RARE DISEASE
Spinocerebellar ataxia with axonal neuropathy type 1
Spinocerebellar ataxia with axonal neuropathy type 1
Spinocerebellar ataxia with axonal neuropathy type 1
Synonyms: SCAN1
Synonyms: SCAN1
Synonyms: SCAN1
Drug discovery
0
drugs
With orphan designations
Overview
Spinocerebellar ataxia with axonal neuropathy type 1 (SCAN1) is a rare autosomal recessive disorder caused by biallelic pathogenic variants in TDP1, encoding a DNA repair enzyme. It manifests in late childhood with progressive cerebellar ataxia, distal sensorimotor axonal neuropathy, gaze nystagmus, and cerebellar dysarthria. Neuropathy features include muscle atrophy, areflexia, and sensory loss. Cerebellar atrophy (vermis-predominant) is universal. Associated features include mild cognitive deficits, hypercholesterolemia, and seizures. Disease progression leads to wheelchair dependence, with no curative therapies available [1][2][4][16].
Burden
Progressive motor disability necessitates lifelong adaptive devices and eventual wheelchair dependence [4][9].
Cognitive deficits (executive dysfunction, mild intellectual disability) and peripheral neuropathy contribute to reduced quality of life [2][4].
High caregiver burden due to degenerative course and lack of disease-modifying treatments [4][10].
Therapies
Supportive care: Multidisciplinary management (neurology, rehabilitation, PT/OT, speech therapy) to address symptoms [4][16].
Avoidance: Genotoxic agents (camptothecins, bleomycin, radiation) due to defective DNA repair mechanisms [4][16].
Research: Preclinical studies focus on TDP1-targeted gene therapy and neuroprotective approaches, though none are yet clinically approved [6][7].
Categories: rare genetic diseases, rare neurological diseases
Research Papers
32 drug discovery papers about Spinocerebellar ataxia with axonal neuropathy type 1, with 1 first-in-class emerging drug candidates forecasted to outperform the average preclinical success rate. Recent publications:
32 drug discovery papers about Spinocerebellar ataxia with axonal neuropathy type 1, with 1 first-in-class emerging drug candidates forecasted to outperform the average preclinical success rate. Recent publications:
categories:
Small molecules
gene therapies
2022-09-05 | Cerebellar glutamatergic system impacts spontaneous motor recovery by regulating Gria1 expression
Peripheral nerve injury (PNI) often results in spontaneous motor recovery; however, how disrupted cerebellar circuitry affects PNI-associated motor recovery is unknown. Here, we demonstrated disrupted cerebellar circuitry and poor motor recovery in ataxia mice after PNI. This effect was mimicked by deep cerebellar nuclei (DCN) lesion, but not by damaging non-motor area hippocampus. By restoring cerebellar circuitry through DCN stimulation, and reversal of neurotransmitter imbalance using baclofen, ataxia mice achieve full motor recovery after PNI. Mechanistically, elevated glutamate-glutamine level was detected in DCN of ataxia mice by magnetic resonance spectroscopy. Transcriptomic study revealed that Gria1, an ionotropic glutamate receptor, was upregulated in DCN of control mice but failed to be upregulated in ataxia mice after sciatic nerve crush. AAV-mediated overexpression of Gria1 in DCN rescued motor deficits of ataxia mice after PNI. Finally, we found a correlative decrease in human GRIA1 mRNA expression in the cerebellum of patients with ataxia-telangiectasia and spinocerebellar ataxia type 6 patient iPSC-derived Purkinje cells, pointing to the clinical relevance of glutamatergic system. By conducting a large-scale analysis of 9,655,320 patients with ataxia, they failed to recover from carpal tunnel decompression surgery and tibial neuropathy, while aged-match non-ataxia patients fully recovered. Our results provide insight into cerebellar disorders and motor deficits after PNI.
2015-10-21 | Broad distribution of ataxin 1 silencing in rhesus cerebella for spinocerebellar ataxia type 1 therapy
Spinocerebellar ataxia type 1 is one of nine polyglutamine expansion diseases and is characterized by cerebellar ataxia and neuronal degeneration in the cerebellum and brainstem. Currently, there are no effective therapies for this disease. Previously, we have shown that RNA interference mediated silencing of ATXN1 mRNA provides therapeutic benefit in mouse models of the disease. Adeno-associated viral delivery of an engineered microRNA targeting ATXN1 to the cerebella of well-established mouse models improved motor phenotypes, neuropathy, and transcriptional changes. Here, we test the translatability of this approach in adult rhesus cerebella. Nine adult male and three adult female rhesus macaque were unilaterally injected with our therapeutic vector, a recombinant adeno-associated virus type 1 (rAAV1) expressing our RNAi trigger (miS1) and co-expressing enhanced green fluorescent protein (rAAV1.miS1eGFP) into the deep cerebellar nuclei using magnetic resonance imaging guided techniques combined with a Stealth Navigation system (Medtronics Inc.). Transduction was evident in the deep cerebellar nuclei, cerebellar Purkinje cells, the brainstem and the ventral lateral thalamus. Reduction of endogenous ATXN1 messenger RNA levels were ≥30% in the deep cerebellar nuclei, the cerebellar cortex, inferior olive, and thalamus relative to the uninjected hemisphere. There were no clinical complications, and quantitative and qualitative analyses suggest that this therapeutic intervention strategy and subsequent reduction of ATXN1 is well tolerated. Collectively the data illustrate the biodistribution and tolerability of rAAV1.miS1eGFP administration to the adult rhesus cerebellum and are supportive of clinical application for spinocerebellar ataxia type 1. Adeno-associated viral delivery of a microRNA targeting ATXN1 provides therapeutic benefit in mouse models of spinocerebellar ataxia type 1. Keiser et al. assess the translatability of this approach using adult rhesus macaques, and show that targeted delivery to deep cerebellar nuclei silences endogenous ATXN1 mRNA in multiple SCA1-affected sites.
2002-03-20 | Highly efficient and specific gene transfer to Purkinje cells in vivo using a herpes simplex virus I amplicon.
The transduction of cerebellar neurons in vivo with herpes simplex virus 1 (HSV-1) amplicon carrying the lacZ gene has been investigated after injection of the vector in the cerebellar cortex, ventricles, and inferior olive of adult rats. Injection into the cerebellar cortex resulted in transduction of Purkinje cells near the needle tract and injection into the ventricles yielded no transduced neurons. In contrast, high transduction efficiency was achieved by vector injection into the inferior olive, resulting in one of three positive Purkinje cells all over the ipsilateral and contralateral cerebellar hemispheres. Because neurons in the deep cerebellar nuclei are also transduced, we suggest that the vector is delivered from the inferior olive to the cerebellar nuclei and then to Purkinje cells by retrograde axonal transport. Expression of the lacZ gene within Purkinje cells was surprisingly persistent and was maintained at the same level for at least 40 days. Importantly, no signs of either toxicity or inflammation were observed in the cerebellum after vector injection, except for the borders of the needle tract where some reactive astrocytes were detected. Indeed, motor coordination of treated animals was entirely normal, as assessed by the rota-rod test. These results demonstrate that HSV-1 amplicon vectors can effect safe and stable transgene expression in Purkinje cells in vivo, raising the possibility of using these vectors for long-term gene therapy of human cerebellar disorders.
proteins
2026-03-20 | Tyrosyl-DNA Phosphodiesterase I Processing of Topoisomerase II-DNA Covalent Complexes is Dependent on Etoposide Stabilization and Tyrosyl-DNA Phosphodiesterase I N-terminal Domain.
Tyrosyl-DNA phosphodiesterase I (Tdp1) hydrolyzes 3'- and 5'-phosphodiester linked DNA-adducts, including Topoisomerase I- and II-DNA covalent complexes (Topo1cc and Topo2cc). Utilizing the model organism Saccharomyces cerevisiae, which only expresses Tdp1 and does not contain TDP2 orthologs or activity, we investigated the conditions under which Tdp1 processes Topo2(peptide)cc in cells and examined the role of the Tdp1 N-terminal domain in resolving Topo2(peptide)cc. We replaced the transcription activator PDR1 gene with the chimeric pdr1dbd-CYC8 transcription repressor in our strain, resulting in increased sensitivity to etoposide and doxorubicin but not to mitoxantrone. Using Tdp1 catalytic histidine mutants that induce substrate-dependent toxicity, we detected that Tdp1 selectively processes etoposide stabilized Topo2(peptide)cc. In contrast, Tdp1's processing of Topo1cc is drug independent. Moreover, we observed that the yeast SCAN1-like H432R mutant induces a more severe toxic phenotype when processing etoposide-Topo2(peptide)cc than Topo1cc with or without camptothecin. Extrapolating this observation to SCAN1 cerebellar neurons, we hypothesize that the contribution of Tdp1H493R processing of Topo2β(peptide)cc trapped by e.g., oxidative damaged nucleotides, is potentially more substantial towards cerebellar atrophy and compels further investigation. Nonetheless, the observed toxic phenotypes induced by Tdp1 mutants are recessive and suppressed by endogenous wild-type Tdp1 by lowering 5'Tdp1(mutant)cc. Moreover, Tdp1 cannot process etoposide-Topo2cc in cells without its N-terminal domain. This suggests that in cells Tdp1's N-terminal domain plays a critical role in regulating Tdp1 activity potentially by mediating recruitment to the DNA-adduct and/or facilitating accessibility to the phosphodiester linkage within a protein/peptide-DNA complex or stabilizing of the DNA strands related to damaged nucleotide-adducts.
2025-11-29 | H263A and SCAN1/H493R mutant TDP1 block TOP1-induced double-strand break repair during gene transcription in quiescent cells and promote cell death.
DNA single-strand break (SSB) repair defects lead to hereditary neurological syndromes. Spinocerebellar ataxia with axonal neuropathy type 1 (SCAN1), is caused by the homozygous H493R mutation in tyrosyl-DNA phosphodiesterase 1 (TDP1), an enzyme that initiates the repair of DNA topoisomerase 1 (TOP1)-induced SSBs by unlinking the TOP1 peptide from the break. Although TDP1 also initiates the repair of TOP1-induced DNA double-strand breaks (DSBs) associated with transcription, the role of TOP1-induced DSBs in SCAN1 pathology remains unclear. Here, we have addressed the impact of the SCAN1/H493R mutation on the repair of TOP1-induced DSBs. We demonstrate that while TDP1 loss delays the repair of these breaks, SCAN1/H493R completely blocks it in RPE-1 quiescent cells. This blockage is specific to DSBs and is accompanied by a prolonged trapping of mutated TDP1 on DNA, but not of TOP1 cleavage complexes (TOP1cc). Intriguingly, the H263A inactivating mutation of TDP1, which accumulates TOP1cc, also blocks TOP1-induced DSB repair. Importantly, both SCAN1/H493R and H263A mutations exhibit genome instability and cell death. Moreover, we demonstrate that tyrosyl-DNA phosphodiesterase 2 (TDP2) can compensate for TDP1 loss in RPE-1 quiescent cells. Collectively, our data support the potential role of TOP1-induced DSBs as a main contributor to certain hereditary neurological syndromes.
2018-03-09 | Reactive oxygen species stress increases accumulation of tyrosyl-DNA phsosphodiesterase 1 within mitochondria
Abstract Tyrosyl-DNA phosphodiesterase 1 (Tdp1) is a nuclear and mitochondrial protein that in nuclei and in vitro repairs blocked 3′ DNA termini such as 3′ phosphotyrosine conjugates resulting from stalling of topoisomerase I-DNA intermediates. Its mutation also causes spinocerebellar ataxia with axonal neuropathy type 1 (SCAN1). Because Tdp1 colocalizes with mitochondria following oxidative stress, we hypothesized that Tdp1 repairs mitochondrial DNA (mtDNA) and that mtDNA damage mediates entry of Tdp1 into the mitochondria. To test this, we used S . cerevisiae mutants, cultured mouse and human cells, and a Tdp1 knockout mouse. H 2 O 2 - and rotenone-induced cellular and intramitochondrial reactive oxygen species (ROS) activated oxidant-responsive kinases P38 and ERK1, and the translocation of Tdp1 from the nucleus to the mitochondria via the TIM/TOM complex. This translocation occurred independently of mtDNA. Within the mitochondria, Tdp1 interacted with Ligase III and reduced mtDNA mutations. Tdp1-deficient tissues had impaired mitochondrial respiration and decreased viability. These observations suggest that Tdp1 maintains mtDNA integrity and support the hypothesis that mitochondrial dysfunction contributes to the pathology of SCAN1.
2016-06-28 | Enforced DNA repair enzymes rescue neurons from apoptosis induced by target deprivation and axotomy in mouse models of neurodegeneration
It is unknown whether DNA damage accumulation is an upstream instigator or secondary effect of the cell death process in different populations of adult postmitotic neurons in the central nervous system. In two different mouse models of injury-induced neurodegeneration characterized by relatively synchronous accumulation of mitochondria, oxidative stress, and DNA damage prior to neuronal apoptosis, we enforced the expression of human 8-oxoguanine DNA glycosylase (hOGG1) and human apurinic-apyrimidinic endonuclease-1/Ref1 (hAPE) using recombinant adenoviruses (Ad). Thalamic lateral geniculate neurons and lumbar spinal cord motor neurons were transduced by Ad-hOGG1 and Ad-hAPE injections into the occipital cortex and skeletal muscle, respectively, prior to their target deprivation- and axotomy-induced retrograde apoptosis. Enforced expression of hOGG1 and hAPE in thalamus and spinal cord was confirmed by western blotting and immunohistochemistry. In injured populations of neurons in thalamus and spinal cord, a DNA damage response (DDR) was registered, as shown by localization of phospho-activated p53, Rad17, and replication protein A-32 immunoreactivities, and this DDR was attenuated more effectively by enforced hAPE expression than by hOGG1 expression. Enforced expression of hOGG1 and hAPE significantly protected thalamic neurons and motor neurons from retrograde apoptosis induced by target deprivation and axotomy. We conclude that a DDR response is engaged pre-apoptotically in different types of injured mature CNS neurons and that DNA repair enzymes can regulate the survival of retrogradely dying neurons, suggesting that DNA damage and activation of DDR are upstream mechanisms for this form of adult neurodegeneration in vivo, thus identifying DNA repair as a therapeutic target for neuroprotection.
2011-01-01 | [DNA repair and neurodegeneration: a common pathology shared by polyglutamine diseases].
Nuclear dysfunctions have been implicated in the pathology of polyglutamine diseases, while the details remain unclear. By employing various omics approaches, we have identified target molecules of mutant polyglutamine proteins in the nucleus. Proteome analysis of soluble nuclear proteins identified decreased HMGB1/2 in vulnerable neurons of Huntington's disease (HD) and spinocerebellar ataxia type 1 (SCA1). Interactome analysis unraveled Ku70 as a direct binding partner of mutant huntingtin. DNA damage repair is significantly impaired by interaction of mutant polyglutamine proteins with HMGB or Ku70, and the functional rescue of these molecules alleviated symptoms and pathologies of HD and SCA1. These results strongly suggest that impairment of DNA damage repair is a common pathology shared by multiple polyglutamine diseases.
small molecules
2024-07-24 | Dehydroabietylamine-based thiazolidin-4-ones and 2-thioxoimidazolidin-4-ones as novel tyrosyl-DNA phosphodiesterase 1 inhibitors.
Tyrosyl-DNA phosphodiesterase 1 (TDP1) is a DNA repair enzyme that plays a key role in repairing damage caused by various antitumor drugs. It is a promising target in medicinal chemistry for the creation of cancer adjuvant therapy. Inhibition of this enzyme together with the use of anticancer chemotherapy enhances the effect of the latter. The natural mutant of TDP1, TDP1(H493R), causes severe neurodegenerative disease spinocerebellar ataxia syndrome with axonal neuropathy (SCAN1). Inhibition of TDP1(H493R) appears to be useful in containment the progression of the disease. A library of compounds was synthesized starting from dehydroabietylamine including heterocyclic pharmacophore groups in the core. To obtain the desired products, the starting dehydroabietylamine was introduced sequentially in reaction with isothiocyanate and ethyl bromoacetate. Different classes of heterocyclic derivatives-2-iminothiazolidin-4-ons and 2-thioxoimidazolidin-4-ones-were obtained depending on the addition order of reagents. 2-Iminothiazolidin-4-thiones were obtained from 2-iminothiazolidin-4-ones under the action of the Lawesson's reagent. Effective TDP1 inhibitors were found among the obtained compounds that work in submicromolar concentrations. The inhibitor of TDP1(H493R) was also detected.
2023-07-05 | Ataxia-associated DNA repair genes protect the Drosophila mushroom body and locomotor function against glutamate signaling-associated damage
The precise control of motor movements is of fundamental importance to all behaviors in the animal kingdom. Efficient motor behavior depends on dedicated neuronal circuits – such as those in the cerebellum – that are controlled by extensive genetic programs. Autosomal recessive cerebellar ataxias (ARCAs) provide a valuable entry point into how interactions between genetic programs maintain cerebellar motor circuits. We previously identified a striking enrichment of DNA repair genes in ARCAs. How dysfunction of ARCA-associated DNA repair genes leads to preferential cerebellar dysfunction and impaired motor function is however unknown. The expression of ARCA DNA repair genes is not specific to the cerebellum. Only a limited number of animal models for DNA repair ARCAs exist, and, even for these, the interconnection between DNA repair defects, cerebellar circuit dysfunction, and motor behavior is barely established. We used Drosophila melanogaster to characterize the function of ARCA-associated DNA repair genes in the mushroom body (MB), a structure in the Drosophila central brain that shares structural features with the cerebellum. Here, we demonstrate that the MB is required for efficient startle-induced and spontaneous motor behaviors. Inhibition of synaptic transmission and loss-of-function of ARCA-associated DNA repair genes in the MB affected motor behavior in several assays. These motor deficits correlated with increased levels of MB DNA damage, MB Kenyon cell apoptosis and/or alterations in MB morphology. We further show that expression of genes involved in glutamate signaling pathways are highly, specifically, and persistently elevated in the postnatal human cerebellum. Manipulation of glutamate signaling in the MB induced motor defects, Kenyon cell DNA damage and apoptosis. Importantly, pharmacological reduction of glutamate signaling in the ARCA DNA repair models rescued the identified motor deficits, suggesting a role for aberrant glutamate signaling in ARCA-DNA repair disorders. In conclusion, our data highlight the importance of ARCA-associated DNA repair genes and glutamate signaling pathways to the cerebellum, the Drosophila MB and motor behavior. We propose that glutamate signaling may confer preferential cerebellar vulnerability in ARCA-associated DNA repair disorders. Targeting glutamate signaling could provide an exciting therapeutic entry point in this large group of so far untreatable disorders.
2023-06-01 | Parkinsonism in spinocerebellar ataxia with axonal neuropathy caused by adult-onset COA7 variants: a case report
Individuals with variants of cytochrome c oxidase assembly factor 7 (COA7), a mitochondrial functional-related gene, exhibit symptoms of spinocerebellar ataxia with axonal neuropathy before the age of 20. However, COA7 variants with parkinsonism or adult-onset type cases have not been described.We report the case of a patient who developed cerebellar symptoms and slowly progressive sensory and motor neuropathy in the extremities, similar to Charcot-Marie-Tooth disease, at age 30, followed by parkinsonism at age 58. Exome analysis revealed COA7 missense mutation in homozygotes (NM_023077.2:c.17A > G, NP_075565.2: p.Asp6Gly). Dopamine transporter single-photon emission computed tomography using a 123I-Ioflupane revealed clear hypo-accumulation in the bilateral striatum. However, 123I-metaiodobenzylguanidine myocardial scintigraphy showed normal sympathetic nerve function. Levodopa administration improved parkinsonism in this patient.COA7 gene variants may have caused parkinsonism in this case because mitochondrial function-related genes, such as parkin and PINK1, are known causative genes in some familial Parkinson's diseases.
2021-01-20 | Identification of novel inhibitors for the tyrosyl-DNA-phosphodiesterase 1 (Tdp1) mutant SCAN1 using virtual screening.
Spinocerebellar ataxia syndrome with axonal neuropathy (SCAN1) is a debilitating neurological disease that is caused by the mutation the Tyrosyl-DNA phosphodiesterase 1 (TDP1) DNA repair enzyme. The crucial His493 in TDP1's binding site is replaced with an arginine amino acid residue rendering the enzyme dysfunctional. A virtual screen was performed against the homology model of SCAN1 and seventeen compounds were identified and tested in a novel SCAN1 specific biochemical assay. Six compounds showed activity with IC50 values between 3.5 and 25.1 µM. The most active ligand 5 (3.5 µM) is a dicoumarin followed by a close structural analogue 6 at 6.0 µM. A less potent series of β-carbolines (14 and 15) was found with potency in the mid-teens. According to molecular modelling an excellent fit for the active ligands into the binding pocket is predicted. To the best of our knowledge, data on inhibitors of the mutant form of TDP1 has not been reported previously. The virtual hits were also tested for wild type TDP1 activity and all six SCAN1 inhibitors are potent for the former, e.g., ligand 5 has a measured IC50 at 99 nM. In the last decade, TDP1 is considered as a promising target for adjuvant therapy against cancer in combination with Topoisomerase 1 poisons. The active ligands are mostly non-toxic to cancer cell lines A-549, T98G and MCF-7 as well as the immortalized WI-38 human fetal lung cells. Furthermore, ligands 5 and 7, show promising synergy in conjunction with topotecan, a clinically used topoisomerase 1 anticancer drug. The active ligands 5, 7, 14 and 15 have a good balance of the physicochemical properties required for oral bioavailability making the excellent candidates for further development.
2020-05-04 | SCAN1-TDP1 trapping on mitochondrial DNA promotes mitochondrial dysfunction and mitophagy.
A homozygous mutation of human tyrosyl-DNA phosphodiesterase 1 (TDP1) causes the neurodegenerative syndrome, spinocerebellar ataxia with axonal neuropathy (SCAN1). TDP1 hydrolyzes the phosphodiester bond between DNA 3'-end and a tyrosyl moiety within trapped topoisomerase I (Top1)-DNA covalent complexes (Top1cc). TDP1 is critical for mitochondrial DNA (mtDNA) repair; however, the role of mitochondria remains largely unknown for the etiology of SCAN1. We demonstrate that mitochondria in cells expressing SCAN1-TDP1 (TDP1H493R) are selectively trapped on mtDNA in the regulatory non-coding region and promoter sequences. Trapped TDP1H493R-mtDNA complexes were markedly increased in the presence of the Top1 poison (mito-SN38) when targeted selectively into mitochondria in nanoparticles. TDP1H493R-trapping accumulates mtDNA damage and triggers Drp1-mediated mitochondrial fission, which blocks mitobiogenesis. TDP1H493R prompts PTEN-induced kinase 1-dependent mitophagy to eliminate dysfunctional mitochondria. SCAN1-TDP1 in mitochondria creates a pathological state that allows neurons to turn on mitophagy to rescue fit mitochondria as a mechanism of survival.
gene therapies
2022-09-05 | Cerebellar glutamatergic system impacts spontaneous motor recovery by regulating Gria1 expression
Peripheral nerve injury (PNI) often results in spontaneous motor recovery; however, how disrupted cerebellar circuitry affects PNI-associated motor recovery is unknown. Here, we demonstrated disrupted cerebellar circuitry and poor motor recovery in ataxia mice after PNI. This effect was mimicked by deep cerebellar nuclei (DCN) lesion, but not by damaging non-motor area hippocampus. By restoring cerebellar circuitry through DCN stimulation, and reversal of neurotransmitter imbalance using baclofen, ataxia mice achieve full motor recovery after PNI. Mechanistically, elevated glutamate-glutamine level was detected in DCN of ataxia mice by magnetic resonance spectroscopy. Transcriptomic study revealed that Gria1, an ionotropic glutamate receptor, was upregulated in DCN of control mice but failed to be upregulated in ataxia mice after sciatic nerve crush. AAV-mediated overexpression of Gria1 in DCN rescued motor deficits of ataxia mice after PNI. Finally, we found a correlative decrease in human GRIA1 mRNA expression in the cerebellum of patients with ataxia-telangiectasia and spinocerebellar ataxia type 6 patient iPSC-derived Purkinje cells, pointing to the clinical relevance of glutamatergic system. By conducting a large-scale analysis of 9,655,320 patients with ataxia, they failed to recover from carpal tunnel decompression surgery and tibial neuropathy, while aged-match non-ataxia patients fully recovered. Our results provide insight into cerebellar disorders and motor deficits after PNI.
2015-10-21 | Broad distribution of ataxin 1 silencing in rhesus cerebella for spinocerebellar ataxia type 1 therapy
Spinocerebellar ataxia type 1 is one of nine polyglutamine expansion diseases and is characterized by cerebellar ataxia and neuronal degeneration in the cerebellum and brainstem. Currently, there are no effective therapies for this disease. Previously, we have shown that RNA interference mediated silencing of ATXN1 mRNA provides therapeutic benefit in mouse models of the disease. Adeno-associated viral delivery of an engineered microRNA targeting ATXN1 to the cerebella of well-established mouse models improved motor phenotypes, neuropathy, and transcriptional changes. Here, we test the translatability of this approach in adult rhesus cerebella. Nine adult male and three adult female rhesus macaque were unilaterally injected with our therapeutic vector, a recombinant adeno-associated virus type 1 (rAAV1) expressing our RNAi trigger (miS1) and co-expressing enhanced green fluorescent protein (rAAV1.miS1eGFP) into the deep cerebellar nuclei using magnetic resonance imaging guided techniques combined with a Stealth Navigation system (Medtronics Inc.). Transduction was evident in the deep cerebellar nuclei, cerebellar Purkinje cells, the brainstem and the ventral lateral thalamus. Reduction of endogenous ATXN1 messenger RNA levels were ≥30% in the deep cerebellar nuclei, the cerebellar cortex, inferior olive, and thalamus relative to the uninjected hemisphere. There were no clinical complications, and quantitative and qualitative analyses suggest that this therapeutic intervention strategy and subsequent reduction of ATXN1 is well tolerated. Collectively the data illustrate the biodistribution and tolerability of rAAV1.miS1eGFP administration to the adult rhesus cerebellum and are supportive of clinical application for spinocerebellar ataxia type 1. Adeno-associated viral delivery of a microRNA targeting ATXN1 provides therapeutic benefit in mouse models of spinocerebellar ataxia type 1. Keiser et al. assess the translatability of this approach using adult rhesus macaques, and show that targeted delivery to deep cerebellar nuclei silences endogenous ATXN1 mRNA in multiple SCA1-affected sites.
2002-03-20 | Highly efficient and specific gene transfer to Purkinje cells in vivo using a herpes simplex virus I amplicon.
The transduction of cerebellar neurons in vivo with herpes simplex virus 1 (HSV-1) amplicon carrying the lacZ gene has been investigated after injection of the vector in the cerebellar cortex, ventricles, and inferior olive of adult rats. Injection into the cerebellar cortex resulted in transduction of Purkinje cells near the needle tract and injection into the ventricles yielded no transduced neurons. In contrast, high transduction efficiency was achieved by vector injection into the inferior olive, resulting in one of three positive Purkinje cells all over the ipsilateral and contralateral cerebellar hemispheres. Because neurons in the deep cerebellar nuclei are also transduced, we suggest that the vector is delivered from the inferior olive to the cerebellar nuclei and then to Purkinje cells by retrograde axonal transport. Expression of the lacZ gene within Purkinje cells was surprisingly persistent and was maintained at the same level for at least 40 days. Importantly, no signs of either toxicity or inflammation were observed in the cerebellum after vector injection, except for the borders of the needle tract where some reactive astrocytes were detected. Indeed, motor coordination of treated animals was entirely normal, as assessed by the rota-rod test. These results demonstrate that HSV-1 amplicon vectors can effect safe and stable transgene expression in Purkinje cells in vivo, raising the possibility of using these vectors for long-term gene therapy of human cerebellar disorders.
proteins
2026-03-20 | Tyrosyl-DNA Phosphodiesterase I Processing of Topoisomerase II-DNA Covalent Complexes is Dependent on Etoposide Stabilization and Tyrosyl-DNA Phosphodiesterase I N-terminal Domain.
Tyrosyl-DNA phosphodiesterase I (Tdp1) hydrolyzes 3'- and 5'-phosphodiester linked DNA-adducts, including Topoisomerase I- and II-DNA covalent complexes (Topo1cc and Topo2cc). Utilizing the model organism Saccharomyces cerevisiae, which only expresses Tdp1 and does not contain TDP2 orthologs or activity, we investigated the conditions under which Tdp1 processes Topo2(peptide)cc in cells and examined the role of the Tdp1 N-terminal domain in resolving Topo2(peptide)cc. We replaced the transcription activator PDR1 gene with the chimeric pdr1dbd-CYC8 transcription repressor in our strain, resulting in increased sensitivity to etoposide and doxorubicin but not to mitoxantrone. Using Tdp1 catalytic histidine mutants that induce substrate-dependent toxicity, we detected that Tdp1 selectively processes etoposide stabilized Topo2(peptide)cc. In contrast, Tdp1's processing of Topo1cc is drug independent. Moreover, we observed that the yeast SCAN1-like H432R mutant induces a more severe toxic phenotype when processing etoposide-Topo2(peptide)cc than Topo1cc with or without camptothecin. Extrapolating this observation to SCAN1 cerebellar neurons, we hypothesize that the contribution of Tdp1H493R processing of Topo2β(peptide)cc trapped by e.g., oxidative damaged nucleotides, is potentially more substantial towards cerebellar atrophy and compels further investigation. Nonetheless, the observed toxic phenotypes induced by Tdp1 mutants are recessive and suppressed by endogenous wild-type Tdp1 by lowering 5'Tdp1(mutant)cc. Moreover, Tdp1 cannot process etoposide-Topo2cc in cells without its N-terminal domain. This suggests that in cells Tdp1's N-terminal domain plays a critical role in regulating Tdp1 activity potentially by mediating recruitment to the DNA-adduct and/or facilitating accessibility to the phosphodiester linkage within a protein/peptide-DNA complex or stabilizing of the DNA strands related to damaged nucleotide-adducts.
2025-11-29 | H263A and SCAN1/H493R mutant TDP1 block TOP1-induced double-strand break repair during gene transcription in quiescent cells and promote cell death.
DNA single-strand break (SSB) repair defects lead to hereditary neurological syndromes. Spinocerebellar ataxia with axonal neuropathy type 1 (SCAN1), is caused by the homozygous H493R mutation in tyrosyl-DNA phosphodiesterase 1 (TDP1), an enzyme that initiates the repair of DNA topoisomerase 1 (TOP1)-induced SSBs by unlinking the TOP1 peptide from the break. Although TDP1 also initiates the repair of TOP1-induced DNA double-strand breaks (DSBs) associated with transcription, the role of TOP1-induced DSBs in SCAN1 pathology remains unclear. Here, we have addressed the impact of the SCAN1/H493R mutation on the repair of TOP1-induced DSBs. We demonstrate that while TDP1 loss delays the repair of these breaks, SCAN1/H493R completely blocks it in RPE-1 quiescent cells. This blockage is specific to DSBs and is accompanied by a prolonged trapping of mutated TDP1 on DNA, but not of TOP1 cleavage complexes (TOP1cc). Intriguingly, the H263A inactivating mutation of TDP1, which accumulates TOP1cc, also blocks TOP1-induced DSB repair. Importantly, both SCAN1/H493R and H263A mutations exhibit genome instability and cell death. Moreover, we demonstrate that tyrosyl-DNA phosphodiesterase 2 (TDP2) can compensate for TDP1 loss in RPE-1 quiescent cells. Collectively, our data support the potential role of TOP1-induced DSBs as a main contributor to certain hereditary neurological syndromes.
2018-03-09 | Reactive oxygen species stress increases accumulation of tyrosyl-DNA phsosphodiesterase 1 within mitochondria
Abstract Tyrosyl-DNA phosphodiesterase 1 (Tdp1) is a nuclear and mitochondrial protein that in nuclei and in vitro repairs blocked 3′ DNA termini such as 3′ phosphotyrosine conjugates resulting from stalling of topoisomerase I-DNA intermediates. Its mutation also causes spinocerebellar ataxia with axonal neuropathy type 1 (SCAN1). Because Tdp1 colocalizes with mitochondria following oxidative stress, we hypothesized that Tdp1 repairs mitochondrial DNA (mtDNA) and that mtDNA damage mediates entry of Tdp1 into the mitochondria. To test this, we used S . cerevisiae mutants, cultured mouse and human cells, and a Tdp1 knockout mouse. H 2 O 2 - and rotenone-induced cellular and intramitochondrial reactive oxygen species (ROS) activated oxidant-responsive kinases P38 and ERK1, and the translocation of Tdp1 from the nucleus to the mitochondria via the TIM/TOM complex. This translocation occurred independently of mtDNA. Within the mitochondria, Tdp1 interacted with Ligase III and reduced mtDNA mutations. Tdp1-deficient tissues had impaired mitochondrial respiration and decreased viability. These observations suggest that Tdp1 maintains mtDNA integrity and support the hypothesis that mitochondrial dysfunction contributes to the pathology of SCAN1.
2016-06-28 | Enforced DNA repair enzymes rescue neurons from apoptosis induced by target deprivation and axotomy in mouse models of neurodegeneration
It is unknown whether DNA damage accumulation is an upstream instigator or secondary effect of the cell death process in different populations of adult postmitotic neurons in the central nervous system. In two different mouse models of injury-induced neurodegeneration characterized by relatively synchronous accumulation of mitochondria, oxidative stress, and DNA damage prior to neuronal apoptosis, we enforced the expression of human 8-oxoguanine DNA glycosylase (hOGG1) and human apurinic-apyrimidinic endonuclease-1/Ref1 (hAPE) using recombinant adenoviruses (Ad). Thalamic lateral geniculate neurons and lumbar spinal cord motor neurons were transduced by Ad-hOGG1 and Ad-hAPE injections into the occipital cortex and skeletal muscle, respectively, prior to their target deprivation- and axotomy-induced retrograde apoptosis. Enforced expression of hOGG1 and hAPE in thalamus and spinal cord was confirmed by western blotting and immunohistochemistry. In injured populations of neurons in thalamus and spinal cord, a DNA damage response (DDR) was registered, as shown by localization of phospho-activated p53, Rad17, and replication protein A-32 immunoreactivities, and this DDR was attenuated more effectively by enforced hAPE expression than by hOGG1 expression. Enforced expression of hOGG1 and hAPE significantly protected thalamic neurons and motor neurons from retrograde apoptosis induced by target deprivation and axotomy. We conclude that a DDR response is engaged pre-apoptotically in different types of injured mature CNS neurons and that DNA repair enzymes can regulate the survival of retrogradely dying neurons, suggesting that DNA damage and activation of DDR are upstream mechanisms for this form of adult neurodegeneration in vivo, thus identifying DNA repair as a therapeutic target for neuroprotection.
2011-01-01 | [DNA repair and neurodegeneration: a common pathology shared by polyglutamine diseases].
Nuclear dysfunctions have been implicated in the pathology of polyglutamine diseases, while the details remain unclear. By employing various omics approaches, we have identified target molecules of mutant polyglutamine proteins in the nucleus. Proteome analysis of soluble nuclear proteins identified decreased HMGB1/2 in vulnerable neurons of Huntington's disease (HD) and spinocerebellar ataxia type 1 (SCA1). Interactome analysis unraveled Ku70 as a direct binding partner of mutant huntingtin. DNA damage repair is significantly impaired by interaction of mutant polyglutamine proteins with HMGB or Ku70, and the functional rescue of these molecules alleviated symptoms and pathologies of HD and SCA1. These results strongly suggest that impairment of DNA damage repair is a common pathology shared by multiple polyglutamine diseases.
small molecules
2024-07-24 | Dehydroabietylamine-based thiazolidin-4-ones and 2-thioxoimidazolidin-4-ones as novel tyrosyl-DNA phosphodiesterase 1 inhibitors.
Tyrosyl-DNA phosphodiesterase 1 (TDP1) is a DNA repair enzyme that plays a key role in repairing damage caused by various antitumor drugs. It is a promising target in medicinal chemistry for the creation of cancer adjuvant therapy. Inhibition of this enzyme together with the use of anticancer chemotherapy enhances the effect of the latter. The natural mutant of TDP1, TDP1(H493R), causes severe neurodegenerative disease spinocerebellar ataxia syndrome with axonal neuropathy (SCAN1). Inhibition of TDP1(H493R) appears to be useful in containment the progression of the disease. A library of compounds was synthesized starting from dehydroabietylamine including heterocyclic pharmacophore groups in the core. To obtain the desired products, the starting dehydroabietylamine was introduced sequentially in reaction with isothiocyanate and ethyl bromoacetate. Different classes of heterocyclic derivatives-2-iminothiazolidin-4-ons and 2-thioxoimidazolidin-4-ones-were obtained depending on the addition order of reagents. 2-Iminothiazolidin-4-thiones were obtained from 2-iminothiazolidin-4-ones under the action of the Lawesson's reagent. Effective TDP1 inhibitors were found among the obtained compounds that work in submicromolar concentrations. The inhibitor of TDP1(H493R) was also detected.
2023-07-05 | Ataxia-associated DNA repair genes protect the Drosophila mushroom body and locomotor function against glutamate signaling-associated damage
The precise control of motor movements is of fundamental importance to all behaviors in the animal kingdom. Efficient motor behavior depends on dedicated neuronal circuits – such as those in the cerebellum – that are controlled by extensive genetic programs. Autosomal recessive cerebellar ataxias (ARCAs) provide a valuable entry point into how interactions between genetic programs maintain cerebellar motor circuits. We previously identified a striking enrichment of DNA repair genes in ARCAs. How dysfunction of ARCA-associated DNA repair genes leads to preferential cerebellar dysfunction and impaired motor function is however unknown. The expression of ARCA DNA repair genes is not specific to the cerebellum. Only a limited number of animal models for DNA repair ARCAs exist, and, even for these, the interconnection between DNA repair defects, cerebellar circuit dysfunction, and motor behavior is barely established. We used Drosophila melanogaster to characterize the function of ARCA-associated DNA repair genes in the mushroom body (MB), a structure in the Drosophila central brain that shares structural features with the cerebellum. Here, we demonstrate that the MB is required for efficient startle-induced and spontaneous motor behaviors. Inhibition of synaptic transmission and loss-of-function of ARCA-associated DNA repair genes in the MB affected motor behavior in several assays. These motor deficits correlated with increased levels of MB DNA damage, MB Kenyon cell apoptosis and/or alterations in MB morphology. We further show that expression of genes involved in glutamate signaling pathways are highly, specifically, and persistently elevated in the postnatal human cerebellum. Manipulation of glutamate signaling in the MB induced motor defects, Kenyon cell DNA damage and apoptosis. Importantly, pharmacological reduction of glutamate signaling in the ARCA DNA repair models rescued the identified motor deficits, suggesting a role for aberrant glutamate signaling in ARCA-DNA repair disorders. In conclusion, our data highlight the importance of ARCA-associated DNA repair genes and glutamate signaling pathways to the cerebellum, the Drosophila MB and motor behavior. We propose that glutamate signaling may confer preferential cerebellar vulnerability in ARCA-associated DNA repair disorders. Targeting glutamate signaling could provide an exciting therapeutic entry point in this large group of so far untreatable disorders.
2023-06-01 | Parkinsonism in spinocerebellar ataxia with axonal neuropathy caused by adult-onset COA7 variants: a case report
Individuals with variants of cytochrome c oxidase assembly factor 7 (COA7), a mitochondrial functional-related gene, exhibit symptoms of spinocerebellar ataxia with axonal neuropathy before the age of 20. However, COA7 variants with parkinsonism or adult-onset type cases have not been described.We report the case of a patient who developed cerebellar symptoms and slowly progressive sensory and motor neuropathy in the extremities, similar to Charcot-Marie-Tooth disease, at age 30, followed by parkinsonism at age 58. Exome analysis revealed COA7 missense mutation in homozygotes (NM_023077.2:c.17A > G, NP_075565.2: p.Asp6Gly). Dopamine transporter single-photon emission computed tomography using a 123I-Ioflupane revealed clear hypo-accumulation in the bilateral striatum. However, 123I-metaiodobenzylguanidine myocardial scintigraphy showed normal sympathetic nerve function. Levodopa administration improved parkinsonism in this patient.COA7 gene variants may have caused parkinsonism in this case because mitochondrial function-related genes, such as parkin and PINK1, are known causative genes in some familial Parkinson's diseases.
2021-01-20 | Identification of novel inhibitors for the tyrosyl-DNA-phosphodiesterase 1 (Tdp1) mutant SCAN1 using virtual screening.
Spinocerebellar ataxia syndrome with axonal neuropathy (SCAN1) is a debilitating neurological disease that is caused by the mutation the Tyrosyl-DNA phosphodiesterase 1 (TDP1) DNA repair enzyme. The crucial His493 in TDP1's binding site is replaced with an arginine amino acid residue rendering the enzyme dysfunctional. A virtual screen was performed against the homology model of SCAN1 and seventeen compounds were identified and tested in a novel SCAN1 specific biochemical assay. Six compounds showed activity with IC50 values between 3.5 and 25.1 µM. The most active ligand 5 (3.5 µM) is a dicoumarin followed by a close structural analogue 6 at 6.0 µM. A less potent series of β-carbolines (14 and 15) was found with potency in the mid-teens. According to molecular modelling an excellent fit for the active ligands into the binding pocket is predicted. To the best of our knowledge, data on inhibitors of the mutant form of TDP1 has not been reported previously. The virtual hits were also tested for wild type TDP1 activity and all six SCAN1 inhibitors are potent for the former, e.g., ligand 5 has a measured IC50 at 99 nM. In the last decade, TDP1 is considered as a promising target for adjuvant therapy against cancer in combination with Topoisomerase 1 poisons. The active ligands are mostly non-toxic to cancer cell lines A-549, T98G and MCF-7 as well as the immortalized WI-38 human fetal lung cells. Furthermore, ligands 5 and 7, show promising synergy in conjunction with topotecan, a clinically used topoisomerase 1 anticancer drug. The active ligands 5, 7, 14 and 15 have a good balance of the physicochemical properties required for oral bioavailability making the excellent candidates for further development.
2020-05-04 | SCAN1-TDP1 trapping on mitochondrial DNA promotes mitochondrial dysfunction and mitophagy.
A homozygous mutation of human tyrosyl-DNA phosphodiesterase 1 (TDP1) causes the neurodegenerative syndrome, spinocerebellar ataxia with axonal neuropathy (SCAN1). TDP1 hydrolyzes the phosphodiester bond between DNA 3'-end and a tyrosyl moiety within trapped topoisomerase I (Top1)-DNA covalent complexes (Top1cc). TDP1 is critical for mitochondrial DNA (mtDNA) repair; however, the role of mitochondria remains largely unknown for the etiology of SCAN1. We demonstrate that mitochondria in cells expressing SCAN1-TDP1 (TDP1H493R) are selectively trapped on mtDNA in the regulatory non-coding region and promoter sequences. Trapped TDP1H493R-mtDNA complexes were markedly increased in the presence of the Top1 poison (mito-SN38) when targeted selectively into mitochondria in nanoparticles. TDP1H493R-trapping accumulates mtDNA damage and triggers Drp1-mediated mitochondrial fission, which blocks mitobiogenesis. TDP1H493R prompts PTEN-induced kinase 1-dependent mitophagy to eliminate dysfunctional mitochondria. SCAN1-TDP1 in mitochondria creates a pathological state that allows neurons to turn on mitophagy to rescue fit mitochondria as a mechanism of survival.
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