Epigenetics decouples mutational from environmental robustness. Did it also facilitate multicellularity?

Area of Science:

• Evolutionary biology
• Systems biology
• Developmental biology

Background:

• Multicellularity requires cell differentiation, which involves sensitivity to environmental cues.
• Gene regulatory network models show a correlation between robustness to mutations and environmental robustness.
• This correlation presents a barrier to the evolution of multicellularity.

Purpose of the Study:

• To investigate how the barrier between mutational robustness and environmental sensitivity can be overcome.
• To model the role of epigenetic mechanisms, specifically Polycomb Group Proteins, in facilitating multicellularity.

Main Methods:

• Utilized a gene regulatory network model incorporating epigenetic control via Polycomb Group Proteins.
• Simulated histone modification mechanisms to analyze network dynamics.
• Assessed the system's capacity for producing novel output states under altered conditions.

Main Results:

• The Polycomb mechanism successfully decoupled mutational and environmental robustness.
• The system became simultaneously robust to mutations and sensitive to environmental cues.
• This decoupling facilitated cell differentiation, enabling the generation of new states.

Conclusions:

• The Polycomb mechanism is a key innovation enabling the evolution of multicellularity.
• It dynamically reshapes gene regulatory networks during development.
• This epigenetic mechanism overcomes a fundamental barrier in evolutionary transitions.