Regionalized tissue fluidization is required for epithelial gap closure during insect gastrulation.

Area of Science:

• Developmental Biology
• Cell Biology
• Biophysics

Background:

• Animal embryos undergo epiboly, a gastrulation process involving epithelial sheet closure around the egg.
• The ellipsoidal egg shape necessitates epithelial expansion followed by compaction, creating mechanical stress.
• Releasing mechanical stress is crucial for successful epithelial sheet closure.

Purpose of the Study:

• To investigate the cellular and mechanical mechanisms driving epithelial sheet closure during epiboly.
• To understand how the extraembryonic tissue (serosa) spreads and seals the embryonic surface.
• To identify conserved morphogenetic modules involved in epithelial gap closure.

Main Methods:

• Utilized the insect Tribolium castaneum as a model organism.
• Observed and analyzed cell behavior and tissue dynamics during serosa epiboly.
• Investigated the role of the actomyosin cable in regulating cell intercalation and tissue fluidity.

Main Results:

• The serosa regionalizes into a solid-like dorsal region and a fluid-like ventral region at the leading edge.
• Smaller cells at the ventral leading edge undergo intercalation.
• A heterogeneous actomyosin cable drives cell eviction and intercalation, fluidizing the leading edge.

Conclusions:

• Actomyosin cable-driven tissue fluidization is a key mechanism for epithelial gap closure during epiboly.
• This process shares similarities with wound healing mechanisms.
• Local tissue fluidization represents a conserved morphogenetic module in epithelial closure.