[Show abstract][Hide abstract] ABSTRACT: Background:
The hereditary spastic paraplegias (HSPs) are rare neurodegenerative gait disorders which are genetically highly heterogeneous. For each single form, eventual consideration of therapeutic strategies requires an understanding of the mechanism by which mutations confer pathogenicity. SPG8 is a dominantly inherited HSP, and associated with rather early onset and rapid progression. A total of nine mutations in KIAA0196, which encodes the WASH regulatory complex (SHRC) member strumpellin, have been reported in SPG8 patients so far. Based on biochemical and cell biological approaches, they have been suggested to act via loss of function-mediated haploinsufficiency.
We generated a deletion-based knockout allele for E430025E21Rik, i.e. the murine homologue of KIAA0196. The consequences on mRNA and protein levels were analyzed by qPCR and Western-blotting, respectively. Motor performance was evaluated by the foot-base angle paradigm. Axon outgrowth and relevant organelle compartments were investigated in primary neuron cultures and primary fibroblast cultures, respectively. A homemade multiplex ligation-dependent probe amplification assay enabling identification of large inactivating KIAA0196 deletion alleles was applied to DNA from 240 HSP index patients.
Homozygous but not heterozygous mice showed early embryonic lethality. No transcripts from the knockout allele were detected, and the previously suggested compensation by the wild-type allele upon heterozygosity was disproven. mRNA expression of genes encoding other SHRC members was unaltered, while there was evidence for reduced SHRC abundance at protein level. We did, however, neither observe HSP-related in vivo and ex vivo phenotypes, nor alterations affecting endosomal, lysosomal, or autophagic compartments. KIAA0196 copy number screening excluded large inactivating deletion mutations in HSP patients. The consequences of monoallelic KIAA0196/E430025E21Rik activation thus differ from those observed for dominant HSP genes for which a loss-of-function mechanism is well established.
Our data do not support the current view that heterozygous loss of strumpellin/SHRC function leads to haploinsufficiency and, in turn, to HSP. The lethality of homozygous knockout mice, i.e. the effect of complete loss of function, also argues against a dominant negative effect of mutant on wild-type strumpellin in patients. Toxic gain-of-function represents a potential alternative explanation. Confirmation of this therapeutically relevant hypothesis in vivo, however, will require availability of appropriate knockin models.
[Show abstract][Hide abstract] ABSTRACT: Mutations in the SPG7 gene are the most frequent cause of autosomal recessive hereditary spastic paraplegias and spastic ataxias. Ala510Val is the most common SPG7 mutation, with a frequency of up to 1% in the general population. Here we report the clinical, genetic, and neuropathological findings in a homozygous Ala510Val SPG7 case with spastic ataxia. Neuron loss with associated gliosis was found in the inferior olivary nucleus, the dentate nucleus of the cerebellum, the substantia nigra and the basal nucleus of Meynert. Neurofilament and/or paraplegin accumulation was observed in swollen neurites in the cerebellar and cerebral cortex. This case also showed subcortical τ-pathology in an unique distribution pattern largely restricted to the brainstem. α-synuclein containing Lewy bodies (LBs) were observed in the brainstem and the cortex, compatible with a limbic pattern of Braak LB-Disease stage 4. Taken together, this case shows that the spectrum of pathologies in SPG7 can include neuron loss of the dentate nucleus and the inferior olivary nucleus as well as neuritic pathology. The progressive supranuclear palsy-like brainstem predominant pattern of τ pathology and α-synuclein containing Lewy bodies in our SPG7 cases may be either coincidental or related to SPG7 in addition to neuron loss and neuritic pathology.
International Journal of Molecular Sciences 10/2015; 16(10):25050-25066. DOI:10.3390/ijms161025050 · 2.86 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The spinocerebellar ataxias types 2 (SCA2) and 3 (SCA3) are autosomal dominantly inherited cerebellar ataxias which are caused by CAG trinucleotide repeat expansions in the coding regions of the disease-specific genes. Although previous post-mortem studies repeatedly revealed a consistent neurodegeneration of the dopaminergic substantia nigra in patients with SCA2 and with SCA3, parkinsonian motor features evolve only rarely. As the pathophysiological mechanism how SCA2 and SCA3 patients do not exhibit parkinsonism is still enigmatic, we performed a positron emission tomography and a post-mortem study of two independent cohorts of SCA2 and SCA3 patients with and without parkinsonian features. Positron emission tomography revealed a significant reduction of dopamine transporter levels in the striatum as well as largely unaffected postsynaptic striatal D2 receptors. In spite of this remarkable pathology in the motor mesostriatal pathway, only 4 of 19 SCA2 and SCA3 patients suffered from parkinsonism. The post-mortem investigation revealed, in addition to an extensive neuronal loss in the dopaminergic substantia nigra of all patients with spinocerebellar ataxia, a consistent affection of the thalamic ventral anterior and ventral lateral nuclei, the pallidum and the cholinergic pedunculopontine nucleus. With the exception of a single patient with SCA3 who suffered from parkinsonian motor features during his lifetime, the subthalamic nucleus underwent severe neuronal loss, which was clearly more severe in its motor territory than in its limbic or associative territories. Our observation that lesions of the motor territory of the subthalamic nucleus were consistently associated with the prevention of parkinsonism in our SCA2 and SCA3 patients matches the clinical experience that selective targeting of the motor territory of the subthalamic nucleus by focal lesions or deep brain stimulation can ameliorate parkinsonian motor features and is likely to counteract the manifestation of parkinsonism in SCA2 and SCA3 despite a severe neurodegeneration of the dopaminergic substantia nigra.
[Show abstract][Hide abstract] ABSTRACT: Niemann-Pick disease type C (NP-C) is a rare autosomal-recessive neurodegenerative disease featuring pleiotropic neurological, psychiatric and visceral manifestations. Since many of the adult manifestations can be non-specific or missed, NP-C often goes undetected in adult-onset patients. Here we hypothesized that targeted high-throughput sequencing allows identifying NP-C patients among subjects with unexplained early-onset ataxia (EOA) and, moreover, that this population is enriched for NPC1 mutations. From 204 consecutive EOA patients, all 108 subjects with an established diagnosis were removed (including 4 NPC1 patients), yielding a target cohort of 96 subjects with unexplained EOA, but without primary suspicion of NP-C. This cohort was investigated for NPC1/NPC2 mutations using a high-coverage HaloPlex gene panel including 122 ataxia genes. Among 96 samples, we identified 4 known NPC1 mutations, 3 novel NPC1 missense variants of uncertain significance (VUS) and 1 novel NPC2 missense VUS. The total mutant allele frequency (8/192 = 4.17 %) was significantly enriched compared with control population data (1.57 %; p = 0.011). Two NPC1-positive patients were identified (both with non-specific incipient clinical features), giving a NPC1 patient frequency of 2/96 = 2.1 % in unexplained EOA and of 6/204 = 2.9 % in the total EOA series. NPC1 mutations are substantially enriched in unexplained EOA, demonstrating EOA as a risk-group for NP-C disease. Targeted high-throughput sequencing allows to identify also those NP-C patients with non-specific conditions where the diagnosis has initially been missed. This method does not require having considered NP-C during differential diagnosis, but allows identification of NP-C as part of the default analysis.
Journal of Neurology 09/2015; DOI:10.1007/s00415-015-7889-y · 3.38 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Background:
Spinocerebellar ataxias are dominantly inherited neurodegenerative diseases. As potential treatments for these diseases are being developed, precise knowledge of their natural history is needed. We aimed to study the long-term disease progression of the most common spinocerebellar ataxias: SCA1, SCA2, SCA3, and SCA6. Furthermore, we aimed to establish the order and occurrence of non-ataxia symptoms, and identify predictors of disease progression.
In this longitudinal cohort study (EUROSCA), we enrolled men and women with positive genetic testing for SCA1, SCA2, SCA3, or SCA6 and with progressive, otherwise unexplained ataxia who were aged 18 years or older from 17 ataxia referral centres in ten European countries. Patients were seen every year for 3 years, and at irregular intervals thereafter. The primary outcome was the scale for the assessment and rating of ataxia (SARA), and the inventory of non-ataxia signs (INAS). We used linear mixed models to analyse progression. To account for dropouts, we applied a pattern-mixture model. This study is registered with ClinicalTrials.gov, number NCT02440763.
Between July 1, 2005, and Aug 31, 2006, 526 patients with SCA1, SCA2, SCA3, or SCA6 were enrolled. We analysed data for 462 patients with at least one follow-up visit. Median observation time was 49 months (IQR 35-72). SARA progression data were best fitted with a linear model in all genotypes. Annual SARA score increase was 2·11 (SE 0·12) in patients with SCA1, 1·49 (0·07) in patients with SCA2, 1·56 (0·08) in patients with SCA3, and 0·80 (0·09) in patients with SCA6. The increase of the number of non-ataxia signs reached a plateau in SCA1, SCA2, and SCA3. In patients with SCA6, the number of non-ataxia symptoms increased linearly, but more slowly than in patients with SCA1, SCA2, and SCA3 (p<0·0001). Factors that were associated with faster progression of the SARA score were short duration of follow-up (p=0·0179), older age at inclusion (0.04 [SE 0·02] per additional year; p=0·0476), and longer repeat expansions (0·06 [SE 0·02] per additional repeat unit; p=0·0128) in SCA1, short duration of follow-up (p<0·0001), lower age at onset (-0·02 [SE 0·01] per additional year; p=0·0014), and lower baseline SARA score (-0·02 [SE 0·01] per additional SARA point; p=0·0083) in SCA2, and lower baseline SARA score (-0·03 [SE 0·01] per additional SARA point; p=0·0195) in SCA6. In SCA3, we did not identify factors that affected progression of the SARA score.
Our study provides quantitative data on the progression of the most common spinocerebellar ataxias based on a follow-up period that exceeds those of previous studies. Our data could prove useful for sample size calculation and patient stratification in interventional trials.
EU FP6 (EUROSCA), German Ministry of Education and Research (BMBF; GeneMove), Polish Ministry of Science, EU FP7 (NEUROMICS).
The Lancet Neurology 09/2015; 14(11). DOI:10.1016/S1474-4422(15)00202-1 · 21.90 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Hereditary spastic paraplegias (HSP) are a group of clinically and genetically heterogeneous disorders with the hallmark of progressive spastic gait disturbance. We used advanced neuroimaging to identify brain regions involved in SPG4, the most common HSP genotype. Additionally, we analyzed correlations between imaging and clinical findings. We performed 3T MRI scans including isotropic high-resolution 3D T1, T2-FLAIR, and DTI sequences in 15 adult patients with genetically confirmed SPG4 and 15 age- and sex-matched healthy controls. Brain volume loss of gray and white matter was evaluated through voxel-based morphometry (VBM) for supra- and infratentorial regions separately. DTI maps of axial diffusivity (AD), radial diffusivity (RD), mean diffusivity (MD), fractional anisotropy (FA), and measured anisotropy (MA1) were analyzed through tract-based special statistics (TBSS). VBM and TBSS revealed a widespread affection of gray and white matter in SPG4 including the corpus callosum, medio-dorsal thalamus, parieto-occipital regions, upper brainstem, cerebellum, and corticospinal tract. Significant correlations with correlation coefficients r > 0.6 between clinical data and DTI findings could be demonstrated for disease duration and disease severity as assessed by the spastic paraplegia rating scale for the pontine crossing tract (AD) and the corpus callosum (RD and FA). Imaging also provided evidence that SPG4 underlies a primarily axonal rather than demyelinating damage in accordance with post-mortem data. DTI is an attractive tool to assess subclinical affection in SPG4. The correlation of imaging findings with disease duration and severity suggests AD, RD, and FA as potential progression markers in interventional studies.
Journal of Neurology 06/2015; 262(8). DOI:10.1007/s00415-015-7791-7 · 3.38 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Spinocerebellar ataxias (SCAs) are characterized by autosomal dominantly inherited progressive ataxia but are clinically heterogeneous due to variable involvement of non-cerebellar parts of the nervous system. Non-cerebellar symptoms contribute significantly to the burden of SCAs, may guide the clinician to the underlying genetic subtype, and might be useful markers to monitor disease. Peripheral neuropathy is frequently observed in SCA, but subtype-specific features and subclinical manifestations have rarely been evaluated. We performed a multicenter nerve conduction study with 162 patients with genetically confirmed SCA1, SCA2, SCA3, and SCA6. The study proved peripheral nerves to be involved in the neurodegenerative process in 82 % of SCA1, 63 % of SCA2, 55 % of SCA3, and 22 % of SCA6 patients. Most patients of all subtypes revealed affection of both sensory and motor fibers. Neuropathy was most frequently of mixed type with axonal and demyelinating characteristics in all SCA subtypes. However, nerve conduction velocities of SCA1 patients were slower compared to other genotypes. SCA6 patients revealed less axonal damage than patients with other subtypes. No influence of CAG repeat length or biometric determinants on peripheral neuropathy could be identified in SCA1, SCA3, and SCA6. In SCA2, earlier onset and more severe ataxia were associated with peripheral neuropathy. We proved peripheral neuropathy to be a frequent site of the neurodegenerative process in all common SCA subtypes. Since damage to peripheral nerves is readily assessable by electrophysiological means, nerve conduction studies should be performed in a longitudinal approach to assess these parameters as potential progression markers.
The Cerebellum 06/2015; DOI:10.1007/s12311-015-0684-6 · 2.72 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Epileptic encephalopathies are a phenotypically and genetically heterogeneous group of severe epilepsies accompanied by intellectual disability and other neurodevelopmental features –6. Using next-generation sequencing, we identified four different de novo mutations in KCNA2, encoding the potassium channel K V .2, in six isolated patients with epileptic encephalopathy (one mutation recurred three times independently). Four individuals presented with febrile and multiple afebrile, often focal seizure types, multifocal epileptiform discharges strongly activated by sleep, mild to moderate intellectual disability, delayed speech development and sometimes ataxia. Functional studies of the two mutations associated with this phenotype showed almost complete loss of function with a dominant-negative effect. Two further individuals presented with a different and more severe epileptic encephalopathy phenotype. They carried mutations inducing a drastic gain-of-function effect leading to permanently open channels. These results establish KCNA2 as a new gene involved in human neurodevelopmental disorders through two different mechanisms, predicting either hyperexcitability or electrical silencing of K V .2-expressing neurons. Many of the voltage-gated potassium channels (K V 1–K V 12) are expressed in the central nervous system (CNS), having an important role in neuronal excitability and neurotransmitter release 7. Mutations in potassium channel–encoding genes cause different neurological diseases, including benign familial neonatal seizures (KCNQ2, encoding K V 7.2; KCNQ3, encoding K V 7.3) 8–10 , neonatal epileptic encephalopathy (KCNQ2) 11,12 , episodic ataxia type 1 (EA1) (KCNA1, encoding K V 1.1) 13 and peripheral nerve hyperexcitability (KCNA1, KCNQ2) 13–15. In addition, antibodies against K V 1.1 or associated proteins such as contactin-associated protein 2 (CASPR2) or leucine-rich, glioma-inactivated 1 (LGI1) cause limbic encephalitis or neuromyotonia 16. Therefore, potassium channel genes represent interesting candidates for neurodevelopmental disorders. To identify mutations in presumed genetic forms of epilepsy, we designed a targeted resequencing panel 17 comprising 265 known and 220 candidate genes for epilepsy (Supplementary Table 1). Screening a pilot cohort of 33 patients, we identified mutations in known epilepsy-related genes in 16 cases 17. We evaluated the remaining 17 cases for mutations in candidate genes (Supplementary Note), which led to the detection of a heterozygous de novo mutation in KCNA2, c.1214C>T (encoding p.Pro405Leu), affecting the highly conserved pore domain of the voltage-gated potassium channel K V 1.2 (NM_004974, CCDS827). This mutation was not present in control databases (1000 Genomes Project, Exome Variant Server (EVS), dbSNP138 or the Exome Aggregation Consortium (ExAC) database). The affected female (patient 1) carrying this mutation had unre-markable early development until the onset of epilepsy at 17 months of age. The phenotype included febrile and afebrile alternating hemiclonic seizures and status epilepticus, reminiscent of Dravet syndrome. The electroencephalogram (EEG) showed multifocal spikes with marked activation during sleep. After seizure onset, ataxia and delay of psychomotor and language development became apparent. She had postnatal short stature, growth hormone deficiency and hypothyroidism. Seizures and ataxia responded poorly to antiepileptic drugs (topiramate, oxcarbazepine, valproic acid and bromide), including acetazolamide (known to be effective in EA1 caused by mutations in KCNA1; ref. 18). At last follow-up at 8 years of age, she had remained seizure free for the past 6 months without previous change of medication. We identified further KCNA2 mutations in several parallel studies (Supplementary Fig. 1). First, we performed whole-exome sequenc-ing in 86 parent-offspring trios with epileptic encephalopathy (31 with Dravet syndrome negative for mutations in SCN1A, 39 with myoclonic-atonic epilepsy (MAE) and 16 with electrical status epi-lepticus in slow-wave sleep (ESES)). Second, we performed panel sequencing (Supplementary Note) in 147 adults with a broad spectrum of epilepsy phenotypes associated with intellectual disability. Third, we performed whole-exome sequencing in an adult cohort of 10 independent trios with severe epilepsy and intellectual disability and whole-exome sequencing in another cohort of 12 independent, isolated index cases with early-onset ataxia and epilepsy. We identified six additional independent cases with previously unre-ported heterozygous KCNA2 variants (Table 1, Supplementary Fig. 2 and Supplementary Note). Patient 2 (initially classified as having MAE) carried the de novo mutation c.788T>C (encoding p.Ile263Thr). Patient 3 (intellectual disability with neonatal-onset focal epilepsy and cerebel-lar hypoplasia) carried the variant c.440G>A (encoding p.Arg147Lys), of unknown inheritance. We considered p.Arg147Lys to be a variant of unknown relevance because (i) it could not be confirmed as de novo, (ii) it was predicted to be benign using seven of nine prediction tools, (iii) a lysine occurs naturally at this position in Drosophila melanogaster and zebrafish, and (iv) the change did not show functional consequences (Supplementary Fig. 3, Supplementary Tables 1 and 2, and Supplementary Note). Patient 4 (initially classified as having Dravet
[Show abstract][Hide abstract] ABSTRACT: Epileptic encephalopathies are a phenotypically and genetically heterogeneous group of severe epilepsies accompanied by intellectual disability and other neurodevelopmental features. Using next-generation sequencing, we identified four different de novo mutations in KCNA2, encoding the potassium channel KV1.2, in six isolated patients with epileptic encephalopathy (one mutation recurred three times independently). Four individuals presented with febrile and multiple afebrile, often focal seizure types, multifocal epileptiform discharges strongly activated by sleep, mild to moderate intellectual disability, delayed speech development and sometimes ataxia. Functional studies of the two mutations associated with this phenotype showed almost complete loss of function with a dominant-negative effect. Two further individuals presented with a different and more severe epileptic encephalopathy phenotype. They carried mutations inducing a drastic gain-of-function effect leading to permanently open channels. These results establish KCNA2 as a new gene involved in human neurodevelopmental disorders through two different mechanisms, predicting either hyperexcitability or electrical silencing of KV1.2-expressing neurons.
[Show abstract][Hide abstract] ABSTRACT: Cerebellar ataxias comprise a large group of rare diseases characterized by degeneration of the cerebellum and its connections. Systematic neuropsychological studies are rare but found variable degrees of neuropsychiatric affection in most entities that have been analyzed. Dementia may occur in the autosomal dominantly inherited spinocerebellar ataxia type 17 (SCA17), the X-linked fragile X-associated tremor/ataxia syndrome (FXTAS), and several autosomal recessive ataxias with established metabolic changes like cerebrotendinous xanthomatosis (CTX), adult-onset Tay-Sachs disease, and Niemann-Pick type C disease. Dementia does not belong to the regular clinical spectrum of the most frequent sporadic adult-onset ataxia, multiple system atrophy of cerebellar type (MSA-C). Some early-onset ataxias of autosomal recessive inheritance lead to early cognitive impairment like infantile-onset spinocerebellar ataxia (IOSCA), Cayman cerebellar ataxia, and congenital disorder of glycosylation type 1A (CDG1a). Most of the other hereditary ataxias show variable degrees of focal neuropsychological deficits probably due to the cerebellar cognitive-affective syndrome. This syndrome is characterized by (1) disturbances of executive function, which includes deficient planning, set-shifting, abstract reasoning, working memory, and decreased verbal fluency; (2) impaired spatial cognition, including visual-spatial disorganization and impaired visual-spatial memory; (3) personality change characterized by flattening or blunting of affect and disinhibited or inappropriate behavior; and (4) linguistic difficulties, including dysprosodia, agrammatism, and mild anomia. However, in most patients, neuropsychological deficits do not interfere with intellectual competence in everyday life.
Neuropsychiatric Symptoms of Movement Disorders, 01/2015: pages 277-292;
[Show abstract][Hide abstract] ABSTRACT: Background
In Friedreich’s ataxia (FA) the genetically decreased expression of the mitochondrial protein frataxin leads to disturbance of the mitochondrial iron metabolism. Within the cerebellum the dentate nuclei (DN) are primarily affected. Histopathological studies show atrophy and accumulation of mitochondrial iron in DN. Dentate iron content has been suggested as a biomarker to measure the effects of siderophores/antioxidant treatment of FA. We assessed the iron content and the volume of DN in FA patients and controls based on ultra-high-field MRI (7 Tesla) images.
Fourteen FA patients (mean age 38.1 yrs) and 14 age- and gender-matched controls participated. Multi-echo gradient echo and susceptibility weighted imaging (SWI) sequences were acquired on a 7 T whole-body scanner. For comparison SWI images were acquired on a 1.5 T MR scanner. Volumes of the DN and cerebellum were assessed at 7 and 1.5 T, respectively. Parametric maps of T2 and T2* sequences were created and proton transverse relaxation rates were estimated as a measure of iron content.
In FA, the DN and the cerebellum were significantly smaller compared to controls. However, proton transverse relaxation rates of the DN were not significantly different between both groups.
Applying in vivo MRI methods we could demonstrate significant atrophy of the DN in the presence of normal iron content. The findings suggest that relaxation rates are not reliable biomarkers in clinical trials evaluating the potential effect of FA therapy.
[Show abstract][Hide abstract] ABSTRACT: Spinocerebellar ataxia 36 (SCA36) is an autosomal-dominant neurodegenerative disorder caused by a large (>650) hexanucleotide GGCCTG repeat expansion in the first intron of the NOP56 gene. The aim of this study is to clarify the prevalence, clinical and genetic features of SCA36.
The expansion was tested in 676 unrelated SCA index cases and 727 controls from France, Germany and Japan. Clinical and neuropathological features were investigated in available family members.
Normal alleles ranged between 5 and 14 hexanucleotide repeats. Expansions were detected in 12 families in France (prevalence: 1.9% of all French SCAs) including one family each with Spanish, Portuguese or Chinese ancestry, in five families in Japan (1.5% of all Japanese SCAs), but were absent in German patients. All the 17 SCA36 families shared one common haplotype for a 7.5 kb pairs region flanking the expansion. While 27 individuals had typically long expansions, three affected individuals harboured small hexanucleotide expansions of 25, 30 and 31 hexanucleotide repeat-units, demonstrating that such a small expansion could cause the disease. All patients showed slowly progressive cerebellar ataxia frequently accompanied by hearing and cognitive impairments, tremor, ptosis and reduced vibration sense, with the age at onset ranging between 39 and 65 years, and clinical features were indistinguishable between individuals with short and typically long expansions. Neuropathology in a presymptomatic case disclosed that Purkinje cells and hypoglossal neurons are affected.
SCA36 is rare with a worldwide distribution. It can be caused by a short GGCCTG expansion and associates various extracerebellar symptoms.
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[Show abstract][Hide abstract] ABSTRACT: Diabetes mellitus and neurodegeneration are common diseases for which shared genetic factors are still only partly known. Here, we show that loss of the BiP (immunoglobulin heavy-chain binding protein) co-chaperone DNAJC3 leads to diabetes mellitus and wide-spread neurodegeneration. We investigated three siblings with juvenile-onset diabetes and central and peripheral neurodegeneration, including ataxia, upper-motor-neuron damage, peripheral neuropathy, hearing loss, and cerebral atrophy. Exome sequencing identified a homozygous stop mutation in DNAJC3. Screening of a diabetes database with 226,194 individuals yielded eight phenotypically similar individuals and one family carrying a homozygous DNAJC3 deletion. DNAJC3 was absent in fibroblasts from all affected subjects in both families. To delineate the phenotypic and mutational spectrum and the genetic variability of DNAJC3, we analyzed 8,603 exomes, including 506 from families affected by diabetes, ataxia, upper-motor-neuron damage, peripheral neuropathy, or hearing loss. This anal-ysis revealed only one further loss-of-function allele in DNAJC3 and no further associations in subjects with only a subset of the features of the main phenotype. Our findings demonstrate that loss-of-function DNAJC3 mutations lead to a monogenic, recessive form of diabetes mellitus in humans. Moreover, they present a common denominator for diabetes and widespread neurodegeneration. This complements findings from mice in which knockout of Dnajc3 leads to diabetes and modifies disease in a neurodegenerative model of Marinesco-Sjögren syndrome. Nonautoimmune diabetes mellitus and neurodegenera-tion are common disorders for which shared genetic factors are still only partly known. Monogenic forms of diabetes include neonatal diabetes (MIM 606176) and maturity-onset diabetes of the young (MIM 606391), both of which arise from mutations that primarily reduce pancreatic b cell function. 1 Although monogenic
The American Journal of Human Genetics 11/2014; 95(6). DOI:10.1016/j.ajhg.2014.10.013 · 10.93 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: To retrospectively determine the frequency of N-Methyl-D-Aspartate (NMDA) receptor (NMDAR) autoantibodies in patients with different forms of dementia.
Clinical characterization of 660 patients with dementia, neurodegenerative disease without dementia, other neurological disorders and age-matched healthy controls combined with retrospective analysis of serum or cerebrospinal fluid (CSF) for the presence of NMDAR antibodies. Antibody binding to receptor mutants and the effect of immunotherapy were determined in a subgroup of patients.
Serum NMDAR antibodies of IgM, IgA, or IgG subtypes were detected in 16.1% of 286 dementia patients (9.5% IgM, 4.9% IgA, and 1.7% IgG) and in 2.8% of 217 cognitively healthy controls (1.9% IgM and 0.9% IgA). Antibodies were rarely found in CSF. The highest prevalence of serum antibodies was detected in patients with "unclassified dementia" followed by progressive supranuclear palsy, corticobasal syndrome, Parkinson's disease-related dementia, and primary progressive aphasia. Among the unclassified dementia group, 60% of 20 patients had NMDAR antibodies, accompanied by higher frequency of CSF abnormalities, and subacute or fluctuating disease progression. Immunotherapy in selected prospective cases resulted in clinical stabilization, loss of antibodies, and improvement of functional imaging parameters. Epitope mapping showed varied determinants in patients with NMDAR IgA-associated cognitive decline.
Serum IgA/IgM NMDAR antibodies occur in a significant number of patients with dementia. Whether these antibodies result from or contribute to the neurodegenerative disorder remains unknown, but our findings reveal a subgroup of patients with high antibody levels who can potentially benefit from immunotherapy.