The chick embryo late primitive streak and head process studied by scanning electron microscopy

Area of Science:

• Developmental biology
• Embryology
• Cell biology

Background:

• Understanding early embryonic development is crucial for regenerative medicine and developmental disorders.
• The formation of the head process and regression of Hensen's node are key events in avian embryogenesis.

Purpose of the Study:

• To investigate dynamic cell shape alterations during chick embryo head process formation and Hensen's node regression.
• To characterize morphological changes in the mesoderm and notochord during specific developmental stages.

Main Methods:

• Scanning electron microscopy (SEM) was employed to visualize surface morphology.
• Chick embryos at stages -5 to -8 were cultured (New culture) with endoderm removal for ventral mesoderm viewing.
• Detailed observation of cell flattening, process loss, notochord differentiation, and sheath formation was performed.

Main Results:

• Primitive streak shortening correlated with mesodermal cell flattening and loss of flap-like processes.
• Notochord cells underwent transverse orientation followed by axial realignment between stages 6 and -8.
• A cleft formed between the notochord and head mesoderm, accompanied by extracellular fibril deposition indicating sheath formation.

Conclusions:

• SEM provides high-resolution insights into dynamic cell shape changes during early chick embryogenesis.
• Specific cellular rearrangements and extracellular matrix deposition are critical for notochord development and structural integrity.