A Novel Solution-Gated Graphene Transistor Biosensor for Ultrasensitive Detection of Trinucleotide Repeats

Zhiqi Ge, Mingyu Ma, Zang Chang, Meijun Chen, Hanping He, Xiuhua Zhang and Shengfu Wang, 2020, doi:10.1039/D0AN00205D

A new way to detect GAA trinucleotide repeats (TNR) based on solution-gated graphene transistor (SGGT) with high performance was developed. Friedreich's ataxia (FRDA) is a neurodegenerative disease where the first intron of the frataxin (FXN) gene exhibits an extended GAA repeat region. Herein, a SGGT biosensor was constructed based on G-quadruplex DNAzymes and graphene channels. The DNAzymes quantify the captured target DNA by producing a strong catalytic current signal depending on the peroxidase-like activity. The higher the target DNA quantity captured on the gate electrode is, the higher is the concentration of DNAzymes on the surface of the gate electrode, which generates a high catalytic current. Due to the excellent self-amplifying performance of the transistor, the current signal of the SGGT is several hundreds of times larger than in conventional electrochemistry under identical detection conditions. Moreover, a large current signal can be obtained in the case of a low concentration of H2O2 when compared to the case of an enzyme-catalyzed transistor. The SGGT biosensor also exhibits ultra-low detection limit (32.25 fM), a wide linear range (100 fM–100 nM), and excellent selectivity. The results show that the SGGT biosensor shows a great potential in the early diagnosis of neurodegenerative diseases.

Cerebellar cognitive disorder parallels cerebellar motor symptoms in Friedreich ataxia

Naeije, G., Rai, M., Allaerts, N., Sjogard, M., De Tiège, X. and Pandolfo, M.; Ann Clin Transl Neurol. doi:10.1002/acn3.51079

Dentate nuclei (DN) are involved in cerebellar modulation of motor and cognitive functions, whose impairment causes ataxia and cerebellar cognitive affective syndrome (CCAS). Friedreich ataxia (FRDA) disease progression relates to degeneration of the dentate nucleus and dentato‐thalamic pathways, causing cerebellar ataxia. Volumetric MRI also shows mild loss in the cerebellar cortex, brainstem, and motor cortex. Cognitive deficits occur in FRDA, but their relationship with ataxia progression is not fully characterized. We found a significant positive correlation between severity of patients’ ataxia and more marked CCAS as assessed with the CCAS‐Scale. This relation could be related to progressive DN impairment.

HMTase Inhibitors as a Potential Epigenetic-Based Therapeutic Approach for Friedreich’s Ataxia

Sherzai, Mursal; Valle, Adamo; Perry, Nicholas; Kalef-Ezra, Ester; Al-Mahdawi, Sahar; Pook, Mark; Sara Anjomani Virmouni. Frontiers. Collection. doi:10.3389/fgene.2020.00584

Recent findings suggest that abnormal GAA expansion plays a role in histone modification, subjecting the FXN gene to heterochromatin silencing. Therefore, as an epigenetic-based therapy, we investigated the efficacy and tolerability of two histone methyltransferase (HMTase) inhibitor compounds, BIX0194 (G9a-inhibitor) and GSK126 (EZH2-inhibitor), to specifically target and reduce H3K9me2/3 and H3K27me3 levels, respectively, in FRDA fibroblasts. We show that a combination treatment of BIX0194 and GSK126, significantly increased FXN gene expression levels and reduced the repressive histone marks. However, no increase in frataxin protein levels was observed. Nevertheless, our results are still promising and may encourage to investigate HMTase inhibitors with other synergistic epigenetic-based therapies for further preliminary studies.

Functional coupling of presequence processing and degradation in human mitochondria

Kücükköse, C., Taskin, A.A., Marada, A., Brummer, T., Dennerlein, S. and Vögtle, F.‐N. (2020), FEBS J. doi:10.1111/febs.15358

The mitochondrial proteome is built and maintained mainly by import of nuclear‐encoded precursor proteins. Most of these precursors use N‐terminal presequences as targeting signals that are removed by mitochondrial matrix proteases. The essential mitochondrial processing protease MPP cleaves presequences after import into the organelle thereby enabling protein folding and functionality. The cleaved presequences are subsequently degraded by peptidases. While most of these processes have been discovered in yeast, characterization of the human enzymes is still scarce.

Significance of NT-proBNP and High-sensitivity Troponin in Friedreich Ataxia

Legrand, L.; Maupain, C.; Monin, M.-L.; Ewenczyk, C.; Isnard, R.; Alkouri, R.; Durr, A.; Pousset, F.; J. Clin. Med. 2020, 9, 1630. doi:10.3390/jcm9061630

Conclusion: hsTnT was increased in 1/3 of the adult FA and associated with increased septal wall thickness. Increased NT-proBNP remained a marker of increased left ventricular filling pressure. This could be used to identify patients that should undergo a closer cardiac surveillance.

Efficacy and Safety of CSF- Delivered AVXS-401 in Mice and NonHuman Primates for the Treatment of Friedreich’s Ataxia

Martin Fugere, Rajeev Sivasankaran, Susan McQuown, Chang Choi, Katrina Salvador, Shirley Phillips, Yin Gu, Binh Chu, Janet Do, Tsun-Kai Chang, Katherine Nguyen, Yanchi Li, Stephanie Solano, Natalia Teider, Colin Fennelly, Ricardo Dolmetsch, Monica Bennett, Kevin Foust, Page Bouchard; AveXis Research and Development, San Diego, CA, Novartis Institutes for Biomedical Research, Cambridge, MA

For clinical translation, we developed AVXS-401, a self-complementary adenoassociated virus (AAV9) based gene replacement therapy to provide sustained expression of FXN in key tissues relevant to FA. Toxicity studies in wildtype mice proved AVXS-401 is safe and well-tolerated. Dose ranging efficacy studies following a one-time, pre-symptomatic intracerebroventricular (ICV) administration of AVXS-401 in conditional FXN-deficient mice in the CNS (Pvalb) demonstrates amelioration of behavioral phenotypes, rescue of Purkinje neurons and cerebellar gliosis at low doses. ICV delivery of AVXS-401 in cardiac mutants (MCK) results in full recovery of cardiac functions as measured by magnetic resonance imaging (MRI), prevention of histopathological evidence of cardiomyopathy and >300% increase in median survival at efficacious doses.
Scale up of therapeutic doses to non-human primates (NHP) showed that AVXS-401 is safe and well tolerated with no aberrant behavior, clinical or anatomical pathology attributable to frataxin expression. Importantly, AVXS-401 provides durable mRNA transcription in the CNS and heart of NHP at 6 months postinjection with frataxin expression detectable above endogenous levels. Dose escalation studies by intrathecal (IT) administration in NHP show a dose correlation between mice and NHP by ddPCR quantification of vector genomes. Together these pre-clinical data show that AVXS-401 is suitable for first-inhuman studies.

PTC announced delays in its gene therapy program for Friedreich’s ataxia

MAY 19, 2020. PTC announced delays in its gene therapy program for Friedreich’s ataxia and in the opening of a manufacturing facility in New Jersey, which is now expected to begin producing clinical material early next year.

Minoryx Therapeutics doses first patient with leriglitazone in registration-enabling cALD NEXUS trial

20-May-2020. PharmiWeb.com. Mataró, Barcelona, Spain and Charleroi, Belgium, May 12, 2020 – Minoryx Therapeutics, a company that specializes in the development of innovative treatments for orphan Central Nervous System (CNS) diseases, today announces the initiation of the registration-enabling Phase 2 NEXUS trial to evaluate the safety and efficacy of leriglitazone in pediatric patients with early-stage cerebral ALD (cALD), the acute form of X-linked adrenoleukodystrophy (X-ALD).

Leriglitazone has also completed enrolment in FRAMES, a one year double-blind, placebo-controlled Phase 2 study in patients with Friedreich’s Ataxia. Results from ADVANCE and FRAMES are expected by the end of 2020 and results from NEXUS are expected in 2021. Leriglitazone has obtained Orphan Drug Designation from the European Commission and the FDA in X-ALD and Friedreich’s Ataxia.

Non-Invasive Cerebellar Stimulation in Neurodegenerative Ataxia: A Literature Review

Benussi A, Pascual-Leone A, Borroni B.; International Journal of Molecular Sciences. 2020 Mar;21(6). DOI: 10.3390/ijms21061948.

In light of limited evidence-based pharmacologic and non-pharmacologic treatment options for patients with ataxia, several different non-invasive brain stimulation protocols have emerged, particularly employing repetitive transcranial magnetic stimulation (rTMS) or transcranial direct current stimulation (tDCS) techniques. In this review, we summarize the most relevant rTMS and tDCS therapeutic trials and discuss their implications in the care of patients with degenerative ataxias.

J. Analysis of Putative Epigenetic Regulatory Elements in the FXN Genomic Locus

Fernández-Frías, I.; Pérez-Luz, S.; Díaz-Nido. Int. J. Mol. Sci. 2020, 21, 3410.

Friedreich´s ataxia (FRDA) is an autosomal recessive disease caused by an abnormally expanded Guanine-Adenine-Adenine (GAA) repeat sequence within the first intron of the frataxin gene (FXN). The molecular mechanisms associated with FRDA are still poorly understood and most studies on FXN gene regulation have been focused on the region around the minimal promoter and the region in which triplet expansion occurs. Nevertheless, since there could be more epigenetic changes involved in the reduced levels of FXN transcripts, the aim of this study was to obtain a more detailed view of the possible regulatory elements by analyzing data from ENCODE and Roadmap consortia databases. This bioinformatic analysis indicated new putative regulatory regions within the FXN genomic locus, including exons, introns, and upstream and downstream regions. Moreover, the region next to the end of intron 4 is of special interest, since the enhancer signals in FRDA-affected tissues are weak or absent in this region, whilst they are strong in the rest of the analyzed tissues. Therefore, these results suggest that there could be a direct relationship between the absence of enhancer sequences in this specific region and their predisposition to be affected in this pathology.