Combinatorial chromatin dynamics foster accurate cardiopharyngeal fate choices

Area of Science:

• Developmental Biology
• Epigenetics
• Chordate Genomics

Background:

• Chromatin accessibility is crucial for lineage-specific gene expression during embryogenesis.
• The cardiopharyngeal mesoderm gives rise to both heart and pharyngeal/head muscles, but the regulatory mechanisms governing their early fate choices are unclear.

Purpose of the Study:

• To investigate chromatin accessibility landscapes in the cardiopharyngeal mesoderm during muscle progenitor development.
• To identify regulatory pathways and elements controlling cell fate decisions in heart vs. pharyngeal muscle precursors.

Main Methods:

• Utilized the chordate model organism *Ciona* for chromatin accessibility profiling.
• Analyzed transitions from naive mesoderm to fate-restricted muscle precursors.
• Investigated the role of the FGF-Foxf pathway and cis-regulatory elements.

Main Results:

• Identified cardiopharyngeal-specific chromatin accessibility patterns established by an FGF-Foxf pathway in multipotent progenitors.
• Demonstrated spatiotemporal decoupling between early enhancer accessibility and late cell-type-specific gene expression.
• Discovered that multiple cis-regulatory elements with distinct profiles are required for activating key fate determinants like *Ebf* and *Tbx1/10*.

Conclusions:

• The FGF-Foxf pathway and specific chromatin accessibility patterns are critical for directing cardiopharyngeal muscle progenitor fates.
• Combined enhancers integrate regulatory inputs to ensure spatially and temporally accurate cell fate choices.
• This study provides insights into the epigenetic control of developmental decisions in muscle formation.