Authors: Shawn Luttrell PhD, Daniel Lih MS, Christos Michas PhD
Featuring: iPSC-derived DM1 Skeletal Muscle Myoblasts | Mantarray Platform | Nautilai Platform
Figure 1. Nuclear foci present in DM1 iPSC-derived myoblasts. (A) Representative images showing RNA-FISH of foci (red) co-stained with DAPI (blue) in CRISPR-corrected control and DM1-derived myoblasts. (B) Quantification of foci (from A), represented as average number of foci per nuclei.
Myotonic Dystrophy Type 1 (DM1) is the most prevalent adult-onset muscular dystrophy and one of the best-characterized genetic disorders[1, 2], with a well-defined etiology linked to expanded CTG trinucleotide repeats in the DMPK gene[3]. This mutation leads to toxic RNA foci that disrupt RNA splicing, causing widespread cellular dysfunction and progressive muscle weakness[4]. Despite DM1’s clear genetic basis and its strong potential for gene therapy interventions, no effective treatments exist. A key challenge in therapy development is the inability of existing preclinical models to replicate the functional in vivo phenotypes of DM1, limiting clinical translatability. To address this gap, we present a human iPSC-derived engineered muscle tissue (EMT) platform that models the functional consequences of CTG repeat expansions on muscle biology. We demonstrate that muscle contractility inversely correlates with repeat length as is seen in vivo[5, 6], with severe mutations leading to reduced strength and impaired calcium handling. This EMT model provides a physiologically relevant in vitro system for studying DM1 pathophysiology and screening candidate therapeutics to improve translatability.
Two iPSC-derived DM1 patient lines harboring 473 and 716 CTG repeats (DM1-473 and DM1-716, respectively) were used to assess the impact of repeat length on muscle function. An isogenic CRISPR-corrected control for DM1-716 was generated and validated to contain zero CTG repeats using whole genome sequencing. All three lines were differentiated into skeletal muscle myoblasts and assessed for purity (% desmin+), population doubling times, and 2D fusion, with no discernible differences observed between the three lines. A non-related wild-type line (24-WT) was included for internal comparison. Enriched myoblasts were combined with 10% fibroblasts in a fibrin-based hydrogel to generate 3D EMTs. Contractile force was measured over 46 days on the Mantarray platform (n = 4 tissues averaged per data point), revealing an inverse correlation between CTG repeat length (0, 473 and 716) and muscle function. Calcium flux, measured on the Curi Bio Nautilai platform, showed altered calcium handling in DM1-716 tissues, with prolonged rise and decay times compared to isogenic controls.
Figure 2. CRISPR-mediated correction provides recovery of function. (A) DMPK CTG repeat length (0, 473, and 716) demonstrated an inverse correlation with contractile force output as measured on Mantarray. n = 4 tissues per data point. (B) Calcium flux was measured in low calcium Tyrode’s solution on the Curi Bio Nautilai platform. Cal-520 fluorescence transient rise and decay times were significantly longer in disease EMTs compared to CRISPR corrected isogenic controls. n = 3 tissues per data point.
For life science research only. Not for use in diagnostic procedures.