Pluto Bioinformatics

GSE139144: Correction of ALS-related phenotypes in iPSC-derived motor neurons carrying a hexanucleotide expansion mutation in C9orf72 by CRISPR/Cas9 genome editing and homology-directed repair

Bulk RNA sequencing

The G4C2 hexanucleotide repeat expansion (HRE) in C9orf72 is the commonest cause of familial amyotrophic lateral sclerosis (ALS). A number of different methods have been used in an attempt to generate isogenic control lines using CRISPR (clustered regularly interspaced short palindromic repeats)/Cas9 and NHEJ by deleting the repeat region without replacing it with the normal repeat size, but typically this strategy carries the risk of creating indels and genomic instability. In this study we demonstrate complete correction of an induced pluripotent stem cell (iPSC) line derived from a C9orf72-HR positive ALS patient using CRISPR/Cas9 genome editing and homology directed repair (HDR), resulting in replacement of the excised region with a donor template carrying the wild-type repeat size to maintain the genetic architecture of the locus. The isogenic correction of the C9orf72 HRE restored normal expression and methylation at the C9orf72 locus, reduced intron retention in the edited lines, and abolished pathological phenotypes associated with the C9orf72 HRE expansion in iPSC derived motor neurons (iPSMNs). RNA sequencing of the mutant line identified 2220 differentially expressed genes compared to its isogenic control. Enrichment analysis demonstrated an over-representation of ALS relevant pathways in the presence of the C9orf72 HRE, including calcium ion dependent exocytosis, synaptic transport and the KEGG ALS pathway, as well as new targets of potential relevance to ALS pathophysiology.Complete correction of the C9orf72 HRE in iPS MNs by CRISPR/Cas9 mediated HDR provides an ideal model to study the earliest effects of the hexanucleotide expansion on cellular homeostasis and the key pathways implicated in ALS pathophysiology. SOURCE: Kevin Talbot University of Oxford

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