Does an equivalent of the "ventral node" exist in chick embryos? A scanning electron microscopic study

Area of Science:

• Developmental biology
• Embryology
• Molecular signaling

Background:

• Vertebrate organ asymmetry is species-specific, with origins studied since the 19th century.
• Conserved molecular cascades initiate left-right (L-R) patterning from Hensen's node.
• The initial trigger for these cascades remains unknown.

Purpose of the Study:

• To investigate the presence and location of monociliated cells in early chick embryos.
• To determine if an avian equivalent of the mouse ventral node exists.
• To assess the role of nodal cilia in initiating L-R patterning in chicks.

Main Methods:

• Microscopic examination of early chick embryo endoderm and epiblast.
• Focus on identifying monociliated cells, particularly around Hensen's node.

Main Results:

• Monociliated cells were found in the chick endoderm but not exclusively at Hensen's node.
• In the epiblast, monociliated cells were peripheral, with only a small subpopulation at Hensen's node.
• No evidence of a ventral node-like structure at Hensen's node in chick embryos.

Conclusions:

• An equivalent of the mouse ventral node is unlikely to exist in early chick embryos.
• Nodal cilia in chick embryos probably do not initiate L-R patterning.
• Further research is needed to understand the initiation of L-R asymmetry in avian development.