Pure Cerebellar Ataxia with Homozygous Mutations in the PNPLA6 Gene.

Autosomal-recessive cerebellar ataxias (ARCA) are clinically and genetically heterogeneous conditions primarily affecting the cerebellum. Mutations in the PNPLA6 gene have been identified as the cause of hereditary spastic paraplegia and complex forms of ataxia associated with retinal and endocrine manifestations in a field where the genotype-phenotype correlations are rapidly expanding. We identified two cousins from a consanguineous family belonging to a large Zoroastrian (Parsi) family residing in Mumbai, India, who presented with pure cerebellar ataxia without chorioretinal dystrophy or hypogonadotropic hypogonadism. We used a combined approach of clinical characterisation, homozygosity mapping, whole-exome and Sanger sequencing to identify the genetic defect in this family. The phenotype in the family was pure cerebellar ataxia. Homozygosity mapping revealed one large region of shared homozygosity at chromosome 19p13 between affected individuals. Within this region, whole-exome sequencing of the index case identified two novel homozygous missense variants in the PNPLA6 gene at c.3847G>A (p.V1283M) and c.3929A>T (p.D1310V) in exon 32. Both segregated perfectly with the disease in this large family, with only the two affected cousins being homozygous. We identified for the first time PNPLA6 mutations associated with pure cerebellar ataxia in a large autosomal-recessive Parsi kindred. Previous mutations in this gene have been associated with a more complex phenotype but the results here suggest an extension of the associated disease spectrum.

DYT6 Dystonia: A Neuropathological Study.

BACKGROUND: Mutations in the thanatos-associated protein domain containing apoptosis-associated protein 1 gene (THAP1) are responsible for adult-onset isolated dystonia (DYT6). However, no neuropathological studies of genetically proven DYT6 cases have been previously reported. OBJECTIVE: We report the first detailed neuropathological investigation carried out on two DYT6 brains. METHODS: Genetic screening for THAP1 gene mutations using standard Sanger polymerase chain reaction sequencing identified 2 cases, 1 with a known pathogenic mutation and the other with a novel mutation. A detailed neuropathological assessment of the cases was performed. RESULTS: Both DYT6 cases showed no significant neurodegeneration and no specific disease-related pathology. CONCLUSIONS: No neuropathological features that could be defined as hallmark features of DYT6 dystonia were identified. Our study supports the notion that in isolated dystonia, there is no significant neurodegeneration or morphological lesions that can be identified using routine methods.

Mutations in the autoregulatory domain of ß-tubulin 4a cause hereditary dystonia.

Dystonia type 4 (DYT4) was first described in a large family from Heacham in Norfolk with an autosomal dominantly inherited whispering dysphonia, generalized dystonia, and a characteristic hobby horse ataxic gait. We carried out a genetic linkage analysis in the extended DYT4 family that spanned 7 generations from England and Australia, revealing a single LOD score peak of 6.33 on chromosome 19p13.12-13. Exome sequencing in 2 cousins identified a single cosegregating mutation (p.R2G) in the ß-tubulin 4a (TUBB4a) gene that was absent in a large number of controls. The mutation is highly conserved in the ß-tubulin autoregulatory MREI (methionine-arginine-glutamic acid-isoleucine) domain, highly expressed in the central nervous system, and extensive in vitro work has previously demonstrated that substitutions at residue 2, specifically R2G, disrupt the autoregulatory capability of the wild-type ß-tubulin peptide, affirming the role of the cytoskeleton in dystonia pathogenesis.

Tumor and local lymphoid tissue interaction determines prognosis in high-grade serous ovarian cancer.

Tertiary lymphoid structure (TLS) is associated with prognosis in copy-number-driven tumors, including high-grade serous ovarian cancer (HGSOC), although the function of TLS and its interaction with copy-number alterations in HGSOC are not fully understood. In the current study, we confirm that TLS-high HGSOC patients show significantly better progression-free survival (PFS). We show that the presence of TLS in HGSOC tumors is associated with B cell maturation and cytotoxic tumor-specific T cell activation and proliferation. In addition, the copy-number loss of IL15 and CXCL10 may limit TLS formation in HGSOC; a list of genes that may dysregulate TLS function is also proposed. Last, a radiomics-based signature is developed to predict the presence of TLS, which independently predicts PFS in both HGSOC patients and immune checkpoint inhibitor (ICI)-treated non-small cell lung cancer (NSCLC) patients. Overall, we reveal that TLS coordinates intratumoral B cell and T cell response to HGSOC tumor, while the cancer genome evolves to counteract TLS formation and function.

THAP1 mutations and dystonia phenotypes: genotype phenotype correlations.

THAP1 mutations have been shown to be the cause of DYT6. A number of different mutation types and locations in the THAP1 gene have been associated with a range of severity and dystonia phenotypes, but, as yet, it has been difficult to identify clear genotype phenotype patterns. Here, we screened the THAP1 gene in a further series of dystonia cases and evaluated the mutation pathogenicity in this series as well as previously reported mutations to investigate possible phenotype-genotype correlations. THAP1 mutations have been identified throughout the coding region of the gene, with the greatest concentration of variants localized to the THAP1 domain. In the additional cases analyzed here, a further two mutations were found. No obvious, indisputable genotype-phenotype correlation emerged from these data. However, we managed to find a correlation between the pathogenicity of mutations, distribution, and age of onset of dystonia. THAP1 mutations are an important cause of dystonia, but, as yet, no clear genotype-phenotype correlations have been identified. Greater mutation numbers in different populations will be important and mutation-specific functional studies will be essential to identify the pathogenicity of the various THAP1 mutations. © 2012 Movement Disorder Society.

SNCA variants are associated with increased risk for multiple system atrophy.

To test whether the synucleinopathies Parkinson's disease and multiple system atrophy (MSA) share a common genetic etiology, we performed a candidate single nucleotide polymorphism (SNP) association study of the 384 most associated SNPs in a genome-wide association study of Parkinson's disease in 413 MSA cases and 3,974 control subjects. The 10 most significant SNPs were then replicated in additional 108 MSA cases and 537 controls. SNPs at the SNCA locus were significantly associated with risk for increased risk for the development of MSA (combined p = 5.5 x 10(-12); odds ratio 6.2) [corrected].

Indian-subcontinent NBIA: unusual phenotypes, novel PANK2 mutations, and undetermined genetic forms.

Neurodegeneration with brain iron accumulation (NBIA) is etiologically, clinically, and by imaging a heterogeneous group including NBIA types 1 [pantothenate kinase-associated neurodegeneration (PKAN)] and 2 (PLA2G6-associated neurodegeneration), neuroferritinopathy, and aceruloplasminaemia. Data on genetically defined Indian-subcontinent NBIA cases are limited. We report 6 patients from the Indian-subcontinent with a movement disorder and MRI basal ganglia iron deposition, compatible with diagnosis of an NBIA syndrome. All patients were screened for abnormalities in serum ceruloplasmin and ferritin levels and mutations in NBIA-associated genes [pantothenate kinase 2 (PANK2), PLA2G6 and ferritin light chain (exon 4)]. We present clinical, imaging and genetic data correlating phenotype-genotype relations. Four patients carried PANK2 mutations, two of these were novel. The clinical phenotype was mainly dystonic with generalized dystonia and marked orobulbar features in the 4 adolescent-onset cases. One of the four had a late-onset (age 37) unilateral jerky postural tremor. His mutation, c.1379C>T, appears associated with a milder phenotype. Interestingly, he developed the eye-of-the-tiger sign only 10 years after onset. Two of the six presented with adult-onset levodopa (L-dopa)-responsive asymmetric re-emergent rest tremor, developing L-dopa-induced dyskinesias, and good benefit to deep brain stimulation (in one), thus resembling Parkinson's disease (PD). Both had an eye-of-the-tiger sign on MRI but were negative for known NBIA-associated genes, suggesting the existence of further genetic or sporadic forms of NBIA syndromes. In conclusion, genetically determined NBIA cases from the Indian subcontinent suggest presence of unusual phenotypes of PANK2 and novel mutations. The phenotype of NBIA of unknown cause includes a PD-like presentation.

Glucocerebrosidase mutations in clinical and pathologically proven Parkinson's disease.

Mutations in the glucocerebrosidase gene (GBA) are associated with Gaucher's disease, the most common lysosomal storage disorder. Parkinsonism is an established feature of Gaucher's disease and an increased frequency of mutations in GBA has been reported in several different ethnic series with sporadic Parkinson's disease. In this study, we evaluated the frequency of GBA mutations in British patients affected by Parkinson's disease. We utilized the DNA of 790 patients and 257 controls, matched for age and ethnicity, to screen for mutations within the GBA gene. Clinical data on all identified GBA mutation carriers was reviewed and analysed. Additionally, in all cases where brain material was available, a neuropathological evaluation was performed and compared to sporadic Parkinson's disease without GBA mutations. The frequency of GBA mutations among the British patients (33/790 = 4.18%) was significantly higher (P = 0.01; odds ratio = 3.7; 95% confidence interval = 1.12-12.14) when compared to the control group (3/257 = 1.17%). Fourteen different GBA mutations were identified, including three previously undescribed mutations, K7E, D443N and G193E. Pathological examination revealed widespread and abundant alpha-synuclein pathology in all 17 GBA mutation carriers, which were graded as Braak stage of 5-6, and had McKeith's limbic or diffuse neocortical Lewy body-type pathology. Diffuse neocortical Lewy body-type pathology tended to occur more frequently in the group with GBA mutations compared to matched Parkinson's disease controls. Clinical features comprised an early onset of the disease, the presence of hallucinations in 45% (14/31) and symptoms of cognitive decline or dementia in 48% (15/31) of patients. This study demonstrates that GBA mutations are found in British subjects at a higher frequency than any other known Parkinson's disease gene. This is the largest study to date on a non-Jewish patient sample with a detailed genotype/phenotype/pathological analyses which strengthens the hypothesis that GBA mutations represent a significant risk factor for the development of Parkinson's disease and suggest that to date, this is the most common genetic factor identified for the disease.

Forebrain deletion of the dystonia protein torsinA causes dystonic-like movements and loss of striatal cholinergic neurons.

Striatal dysfunction plays an important role in dystonia, but the striatal cell types that contribute to abnormal movements are poorly defined. We demonstrate that conditional deletion of the DYT1 dystonia protein torsinA in embryonic progenitors of forebrain cholinergic and GABAergic neurons causes dystonic-like twisting movements that emerge during juvenile CNS maturation. The onset of these movements coincides with selective degeneration of dorsal striatal large cholinergic interneurons (LCI), and surviving LCI exhibit morphological, electrophysiological, and connectivity abnormalities. Consistent with the importance of this LCI pathology, murine dystonic-like movements are reduced significantly with an antimuscarinic agent used clinically, and we identify cholinergic abnormalities in postmortem striatal tissue from DYT1 dystonia patients. These findings demonstrate that dorsal LCI have a unique requirement for torsinA function during striatal maturation, and link abnormalities of these cells to dystonic-like movements in an overtly symptomatic animal model.

Neuropathological features of genetically confirmed DYT1 dystonia: investigating disease-specific inclusions.

INTRODUCTION: Early onset isolated dystonia (DYT1) is linked to a three base pair deletion (ΔGAG) mutation in the TOR1A gene. Clinical manifestation includes intermittent muscle contraction leading to twisting movements or abnormal postures. Neuropathological studies on DYT1 cases are limited, most showing no significant abnormalities. In one study, brainstem intraneuronal inclusions immunoreactive for ubiquitin, torsinA and lamin A/C were described. Using the largest series reported to date comprising 7 DYT1 cases, we aimed to identify consistent neuropathological features in the disease and determine whether we would find the same intraneuronal inclusions as previously reported. RESULT: The pathological changes of brainstem inclusions reported in DYT1 dystonia were not replicated in our case series. Other anatomical regions implicated in dystonia showed no disease-specific pathological intracellular inclusions or evidence of more than mild neuronal loss. CONCLUSION: Our findings suggest that the intracellular inclusions described previously in DYT1 dystonia may not be a hallmark feature of the disorder. In isolated dystonia, DYT1 in particular, biochemical changes may be more relevant than the morphological changes.

C19orf12 mutation leads to a pallido-pyramidal syndrome.

Pallido-pyramidal syndromes combine dystonia with or without parkinsonism and spasticity as part of a mixed neurodegenerative disorder. Several causative genes have been shown to lead to pallido-pyramidal syndromes, including FBXO7, ATP13A2, PLA2G6, PRKN and SPG11. Among these, ATP13A2 and PLA2G6 are inconsistently associated with brain iron deposition. Using homozygosity mapping and direct sequencing in a multiplex consanguineous Saudi Arabian family with a pallido-pyramidal syndrome, iron deposition and cerebellar atrophy, we identified a homozygous p.G53R mutation in C19orf12. Our findings add to the phenotypic spectrum associated with C19orf12 mutations.

Analysis of spinocerebellar ataxias due to expanded triplet repeats in Greek patients with cerebellar ataxia.

The relative frequency of different autosomal dominant cerebellar ataxias, commonly referred to as spinocerebellar ataxias (SCAs), varies considerably among populations of different ethnic origin. No data exist at present on the frequency of different SCAs in the Greek population. In the present study we investigated the presence of triplet repeat expansion SCAs (SCA1, SCA2, SCA3, SCA6, SCA7, SCA8, SCA12, SCA17 and DRPLA) in a cohort of 83 Greek patients with slowly progressive cerebellar ataxia. Twenty patients came from autosomal dominant (AD) pedigrees, seven displayed recessive or unclear inheritance and 56 were sporadic. We found four patients with pathological SCA expansions, all from AD pedigrees. Two patients had SCA1, one SCA2 and one SCA7 (10.0, 5.0 and 5.0% of the AD group, respectively). The clinical features of these patients were within the expected spectrum. In total, a pathological expansion was detected in 20% of patients from AD pedigrees. Interestingly, no cases of SCA3 or SCA6 were detected in the AD group. No expansions were found in other familial cases or in sporadic patients. Overall, no cases of SCA3, SCA6, SCA12, SCA17 or DRPLA were identified in the Greek population. In conclusion, SCA1, SCA2 and SCA7 are present in Greek patients with AD cerebellar ataxia in frequencies similar to those observed in other populations. SCA3 and SCA6 appear however to be rare in Greece. The genetic cause for the majority of AD ataxias remains to be identified.

Analysis of ATP13A2 in large neurodegeneration with brain iron accumulation (NBIA) and dystonia-parkinsonism cohorts.

Several causative genes have been identified for both dystonia-parkinsonism and neurodegeneration with brain iron accumulation (NBIA), yet many patients do not have mutations in any of the known genes. Mutations in the ATP13A2 lead to Kufor Rakeb disease, a form of autosomal recessive juvenile parkinsonism that also features oromandibular dystonia. More recently, evidence of iron deposition in the caudate and putamen have been reported in patients with ATP13A2 mutations. We set out to determine the frequency of ATP13A2 mutations in cohorts of idiopathic NBIA and dystonia-parkinsonism. We screened for large deletions using whole genome arrays, and sequenced the entire coding region in 92 cases of NBIA and 76 cases of dystonia-parkinsonism. A number of coding and non-coding sequence variants were identified in a heterozygous state, but none were predicted to be pathogenic based on in silico analyses. Our results indicate that ATP13A2 mutations are a rare cause of both NBIA and dystonia-parkinsonism.

Mutational analysis of parkin and PINK1 in multiple system atrophy.

Multiple system atrophy (MSA) and Parkinson's disease (PD) are progressive neurodegenerative disorders with overlapping clinical, biochemical and genetic features. To test the hypothesis that the PD genes parkin and PINK1 also play a role in the pathogenesis of MSA, we performed a mutational screening study involving 87 pathologically proven MSA cases. In parkin we identified eight sequence variants and four heterozygous deletions and in PINK1 we identified nine variants of which two silent mutations have not been previously reported (p.Gly189Gly and p.Arg337Arg). The frequencies of the observed variants were not significantly different from previously published control data and none of the possibly pathogenic variants were found in a homozygous state. Our results indicate that genetic variants at the parkin and PINK1 loci do not play a critical role in the pathogenesis of MSA.

Mutations in TRPV4 cause Charcot-Marie-Tooth disease type 2C.

Charcot-Marie-Tooth disease type 2C (CMT2C) is an autosomal dominant neuropathy characterized by limb, diaphragm and laryngeal muscle weakness. Two unrelated families with CMT2C showed significant linkage to chromosome 12q24.11. We sequenced all genes in this region and identified two heterozygous missense mutations in the TRPV4 gene, C805T and G806A, resulting in the amino acid substitutions R269C and R269H. TRPV4 is a well-known member of the TRP superfamily of cation channels. In TRPV4-transfected cells, the CMT2C mutations caused marked cellular toxicity and increased constitutive and activated channel currents. Mutations in TRPV4 were previously associated with skeletal dysplasias. Our findings indicate that TRPV4 mutations can also cause a degenerative disorder of the peripheral nerves. The CMT2C-associated mutations lie in a distinct region of the TRPV4 ankyrin repeats, suggesting that this phenotypic variability may be due to differential effects on regulatory protein-protein interactions.