Stable developmental patterns of gene expression without morphogen gradients

Area of Science:

• Developmental biology
• Systems biology
• Computational biology

Background:

• Gene expression patterns in developing organisms are initially driven by morphogen gradients.
• As development progresses, morphogen activity decreases, risking pattern instability due to cellular noise.
• Despite this, gene expression patterns often remain stable over long developmental periods.

Purpose of the Study:

• To investigate how spatiotemporal integrity of gene expression patterns is maintained in developing tissues lacking morphogen gradients.
• To understand the mechanisms underlying pattern stability in the absence of continuous positional cues.

Main Methods:

• Spatial-stochastic simulations of a minimal embryo model.
• Application of Non-Stationary Forward Flux Sampling (NFFS) for enhanced sampling.
• Utilizing a recently developed stability theory for analysis.
• Analysis of a reduced phase space using pattern asymmetry measures.

Main Results:

• Tuning weak cross-repressive interactions to an optimal level significantly prolongs pattern stability.
• Stable gene expression patterns can be maintained over developmentally relevant timescales without morphogen gradients.
• Simulations identified an optimal parameter regime that aligns with stability theory predictions.
• Restoring forces in the optimal regime protect patterns, creating a metastable basin.

Conclusions:

• Metastable attractors can emerge in stochastic gene expression patterns without global positional cues.
• Optimal tuning of gene regulatory interactions is crucial for maintaining pattern integrity.
• This mechanism provides a framework for understanding pattern stability in early development.