A high-throughput screening identifies microRNA inhibitors that influence neuronal maintenance and/or response to oxidative stress

Oxidative stress; Small RNA sequencing; NeurodegenerationEstrés oxidativo; Secuenciación de ARN pequeño; NeurodegeneraciónEstrès oxidatiu; Seqüenciació d'ARN petit; NeurodegeneracióSmall non-coding RNAs (sncRNAs), including microRNAs (miRNAs) are important post-transcriptional gene expression regulators relevant in physiological and pathological processes. Here, we combined a high-throughput functional screening (HTFS) platform with a library of antisense oligonucleotides (ASOs) to systematically identify sncRNAs that affect neuronal cell survival in basal conditions and in response to oxidative stress (OS), a major hallmark in neurodegenerative diseases. We considered hits commonly detected by two statistical methods in three biological replicates. Forty-seven ASOs targeting miRNAs (miRNA-ASOs) consistently decreased cell viability under basal conditions. A total of 60 miRNA-ASOs worsened cell viability impairment mediated by OS, with 36.6% commonly affecting cell viability under basal conditions. In addition, 40 miRNA-ASOs significantly protected neuronal cells from OS. In agreement with cell viability impairment, damaging miRNA-ASOs specifically induced increased free radical biogenesis. miRNAs targeted by the detrimental ASOs are enriched in the fraction of miRNAs downregulated by OS, suggesting that the miRNA expression pattern after OS contributes to neuronal damage. The present HTFS highlighted potentially druggable sncRNAs. However, future studies are needed to define the pathways by which the identified ASOs regulate cell survival and OS response and to explore the potential of translating the current findings into clinical applications.This work was supported by the Spanish Ministry of Economy and Competitiveness and FEDER funds (SAF2014-60551-R and SAF2017-88452-R). We acknowledge the support of the Spanish Ministry of Economy, Industry and Competitiveness (MEIC) to the EMBL partnership and the Centro de Excelencia Severo Ochoa 2013-2017 (SEV-2012-0208). We acknowledge the support of the Spanish Ministry of Science Innovation and Universities, Maria Maeztu Unit of Excellence Programme. We thank the staff of the Genomics Unit for the preparation of sRNA libraries and sequencing and the staff of the Biomolecular Screening and Protein Technologies Unit for their help in the setting up the high-throughput screening

Targeting CAG repeat RNAs reduces Huntington's disease phenotype independently of huntingtin levels.

Huntington's disease (HD) is a polyglutamine disorder caused by a CAG expansion in the Huntingtin (HTT) gene exon 1. This expansion encodes a mutant protein whose abnormal function is traditionally associated with HD pathogenesis; however, recent evidence has also linked HD pathogenesis to RNA stable hairpins formed by the mutant HTT expansion. Here, we have shown that a locked nucleic acid-modified antisense oligonucleotide complementary to the CAG repeat (LNA-CTG) preferentially binds to mutant HTT without affecting HTT mRNA or protein levels. LNA-CTGs produced rapid and sustained improvement of motor deficits in an R6/2 mouse HD model that was paralleled by persistent binding of LNA-CTG to the expanded HTT exon 1 transgene. Motor improvement was accompanied by a pronounced recovery in the levels of several striatal neuronal markers severely impaired in R6/2 mice. Furthermore, in R6/2 mice, LNA-CTG blocked several pathogenic mechanisms caused by expanded CAG RNA, including small RNA toxicity and decreased Rn45s expression levels. These results suggest that LNA-CTGs promote neuroprotection by blocking the detrimental activity of CAG repeats within HTT mRNA. The present data emphasize the relevance of expanded CAG RNA to HD pathogenesis, indicate that inhibition of HTT expression is not required to reverse motor deficits, and further suggest a therapeutic potential for LNA-CTG in polyglutamine disorders.This work was supported by the Spanish government through the Plan Nacional de I+D+I and cofunded by grants from the Instituto de Salud Carlos III (ISCIII) – Subdirección General de Evaluación and the Fondo Europeo de Desarrollo Regional (FEDER) (project PI11/02036, to EM, and PI13/01250, to EPN); the Spanish Ministerio de Economía y Competitividad (MINECO) (SAF2008-00357 and SAF2013-49108-R, to XE, and SAF2014-60551-R: iRPaD, to EM); and the Generalitat de Catalunya, Departament Economia i Coneixement, Secretaria Universitats i Recerca (AGAUR 2014 SGR-1138, to XE)

Targeting CAG repeat RNAs reduces Huntington's disease phenotype independently of huntingtin levels.

Huntington's disease (HD) is a polyglutamine disorder caused by a CAG expansion in the Huntingtin (HTT) gene exon 1. This expansion encodes a mutant protein whose abnormal function is traditionally associated with HD pathogenesis; however, recent evidence has also linked HD pathogenesis to RNA stable hairpins formed by the mutant HTT expansion. Here, we have shown that a locked nucleic acid-modified antisense oligonucleotide complementary to the CAG repeat (LNA-CTG) preferentially binds to mutant HTT without affecting HTT mRNA or protein levels. LNA-CTGs produced rapid and sustained improvement of motor deficits in an R6/2 mouse HD model that was paralleled by persistent binding of LNA-CTG to the expanded HTT exon 1 transgene. Motor improvement was accompanied by a pronounced recovery in the levels of several striatal neuronal markers severely impaired in R6/2 mice. Furthermore, in R6/2 mice, LNA-CTG blocked several pathogenic mechanisms caused by expanded CAG RNA, including small RNA toxicity and decreased Rn45s expression levels. These results suggest that LNA-CTGs promote neuroprotection by blocking the detrimental activity of CAG repeats within HTT mRNA. The present data emphasize the relevance of expanded CAG RNA to HD pathogenesis, indicate that inhibition of HTT expression is not required to reverse motor deficits, and further suggest a therapeutic potential for LNA-CTG in polyglutamine disorders.This work was supported by the Spanish government through the Plan Nacional de I+D+I and cofunded by grants from the Instituto de Salud Carlos III (ISCIII) – Subdirección General de Evaluación and the Fondo Europeo de Desarrollo Regional (FEDER) (project PI11/02036, to EM, and PI13/01250, to EPN); the Spanish Ministerio de Economía y Competitividad (MINECO) (SAF2008-00357 and SAF2013-49108-R, to XE, and SAF2014-60551-R: iRPaD, to EM); and the Generalitat de Catalunya, Departament Economia i Coneixement, Secretaria Universitats i Recerca (AGAUR 2014 SGR-1138, to XE)