Patterning of avian craniofacial muscles

Area of Science:

• Developmental biology
• Embryology
• Cell biology

Background:

• Vertebrate voluntary muscles comprise myotubes and connective tissue cells with distinct embryonic origins.
• Myogenic cells originate from paraxial mesoderm, while head connective tissues often derive from neural crest cells.

Purpose of the Study:

• To investigate the interactions between trunk myotomal cells and cephalic neural crest mesenchyme during development.
• To determine if neural crest cells provide spatial patterning information to myogenic cells.

Main Methods:

• Heterotopic transplantation of quail cervical somites into chick host embryos.
• Surgical implantation of somites adjacent to the midbrain before neural crest emigration.
• Histological examination of host embryos (7-12 days incubation) for quail cell presence and differentiation.

Main Results:

• Grafted trunk myotomal cells integrated into host neural crest mesenchyme, forming normal extrinsic ocular and jaw muscles.
• Myogenic cells from the graft formed only the muscle components, with neural crest cells providing the connective tissue framework.
• Grafted paraxial mesoderm interfered with corneal tissue development, and some cells formed ectopic bone near the eye.

Conclusions:

• Neural crest-derived mesenchyme provides essential spatial patterning cues for invading myogenic cells.
• Similar interaction mechanisms between myotomal cells and mesenchyme (neural crest in head, lateral plate in trunk) are suggested.