The vertebrate tail bud: three germ layers from one tissue.

Area of Science:

• Developmental biology
• Embryology
• Cell differentiation

Background:

• The amniote tail bud is a source of undifferentiated mesenchymal cells at the embryo's posterior.
• These cells contribute to various tissues, including the secondary neural tube and somites.
• Tail bud cells can differentiate into tissues typically derived from different germ layers in cranial regions.

Purpose of the Study:

• To review the tissue contributions of the tail bud across vertebrate classes.
• To examine the mesenchymal-to-epithelial transformation during secondary neurulation.
• To discuss the role of cell surface changes, like N-CAM expression, in tail bud development.

Main Methods:

• Review of existing literature on tail bud development in vertebrates.
• Analysis of the mesenchymal-to-epithelial transition in secondary neurulation.
• Discussion of experimental approaches, including ectopic grafting and substrate-dependent cell culture.

Main Results:

• Tail bud mesenchyme exhibits pluripotency, differentiating into myocytes, chondrocytes, neuroepithelium, and neural crest derivatives.
• Secondary neurulation involves a mesenchymal-to-epithelial transformation, distinct from primary neurulation.
• Cell surface oligosaccharide changes and N-CAM expression correlate with differentiation during secondary neurulation.

Conclusions:

• The tail bud mesenchyme is a versatile developmental system.
• It offers a model for studying fundamental mechanisms of cell differentiation and transformation.
• Experimental manipulation of tail bud tissue can yield significant insights into developmental processes.