopathy.

Small vessel disease in primary familial brain calcification with novel truncating PDGFB variants.

INTRODUCTION: Primary familial brain calcification (PFBC) is a neurodegenerative disease characterised by bilateral calcification in the brain, especially in the basal ganglia, leading to neurological and neuropsychiatric manifestations. White matter hyperintensities (WMH) have been described in patients with PFBC and pathogenic variants in the gene for platelet-derived growth factor beta polypeptide (PDGFB), suggesting a manifest cerebrovascular process. We present below the cases of two PFBC families with PDGFB variants and stroke or transient ischaemic attack (TIA) episodes. We examine the possible correlation between PFBC and vascular events as stroke/TIA, and evaluate whether signs for vascular disease in this condition are systemic or limited to the cerebral vessels. MATERIAL AND METHODS: Two Swedish families with novel truncating PDGFB variants, p.Gln140* and p.Arg191*, are described clinically and radiologically. Subcutaneous capillary vessels in affected and unaffected family members were examined by light and electron microscopy. RESULTS: All mutation carriers showed WMH and bilateral brain calcifications. The clinical presentations differed, with movement disorder symptoms dominating in family A, and psychiatric symptoms in family B. However, affected members of both families had stroke, TIA, and/or asymptomatic intracerebral ischaemic lesions. Only one of the patients had classical vascular risk factors. Skin microvasculature was normal. CONCLUSIONS: Patients with these PDGFB variants develop microvascular changes in the brain, but not the skin. PDGFB-related small vessel disease can manifest radiologically as cerebral haemorrhage or ischaemia, and may explain TIA or stroke in patients without other vascular risk factors.

THE PREVALENCE OF C3953T IL1Β GENE AND G308A TNFΑ GENE POLYMORPHIC VARIANTS IN THE PATIENTS WITH DIFFERENT TYPES OF ENCEPHALOPATHIES.

It is essential to study disorders of the immune system in chronic encephalopathies of various genesis, considering that the mechanisms of brain damage remain unknown in their molecular basis. Among numerous inflammatory mediators, cytokines are particular in regulating immunological interactions. Many factors, including the genetic ones, determine these pro-inflammatory proteins' activity. The aim of study was to study the prevalence of IL1ß C3953T gene polymorphism and TNFα G308A gene polymorphism in patients with chronic traumatic encephalopathy (CTE), microvascular ischemic disease of the brain (or cerebral small vessel disease, (SVD)), chronic alcohol-induced encephalopathy (AIE) and postinfectious encephalopathy (PIE), and to evaluate the impact of a particular genotype presence on the occurrence and/or progression of encephalopathy. The molecular genetic study of polymorphic variants - C3953T of the IL1ß gene and G308A of the TNFα gene was applied for 96 patients with encephalopathies of various genesis (CTE n=26, CAIE n=26, SVD n=18, and PIE n=26). The patients were undergoing treatment in the neurological departments of the Communal Non-commercial Enterprise "Ternopil Regional Clinical Psychoneurological Hospital" of Ternopil Regional Council (Ternopil, Ukraine) during 2021-2022. The control group consisted of 12 healthy persons, who were representative in terms of age and sex. Statistical processing of the results was carried out using the STATISTICA 10.0 software package. The frequency distribution analysis of the genotypes of the polymorphic variant C3953T of the IL1ß gene and G308A of the TNFα gene in patients with CTE, SVD, CAIE, and PIE compared to individuals of the control group was performed. The statistically significant differences were found only in patients with PIE: 26.92% vs. 83.33% - carriers of the C/ C genotype, 61.54% versus 16.67% - carriers of the C/T genotype and 11.54% versus 0% - carriers of the T/T genotype and 53.85% versus 91.67% - carriers of the G/G genotype, 46 .15% versus 8.33% - carriers of the G/A genotype and 0.0% versus 0.0% - carriers of the A/A genotype, respectively. In addition, in the group of patients with PIE, the distribution of genotype frequencies of the polymorphic variant C3953T of the IL1ß gene probably differed from the data of patients with CTE, SVD, and PIE (χ2=28.64; p<0.001), and in the group of patients with CAIE, the distribution of genotype frequencies of the polymorphic variant G308A of the TNFα gene probably differed from the data of patients with SVD and PIE (χ2=24.91; p=0.002). Analyzing the odds ratio and its confidence interval for the genotypes of polymorphic variants C3953T of the IL1ß gene and G308A of the TNFα gene in patients with CTE, SVD, CAIE, and PIE, it was established that the presence of the C/T genotype of the IL1ß gene increases the risk of encephalopathy in patients with PIE by 8.0 times, and the presence of the G/A genotype of the TNFα gene increases the risk of encephalopathy in patients with PIE by 9.4 times. For the first time in the Ukrainian population, an analysis of the frequency distribution of the genotypes of the polymorphic variant C3953T of the IL1ß gene and G308A of the TNFα gene in patients with chronic encephalopathies of various genesis was performed. Statistically, significant differences were found only in patients with PIE compared to healthy individuals. At the same time, the presence of the C/T genotype of the IL1ß gene increases the risk of the occurrence and/or progression of PIE by 8.0 times, and the presence of the G/A genotype of the TNFα gene by 9.4 times, which indicates the feasibility of including the corresponding single-nucleotide polymorphisms in the genetic panel of the study patients with PIE.

Generation and characterization of human induced pluripotent stem cell line METUi002-A from a patient with primary familial brain calcification (PFBC) carrying a heterozygous mutation (c.687dupT (p.Val230CysfsTer28)) in the SLC20A2 gene.

Primary familial brain calcification (PFBC) is a rare neurological condition characterized by abnormal calcification commonly in basal ganglia and multiple other brain regions, leading to neuropsychiatric, cognitive, and motor symptoms. SLC20A2, one of the known causative genes for PFBC, contains the highest number of variants directly associated with the disease. Here, we established an iPSC line (METUi002-A) from the peripheral blood mononuclear cells of a clinically diagnosed PFBC patient carrying a SLC20A2 mutation (c.687dupT) using the integration-free Sendai reprogramming. METUi002-A can serve as a valuable tool to generate cellular models to investigate the mechanistic effects of this mutation in PFBC.

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.

Infantile-onset parkinsonism, dyskinesia, and developmental delay: do not forget polyglutamine defects!

We present the phenotype of an infant with the largest ATN1 CAG expansion reported to date (98 repeats). He presented at 4 months with developmental delay, poor eye contact, acquired microcephaly, failure to thrive. He progressively developed dystonia-parkinsonism with paroxysmal oromandibular and limbs dyskinesia and fatal outcome at 17 months. Cerebral MRI disclosed globus pallidus T2-WI hyperintensities and brain atrophy. Molecular analysis was performed post-mortem following the diagnosis of dentatorubral-pallidoluysian atrophy (DRPLA) in his symptomatic father. Polyglutamine expansion defects should be considered when neurodegenerative genetic disease is suspected even in infancy and parkinsonism can be a presentation of infantile-onset DRPLA.

Familial hemophagocytic phohistiocytosis induced by PRF1 mutation with neurologic manifestations as the initial clinical presentations: A case report.

BACKGROUND: To investigate the clinical characteristics of familial hemophagocytic phohistiocytosis (FHL) induced by PRF1 gene mutation and with central nervous injury as the initial presentation. CASE PRESENTATION: Herein, we presented 2 cases of a familial hemophagocytic syndrome caused by PRF1 gene mutation in 1 family with central nervous injury as the first symptom and searched relevant literature for clinical analysis of its pathogenic characteristics. Two children from 1 family were included in this study, both of whom had complex heterozygous mutations of C. 1189_1190dupTG (p.H398Afs*23) and C. 394G>A (p.G132R). Literature search further revealed 20 cases of PRF1 gene mutation-induced familial FHL with central nervous injury as the initial presentation. The main neurological symptoms included cranial nerve injury (81.8%), convulsion (77.3%), ataxia (63.6%), encephalopathy (59.1%), and limb paralysis (40.9%). Cranial imaging findings were dominated by the cerebral hemisphere (100%), cerebellar hemisphere (85%), brainstem (55%), and periventricular white matter (40%), and 73.7% of cases had elevated white blood cell count in CSF. Most cases were confirmed by differential diagnosis and gene sequencing, which suggested that C. 673C>T (P.r225W), C. 394G>A (P.G132r), C. 666C>A (p.H222Q), C. 1349C>T (p.T450M), C. 1349C>T (p.T450M), and C. 443C>C (p.A148G) could be focal mutations of this disease. CONCLUSION: Lesions involving the cerebellum and brainstem in children with ataxia and cranial nerve damage could be indicative of primary FHL; thus, the inherent immune test and gene test should be timely performed to help confirm the diagnosis, guide the treatment, and improve the prognosis.

Association of deep phenotyping with diagnostic yield of prenatal exome sequencing for fetal brain abnormalities.

PURPOSE: To evaluate whether deep prenatal phenotyping of fetal brain abnormalities (FBAs) increases diagnostic yield of trio-exome sequencing (ES) compared with standard phenotyping. METHODS: Retrospective exploratory analysis of a multicenter prenatal ES study. Participants were eligible if an FBA was diagnosed and subsequently found to have a normal microarray. Deep phenotyping was defined as phenotype based on targeted ultrasound plus prenatal/postnatal magnetic resonance imaging, autopsy, and/or known phenotypes of other affected family members. Standard phenotyping was based on targeted ultrasound alone. FBAs were categorized by major brain findings on prenatal ultrasound. Cases with positive ES results were compared with those that have negative results by available phenotyping, as well as diagnosed FBAs. RESULTS: A total of 76 trios with FBAs were identified, of which 25 (33%) cases had positive ES results and 51 (67%) had negative results. Individual modalities of deep phenotyping were not associated with diagnostic ES results. The most common FBAs identified were posterior fossa anomalies and midline defects. Neural tube defects were significantly associated with receipt of a negative ES result (0% vs 22%, P = .01). CONCLUSION: Deep phenotyping was not associated with increased diagnostic yield of ES for FBA in this small cohort. Neural tube defects were associated with negative ES results.

RNASEH2C c.194G>A is a Chinese-specific founder mutation in three unrelated patients with Aicardi-Goutières syndrome 3.

Biallelic pathogenic variants in RNASEH2C cause Aicardi-Goutières syndrome 3 (AGS3, MIM #610329), a rare early-onset encephalopathy characterized by intermittent unexplained fever, chilblains, irritability, progressive microcephaly, dystonia, spasticity, severe psychomotor retardation and abnormal brain imaging. Currently, approximately 50 individuals with AGS3 and 19 variants in RNASEH2C have been revealed. Here, we reported the novel clinical manifestations and genotypic information of three unrelated Chinese patients with AGS3 caused by pathogenic variants in RNASEH2C. In addition to three novel missense variants (c.101G>A, p.Cys34Tyr; c.401T>A, p.Leu134Gln and c.434G>T, p.Arg145Leu), one missense variant (c.194G>A, p.Gly65Asp) reoccurred in all patients but was completely absent in South Asian and other ethnicities. Our study expanded the variant spectrum of RNASEH2C and identified RNASEH2C c.194G>A as a Chinese-specific founder mutation. The novel phenotypes, including mouth ulcers, hip dysplasia, retarded dentition and hypogonadism, observed in our patients greatly enriched the clinical characteristics of AGS3.

A comparison of anatomic and cellular transcriptome structures across 40 human brain diseases.

Genes associated with risk for brain disease exhibit characteristic expression patterns that reflect both anatomical and cell type relationships. Brain-wide transcriptomic patterns of disease risk genes provide a molecular-based signature, based on differential co-expression, that is often unique to that disease. Brain diseases can be compared and aggregated based on the similarity of their signatures which often associates diseases from diverse phenotypic classes. Analysis of 40 common human brain diseases identifies 5 major transcriptional patterns, representing tumor-related, neurodegenerative, psychiatric and substance abuse, and 2 mixed groups of diseases affecting basal ganglia and hypothalamus. Further, for diseases with enriched expression in cortex, single-nucleus data in the middle temporal gyrus (MTG) exhibits a cell type expression gradient separating neurodegenerative, psychiatric, and substance abuse diseases, with unique excitatory cell type expression differentiating psychiatric diseases. Through mapping of homologous cell types between mouse and human, most disease risk genes are found to act in common cell types, while having species-specific expression in those types and preserving similar phenotypic classification within species. These results describe structural and cellular transcriptomic relationships of disease risk genes in the adult brain and provide a molecular-based strategy for classifying and comparing diseases, potentially identifying novel disease relationships.

An Update of Epigenetic Drugs for the Treatment of Cancers and Brain Diseases: A Comprehensive Review.

Epigenetics has long been recognized as a significant field in biology and is defined as the investigation of any alteration in gene expression patterns that is not attributed to changes in the DNA sequences. Epigenetic marks, including histone modifications, non-coding RNAs, and DNA methylation, play crucial roles in gene regulation. Numerous studies in humans have been carried out on single-nucleotide resolution of DNA methylation, the CpG island, new histone modifications, and genome-wide nucleosome positioning. These studies indicate that epigenetic mutations and aberrant placement of these epigenetic marks play a critical role in causing the disease. Consequently, significant development has occurred in biomedical research in identifying epigenetic mechanisms, their interactions, and changes in health and disease conditions. The purpose of this review article is to provide comprehensive information about the different types of diseases caused by alterations in epigenetic factors such as DNA methylation and histone acetylation or methylation. Recent studies reported that epigenetics could influence the evolution of human cancer via aberrant methylation of gene promoter regions, which is associated with reduced gene function. Furthermore, DNA methyltransferases (DNMTs) in the DNA methylation process as well as histone acetyltransferases (HATs)/histone deacetylases (HDACs) and histone methyltransferases (HMTs)/demethylases (HDMs) in histone modifications play important roles both in the catalysis and inhibition of target gene transcription and in many other DNA processes such as repair, replication, and recombination. Dysfunction in these enzymes leads to epigenetic disorders and, as a result, various diseases such as cancers and brain diseases. Consequently, the knowledge of how to modify aberrant DNA methylation as well as aberrant histone acetylation or methylation via inhibitors by using epigenetic drugs can be a suitable therapeutic approach for a number of diseases. Using the synergistic effects of DNA methylation and histone modification inhibitors, it is hoped that many epigenetic defects will be treated in the future. Numerous studies have demonstrated a link between epigenetic marks and their effects on brain and cancer diseases. Designing appropriate drugs could provide novel strategies for the management of these diseases in the near future.

The clinical and genetic spectrum of primary familial brain calcification.

Primary familial brain calcification (PFBC), formerly known as Fahr's disease, is a rare neurodegenerative disease characterized by bilateral progressive calcification of the microvessels of the basal ganglia and other cerebral and cerebellar structures. PFBC is thought to be due to an altered function of the Neurovascular Unit (NVU), where abnormal calcium-phosphorus metabolism, functional and microanatomical alterations of pericytes and mitochondrial alterations cause a dysfunction of the blood-brain barrier (BBB) and the generation of an osteogenic environment with surrounding astrocyte activation and progressive neurodegeneration. Seven causative genes have been discovered so far, of which four with dominant (SLC20A2, PDGFB, PDGFRB, XPR1) and three with recessive inheritance (MYORG, JAM2, CMPK2). Clinical presentation ranges from asymptomatic subjects to movement disorders, cognitive decline and psychiatric disturbances alone or in various combinations. Radiological patterns of calcium deposition are similar in all known genetic forms, but central pontine calcification and cerebellar atrophy are highly suggestive of MYORG mutations and extensive cortical calcification has been associated with JAM2 mutations. Currently, no disease-modifying drugs or calcium-chelating agents are available and only symptomatic treatments can be offered.

WWOX developmental and epileptic encephalopathy: Understanding the epileptology and the mortality risk.

OBJECTIVE: WWOX is an autosomal recessive cause of early infantile developmental and epileptic encephalopathy (WWOX-DEE), also known as WOREE (WWOX-related epileptic encephalopathy). We analyzed the epileptology and imaging features of WWOX-DEE, and investigated genotype-phenotype correlations, particularly with regard to survival. METHODS: We studied 13 patients from 12 families with WWOX-DEE. Information regarding seizure semiology, comorbidities, facial dysmorphisms, and disease outcome were collected. Electroencephalographic (EEG) and brain magnetic resonance imaging (MRI) data were analyzed. Pathogenic WWOX variants from our cohort and the literature were coded as either null or missense, allowing individuals to be classified into one of three genotype classes: (1) null/null, (2) null/missense, (3) missense/missense. Differences in survival outcome were estimated using the Kaplan-Meier method. RESULTS: All patients experienced multiple seizure types (median onset = 5 weeks, range = 1 day-10 months), the most frequent being focal (85%), epileptic spasms (77%), and tonic seizures (69%). Ictal EEG recordings in six of 13 patients showed tonic (n = 5), myoclonic (n = 2), epileptic spasms (n = 2), focal (n = 1), and migrating focal (n = 1) seizures. Interictal EEGs demonstrated slow background activity with multifocal discharges, predominantly over frontal or temporo-occipital regions. Eleven of 13 patients had a movement disorder, most frequently dystonia. Brain MRIs revealed severe frontotemporal, hippocampal, and optic atrophy, thin corpus callosum, and white matter signal abnormalities. Pathogenic variants were located throughout WWOX and comprised both missense and null changes including five copy number variants (four deletions, one duplication). Survival analyses showed that patients with two null variants are at higher mortality risk (p-value = .0085, log-rank test). SIGNIFICANCE: Biallelic WWOX pathogenic variants cause an early infantile developmental and epileptic encephalopathy syndrome. The most common seizure types are focal seizures and epileptic spasms. Mortality risk is associated with mutation type; patients with biallelic null WWOX pathogenic variants have significantly lower survival probability compared to those carrying at least one presumed hypomorphic missense pathogenic variant.

Report of a young patient with brain calcifications with a novel homozygous MYORG variant.

Primary familial brain calcifications (PFBC) is characterized by bilateral and symmetrical deposition of inorganic phosphate, mainly in the basal ganglia, thalamus, cerebellum, and dentate nucleus. The symptoms resemble other neuropsychiatric conditions, such as Parkinsonism, dementia, migraine, and mood disorders. Pathogenic variants in six genes have been associated with this disorder, four linked to the autosomal dominant mode (SLC20A2, PDGFRB, PDGFB, and XPR1) and two linked to the recessive fashion (MYORG and JAM2). Herein, we report a young 24-year-old patient with a medical history of bilateral and symmetrical brain calcification and neuropsychiatric symptoms that include movement disturbances (chorea and dystonia), chronic migraine, unexplained tinnitus, and mood swings. After whole-exome sequencing, she was diagnosed with a novel homozygous MYORG variant (c.912_914del; p.(Ser305del)). In silico analysis showed that the variant is located on the extracellular domain of MYORG protein and is predicted to be disease-causing (likely pathogenic), implying that protein features might be affected. This study describes the second Brazilian case of MYORG PFBC-causative gene. Furthermore, it highlights the early age and onset of symptoms of the proband, especially in regard to movement disorders.

The Pathology of Primary Familial Brain Calcification: Implications for Treatment.

Primary familial brain calcification (PFBC) is an inherited neurodegenerative disorder mainly characterized by progressive calcium deposition bilaterally in the brain, accompanied by various symptoms, such as dystonia, ataxia, parkinsonism, dementia, depression, headaches, and epilepsy. Currently, the etiology of PFBC is largely unknown, and no specific prevention or treatment is available. During the past 10 years, six causative genes (SLC20A2, PDGFRB, PDGFB, XPR1, MYORG, and JAM2) have been identified in PFBC. In this review, considering mechanistic studies of these genes at the cellular level and in animals, we summarize the pathogenesis and potential preventive and therapeutic strategies for PFBC patients. Our systematic analysis suggests a classification for PFBC genetic etiology based on several characteristics, provides a summary of the known composition of brain calcification, and identifies some potential therapeutic targets for PFBC.

Temperature instability of a mutation at a multidomain junction in Na,K-ATPase isoform ATP1A3 (p.Arg756His) produces a fever-induced neurological syndrome.

ATP1A3 encodes the α3 isoform of Na,K-ATPase. In the brain, it is expressed only in neurons. Human ATP1A3 mutations produce a wide spectrum of phenotypes, but particular syndromes are associated with unique substitutions. For arginine 756, at the junction of membrane and cytoplasmic domains, mutations produce encephalopathy during febrile infections. Here we tested the pathogenicity of p.Arg756His (R756H) in isogenic mammalian cells. R756H protein had sufficient transport activity to support cells when endogenous ATP1A1 was inhibited. It had half the turnover rate of wildtype, reduced affinity for Na+, and increased affinity for K+. There was modest endoplasmic reticulum retention during biosynthesis at 37 °C but little benefit from the folding drug phenylbutyrate (4-PBA), suggesting a tolerated level of misfolding. When cells were incubated at just 39 °C, however, α3 protein level dropped without loss of ß subunit, paralleled by an increase of endogenous α1. Elevated temperature resulted in internalization of α3 from the surface along with some ß subunit, accompanied by cytoplasmic redistribution of a marker of lysosomes and endosomes, lysosomal-associated membrane protein 1. After return to 37 °C, α3 protein levels recovered with cycloheximide-sensitive new protein synthesis. Heating in vitro showed activity loss at a rate 20- to 30-fold faster than wildtype, indicating a temperature-dependent destabilization of protein structure. Arg756 appears to confer thermal resistance as an anchor, forming hydrogen bonds among four linearly distant parts of the Na,K-ATPase structure. Taken together, our observations are consistent with fever-induced symptoms in patients.