# MicroRNA profiling in post-mortem spinal cord of C9ORF72-related ALS patients reveals molecular pathways involved in motor neuron degeneration

## TL;DR

This study identifies specific microRNAs linked to motor neuron degeneration in C9ORF72-related ALS, offering potential therapeutic targets.

## Contribution

The study reveals novel miRNA profiles and their associated pathways in C9ORF72-ALS spinal cord tissue.

## Key findings

- miR-200b-3p and miR-346 are uniquely expressed in C9ORF72-ALS patients' spinal cord ventral horn regions.
- Target genes of differentially expressed miRNAs are linked to inflammation, cell death, and protein metabolism.
- Restoring miRNA expression could be a therapeutic strategy for C9ORF72-ALS.

## Abstract

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disorder causing progressive motor neuron death in cortex, brainstem and spinal cord. The most common genetic cause is the G4C2 hexanucleotide repeat expansion in the non-coding region of exon 1 of C9ORF72, accounting for ~40% of familial and ~7% of sporadic ALS. RNA dysregulation is increasingly recognized as a key contributor to ALS pathogenesis. This study aimed to identify specific microRNAs (miRNAs) involved in motor neuron degeneration in C9ORF72-ALS.

We profiled 754 miRNAs in human post-mortem spinal cord tissue from C9ORF72-ALS patients and healthy donors. Laser capture microdissection isolated ventral horn regions, and in silico target prediction identified potential genes and pathways regulated by differentially expressed miRNAs. Target genes were validated by Real time PCR.

Two subsets of miRNAs were exclusively expressed in ventral horn regions: miR-200b-3p and miR-346 in C9ORF72-ALS patients, and miR-30d-5p, miR-106b-5p and miR-135a-5p in healthy donors. Target prediction and molecular analysis identified putative genes and pathways linked to cell death, inflammation, protein metabolism, DNA modification, excitotoxicity, autophagy and vesicles trafficking.

This study identifies specific miRNAs and their target genes as key molecules in motor neuron degeneration in C9ORF72-ALS. Restoring their expression could represent a therapeutic approach for ALS.

Diagram depicting the analysis of human post-mortem brain and spinal cord tissues from healthy donors and C9ORF72-related ALS patients. Motor neuron laser capture, RNA extraction, and miRNA profiling are illustrated. miRNAs and target gene expressions in healthy donors and C9ORF72-ALS patients affect neuroinflammation, DNA modification, motor neuron survival, and other processes. Histological and RNA analyses are shown with images of tissues and confocal microscopy. Potential molecular therapies to counteract motor neuron degeneration are proposed, focusing on various biological processes.