A missense mutation in human INSC causes peripheral neuropathy.

PAR3/INSC/LGN form an evolutionarily conserved complex required for asymmetric cell division in the developing brain, but its post-developmental function and disease relevance in the peripheral nervous system (PNS) remains unknown. We mapped a new locus for axonal Charcot-Marie-Tooth disease (CMT2) and identified a missense mutation c.209 T > G (p.Met70Arg) in the INSC gene. Modeling the INSCM70R variant in Drosophila, we showed that it caused proprioceptive defects in adult flies, leading to gait defects resembling those in CMT2 patients. Cellularly, PAR3/INSC/LGN dysfunction caused tubulin aggregation and necrotic neurodegeneration, with microtubule-stabilizing agents rescuing both morphological and functional defects of the INSCM70R mutation in the PNS. Our findings underscore the critical role of the PAR3/INSC/LGN machinery in the adult PNS and highlight a potential therapeutic target for INSC-associated CMT2.

Neuronal intranuclear inclusion disease in New Zealand: A novel discovery.

Neuronal intranuclear inclusion disease, caused by a GGC repeat expansion in the 5'-untranslated region of NOTCH2NLC, is a rare neurodegenerative condition with highly variable clinical manifestations. In recent years, the number of reported cases have increased dramatically in East Asia. We report the first four genetically confirmed cases of neuronal intranuclear inclusion disease in New Zealand, all having Polynesian ancestry (three New Zealand Maori and one Cook Island Maori). Phenotypically, they resemble cases reported from recent large East Asian cohorts.

Patisiran, an RNAi therapeutic for hereditary transthyretin-mediated amyloidosis: Sub-analysis in Taiwanese patients from the APOLLO study.

BACKGROUND AND OBJECTIVES: To examine the efficacy and safety of patisiran, an RNA interference therapeutic, in patients from Taiwan with hereditary transthyretin-mediated (hATTR) amyloidosis with polyneuropathy. METHODS: The APOLLO phase 3 trial included patients from Taiwan who received patisiran 0.3 mg/kg intravenously or placebo once every 3 weeks (q3w) for 18 months (18 M), followed by patisiran 0.3 mg/kg q3w in an ongoing global open-label extension (OLE) study. The primary endpoint was change from baseline in modified Neuropathy Impairment Score +7 (mNIS+7) at 18 M. RESULTS: Eighteen Taiwanese patients were enrolled in APOLLO (patisiran, n = 8; placebo, n = 10; all A97S gene variant) and 14 continued in the global OLE. In this Taiwanese sub-population, beneficial treatment effects at 18 M were observed in mNIS+7 (least squares mean difference in change from baseline [patisiran-placebo], -26.5 points; 95% confidence interval: -45.5, -7.5). Patients who switched from placebo to patisiran demonstrated slowing of polyneuropathy progression at month 12 in the global OLE, while those who received patisiran in APOLLO maintained the beneficial treatment effects. Patisiran had an acceptable safety profile in the Taiwanese sub-population. CONCLUSIONS: This analysis suggests that patisiran is well tolerated and may provide a substantial clinical benefit for Taiwanese patients with hATTR amyloidosis with polyneuropathy. TRIAL REGISTRATION INFORMATION: The studies were registered on the ClinicalTrials.gov. The APOLLO study ClinicalTrials.gov identifier is NCT01960348 (https://clinicaltrials.gov/ct2/show/NCT01960348), with the registration date of October 10, 2013, and the first patient was enrolled on December 13, 2013. For the global OLE, the ClinicalTrials.gov identifier is NCT02510261 (https://clinicaltrials.gov/ct2/show/NCT02510261) with the registration date of July 29, 2015, and the first patient was enrolled on July 13, 2015. CLASSIFICATION OF EVIDENCE: This study provides Class II evidence that treatment with patisiran is safe and efficacious in Taiwanese patients with hereditary transthyretin-mediated amyloidosis with polyneuropathy.

Sulfated disaccharide protects membrane and DNA damages from arginine-rich dipeptide repeats in ALS.

Hexanucleotide repeat expansion in C9ORF72 (C9) is the most prevalent mutation among amyotrophic lateral sclerosis (ALS) patients. The patients carry over ~30 to hundreds or thousands of repeats translated to dipeptide repeats (DPRs) where poly-glycine-arginine (GR) and poly-proline-arginine (PR) are most toxic. The structure-function relationship is still unknown. Here, we examined the minimal neurotoxic repeat number of poly-GR and found that extension of the repeat number led to a loose helical structure disrupting plasma and nuclear membrane. Poly-GR/PR bound to nucleotides and interfered with transcription. We screened and identified a sulfated disaccharide that bound to poly-GR/PR and rescued poly-GR/PR-induced toxicity in neuroblastoma and C9-ALS-iPSC-derived motor neurons. The compound rescued the shortened life span and defective locomotion in poly-GR/PR expressing Drosophila model and improved motor behavior in poly-GR-injected mouse model. Overall, our results reveal structural and toxicity mechanisms for poly-GR/PR and facilitate therapeutic development for C9-ALS.

Impaired cerebral interstitial fluid dynamics in cerebral autosomal dominant arteriopathy with subcortical infarcts and leucoencephalopathy.

Cerebral autosomal dominant arteriopathy with subcortical infarcts and leucoencephalopathy, caused by cysteine-altering variants in NOTCH3, is the most prevalent inherited cerebral small vessel disease. Impaired cerebral interstitial fluid dynamics has been proposed as one of the potential culprits of neurodegeneration and may play a critical role in the initiation and progression of cerebral small vessel disease. In the present study, we aimed to explore the cerebral interstitial fluid dynamics in patients with cerebral autosomal dominant arteriopathy with subcortical infarcts and leucoencephalopathy and to evaluate its association with clinical features, imaging biomarkers and disease severity of cerebral autosomal dominant arteriopathy with subcortical infarcts and leucoencephalopathy. Eighty-one participants carrying a cysteine-altering variant in NOTCH3, including 44 symptomatic cerebral autosomal dominant arteriopathy with subcortical infarcts and leucoencephalopathy patients and 37 preclinical carriers, and 21 age- and sex-matched healthy control individuals were recruited. All participants underwent brain MRI studies and neuropsychological evaluations. Cerebral interstitial fluid dynamics was investigated by using the non-invasive diffusion tensor image analysis along the perivascular space method. We found that cerebral autosomal dominant arteriopathy with subcortical infarcts and leucoencephalopathy patients exhibited significantly lower values of diffusion tensor image analysis along the perivascular space index comparing to preclinical carriers and healthy controls. For the 81 subjects carrying NOTCH3 variants, older age and presence of hypertension were independently associated with decreased diffusion tensor image analysis along the perivascular space index. The degree of cerebral interstitial fluid dynamics was strongly related to the severity of cerebral small vessel disease imaging markers, with a positive correlation between diffusion tensor image analysis along the perivascular space index and brain parenchymal fraction and negative correlations between diffusion tensor image analysis along the perivascular space index and total volume of white matter hyperintensity, peak width of skeletonized mean diffusivity, lacune numbers and cerebral microbleed counts. In addition, diffusion tensor image analysis along the perivascular space index was a significant risk factor associated with the development of clinical symptoms of stroke or cognitive dysfunction in individuals carrying NOTCH3 variants. In cerebral autosomal dominant arteriopathy with subcortical infarcts and leucoencephalopathy patients, diffusion tensor image analysis along the perivascular space index was significantly associated with Mini-Mental State Examination scores. Mediation analysis showed that compromised cerebral interstitial fluid dynamics was not only directly associated with cognitive dysfunction but also had an indirect effect on cognition by influencing brain atrophy, white matter disruption, lacunar lesions and cerebral microbleeds. In conclusion, cerebral interstitial fluid dynamics is impaired in cerebral autosomal dominant arteriopathy with subcortical infarcts and leucoencephalopathy and its disruption may play an important role in the pathogenesis of cerebral autosomal dominant arteriopathy with subcortical infarcts and leucoencephalopathy. Diffusion tensor image analysis along the perivascular space index may serve as a biomarker of disease severity for cerebral autosomal dominant arteriopathy with subcortical infarcts and leucoencephalopathy.

Biallelic COQ4 Variants in Hereditary Spastic Paraplegia: Clinical and Molecular Characterization.

BACKGROUND: Hereditary spastic paraplegias (HSP) are neurologic disorders characterized by progressive lower-extremity spasticity. Despite the identification of several HSP-related genes, many patients lack a genetic diagnosis. OBJECTIVES: The aims were to confirm the pathogenic role of biallelic COQ4 mutations in HSP and elucidate the clinical, genetic, and functional molecular features of COQ4-associated HSP. METHODS: Whole exome sequences of 310 index patients with HSP of unknown cause from three distinct populations were analyzed to identify potential HSP causal genes. Clinical data obtained from patients harboring candidate causal mutations were examined. Functional characterization of COQ4 variants was performed using bioinformatic tools, single-cell RNA sequencing, biochemical assays in cell lines, primary fibroblasts, induced pluripotent stem cell-derived pyramidal neurons, and zebrafish. RESULTS: Compound heterozygous variants in COQ4, which cosegregated with HSP in pedigrees, were identified in 7 patients from six unrelated families. Patients from four of the six families presented with pure HSP, whereas probands of the other two families exhibited complicated HSP with epilepsy or with cerebellar ataxia. In patient-derived fibroblasts and COQ4 knockout complementation lines, stable expression of these missense variants exerted loss-of-function effects, including mitochondrial reactive oxygen species accumulation, decreased mitochondrial membrane potential, and lower ubiquinone biosynthesis. Whereas differentiated pyramidal neurons expressed high COQ4 levels, coq4 knockdown zebrafish displayed severe motor dysfunction, reflecting motor neuron dysregulation. CONCLUSIONS: Our study confirms that loss-of-function, compound heterozygous, pathogenic COQ4 variants are causal for autosomal recessive pure and complicated HSP. Moreover, reduced COQ4 levels attributable to variants correspond with decreased ubiquinone biosynthesis, impaired mitochondrial function, and higher phenotypic disease severity. © 2023 International Parkinson and Movement Disorder Society.

Tumefactive Demyelination Lesions: Report on three cases.

PURPOSE: Tumefactive demyelination (TD) lesion and its subtype Balo's concentric sclerosis (BCS), are rare manifestations of central nervous system demyelinating disease. Because of its rarity, physicians might hesitate in reaching a diagnosis or initiating steroid pulse therapy. This study aims at pinpointing the key neuroimaging features to distinguish TD lesions from surgical conditions, and illustrating the clinical outcomes of patients with TD lesions. CASE REPORT: Two of the three patients had solitary TD lesions, one 47-year-old man presenting with newly onset seizure and another 54-year-old women suffering from progressive hemiparesis. The male patient underwent craniotomy for mass excision without further steroid therapy, while the female patient received methylprednisolone pulse therapy only. Both patients remained free of clinical and radiological relapses over the past 6-7 years, leading to the diagnosis of clinically isolated syndrome. The third case is a 30-year-old woman with subacute onset of dysarthria and hemiparesis. She had two BCS lesions along with other demyelinating lesions in the juxtacortical and periventricular regions, cerebellar peduncles, and spinal cord, fulfilling dissemination in time and space. Her neurological deficits resolved after pulse therapy, and she received long-term disease modifying therapy for multiple sclerosis. CONCLUSION: This study underscores the diverse neuroimaging and clinical presentations of patients with TD lesions, and emphasizes the importance of clinical vigilance regarding this rare condition.

Contribution of the APOE Genotype to Cognitive Impairment in Individuals With NOTCH3 Cysteine-Altering Variants.

BACKGROUND: Cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) is the most prevalent monogenic cerebral small-vessel disease. Phenotype variability in CADASIL suggests the possible role of genetic modifiers. We aimed to investigate the contributions of the APOE genotype and Neurogenic locus notch homolog protein 3 (NOTCH3) variant position to cognitive impairment associated with CADASIL. METHODS AND RESULTS: Patients with the cysteine-altering NOTCH3 variant were enrolled in a cross-sectional study, including the Mini-Mental State Examination (MMSE), brain magnetic resonance imaging, and APOE genotyping. Cognitive impairment was defined as an MMSE score <24. The associations between the MMSE score and genetic factors were assessed using linear regression models. Bayesian adjustment for confounding was used to identify clinical confounders. A total of 246 individuals were enrolled, among whom 210 (85%) harbored the p.R544C variant, 96 (39%) had cognitive impairment, and 150 (61%) had a history of stroke. The APOE ɛ2 allele was associated with a lower MMSE score (adjusted B, -4.090 [95% CI, -6.708 to -1.473]; P=0.023), whereas the NOTCH3 p.R544C variant was associated with a higher MMSE score (adjusted B, 2.854 [95% CI, 0.603-5.105]; P=0.0132) after adjustment for age, education, and history of ischemic stroke. Mediation analysis suggests that the associations between the APOE ɛ2 allele and MMSE score and between the NOTCH3 p.R544C variant and MMSE score are mediated by mesial temporal atrophy and white matter hyperintensity, respectively. CONCLUSIONS: APOE genotype may modify cognitive impairment in CADASIL, whereby individuals carrying the APOE ɛ2 allele may present a more severe cognitive impairment.

Phenotypic Heterogeneity in Patients with Mutations in the Mitochondrial Complex I Assembly Gene NDUFAF5.

BACKGROUND: Rare mutations in NADH:ubiquinone oxidoreductase complex assembly factor 5 (NDUFAF5) are linked to Leigh syndrome. OBJECTIVE: We aimed to describe clinical characteristics and functional findings in a patient cohort with NDUFAF5 mutations. METHODS: Patients with biallelic NDUFAF5 mutations were recruited from multi-centers in Taiwan. Clinical, laboratory, radiological, and follow-up features were recorded and mitochondrial assays were performed in patients' skin fibroblasts. RESULTS: Nine patients from seven unrelated pedigrees were enrolled, eight homozygous for c.836 T > G (p.Met279Arg) in NDUFAF5 and one compound heterozygous for p.Met279Arg. Onset age had a bimodal distribution. The early-onset group (age <3 years) presented with psychomotor delay, seizure, respiratory failure, and hyponatremia. The late-onset group (age ≥5 years) presented with normal development, but slowly progressive dystonia. Combing 25 previously described patients, the p.Met279Arg variant was exclusively identified in Chinese ancestry. Compared with other groups, patients with late-onset homozygous p.Met279Arg were older at onset (P = 0.008), had less developmental delay (P = 0.01), less hyponatremia (P = 0.01), and better prognosis with preserved ambulatory function into early adulthood (P = 0.01). Bilateral basal ganglia necrosis was a common radiological feature, but brainstem and spinal cord involvement was more common with early-onset patients (P = 0.02). A modifier gene analysis showed higher concomitant mutation burden in early-versus late-onset p.Met279Arg homozygous cases (P = 0.04), consistent with more impaired mitochondrial function in fibroblasts from an early-onset case than a late-onset patient. CONCLUSIONS: The p.Met279Arg variant is a common mutation in our population with phenotypic heterogeneity and divergent prognosis based on age at onset. © 2023 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

Biallelic DDHD2 mutations in patients with adult-onset complex hereditary spastic paraplegia.

OBJECTIVE: Hereditary spastic paraplegias (HSPs) are a group of inherited neurodegenerative disorders characterized by slowly progressive lower limb spasticity and weakness. HSP type 54 (SPG54) is autosomal recessively inherited and caused by mutations in the DDHD2 gene. This study investigated the clinical characteristics and molecular features of DDHD2 mutations in a cohort of Taiwanese patients with HSP. METHODS: Mutational analysis of DDHD2 was performed for 242 unrelated Taiwanese patients with HSP. The clinical, neuroimaging, and genetic features of the patients with biallelic DDHD2 mutations were characterized. A cell-based study was performed to assess the effects of the DDHD2 mutations on protein expression. RESULTS: SPG54 was diagnosed in three patients. Among them, two patients carried compound heterozygous DDHD2 mutations, p.[R112Q];[Y606*] and p.[R112Q];[p.D660H], and the other one was homozygous for the DDHD2 p.R112Q mutation. DDHD2 p.Y606* is a novel mutation, whereas DDHD2 p.D660H and p.R112Q have been reported in the literature. All three patients manifested adult onset complex HSP with additional cerebellar ataxia, polyneuropathy, or cognitive impairment. Brain proton magnetic resonance spectroscopy revealed an abnormal lipid peak in thalamus of all three patients. In vitro studies demonstrated that all the three DDHD2 mutations were associated with a considerably lower DDHD2 protein level. INTERPRETATION: SPG54 was detected in approximately 1.2% (3 of 242) of the Taiwanese HSP cohort. This study expands the known mutational spectrum of DDHD2, provides molecular evidence of the pathogenicity of the DDHD2 mutations, and underlines the importance of considering SPG54 as a potential diagnosis of adult-onset HSP.

Identification of m.3243A>G mitochondrial DNA mutation in patients with cerebellar ataxia.

BACKGROUND: The mitochondrial DNA m.3243A>G mutation can affect mitochondrial function and lead to a wide phenotypic spectrum, including mitochondrial encephalopathy with lactic acidosis and stroke-like episodes (MELAS) syndrome, diabetes mellitus, hearing impairment, cardiac involvement, epilepsy, migraine, myopathy, and cerebellar ataxia. However, m.3243A>G has been rarely reported in patients with cerebellar ataxia as their predominant manifestation. The aim of this study is to investigate the prevalence and clinical features of m.3243A>G in a Taiwanese cohort of cerebellar ataxia with unknown genetic diagnosis. METHODS: This retrospective cohort study conducted the mutation analysis of m.3243A>G by polymerase chain reaction and restriction fragment length polymorphism (PCR-RFLP) in 232 unrelated Han Chinese patients with genetically-undetermined cerebellar ataxia. The clinical presentation and neuroimaging features of patients with m.3243A>G mutation-related cerebellar ataxia were characterized. RESULTS: We identified two patients harboring m.3243A>G mutation. These patients have suffered from apparently sporadic and slowly progressive cerebellar ataxia since age 52 and 35 years, respectively. Both patients had diabetes mellitus and/or hearing impairment. The neuroimaging studies revealed generalized brain atrophy with predominantly cerebellar involvement in both individuals and bilateral basal ganglia calcifications in one of the patients. CONCLUSION: Mitochondrial m.3243A>G mutation accounted for 0.9% (2/232) of genetically-undetermined cerebellar ataxia in the Han Chinese cohort in Taiwan. These findings highlight the importance of investigating m.3243A>G in patients with genetically-undetermined cerebellar ataxia.

Baseline P2Y12 reactivity, kidney function, and CYP2C19 genotype determine clopidogrel responsiveness in acute stroke.

Clopidogrel is the most-widely used platelet P2Y12-inhibitor for secondary-prevention of ischemic stroke. Platelet P2Y12 reactivity before and after inhibitors can be measured with blood sampling by commercialized system. We aimed to evaluate (1) whether high-on-clopidogrel platelet P2Y12 reactivity (HCPR) is associated with short-term vascular events and (2) the predictors of HCPR in acute stroke. The inclusion criterion was patients with acute stroke who received clopidogrel within 12-48 h after the onset. Platelet reactivity was assayed at baseline and after clopidogrel treatment using the VerifyNow system. The primary endpoint was recurrent ischemic events within 21 days after stroke. Among 190 patients, 32(16.9%) had recurrent ischemic stroke. Multivariate analyses showed that HCPR was significantly associated with the short-term events with an odds-ratio of 2.5 (95% CI 1.1-5.7, p = 0.027). Patients with HCPR had significantly higher frequencies of high baseline platelet P2Y12 reactivity, impaired kidney function, and carrying one or two CYP2C19 loss-of-function alleles. A poor clopidogrel response score combining these factors was developed. Ten percent of patients with score 0, 20.3% of those with score 1, 38.3% of those with score 2, and 66.7% of those with score 3 had HCPR (χ2-test, p < 0.001). Multivariate analyses showed that, compared with the score-0 group, the score-2 and -3 groups had higher risks of HCPR with hazard-ratios of 5.4 (95% CI 1.5-20.3, p = 0.012) and 17.4 (95% CI 3.4-88.9, p = 0.001) for developing recurrent ischemic strokes. The study emphasized the role of HCPR in ischemic stroke. We also developed an HCPR risk score, which could be used in clinical practice or trials, potentially with more precision, to weigh the clinical benefit of a tailored antiplatelet-strategy for patients with stroke.

NOTCH2NLC GGC Repeat Expansion in Patients With Vascular Leukoencephalopathy.

BACKGROUND: Neuronal intranuclear inclusion disease (NIID), caused by GGC (guanine-guanine-cytosine) repeat expansion in NOTCH2NLC, has several clinical and radiological features akin to cerebral small vessel disease (cSVD). The present study tested the hypothesis that NOTCH2NLC GGC expansion may contribute to cSVD. METHODS: One hundred and ninety-seven unrelated patients with genetically unsolved vascular leukoencephalopathy without NOTCH3, HTRA1, and mitochondrial m.3243A>G mutations and 730 healthy individuals were screened for NOTCH2NLC GGC repeat expansion using repeat-primed polymerase chain reaction, fragment analysis, Southern blot analysis, or nanopore sequencing with Cas9 (CRISPR associated protein 9)-mediated enrichment. The clinical and neuroimaging features of the patients were compared between individuals with and without NOTCH2NLC GGC repeat expansion. RESULTS: Six of the 197 (3.0%) patients with unsolved vascular leukoencephalopathy and none of the controls carried the GGC repeat expansion (P=0.00009). Skin biopsy of 1 patient revealed eosinophilic, ubiquitin-positive, and p62-positive intranuclear inclusions in the cells of sweat gland and capillary, providing pathologic evidence for the involvement of small vessels in NIID. For the 6 patients, gait disturbance and cognitive decline were common manifestations with a median onset age of 65 (59-69) years. They all had multiple neuroimaging features suggestive of cSVD, including diffuse white matter hyperintensities, lacunes, and enlarged perivascular space in all 6 patients, cerebral microbleeds in 5, and old intracerebral hemorrhage in 4. Four patients had linear hyperintensity in the corticomedullary junction on diffusion-weighted imaging-the characteristic neuroimaging feature of NIID. There was no difference in the severity of cSVD imaging features between the patients with and without the GGC expansion but more pronounced brain atrophy in the patients with the GGC expansion. CONCLUSIONS: NOTCH2NLC GGC repeat expansion accounted for 3% of genetically unsolved Taiwanese vascular leukoencephalopathy cases after excluding participants with cerebral autosomal dominant arteriopathy with subcortical infarct and leukoencephalopathy (CADASIL), cerebral autosomal recessive arteriopathy with subcortical infarcts and leukoencephalopathy (CARASIL), and mitochondrial encephalomyopathy, lactic acidosis and stroke-like episodes (MELAS). NIID should be considered in patients manifesting cSVD, especially in those with characteristic neuroimaging feature of NIID.

Update on the Epidemiology, Pathogenesis, and Biomarkers of Cerebral Autosomal Dominant Arteriopathy With Subcortical Infarcts and Leukoencephalopathy.

Cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) is the most common monogenic disorder of the cerebral small blood vessels. It is caused by mutations in the NOTCH3 gene on chromosome 19, and more than 280 distinct pathogenic mutations have been reported to date. CADASIL was once considered a very rare disease with an estimated prevalence of 1.3-4.1 per 100,000 adults. However, recent large-scale genomic studies have revealed a high prevalence of pathogenic NOTCH3 variants among the general population, with the highest risk being among Asians. The disease severity and age at onset vary significantly even among individuals who carry the same NOTCH3 mutations. It is still unclear whether a significant genotype-phenotype correlation is present in CADASIL. The accumulation of granular osmiophilic material in the vasculature is a characteristic feature of CADASIL. However, the exact pathogenesis of CADASIL remains largely unclear despite various laboratory and clinical observations being made. Major hypotheses proposed so far have included aberrant NOTCH3 signaling, toxic aggregation, and abnormal matrisomes. Several characteristic features have been observed in the brain magnetic resonance images of patients with CADASIL, including subcortical lacunar lesions and white matter hyperintensities in the anterior temporal lobe or external capsule, which were useful in differentiating CADASIL from sporadic stroke in patients. The number of lacunes and the degree of brain atrophy were useful in predicting the clinical outcomes of patients with CADASIL. Several promising blood biomarkers have also recently been discovered for CADASIL, which require further research for validation.

Clinical and genetic characterization of NIPA1 mutations in a Taiwanese cohort with hereditary spastic paraplegia.

OBJECTIVE: NIPA1 mutations have been implicated in hereditary spastic paraplegia (HSP) as the cause of spastic paraplegia type 6 (SPG6). The aim of this study was to investigate the clinical and genetic features of SPG6 in a Taiwanese HSP cohort. METHODS: We screened 242 unrelated Taiwanese patients with HSP for NIPA1 mutations. The clinical features of patients with a NIPA1 mutation were analyzed. Minigene-based splicing assay, RT-PCR analysis on the patients' RNA, and cell-based protein expression study were utilized to assess the effects of the mutations on splicing and protein expression. RESULTS: Two patients were identified to carry a different heterozygous NIPA1 mutation. The two mutations, c.316G>A and c.316G>C, are located in the 3' end of NIPA1 exon 3 near the exon-intron boundary and putatively lead to the same amino acid substitution, p.G106R. The patient harboring NIPA1 c.316G>A manifested spastic paraplegia, epilepsy and schizophrenia since age 17 years, whereas the individual carrying NIPA1 c.316G>C had pure HSP since age 12 years. We reviewed literature and found that epilepsy was present in multiple individuals with NIPA1 c.316G>A but none with NIPA1 c.316G>C. Functional studies demonstrated that both mutations did not affect splicing, but only the c.316G>A mutation was associated with a significantly reduced NIPA1 protein expression. INTERPRETATION: SPG6 accounted for 0.8% of HSP cases in the Taiwanese cohort. The NIPA1 c.316G>A and c.316G>C mutations are associated with adolescent-onset complex and pure form HSP, respectively. The different effects on protein expression of the two mutations may be associated with their phenotypic discrepancy.

Reduced-penetrance Huntington's disease-causing alleles with 39 CAG trinucleotide repeats could be a genetic factor of amyotrophic lateral sclerosis.

BACKGROUND: Expanded HTT alleles with 40 or more CAG repeats were recently found to be a rare cause of frontotemporal dementia and amyotrophic lateral sclerosis (ALS) spectrum diseases. The aim of this study was to investigate the role of HTT repeat expansions in a Taiwanese cohort with ALS. METHODS: We analyzed the numbers of CAG repeats in exon 1 of HTT in a cohort of 410 Taiwanese patients with ALS and 1514 control individuals by utilizing polymerase chain reaction and amplicon fragment length analysis. RESULTS: Only one of the 410 ALS patients carried a reduced-penetrance HD-causing allele with 39 CAG repeats, and none had an expanded HTT CAG repeats ≥40. The patient presented with rapidly progressive bulbar-onset ALS with disease onset at the age of 64 years. He had neither chorea nor cognitive impairment. He had a family history of chorea, but no other family member manifested with ALS. None of the 1514 control individuals carried an HTT expanded allele with CAG repeats larger than 37 repeats. CONCLUSION: The HTT allele with 39 CAG repeats could be a genetic factor linked to ALS susceptibility.

Clinical and genetic characterization of NEFL-related neuropathy in Taiwan.

BACKGROUND: Mutations in the neurofilament light polypeptide gene (NEFL) are an uncommon cause of Charcot-Marie-Tooth disease (CMT). The aim of this study is to elucidate the clinical characteristics and genetic spectrum of NEFL-related neuropathy in a Taiwanese CMT cohort. METHODS: Mutational analysis of the coding regions of NEFL was performed by Sanger sequencing or targeted resequencing. Twenty-one patients from nine CMT pedigrees, identified from a cohort of 508 unrelated CMT patients, were found to have a NEFL mutation. Genetic, clinical and electrophysiological features were analyzed. RESULTS: Six NEFL mutations were identified, including two novel ones (p.P8S, p.N98Y). NEFL p.E396K was the most common mutation, accounting for 33.3% of the patients in our cohort. All patients manifested sensorimotor polyneuropathy with a mean age of disease onset of 13.5 ± 9.6 (1-40) years. Their motor nerve conduction velocities (MNCVs) of the ulnar nerve ranged from 22.1 to 48.7 m/s. Seventy percent of the patients could be classified as intermediate CMT with ulnar MNCVs between 25 and 45 m/s. Six of the 21 patients (28.6%) had additional features of central nervous system (CNS) involvement, including motor developmental delay, spasticity, cerebellar signs, neuropathic pain and scoliosis. CONCLUSION: NEFL mutations account for 1.8% (9/508) of the CMT patients in Taiwan. The present study delineates the clinical and genetic characteristics of NEFL-related neuropathy in Taiwan, and highlights that ulnar MNCV above 25 m/s and CNS involvement may serve as diagnostic clues for NEFL-related neuropathy.

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.