Modulating MyoD1 dosage activates alternate cell fate beyond myogenic differentiation

Area of Science:

• Molecular Biology
• Developmental Biology
• Genetics

Background:

• Transcription factor (TF) dosage is crucial for cell fate determination during development.
• The impact of TF binding to high-affinity versus low-affinity targets at different dosages is not fully understood.
• MyoD1 is a key regulator of skeletal muscle development (myogenesis).

Purpose of the Study:

• To investigate the role of transcription factor dosage in cell fate decisions.
• To examine how increased MyoD1 dosage affects skeletal muscle differentiation.
• To elucidate the molecular mechanisms underlying altered myogenesis due to TF dosage.

Main Methods:

• Utilized live-cell single-molecule imaging to track TF binding dynamics.
• Employed CUT&RUN and ATAC-seq for genome-wide chromatin accessibility and TF binding analysis.
• Integrated RNA-seq data to correlate TF binding with gene expression changes.

Main Results:

• Elevated MyoD1 dosage unexpectedly inhibited canonical skeletal muscle differentiation.
• Increased MyoD1 dosage led to the upregulation of non-myogenic genes, including cell adhesion genes.
• Higher MyoD1 levels promoted binding to lower-affinity genomic loci, expanding target gene activation.
• This resulted in the formation of spontaneously contracting myotubes, a novel phenotype.

Conclusions:

• Transcription factor dosage can reprogram developmental trajectories by altering gene regulatory networks.
• Increased MyoD1 dosage drives a shift from high- to low-affinity binding sites, activating a broader set of genes.
• This TF dose-dependent mechanism reveals a novel pathway for triggering distinct developmental programs, impacting cell fate decisions.