Bone marrow transplantation stimulates neural repair in Friedreich's ataxia mice

Cerebellum Lecture: the Cerebellar Nuclei-Core of the Cerebellum

The cerebellum is a key player in many brain functions and a major topic of neuroscience research. However, the cerebellar nuclei (CN), the main output structures of the cerebellum, are often overlooked. This neglect is because research on the cerebellum typically focuses on the cortex and tends to treat the CN as relatively simple output nuclei conveying an inverted signal from the cerebellar cortex to the rest of the brain. In this review, by adopting a nucleocentric perspective we aim to rectify this impression. First, we describe CN anatomy and modularity and comprehensively integrate CN architecture with its highly organized but complex afferent and efferent connectivity. This is followed by a novel classification of the specific neuronal classes the CN comprise and speculate on the implications of CN structure and physiology for our understanding of adult cerebellar function. Based on this thorough review of the adult literature we provide a comprehensive overview of CN embryonic development and, by comparing cerebellar structures in various chordate clades, propose an interpretation of CN evolution. Despite their critical importance in cerebellar function, from a clinical perspective intriguingly few, if any, neurological disorders appear to primarily affect the CN. To highlight this curious anomaly, and encourage future nucleocentric interpretations, we build on our review to provide a brief overview of the various syndromes in which the CN are currently implicated. Finally, we summarize the specific perspectives that a nucleocentric view of the cerebellum brings, move major outstanding issues in CN biology to the limelight, and provide a roadmap to the key questions that need to be answered in order to create a comprehensive integrated model of CN structure, function, development, and evolution.

A new FRDA mouse model [Fxn null:YG8s(GAA) > 800] with more than 800 GAA repeats

Introduction

Friedreich's ataxia (FRDA) is an inherited recessive neurodegenerative disorder caused by a homozygous guanine-adenine-adenine (GAA) repeat expansion within intron 1 of the FXN gene, which encodes the essential mitochondrial protein frataxin. There is still no effective therapy for FRDA, therefore the development of optimal cell and animal models of the disease is one of the priorities for preclinical therapeutic testing.

Methods

We obtained the latest FRDA humanized mouse model that was generated on the basis of our previous YG8sR, by Jackson laboratory [YG8JR, Fxn ^null:YG8s(GAA) > 800]. We characterized the behavioral, cellular, molecular and epigenetics properties of the YG8JR model, which has the largest GAA repeat sizes compared to all the current FRDA mouse models.

Results

We found statistically significant behavioral deficits, together with reduced levels of frataxin mRNA and protein, and aconitase activity in YG8JR mice compared with control Y47JR mice. YG8JR mice exhibit intergenerational GAA repeat instability by the analysis of parent and offspring tissue samples. Somatic GAA repeat instability was also detected in individual brain and cerebellum tissue samples. In addition, increased DNA methylation of CpG U13 was identified in FXN GAA repeat region in the brain, cerebellum, and heart tissues. Furthermore, we show decreased histone H3K9 acetylation and increased H3K9 methylation of YG8JR cerebellum tissues within the FXN gene, upstream and downstream of the GAA repeat region compared to Y47JR controls.

Discussion

These studies provide a detailed characterization of the GAA repeat expansion-based YG8JR transgenic mouse models that will help investigations of FRDA disease mechanisms and therapy.

An open-label pilot study of recombinant granulocyte-colony stimulating factor in Friedreich's ataxia

Friedreich's ataxia (FA) is an inherited progressive neurodegenerative disease for which there is no proven disease-modifying treatment. Here we perform an open-label, pilot study of recombinant human granulocyte-colony stimulating factor (G-CSF) administration in seven people with FA (EudraCT: 2017-003084-34); each participant receiving a single course of G-CSF (Lenograstim; 1.28 million units per kg per day for 5 days). The primary outcome is peripheral blood mononuclear cell frataxin levels over a 19-day period. The secondary outcomes include safety, haematopoietic stem cell (HSC) mobilisation, antioxidant levels and mitochondrial enzyme activity. The trial meets pre-specified endpoints. We show that administration of G-CSF to people with FA is safe. Mobilisation of HSCs in response to G-CSF is comparable to that of healthy individuals. Notably, sustained increases in cellular frataxin concentrations and raised PGC-1α and Nrf2 expression are detected. Our findings show potential for G-CSF therapy to have a clinical impact in people with FA.

Advantages and Limitations of Gene Therapy and Gene Editing for Friedreich's Ataxia

Friedreich's ataxia (FRDA) is an inherited, multisystemic disorder predominantly caused by GAA hyper expansion in intron 1 of frataxin (FXN) gene. This expansion mutation transcriptionally represses FXN, a mitochondrial protein that is required for iron metabolism and mitochondrial homeostasis, leading to neurodegerative and cardiac dysfunction. Current therapeutic options for FRDA are focused on improving mitochondrial function and increasing frataxin expression through pharmacological interventions but are not effective in delaying or preventing the neurodegeneration in clinical trials. Recent research on in vivo and ex vivo gene therapy methods in FRDA animal and cell models showcase its promise as a one-time therapy for FRDA. In this review, we provide an overview on the current and emerging prospects of gene therapy for FRDA, with specific focus on advantages of CRISPR/Cas9-mediated gene editing of FXN as a viable option to restore endogenous frataxin expression. We also assess the potential of ex vivo gene editing in hematopoietic stem and progenitor cells as a potential autologous transplantation therapeutic option and discuss its advantages in tackling FRDA-specific safety aspects for clinical translation.

An Overview of the Current State and the Future of Ataxia Treatments

Cerebellar ataxia can be caused by a variety of disorders, including degenerative processes, autoimmune and paraneoplastic illness as well as by gene mutations inherited in autosomal dominant, autosomal recessive, or X-linked fashions. In this review, we highlight the treatments for cerebellar ataxia in a systematic way, to provide guidance for clinicians who treat patients with cerebellar ataxia. In addition, we review therapies currently under development for ataxia, which we feel is currently one of the most exciting fields in neurology.

Molecular Mechanisms and Therapeutics for the GAA·TTC Expansion Disease Friedreich Ataxia

Friedreich ataxia (FRDA), the most common inherited ataxia, is caused by transcriptional silencing of the nuclear FXN gene, encoding the essential mitochondrial protein frataxin. Currently, there is no approved therapy for this fatal disorder. Gene silencing in FRDA is due to hyperexpansion of the triplet repeat sequence GAA·TTC in the first intron of the FXN gene, which results in chromatin histone modifications consistent with heterochromatin formation. Frataxin is involved in mitochondrial iron homeostasis and the assembly and transfer of iron-sulfur clusters to various mitochondrial enzymes and components of the electron transport chain. Frataxin insufficiency leads to progressive spinocerebellar neurodegeneration, causing symptoms of gait and limb ataxia, slurred speech, muscle weakness, sensory loss, and cardiomyopathy in many patients, resulting in death in early adulthood. Numerous approaches are being taken to find a treatment for FRDA, including excision or correction of the repeats by genome engineering methods, gene activation with small molecules or artificial transcription factors, delivery of frataxin to affected cells by protein replacement therapy, gene therapy, or small molecules to increase frataxin protein levels, and therapies aimed at countering the cellular consequences of reduced frataxin. This review will summarize the mechanisms involved in repeat-mediated gene silencing and recent efforts aimed at development of therapeutics.

Iron Pathophysiology in Friedreich's Ataxia

Friedreich's ataxia (FRDA) is a degenerative disease that affects both the central and the peripheral nervous systems and non-neural tissues including, mainly, heart, and endocrine pancreas. It is an autosomal recessive disease caused by a GAA triplet-repeat localized within an Alu sequence element in intron 1 of frataxin (FXN) gene, which encodes a mitochondrial protein FXN. This protein is essential for mitochondrial function by the involvement of iron-sulfur cluster biogenesis. The effects of its deficiency also include disruption of cellular, particularly mitochondrial, iron homeostasis, i.e., relatively more iron accumulated in mitochondria and less iron presented in cytosol. Though iron toxicity is commonly thought to be mediated via Fenton reaction, oxidative stress seems not to be the main problem to result in detrimental effects on cell survival, particularly neuron survival. Therefore, the basic research on FXN function is urgently demanded to understand the disease. This chapter focuses on the outcome of FXN expression, regulation, and function in cellular or animal models of FRDA and on iron pathophysiology in the affected tissues. Finally, therapeutic strategies based on the control of iron toxicity and iron cellular redistribution are considered. The combination of multiple therapeutic targets including iron, oxidative stress, mitochondrial function, and FXN regulation is also proposed.

shRNA-mediated PPARα knockdown in human glioma stem cells reduces in vitro proliferation and inhibits orthotopic xenograft tumour growth

The overall survival for patients with primary glioblastoma is very poor. Glioblastoma contains a subpopulation of glioma stem cells (GSC) that are responsible for tumour initiation, treatment resistance and recurrence. PPARα is a transcription factor involved in the control of lipid, carbohydrate and amino acid metabolism. We have recently shown that PPARα gene and protein expression is increased in glioblastoma and has independent clinical prognostic significance in multivariate analyses. In this work, we report that PPARα is overexpressed in GSC compared to foetal neural stem cells. To investigate the role of PPARα in GSC, we knocked down its expression using lentiviral transduction with short hairpin RNA (shRNA). Transduced GSC were tagged with luciferase and stereotactically xenografted into the striatum of NOD-SCID mice. Bioluminescent and magnetic resonance imaging showed that knockdown (KD) of PPARα reduced the tumourigenicity of GSC in vivo. PPARα-expressing control GSC xenografts formed invasive histological phenocopies of human glioblastoma, whereas PPARα KD GSC xenografts failed to establish viable intracranial tumours. PPARα KD GSC showed significantly reduced proliferative capacity and clonogenic potential in vitro with an increase in cellular senescence. In addition, PPARα KD resulted in significant downregulation of the stem cell factors c-Myc, nestin and SOX2. This was accompanied by downregulation of the PPARα-target genes and key regulators of fatty acid oxygenation ACOX1 and CPT1A, with no compensatory increase in glycolytic flux. These data establish the aberrant overexpression of PPARα in GSC and demonstrate that this expression functions as an important regulator of tumourigenesis, linking self-renewal and the malignant phenotype in this aggressive cancer stem cell subpopulation. We conclude that targeting GSC PPARα expression may be a therapeutically beneficial strategy with translational potential as an adjuvant treatment. © 2018 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of Pathological Society of Great Britain and Ireland.

In vivo somatic cell reprogramming for tissue regeneration: the emerging role of the local microenvironment

The past few years have witnessed an exponential increase of interest in the reprogramming process. This has been motivated by the enthusiasm of unravelling key aspects not only of cell identity and dedifferentiation, but also of the endogenous regenerative capacities of mammalian organs. Here, we present the most recent advances in the field of reprogramming, stressing how they are re-defining the rules of cell fate and plasticity in vivo. Specifically, we focus on the emerging role of the tissue microenvironment, with particular emphasis on tissue damage, inflammation and senescence that can facilitate in vivo reprogramming and regeneration through cell-extrinsic mechanisms.