Mutated ATP10B increases Parkinson's disease risk by compromising lysosomal glucosylceramide export.

Parkinson's disease (PD) is a progressive neurodegenerative brain disease presenting with a variety of motor and non-motor symptoms, loss of midbrain dopaminergic neurons in the substantia nigra pars compacta and the occurrence of α-synuclein-positive Lewy bodies in surviving neurons. Here, we performed whole exome sequencing in 52 early-onset PD patients and identified 3 carriers of compound heterozygous mutations in the ATP10B P4-type ATPase gene. Genetic screening of a Belgian PD and dementia with Lewy bodies (DLB) cohort identified 4 additional compound heterozygous mutation carriers (6/617 PD patients, 0.97%; 1/226 DLB patients, 0.44%). We established that ATP10B encodes a late endo-lysosomal lipid flippase that translocates the lipids glucosylceramide (GluCer) and phosphatidylcholine (PC) towards the cytosolic membrane leaflet. The PD associated ATP10B mutants are catalytically inactive and fail to provide cellular protection against the environmental PD risk factors rotenone and manganese. In isolated cortical neurons, loss of ATP10B leads to general lysosomal dysfunction and cell death. Impaired lysosomal functionality and integrity is well known to be implicated in PD pathology and linked to multiple causal PD genes and genetic risk factors. Our results indicate that recessive loss of function mutations in ATP10B increase risk for PD by disturbed lysosomal export of GluCer and PC. Both ATP10B and glucocerebrosidase 1, encoded by the PD risk gene GBA1, reduce lysosomal GluCer levels, emerging lysosomal GluCer accumulation as a potential PD driver.

Loss of DPP6 in neurodegenerative dementia: a genetic player in the dysfunction of neuronal excitability.

Emerging evidence suggested a converging mechanism in neurodegenerative brain diseases (NBD) involving early neuronal network dysfunctions and alterations in the homeostasis of neuronal firing as culprits of neurodegeneration. In this study, we used paired-end short-read and direct long-read whole genome sequencing to investigate an unresolved autosomal dominant dementia family significantly linked to 7q36. We identified and validated a chromosomal inversion of ca. 4 Mb, segregating on the disease haplotype and disrupting the coding sequence of dipeptidyl-peptidase 6 gene (DPP6). DPP6 resequencing identified significantly more rare variants-nonsense, frameshift, and missense-in early-onset Alzheimer's disease (EOAD, p value = 0.03, OR = 2.21 95% CI 1.05-4.82) and frontotemporal dementia (FTD, p = 0.006, OR = 2.59, 95% CI 1.28-5.49) patient cohorts. DPP6 is a type II transmembrane protein with a highly structured extracellular domain and is mainly expressed in brain, where it binds to the potassium channel Kv4.2 enhancing its expression, regulating its gating properties and controlling the dendritic excitability of hippocampal neurons. Using in vitro modeling, we showed that the missense variants found in patients destabilize DPP6 and reduce its membrane expression (p < 0.001 and p < 0.0001) leading to a loss of protein. Reduced DPP6 and/or Kv4.2 expression was also detected in brain tissue of missense variant carriers. Loss of DPP6 is known to cause neuronal hyperexcitability and behavioral alterations in Dpp6-KO mice. Taken together, the results of our genomic, genetic, expression and modeling analyses, provided direct evidence supporting the involvement of DPP6 loss in dementia. We propose that loss of function variants have a higher penetrance and disease impact, whereas the missense variants have a variable risk contribution to disease that can vary from high to low penetrance. Our findings of DPP6, as novel gene in dementia, strengthen the involvement of neuronal hyperexcitability and alteration in the homeostasis of neuronal firing as a disease mechanism to further investigate.

GDAP2 mutations implicate susceptibility to cellular stress in a new form of cerebellar ataxia.

Autosomal recessive cerebellar ataxias are a group of rare disorders that share progressive degeneration of the cerebellum and associated tracts as the main hallmark. Here, we report two unrelated patients with a new subtype of autosomal recessive cerebellar ataxia caused by biallelic, gene-disruptive mutations in GDAP2, a gene previously not implicated in disease. Both patients had onset of ataxia in the fourth decade. Other features included progressive spasticity and dementia. Neuropathological examination showed degenerative changes in the cerebellum, olive inferior, thalamus, substantia nigra, and pyramidal tracts, as well as tau pathology in the hippocampus and amygdala. To provide further evidence for a causative role of GDAP2 mutations in autosomal recessive cerebellar ataxia pathophysiology, its orthologous gene was investigated in the fruit fly Drosophila melanogaster. Ubiquitous knockdown of Drosophila Gdap2 resulted in shortened lifespan and motor behaviour anomalies such as righting defects, reduced and uncoordinated walking behaviour, and compromised flight. Gdap2 expression levels responded to stress treatments in control flies, and Gdap2 knockdown flies showed increased sensitivity to deleterious effects of stressors such as reactive oxygen species and nutrient deprivation. Thus, Gdap2 knockdown in Drosophila and GDAP2 loss-of-function mutations in humans lead to locomotor phenotypes, which may be mediated by altered responses to cellular stress.

Motor neuron degeneration in spastic paraplegia 11 mimics amyotrophic lateral sclerosis lesions.

The most common form of autosomal recessive hereditary spastic paraplegia is caused by mutations in the SPG11/KIAA1840 gene on chromosome 15q. The nature of the vast majority of SPG11 mutations found to date suggests a loss-of-function mechanism of the encoded protein, spatacsin. The SPG11 phenotype is, in most cases, characterized by a progressive spasticity with neuropathy, cognitive impairment and a thin corpus callosum on brain MRI. Full neuropathological characterization has not been reported to date despite the description of >100 SPG11 mutations. We describe here the clinical and pathological features observed in two unrelated females, members of genetically ascertained SPG11 families originating from Belgium and Italy, respectively. We confirm the presence of lesions of motor tracts in medulla oblongata and spinal cord associated with other lesions of the central nervous system. Interestingly, we report for the first time pathological hallmarks of SPG11 in neurons that include intracytoplasmic granular lysosome-like structures mainly in supratentorial areas, and others in subtentorial areas that are partially reminiscent of those observed in amyotrophic lateral sclerosis, such as ubiquitin and p62 aggregates, except that they are never labelled with anti-TDP-43 or anti-cystatin C. The neuropathological overlap with amyotrophic lateral sclerosis, associated with some shared clinical manifestations, opens up new fields of investigation in the physiopathological continuum of motor neuron degeneration.

Clinical features of TBK1 carriers compared with C9orf72, GRN and non-mutation carriers in a Belgian cohort.

We identified in a cohort of patients with frontotemporal dementia (n = 481) or amyotrophic lateral sclerosis (n = 147), 10 index patients carrying a TBK1 loss of function mutation reducing TBK1 expression by 50%. Here, we describe the clinical and pathological characteristics of the 10 index patients and six of their affected relatives carrying a TBK1 mutation. Six TBK1 carriers were diagnosed with frontotemporal dementia, seven with amyotrophic lateral sclerosis, one with both clinical phenotypes and two with dementia unspecified. The mean age at onset of all 16 TBK1 carriers was 62.1 ± 8.9 years (range 41-73) with a mean disease duration of 4.7 ± 4.5 years (range 1-13). TBK1 carriers with amyotrophic lateral sclerosis had shorter disease duration than carriers with frontotemporal dementia. Six of seven TBK1 carriers were diagnosed with the behavioural variant of frontotemporal dementia, presenting predominantly as disinhibition. Memory loss was an important associated symptom in the initial phase of the disease in all but one of the carriers with frontotemporal dementia. Three of the patients with amyotrophic lateral sclerosis exhibited pronounced upper motor neuron symptoms. Overall, neuroimaging displayed widespread atrophy, both symmetric and asymmetric. Brain perfusion single-photon emission computed tomography or fluorodeoxyglucose-positron emission tomography showed asymmetric and predominantly frontotemporal involvement. Neuropathology in two patients demonstrated TDP-43 type B pathology. Further, we compared genotype-phenotype data of TBK1 carriers with frontotemporal dementia (n = 7), with those of frontotemporal dementia patients with a C9orf72 repeat expansion (n = 65) or a GRN mutation (n = 52) and with frontotemporal dementia patients (n = 259) negative for mutations in currently known causal genes. TBK1 carriers with frontotemporal dementia had a later age at onset (63.3 years) than C9orf72 carriers (54.3 years) (P = 0.019). In clear contrast with TBK1 carriers, GRN carriers were more often diagnosed with the language variant than the behavioural variant, and presented in case of the diagnosis of behavioural variant, more often than TBK1 carriers with apathy as the predominant characteristic (P = 0.004). Also, TBK1 carriers exhibited more often extrapyramidal symptoms than C9orf72 carriers (P = 0.038). In conclusion, our study identified clinical differences between the TBK1, C9orf72 and GRN carriers, which allows us to formulate guidelines for genetic diagnosis. After a negative result for C9orf72, patients with both frontotemporal dementia and amyotrophic lateral sclerosis should be tested first for mutations in TBK1. Specifically in frontotemporal dementia patients with early memory difficulties, a relatively late age at onset or extrapyramidal symptoms, screening for TBK1 mutations should be considered.

Activation of osmolyte pathways in inflammatory myopathy and Duchenne muscular dystrophy points to osmoregulation as a contributing pathogenic mechanism.

Alongside well-known nuclear factor κB (NFκB) and its associated cytokine networks, nuclear factor of activated T cells 5 (NFAT5), the master regulator of cellular osmoprotective programs, comes forward as an inflammatory regulator. To gain insight into its yet unexplored role in muscle disease, we studied the expression of NFAT5 target proteins involved in osmolyte accumulation: aldose reductase (AR), taurine transporter (TauT), and sodium myo-inositol co-transporter (SMIT). We analyzed idiopathic inflammatory myopathy and Duchenne muscular dystrophy muscle biopsies and myotubes in culture, using immunohistochemistry, immunofluorescence, and western blotting. We report that the level of constitutive AR was upregulated in patients, most strongly so in Duchenne muscular dystrophy. TauT and SMIT expression levels were induced in patients' muscle fibers, mostly representing regenerating and atrophic fibers. In dermatomyositis, strong staining for AR, TauT, and SMIT in atrophic perifascicular fibers was accompanied by staining for other molecular NFAT5 targets, including chaperones, chemokines, and inducible nitric oxide synthase. In these fibers, NFAT5 and NFκB p65 staining coincided, linking both transcription factors with this important pathogenic hallmark. In sporadic inclusion body myositis, SMIT localized to inclusions inside muscle fibers. In addition, SMIT was expressed by a substantial subset of muscle-infiltrating macrophages and T cells in patient biopsies. Our results indicate that osmolyte pathways may contribute to normal muscle functioning, and that activation of AR, TauT, and SMIT in muscle inflammation possibly contributes to the tissue's failing program of damage control.

Loss of function of glucocerebrosidase GBA2 is responsible for motor neuron defects in hereditary spastic paraplegia.

Spastic paraplegia 46 refers to a locus mapped to chromosome 9 that accounts for a complicated autosomal-recessive form of hereditary spastic paraplegia (HSP). With next-generation sequencing in three independent families, we identified four different mutations in GBA2 (three truncating variants and one missense variant), which were found to cosegregate with the disease and were absent in controls. GBA2 encodes a microsomal nonlysosomal glucosylceramidase that catalyzes the conversion of glucosylceramide to free glucose and ceramide and the hydrolysis of bile acid 3-O-glucosides. The missense variant was also found at the homozygous state in a simplex subject in whom no residual glucocerebrosidase activity of GBA2 could be evidenced in blood cells, opening the way to a possible measurement of this enzyme activity in clinical practice. The overall phenotype was a complex HSP with mental impairment, cataract, and hypogonadism in males associated with various degrees of corpus callosum and cerebellar atrophy on brain imaging. Antisense morpholino oligonucleotides targeting the zebrafish GBA2 orthologous gene led to abnormal motor behavior and axonal shortening/branching of motoneurons that were rescued by the human wild-type mRNA but not by applying the same mRNA containing the missense mutation. This study highlights the role of ceramide metabolism in HSP pathology.

Diagnostic value of MIBG cardiac scintigraphy for differential dementia diagnosis.

OBJECTIVE: Iodine-123 metaiodobenzylguanidine (MIBG) cardiac scintigraphy has shown the potential to discriminate dementia with Lewy bodies (DLB) from Alzheimer's disease (AD). However, these studies did not reflect clinical practice, as patients with ischemic heart disease, heart failure, diabetes mellitus, arterial hypertension, and hyperlipidemia and patients treated with antidepressants like trazodone were excluded. METHODS: This study aimed to evaluate the use of MIBG cardiac scintigraphy to diagnose DLB in clinical practice. Moreover, the potential diagnostic value of MIBG cardiac scintigraphy in patients with clinically ambiguous dementia diagnosis (DLB versus AD) was tested. Eighty-five patients with a possible clinical diagnosis of DLB entered the study. MIBG uptake was determined by calculating the heart-to-mediastinum-uptake ratio (H/M). RESULTS: The average H/M ratio was 1.42 ± 0.35. The number of core features for DLB and the H/M ratio were negatively correlated (p = 0.001; r = -0.360). With an H/M ratio cutoff of 1.68 in 20 patients with clinically ambiguous dementia diagnoses (DLB versus AD) at the moment of MIBG cardiac scintigraphy, 95% (19/20) of the patients were correctly classified as compared with clinical or definite diagnosis at follow-up, with sensitivity and specificity values for diagnosing DLB of 100% (16/16) and 75% (3/4), respectively. The H/M ratio was influenced only by age (p = 0.046; r = -0.217) and gender (p = 0.024) and not by any other variable studied. CONCLUSIONS: The MIBG cardiac scintigraphy H/M ratio is a possible diagnostic biomarker for DLB in routine clinical practice and might have an added diagnostic value in case of doubt between DLB and AD.

Common pathobiochemical hallmarks of progranulin-associated frontotemporal lobar degeneration and neuronal ceroid lipofuscinosis.

Heterozygous loss-of-function mutations in the progranulin (GRN) gene and the resulting reduction of GRN levels is a common genetic cause for frontotemporal lobar degeneration (FTLD) with accumulation of TAR DNA-binding protein (TDP)-43. Recently, it has been shown that a complete GRN deficiency due to a homozygous GRN loss-of-function mutation causes neuronal ceroid lipofuscinosis (NCL), a lysosomal storage disorder. These findings suggest that lysosomal dysfunction may also contribute to some extent to FTLD. Indeed, Grn(-/-) mice recapitulate not only pathobiochemical features of GRN-associated FTLD-TDP (FTLD-TDP/GRN), but also those which are characteristic for NCL and lysosomal impairment. In Grn(-/-) mice the lysosomal proteins cathepsin D (CTSD), LAMP (lysosomal-associated membrane protein) 1 and the NCL storage components saposin D and subunit c of mitochondrial ATP synthase (SCMAS) were all found to be elevated. Moreover, these mice display increased levels of transmembrane protein (TMEM) 106B, a lysosomal protein known as a risk factor for FTLD-TDP pathology. In line with a potential pathological overlap of FTLD and NCL, Ctsd(-/-) mice, a model for NCL, show elevated levels of the FTLD-associated proteins GRN and TMEM106B. In addition, pathologically phosphorylated TDP-43 occurs in Ctsd(-/-) mice to a similar extent as in Grn(-/-) mice. Consistent with these findings, some NCL patients accumulate pathologically phosphorylated TDP-43 within their brains. Based on these observations, we searched for pathological marker proteins, which are characteristic for NCL or lysosomal impairment in brains of FTLD-TDP/GRN patients. Strikingly, saposin D, SCMAS as well as the lysosomal proteins CTSD and LAMP1/2 are all elevated in patients with FTLD-TDP/GRN. Thus, our findings suggest that lysosomal storage disorders and GRN-associated FTLD may share common features.

TMEM106B is a genetic modifier of frontotemporal lobar degeneration with C9orf72 hexanucleotide repeat expansions.

Hexanucleotide repeat expansions in chromosome 9 open reading frame 72 (C9orf72) have recently been linked to frontotemporal lobar degeneration (FTLD) and amyotrophic lateral sclerosis, and may be the most common genetic cause of both neurodegenerative diseases. Genetic variants at TMEM106B influence risk for the most common neuropathological subtype of FTLD, characterized by inclusions of TAR DNA-binding protein of 43 kDa (FTLD-TDP). Previous reports have shown that TMEM106B is a genetic modifier of FTLD-TDP caused by progranulin (GRN) mutations, with the major (risk) allele of rs1990622 associating with earlier age at onset of disease. Here, we report that rs1990622 genotype affects age at death in a single-site discovery cohort of FTLD patients with C9orf72 expansions (n = 14), with the major allele correlated with later age at death (p = 0.024). We replicate this modifier effect in a 30-site international neuropathological cohort of FTLD-TDP patients with C9orf72 expansions (n = 75), again finding that the major allele associates with later age at death (p = 0.016), as well as later age at onset (p = 0.019). In contrast, TMEM106B genotype does not affect age at onset or death in 241 FTLD-TDP cases negative for GRN mutations or C9orf72 expansions. Thus, TMEM106B is a genetic modifier of FTLD with C9orf72 expansions. Intriguingly, the genotype that confers increased risk for developing FTLD-TDP (major, or T, allele of rs1990622) is associated with later age at onset and death in C9orf72 expansion carriers, providing an example of sign epistasis in human neurodegenerative disease.

Increased CSF α-synuclein levels in Alzheimer's disease: correlation with tau levels.

BACKGROUND: Given the difficult clinical differential diagnosis between Alzheimer's disease (AD) and dementia with Lewy bodies (DLB), growing interest resulted in research on α-synuclein as a potential cerebrospinal fluid biomarker (CSF) for synucleinopathies. METHODS: CSF α-synuclein-140 concentrations were determined by a prototype xMAP™ bead-based assay (Innogenetics NV, Belgium). In addition, CSF amyloid ß1-42 (Aß1-42), total tau (T-tau), and phosphorylated tau (P-tau181P) levels were determined. RESULTS: CSF α-synuclein levels were higher in AD patients as compared with cognitively healthy controls (P=.019) and patients with synucleinopathies (P<.001). CSF α-synuclein levels were correlated with T-tau (P<.001) and P-tau181P (P<.001) levels in autopsy-confirmed AD patients. A diagnostic algorithm using α-synuclein and P-tau181P discriminated neuropathologically confirmed AD from DLB patients, resulting in sensitivity and specificity values of 85% and 81%, respectively. CONCLUSION: Because CSF α-synuclein levels were significantly higher in AD as compared with synucleinopathies, α-synuclein might have a value as a biomarker for differential dementia diagnosis.

Mutations in dynamin 2 cause dominant centronuclear myopathy.

Autosomal dominant centronuclear myopathy is a rare congenital myopathy characterized by delayed motor milestones and muscular weakness. In 11 families affected by centronuclear myopathy, we identified recurrent and de novo missense mutations in the gene dynamin 2 (DNM2, 19p13.2), which encodes a protein involved in endocytosis and membrane trafficking, actin assembly and centrosome cohesion. The transfected mutants showed reduced labeling in the centrosome, suggesting that DNM2 mutations might cause centronuclear myopathy by interfering with centrosome function.

Mutant small heat-shock protein 27 causes axonal Charcot-Marie-Tooth disease and distal hereditary motor neuropathy.

Charcot-Marie-Tooth disease (CMT) is the most common inherited neuromuscular disease and is characterized by considerable clinical and genetic heterogeneity. We previously reported a Russian family with autosomal dominant axonal CMT and assigned the locus underlying the disease (CMT2F; OMIM 606595) to chromosome 7q11-q21 (ref. 2). Here we report a missense mutation in the gene encoding 27-kDa small heat-shock protein B1 (HSPB1, also called HSP27) that segregates in the family with CMT2F. Screening for mutations in HSPB1 in 301 individuals with CMT and 115 individuals with distal hereditary motor neuropathies (distal HMNs) confirmed the previously observed mutation and identified four additional missense mutations. We observed the additional HSPB1 mutations in four families with distal HMN and in one individual with CMT neuropathy. Four mutations are located in the Hsp20-alpha-crystallin domain, and one mutation is in the C-terminal part of the HSP27 protein. Neuronal cells transfected with mutated HSPB1 were less viable than cells expressing the wild-type protein. Cotransfection of neurofilament light chain (NEFL) and mutant HSPB1 resulted in altered neurofilament assembly in cells devoid of cytoplasmic intermediate filaments.

The genetics and neuropathology of frontotemporal lobar degeneration.

Frontotemporal lobar degeneration (FTLD) is a heterogeneous group of disorders characterized by disturbances of behavior and personality and different types of language impairment with or without concomitant features of motor neuron disease or parkinsonism. FTLD is characterized by atrophy of the frontal and anterior temporal brain lobes. Detailed neuropathological studies have elicited proteinopathies defined by inclusions of hyperphosphorylated microtubule-associated protein tau, TAR DNA-binding protein TDP-43, fused-in-sarcoma or yet unidentified proteins in affected brain regions. Rather than the type of proteinopathy, the site of neurodegeneration correlates relatively well with the clinical presentation of FTLD. Molecular genetic studies identified five disease genes, of which the gene encoding the tau protein (MAPT), the growth factor precursor gene granulin (GRN), and C9orf72 with unknown function are most frequently mutated. Rare mutations were also identified in the genes encoding valosin-containing protein (VCP) and charged multivesicular body protein 2B (CHMP2B). These genes are good markers to distinguish underlying neuropathological phenotypes. Due to the complex landscape of FTLD diseases, combined characterization of clinical, imaging, biological and genetic biomarkers is essential to establish a detailed diagnosis. Although major progress has been made in FTLD research in recent years, further studies are needed to completely map out and correlate the clinical, pathological and genetic entities, and to understand the underlying disease mechanisms. In this review, we summarize the current state of the rapidly progressing field of genetic, neuropathological and clinical research of this intriguing condition.

Upregulation of chemokines and their receptors in Duchenne muscular dystrophy: potential for attenuation of myofiber necrosis.

INTRODUCTION: In Duchenne muscular dystrophy (DMD), the infiltration of skeletal muscle by immune cells aggravates disease, yet the precise mechanisms behind these inflammatory responses remain poorly understood. Chemotactic cytokines, or chemokines, are considered essential recruiters of inflammatory cells to the tissues. METHODS: We assayed chemokine and chemokine receptor expression in DMD muscle biopsies (n = 9, average age 7 years) using immunohistochemistry, immunofluorescence, and in situ hybridization. RESULTS: CXCL1, CXCL2, CXCL3, CXCL8, and CXCL11, absent from normal muscle fibers, were induced in DMD myofibers. CXCL11, CXCL12, and the ligand-receptor couple CCL2-CCR2 were upregulated on the blood vessel endothelium of DMD patients. CD68(+) macrophages expressed high levels of CXCL8, CCL2, and CCL5. CONCLUSIONS: Our data suggest a possible beneficial role for CXCR1/2/4 ligands in managing muscle fiber damage control and tissue regeneration. Upregulation of endothelial chemokine receptors and CXCL8, CCL2, and CCL5 expression by cytotoxic macrophages may regulate myofiber necrosis.

Null mutations in progranulin cause ubiquitin-positive frontotemporal dementia linked to chromosome 17q21.

Frontotemporal dementia (FTD) with ubiquitin-immunoreactive neuronal inclusions (both cytoplasmic and nuclear) of unknown nature has been linked to a chromosome 17q21 region (FTDU-17) containing MAPT (microtubule-associated protein tau). FTDU-17 patients have consistently been shown to lack a tau-immunoreactive pathology, a feature characteristic of FTD with parkinsonism linked to mutations in MAPT (FTDP-17). Furthermore, in FTDU-17 patients, mutations in MAPT and genomic rearrangements in the MAPT region have been excluded by both genomic sequencing and fluorescence in situ hybridization on mechanically stretched chromosomes. Here we demonstrate that FTDU-17 is caused by mutations in the gene coding for progranulin (PGRN), a growth factor involved in multiple physiological and pathological processes including tumorigenesis. Besides the production of truncated PGRN proteins due to premature stop codons, we identified a mutation within the splice donor site of intron 0 (IVS0 + 5G > C), indicating loss of the mutant transcript by nuclear degradation. The finding was made within an extensively documented Belgian FTDU-17 founder family. Transcript and protein analyses confirmed the absence of the mutant allele and a reduction in the expression of PGRN. We also identified a mutation (c.3G > A) in the Met1 translation initiation codon, indicating loss of PGRN due to lack of translation of the mutant allele. Our data provide evidence that PGRN haploinsufficiency leads to neurodegeneration because of reduced PGRN-mediated neuronal survival. Furthermore, in a Belgian series of familial FTD patients, PGRN mutations were 3.5 times more frequent than mutations in MAPT, underscoring a principal involvement of PGRN in FTD pathogenesis.

Neuropathology in classical and variant ataxia-telangiectasia.

Ataxia-telangiectasia (A-T) is classically characterized by progressive neurodegeneration, oculocutaneous telangiectasia, immunodeficiency and elevated α-fetoprotein levels. Some patients, classified as variant A-T, exhibit a milder clinical course. In the latter patients extrapyramidal symptoms, instead of cerebellar ataxia, tend to be the dominating feature and other classical disease hallmarks, like telangiectasia, appear later or even may be absent. Some patients with variant disease have clinically pronounced anterior horn cell degeneration. Neuropathological studies of genetically proven A-T patients are lacking. The aims of our study were to describe the neuropathology of three A-T patients; in two of them the diagnosis was genetically confirmed. The neuropathological findings were compared with those of all known published autopsy findings in A-T patients up to now. Two classical A-T patients aged 19 and 22 and a 33-year-old patient with variant disease were autopsied. In line with previous reports, our patients had severe cerebellar atrophy, less pronounced degeneration of the dentate nucleus and inferior olive, degeneration of the posterior columns and neurogenic muscular atrophy. In addition, all three had anterior horn cell degeneration, which was most prominent at the lumbar level. Compared to the literature, the degenerative changes in the brain stem of the variant A-T patient were somewhat less than anticipated for his age. Degenerative changes in the cerebellum and spinal cord were comparable with those in the literature. Progeric changes were lacking. In conclusion, compared to classical A-T, the variant A-T patient showed essentially the same, only slightly milder neuropathological abnormalities, except for anterior horn degeneration.

Improved Alzheimer's Disease versus Frontotemporal Lobar Degeneration Differential Diagnosis Combining EEG and Neurochemical Biomarkers: A Pilot Study.

BACKGROUND: Distinguishing between Alzheimer's disease (AD) and frontotemporal lobar degeneration (FTLD) results in poor diagnostic accuracy. OBJECTIVE: To investigate the utility of electroencephalography (EEG)-based biomarkers in comparison and in addition to established cerebrospinal fluid (CSF) biomarkers in the AD versus FTLD differential diagnosis. METHODS: The study cohort comprised 37 AD and 30 FTLD patients, of which 17 AD and 9 FTLD patients had definite diagnoses. All participants had CSF neurochemical (NCM) biomarker analyses (Aß1-42, T-tau, P-tau181, and Nf-L) and underwent 19-channel resting-state EEG. From the EEG spectra, dominant frequency peaks were extracted in four regions resulting in four dominant frequencies. This produced eight features (4 NCM + 4 EEG). RESULTS: When NCM and EEG markers were combined, the diagnostic accuracy increased significantly. In the whole group, the accuracy went up from 79% (NCM) to almost 82%, while in the definite group only, it went up from around 85% to almost 95%. Two differences in the occurrence of the dominant EEG frequency were discovered: people lacking a clear dominant peak almost all had definite AD, while people with two peaks more often had FTLD. CONCLUSION: Combining EEG with NCM biomarkers resulted in differential diagnostic accuracies of 82% in clinically diagnosed AD and FTD patients and of 95% in patients having a definite diagnosis, which was significantly better than with EEG or NCM biomarkers alone. This suggests that NCM and EEG markers are complementary, revealing different aspects of the disease and therefore confirms again their relevance in developing additional diagnosis tools.

DNAJB2 expression in normal and diseased human and mouse skeletal muscle.

DNAJB2, a co-chaperone regulator of Hsp70 that is expressed principally in the nervous system, has been recently reported to be up-regulated in human skeletal muscle during its recovery from damage. Here we identified DNAJB2 expression in regenerating fibers in skeletal muscles of the dystrophic mdx mouse and patients with Duchenne muscular dystrophy. Surprisingly, in both dystrophic and control mice and patients, DNAJB2 was also expressed in non-regenerating fibers at the postsynaptic side of the neuromuscular junction. DNAJB2 functions as an adaptor molecule for the evacuation and degradation of proteins through the ubiquitin-proteasome system, and overexpression of DNAJB2 in models of the neurodegenerative disease spinobulbar muscular atrophy was shown to result in the reduction of protein inclusions. We therefore studied the possible relation of DNAJB2 expression to protein inclusion formation in skeletal muscle in biopsies of several muscle pathologies associated with protein aggregation and found in all of them a strong immunoreactivity with anti-DNAJB2 in aggregates and vacuoles. We conclude that DNAJB2 is expressed in mouse and human skeletal muscle at the neuromuscular junction of normal fibers, in the cytoplasm and membrane of regenerating fibers, and in protein aggregates and vacuoles in protein aggregate myopathies. Therefore, we propose a role for DNAJB2 in protein turnover processes in skeletal muscle.

Hippocampal Sclerosis in Frontotemporal Dementia: When Vascular Pathology Meets Neurodegeneration.

Hippocampal sclerosis (HS) is a common neuropathological finding and has been associated with advanced age, TDP-43 proteinopathy, and cerebrovascular pathology. We analyzed neuropathological data of an autopsy cohort of early-onset frontotemporal dementia patients. The study aimed to determine whether in this cohort HS was related to TDP-43 proteinopathy and whether additional factors could be identified. We examined the relationship between HS, proteinopathies in frontotemporal cortices and hippocampus, Alzheimer disease, cerebrovascular changes, and age. We confirmed a strong association between HS and hippocampal TDP-43, whereas there was a weaker association between HS and frontotemporal lobar degeneration with TDP-43 pathology (FTLD-TDP). Nearly all of the FTLD-TDP cases had TDP-43 pathology in the hippocampus. HS was present in all FTLD-TDP type D cases, in 50% of the FTLD-TDP A cohort and in 6% of the FTLD-TDP B cohort. Our data also showed a significant association between HS and vascular changes. We reviewed the literature on HS and discuss possible pathophysiological mechanisms between TDP-43 pathology, cerebrovascular disease, and HS. Additionally, we introduced a quantitative neuronal cell count in CA1 to objectify the semiquantitative visual appreciation of HS.