gene therapy

https://www.nature.com/articles/s10038-022-01031-2

In this article, we review the epidemiology, genetic diagnosis, and clinicogenetic characteristics of CMT in Japan. In addition, we discuss the newly identified novel causative genes for CMT/IPNs in Japan, namely MME and COA7. Identification of the new causes of CMT will facilitate in-depth characterization of the underlying molecular mechanisms of CMT, leading to the establishment of therapeutic approaches such as drug development and gene therapy.

https://academic.oup.com/brain/advance-article-abstract/doi/10.1093/brain/awaa311/5989972?redirectedFrom=fulltext

https://www.ncbi.nlm.nih.gov/pubmed/33210134?dopt=Abstract

The expanding genetic landscape of hereditary motor neuropathies.

Related Articles

The expanding genetic landscape of hereditary motor neuropathies.

Brain. 2020 Nov 19;:

Authors: Beijer D, Baets J

Abstract

Hereditary motor neuropathies are clinically and genetically diverse disorders characterized by length-dependent axonal degeneration of lower motor neurons. Although currently as many as 26 causal genes are known, there is considerable missing heritability compared to other inherited neuropathies such as Charcot-Marie-Tooth disease. Intriguingly, this genetic landscape spans a discrete number of key biological processes within the peripheral nerve. Also, in terms of underlying pathophysiology, hereditary motor neuropathies show striking overlap with several other neuromuscular and neurological disorders. In this review, we provide a current overview of the genetic spectrum of hereditary motor neuropathies highlighting recent reports of novel genes and mutations or recent discoveries in the underlying disease mechanisms. In addition, we link hereditary motor neuropathies with various related disorders by addressing the main affected pathways of disease divided into five major processes: axonal transport, tRNA aminoacylation, RNA metabolism and DNA integrity, ion channels and transporters and endoplasmic reticulum.

PMID: 33210134 [PubMed – as supplied by publisher]

PubMed:33210134

Beijer D, Baets J

https://www.hindawi.com/journals/bmri/2020/1353516/

https://www.ncbi.nlm.nih.gov/pubmed/33029488?dopt=Abstract

Identification of Candidate Genes Associated with Charcot-Marie-Tooth Disease by Network and Pathway Analysis.

Identification of Candidate Genes Associated with Charcot-Marie-Tooth Disease by Network and Pathway Analysis.

Biomed Res Int. 2020;2020:1353516

Authors: Zhong M, Luo Q, Ye T, Zhu X, Chen X, Liu J

Abstract

Charcot-Marie-Tooth Disease (CMT) is the most common clinical genetic disease of the peripheral nervous system. Although many studies have focused on elucidating the pathogenesis of CMT, few focuses on achieving a systematic analysis of biology to decode the underlying pathological molecular mechanisms and the mechanism of its disease remains to be elucidated. So our study may provide further useful insights into the molecular mechanisms of CMT based on a systematic bioinformatics analysis. In the current study, by reviewing the literatures deposited in PUBMED, we identified 100 genes genetically related to CMT. Then, the functional features of the CMT-related genes were examined by R software and KOBAS, and the selected biological process crosstalk was visualized with the software Cytoscape. Moreover, CMT specific molecular network analysis was conducted by the Molecular Complex Detection (MCODE) Algorithm. The biological function enrichment analysis suggested that myelin sheath, axon, peripheral nervous system, mitochondrial function, various metabolic processes, and autophagy played important roles in CMT development. Aminoacyl-tRNA biosynthesis, metabolic pathways, and vasopressin-regulated water reabsorption were significantly enriched in the Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway network, suggesting that these pathways may play key roles in CMT occurrence and development. According to the crosstalk, the biological processes could be roughly divided into a correlative module and two separate modules. MCODE clusters showed that in top 3 clusters, 13 of CMT-related genes were included in the network and 30 candidate genes were discovered which might be potentially related to CMT. The study may help to update the new understanding of the pathogenesis of CMT and expand the potential genes of CMT for further exploration.

PMID: 33029488 [PubMed – in process]

PubMed:33029488

Zhong M, Luo Q, Ye T, Zhu X, Chen X, Liu J

https://link.springer.com/article/10.1007/s00415-020-10171-4

https://www.ncbi.nlm.nih.gov/pubmed/32897397?dopt=Abstract

Deep geno- and phenotyping in two consanguineous families with CMT2 reveals HADHA as an unusual disease-causing gene and an intronic variant in GDAP1 as an unusual mutation.

Related Articles

Deep geno- and phenotyping in two consanguineous families with CMT2 reveals HADHA as an unusual disease-causing gene and an intronic variant in GDAP1 as an unusual mutation.

J Neurol. 2020 Sep 08;:

Authors: Khani M, Taheri H, Shamshiri H, Moazzeni H, Hardy J, Bras JT, InanlooRahatloo K, Alavi A, Nafissi S, Elahi E

Abstract

BACKGROUND: Charcot-Marie-Tooth (CMT) disease is a prevalent and heterogeneous peripheral neuropathy. Most patients affected with the axonal form of CMT (CMT2) do not harbor mutations in the approximately 90 known CMT-associated genes. We aimed to identify causative genes in two CMT2 pedigrees.

METHODS: Neurologic examination, laboratory tests and brain MRIs were performed. Genetic analysis included exome sequencing of four patients from the two pedigrees. The predicted effect of a deep intronic mutation on splicing was tested by regular and real-time PCR and sequencing.

RESULTS: Clinical data were consistent with CMT2 diagnosis. Inheritance patterns were autosomal recessive. Exome data of CMT2-101 did not include mutations in known CMT-associated genes. Sequence data, segregation analysis, bioinformatics analysis, evolutionary conservation, and information in the literature strongly implicated HADHA as the causative gene. An intronic variation positioned 23 nucleotides away from following intron/exon border in GDAP1 was ultimately identified as cause of CMT in CMT2-102. It was shown to affect splicing.

CONCLUSION: The finding of a HADHA mutation as a cause of CMT is of interest because its encoded protein is a subunit of the mitochondrial trifunctional protein (MTP) complex, a mitochondrial enzyme involved in long chain fatty acid oxidation. Long chain fatty acid oxidation is an important source of energy for skeletal muscles. The mutation found in CMT2-102 is only the second intronic mutation reported in GDAP1. The mutation in the CMT2-102 pedigree was outside the canonical splice site sequences, emphasizing the importance of careful examination of available intronic sequences in exome sequence data.

PMID: 32897397 [PubMed – as supplied by publisher]

PubMed:32897397

Khani M, Taheri H, Shamshiri H, Moazzeni H, Hardy J, Bras JT, InanlooRahatloo K, Alavi A, Nafissi S, Elahi E

https://onlinelibrary.wiley.com/doi/abs/10.1111/jns.12377

https://www.ncbi.nlm.nih.gov/pubmed/32319184?dopt=Abstract

Genetic spectrum of MCM3AP and its relationship with phenotype of Charcot-Marie-Tooth disease.

Genetic spectrum of MCM3AP and its relationship with phenotype of Charcot-Marie-Tooth disease.

J Peripher Nerv Syst. 2020 Apr 21;:

Authors: Dong HL, Wei Q, Li JQ, Li HF, Bai G, Ma H, Wu ZY

Abstract

BACKGROUND AND AIMS: Mutations in MCM3AP have recently been reported to cause autosomal recessive Charcot-Marie-Tooth disease (CMT). However, only 9 CMT families with MCM3AP mutations have been reported and genotype-phenotype correlation remains unclear. This study aimed to investigate the genetic spectrum of MCM3AP and its relationship with phenotype of CMT.

METHODS: Whole exome sequencing (WES) was performed in the family and variants were validated by Sanger sequencing. Reverse transcription-PCR (RT-PCR) were performed in splicing analysis.

RESULTS: We reported a novel splicing variant (c.5634-1G > T) and a known missense variant (c.2633G > A, p.Arg878His). Functional studies showed that c.5634-1G > T led to splicing defect and aberrant transcript eliminated by nonsense-mediated mRNA decay. The symptom of the patient was less severe and slowly progressed with axonal peripheral neuropathy compared to the reported CMT patients. Genotype-phenotype correlation analysis indicated that affected individuals with null mutations presented with delayed independent walking. The percentage of intellectual disability and loss of ambulation in the null group tended to be greater, although this failed to reach statistical significance.

INTERPRETATION: Our findings expand the genetic spectrum of MCM3AP and suggest that genotype-phenotype correlation would help genetic counseling of MCM3AP in CMT patients. This article is protected by copyright. All rights reserved.

PMID: 32319184 [PubMed – as supplied by publisher]

PubMed:32319184

Dong HL, Wei Q, Li JQ, Li HF, Bai G, Ma H, Wu ZY

https://www.mdpi.com/2073-4409/9/4/1028

https://www.ncbi.nlm.nih.gov/pubmed/32326241?dopt=Abstract

Charcot-Marie-Tooth Type 2B: A New Phenotype Associated with a Novel RAB7A Mutation and Inhibited EGFR Degradation.

Charcot-Marie-Tooth Type 2B: A New Phenotype Associated with a Novel RAB7A Mutation and Inhibited EGFR Degradation.

Cells. 2020 Apr 21;9(4):

Authors: Saveri P, De Luca M, Nisi V, Pisciotta C, Romano R, Piscosquito G, Reilly MM, Polke JM, Cavallaro T, Fabrizi GM, Fossa P, Cichero E, Lombardi R, Lauria G, Magri S, Taroni F, Pareyson D, Bucci C

Abstract

The rare autosomal dominant Charcot-Marie-Tooth type 2B (CMT2B) is associated with mutations in the RAB7A gene, involved in the late endocytic pathway. CMT2B is characterized by predominant sensory loss, ulceromutilating features, with lesser-to-absent motor deficits. We characterized clinically and genetically a family harboring a novel pathogenic RAB7A variant and performed structural and functional analysis of the mutant protein. A 39-year-old woman presented with early-onset walking difficulties, progressive distal muscle wasting and weakness in lower limbs and only mild sensory signs. Electrophysiology demonstrated an axonal sensorimotor neuropathy. Nerve biopsy showed a chronic axonal neuropathy with moderate loss of all caliber myelinated fibers. Next-generation sequencing (NGS) technology revealed in the proband and in her similarly affected father the novel c.377A>G (p.K126R) heterozygous variant predicted to be deleterious. The mutation affects the biochemical properties of RAB7 GTPase, causes altered interaction with peripherin, and inhibition of neurite outgrowth, as for previously reported CMT2B mutants. However, it also shows differences, particularly in the epidermal growth factor receptor degradation process. Altogether, our findings indicate that this RAB7A variant is pathogenic and widens the phenotypic spectrum of CMT2B to include predominantly motor CMT2. Alteration of the receptor degradation process might explain the different clinical presentations in this family.

PMID: 32326241 [PubMed – in process]

PubMed:32326241

Saveri P, De Luca M, Nisi V, Pisciotta C, Romano R, Piscosquito G, Reilly MM, Polke JM, Cavallaro T, Fabrizi GM, Fossa P, Cichero E, Lombardi R, Lauria G, Magri S, Taroni F, Pareyson D, Bucci C

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7164973/

https://www.ncbi.nlm.nih.gov/pubmed/32337334?dopt=Abstract

Novel EGR2 variant that associates with Charcot-Marie-Tooth disease when combined with lipopolysaccharide-induced TNF-α factor T49M polymorphism.

Related Articles

Novel EGR2 variant that associates with Charcot-Marie-Tooth disease when combined with lipopolysaccharide-induced TNF-α factor T49M polymorphism.

Neurol Genet. 2020 Apr;6(2):e407

Authors: Blanco-Cantó ME, Patel N, Velasco-Aviles S, Casillas-Bajo A, Salas-Felipe J, García-Escrivá A, Díaz-Marín C, Cabedo H

Abstract

Objective: To identify novel genetic mechanisms causing Charcot-Marie-Tooth (CMT) disease.

Methods: We performed a next-generation sequencing study of 34 genes associated with CMT in a patient with peripheral neuropathy.

Results: We found a non-previously described mutation in EGR2 (p.P397H). P397H mutation is located within the loop that connects zinc fingers 2 and 3, a pivotal domain for the activity of this transcription factor. Using promoter activity luciferase assays, we found that this mutation promotes decreased transcriptional activity of EGR2. In this patient, we also found a previously described nonpathogenic polymorphism in lipopolysaccharide-induced TNF-α factor (LITAF) (p.T49M). We show that the p.T49M mutation decreases the steady-state levels of the LITAF protein in Schwann cells. Loss of function of LITAF has been shown to produce deregulation in the NRG1-erbB signaling, a pivotal pathway for EGR2 expression by Schwann cells. Surprisingly, our segregation study demonstrates that p.P397H mutation in EGR2 is not sufficient to produce CMT disease. Most notably, only those patients expressing simultaneously the LITAF T49M polymorphism develop peripheral neuropathy.

Conclusions: Our data support that the LITAF loss-of-function interferes with the expression of the transcriptional-deficient EGR2 P397H mutant hampering Schwann cell differentiation and suggest that in vivo both genes act in tandem to allow the proper development of myelin.

PMID: 32337334 [PubMed]

PubMed:32337334

Blanco-Cantó ME, Patel N, Velasco-Aviles S, Casillas-Bajo A, Salas-Felipe J, García-Escrivá A, Díaz-Marín C, Cabedo H

https://www.sciencedirect.com/science/article/abs/pii/S0006899320300391?via%3Dihub

https://www.ncbi.nlm.nih.gov/pubmed/32001243?dopt=Abstract

Gene Therapies for Axonal Neuropathies: Available Strategies, Successes to Date, and What to Target Next.

Related Articles

Gene Therapies for Axonal Neuropathies: Available Strategies, Successes to Date, and What to Target Next.

Brain Res. 2020 Jan 27;:146683

Authors: Morelli KH, Hatton CL, Harper SQ, Burgess RW

Abstract

Nearly one-hundred loci in the human genome have been associated with different forms of Charcot-Marie-Tooth disease (CMT) and related inherited neuropathies. Despite this wealth of gene targets, treatment options are still extremely limited, and clear “druggable” pathways are not obvious for many of these mutations. However, recent advances in gene therapies are beginning to circumvent this challenge. Each type of CMT is a monogenic disorder, and the cellular targets are usually well-defined and typically include peripheral neurons or Schwann cells. In addition, the genetic mechanism is often also clear, with loss-of-function mutations requiring restoration of gene expression, and gain-of-function or dominant-negative mutations requiring silencing of the mutant allele. These factors combine to make CMT a good target for developing genetic therapies. Here we will review the state of relatively established gene therapy approaches, including viral vector-mediated gene replacement and antisense oligonucleotides for exon skipping, altering splicing, and gene knockdown. We will also describe earlier stage approaches for allele-specific knockdown and CRIPSR/Cas9 gene editing. We will next describe how these various approaches have been deployed in clinical and preclinical studies. Finally, we will evaluate various forms of CMT as candidates for gene therapy based on the current understanding of their genetics, cellular/tissue targets, validated animal models, and availability of patient populations and natural history data.

PMID: 32001243 [PubMed – as supplied by publisher]

PubMed:32001243

Morelli KH, Hatton CL, Harper SQ, Burgess RW

https://www.nature.com/articles/s10038-019-0710-5

https://www.ncbi.nlm.nih.gov/pubmed/31852984?dopt=Abstract

Identification of novel pathogenic copy number variations in Charcot-Marie-Tooth disease.

Related Articles

Identification of novel pathogenic copy number variations in Charcot-Marie-Tooth disease.

J Hum Genet. 2019 Dec 18;:

Authors: Mortreux J, Bacquet J, Boyer A, Alazard E, Bellance R, Giguet-Valard AG, Cerino M, Krahn M, Audic F, Chabrol B, Laugel V, Desvignes JP, Béroud C, Nguyen K, Verschueren A, Lévy N, Attarian S, Delague V, Missirian C, Bonello-Palot N

Abstract

Charcot-Marie-Tooth disease (CMT) is a hereditary sensory-motor neuropathy characterized by a strong clinical and genetic heterogeneity. Over the past few years, with the occurrence of whole-exome sequencing (WES) or whole-genome sequencing (WGS), the molecular diagnosis rate has been improved by allowing the screening of more than 80 genes at one time. In CMT, except the recurrent PMP22 duplication accounting for about 60% of pathogenic variations, pathogenic copy number variations (CNVs) are rarely reported and only a few studies screening specifically CNVs have been performed. The aim of the present study was to screen for CNVs in the most prevalent genes associated with CMT in a cohort of 200 patients negative for the PMP22 duplication. CNVs were screened using the Exome Depth software on next generation sequencing (NGS) data obtained by targeted capture and sequencing of a panel of 81 CMT associated genes. Deleterious CNVs were identified in four patients (2%), in four genes: GDAP1, LRSAM1, GAN, and FGD4. All CNVs were confirmed by high-resolution oligonucleotide array Comparative Genomic Hybridization (aCGH) and/or quantitative PCR. By identifying four new CNVs in four different genes, we demonstrate that, although they are rare mutational events in CMT, CNVs might contribute significantly to mutational spectrum of Charcot-Marie-Tooth disease and should be searched in routine NGS diagnosis. This strategy increases the molecular diagnosis rate of patients with neuropathy.

PMID: 31852984 [PubMed – as supplied by publisher]

PubMed:31852984

Mortreux J, Bacquet J, Boyer A, Alazard E, Bellance R, Giguet-Valard AG, Cerino M, Krahn M, Audic F, Chabrol B, Laugel V, Desvignes JP, Béroud C, Nguyen K, Verschueren A, Lévy N, Attarian S, Delague V, Missirian C, Bonello-Palot N

https://www.ncbi.nlm.nih.gov/pubmed/31790684?dopt=Abstract

https://www.sciencedirect.com/science/article/abs/pii/S0006899319306262?via%3Dihub

Gene therapy approaches targeting Schwann cells for demyelinating neuropathies.

Related Articles

Gene therapy approaches targeting Schwann cells for demyelinating neuropathies.

Brain Res. 2019 Nov 29;:146572

Authors: Sargiannidou I, Kagiava A, Kleopa KA

Abstract

Charcot-Marie-Tooth disease (CMT) encompasses numerous genetically heterogeneous inherited neuropathies, which together are one of the commonest neurogenetic disorders. Axonal CMT types result from mutations in neuronally expressed genes, whereas demyelinating CMT forms mostly result from mutations in genes expressed by myelinating Schwann cells. The demyelinating forms are the most common, and may be caused by dominant mutations and gene dosage effects (as in CMT1), as well as by recessive mutations and loss of function mechanisms (as in CMT4). The discovery of causative genes and increasing insights into molecular mechanisms through the study of experimental disease models has provided the basis for the development of gene therapy approaches. For demyelinating CMT, gene silencing or gene replacement strategies need to be targeted to Schwann cells. Progress in gene replacement for two different CMT forms, including CMT1X caused by GJB1 gene mutations, and CMT4C, caused by SH3TC2 gene mutations, has been made through the use of a myelin-specific promoter to restrict expression in Schwann cells, and by lumbar intrathecal delivery of lentiviral viral vectors to achieve more widespread biodistribution in the peripheral nervous system. This review summarizes the molecular-genetic mechanisms of selected demyelinating CMT neuropathies and the progress made so far, as well as the remaining challenges in the path towards a gene therapy to treat these disorders through the use of optimal gene therapy tools such as using clinically translatable delivery methods and adeno-associated viral (AAV) vectors.

PMID: 31790684 [PubMed – as supplied by publisher]

PubMed:31790684

Sargiannidou I, Kagiava A, Kleopa KA

https://www.sciencedirect.com/science/article/abs/pii/S0006899319305864?via%3Dihub

https://www.ncbi.nlm.nih.gov/pubmed/31678418?dopt=Abstract

Overlapping spectrums: the clinicogenetic commonalities between Charcot-Marie-Tooth and other neurodegenerative diseases.

Related Articles

Overlapping spectrums: the clinicogenetic commonalities between Charcot-Marie-Tooth and other neurodegenerative diseases.

Brain Res. 2019 Oct 31;:146532

Authors: Martin PB, Hicks AN, Holbrook SE, Cox GA

Abstract

Charcot-Marie-Tooth (CMT) disease is a progressive and heterogeneous inherited peripheral neuropathy. A myriad of genetic factors have been identified that contribute to the degeneration of motor and sensory axons in a length-dependent manner. Emerging biological themes underlying disease include defects in axonal trafficking, dysfunction in RNA metabolism and protein homeostasis, as well deficits in the cellular stress response. Moreover, genetic contributions to CMT can have overlap with other neuropathies, motor neuron diseases (MNDs) and neurodegenerative disorders. Recent progress in understanding the molecular biology of CMT and overlapping syndromes aids in the search for necessary therapeutic targets.

PMID: 31678418 [PubMed – as supplied by publisher]

PubMed:31678418

Martin PB, Hicks AN, Holbrook SE, Cox GA

https://www.sciencedirect.com/science/article/abs/pii/S0006899319305876?via%3Dihub

https://www.ncbi.nlm.nih.gov/pubmed/31669284?dopt=Abstract

Gene therapy to promote regeneration in Charcot-Marie-Tooth disease.

Related Articles

Gene therapy to promote regeneration in Charcot-Marie-Tooth disease.

Brain Res. 2019 Oct 24;:146533

Authors: Sahenk Z, Ak BO

Abstract

The molecular pathogenesis underlying Charcot-Marie-Tooth (CMT) neuropathy subtypes is becoming increasingly variable and identification of common approaches for treatment, independently of the disease causing gene defect, is therefore much desirable. Gene therapy approach from the clinical translational view point is particularly challenging for the most common “demyelinating” CMT1 subtypes, caused by primary Schwann cell genetic defects. Studies have shown that impaired regenerative capacity of distal axons is major contributing factor to distal axonal loss in primary Schwann cell genetic defects and neurotrophin 3 (NT-3) improves impaired regeneration in CMT1 mouse models. This review surveys the evidence supporting the rationale for AAV1.NT-3 surrogate gene therapy to improve nerve regeneration in CMT1A. The translational process, from proof of principal studies to the design of the phase I/IIa trial evaluating scAAV1.tMCK.NTF3 gene therapy for treatment of CMT1A is summarized.

PMID: 31669284 [PubMed – as supplied by publisher]

PubMed:31669284

Sahenk Z, Ak BO

https://www.nature.com/articles/s41582-019-0254-5

https://www.ncbi.nlm.nih.gov/pubmed/31582811?dopt=Abstract

Next-generation sequencing in Charcot-Marie-Tooth disease: opportunities and challenges.

Related Articles

Next-generation sequencing in Charcot-Marie-Tooth disease: opportunities and challenges.

Nat Rev Neurol. 2019 Oct 03;:

Authors: Pipis M, Rossor AM, Laura M, Reilly MM

Abstract

Charcot-Marie-Tooth disease and the related disorders hereditary motor neuropathy and hereditary sensory neuropathy, collectively termed CMT, are the commonest group of inherited neuromuscular diseases, and they exhibit wide phenotypic and genetic heterogeneity. CMT is usually characterized by distal muscle atrophy, often with foot deformity, weakness and sensory loss. In the past decade, next-generation sequencing (NGS) technologies have revolutionized genomic medicine and, as these technologies are being applied to clinical practice, they are changing our diagnostic approach to CMT. In this Review, we discuss the application of NGS technologies, including disease-specific gene panels, whole-exome sequencing, whole-genome sequencing (WGS), mitochondrial sequencing and high-throughput transcriptome sequencing, to the diagnosis of CMT. We discuss the growing challenge of variant interpretation and consider how the clinical phenotype can be combined with genetic, bioinformatic and functional evidence to assess the pathogenicity of genetic variants in patients with CMT. WGS has several advantages over the other techniques that we discuss, which include unparalleled coverage of coding, non-coding and intergenic areas of both nuclear and mitochondrial genomes, the ability to identify structural variants and the opportunity to perform genome-wide dense homozygosity mapping. We propose an algorithm for incorporating WGS into the CMT diagnostic pathway.

PMID: 31582811 [PubMed – as supplied by publisher]

PubMed:31582811

Pipis M, Rossor AM, Laura M, Reilly MM

https://www.jci.org/articles/view/130600

https://www.ncbi.nlm.nih.gov/pubmed/31557132?dopt=Abstract

Efficacy of allele-specific RNAi as a potential therapeutic for Charcot-Marie-Tooth type 2D (CMT2D)

Allele-specific RNA interference prevents neuropathy in Charcot-Marie-Tooth disease type 2D mouse models.

Allele-specific RNA interference prevents neuropathy in Charcot-Marie-Tooth disease type 2D mouse models.

J Clin Invest. 2019 Sep 26;:

Authors: Morelli KH, Griffin LB, Pyne NK, Wallace LM, Fowler AM, Oprescu SN, Takase R, Wei N, Meyer-Schuman R, Mellacheruvu D, Kitzman JO, Kocen SG, Hines TJ, Spaulding EL, Lupski JR, Nesvizhskii A, Mancias P, Butler IJ, Yang XL, Hou YM, Antonellis A, Harper SQ, Burgess RW

Abstract

Gene therapy approaches are being deployed to treat recessive genetic disorders by restoring the expression of mutated genes. However, the feasibility of these approaches for dominantly-inherited diseases-where treatment may require reduction in the expression of a toxic mutant protein resulting from a gain-of-function (GoF) allele-is unclear. Here we show the efficacy of allele-specific RNAi as a potential therapeutic for Charcot-Marie-Tooth type 2D (CMT2D), caused by dominant mutations in glycyl tRNA-synthetase (GARS). A de novo mutation in GARS was identified in a patient with a severe peripheral neuropathy, and a mouse model precisely recreating the mutation was produced. These mice developed a neuropathy by 3-4 weeks-of-age, validating the pathogenicity of the mutation. RNAi sequences targeting mutant GARS mRNA, but not wild-type, were optimized and then packaged into AAV9 for in vivo delivery. This almost completely prevented the neuropathy in mice treated at birth. Delaying treatment until after disease onset showed modest benefit, though this effect decreased the longer treatment was delayed. These outcomes were reproduced in a second mouse model of CMT2D using a vector specifically targeting that allele. The effects were dose dependent, and persisted for at least one year. Our findings demonstrate the feasibility of AAV9-mediated allele-specific knockdown and provide proof-of-concept for gene therapy approaches for dominant neuromuscular diseases.

PMID: 31557132 [PubMed – as supplied by publisher]

PubMed:31557132

Morelli KH, Griffin LB, Pyne NK, Wallace LM, Fowler AM, Oprescu SN, Takase R, Wei N, Meyer-Schuman R, Mellacheruvu D, Kitzman JO, Kocen SG, Hines TJ, Spaulding EL, Lupski JR, Nesvizhskii A, Mancias P, Butler IJ, Yang XL, Hou YM, Antonellis A, Harper SQ, Burgess RW

https://www.ncbi.nlm.nih.gov/pubmed/31525351?dopt=Abstract

https://www.sciencedirect.com/science/article/abs/pii/S000689931930513X?via%3Dihub

Genetic Modifiers and Non-Mendelian Aspects of CMT.

Genetic Modifiers and Non-Mendelian Aspects of CMT.

Brain Res. 2019 Sep 13;:146459

Authors: Bis-Brewer DM, Fazal S, Züchner S

Abstract

Charcot-Marie-Tooth (CMT) neuropathies are amongst the most common inherited diseases in neurology. While great strides have been made to identify the genesis of these diseases, a diagnostic gap of 30-60% remains. Classic models of genetic causation may be limited to fully close this gap and, thus, we review the current state and future role of alternative, non-Mendelian forms of genetics in CMT. Promising synergies exist to further define the full genetic architecture of inherited neuropathies, including affordable whole-genome sequencing, increased data aggregation and clinical collaboration, improved bioinformatics and statistical methodology, and vastly improved computational resources. Given the recent advances in genetic therapies for rare diseases, it becomes a matter of urgency to diagnose CMT patients with great fidelity. Otherwise, they will not be able to benefit from such therapeutic options, or worse, suffer harm when pathogenicity of genetic variation is falsely evaluated. In addition, the newly identified modifier and risk genes may offer alternative targets for pharmacotherapy of inherited and, potentially, even acquired forms of neuropathies.

PMID: 31525351 [PubMed – as supplied by publisher]

PubMed:31525351

Bis-Brewer DM, Fazal S, Züchner S

https://academic.oup.com/hmg/advance-article-abstract/doi/10.1093/hmg/ddz199/5549642?redirectedFrom=fulltext

https://www.ncbi.nlm.nih.gov/pubmed/31411673?dopt=Abstract

Gene replacement therapy after neuropathy onset provides therapeutic benefit in a model of CMT1X.

Gene replacement therapy after neuropathy onset provides therapeutic benefit in a model of CMT1X.

Hum Mol Genet. 2019 Aug 14;:

Authors: Kagiava A, Richter J, Tryfonos C, Karaiskos C, Heslegrave AJ, Sargiannidou I, Rossor AM, Zetterberg H, Reilly MM, Christodoulou C, Kleopa KA

Abstract

X-linked Charcot-Marie-Tooth disease (CMT1X), one of the commonest forms of inherited demyelinating neuropathy, results from GJB1 gene mutations causing loss of function of the gap junction protein connexin32 (Cx32). The aim of this study was to examine whether delayed gene replacement therapy after the onset of peripheral neuropathy can provide a therapeutic benefit in the Gjb1-null/Cx32 knockout (KO) model of CMT1X. After delivery of the LV-Mpz.GJB1 lentiviral vector by a single lumbar intrathecal injection into 6-month old Gjb1-null mice we confirmed expression of Cx32 in lumbar roots and sciatic nerves correctly localized at the paranodal myelin areas. Gjb1-null mice treated with LV-Mpz.GJB1 compared to LV-Mpz.Egfp (mock) vector at the age of 6 months showed improved motor performance at 8 and 10 months. Furthermore, treated mice showed increased sciatic nerve conduction velocities, improvement of myelination and reduced inflammation in lumbar roots and peripheral nerves at 10 months of age, along with enhanced quadriceps muscle innervation. Plasma neurofilament light (NEFL) levels, a clinically relevant biomarker, were also ameliorated in fully treated mice. Intrathecal gene delivery after the onset of peripheral neuropathy offers a significant therapeutic benefit in this disease model, providing a proof of principle for treating patients with CMT1X at different ages.

PMID: 31411673 [PubMed – as supplied by publisher]

PubMed:31411673

Kagiava A, Richter J, Tryfonos C, Karaiskos C, Heslegrave AJ, Sargiannidou I, Rossor AM, Zetterberg H, Reilly MM, Christodoulou C, Kleopa KA

https://jnnp.bmj.com/content/early/2019/06/05/jnnp-2019-320717

https://www.ncbi.nlm.nih.gov/pubmed/31167812?dopt=Abstract

Expanding the spectrum of genes responsible for hereditary motor neuropathies.

Related Articles

Expanding the spectrum of genes responsible for hereditary motor neuropathies.

J Neurol Neurosurg Psychiatry. 2019 Jun 05;:

Authors: Previtali SC, Zhao E, Lazarevic D, Pipitone GB, Fabrizi GM, Manganelli F, Mazzeo A, Pareyson D, Schenone A, Taroni F, Vita G, Bellone E, Ferrarini M, Garibaldi M, Magri S, Padua L, Pennisi E, Pisciotta C, Riva N, Scaioli V, Scarlato M, Tozza S, Geroldi A, Jordanova A, Ferrari M, Molineris I, Reilly MM, Comi G, Carrera P, Devoto M, Bolino A

Abstract

BACKGROUND: Inherited peripheral neuropathies (IPNs) represent a broad group of genetically and clinically heterogeneous disorders, including axonal Charcot-Marie-Tooth type 2 (CMT2) and hereditary motor neuropathy (HMN). Approximately 60%-70% of cases with HMN/CMT2 still remain without a genetic diagnosis. Interestingly, mutations in HMN/CMT2 genes may also be responsible for motor neuron disorders or other neuromuscular diseases, suggesting a broad phenotypic spectrum of clinically and genetically related conditions. Thus, it is of paramount importance to identify novel causative variants in HMN/CMT2 patients to better predict clinical outcome and progression.

METHODS: We designed a collaborative study for the identification of variants responsible for HMN/CMT2. We collected 15 HMN/CMT2 families with evidence for autosomal recessive inheritance, who had tested negative for mutations in 94 known IPN genes, who underwent whole-exome sequencing (WES) analyses. Candidate genes identified by WES were sequenced in an additional cohort of 167 familial or sporadic HMN/CMT2 patients using next-generation sequencing (NGS) panel analysis.

RESULTS: Bioinformatic analyses led to the identification of novel or very rare variants in genes, which have not been previously associated with HMN/CMT2 (ARHGEF28, KBTBD13, AGRN and GNE); in genes previously associated with HMN/CMT2 but in combination with different clinical phenotypes (VRK1 and PNKP), and in the SIGMAR1 gene, which has been linked to HMN/CMT2 in only a few cases. These findings were further validated by Sanger sequencing, segregation analyses and functional studies.

CONCLUSIONS: These results demonstrate the broad spectrum of clinical phenotypes that can be associated with a specific disease gene, as well as the complexity of the pathogenesis of neuromuscular disorders.

PMID: 31167812 [PubMed – as supplied by publisher]

PubMed:31167812

Previtali SC, Zhao E, Lazarevic D, Pipitone GB, Fabrizi GM, Manganelli F, Mazzeo A, Pareyson D, Schenone A, Taroni F, Vita G, Bellone E, Ferrarini M, Garibaldi M, Magri S, Padua L, Pennisi E, Pisciotta C, Riva N, Scaioli V, Scarlato M, Tozza S, Geroldi A, Jordanova A, Ferrari M, Molineris I, Reilly MM, Comi G, Carrera P, Devoto M, Bolino A

https://onlinelibrary.wiley.com/doi/full/10.1002/mgg3.676

https://www.ncbi.nlm.nih.gov/pubmed/31020813?dopt=Abstract

Whole genome sequencing reveals novel IGHMBP2 variant leading to unique cryptic splice-site and Charcot-Marie-Tooth phenotype with early onset symptoms.

Related Articles

Whole genome sequencing reveals novel IGHMBP2 variant leading to unique cryptic splice-site and Charcot-Marie-Tooth phenotype with early onset symptoms.

Mol Genet Genomic Med. 2019 Apr 25;:e00676

Authors: Cassini TA, Duncan L, Rives LC, Newman JH, Phillips JA, Koziura ME, Brault J, Hamid R, Cogan J, Undiagnosed Diseases Network

Abstract

BACKGROUND: Rare variants (RV) in immunoglobulin mu-binding protein 2 (IGHMBP2) [OMIM 600502] can cause an autosomal recessive type of Charcot-Marie-Tooth (CMT) disease [OMIM 616155], an inherited peripheral neuropathy. Over 40 different genes are associated with CMT, with different possible inheritance patterns.

METHODS AND RESULTS: An 11-year-old female with motor delays was found to have distal atrophy, weakness, and areflexia without bulbar or sensory findings. Her clinical evaluation was unrevealing. Whole exome sequencing (WES) revealed a maternally inherited IGHMBP2 RV (c.1730T>C) predicted to be pathogenic, but no variant on the other allele was identified. Deletion and duplication analysis was negative. She was referred to the Undiagnosed Disease Network (UDN) for further evaluation. Whole genome sequencing (WGS) confirmed the previously identified IGHMBP2 RV and identified a paternally inherited non-coding IGHMBP2 RV. This was predicted to activate a cryptic splice site perturbing IGHMBP2 splicing. Reverse transcriptase polymerase chain reaction (RT-PCR) analysis was consistent with activation of the cryptic splice site. The abnormal transcript was shown to undergo nonsense-mediated decay (NMD), resulting in halpoinsufficiency.

CONCLUSION: This case demonstrates the deficiencies of WES and traditional molecular analyses and highlights the advantages of utilization of WGS and functional studies.

PMID: 31020813 [PubMed – as supplied by publisher]

PubMed:31020813

Cassini TA, Duncan L, Rives LC, Newman JH, Phillips JA, Koziura ME, Brault J, Hamid R, Cogan J, Undiagnosed Diseases Network

https://n.neurology.org/content/92/15_Supplement/P3.4-045

http://indexsmart.mirasmart.com/AAN2019/PDFfiles/AAN2019-003276.pdf

GDAP1-Related Charcot-Marie-Tooth Disease: Additional Evidence for the c.692C>T Variant as a Pathogenic Mutation (P3.4-045)

https://content.iospress.com/articles/journal-of-neuromuscular-diseases/jnd190377

https://www.ncbi.nlm.nih.gov/pubmed/30958311?dopt=Abstract

Modifier Gene Candidates in Charcot-Marie-Tooth Disease Type 1A: A Case-Only Genome-Wide Association Study.

Modifier Gene Candidates in Charcot-Marie-Tooth Disease Type 1A: A Case-Only Genome-Wide Association Study.

J Neuromuscul Dis. 2019 Apr 03;:

Authors: Tao F, Beecham GW, Rebelo AP, Blanton SH, Moran JJ, Lopez-Anido C, Svaren J, Abreu L, Rizzo D, Kirk CA, Wu X, Feely S, Verhamme C, Saporta MA, Herrmann DN, Day JW, Sumner CJ, Lloyd TE, Li J, Yum SW, Taroni F, Baas F, Choi BO, Pareyson D, Scherer SS, Reilly MM, Shy ME, Züchner S, Inherited Neuropathy Consortium

Abstract

BACKGROUND: Charcot-Marie-Tooth disease type 1A (CMT1A) is caused by a uniform 1.5-Mb duplication on chromosome 17p, which includes the PMP22 gene. Patients often present the classic neuropathy phenotype, but also with high clinical variability.

OBJECTIVE: We aimed to identify genetic variants that are potentially associated with specific clinical outcomes in CMT1A.

METHODS: We genotyped over 600,000 genomic markers using DNA samples from 971 CMT1A patients and performed a case-only genome-wide association study (GWAS) to identify potential genetic association in a subset of 644 individuals of European ancestry. A total of 14 clinical outcomes were analyzed in this study.

RESULTS: The analyses yielded suggestive association signals in four clinical outcomes: difficulty with eating utensils (lead SNP rs4713376, chr6 : 30773314, P = 9.91×10-7, odds ratio = 3.288), hearing loss (lead SNP rs7720606, chr5 : 126551732, P = 2.08×10-7, odds ratio = 3.439), decreased ability to feel (lead SNP rs17629990, chr4 : 171224046, P = 1.63×10-7, odds ratio = 0.336), and CMT neuropathy score (lead SNP rs12137595, chr1 : 4094068, P = 1.14×10-7, beta = 3.014).

CONCLUSIONS: While the results require validation in future genetic and functional studies, the detected association signals may point to novel genetic modifiers in CMT1A.

PMID: 30958311 [PubMed – as supplied by publisher]

PubMed:30958311

Tao F, Beecham GW, Rebelo AP, Blanton SH, Moran JJ, Lopez-Anido C, Svaren J, Abreu L, Rizzo D, Kirk CA, Wu X, Feely S, Verhamme C, Saporta MA, Herrmann DN, Day JW, Sumner CJ, Lloyd TE, Li J, Yum SW, Taroni F, Baas F, Choi BO, Pareyson D, Scherer SS, Reilly MM, Shy ME, Züchner S, Inherited Neuropathy Consortium

https://academic.oup.com/brain/advance-article/doi/10.1093/brain/awz064/5419304

https://www.ncbi.nlm.nih.gov/pubmed/30907403?dopt=Abstract

Gene replacement therapy in a model of Charcot-Marie-Tooth 4C neuropathy.

Gene replacement therapy in a model of Charcot-Marie-Tooth 4C neuropathy.

Brain. 2019 Mar 25;:

Authors: Schiza N, Georgiou E, Kagiava A, Médard JJ, Richter J, Tryfonos C, Sargiannidou I, Heslegrave AJ, Rossor AM, Zetterberg H, Reilly MM, Christodoulou C, Chrast R, Kleopa KA

Abstract

Charcot-Marie-Tooth disease type 4C is the most common recessively inherited demyelinating neuropathy that results from loss of function mutations in the SH3TC2 gene. Sh3tc2-/- mice represent a well characterized disease model developing early onset progressive peripheral neuropathy with hypo- and demyelination, slowing of nerve conduction velocities and disturbed nodal architecture. The aim of this project was to develop a gene replacement therapy for treating Charcot-Marie-Tooth disease type 4C to rescue the phenotype of the Sh3tc2-/- mouse model. We generated a lentiviral vector LV-Mpz.SH3TC2.myc to drive expression of the human SH3TC2 cDNA under the control of the Mpz promoter specifically in myelinating Schwann cells. The vector was delivered into 3-week-old Sh3tc2-/- mice by lumbar intrathecal injection and gene expression was assessed 4-8 weeks after injection. Immunofluorescence analysis showed presence of myc-tagged human SH3TC2 in sciatic nerves and lumbar roots in the perinuclear cytoplasm of a subset of Schwann cells, in a dotted pattern co-localizing with physiologically interacting protein Rab11. Quantitative PCR analysis confirmed SH3TC2 mRNA expression in different peripheral nervous system tissues. A treatment trial was initiated in 3 weeks old randomized Sh3tc2-/- littermate mice which received either the full or mock (LV-Mpz.Egfp) vector. Behavioural analysis 8 weeks after injection showed improved motor performance in rotarod and foot grip tests in treated Sh3tc2-/- mice compared to mock vector-treated animals. Moreover, motor nerve conduction velocities were increased in treated Sh3tc2-/- mice. On a structural level, morphological analysis revealed significant improvement in g-ratios, myelin thickness, and ratios of demyelinated fibres in lumbar roots and sciatic nerves of treated Sh3tc2-/- mice. Finally, treated mice also showed improved nodal molecular architecture and reduction of blood neurofilament light levels, a clinically relevant biomarker for axonal injury/degeneration. This study provides a proof of principle for viral gene replacement therapy targeted to Schwann cells to treat Charcot-Marie-Tooth disease type 4C and potentially other similar demyelinating inherited neuropathies.

PMID: 30907403 [PubMed – as supplied by publisher]

PubMed:30907403

Schiza N, Georgiou E, Kagiava A, Médard JJ, Richter J, Tryfonos C, Sargiannidou I, Heslegrave AJ, Rossor AM, Zetterberg H, Reilly MM, Christodoulou C, Chrast R, Kleopa KA