Chick amniogenesis is mediated by an actin cable

Area of Science:

• Developmental Biology
• Cell Biology
• Embryology

Background:

• The actin cable mechanism is known to be involved in amnion wound repair.
• The role of this mechanism during embryonic development, specifically amniogenesis, is not well understood.

Purpose of the Study:

• To investigate if the actin cable mechanism in amnion wound repair is a recapitulation of developmental events during chick amniogenesis.
• To elucidate the cellular and molecular processes underlying chick amnion closure.

Main Methods:

• Fluorescein isothiocyanate-labeled phalloidin staining to visualize actin cables in the developing chick amnion.
• Transmission electron microscopy (TEM) to examine the ultrastructure of cells at the leading edge and fusion point of the amnion.
• Inhibition of Rho signaling using cell-permeable C3 transferase to assess its impact on amniogenesis.

Main Results:

• An actin cable was identified in the amniotic head fold, persisting until amnion closure.
• TEM revealed linearly arranged actin microfilaments in elongated leading-edge cells and a mesh of actin filaments within the midline fusion nodule.
• Absence of lamellapodia suggests cell crawling is not the primary mechanism for amniogenesis.
• Inhibition of Rho with C3 transferase impeded amniogenesis in early embryonic stages.

Conclusions:

• The actin cable mechanism observed in amnion wound repair appears to be a recapitulation of developmental events during chick amniogenesis.
• Actin microfilaments and Rho signaling play critical roles in chick amnion closure.
• Amniogenesis likely involves mechanisms other than cell crawling, such as actin cable-mediated cell shape changes.