Magnetic resonance radiomics-derived sphericity correlates with seizure in brain arteriovenous malformations.

OBJECTIVES: Angioarchitectural analysis of brain arteriovenous malformations (BAVMs) is qualitative and subject to interpretation. This study quantified the morphology of and signal changes in the nidal and perinidal areas by using MR radiomics and compared the performance of MR radiomics and angioarchitectural analysis in detecting epileptic BAVMs. MATERIALS AND METHODS: From 2010 to 2020, a total of 111 patients with supratentorial BAVMs were retrospectively included and grouped in accordance with the initial presentation of seizure. Patients' angiograms and MR imaging results were analyzed to determine the corresponding angioarchitecture. The BAVM nidus was contoured on time-of-flight MR angiography images. The perinidal brain parenchyma was contoured on T2-weighted images, followed by radiomic analysis. Logistic regression analysis was performed to determine the independent risk factors for seizure. ROC curve analysis, decision curve analysis (DCA), and calibration curve were performed to compare the performance of angioarchitecture-based and radiomics-based models in diagnosing epileptic BAVMs. RESULTS: In multivariate analyses, low sphericity (OR: 2012.07, p = .04) and angiogenesis (OR: 5.30, p = .01) were independently associated with a high risk of seizure after adjustment for age, sex, temporal location, and nidal volume. The AUC for the angioarchitecture-based, MR radiomics-based, and combined models was 0.672, 0.817, and 0.794, respectively. DCA confirmed the clinical utility of the MR radiomics-based and combined models. CONCLUSIONS: Low nidal sphericity and angiogenesis were associated with high seizure risk in patients with BAVMs. MR radiomics-derived tools may be used for noninvasive and objective measurement for evaluating the risk of seizure due to BAVM. CLINICAL RELEVANCE STATEMENT: Low nidal sphericity was associated with high seizure risk in patients with brain arteriovenous malformation and MR radiomics may be used as a noninvasive and objective measurement method for evaluating seizure risk in patients with brain arteriovenous malformation. KEY POINTS: • Low nidal sphericity was associated with high seizure risk in patients with brain arteriovenous malformation. • The performance of MR radiomics in detecting epileptic brain arteriovenous malformations was more satisfactory than that of angioarchitectural analysis. • MR radiomics may be used as a noninvasive and objective measurement method for evaluating seizure risk in patients with brain arteriovenous malformation.

Monogenic Causes in Familial Stroke Across Intracerebral Hemorrhage and Ischemic Stroke Subtypes Identified by Whole-Exome Sequencing.

Whole exome sequencing (WES) has been used to detect rare causative variants in neurological diseases. However, the efficacy of WES in genetic diagnosis of clinically heterogeneous familial stroke remains inconclusive. We prospectively searched for disease-causing variants in unrelated probands with defined familial stroke by candidate gene/hotspot screening and/or WES, depending on stroke subtypes and neuroimaging features at a referral center. The clinical significance of each variant was determined according to the American College of Medical Genetics guidelines. Among 161 probands (mean age at onset 53.2 ± 13.7 years; male 63.4%), 33 participants (20.5%) had been identified with 19 pathogenic/likely pathogenic variants (PVs; WES applied 152/161 = 94.4%). Across subtypes, the highest hit rate (HR) was intracerebral hemorrhage (ICH, 7/18 = 38.9%), particularly with the etiological subtype of structural vasculopathy (4/4 = 100%, PVs in ENG, KRIT1, PKD1, RNF213); followed by ischemic small vessel disease (SVD, 15/48 = 31.3%; PVs in NOTCH3, HTRA1, HBB). In contrast, large artery atherosclerosis (LAA, 4/44 = 9.1%) and cardioembolism (0/11 = 0%) had the lowest HR. NOTCH3 was the most common causative gene (16/161 = 9.9%), presenting with multiple subtypes of SVD (n = 13), ICH (n = 2), or LAA (n = 1). Importantly, we disclosed two previously unreported PVs, KRIT1 p.E379* in a familial cerebral cavernous malformation, and F2 p.F382L in a familial cerebral venous sinus thrombosis. The contribution of monogenic etiologies was particularly high in familial ICH and SVD subtypes in our Taiwanese cohort. Utilizing subtype-guided hotspot screening and/or subsequent WES, we unraveled monogenic causes in 20.5% familial stroke probands, including 1.2% novel PVs. Genetic diagnosis may enable early diagnosis, management and lifestyle modification. Among 161 familial stroke probands, 33 (20.5%) had been identified pathogenic or likely pathogenic monogenic variants related to stroke. The positive hit rate among all subtypes was high in intracerebral hemorrhage (ICH) and ischemic small vessel disease (SVD). Notably, two previously unreported variants, KRIT1 p.E379* in a familial cerebral cavernous malformation and F2 p.F382L in familial cerebral venous sinus thrombosis, were disclosed. CVT cerebral venous thrombosis; HTN Hypertensive subtype; LAA large artery atherosclerosis; SV structural vasculopathy; U Undetermined.

Novel lissencephaly-associated DCX variants in the C-terminal DCX domain affect microtubule binding and dynamics.

OBJECTIVE: Pathogenic variants in DCX on the X chromosome lead to lissencephaly and subcortical band heterotopia (SBH), brain malformations caused by neuronal migration defects. Its product doublecortin (DCX) binds to microtubules to modulate microtubule polymerization. How pathogenic DCX variants affect these activities remains not fully investigated. METHODS: DCX variants were identified using whole exome and Sanger sequencing from six families with lissencephaly/SBH. We examined how these variants affect DCX functions using microtubule binding, regrowth, and colocalization assays. RESULTS: We found novel DCX variants p.Val177AlafsTer31 and p.Gly188Trp, as well as reported variants p.Arg196His, p.Lys202Met, and p.Thr203Ala. Incidentally, all of the missense variants were clustered on the C-terminal DCX domain. The microtubule binding ability was significantly decreased in p.Val177AlafsTer31, p.Gly188Trp, p.Lys202Met, and previously reported p.Asp262Gly variants. Furthermore, expression of p.Val177AlafsTer31, p.Gly188Trp, p.Arg196His, p.Lys202Met, and p.Asp262Gly variants hindered microtubule growth in cells. There were also decreases in the colocalization of p.Val177AlafsTer31, p.Thr203Ala, and p.Asp262Gly variants to microtubules. SIGNIFICANCE: Our results indicate that these variants in the C-terminal DCX domain altered microtubule binding and dynamics, which may underlie neuronal migration defects during brain development.

Clinical characteristics and long-term outcome of cerebral cavernous malformations-related epilepsy.

OBJECTIVE: Cerebral cavernous malformations (CCMs) present variably, and epileptic seizures are the most common symptom. The factors contributing to cavernoma-related epilepsy (CRE) and drug resistance remain inconclusive. The outcomes of CRE after different treatment modalities have not yet been fully addressed. This study aimed to characterize the clinical features of patients with CRE and the long-term seizure outcomes of medical and surgical treatment strategies. METHODS: This was a retrospective cohort of 135 patients with CCM who were diagnosed in 2007-2011 and followed up for 93.6 months on average. The patients were divided into drug-resistant epilepsy (DRE; n = 29), non-DRE (n = 45), and no epilepsy (NE; n = 61). RESULTS: Temporal CCM was the factor most strongly associated with the development of both CRE and DRE. The majority of patients with single temporal CCMs had CRE (86.8%, n = 33), and 50% had DRE, whereas only 14.7% (n = 5) with a nontemporal supratentorial CCM had DRE (p < .05). The most common lesion site in the DRE group was the mesiotemporal lobe (50%). Multiple CCMs were more frequently observed in the CRE (29.2%) than the NE (11.5%) group (p < .05). In patients with CRE, multiple lesions were associated with a higher rebleeding rate (odds ratio = 11.1), particularly in those with DRE (odds ratio = 15.4). The majority of patients who underwent resective surgery for DRE (76.5%, n = 13) achieved International League Against Epilepsy Class I and II seizure outcomes even after a long disease course. SIGNIFICANCE: Temporal CCM not only predisposes to CRE but also is a major risk factor for drug resistance. The mesiotemporal lobe is the most epileptogenic zone. Multiple CCMs are another risk factor for CRE and increase the rebleeding risk in these patients. Surgical resection could provide beneficial long-term seizure outcomes in patients with DRE.

Acute withdrawal of new-generation antiepileptic drugs in epilepsy monitoring units: Safety and efficacy.

INTRODUCTION: Acute withdrawal of antiepileptic drugs (AEDs) is a safe and effective approach to provoking seizures in order to complete video-electroencephalogram (V-EEG) studies in a timely manner. Previous studies have focused only on withdrawal from conventional AEDs, and the effects of withdrawal from new-generation AEDs have not been extensively studied. MATERIALS AND METHODS: This study examined adult patients with drug-resistant epilepsy admitted to an epilepsy monitoring unit between 2015 and 2018. Patients were classified according to whether they received conventional AEDs (Con; n = 13) or new-generation AEDs (N-Gen; n = 26). We then compared the effects of withdrawing these two types of AEDs over a period of one week in terms of efficacy (time to complete V-EEG monitoring) and safety, including the incidence of cluster seizures (CS), focal to bilateral tonic-clonic seizures (FBTCS) and status epilepticus (SE). RESULTS: In both groups, approximately one week was required to complete V-EEG analysis: N-Gen group (5.6 days) and Con group (6.3 days). No differences were observed between the two groups in terms of the median number of seizures, the onset of the 1st seizure, the distribution of CS, FBTCS, or SE. Following acute withdrawal of medication, a high percentage of patients with a history of CS or FBTCS, respectively, presented CS or FBTCS. CONCLUSIONS: We did not observe significant differences between patients taking new-generation AEDs and those taking conventional AEDs following withdrawal during V-EEG recording. In the current study, we employed a standard protocol for the rapid withdrawal of AEDs (daily dose reduction of 50%), which was sufficient for 80% of patients to complete V-EEG monitoring within one week.

Cellular secretion and cytotoxicity of transthyretin mutant proteins underlie late-onset amyloidosis and neurodegeneration.

Transthyretin amyloidosis (ATTR) is a progressive life-threatening disease characterized by the deposition of transthyretin (TTR) amyloid fibrils. Several pathogenic variants have been shown to destabilize TTR tetramers, leading to aggregation of misfolded TTR fibrils. However, factors that underlie the differential age of disease onset amongst amyloidogenic TTR variants remain elusive. Here, we examined the biological properties of various TTR mutations and found that the cellular secretory pattern of the wild-type (WT) TTR was similar to those of the late-onset mutant (Ala97Ser, p. Ala117Ser), stable mutant (Thr119Met, p. Thr139Met), early-onset mutant (Val30Met, p. Val50Met), but not in the unstable mutant (Asp18Gly, p. Asp38Gly). Cytotoxicity assays revealed their toxicities in the order of Val30Met > Ala97Ser > WT > Thr119Met in neuroblastoma cells. Surprisingly, while early-onset amyloidogenic TTR monomers (M-TTRs) are retained by the endoplasmic reticulum quality control (ERQC), late-onset amyloidogenic M-TTRs can be secreted extracellularly. Treatment of thapsigargin (Tg) to activate the unfolded protein response (UPR) alleviates Ala97Ser M-TTR secretion. Interestingly, Ala97Ser TTR overexpression in Drosophila causes late-onset fast neurodegeneration and a relatively short lifespan, recapitulating human disease progression. Our study demonstrates that the escape of TTR monomers from the ERQC may underlie late-onset amyloidogenesis in patients and suggests that targeting ERQC could mitigate late-onset ATTR.

PDXK mutations cause polyneuropathy responsive to pyridoxal 5'-phosphate supplementation.

OBJECTIVE: To identify disease-causing variants in autosomal recessive axonal polyneuropathy with optic atrophy and provide targeted replacement therapy. METHODS: We performed genome-wide sequencing, homozygosity mapping, and segregation analysis for novel disease-causing gene discovery. We used circular dichroism to show secondary structure changes and isothermal titration calorimetry to investigate the impact of variants on adenosine triphosphate (ATP) binding. Pathogenicity was further supported by enzymatic assays and mass spectroscopy on recombinant protein, patient-derived fibroblasts, plasma, and erythrocytes. Response to supplementation was measured with clinical validated rating scales, electrophysiology, and biochemical quantification. RESULTS: We identified biallelic mutations in PDXK in 5 individuals from 2 unrelated families with primary axonal polyneuropathy and optic atrophy. The natural history of this disorder suggests that untreated, affected individuals become wheelchair-bound and blind. We identified conformational rearrangement in the mutant enzyme around the ATP-binding pocket. Low PDXK ATP binding resulted in decreased erythrocyte PDXK activity and low pyridoxal 5'-phosphate (PLP) concentrations. We rescued the clinical and biochemical profile with PLP supplementation in 1 family, improvement in power, pain, and fatigue contributing to patients regaining their ability to walk independently during the first year of PLP normalization. INTERPRETATION: We show that mutations in PDXK cause autosomal recessive axonal peripheral polyneuropathy leading to disease via reduced PDXK enzymatic activity and low PLP. We show that the biochemical profile can be rescued with PLP supplementation associated with clinical improvement. As B6 is a cofactor in diverse essential biological pathways, our findings may have direct implications for neuropathies of unknown etiology characterized by reduced PLP levels. ANN NEUROL 2019;86:225-240.

Novel SCA19/22-associated KCND3 mutations disrupt human KV 4.3 protein biosynthesis and channel gating.

Mutations in the human voltage-gated K+ channel subunit KV 4.3-encoding KCND3 gene have been associated with the autosomal dominant neurodegenerative disorder spinocerebellar ataxia types 19 and 22 (SCA19/22). The precise pathophysiology underlying the dominant inheritance pattern of SCA19/22 remains elusive. Using cerebellar ataxia-specific targeted next-generation sequencing technology, we identified two novel KCND3 mutations, c.950 G>A (p.C317Y) and c.1123 C>T (p.P375S) from a cohort with inherited cerebellar ataxias in Taiwan. The patients manifested notable phenotypic heterogeneity that includes cognitive impairment. We employed in vitro heterologous expression systems to inspect the biophysical and biochemical properties of human KV 4.3 harboring the two novel mutations, as well as two previously reported but uncharacterized disease-related mutations, c.1013 T>A (p.V338E) and c.1130 C>T (p.T377M). Electrophysiological analyses revealed that all of these SCA19/22-associated KV 4.3 mutant channels manifested loss-of-function phenotypes. Protein chemistry and immunofluorescence analyses further demonstrated that these mutants displayed enhanced protein degradation and defective membrane trafficking. By coexpressing KV 4.3 wild-type with the disease-related mutants, we provided direct evidence showing that the mutants instigated anomalous protein biosynthesis and channel gating of KV 4.3. We propose that the dominant inheritance pattern of SCA19/22 may be explained by the dominant-negative effects of the mutants on protein biosynthesis and voltage-dependent gating of KV 4.3 wild-type channel.

PRRT2 missense mutations cluster near C-terminus and frequently lead to protein mislocalization.

OBJECTIVE: Variants in human PRRT2 cause paroxysmal kinesigenic dyskinesia (PKD) and other neurological disorders. Most reported variants resulting in truncating proteins failed to localize to cytoplasmic membrane. The present study identifies novel PRRT2 variants in PKD and epilepsy patients and evaluates the functional consequences of PRRT2 missense variations. METHODS: We investigated two families with PKD and epilepsies using Sanger sequencing and a multiple gene panel. Subcellular localization of mutant proteins was investigated using confocal microscopy and cell surface biotinylation assay in Prrt2-transfected cells. RESULTS: Two novel PRRT2 variants, p.His232Glnfs*10 and p.Leu298Pro, were identified, and functional study revealed impaired localization of both mutant proteins to the plasma membrane. Further investigation of other reported missense variants revealed decreased protein targeting to the plasma membrane in eight of the 13 missense variants examined (p.Trp281Arg, p.Ala287Thr, p.Ala291Val, p.Arg295Gln, p.Leu298Pro, p.Ala306Asp, p.Gly324Glu, and p.Gly324Arg). In contrast, all benign variants we tested exhibited predominant localization to the plasma membrane similar to wild-type Prrt2. Most likely pathogenic variants were located at conserved amino acid residues near the C-terminus, whereas truncating variants spread throughout the gene. SIGNIFICANCE: PRRT2 missense variants clustering at the C-terminus often lead to protein mislocalization. Failure in protein targeting to the plasma membrane by PRRT2 variants may be a key mechanism in causing PKD and related neurological disorders.

A recurrent WARS mutation is a novel cause of autosomal dominant distal hereditary motor neuropathy.

Distal hereditary motor neuropathy is a heterogeneous group of inherited neuropathies characterized by distal limb muscle weakness and atrophy. Although at least 15 genes have been implicated in distal hereditary motor neuropathy, the genetic causes remain elusive in many families. To identify an additional causal gene for distal hereditary motor neuropathy, we performed exome sequencing for two affected individuals and two unaffected members in a Taiwanese family with an autosomal dominant distal hereditary motor neuropathy in which mutations in common distal hereditary motor neuropathy-implicated genes had been excluded. The exome sequencing revealed a heterozygous mutation, c.770A > G (p.His257Arg), in the cytoplasmic tryptophanyl-tRNA synthetase (TrpRS) gene (WARS) that co-segregates with the neuropathy in the family. Further analyses of WARS in an additional 79 Taiwanese pedigrees with inherited neuropathies and 163 index cases from Australian, European, and Korean distal hereditary motor neuropathy families identified the same mutation in another Taiwanese distal hereditary motor neuropathy pedigree with different ancestries and one additional Belgian distal hereditary motor neuropathy family of Caucasian origin. Cell transfection studies demonstrated a dominant-negative effect of the p.His257Arg mutation on aminoacylation activity of TrpRS, which subsequently compromised protein synthesis and reduced cell viability. His257Arg TrpRS also inhibited neurite outgrowth and led to neurite degeneration in the neuronal cell lines and rat motor neurons. Further in vitro analyses showed that the WARS mutation could potentiate the angiostatic activities of TrpRS by enhancing its interaction with vascular endothelial-cadherin. Taken together, these findings establish WARS as a gene whose mutations may cause distal hereditary motor neuropathy and alter canonical and non-canonical functions of TrpRS.

Genetic and clinical characteristics of NEFL-related Charcot-Marie-Tooth disease.

OBJECTIVES: To analyse and describe the clinical and genetic spectrum of Charcot-Marie-Tooth disease (CMT) caused by mutations in the neurofilament light polypeptide gene (NEFL). METHODS: Combined analysis of newly identified patients with NEFL-related CMT and all previously reported cases from the literature. RESULTS: Five new unrelated patients with CMT carrying the NEFL mutations P8R and N98S and the novel variant L311P were identified. Combined data from these cases and 62 kindreds from the literature revealed four common mutations (P8R, P22S, N98S and E396K) and three mutational hotspots accounting for 37 (55%) and 50 (75%) kindreds, respectively. Eight patients had de novo mutations. Loss of large-myelinated fibres was a uniform feature in a total of 21 sural nerve biopsies and 'onion bulb' formations and/or thin myelin sheaths were observed in 14 (67%) of them. The neurophysiological phenotype was broad but most patients with E90K and N98S had upper limb motor conduction velocities <38 m/s. Age of onset was ≤3 years in 25 cases. Pyramidal tract signs were described in 13 patients and 7 patients were initially diagnosed with or tested for inherited ataxia. Patients with E90K and N98S frequently presented before age 3 years and developed hearing loss or other neurological features including ataxia and/or cerebellar atrophy on brain MRI. CONCLUSIONS: NEFL-related CMT is clinically and genetically heterogeneous. Based on this study, however, we propose mutational hotspots and relevant clinical-genetic associations that may be helpful in the evaluation of NEFL sequence variants and the differential diagnosis with other forms of CMT.

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.

Defects of mutant DNMT1 are linked to a spectrum of neurological disorders.

We report a broader than previously appreciated clinical spectrum for hereditary sensory and autonomic neuropathy type 1E (HSAN1E) and a potential pathogenic mechanism for DNA methyltransferase (DNMT1) mutations. The clinical presentations and genetic characteristics of nine newly identified HSAN1E kinships (45 affected subjects) were investigated. Five novel mutations of DNMT1 were discovered; p.C353F, p.T481P, p.P491L, p.Y524D and p.I531N, all within the target-sequence domain, and two mutations (p.T481P, p.P491L) arising de novo. Recently, HSAN1E has been suggested as an allelic disorder of autosomal dominant cerebellar ataxia, deafness and narcolepsy. Our results indicate that all the mutations causal for HSAN1E are located in the middle part or N-terminus end of the TS domain, whereas all the mutations causal for autosomal dominant cerebellar ataxia, deafness and narcolepsy are located in the C-terminus end of the TS domain. The impact of the seven causal mutations in this cohort was studied by cellular localization experiments. The binding efficiency of the mutant DNMT proteins at the replication foci and heterochromatin were evaluated. Phenotypic characterizations included electromyography, brain magnetic resonance and nuclear imaging, electroencephalography, sural nerve biopsies, sleep evaluation and neuropsychometric testing. The average survival of HSAN1E was 53.6 years. [standard deviation = 7.7, range 43-75 years], and mean onset age was 37.7 years. (standard deviation = 8.6, range 18-51 years). Expanded phenotypes include myoclonic seizures, auditory or visual hallucinations, and renal failure. Hypersomnia, rapid eye movement sleep disorder and/or narcolepsy were identified in 11 subjects. Global brain atrophy was found in 12 of 14 who had brain MRI. EEGs showed low frequency (delta waves) frontal-predominant abnormality in five of six patients. Marked variability in cognitive deficits was observed, but the majority of patients (89%) developed significant cognitive deficit by the age of 45 years. Cognitive function decline often started with personality changes and psychiatric manifestations. A triad of hearing loss, sensory neuropathy and cognitive decline remains as the stereotypic presentation of HSAN1E. Moreover, we show that mutant DNMT1 proteins translocate to the cytoplasm and are prone to form aggresomes while losing their binding ability to heterochromatin during the G2 cell cycle. Our results suggest mutations in DNMT1 result in imbalanced protein homeostasis through aggresome-induced autophagy. This mechanism may explain why mutations in the sole DNA maintenance methyltransferase lead to selective central and peripheral neurodegeneration.

What we have learned from the next-generation sequencing: Contributions to the genetic diagnoses and understanding of pathomechanisms of neurodegenerative diseases.

Since its first availability in 2009, the next-generation sequencing (NGS) has been proved to be a powerful tool in identifying disease-associated variants in many neurological diseases, such as spinocerebellar ataxias, Charcot-Marie-Tooth disease, hereditary spastic paraplegia, and amyotrophic lateral sclerosis. Whole exome sequencing and whole genome sequencing are efficient for identifying variants in novel or unexpected genes responsible for inherited diseases, whereas targeted sequencing is useful in detecting variants in previously known disease-associated genes. The trove of genetic data yielded by NGS has made a significant impact on the clinical diagnoses while contributing hugely on the discovery of molecular pathomechanisms underlying these diseases. Nonetheless, elucidation of the pathogenic roles of the variants identified by NGS is challenging. Establishment of consensus guidelines and development of public genomic/phenotypic databases are thus vital to facilitate data sharing and validation.

Autosomal-recessive cerebellar ataxia caused by a novel ADCK3 mutation that elongates the protein: clinical, genetic and biochemical characterisation.

BACKGROUND: The autosomal-recessive cerebellar ataxias (ARCA) are a clinically and genetically heterogeneous group of neurodegenerative disorders. The large number of ARCA genes leads to delay and difficulties obtaining an exact diagnosis in many patients and families. Ubiquinone (CoQ10) deficiency is one of the potentially treatable causes of ARCAs as some patients respond to CoQ10 supplementation. The AarF domain containing kinase 3 gene (ADCK3) is one of several genes associated with CoQ10 deficiency. ADCK3 encodes a mitochondrial protein which functions as an electron-transfer membrane protein complex in the mitochondrial respiratory chain (MRC). METHODS: We report two siblings from a consanguineous Pakistani family who presented with cerebellar ataxia and severe myoclonus from adolescence. Whole exome sequencing and biochemical assessment of fibroblasts were performed in the index patient. RESULTS: A novel homozygous frameshift mutation in ADCK3 (p.Ser616Leufs*114), was identified in both siblings. This frameshift mutation results in the loss of the stop codon, extending the coding protein by 81 amino acids. Significant CoQ10 deficiency and reduced MRC enzyme activities in the index patient's fibroblasts suggested that the mutant protein may reduce the efficiency of mitochondrial electron transfer. CoQ10 supplementation was initiated following these genetic and biochemical analyses. She gained substantial improvement in myoclonic movements, ataxic gait and dysarthric speech after treatment. CONCLUSION: This study highlights the importance of diagnosing ADCK3 mutations and the potential benefit of treatment for patients. The identification of this new mutation broadens the phenotypic spectrum associated with ADCK3 mutations and provides further understanding of their pathogenic mechanism.

Novel C12orf65 mutations in patients with axonal neuropathy and optic atrophy.

OBJECTIVE: Charcot-Marie Tooth disease (CMT) forms a clinically and genetically heterogeneous group of disorders. Although a number of disease genes have been identified for CMT, the gene discovery for some complex form of CMT has lagged behind. The association of neuropathy and optic atrophy (also known as CMT type 6) has been described with autosomaldominant, recessive and X-linked modes of inheritance. Mutations in Mitofusin 2 have been found to cause dominant forms of CMT6. Phosphoribosylpyrophosphate synthetase-I mutations cause X-linked CMT6, but until now, mutations in the recessive forms of disease have never been identified. METHODS: We here describe a family with three affected individuals who inherited in an autosomal recessive fashion a childhood onset neuropathy and optic atrophy. Using homozygosity mapping in the family and exome sequencing in two affected individuals we identified a novel protein-truncating mutation in the C12orf65 gene, which encodes for a protein involved in mitochondrial translation. Using a variety of methods we investigated the possibility of mitochondrial impairment in the patients cell lines. RESULTS: We described a large consanguineous family with neuropathy and optic atrophy carrying a loss of function mutation in the C12orf65 gene. We report mitochondrial impairment in the patients cell lines, followed by multiple lines of evidence which include decrease of complex V activity and stability (blue native gel assay), decrease in mitochondrial respiration rate and reduction of mitochondrial membrane potential. CONCLUSIONS: This work describes a mutation in the C12orf65 gene that causes recessive form of CMT6 and confirms the role of mitochondrial dysfunction in this complex axonal neuropathy.

Charcot-Marie-Tooth disease: frequency of genetic subtypes and guidelines for genetic testing.

BACKGROUND: Charcot-Marie-Tooth disease (CMT) is a clinically and genetically heterogeneous group of diseases with approximately 45 different causative genes described. The aims of this study were to determine the frequency of different genes in a large cohort of patients with CMT and devise guidelines for genetic testing in practice. METHODS: The genes known to cause CMT were sequenced in 1607 patients with CMT (425 patients attending an inherited neuropathy clinic and 1182 patients whose DNA was sent to the authors for genetic testing) to determine the proportion of different subtypes in a UK population. RESULTS: A molecular diagnosis was achieved in 62.6% of patients with CMT attending the inherited neuropathy clinic; in 80.4% of patients with CMT1 (demyelinating CMT) and in 25.2% of those with CMT2 (axonal CMT). Mutations or rearrangements in PMP22, GJB1, MPZ and MFN2 accounted for over 90% of the molecular diagnoses while mutations in all other genes tested were rare. CONCLUSION: Four commonly available genes account for over 90% of all CMT molecular diagnoses; a diagnostic algorithm is proposed based on these results for use in clinical practice. Any patient with CMT without a mutation in these four genes or with an unusual phenotype should be considered for referral for an expert opinion to maximise the chance of reaching a molecular diagnosis.

The clinical and imaging features of FLNA positive and negative periventricular nodular heterotopia.

BACKGROUND: Periventricular nodular heterotopia (PVNH) is caused by abnormal neuronal migration, resulting in the neurons accumulate as nodules along the surface of the lateral ventricles. PVNH often cause epilepsy, psychomotor development or cognition problem. Mutations in FLNA (Filamin A) is the most common underlying genetic etiology. Our purpose is to delineate the clinical and imaging spectrum that differentiates FLNA-positive and FLNA-negative PVNH patients. METHODS: We included 21 patients with confirmed PVNH. The detailed clinical information, electroencephalography, and other clinical findings were recorded. Detailed brain MR imaging was assessed. Mutation analysis of the FLNA gene was used Sanger sequencing or a next generation sequencing based assay. RESULTS: FLNA mutations were identified in 9 patients (7 females and 2 males), including two nonsense, two splice site, three frameshift, and two missense mutations. In FLNA-positive group, 8 patients had anterior predominant bilateral symmetric presentation and only one had asymmetrical distribution and dilated ventricles. Extra-cerebral features were more often observed in FLNA-positive group than FLNA-negative group. CONCLUSION: Genetics of PVNH is heterogenous, and mutations in FLNA gene account for less than half of the patients in our cohort. Our finding between FLNA-positive and FLNA-negative patients could guide the clinicians to select relevant genetic testing.

Plasma Matrix Metalloproeteinase-9 Is Associated with Seizure and Angioarchitecture Changes in Brain Arteriovenous Malformations.

Both angiogenesis and inflammation contribute to activation of matrix metalloproeteinase-9 (MMP-9), which dissolves the extracellular matrix, disrupts the blood-brain barrier, and plays an important role in the pathogenesis of brain arteriovenous malformations (BAVMs). The key common cytokine in both angiogenesis and inflammation is interleukin 6 (IL-6). Previous studies have shown elevated systemic MMP-9 and decreased systemic vascular endothelial growth factor (VEGF) in BAVM patients. However, the clinical utility of plasma cytokines is unclear. The purpose of this study is to explore the relationship between plasma cytokines and the clinical presentations of BAVMs. Prospectively, we recruited naive BAVM patients without hemorrhage as the experimental group and unruptured intracranial aneurysm (UIA) patients as the control group. All patients received digital subtraction angiography, and plasma cytokines were collected from the lesional common carotid artery. Plasma cytokine levels were determined using a commercially available, monoclonal antibody-based enzyme-linked immunosorbent assay. Subgroup analysis based on hemorrhagic presentation and angiograchitecture was done for the BAVM group. Pearson correlations were calculated for the covariates. Means and differences for continuous and categorical variables were compared using Student's t and χ2 tests respectively. Plasma MMP-9 levels were significantly higher in the BAVM group (42,945 ± 29,991 pg/mL) than in the UIA group (28,270 ± 17,119 pg/mL) (p < 0.001). Plasma MMP-9 levels in epileptic BAVMs (57,065 ± 35,732; n = 9) were higher than in non-epileptic BAVMs (35,032 ± 28,301; n = 19) (p = 0.049). Lower plasma MMP-9 levels were found in cases of BAVM with angiogenesis and with peudophlebitis. Plasma MMP-9 is a good biomarker reflecting ongoing vascular remodeling in BAVMs. Angiogenesis and pseudophlebitis are two angioarchitectural signs that reflect MMP-9 activities and can potentially serve as imaging biomarkers for epileptic BAVMs.

Contributions of Animal Models to the Mechanisms and Therapies of Transthyretin Amyloidosis.

Transthyretin amyloidosis (ATTR amyloidosis) is a fatal systemic disease caused by amyloid deposits of misfolded transthyretin, leading to familial amyloid polyneuropathy and/or cardiomyopathy, or a rare oculoleptomeningeal amyloidosis. A good model system that mimic the disease phenotype is crucial for the development of drugs and treatments for this devastating degenerative disorder. The present models using fruit flies, worms, rodents, non-human primates and induced pluripotent stem cells have helped researchers understand important disease-related mechanisms and test potential therapeutic options. However, the challenge of creating an ideal model still looms, for these models did not recapitulates all symptoms, particularly neurological presentation, of ATTR amyloidosis. Recently, knock-in techniques was used to generate two humanized ATTR mouse models, leading to amyloid deposition in the nerves and neuropathic manifestation in these models. This review gives a recent update on the milestone, progress, and challenges in developing different models for ATTR amyloidosis research.