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.

PSEN1/SLC20A2 double mutation causes early-onset Alzheimer's disease and primary familial brain calcification co-morbidity.

Primary familial brain calcification (PFBC; formerly Fahr's disease) and early-onset Alzheimer's disease (EOAD) may share partially overlapping pathogenic principles. Although the heterozygous loss-of-function mutation c.1523 + 1G > T in the PFBC-linked gene SLC20A2 was detected in a patient with asymmetric tremor, early-onset dementia, and brain calcifications, CSF ß-amyloid parameters and FBB-PET suggested cortical ß-amyloid pathology. Genetic re-analysis of exome sequences revealed the probably pathogenic missense mutation c.235G > A/p.A79T in PSEN1. The SLC20A2 mutation segregated with mild calcifications in two children younger than 30 years. We thus describe the stochastically extremely unlikely co-morbidity of genetic PFBC and genetic EOAD. The clinical syndromes pointed to additive rather than synergistic effects of the two mutations. MRI data revealed the formation of PFBC calcifications decades before the probable onset of the disease. Our report furthermore exemplifies the value of neuropsychology and amyloid PET for differential diagnosis.

The Role of Voltage-Gated Calcium Channels in Basal Ganglia Neurodegenerative Disorders.

Calcium (Ca2+) plays a central role in regulating many cellular processes and influences cell survival. Several mechanisms can disrupt Ca2+ homeostasis to trigger cell death, including oxidative stress, mitochondrial damage, excitotoxicity, neuroinflammation, autophagy, and apoptosis. Voltage-gated Ca2+ channels (VGCCs) act as the main source of Ca2+ entry into electrically excitable cells, such as neurons, and they are also expressed in glial cells such as astrocytes and oligodendrocytes. The dysregulation of VGCC activity has been reported in both Parkinson's disease (PD) and Huntington's (HD). PD and HD are progressive neurodegenerative disorders (NDs) of the basal ganglia characterized by motor impairment as well as cognitive and psychiatric dysfunctions. This review will examine the putative role of neuronal VGCCs in the pathogenesis and treatment of central movement disorders, focusing on PD and HD. The link between basal ganglia disorders and VGCC physiology will provide a framework for understanding the neurodegenerative processes that occur in PD and HD, as well as a possible path towards identifying new therapeutic targets for the treatment of these debilitating disorders.

Role of phosphate transporter PiT-2 in the pathogenesis of primary brain calcification.

Primary brain calcification (PBC), also known as idiopathic basal ganglia calcification (IBGC), primary familial brain calcification (PFBC) and so on, is a rare intractable disease characterized by abnormal mineral deposits, including mostly calcium in the basal ganglia, thalamus, and cerebellum. The causative gene of familial PBC is SLC20A2, which encodes the phosphate transporter PiT-2. Despite this knowledge, the molecular mechanism underlying SLC20A2-associated PBC remains unclear. In the present study, we investigated whether haploinsufficiency or a dominant-negative mechanism reduced Pi uptake in two PiT-2 variants (T115 M and R467X). We demonstrated that the presence of T115 M or R467X had no dominant-negative effect on Pi transport activity of wild-type (WT). In addition, the subcellular localization of R467X completely differed from that of WT, indicating that there is no interaction between R467X and WT. Conversely, T115 M and WT showed almost the same localization. Therefore, we examined the interaction between T115 M and WT using the bioluminescence resonance energy transfer (BRET) method. Although WT and T115 M interact with each other, T115 M does not inhibit WT's Pi transport activity. These results suggest that the role of SLC20A2 in the pathogenesis of PBC may involve decreased intracellular Pi uptake by a haploinsufficiency mechanism rather than a dominant-negative mechanism; agents promoting PiT-2 dimerization may be promising potential therapeutic agents for PBC.

Familial idiopathic basal ganglia calcification with a heterozygous missense variant (c.902C>T/p.P307L) in SLC20A2 showing widespread cerebrovascular lesions.

We describe a postmortem case of familial idiopathic basal ganglia calcification (FIBGC) in a 72-year-old Japanese man. The patient showed progressive cognitive impairment with a seven-year clinical course and calcification of the basal ganglia, thalami, and cerebellar dentate nuclei. A novel heterozygous missense variant in SLC20A2 (c.920C>T/p.P307L), a type III sodium-dependent phosphate transporter (PiT-2), was subsequently identified, in addition to typical neuropathological findings of FIBGC, such as capillary calcification of the occipital gray matter, confluent calcification of the basal ganglia and cerebellar white matter, widespread occurrence of vasculopathic changes, cerebrovascular lesions, and vascular smooth muscle cell depletion. Immunohistochemistry for PiT-2 protein revealed no apparent staining in endothelial cells in the basal ganglia and insular cortex; however, the immunoreactivity in endothelial cells of the cerebellum was preserved. Moreover, Western blot analysis identified preserved PiT-2 immunoreactivity signals in the frontal cortex and cerebellum. The variant identified in the present patient could be associated with development of FIBGC and is known to be located at the large intracytoplasmic part of the PiT-2 protein, which has potential phosphorylation sites with importance in the regulation of inorganic phosphate transport activity. The present case is an important example to prove that FIGBC could stem from a missense variant in the large intracytoplasmic loop of the PiT-2 protein. Abnormal clearance of inorganic phosphate in the brain could be related to the development of vascular smooth muscle damage, the formation of cerebrovascular lesions, and subsequent brain calcification in patients with FIBGC with SLC20A2 variants.

Novel splicing-site mutation in DCAF17 gene causing Woodhouse-Sakati syndrome in a large consanguineous family.

BACKGROUND: Woodhouse-Sakati syndrome is a rare autosomal recessive disease with endocrine and neuroectodermal aberrations with heterogeneous phenotypes and disease course. The most common phenotypes of the disease are progressive sensorineural hearing loss and alopecia, mild-to-moderate mental retardation and hypogonadism. The disease results from mutations in the DCAF17 gene. METHOD: Here, we reported a large consanguineous pedigree with multiple affected individuals with Woodhouse-Sakati syndrome phenotypes. Laboratory tests confirmed the endocrine perturbance in affected individuals. To find out the underlying genetic change, whole-exome sequencing was carried out. RESULT: Analysis of the exome data identified a splicing-site deletion NM_025000.3:c.1423-1_1425delGACA in DCAF17 gene. Sanger sequencing confirmed the co-segregation of the variant with the disease phenotypes in the family. CONCLUSION: The variant is predicted to cause aberrant splicing, i.e., exon skipping, resulting in the translation of a truncated functionless protein which results in appearance of typical phenotypic features and clinical laboratory findings of Woodhouse-Sakati syndrome in affected members of the family.

Gray matter structural plasticity in patients with basal ganglia germ cell tumors: A voxel-based morphometry study.

BACKGROUND: Basal ganglia germ cell tumors (BGGCTs) are rare intracranial germ cell tumors (iGCTs) that often presents with cognitive impairment. OBJECTIVE: To assess structural brain plasticity in the presence of unilateral basal ganglia germ cell tumors (BGGCTs), and the correlation between gray matter volume (GMV) changes and cognitive tests. MATERIALS AND METHODS: We applied voxel-based morphometry (VBM) to structural magnetic resonance imaging (MRI) scans to compare a sample of 41 patients with BGGCTs in the left (n = 22) or right (n = 19) and a sample of 16 patients as control group using a two-sample t-test, correcting for family-wise-errors. A battery of cognitive tests was administered to all BGGCTs patients prior to MRI. We used Pearson correlation analysis to assess the correlation between cognitive test scores and GMV changes. RESULTS: In patients with left BGGCTs, whole-brain VBM analysis revealed a large cluster of voxels reflecting an increase in GMV in the left parahippocampal region (k = 529 voxels, T = 4.18, p < 0.01), right middle cingulate cortex (k = 172 voxels, T = 3.96, p < 0.01), and a decrease in volume in the left thalamus (k = 527 voxels, T = -4.88, p < 0.01), right inferior frontal gyrus (k = 495 voxels, T = -4.29, p < 0.01). Pearson correlation analysis showed that the GMV were significantly correlated with the Integrated Visual and Auditory continuous performance test (IVA-CPT) scale (r = 0.637, P = 0.002), abstract reasoning (r = 0.597, P = 0.011), Self-rating Depression Scale (SAS) scale (r = -0.623, P = 0.004) and memory recall (r = 0.648, P = 0.003). CONCLUSION: These results demonstrate that slow growing but destructive BGGCTs markedly and asymmetrically effect the GMV in left parahippocampal, left thalamus, right middle cingulate cortex, right inferior frontal gyrus and GMV changes were significantly associated with cognitive test.

Multimodal Evoked Potential Profiles in Woodhouse-Sakati Syndrome.

PURPOSE: Woodhouse-Sakati syndrome is a rare autosomal recessive syndrome caused by homozygous mutations in the DCAF17 gene, characterized by marked neurologic and endocrine manifestations in the setting of brain iron accumulation and white matter lesions on neuroimaging. Here, we report electrophysiologic profiles in Woodhouse-Sakati syndrome and their possible value in understanding disease pathophysiology and phenotypic variability. METHODS: Thirteen genetically confirmed Woodhouse-Sakati syndrome patients were evaluated via different evoked potential (EP) modalities, including brainstem auditory EPs, pattern reversal visual EPs, and somatosensory EPs to tibial and/or median nerves. RESULTS: All EP modalities showed variable abnormalities. Pattern reversal visual EPs were recorded in all patients, with nine patients exhibiting abnormal results. From those, seven patients showed prolonged P100 latencies after stimulation of right and left eyes for each in turn. Two patients showed P100 latency abnormality after single eye stimulation recorded from midoccipital electrode. Median somatosensory EPs were recorded in 10 patients, with 6 patients having a prolonged cortical N19 response. Tibial somatosensory EP was performed for 11 patients, and 8 patients showed abnormal results where P37 cortical response was absent or prolonged, whereas peripheral potentials at the popliteal fossa were normal. Brainstem auditory EPs were abnormal only in two patients, with prolonged wave III and V latencies. Five patients with hearing impairment presented with normal brainstem auditory EP results. CONCLUSIONS: Multiple EP abnormalities are observed in Woodhouse-Sakati syndrome patients, mainly in pattern reversal visual EPs and somatosensory EPs. These findings indicate potential myelin dysfunction that has a role in the underlying pathophysiology, disease course, and phenotypic variability.

First pediatric case with primary familial brain calcification due to a novel variant on the MYORG gene and review of the literature.

Variants in the myogenesis-regulating glycosidase (MYORG) gene which is known as the first autosomal recessive gene that has been associated with primary familial brain calcification (AR-PFBC). Although adult patients have been reported, no pediatric case has been reported until now. Herein, we review the clinical and radiological features of all AR- PFBC patients with biallelic variants in the MYORG gene who were reported until now, and we report the youngest patient who has a novel homozygous variant. Since the first identification of the MYORG gene in 2018, 74cases of MYORG variants related to AR-PFBC were evaluated. The ages of symptom onset of the patients ranged between 7.5 and 87 years. The most frequent clinical courses were speech impairment, movement disorder and cerebellar signs. All patients showed basal ganglia calcification usually bilaterally with different severities. Conclusion; herein, we reported the first pediatric patient in the literature who had a novel homozygous variant in the MYORG gene with mild clinic findings.

An autopsy case of corticobasal degeneration with inferior olivary hypertrophy.

We report autopsy results of a female patient who was confirmed pathologically as having corticobasal degeneration (CBD). This patient presented with progressive gait disturbance at the age of 66 years, and subsequently showed parkinsonism with a right-sided predominance and dementia. She was clinically diagnosed as having possible corticobasal syndrome without palatal myoclonus throughout the disease course. An autopsy at 72 years of age revealed that neuronal loss with gliosis was severe in the substantia nigra and the portion from hippocampal cornu ammonis (CA1) region to the parahippocampal gyrus, and mild-to-moderate in the basal ganglia, thalamus, red nucleus, dentate nucleus, and cerebral cortices, predominantly in the frontal lobe. Myelin pallor was observed in the pyramidal tract of the brainstem and central tegmental tract. Neurodegenerative or axonal degenerative findings were observed predominantly on the left side, except for the dentate nucleus, which was more affected on the right side. The inferior olivary nucleus exhibited hypertrophic degeneration predominantly on the left side. The topography of neurodegeneration was likely to correspond to the dentate nucleus and inferior olivary nucleus. Phosphorylated tau-immunoreactive pretangles, neurofibrillary tangles, coiled bodies, and threads were diffusely observed in the whole brain. The distribution of tau deposits was prominent in the deeper affected lesions of the dentate nucleus and inferior olivary nucleus. Inferior olivary hypertrophy is unusual in patients with CBD. It is highly possible that the neurodegeneration of the inferior olivary nucleus followed that of the dentate nucleus in our patient. Moreover, these results indicate not only the severity of neurodegenerative changes, but also that of tau deposition that could be related to the topography of the projections of the dentato-olivary pathway. Tau propagation and subsequent neurodegeneration along the fiber connections may have occurred. Our results support the possibility that progression of CBD lesions can be mediated by tau propagation.

Diagnostic Accuracy of Affective Social Tasks in the Clinical Classification Between the Behavioral Variant of Frontotemporal Dementia and Other Neurodegenerative Disease.

BACKGROUND: Severe socio-emotional impairments characterize the behavioral variant of frontotemporal dementia (bvFTD). However, literature reports social cognition disorders in other dementias. OBJECTIVE: In this study, we investigated the accuracy of social cognition performances in the early and differential diagnosis of bvFTD. METHODS: We included 131 subjects: 32 bvFTD, 26 Alzheimer's disease (AD), 16 primary progressive aphasia (PPA), 17 corticobasal syndrome (CBS), and 40 healthy control (HC). Each subject completed the Ekman 60 faces (Ek-60F) test assessing basic emotion recognition and the Story-based Empathy Task (SET) assessing attribution of intentions/emotions. A combined social measure (i.e., Emotion Recognition and Attribution (ERA) index) was calculated. One-way ANOVA has been used to compare performances among groups, while receiver operating characteristic (ROC) curve tested measures ability to distinguish subjects with and without bvFTD. RESULTS: Ek-60F and ERA index scores were significantly lower in bvFTD versus HC, AD, and PPA groups. ROC analyses significantly distinguished bvFTD from HC (AUC 0.82-0.92), with the Ek-60F test showing the highest performance, followed by the ERA index. These two social measures showed the best accuracy in detecting bvFTD from AD (AUC 0.78-0.74) and PPA (AUC 0.80-0.76). Investigated measures failed in detecting bvFTD from CBS. CONCLUSION: Accuracy analyses support the advantage of using social cognition tests for bvFTD diagnosis. Short social battery may reduce uncertainties and improve disease identification in clinical settings. We recommend a revision of current clinical criteria considering neuropsychological deficits in emotion recognition and processing tasks as key cognitive markers of this neurodegenerative syndrome.

18F-AV-1451 positron emission tomography in neuropathological substrates of corticobasal syndrome.

Multiple neuropathological processes can manifest in life as a corticobasal syndrome. We sought to relate retention of the tau-PET tracer 18F-AV-1451 and structural magnetic resonance measures of regional atrophy to clinical features in clinically diagnosed and neuropathologically confirmed cases of corticobasal syndrome and to determine whether these vary with the underlying neuropathological changes. In this observational, cross-sectional study, 11 subjects (eight female and three male, median age 72 years) with corticobasal syndrome underwent structural MRI, tau-PET with 18F-AV-1451, amyloid-PET with 11C-Pittsburgh compound B, detailed clinical examinations and neuropsychological testing. Of the 11, three had evidence of high amyloid burden consistent with Alzheimer's disease while eight did not. Neuropathological evaluations were acquired in six cases. Mixed effects general linear models were used to compare 18F-AV-1451 retention and atrophy in amyloid-negative corticobasal syndrome cases to 32 age-matched healthy control subjects and to relate cortical and subcortical 18F-AV-1451 retention and atrophy to clinical features. Subjects without amyloid, including three with pathologically confirmed corticobasal degeneration, showed greater regional 18F-AV-1451 retention and associated regional atrophy in areas commonly associated with corticobasal degeneration pathology than healthy control subjects [retention was higher compared to healthy controls (P = 0.0011), driven especially by the precentral gyrus (P = 0.011) and pallidum (P < 0.0001), and greater atrophy was seen in subjects compared to control subjects (P = 0.0004)]. Both 18F-AV-1451 retention and atrophy were greater in the clinically more affected hemisphere [on average, retention was 0.173 standardized uptake value ratio units higher on the more affected side (95% confidence interval, CI 0.11-0.24, P < 0.0001), and volume was 0.719 lower on the more affected side (95% CI 0.35-1.08, P = 0.0001)]. 18F-AV-1451 retention was greater in subcortical than in cortical regions, P < 0.0001. In contrast to these findings, subjects with amyloid-positive corticobasal syndrome, including two neuropathologically confirmed cases of Alzheimer's disease, demonstrated greater and more widespread 18F-AV-1451 retention and regional atrophy than observed in the amyloid-negative cases. There was thalamic 18F-AV-1451 retention but minimal cortical and basal ganglia uptake in a single corticobasal syndrome subject without neuropathological evidence of tau pathology, likely representing non-specific signal. Asymmetric cortical and basal ganglia 18F-AV-1451 retention consonant with the clinical manifestations characterize corticobasal syndrome due to corticobasal degeneration, whereas the cortical retention in cases associated with Alzheimer's disease is greater and more diffuse.

Strain-specific clearance of seed-dependent tau aggregation by lithium-induced autophagy.

Different conformational strains of tau have been implicated in the clinicopathological heterogeneity of tauopathies. In this study, we hypothesized that distinct strains are degraded in a different manner. Lithium, a drug for bipolar disorder, had previously been reported to reduce aggregation-prone protein content by promoting autophagy. Here, we assessed the effects of lithium on tau aggregates using different tauopathy brain seeds. SH-SY5Y cells were transfected with C-terminal tau fragment Tau-CTF24 (residues 243-441), and Alzheimer's disease (AD), progressive supranuclear palsy (PSP), and corticobasal degeneration (CBD) brain seeds were introduced. After 48-h lithium treatment, sarkosyl-insoluble fractions were prepared. Lithium treatment was found to reduce the amount of insoluble tau and p62, and increase LC3-II levels along with the number of autophagic vacuoles in AD-seeded cells. The effects were lower in case of CBD seeds, and comparable between PSP and AD seeds. An inhibitor of myo-inositol monophosphatase (IMPase) also demonstrated similar effects. Overall, the study suggested that aggregated tau protein is degraded by lithium-induced autophagy, influencing IMPase in a strain-specific manner.

Basal ganglia calcification in hypoparathyroidism and pseudohypoparathyroidism: local and systemic metabolic mechanisms.

BACKGROUND: Hypoparathyroidism and pseudohypoparathyroidism are rare disorders of mineral metabolism which may be associated with soft tissue calcification in the basal ganglia in the brain, and occasionally the skin and other tissues. The basal ganglia are the most common sites of calcification in the central nervous system in these disorders, and were first associated with this manifestation in a report from the Mayo Clinic in 1939. The reasons why the basal ganglia are a common site of soft tissue calcification in these rare disorders has been a matter of investigation for many years. FINDINGS: Due to recent increased understanding of phosphate transport and new insights gained from mRNA expression in the basal ganglia, the pathophysiology of basal ganglia calcification (BGC) is now clearer. There is evidence that the absence of parathyroid hormone in hypoparathyroidism may play a direct role, but this is clearly not the case in pseudohypoparathyroidism, which is associated with increased parathyroid hormone levels. Maintaining the calcium/phosphorus ratio as close to normal as possible, and maintaining normal serum phosphate levels, may help mitigate the progression of BGC. There is no evidence of regression of BGC with conventional treatment, and long-term data with adjunctive or replacement therapy with parathyroid hormone or its analogues are not yet available. PURPOSE OF THE REVIEW: This review will focus on the pathophysiology of BGC in hypoparathyroidism and pseudohypoparathyroidism, and review the proposed pathophysiologic mechanisms, as well as the clinical implications of BGC on patient quality of life.

The retina as a window to the basal ganglia: Systematic review of the potential link between retinopathy and hyperkinetic disorders in diabetes.

There is evidence that glycemic fluctuations trigger vascular-mediated dysfunction in both the retina and the striatopallidal regions in patients with diabetes. The latter is associated with a variety of hyperkinetic disorders that are rare but disabling and potentially preventable. We conducted a systematic review of the potential association between diabetic retinopathy and the risk and prognosis of hyperkinetic disorders in patients with diabetes. We identified a total of 461 articles and 147 were eligible for review. Nine out of 147 articles (6.12%) reported 13 patients with information on diabetic retinopathy. Glycemic fluctuations were present at onset in 10 patients (77%) and retinopathy was present in nine of them (69.23%). The degree of retinopathy was reported in four patients. Two had severe, bilateral proliferative retinopathy, one had moderate-to-severe non-proliferative retinopathy and one had non-proliferative retinopathy. In the nine patients with retinopathy, hyperkinesia persisted, required higher doses of dopamine receptor antagonists or deep brain stimulation. Retinopathy was absent in four cases (30.77%). In these patients, hyperkinesia resolved spontaneously or with lower doses of dopamine receptor antagonists. Diabetic retinopathy could be an indirect marker of striatopallidal microangiopathy in patients with diabetes. The severity of retinopathy may be associated with increased risk or worse prognosis for patients who develop hyperkinetic disorders of the diabetic striatopathy spectrum. Early detection of retinopathy could identify patients in which avoiding glycemic fluctuations may prevent the development of striatopathy and hyperkinetic disorders.