Abstract Body: Introduction: Spinal and Bulbar Muscular Atrophy (SBMA), also known as Kennedy’s Disease, is a polyglutamine (polyQ) expansion disorder caused by mutations in the androgen receptor (AR) gene. While the normal AR contains approximately 23 polyQ repeats, SBMA patients exhibit expansions exceeding 35 repeats. Primarily recognized as a neuromuscular disorder, SBMA is also linked to cardiac abnormalities, including Long QT syndrome, hypertrophic cardiomyopathy, and cardiac fibrosis. However, the molecular mechanisms underlying SBMA-related cardiac dysfunction remain unclear. This study modeled SBMA-related cardiac dysfunction using patient-derived human induced pluripotent stem cells (hiPSCs) and analyzed polyQ expanded AR transcriptional regulation in cardiomyocytes.
Hypothesis: PolyQ-expanded AR in SBMA may dysregulate transcriptional activity in cardiomyocytes, contributing to cardiac dysfunction.
Methods: hiPSCs derived from three SBMA patients (53, 53, and 56 polyQ repeats) were obtained from NINDS, and isogenic control hiPSCs were generated by correcting expansions to 23 repeats via CRISPR-Cas9. All hiPSCs were differentiated into cardiomyocytes (iPSC-CMs) under chemically defined conditions. Cells were treated with 30 nM dihydrotestosterone (DHT) or vehicle (EtOH) for two weeks to activate AR. Bulk RNA-seq analyzed transcriptional alterations between SBMA and isogenic control iPSC-CMs.
Results: The isogenic control iPSCs were successfully generated with targeted gene correction and rescue in normal size AR protein expression in iPSC-CM. RNA-seq identified 300 differentially expressed genes with DHT and 382 genes with vehicle. Gene ontology (GO) analysis indicated significant changes in pathways related to cardiac muscle development, heart contraction, sarcomere organization, and calcium signaling pathways. Several hypertrophy-related genes (e.g., LAMA4, CASQ2, NRAP), cardiac fibrosis-associated genes (e.g., CAV3, NPPB, ACKR3), and DCM-associated genes (e.g., SCN5A, SLC6A4, COL23A1) were differentially expressed in SBMA iPSC-CMs.
Conclusions: Transcriptomic analysis revealed enrichment of cardiac dysfunction-associated genes in SBMA iPSC-CMs. PolyQ-expanded AR alters transcriptional regulation, potentially contributing to SBMA-related cardiomyopathy. Further studies will focus on cardiac functional analysis and AR transcriptional dysregulation using CUT&RUN-seq.