Combined RNA interference and gene replacement therapy targeting MFN2 as proof of principle for the treatment of Charcot-Marie-Tooth type 2A.

Mitofusin-2 (MFN2) is an outer mitochondrial membrane protein essential for mitochondrial networking in most cells. Autosomal dominant mutations in the MFN2 gene cause Charcot-Marie-Tooth type 2A disease (CMT2A), a severe and disabling sensory-motor neuropathy that impacts the entire nervous system. Here, we propose a novel therapeutic strategy tailored to correcting the root genetic defect of CMT2A. Though mutant and wild-type MFN2 mRNA are inhibited by RNA interference (RNAi), the wild-type protein is restored by overexpressing cDNA encoding functional MFN2 modified to be resistant to RNAi. We tested this strategy in CMT2A patient-specific human induced pluripotent stem cell (iPSC)-differentiated motor neurons (MNs), demonstrating the correct silencing of endogenous MFN2 and replacement with an exogenous copy of the functional wild-type gene. This approach significantly rescues the CMT2A MN phenotype in vitro, stabilizing the altered axonal mitochondrial distribution and correcting abnormal mitophagic processes. The MFN2 molecular correction was also properly confirmed in vivo in the MitoCharc1 CMT2A transgenic mouse model after cerebrospinal fluid (CSF) delivery of the constructs into newborn mice using adeno-associated virus 9 (AAV9). Altogether, our data support the feasibility of a combined RNAi and gene therapy strategy for treating the broad spectrum of human diseases associated with MFN2 mutations.

Antisense Morpholino-Based In Vitro Correction of a Pseudoexon-Generating Variant in the SGCB Gene.

Limb-girdle muscular dystrophies (LGMD) are clinically and genetically heterogenous presentations displaying predominantly proximal muscle weakness due to the loss of skeletal muscle fibers. Beta-sarcoglycanopathy (LGMDR4) results from biallelic molecular defects in SGCB and features pediatric onset with limb-girdle involvement, often complicated by respiratory and heart dysfunction. Here we describe a patient who presented at the age of 12 years reporting high creatine kinase levels and onset of cramps after strenuous exercise. Instrumental investigations, including a muscle biopsy, pointed towards a diagnosis of beta-sarcoglycanopathy. NGS panel sequencing identified two variants in the SGCB gene, one of which (c.243+1548T>C) was found to promote the inclusion of a pseudoexon between exons 2 and 3 in the SGCB transcript. Interestingly, we detected the same genotype in a previously reported LGMDR4 patient, deceased more than twenty years ago, who had escaped molecular diagnosis so far. After the delivery of morpholino oligomers targeting the pseudoexon in patient-specific induced pluripotent stem cells, we observed the correction of the physiological splicing and partial restoration of protein levels. Our findings prompt the analysis of the c.243+1548T>C variant in suspected LGMDR4 patients, especially those harbouring monoallelic SGCB variants, and provide a further example of the efficacy of antisense technology for the correction of molecular defects resulting in splicing abnormalities.

MicroRNAs as serum biomarkers in Becker muscular dystrophy.

Becker muscular dystrophy (BMD) is an X-linked neuromuscular disorder due to mutation in the DMD gene, encoding dystrophin. Despite a wide clinical variability, BMD is characterized by progressive muscle degeneration and proximal muscle weakness. Interestingly, a dysregulated expression of muscle-specific microRNAs (miRNAs), called myomirs, has been found in patients affected with muscular dystrophies, although few studies have been conducted in BMD. We analysed the serum expression levels of a subset of myomirs in a cohort of 29 ambulant individuals affected by BMD and further classified according to the degree of alterations at muscle biopsy and in 11 age-matched healthy controls. We found a significant upregulation of serum miR-1, miR-133a, miR-133b and miR-206 in our cohort of BMD patients, supporting the role of these miRNAs in the pathophysiology of the disease, and we identified serum cut-off levels discriminating patients from healthy controls, confiming the potential of circulating miRNAs as promising noninvasive biomarkers. Moreover, serum levels of miR-133b were found to be associated with fibrosis at muscle biopsy and with patients' motor performances, suggesting that miR-133b might be a useful prognostic marker for BMD patients. Taken together, our data showed that these serum myomirs may represent an effective tool that may support stratification of BMD patients, providing the opportunity of both monitoring disease progression and assessing the treatment efficacy in the context of clinical trials.

Clinical, neuroradiological and genetic findings in a cohort of patients with multiple Cerebral Cavernous Malformations.

Cerebral cavernous malformations (CCM) consist of clusters of irregular dilated capillaries and represent the second most common type of vascular malformation affecting the central nervous system. CCM might be asymptomatic or cause cerebral hemorrhage, seizures, recurrent headaches and focal neurologic deficits. Causative mutations underlining CCM have been reported in three genes: KRIT1/CCM1, MGC4607/CCM2 and PDCD10/CCM3. Therapeutic avenues are limited to surgery. Here we present clinical, neuroradiological and molecular findings in a cohort of familial and sporadic CCM patients. Thirty subjects underwent full clinical and radiological assessment. Molecular analysis was performed by direct sequencing and MLPA analysis. Twenty-eight of 30 subjects (93%) experienced one or more typical CCM disturbances with cerebral/spinal hemorrhage being the most common (43%) presenting symptom. A molecular diagnosis was achieved in 87% of cases, with three novel mutations identified. KRIT1/CCM1 patients displayed higher risk of de novo CCMs appearance and bleedings. Magnetic Resonance Imaging (MRI) showed that infratentorial region was more frequently affected in mutated subjects while brainstem was often spared in patients with negative genetic testing.

Early Findings in Neonatal Cases of RYR1-Related Congenital Myopathies.

Ryanodine receptor type 1-related congenital myopathies are the most represented subgroup among congenital myopathies (CMs), typically presenting a central core or multiminicore muscle histopathology and high clinical heterogeneity. We evaluated a cohort of patients affected with Ryanodine receptor type 1-related congenital myopathy (RYR1-RCM), focusing on four patients who showed a severe congenital phenotype and underwent a comprehensive characterization at few months of life. To date there are few reports on precocious instrumental assessment. In two out of the four patients, a muscle biopsy was performed in the first days of life (day 5 and 37, respectively) and electron microscopy was carried out in two patients detecting typical features of congenital myopathy. Two patients underwent brain MRI in the first months of life (15 days and 2 months, respectively), one also a fetal brain MRI. In three children electromyography was performed in the first week of life and neurogenic signs were excluded. Muscle MRI obtained within the first years of life showed a typical pattern of RYR1-CM. The diagnosis was confirmed through genetic analysis in three out of four cases using Next Generation Sequencing (NGS) panels. The development of a correct and rapid diagnosis is a priority and may lead to prompt medical management and helps optimize inclusion in future clinical trials.

Limb girdle muscular dystrophy due to LAMA2 gene mutations: new mutations expand the clinical spectrum of a still challenging diagnosis.

Mutations in LAMA2 gene, encoding merosin, are generally responsible of a severe congenital-onset muscular dystrophy (CMD type 1A) characterized by severe weakness, merosin absence at muscle analysis and white matter alterations at brain Magnetic Resonance Imaging (MRI). Recently, LAMA2 mutations have been acknowledged as responsible of LGMD R23, despite only few cases with slowly progressive adult-onset and partial merosin deficiency have been reported. We describe 5 independent Italian subjects presenting with progressive limb girdle muscular weakness, brain white matter abnormalities, merosin deficiency and LAMA2 gene mutations. We detected 7 different mutations, 6 of which are new. All patients showed normal psicomotor development and slowly progressive weakness with onset spanning from childhood to forties. Creatin-kinase levels were moderately elevated. One patient showed dilated cardiomyopathy. Muscle MRI allowed to evaluate the degree and pattern of muscular involvement in all patients. Brain MRI was fundamental in order to address and/or support the molecular diagnosis, showing typical widespread white matter hyperintensity in T2-weighted sequences. Interestingly these alterations were associated with central nervous system involvement in 3 patients who presented epilepsy and migraine. Muscle biopsy commonly but not necessarily revealed dystrophic features. Western-blot was usually more accurate than immunohystochemical analysis in detecting merosin deficiency. The description of these cases further enlarges the clinical spectrum of LAMA2-related disorders. Moreover, it supports the inclusion of LGMD R23 in the new classification of LGMD. The central nervous system involvement was fundamental to address the diagnosis and should be always included in the diagnostic work-up of undiagnosed LGMD.

Hereditary hemorrhagic telangiectasia associated with cortical development malformation due to a start loss mutation in ENG.

BACKGROUND: Hereditary hemorrhagic telangiectasia (HHT), also known as Rendu-Osler-Weber syndrome, is a rare disorder characterized by recurrent epistaxis, telangiectasias and systemic arteriovenous malformations (AVMs). HHT is associated with mutations in genes encoding for proteins involved in endothelial homeostasis such as ENG (endoglin) and ACVRL1 (activin receptor-like kinase-1). CASE PRESENTATION: Here we describe a 22-year-old male presenting with a transient episode of slurred speech and left arm paresis. Brain MRI displayed polymicrogyria. A right-to-left shunt in absence of an atrial septum defect was noted. Chest CT revealed multiple pulmonary AVMs, likely causing paradoxical embolism manifesting as a transient ischemic attack. The heterozygous ENG variant, c.3G > A (p.Met1lle), was detected in the patient. This variant was also found in patient's mother and in his younger brother who displayed cortical dysplasia type 2. CONCLUSIONS: The detection of cortical development malformations in multiple subjects from the same pedigree may expand the phenotypic features of ENG-related HHT patients. We suggest considering HHT in young patients presenting with acute cerebral ischemic events of unknown origin.

Neural Stem Cell Transplantation for Neurodegenerative Diseases.

Neurodegenerative diseases are disabling and fatal neurological disorders that currently lack effective treatment. Neural stem cell (NSC) transplantation has been studied as a potential therapeutic approach and appears to exert a beneficial effect against neurodegeneration via different mechanisms, such as the production of neurotrophic factors, decreased neuroinflammation, enhanced neuronal plasticity and cell replacement. Thus, NSC transplantation may represent an effective therapeutic strategy. To exploit NSCs' potential, some of their essential biological characteristics must be thoroughly investigated, including the specific markers for NSC subpopulations, to allow profiling and selection. Another key feature is their secretome, which is responsible for the regulation of intercellular communication, neuroprotection, and immunomodulation. In addition, NSCs must properly migrate into the central nervous system (CNS) and integrate into host neuronal circuits, enhancing neuroplasticity. Understanding and modulating these aspects can allow us to further exploit the therapeutic potential of NSCs. Recent progress in gene editing and cellular engineering techniques has opened up the possibility of modifying NSCs to express select candidate molecules to further enhance their therapeutic effects. This review summarizes current knowledge regarding these aspects, promoting the development of stem cell therapies that could be applied safely and effectively in clinical settings.

CSF transplantation of a specific iPSC-derived neural stem cell subpopulation ameliorates the disease phenotype in a mouse model of spinal muscular atrophy with respiratory distress type 1.

Spinal muscular atrophy with respiratory distress type 1 (SMARD1) is a genetic motor neuron disease affecting infants. This condition is caused by mutations in the IGHMBP2 gene and currently has no cure. Stem cell transplantation is a potential therapeutic strategy for motor neuron diseases such as SMARD1, exerting beneficial effects both by replacing cells and by providing support to endogenous motor neurons. In this work, we demonstrate that human induced pluripotent stem cell (iPSC)-derived neural stem cells (NSCs) selected for the expression of specific markers, namely, Lewis X, CXCR4 and beta 1 integrin, and pretreated with neurotrophic factors and apoptosis/necroptosis inhibitors were able to effectively migrate and engraft into the host parenchyma after administration into the cerebrospinal fluid in a SMARD1 mouse model. We were able to detect donor cells in the ventral horn of the spinal cord and observe improvements in neuropathological features, particularly preservation of the integrity of the motor unit, that were correlated with amelioration of the SMARD1 disease phenotype in terms of neuromuscular function and lifespan. This minimally invasive stem cell approach can confer major advantages in the context of cell-mediated therapy for patients with neurodegenerative diseases.

Advances, Challenges, and Perspectives in Translational Stem Cell Therapy for Amyotrophic Lateral Sclerosis.

Finding an effective therapeutic approach is a primary goal for current and future research for amyotrophic lateral sclerosis (ALS), a fatal neurological disease characterized by degeneration and loss of upper and lower motor neurons. Transplantation approaches based on stem cells have been attempted in virtue of their potential to contrast simultaneously different ALS pathogenic aspects including either the replacement of lost cells or the protection of motor neurons from degeneration and toxic microenvironment. Here, we critically review the recent translational research aimed at the assessment of stem cell transplantation safety and feasibility in the treatment of ALS. Most of these efforts aim to exert a neuroprotective action rather than cell replacement. Critical aspects that emerge in these studies are the need for the identification of the most effective therapeutic cell source (mesenchymal stem cells, immune, or neural stem cells), the definition of the optimal injection site (cortical area, spinal cord, or muscles) with a suitable administration protocol (local or systemic injection), and the analysis of therapeutic mechanisms, which are necessary steps in order to overcome the hurdles posed by previous in vivo human studies. New perspectives will also be offered by the increasing number of induced pluripotent stem cell-based therapies that are now being tested in clinical trials. A thorough analysis of recently completed trials is the foundation for continued progress in cellular therapy for ALS and other neurodegenerative disorders.

Key role of SMN/SYNCRIP and RNA-Motif 7 in spinal muscular atrophy: RNA-Seq and motif analysis of human motor neurons.

Spinal muscular atrophy is a motor neuron disorder caused by mutations in SMN1. The reasons for the selective vulnerability of motor neurons linked to SMN (encoded by SMN1) reduction remain unclear. Therefore, we performed deep RNA sequencing on human spinal muscular atrophy motor neurons to detect specific altered gene splicing/expression and to identify the presence of a common sequence motif in these genes. Many deregulated genes, such as the neurexin and synaptotagmin families, are implicated in critical motor neuron functions. Motif-enrichment analyses of differentially expressed/spliced genes, including neurexin2 (NRXN2), revealed a common motif, motif 7, which is a target of SYNCRIP. Interestingly, SYNCRIP interacts only with full-length SMN, binding and modulating several motor neuron transcripts, including SMN itself. SYNCRIP overexpression rescued spinal muscular atrophy motor neurons, due to the subsequent increase in SMN and their downstream target NRXN2 through a positive loop mechanism and ameliorated SMN-loss-related pathological phenotypes in Caenorhabditis elegans and mouse models. SMN/SYNCRIP complex through motif 7 may account for selective motor neuron degeneration and represent a potential therapeutic target.

Preconditioning and Cellular Engineering to Increase the Survival of Transplanted Neural Stem Cells for Motor Neuron Disease Therapy.

Despite the extensive research effort that has been made in the field, motor neuron diseases, namely, amyotrophic lateral sclerosis and spinal muscular atrophies, still represent an overwhelming cause of morbidity and mortality worldwide. Exogenous neural stem cell-based transplantation approaches have been investigated as multifaceted strategies to both protect and repair upper and lower motor neurons from degeneration and inflammation. Transplanted neural stem cells (NSCs) exert their beneficial effects not only through the replacement of damaged cells but also via bystander immunomodulatory and neurotrophic actions. Notwithstanding these promising findings, the clinical translatability of such techniques is jeopardized by the limited engraftment success and survival of transplanted cells within the hostile disease microenvironment. To overcome this obstacle, different methods to enhance graft survival, stability, and therapeutic potential have been developed, including environmental stress preconditioning, biopolymers scaffolds, and genetic engineering. In this review, we discuss current engineering techniques aimed at the exploitation of the migratory, proliferative, and secretive capacity of NSCs and their relevance for the therapeutic arsenal against motor neuron disorders and other neurological disorders.

R-Loops in Motor Neuron Diseases.

R loops are transient three-stranded nucleic acid structures that form physiologically during transcription when a nascent RNA transcript hybridizes with the DNA template strand, leaving a single strand of displaced nontemplate DNA. However, aberrant persistence of R-loops can cause DNA damage by inducing genomic instability. Indeed, evidence has emerged that R-loops might represent a key element in the pathogenesis of human diseases, including cancer, neurodegeneration, and motor neuron disorders. Mutations in genes directly involved in R-loop biology, such as SETX (senataxin), or unstable DNA expansion eliciting R-loop generation, such as C9ORF72 HRE, can cause DNA damage and ultimately result in motor neuron cell death. In this review, we discuss current advancements in this field with a specific focus on motor neuron diseases associated with deregulation of R-loop structures. These mechanisms can represent novel therapeutic targets for these devastating, incurable diseases.

Central Nervous System Involvement in Common Variable Immunodeficiency: A Case of Acute Unilateral Optic Neuritis in a 26-Year-Old Italian Patient.

Common Variable Immunodeficiency (CVID) is a group of heterogeneous primary immunodeficiencies sharing defective B lymphocytes maturation and dysregulated immune response and resulting in impaired immunoglobulin production. Clinical picture encompasses increased susceptibility to infections, hematologic malignancies, inflammatory, and autoimmune diseases. Neurological manifestations are uncommon and optic neuritis has been previously reported only in one case with bilateral involvement. We hereby report a case of a 26-year-old man affected by CVID undergoing regular immunoglobulin supplementation, who presented with acute unilateral demyelinating optic neuritis and lymphocytic pleocytosis in the cerebrospinal fluid. A variety of infectious, inflammatory, and neoplastic conditions were excluded and a diagnosis of clinically isolated optic neuritis was made. The patient was treated with a short course of intravenous steroids with complete recovery. Overall, this case expands our current knowledge about clinical spectrum of complications in CVID and highlights the need for further research about this complex disease.

MicroRNA expression analysis identifies a subset of downregulated miRNAs in ALS motor neuron progenitors.

Amyotrophic lateral sclerosis (ALS) is a fatal neurological disorder that is characterized by a progressive degeneration of motor neurons (MNs). The pathomechanism underlying the disease is largely unknown, even though increasing evidence suggests that RNA metabolism, including microRNAs (miRNAs) may play an important role. In this study, human ALS induced pluripotent stem cells were differentiated into MN progenitors and their miRNA expression profiles were compared to those of healthy control cells. We identified 15 downregulated miRNAs in patients' cells. Gene ontology and molecular pathway enrichment analysis indicated that the predicted target genes of the differentially expressed miRNAs were involved in neurodegeneration-related pathways. Among the 15 examined miRNAs, miR-34a and miR504 appeared particularly relevant due to their involvement in the p53 pathway, synaptic vesicle regulation and general involvement in neurodegenerative diseases. Taken together our results demonstrate that the neurodegenerative phenotype in ALS can be associated with a dysregulation of miRNAs involved in the control of disease-relevant genetic pathways, suggesting that targeting entire gene networks can be a potential strategy to treat complex diseases such as ALS.

A new case of limb girdle muscular dystrophy 2G in a Greek patient, founder effect and review of the literature.

Limb girdle muscular dystrophy (LGMD) type 2G is a rare form of muscle disease, described only in a few patients worldwide, caused by mutations in TCAP gene, encoding the protein telethonin. It is characterised by proximal limb muscle weakness associated with distal involvement of lower limbs, starting in the first or second decade of life. We describe the case of a 37-year-old woman of Greek origin, affected by disto-proximal lower limb weakness. No cardiac or respiratory involvement was detected. Muscle biopsy showed myopathic changes with type I fibre hypotrophy, cytoplasmic vacuoles, lipid overload, multiple central nuclei and fibre splittings; ultrastructural examination showed metabolic abnormalities. Next generation sequencing analysis detected a homozygous frameshift mutation in the TCAP gene (c.90_91del), previously described in one Turkish family. Immunostaining and Western blot analysis showed complete absence of telethonin. Interestingly, Single Nucleotide Polymorphism analysis of the 10 Mb genomic region containing the TCAP gene showed a shared homozygous haplotype of both the Greek and the Turkish patients, thus suggesting a possible founder effect of TCAP gene c.90_91del mutation in this part of the Mediterranean area.

Progressive Encephalomyelitis with Rigidity and Myoclonus Associated With Anti-GlyR Antibodies and Hodgkin's Lymphoma: A Case Report.

INTRODUCTION: A 60-year-old man presented with a 6-month history of low back pain and progressive rigidity of the trunk and lower limbs, followed by pruritus, dysphonia, hyperhydrosis, and urinary retention. Brain and spinal imaging were normal. EMG showed involuntary motor unit hyperactivity. Onconeural, antiglutamic acid decarboxylase (anti-GAD), voltage-gated potassium channel, and dipeptidyl peptidase-like protein 6 (DPPX) autoantibodies were negative. CSF was negative. Symptoms were partially responsive to baclofen, gabapentin, and clonazepam, but he eventually developed severe dysphagia. Antiglycine receptor (anti-GlyR) antibodies turned out positive on both serum and CSF. A plasmapheresis cycle was completed with good clinical response. A PET scan highlighted an isolated metabolically active axillary lymphnode that turned out to be a classic type Hodgkin lymphoma (HL), in the absence of bone marrow infiltration nor B symptoms. Polychemotherapy with ABVD protocol was completed with good clinical response and at 1-year follow-up the neurological examination is normal. BACKGROUND: Progressive encephalomyelitis with rigidity and myoclonus (PERM) is a rare and severe neurological syndrome characterized by muscular rigidity and spasms as well as brain stem and autonomic dysfunction. It can be associated with anti-GAD, GlyR, and DPPX antibodies. All of these autoantibodies may be variably associated with malignant tumors and their response to immunotherapy, as well as to tumor removal, is not easily predictable. CONCLUSION: Progressive encephalomyelitis with rigidity and myoclonus has already been described in association with HL, but this is the first case report of a HL manifesting as anti-GlyR antibodies related PERM. Our report highlights the importance of malignancy screening in autoimmune syndromes of suspected paraneoplastic origin.

Selective mitochondrial depletion, apoptosis resistance, and increased mitophagy in human Charcot-Marie-Tooth 2A motor neurons.

Charcot-Marie-Tooth 2A (CMT2A) is an inherited peripheral neuropathy caused by mutations in MFN2, which encodes a mitochondrial membrane protein involved in mitochondrial network homeostasis. Because MFN2 is expressed ubiquitously, the reason for selective motor neuron (MN) involvement in CMT2A is unclear. To address this question, we generated MNs from induced pluripotent stem cells (iPSCs) obtained from the patients with CMT2A as an in vitro disease model. CMT2A iPSC-derived MNs (CMT2A-MNs) exhibited a global reduction in mitochondrial content and altered mitochondrial positioning without significant differences in survival and axon elongation. RNA sequencing profiles and protein studies of key components of the apoptotic executioner program (i.e. p53, BAX, caspase 8, cleaved caspase 3, and the anti-apoptotic marker Bcl2) demonstrated that CMT2A-MNs are more resistant to apoptosis than wild-type MNs. Exploring the balance between mitochondrial biogenesis and the regulation of autophagy-lysosome transcription, we observed an increased autophagic flux in CMT2A-MNs that was associated with increased expression of PINK1, PARK2, BNIP3, and a splice variant of BECN1 that was recently demonstrated to be a trigger for mitochondrial autophagic removal. Taken together, these data suggest that the striking reduction in mitochondria in MNs expressing mutant MFN2 is not the result of impaired biogenesis, but more likely the consequence of enhanced mitophagy. Thus, these pathways represent possible novel molecular therapeutic targets for the development of an effective cure for this disease.

Mutational analysis of COQ2 in patients with MSA in Italy.

COQ2 mutations have been implicated in the etiology of multiple system atrophy (MSA) in Japan. However, several genetic screenings have not confirmed the role of its variants in the disease. We performed COQ2 sequence analysis in 87 probable MSA. A homozygous change p.A43G was found in an MSA-C patient. Cosegregation analysis and the evaluation of CoQ10 content in muscle and fibroblasts did not support the pathogenic role of this variant.