Somite pattern regulation in the avian segmental plate mesoderm

Area of Science:

• Developmental Biology
• Embryology
• Regenerative Medicine

Background:

• The avian segmental pattern, formed by somites, is thought to be specified early in the paraxial mesoderm.
• This pattern is known to be modifiable and capable of reconstitution after disruption.

Purpose of the Study:

• To investigate the capacity of avian embryos to alter the specified segmental pattern.
• To examine the ability of embryos to restore the segmental pattern after experimental disruption.

Main Methods:

• Experimental manipulation of paraxial (segmental plate) mesoderm in chicken and Japanese quail embryos.
• Grafting of segmental plates between species and analysis of somite formation.
• Halting further development by removing Hensen's node and primitive streak.
• Orthostereoscopic reconstructions for detailed analysis of somite development.

Main Results:

• Control experiments showed high correlation in somite numbers between operated and unoperated sides, indicating pattern stability.
• Cross-species grafts demonstrated that the host embryo significantly influences the graft's somite number to match the host's pattern.
• Grafted and minced paraxial mesoderm required proximity to the midline for successful somite formation.

Conclusions:

• The host avian embryo actively regulates and modifies the segmental pattern specified in the paraxial mesoderm.
• This regulation extends to adjusting somite number, location, and size to achieve pattern compatibility.
• The paraxial mesoderm exhibits remarkable plasticity and regenerative capacity during early embryonic development.