MYOD1 L122R mutation drives a neuronal-associated transcriptional rewiring through alternative MYC binding in in vitro models of spindle cell rhabdomyosarcoma

ABSTRACT: The L122R MYOD1 activating mutation drives the pathogenesis of spindle cell rhabdomyosarcoma (SRMS), an aggressive pediatric and young adult soft tissue tumor. While wild-type MYOD1 is a master regulator of myogenic-specific genes, the mechanisms by which the L122R mutation shifts cells from differentiation toward proliferation remain incompletely understood. We generate complementary preclinical models of the oncogenic MYOD1 mutation in human embryonic stem (hES) cells and hES-derived progenitors (mesenchymal, skeletal muscle precursors) to evaluate its impact on myogenic differentiation and transcriptional reprogramming. Compared to the wild-type isoform, the expression of the MYOD1 L122R mutation, either ectopically by an inducible transposon system or targeted by CRISPR-Cas9 at the endogenous locus, does not induce the expression of key myogenic genes in differentiating skeletal muscle precursors (hES-SMP) cells. ChIP-seq analysis revealed that approximately 70% of shared binding peaks contained the canonical E-box motif (CAGCTG), indicating that the mutant MYOD1 L122R retains the ability to bind myogenic promoters but does not activate their transcription. Notably, the mutant preferentially binds to MYC E-box motifs at promoter regions of upregulated genes involved in synaptic and neuronal regulation. Moreover, a neuronal-associated transcriptional signature was detected in SRMS tumors, at both bulk and single-cell RNA-seq levels. However, despite the association of MYOD1 L122R with MYC-binding motifs, canonical MYC target genes were not overtly activated, a finding also confirmed in SRMS tumors. Overall, these findings highlight the role of MYOD1 L122R mutation in inhibiting skeletal muscle differentiation and rewiring to a neuronal-associated transcriptional network through alternative binding to MYC-responsive genes.

ORGANISM(S): Homo sapiens

PROVIDER: GSE354182 | GEO | 2026/11/13

REPOSITORIES: GEO