Transcriptomic analysis of Cr(VI)-induced changes in C2C12 cells during myogenic differentiation

Hexavalent chromium [Cr(VI)] is an environmental toxicant extensively used in a variety of industrial processes including chrome plating, leather tanning, textile manufacturing, aircraft production, and stainless-steel production. Our previous study showed that exposure to Cr(VI) impaired C2C12 myogenic differentiation in a dose-dependent manner, yet the transcriptional mechanisms underlying Cr(VI)-induced disruption of myogenesis remains poorly understood. Here, we performed bulk RNA-sequencing on C2C12 myoblasts undergoing differentiation in the presence of 0, 2, or 5 µM of Cr(VI). Differential gene expression analysis demonstrated a dose- and time-dependent increase in transcriptional dysregulation. Fuzzy c-means clustering identified 12 distinct gene expression patterns, with Clusters 3, 10, and 12 showing significant overlap with Cr(VI)-regulated genes. Functional enrichment analyses revealed Cr(VI) disrupts genes involved in early-stage cell cycle regulation and DNA repair as well as terminal differentiation processes like sarcomere organization and muscle contraction. Specifically, Cr(VI) impaired expression of key structural and contractile genes and disrupted DNA repair and cell cycle regulatory pathways, including downregulation of p21 and upregulation of proliferative marker PCNA. Furthermore, we identified suppression of Hippo signaling through downregulation of Tead4 and its muscle-specific downstream targets, providing a mechanism for impaired differentiation. These findings highlight widespread alterations in transcriptional programs governing muscle development and maturation, offering insight into how Cr(VI) exposure affects skeletal muscle health.