Do vertebrate neural crest and cranial placodes have a common evolutionary origin?

Area of Science:

• Developmental biology
• Evolutionary developmental biology
• Head development

Background:

• The vertebrate head's evolutionary novelties arise from neural crest and cranial placodes.
• Both tissues share similarities in origin, cell migration, and fate, suggesting a common evolutionary origin.
• However, fundamental developmental differences exist between neural crest and placodes.

Purpose of the Study:

• To investigate the evolutionary origin of the neural crest and cranial placodes.
• To compare developmental mechanisms of neural crest and placodes.
• To reconcile similarities with differences in their origins.

Main Methods:

• Comparative analysis of developmental mechanisms.
• Review of existing literature on neural crest and placode induction, specification, migration, and cytodifferentiation.
• Incorporation of data from tunicates and amphioxus.

Main Results:

• Despite developmental similarities, fundamental differences in induction, specification, migration, and differentiation exist between neural crest and placodes.
• Insights from tunicates and amphioxus highlight distinct origins.
• Neural crest and placodes likely evolved independently.

Conclusions:

• Neural crest and placodes possess independent evolutionary origins.
• They likely evolved from distinct regions of the neural plate border: neural and non-neural sides, respectively.
• This clarifies the evolution of vertebrate head structures.