Fine-tuning mechanical constraints reveals uncoupled patterning and gene expression programs in murine gastruloids

Area of Science:

• Developmental Biology
• Biophysics
• Cell Biology

Background:

• Embryonic development relies on the complex interplay between mechanical forces and genetic programs.
• Understanding how physical cues influence morphogenesis and cell fate decisions is crucial but remains challenging.
• Murine gastruloids offer a 3D in vitro model to study early embryogenesis.

Purpose of the Study:

• To investigate the impact of tunable mechanical environments on murine gastruloid development.
• To determine how hydrogel stiffness and embedding timing affect transcriptional profiles, patterning, and morphology.
• To dissect the relationship between mechanical forces, cell motility, polarization, and gene expression during embryogenesis.

Main Methods:

• Embedding murine gastruloids in bioinert hydrogels with controlled stiffness (<30 Pa to higher stiffness) and timing.
• Utilizing live imaging and cell tracking to monitor gastruloid elongation, polarization, and cell motility.
• Analyzing transcriptional profiles and anteroposterior patterning in response to varying mechanical constraints.

Main Results:

• Ultra-soft hydrogels (<30 Pa) promote robust elongation while preserving patterning and transcription.
• Higher stiffness disrupts gastruloid polarization, but gene expression remains largely unaffected.
• Earlier embedding significantly alters transcriptional profiles independently of polarization defects, uncoupling transcription and patterning.
• Impaired cell motility, identified through live imaging, underlies polarization defects.

Conclusions:

• External mechanical constraints can selectively influence specific developmental processes like patterning, transcription, or morphology.
• Distinct cellular states exhibit differential responses to mechanical cues, highlighting the plasticity of embryonic development.
• Mechanical forces play a critical role in shaping morphogenesis, potentially independent of transcriptional regulation, by affecting cell motility.