SCRMC Seminar: Eileen Lynch

Topic: In vitro modeling of skeletal muscle pathology using ALS patient iPSCs

Abstract: Amyotrophic lateral sclerosis (ALS) is a late-onset neuromuscular disease with no cure and limited treatment options. Patients experience a gradual paralysis leading to death from respiratory complications on average only 2-5 years after diagnosis. There is increasing evidence that skeletal muscle is affected early in the disease process, yet the pathological processes occurring in the skeletal muscle of ALS patients are still mostly unknown. Specifically, the most common genetic cause of ALS, a hexanucleotide repeat expansion in the C9ORF72 gene, has yet to be fully characterized in the context of skeletal muscle. The objective of this study was to determine if skeletal myocytes experience specific pathological changes due to the C9ORF72 mutation. We used the protocol previously developed in our lab to differentiate skeletal myocytes from induced pluripotent stem cells (iPSCs) of C9ORF72 ALS (C9-ALS) patients and examined them for signs of the three proposed mechanisms of the C9ORF72 mutation which include haploinsufficiency, repeat RNA foci, and dipeptide repeat (DPR) proteins.

Of the three C9ORF72 mutation hallmarks, we did not see any evidence of haploinsufficiency, but we did detect RNA foci and DPR protein aggregates. Additional abnormalities included changes in the expression of mitochondrial genes and a susceptibility to oxidative stress, indicating that mitochondrial dysfunction may be a critical feature of C9-ALS skeletal muscle pathology. Finally, the C9-ALS myocytes had increased expression and aggregation of TDP-43. Together, these data support the hypothesis that skeletal muscle cells experience pathological changes due to the C9ORF72 mutation. Our in vitro model could facilitate further study of cellular and molecular pathology in ALS skeletal muscle in order to discover new therapeutic targets against this devastating disease.

Information taken from https://stemcells.wisc.edu/event/tba-2019-03-12/