Sca-1 Research Articles

Use of single guided Cas9 nickase to facilitate precise and efficient genome editing in human iPSCs

Cas9 nucleases permit rapid and efficient generation of gene-edited cell lines. However, in typical protocols, mutations are intentionally introduced into the donor template to avoid the cleavage of donor template or re-cleavage of the successfully edited allele, compromising the fidelity of the isogenic lines generated. In addition, the double-stranded breaks (DSBs) used for editing can introduce undesirable “on-target” indels within the second allele of successfully modified cells via non-homologous end joining (NHEJ). To address these problems, we present an optimized protocol for precise genome editing in human iPSCs that employs (1) single guided Cas9 nickase to generate single-stranded breaks (SSBs), (2) transient overexpression of BCL-XL to enhance survival post electroporation, and (3) the PiggyBac transposon system for seamless removal of dual selection markers. We have used this method to modify the length of the CAG repeat contained in exon 7 of PPP2R2B. When longer than 43 triplets, this repeat causes the neurodegenerative disorder spinocerebellar ataxia type 12 (SCA12); our goal was to seamlessly introduce the SCA12 mutation into a human control iPSC line. With our protocol, ~ 15% of iPSC clones selected had the desired gene editing without “on target” indels or off-target changes, and without the deliberate introduction of mutations via the donor template. This method will allow for the precise and efficient editing of human iPSCs for disease modeling and other purposes.

The Electrophysiological Findings in Spinocerebellar Ataxia Type 6: Evidence From 24 Patients.

Peripheral neuropathy has been reported commonly in several spinocerebellar ataxia (SCA) types. To date, there is a lack of robust evidence for neuropathy or neuronopathy in SCA type 6 (SCA6). Here, we aim to evaluate the presence of neuropathy or neuronopathy in a cohort of SCA6 patients. Twenty-four individuals with genetically confirmed SCA6 underwent detailed neurophysiological assessment. This included nerve conduction studies, and in some, cutaneous silent periods, blink reflexes, tilt table tests, quantitative sudomotor axon reflex tests, and somatosensory (median and tibial) evoked potentials. Mean age was 56.1 years (range, 22-94 years) at the time of testing. Four patients were presymptomatic of SCA6 at recruitment. The mean disease duration of symptomatic patients was 11.9 years (range, 1-40 years). Most patients (79.2%, 19/24) had no neurophysiological evidence of a peripheral neuropathy. One with impaired glucose tolerance had mild, large, and small fiber sensorimotor polyneuropathy. One elderly patient had length-dependent axonal sensorimotor polyneuropathy. Two had minor sensory abnormalities (one had type II diabetes and previous chemotherapy). One other had minor small fiber abnormalities. Ten patients (41.7%) had median neuropathies at the wrist. All somatosensory evoked potential (15/15), and most autonomic function tests (13/14) were normal. A large proportion of subjects (79.2%) in our cohort had no evidence of large or small fiber neuropathy. This study does not support the presence of neuropathy or neuronopathy as a common finding in SCA6 and confirms the importance of considering comorbidities as the cause of neurophysiological abnormalities.

Generation of a human induced pluripotent stem cell line JHUi003-A with homozygous mutation for spinocerebellar ataxia type 12 using genome editing

Spinocerebellar ataxia type 12 (SCA12) is caused by a CAG expansion mutation in PPP2R2B, a gene encoding a brain-specific regulatory unit of protein phosphatase 2A (PP2A); while normal alleles carry 4 to 31 triplets, the disease alleles carry 43 to 78 triplets. Here, by CRISPR/Cas9 genome editing, we have generated a human homozygous SCA12 iPSC line with 69 and 72 triplets for each allele. The homozygous SCA12 iPSCs have normal karyotype, express pluripotency markers and are able to differentiate into the three germ layers.

Does SCA45 Cause Very Late-Onset Pure Cerebellar Ataxia?

Spinocerebellar ataxias (SCAs) are a large group of genetically and phenotypically heterogeneous autosomal dominant, neurodegenerative disorders manifesting with progressive cerebellar ataxia usually with adult-onset.1 Currently, 48 subtypes of SCAs are described; of which, for 40 SCAs, the genes have been identified. The most frequent types are related to coding repeat expansions including SCA1, SCA2, SCA3, SCA6, and SCA7. However, for unusual SCA types, whole exome sequencing (WES) is necessary to identify the genetic cause. Late-onset cerebellar ataxia can be caused by several genetic mutations, but a large percentage of patients remain undiagnosed after WES. The authors would like to thank FAPESP (Fundação de Amparo à Pesquisa do Estado de São Paulo) for having funded this study.

Cognitive impairment in spinocerebellar ataxia type 12

IntroductionCognitive impairment has now been recognised to be present in patients with several of spinocerebellar ataxias (SCAs). Cognitive impairment in patients with spinocerebellar ataxia type 12 has not been evaluated. ObjectiveTo evaluate the cognitive impairment in patients diagnosed with spinocerebellar ataxia type 12 (SCA12). MethodsWe conducted a cross sectional study and enrolled 30 (20 male and 10 female) genetically confirmed SCA12 patients and 30 healthy, age, gender and education matched individuals as controls. Cognitive domains were tested using a battery of validated neurocognitive tests. ResultMean age of patients was 51.6 ± 8.0 years and mean disease duration was 5.3 ± 3.0 years. Mean International Cooperative Ataxia Rating Scale (ICARS) score was 29.8 ± 12.5. SCA 12 patients scored significantly lower than controls in executive function and new learning ability. Other tested cognitive domains were also affected but did not reach statistical significance. Age, age at onset, severity of ataxia, disease duration and CAG repeat length did not correlate with cognitive impairment. ConclusionCognitive impairment is a part of the spectrum of SCA12 and is characterized by dysfunction in executive function and new learning ability even early in the course of disease.

Porphyrins ameliorate spinocerebellar ataxia type 36 GGCCTG repeat expansion-mediated cytotoxicity

Spinocerebellar ataxia type 36 (SCA36) is a noncoding repeat expansion disorder caused by an expanded GGCCTG hexanucleotide repeat (HNR) in the first intron of the nucleolar protein 56 (NOP56) gene. Another disease-causing HNR expansion derived from C9orf72-linked GGGGCC repeats that form G-quadruplexes (GQs) affects genetic stability, RNA splicing, and mRNA localization within neurites. The porphyrin derivative TMPyP4 was shown to ameliorate RNA toxicity caused by GGGGCC HNR expansion by binding and distorting RNA GQ structures. SCA36 GGCCTG HNRs can potentially form RNA GQs; therefore, we investigated whether several porphyrin derivatives could reduce RNA toxicity in SCA36 cell models. Among these, sodium copper chlorophyllin and hemin chloride, which have already been used in clinical practice, reduced SCA36 GGCCTG expansion-mediated cytotoxicity and improved cell viability. These data suggest that porphyrins are potential therapeutic candidates against SCA36 pathogenesis.

The Complex Genetic Landscape of Hereditary Ataxias in Turkey and Implications in Clinical Practice.

The genetic and epidemiological features of hereditary ataxias have been reported in several populations; however, Turkey is still unexplored. Due to high consanguinity, recessive ataxias are more common in Turkey than in Western European populations. To identify the prevalence and genetic structure of hereditary ataxias in the Turkish population. Our cohort consisted of 1296 index cases and 324 affected family members. Polymerase chain reaction followed by Sanger sequencing or fragment analysis were performed to screen for the trinucleotide repeat expansions in families with a dominant inheritance pattern, as well as in sporadic cases. The expansion in the frataxin (FXN) gene was tested in all autosomal recessive cases and in sporadic cases with a compatible phenotype. Whole-exome sequencing was applied to 251 probands, selected based on the family history, age of onset, and phenotype. Mutations in known ataxia genes were identified in 30% of 1296 probands. Friedreich's ataxia was found to be the most common recessive ataxia in Turkey, followed by autosomal recessive spastic ataxia of Charlevoix-Saguenay. Spinocerebellar ataxia types 2 and 1 were the most common dominant ataxias. Whole-exome sequencing was performed in 251 probands with an approximate diagnostic yield of 50%. Forty-eight novel variants were found in a plethora of genes, suggesting a high heterogeneity. Variants of unknown significance were discussed in light of clinical data. With the large sample size recruited across the country, we consider that our results provide an accurate picture of the frequency of hereditary ataxias in Turkey. © 2021 International Parkinson and Movement Disorder Society.

Rapid Molecular Screen of Spinocerebellar Ataxia Types 1, 2, and 3 by Triplet-Primed PCR and Melting Curve Analysis

The autosomal-dominantly inherited spinocerebellar ataxias (SCAs) can be caused by dynamic mutations of short tandem repeats within various genes. Due to the significant clinical overlap among the various SCA types, molecular screening of multiple genetic loci by fluorescent PCR and capillary electrophoresis is necessary to identify the causative repeat expansion. We describe a simple, rapid, and inexpensive strategy to screen for CAG repeat expansion mutations at the ATXN1, ATXN2, and ATXN3 loci using melting curve analysis (MCA) of triplet-primed PCR products. Plasmid DNAs of known repeat sizes were used to generate threshold melt peak temperatures, which rapidly and effectively distinguish samples carrying an expanded allele from those carrying non-expanded alleles. MCA-positive samples were confirmed by capillary electrophoresis sizing of the triplet-primed PCR products. All three assays achieved 100% sensitivity with 95% confidence intervals (CI) of 67.86-100 (SCA1), 74.65-100 (SCA2), and 91.58-100 (SCA3). The SCA1 assay also achieved 100% specificity (95% CI: 97.52-100), while the SCA2 and SCA3 assays achieved specificity of 99.46% (95% CI: 96.56-99.97) and 99.32% (95% CI: 95.70-99.96), respectively. These screening assays provide robust and highly accurate detection of expanded alleles and are amenable to large-scale screening while minimizing the need for capillary electrophoresis sizing for every sample.

Establish a Nomogram to Predict Falls in Spinocerebellar Ataxia Type 3.

Purpose: Falls are common and are frequently accompanied by injuries in patients with spinocerebellar ataxias type 3 (SCA3). We explored which factors could predict falls in a cohort of patients with SCA3 and developed a nomogram model to predict the first fall in non-fallen patients with SCA3.Method: We conducted a prospective cohort study. Forty-four non-fallen patients with SCA3 were followed up until the first fall or November 5, 2020, whichever came first. Univariate and multivariate Cox proportional hazard regression analyses were applied to explore the predictive factors of falls in patients with SCA3. A nomogram model predicting the no-fall probabilities at 3, 6, 12, and 24 months was formulated based on the results of the multivariate Cox analysis. Internal validation was conducted to assess the discrimination and calibration of the final model using bootstrapping with 1,000 resamples.Results: Multivariate Cox proportional hazard regression showed that the presence of dystonia, hyperreflexia, urinary incontinence, and hidrosis and the number of abnormal eye movements predicted a more rapid progression to falls in patients with SCA3. The nomogram model showed good discrimination with a concordance index of 0.83 and good calibration.Conclusion: Patients with dystonia, hyperreflexia, urinary incontinence, and hidrosis, and more types of abnormal eye movement had a more rapid progression to falls in SCA3.

Abnormal eye movements in spinocerebellar ataxia type 3

BackgroundAbnormal eye movements are common in spinocerebellar ataxias Type 3 (SCA3). We conducted the research to explore the frequency of abnormal eye movements in Chinese patients with SCA3, to compare the demographic and clinical characteristics between SCA3 patients with and without each type of abnormal eye movement, and to explore the correlation between abnormal eye movements and the severity of ataxia.MethodsSeventy-four patients with SCA3 were enrolled in this cross-sectional study. Six types of abnormal eye movements including impaired smooth pursuit, increased square-wave jerks (SWJ), gaze-evoked nystagmus (GEN), slowing of saccades, saccadic hypo/hypermetria and supranuclear gaze palsy were evaluated by experienced neurologists. The severity of ataxia was evaluated by Scale for the Assessment and Rating of Ataxia (SARA).ResultsThe prevalence of impaired smooth pursuit, increased SWJ, GEN, slowing of saccades, saccadic hypo/hypermetria and supranuclear gaze palsy in Chinese SCA3 patients was 28.4, 13.5, 78.4, 41.9, 23.0, and 5.4%, respectively. SCA3 patients with GEN had higher scores of International Cooperative Ataxia Rating Scale (ICARS-IV) and total ICARS, and longer length of CAG repeat than patients without GEN. SCA3 patients with slowing of saccades had a longer disease duration, higher scores of ICARS-I, ICARS-II, total ICARS and SARA than patients without slowing of saccades. SCA3 patients with saccadic hypo/hypermetria had higher scores of ICARS-III, ICARS-IV, and SARA than patients without saccadic hypo/hypermetria. The demographic and clinical characteristics did not differ significantly between SCA3 patients with and without impaired smooth pursuit, increased SWJ, or supranuclear gaze palsy. Multivariate linear regression showed that the number of abnormal eye movements (0–6), disease duration, Hamilton Depression Rating Scale-24 (HDRS-24) score, and CAG repeat length were positively correlated with SARA score, whereas Montreal Cognitive Assessment (MoCA) score was negatively correlated with SARA score in SCA3.ConclusionsAn increased number of abnormal eye movement types correlated with the severity of ataxia in SCA3.

Development of SARAhome , a New Video-Based Tool for the Assessment of Ataxia at Home.

Clinical scales such as the Scale for the Assessment and Rating of Ataxia (SARA) cannot be used to study ataxia at home or to assess daily fluctuations. The objective of the current study was to develop a video-based instrument, SARAhome , for measuring ataxia severity easily and independently at home. Based on feasibility of self-application, we selected 5 SARA items (gait, stance, speech, nose-finger test, fast alternating hand movements) for SARAhome (range, 0-28). We compared SARAhome items with total SARA scores in 526 patients with spinocerebellar ataxia types 1, 2, 3, and 6 from the EUROSCA natural history study. To prospectively validate the SARAhome , we directly compared the self-applied SARAhome and the conventional SARA in 50 ataxia patients. To demonstrate feasibility of independent home recordings in a pilot study, 12 ataxia patients were instructed to obtain a video each morning and evening over a period of 14 days. All videos were rated offline by a trained rater. SARAhome extracted from the EUROSCA baseline data was highly correlated with conventional SARA (r= 0.9854, P< 0.0001). In the prospective validation study, the SARAhome was highly correlated with the conventional SARA (r= 0.9254, P< 0.0001). Five of 12 participants of the pilot study obtained a complete set of 28 evaluable videos. Seven participants obtained 13-27 videos. The intraindividual differences between the lowest and highest SARAhome scores ranged from 1 to 5.5. The SARAhome and the conventional SARA are highly correlated. Application at home is feasible. There was a considerable degree of intraindividual variability of the SARAhome scores. © 2021 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

Small molecule targeting r(UGGAA)n disrupts RNA foci and alleviates disease phenotype in Drosophila model

Synthetic small molecules modulating RNA structure and function have therapeutic potential for RNA diseases. Here we report our discovery that naphthyridine carbamate dimer (NCD) targets disease-causing r(UGGAA)n repeat RNAs in spinocerebellar ataxia type 31 (SCA31). Structural analysis of the NCD-UGGAA/UGGAA complex by nuclear magnetic resonance (NMR) spectroscopy clarifies the mode of binding that recognizes four guanines in the UGGAA/UGGAA pentad by hydrogen bonding with four naphthyridine moieties of two NCD molecules. Biological studies show that NCD disrupts naturally occurring RNA foci built on r(UGGAA)n repeat RNA known as nuclear stress bodies (nSBs) by interfering with RNA–protein interactions resulting in the suppression of nSB-mediated splicing events. Feeding NCD to larvae of the Drosophila model of SCA31 alleviates the disease phenotype induced by toxic r(UGGAA)n repeat RNA. These studies demonstrate that small molecules targeting toxic repeat RNAs are a promising chemical tool for studies on repeat expansion diseases.

Progression of Cerebellar Atrophy in Spinocerebellar Ataxia Type 2 Gene Carriers: A Longitudinal MRI Study in Preclinical and Early Disease Stages.

Spinocerebellar ataxias type 2 (SCA2) is an autosomal dominant inherited disease caused by expanded trinucleotide repeats (≥32 CAG) within the coding region of ATXN2 gene. Age of disease onset primarily depends on the length of the expanded region. The majority of subjects carrying the mutation remain free of clinical signs for few decades (“pre-symptomatic” stage), but in proximity of disease onset subtle neurophysiological, cognitive, and structural brain imaging changes may occur. Aims of the present study are to determine the time-window in which early clinical and neurodegenerative MRI changes may be identified, and to evaluate the rate of the disease progression in both preclinical and early disease phases. We performed a 1-year longitudinal study in 42 subjects: 14 SCA2 patients (mean age 39 years, disease duration 7 years, SARA score 9 points), 13 presymptomatic SCA2 subjects (preSCA2, mean age 39 years, expected time to disease onset 16 years), and 15 gene-negative healthy controls (mean age 33 years). All participants underwent genetic test, neurological examination, cognitive tests, and brain MRI. Evaluations were repeated at 1-year interval. Baseline MRI evaluations in SCA2 patients showed significant atrophy in cerebellum, brainstem, basal ganglia and cortex compared to controls, while preSCA2 subjects had isolated volume loss in the pons, and cortical thinning in specific frontal and parietal areas, namely rostral-middle-frontal and precuneus. One-year longitudinal follow-up demonstrated, in SCA2 patients, volume reduction in cerebellum, pons, superior cerebellar peduncles, and midbrain, and only in the cerebellum in preSCA2 subjects. No progression in clinical or cognitive measures was observed in preSCA2 subjects. The rate of volume loss in the cerebellum and subcortical regions greatly differed between patients and preSCA2. In conclusion, our pilot study demonstrated that MRI measures are highly sensitive to identify longitudinal structural changes in SCA2 patients, and in preSCA2 up to a decade before expected disease onset. These findings may contribute in the understanding of early neurodegenerative processes and may be useful in future therapeutical trials.

Genetic profile and clinical characteristics of Chinese patients with spinocerebellar ataxia type 2: A multicenter experience over 10years.

Spinocerebellar ataxia type 2 (SCA2) is the second most common type of spinocerebellar ataxia in China. However, data on the clinical and genetic features of Chinese SCA2 patients are scarce. This study aims to provide a comprehensive description of in the Chinese SCA2 cohort. A total of 135 patients with SCA2 from 92 families and 104 unrelated normal controls were recruited from three medical centers between 2008 and 2020. Sanger sequencing and TA cloning were used to determine the CAG repeat length and intrinsic structure. The clinical data of patients with SCA2, including electromyography, magnetic resonance imaging, positron-emission tomography, and clinical scale scores, were recorded. The mean±SD age at onset of SCA2 patients was 32.6±11.9years and the corresponding CAG repeat length was 42.1±3.6. CAG repeat length accounted for 64% of the age-at-onset variance. We observed that patients had a significantly lower proportion of (CAG)8 CAA(CAG)4 CAA(CAG)8 within normal alleles than normal controls (48.8% vs. 64.9%; p=0.003), while the distribution of the proportion of (CAG)13 CAA (CAG)8 was the opposite. Peripheral neuropathy was frequent, occurring in 75.9% of the patients. Parkinsonism was relatively common, with a frequency of 11.8%. Two patients with parkinsonism had a significantly more severe reduction in dopamine transporter levels in the bilateral striatum than the one patient with pure ataxia. An infant-onset case of SCA2 with more than 180 CAG repeats was characterized by global development delay, hypotonia and hearing impairment. This study describes the genetic profile and clinical characteristics of the largest SCA2 cohort to date in the Chinese population and analyzes inter-population differences. Many aspects of this study population were different from other populations with SCA2.

Expanded CAG Repeats in ATXN1, ATXN2, ATXN3, and HTT in the 1000 Genomes Project.

Spinocerebellar ataxia types 1, 2, 3 and Huntington disease are neurodegenerative disorders caused by expanded CAG repeats. We performed an in-silico analysis of CAG repeats in ATXN1, ATXN2, ATXN3, and HTT using 30× whole-=genome sequencing data of 2504 samples from the 1000 Genomes Project. Seven HTT-positive, 3 ATXN2-positive, 1 ATXN3-positive, and 6 possibly ATXN1-positive samples were identified. No correlation was found between the repeat sizes of the different genes. The distribution of CAG alleles varied by ethnicity. Our results suggest that there may be asymptomatic small expanded repeats in almost 0.5% of these populations. © 2020 International Parkinson and Movement Disorder Society.

Isolation and Identification of a Novel Anti-protein Aggregation Activity of Lignin-Carbohydrate Complex From Chionanthus retusus Leaves.

Lignin-carbohydrate complex (LCC) is the biological macromolecule that has been demonstrated to exert multiple biological functions, including antioxidant, anti-inflammation and anti-tumorigenesis, which support its broad application in the bioengineering field. However, it remains elusive the involvements of LCC in human neurological disorders, especially those with the overproduction of reactive oxygen species (ROS), such as spinocerebellar ataxias (SCAs). In this study, we found a previously undetermined anti-protein aggregation activity of LCC. Initially, two individual LCC preparations and carbohydrate-free lignin were isolated from the water-extracted waste residues of Chionanthus retusus (C. retusus) tender leaves. The chemical compositional analysis revealed that lignin (61.5%) is the predominant constituent in the lignin-rich LCC (LCC-L-CR), whereas the carbohydrate-rich LCC (LCC-C-CR) is mainly composed of carbohydrate (60.9%) with the xylan as the major constituent (42.1%). The NMR structural characterization showed that LCC-L-CR preparation is enriched in benzyl ether linkage, while phenyl glycoside is the predominant type of linkage in LCC-C-CR. Both LCC and lignin preparations showed antioxidant activities as exemplified by their abilities to scavenge free radicals in cultured mammalian cells and ROS in zebrafish. We further demonstrated a pronounced capability of LCC-L-CR in inhibiting the aggregation of expanded Ataxin-3, disease protein of SCA type 3, in human neuronal cells. Taken together, our study highlights the antioxidant and novel anti-protein aggregation activities of the C. retusus tender leaves-derived LCC.

Conversion of individuals at risk for spinocerebellar ataxia types 1, 2, 3, and 6 to manifest ataxia (RISCA): a longitudinal cohort study

Conversion of individuals at risk for spinocerebellar ataxia types 1, 2, 3, and 6 to manifest ataxia (RISCA): a longitudinal cohort study

A Brief Review on Spinocerebellar Ataxia and its Treatment

Ataxia is defined as a neurological sign including the lack of muscle movement coordination particularly of gait abnormality, talking changes, and also abnormality in eye actions. In ataxia, a part of nervous system is dysfunction which is also coordinate movement such as the cerebellum. In adults, ataxia can be acquired or genetic disorder. The Spinocerebellar ataxia is hereditary, progressive, degenerative, genetic disease or often fatel. There are no effective treatment and cure for Spinocerebellar ataxia (SCA). Spinocerebellar ataxia is a progressive disorders in which the cerebellum slowly degenerates. An average results estimated that 150,000 peoples in the United States have a diagnosis of Spinocerebellar ataxia (SCA) at any given time periods. Spinocerebellar ataxia (SCA) can affects anybody persons of at all ages. A current systemic review shows that the global prevalence of Spinocerebellar ataxia (SCA) is 3 in 100,000 people. However, a wide regional variation exists. SCA3 is common subtype around the world, SCA2 is additional prevalent in Cuba than SCA3 whilst SCA7 is the most frequent subtype in Venezuela due to strong founder’s effect. SCA6 is 1 of the most general ADCA in the North of England, with a global prevalence of 5.2/100,000.There are many different types of spinocerebellar ataxia (SCA) and each may have unique signs and symptoms. And these includes: Problems with coordination and balance (ataxia), Uncoordinated walk, poor hand eye coordination, Abnormal speech, Involuntary eye movement, Vision problems, Difficulty processing, Learning and remembering information. The hereditary ataxias are categorized by mode of inheritance and causative gene or chromosomal locus. The hereditary ataxias can be inherited in an autosomal dominant, autosomal recessive,or X-linked manner. Some types of SCA inherited in an autosomal dominant manner are caused by trinucleotide repeat expansions. A trinucleotide repeat is a segment of DNA that is repeated a number of times. It is normal for these repeats to exist and they typically do not cause any problems. Some Spinocerebellar ataxia SCAs remain unspecified and cannot be precisely diagnosed, but in the previous decades genetic testing has permissible precise identification of dozens of different SCAs and extra tests are being added each year. The spinocerebellar ataxia are classified SCA1 to SCA35for the treatment of SCA. There are no effective and cure treatment available for the spinocerebellar ataxia (SCA). But there are some methods; therapies and treatment are available which will be fruitful for the SCA. And these included the following: Meditation, Zolpidem, N-acetyl leucine, Rehabilitation

Preclinical Nanomedicines for Polyglutamine-Based Neurodegenerative Diseases.

Polyglutamine (polyQ) diseases, such as Huntington's disease and several types of spinocerebellar ataxias, are dominantly inherited progressive neurodegenerative disorders and characterized by the presence of expanded CAG trinucleotide repeats in the respective disease locus of the patient genomes. Patients with polyQ diseases currently need to rely on symptom-relieving treatments because disease-modifying therapeutic interventions remain scarce. Many disease-modifying therapeutic agents are now under clinical testing for treating polyQ diseases, but their delivery to the brain is often too invasive (e.g., intracranial injection) or inefficient, owing to in vivo degradation and clearance by physiological barriers (e.g., oral and intravenous administration). Nanoparticles provide a feasible solution for improving drug delivery to the brain, as evidenced by an increasing number of preclinical studies that document the efficacy of nanomedicines for polyQ diseases over the past 5-6 years. In this review, we present the pathogenic mechanisms of polyQ diseases, the common animal models of polyQ diseases for evaluating the efficacy of nanomedicines, and the common administration routes for delivering nanoparticles to the brain. Next, we summarize the recent preclinical applications of nanomedicines for treating polyQ diseases and improving neurological conditions in vivo, placing emphasis on antisense oligonucleotides, small peptide inhibitors, and small molecules as the disease-modifying agents. We conclude with our perspectives of the burgeoning field of "nanomedicines for polyQ diseases", including the use of inorganic nanoparticles and potential drugs as next-generation nanomedicines, development of higher-order animal models of polyQ diseases, and importance of "brain-nano" interactions.

Chimeric Peptide Species Contribute to Divergent Dipeptide Repeat Pathology in c9ALS/FTD and SCA36

GGGGCC hexanucleotide repeat expansions (HREs) in C9orf72 cause amyotrophic lateral sclerosis (ALS)and frontotemporal dementia (FTD) and lead to the production of aggregating dipeptide repeat proteins (DPRs) via repeat associated non-AUG (RAN) translation. Here, we show the similar intronic GGCCTG HREs that causes spinocerebellar ataxia type 36 (SCA36) is also translated into DPRs, including poly(GP) and poly(PR). We demonstrate that poly(GP) is more abundant in SCA36 compared to c9ALS/FTD patient tissue due to canonical AUG-mediated translation from intron-retained GGCCTG repeat RNAs. However, the frequency of the antisense RAN translation product poly(PR) is comparable between c9ALS/FTD and SCA36 patient samples. Interestingly, in SCA36 patient tissue, poly(GP) exists as a solublespecies, and no TDP-43 pathology is present. We show that aggregate-prone chimeric DPR (cDPR) species underlie the divergent DPR pathology between c9ALS/FTD and SCA36. These findings reveal key differences in translation, solubility, and protein aggregation of DPRs between c9ALS/FTD and SCA36.