Author:
Cheng Yung-Chih,Nocula-Lugowska Gosia,Ramirez Julita A.,Fan Xiaoyu,Jin Fang,Jiang Zhihua,Bennett Eric,Li Jin,Hokanson David,Grandhi Sneha,Chen Michelle,Cheng Congsheng,Lin Guan-Yu,Lin Laura,Lepsy Chris,Chaparro-Riggers Javier,Bloom Laird,Morrissey David,Stewart Morag,Tadin-Strapps Marija,Chiang Shian-Huey
Abstract
ABSTRACTExpansion of repeat sequences within the human genome can lead to disease pathogenesis, such as Huntington’s Disease, primarily affecting the nervous system. Genome-wide association studies (GWAS) of age-at-onset in Huntington’s disease (HD) patients demonstrated DNA mismatch repair (MMR) genes are modifiers of somatic expansion and may be potential therapeutic targets for repeat expansion (RE) disorders. FAN1, a Fanconi anemia-associated nuclease, has been reported as an influencer of repeat expansion in the RE mouse models. Here, we show the first demonstration that FAN1 knock-out in HD patient-derived fibroblasts and results in increased CAG repeat length. We also develop a robust novel cell-based platform using stem cell technology to produce the HD patients’ iPSC-derived astrocytes (iAstro). This platform is a disease-relevant system and has a significantly wider assay window, making it more suitable to assess the effect of gene modulation on CAG repeats. A substantial and exponential increase in repeat instability was exhibited in this HD patient’s iPSC-derived astrocytes platform. Over-expression of FAN1 protein viaFAN1plasmid transfection in this platform reduced CAG repeat instability, suggesting that upregulation of FAN1 protein may have a potential protective effect in CAG repeat expansion for a therapeutic setting. We leveraged the mRNA-LNP modality to enhance FAN1 protein expression and revealed that codon-optimizedFAN1mRNA-LNP robustly prevented increased CAG repeat in HD patients’ iPSC-derived astrocytes platform. The data from these cell-based platforms highlight that FAN1 plays a protective role in attenuating expanded somaticHTTCAG repeats and shed light on new therapeutic directions against repeat expansion disorders.
Publisher
Cold Spring Harbor Laboratory