Vitamin D3 deficiency and osteopenia in spastic paraplegia type 5 indicate impaired bone homeostasis.

Hereditary spastic paraplegia type 5 (SPG5) is an autosomal recessively inherited movement disorder characterized by progressive spastic gait disturbance and afferent ataxia. SPG5 is caused by bi-allelic loss of function mutations in CYP7B1 resulting in accumulation of the oxysterols 25-hydroxycholesterol and 27-hydroxycholesterol in serum and cerebrospinal fluid of SPG5 patients. An effect of 27- hydroxycholesterol via the estrogen and liver X receptors was previously shown on bone homeostasis. This study analyzed bone homeostasis and osteopenia in 14 SPG5 patients as a non-motor feature leading to a potential increased risk for bone fractures. T-Scores in CT bone density measurements were reduced, indicating osteopenia in SPG5 patients. Further, we analyzed various metabolites of bone homeostasis by ELISA in serum samples of these patients. We identified a lack of vitamin D3 metabolites (Calcidiol and Calcitriol), an increase in Sclerostin as a bone formation/mineralization inhibiting factor, and a decrease in cross-linked N-telopeptide of type I collagen (NTX), a marker indicating reduced bone resorption. As statin treatment has been found to lower oxysterol levels, we evaluated its effect in samples of the STOP-SPG5 trial and found atorvastatin to normalize the increased sclerostin levels. In summary, our study identified osteopenia as a non-motor feature in SPG5 and suggests the need for vitamin D3 substitution in SPG5 patients. Sclerostin may be considered a therapeutic target and biomarker in upcoming therapeutical trials in SPG5.

Allogeneic hematopoietic cell transplantation for adult metachromatic leukodystrophy: a case series.

ABSTRACT: Metachromatic leukodystrophy (MLD) is a rare genetic disorder caused by pathogenic variants of the ARSA gene, leading to a deficiency of the arylsulfatase A enzyme (ARSA) and consecutive accumulation of galactosylceramide-3-0-sulfate in the nervous system. The condition leads to severe neurological deficits and subsequently results in profound intellectual and motoric disability. Especially, the adult form of MLD, which occurs in individuals aged >16 years, poses significant challenges for treating physicians because of the rarity of cases, limited therapeutic options, and different allogeneic hematopoietic cell transplantation (allo-HCT) protocols worldwide. Here, we report the results of allo-HCT treatment in 4 patients with a confirmed adult MLD diagnosis. Bone marrow or mobilized peripheral progenitor cells were infused after a reduced intensity conditioning regime consisting of fludarabine and treosulfan. In 3 patients, allo-HCT was followed by an infusion of mesenchymal cells to further consolidate ARSA production. We observed a good tolerability and an increase in ARSA levels up to normal range values in all patients. A full donor chimerism was detected in 3 patients within the first 12 months. In a 1-year follow-up, patients with complete donor chimerism showed a neurological stable condition. Only 1 patient with an increasing autologous chimerism showed neurological deterioration and a decline in ARSA levels in the first year. In summary, allo-HCT offers a therapeutic option for reconstituting ARSA enzyme levels in adult patients with MLD, with tolerable side effects.

First case of adult onset neuronal intranuclear inclusion disease with both typical radiological signs and NOTCH2NLC repeat expansions in a Caucasian individual.

BACKGROUND AND PURPOSE: Adult onset neuronal intranuclear inclusion disease (NIID) is a rare neurodegenerative disorder with a heterogeneous clinical presentation that can mimic stroke and various forms of dementia. To date, it has been described almost exclusively in Asian individuals. METHODS: This case presentation includes magnetic resonance imaging (MRI) of the neurocranium, histology by skin biopsy, and long-read genome sequencing. RESULTS: A 75-year-old Caucasian female presented with paroxysmal encephalopathy twice within a 14-month period. Brain MRI revealed high-intensity signals at the cerebral corticomedullary junction (diffusion-weighted imaging) and the paravermal area (fluid-attenuated inversion recovery), a typical distribution observed in adult onset NIID. The diagnosis was corroborated by skin biopsy, which demonstrated eosinophilic intranuclear inclusion bodies, and confirmed by long-read genome sequencing, showing an expansion of the GGC repeat in exon 1 of NOTCH2NLC. CONCLUSIONS: Our case proves adult onset NOTCH2NLC-GGC-positive NIID with typical findings on MRI and histology in a Caucasian patient and underscores the need to consider this diagnosis in non-Asian individuals.

The frequency of non-motor symptoms in SCA3 and their association with disease severity and lifestyle factors.

BACKGROUND: Non-motor symptoms (NMS) are a substantial burden for patients with SCA3. There are limited data on their frequency, and their relation with disease severity and activities of daily living is not clear. In addition, lifestyle may either influence or be affected by the occurrence of NMS. OBJECTIVE: To characterize NMS in SCA3 and investigate possible associations with disease severity and lifestyle factors. METHODS: In a prospective cohort study, we performed a cross-sectional analysis of NMS in 227 SCA3 patients, 42 pre-ataxic mutation carriers, and 112 controls and tested for associations with SARA score, activities of daily living, and the lifestyle factors alcohol consumption, smoking and physical activity. RESULTS: Sleep disturbance, restless legs syndrome, mild cognitive impairment, depression, bladder dysfunction and pallhypesthesia were frequent among SCA3 patients, while mainly absent in pre-ataxic mutation carriers. Except for restless legs syndrome, NMS correlated significantly with disease severity and activities of daily living. Alcohol abstinence was associated with bladder dysfunction. Patients with higher physical activity showed less cognitive impairment and fewer depressive symptoms, but these differences were not significant. CONCLUSION: This study revealed a clear association between disease severity and NMS, likely driven by the progression of the widespread neurodegenerative process. Associations between lifestyle and NMS can probably be attributed to the influence of NMS on lifestyle.

Characterization of Lifestyle in Spinocerebellar Ataxia Type 3 and Association with Disease Severity.

BACKGROUND: Lifestyle could influence the course of hereditary ataxias, but representative data are missing. OBJECTIVE: The objective of this study was to characterize lifestyle in spinocerebellar ataxia type 3 (SCA3) and investigate possible associations with disease parameters. METHODS: In a prospective cohort study, data on smoking, alcohol consumption, physical activity, physiotherapy, and body mass index (BMI) were collected from 243 patients with SCA3 and 119 controls and tested for associations with age of onset, disease severity, and progression. RESULTS: Compared with controls, patients with SCA3 were less active and consumed less alcohol. Less physical activity and alcohol abstinence were associated with more severe disease, but not with progression rates or age of onset. Smoking, BMI, or physiotherapy did not correlate with disease parameters. CONCLUSION: Differences in lifestyle factors of patients with SCA3 and controls as well as associations of lifestyle factors with disease severity are likely driven by the influence of symptoms on behavior. No association between lifestyle and disease progression was detected. © 2021 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

Polyglutamine-Expanded Ataxin-3: A Target Engagement Marker for Spinocerebellar Ataxia Type 3 in Peripheral Blood.

BACKGROUND: Spinocerebellar ataxia type 3 is a rare neurodegenerative disease caused by a CAG repeat expansion in the ataxin-3 gene. Although no curative therapy is yet available, preclinical gene-silencing approaches to reduce polyglutamine (polyQ) toxicity demonstrate promising results. In view of upcoming clinical trials, quantitative and easily accessible molecular markers are of critical importance as pharmacodynamic and particularly as target engagement markers. OBJECTIVE: We aimed at developing an ultrasensitive immunoassay to measure specifically polyQ-expanded ataxin-3 in plasma and cerebrospinal fluid (CSF). METHODS: Using the novel single molecule counting ataxin-3 immunoassay, we analyzed cross-sectional and longitudinal patient biomaterials. RESULTS: Statistical analyses revealed a correlation with clinical parameters and a stability of polyQ-expanded ataxin-3 during conversion from the pre-ataxic to the ataxic phases. CONCLUSIONS: The novel immunoassay is able to quantify polyQ-expanded ataxin-3 in plasma and CSF, whereas ataxin-3 levels in plasma correlate with disease severity. Longitudinal analyses demonstrated a high stability of polyQ-expanded ataxin-3 over a short period. © 2021 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

Bi-allelic loss-of-function variants in BCAS3 cause a syndromic neurodevelopmental disorder.

BCAS3 microtubule-associated cell migration factor (BCAS3) is a large, highly conserved cytoskeletal protein previously proposed to be critical in angiogenesis and implicated in human embryogenesis and tumorigenesis. Here, we established BCAS3 loss-of-function variants as causative for a neurodevelopmental disorder. We report 15 individuals from eight unrelated families with germline bi-allelic loss-of-function variants in BCAS3. All probands share a global developmental delay accompanied by pyramidal tract involvement, microcephaly, short stature, strabismus, dysmorphic facial features, and seizures. The human phenotype is less severe compared with the Bcas3 knockout mouse model and cannot be explained by angiogenic defects alone. Consistent with being loss-of-function alleles, we observed absence of BCAS3 in probands' primary fibroblasts. By comparing the transcriptomic and proteomic data based on probands' fibroblasts with those of the knockout mouse model, we identified similar dysregulated pathways resulting from over-representation analysis, while the dysregulation of some proposed key interactors could not be confirmed. Together with the results from a tissue-specific Drosophila loss-of-function model, we demonstrate a vital role for BCAS3 in neural tissue development.

Metabolic profiling in serum, cerebrospinal fluid, and brain of patients with cerebrotendinous xanthomatosis.

Cerebrotendinous xanthomatosis (CTX) is caused by autosomal recessive loss-of-function mutations in CYP27A1, a gene encoding cytochrome p450 oxidase essential for bile acid synthesis, resulting in altered bile acid and lipid metabolism. Here, we aimed to identify metabolic aberrations that drive ongoing neurodegeneration in some patients with CTX despite chenodeoxycholic acid (CDCA) supplementation, the standard treatment in CTX. Using chromatographic separation techniques coupled to mass spectrometry, we analyzed 26 sterol metabolites in serum and cerebrospinal fluid (CSF) of patients with CTX and in one CTX brain. Comparing samples of drug naive patients to patients treated with CDCA and healthy controls, we identified 7α,12α-dihydroxycholest-4-en-3-one as the most prominently elevated metabolite in serum and CSF of drug naive patients. CDCA treatment substantially reduced or even normalized levels of all metabolites increased in untreated patients with CTX. Independent of CDCA treatment, metabolites of the 27-hydroxylation pathway were nearly absent in all patients with CTX. 27-hydroxylated metabolites accounted for ∼45% of total free sterol content in CSF of healthy controls but <2% in patients with CTX. Metabolic changes in brain tissue corresponded well with findings in CSF. Interestingly, 7α,12α-dihydroxycholest-4-en-3-one and 5α-cholestanol did not exert toxicity in neuronal cell culture. In conclusion, we propose that increased 7α,12α-dihydroxycholest-4-en-3-one and lack of 27-hydroxycholesterol may be highly sensitive metabolic biomarkers of CTX. As CDCA cannot reliably prevent disease progression despite reduction of most accumulated metabolites, supplementation of 27-hydroxylated bile acid intermediates or replacement of CYP27A1 might be required to counter neurodegeneration in patients with progressive disease despite CDCA treatment.

Cerebrospinal fluid findings in patients with psychotic symptoms-a retrospective analysis.

In current international classification systems (ICD-10, DSM5), the diagnostic criteria for psychotic disorders (e.g. schizophrenia and schizoaffective disorder) are based on symptomatic descriptions since no unambiguous biomarkers are known to date. However, when underlying causes of psychotic symptoms, like inflammation, ischemia, or tumor affecting the neural tissue can be identified, a different classification is used ("psychotic disorder with delusions due to known physiological condition" (ICD-10: F06.2) or psychosis caused by medical factors (DSM5)). While CSF analysis still is considered optional in current diagnostic guidelines for psychotic disorders, CSF biomarkers could help to identify known physiological conditions. In this retrospective, partly descriptive analysis of 144 patients with psychotic symptoms and available CSF data, we analyzed CSF examinations' significance to differentiate patients with specific etiological factors (F06.2) from patients with schizophrenia, schizotypal, delusional, and other non-mood psychotic disorders (F2). In 40.3% of all patients, at least one CSF parameter was out of the reference range. Abnormal CSF-findings were found significantly more often in patients diagnosed with F06.2 (88.2%) as compared to patients diagnosed with F2 (23.8%, p < 0.00001). A total of 17 cases were identified as probably caused by specific etiological factors (F06.2), of which ten cases fulfilled the criteria for a probable autoimmune psychosis linked to the following autoantibodies: amphiphysin, CASPR2, CV2, LGl1, NMDA, zic4, and titin. Two cases presented with anti-thyroid tissue autoantibodies. In four cases, further probable causal factors were identified: COVID-19, a frontal intracranial tumor, multiple sclerosis (n = 2), and neurosyphilis. Twenty-one cases remained with "no reliable diagnostic classification". Age at onset of psychotic symptoms differed between patients diagnosed with F2 and F06.2 (p = 0.014), with the latter group being older (median: 44 vs. 28 years). Various CSF parameters were analyzed in an exploratory analysis, identifying pleocytosis and oligoclonal bands (OCBs) as discriminators (F06.2 vs. F2) with a high specificity of > 96% each. No group differences were found for gender, characteristics of psychotic symptoms, substance dependency, or family history. This study emphasizes the great importance of a detailed diagnostic workup in diagnosing psychotic disorders, including CSF analysis, to detect possible underlying pathologies and improve treatment decisions.

PolyQ-expanded ataxin-3 protein levels in peripheral blood mononuclear cells correlate with clinical parameters in SCA3: a pilot study.

In view of upcoming clinical trials, quantitative molecular markers accessible in peripheral blood are of critical importance as prognostic or pharmacodynamic markers in genetic neurodegenerative diseases such as Spinocerebellar Ataxia Type 3 (SCA3), in particular for signaling target engagement. In this pilot study, we focused on the quantification of ataxin-3, the protein altered in SCA3, in human peripheral blood mononuclear cells (PBMCs) acquired from preataxic and ataxic SCA3 mutation carriers as well as healthy controls, as a molecular marker directly related to SCA3 pathophysiology. We established two different highly sensitive TR-FRET-based immunoassays to measure the protein levels of either total full-length, non-expanded and expanded, ataxin-3 or specifically polyQ-expanded ataxin-3. In PBMCs, a clear discrimination between SCA3 mutation carrier and controls were seen measuring polyQ-expanded ataxin-3 protein level. Additionally, polyQ-expanded ataxin-3 protein levels correlated with disease progression and clinical severity as assessed by the Scale for the Assessment and Rating of Ataxia. Total full-length ataxin-3 protein levels were directly influenced by the expression levels of the polyQ-expanded ataxin-3 protein, but were not correlated with clinical parameters. Assessment of ataxin-3 levels in fibroblasts or induced pluripotent stem cells allowed to distinguish mutation carriers from controls, thus providing proof-of-principle validation of our PBMC findings across cell lines. Total full-length or polyQ-expanded ataxin-3 protein was not detectable by TR-FRET assays in other biofluids like plasma or cerebrospinal fluid, indicating the need for ultra-sensitive assays for these biofluids. Standardization studies revealed that tube systems, blood sampling, and PBMC preparation may influence ataxin-3 protein levels indicating a high demand for standardized protocols in biomarker studies. In conclusion, the polyQ-expanded ataxin-3 protein is a promising candidate as a molecular target engagement marker in SCA3 in future clinical trials, determinable even in-easily accessible-peripheral blood biomaterials. These results, however, require validation in a larger cohort and further standardization of modifying conditions.

Multifocal, hypoechogenic nerve thickening in Cerebrotendinous Xanthomatosis.

OBJECTIVE: To characterize peripheral nerve morphology in cerebrotendinous xanthomatosis (CTX) patients using high-resolution ultrasound (HRUS) in vivo. We hypothesized that nerve enlargements might be present in CTX as a result of accumulation of abnormal lipids with deposition also in peripheral nerves. METHODS: Four CTX patients were examined using HRUS to assess morphological abnormalities of peripheral nerves as well as cervical nerve roots 5 and 6. RESULTS: HRUS revealed mild to moderate, hypoechogenic thickening of sensorimotor nerves (ulnar nerve in 1/4, tibial nerve in 3/4, median nerve 4/4 patients) as well as mild enlargement of pure sensory nerves (sural nerve in 2/3, superficial FN in 2/4 patients). The vagal nerve was moderately enlarged in one patient, cervical roots showed moderate enlargements of C5 in two patients, one of which also showing thickening of C6 as well as in another patient. UPSS score was slightly to moderately abnormal in all patients. The Homogeneity score was not increased suggesting regional to inhomogeneous nerve enlargement. CONCLUSIONS: HRUS shows multifocal, hypoechogenic nerve thickening of peripheral nerves and nerve roots in CTX. SIGNIFICANCE: HRUS might serve as a valuable, additive and non-invasive bedside tool to assess peripheral nerve morphology in future clinical studies on CTX patients.

A novel biallelic loss-of-function mutation in TMCO1 gene confirming and expanding the phenotype spectrum of cerebro-facio-thoracic dysplasia.

The main clinical features of cerebro-facio-thoracic dysplasia (CFTD) syndrome, which were described over four decades ago, include facial dysmorphism, multiple malformations of the vertebrae and ribs, and intellectual disability. Recently, a TMCO1 gene mutation was shown to be responsible for an autosomal recessive CFTD syndrome characterized by craniofacial dysmorphism, skeletal anomalies, and intellectual disability. In the current report, we describe two members of a consanguineous family from an Arab community in Israel who were clinically diagnosed as suffering from craniofacial dysmorphism, skeletal anomalies, intellectual disability, and epilepsy. Both affected siblings had behavioral difficulties such as anxiety and emotional instability with impulsive behaviors. Whole-exome sequencing revealed a homozygous stop-gain mutation NM_019026.4: c.616C > T; p.(Arg206*) in exon 6 of the TMCO1 gene. Bioinformatics analysis suggested a structural model for the TMCO1 protein and its homologues. The clinical features of our patients were compared with those of the only other five studies available in the literature. We conclude that this mutation in the TMCO1 gene is responsible for the various clinical manifestations of CFTD syndrome exhibited by the patients studied that expand the phenotypic spectrum of the disease to include epilepsy as a characteristic feature of this syndrome.

Clinical, radiological, and genetic characteristics of 16 patients with ACO2 gene defects: Delineation of an emerging neurometabolic syndrome.

Mitochondrial aconitase is the second enzyme in the tricarboxylic acid (TCA) cycle catalyzing the interconversion of citrate into isocitrate and encoded by the nuclear gene ACO2. A homozygous pathogenic variant in the ACO2 gene was initially described in 2012 resulting in a novel disorder termed "infantile cerebellar retinal degeneration" (ICRD, OMIM#614559). Subsequently, additional studies reported patients with pathogenic ACO2 variants, further expanding the genetic and clinical spectrum of this disorder to include milder and later onset manifestations. Here, we report an international multicenter cohort of 16 patients (of whom 7 are newly diagnosed) with biallelic pathogenic variants in ACO2 gene. Most patients present in early infancy with severe truncal hypotonia, truncal ataxia, variable seizures, evolving microcephaly, and ophthalmological abnormalities of which the most dominant are esotropia and optic atrophy with later development of retinal dystrophy. Most patients remain nonambulatory and do no acquire any language, but a subgroup of patients share a more favorable course. Brain magnetic resonance imaging (MRI) is typically normal within the first months but global atrophy gradually develops affecting predominantly the cerebellum. Ten of our patients were homozygous to the previously reported c.336C>G founder mutation while the other six patients were all compound heterozygotes displaying 10 novel mutations of whom 2 were nonsense predicting a deleterious effect on enzyme function. Structural protein modeling predicted significant impairment in aconitase substrate binding in the additional missense mutations. This study provides the most extensive cohort of patients and further delineates the clinical, radiological, biochemical, and molecular features of ACO2 deficiency.

CNTNAP1 mutations cause CNS hypomyelination and neuropathy with or without arthrogryposis.

OBJECTIVE: To explore the phenotypic spectrum and pathophysiology of human disease deriving from mutations in the CNTNAP1 gene. METHODS: In a field study on consanguineous Palestinian families, we identified 3 patients carrying homozygous mutations in the CNTNAP1 gene using whole-exome sequencing. An unrelated Irish family was detected by screening the GENESIS database for further CNTNAP1 mutations. Neurophysiology, MRI, and nerve biopsy including electron microscopy were performed for deep phenotyping. RESULTS: We identified 3 novel CNTNAP1 mutations in 5 patients from 2 families: c.2015G>A:p.(Trp672*) in a homozygous state in family 1 and c.2011C>T:p.(Gln671*) in a compound heterozygous state with c.2290C>T:p.(Arg764Cys) in family 2. Affected patients suffered from a severe CNS disorder with hypomyelinating leukodystrophy and peripheral neuropathy of sensory-motor type. Arthrogryposis was present in 2 patients but absent in 3 patients. Brain MRI demonstrated severe hypomyelination and secondary cerebral and cerebellar atrophy as well as a mega cisterna magna and corpus callosum hypoplasia. Nerve biopsy revealed very distinct features with lack of transverse bands at the paranodes and widened paranodal junctional gaps. CONCLUSIONS: CNTNAP1 mutations have recently been linked to patients with arthrogryposis multiplex congenita. However, we show that arthrogryposis is not an obligate feature. CNTNAP1-related disorders are foremost severe hypomyelinating disorders of the CNS and the peripheral nervous system. The pathology is partly explained by the involvement of CNTNAP1 in the proper formation and preservation of paranodal junctions and partly by the assumed role of CNTNAP1 as a key regulator in the development of the cerebral cortex.

Structures of Merkel cell polyomavirus VP1 complexes define a sialic acid binding site required for infection.

The recently discovered human Merkel cell polyomavirus (MCPyV or MCV) causes the aggressive Merkel cell carcinoma (MCC) in the skin of immunocompromised individuals. Conflicting reports suggest that cellular glycans containing sialic acid (Neu5Ac) may play a role in MCPyV infectious entry. To address this question, we solved X-ray structures of the MCPyV major capsid protein VP1 both alone and in complex with several sialylated oligosaccharides. A shallow binding site on the apical surface of the VP1 capsomer recognizes the disaccharide Neu5Ac-α2,3-Gal through a complex network of interactions. MCPyV engages Neu5Ac in an orientation and with contacts that differ markedly from those observed in other polyomavirus complexes with sialylated receptors. Mutations in the Neu5Ac binding site abolish MCPyV infection, highlighting the relevance of the Neu5Ac interaction for MCPyV entry. Our study thus provides a powerful platform for the development of MCPyV-specific vaccines and antivirals. Interestingly, engagement of sialic acid does not interfere with initial attachment of MCPyV to cells, consistent with a previous proposal that attachment is mediated by a class of non-sialylated carbohydrates called glycosaminoglycans. Our results therefore suggest a model in which sialylated glycans serve as secondary, post-attachment co-receptors during MCPyV infectious entry. Since cell-surface glycans typically serve as primary attachment receptors for many viruses, we identify here a new role for glycans in mediating, and perhaps even modulating, post-attachment entry processes.