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Protochordate Zic genes define primitive somite compartments and highlight molecular changes underlying neural crest
Neil J Gostling1, Sebastian M Shimeld
1School of Animal and Microbial Sciences, University of Reading, P.O. Box 228, Whiteknights, Reading RG6 6AJ, United Kingdom.
Evolution & Development
|March 8, 2003
Summary
The Zic gene family, crucial for neural crest development in vertebrates, shows ancient origins in invertebrates. Its expression patterns reveal insights into the evolution of segmented mesoderm and neural crest formation in chordates.
Area of Science:
- Developmental Biology
- Evolutionary Biology
- Genetics
Background:
- The Zic gene family encodes C2H2 zinc finger transcription factors, homologous to Gli proteins, and plays a key role in vertebrate embryonic development, particularly in neural crest induction.
- Zic genes are expressed in various embryonic tissues, including the dorsal neural tube, where they function as potent neural crest inducers.
Purpose of the Study:
- To characterize a Zic ortholog in amphioxus (Branchiostoma floridae) and describe the expression of a Zic ortholog in the ascidian Ciona intestinalis.
- To investigate the evolutionary history of the Zic gene family and its role in the development of chordate features.
Main Methods:
- Molecular phylogenetic analysis and sequence comparisons of Zic genes across different species.
- Detailed analysis of Zic gene expression patterns during embryonic development in Ciona intestinalis and Branchiostoma floridae using in situ hybridization techniques.
Main Results:
- Phylogenetic analysis indicates that gene duplications forming the vertebrate Zic family are specific to the vertebrate lineage.
- CiZic transcripts show maternal localization and zygotic expression in the neural plate of Ciona intestinalis.
- AmphiZic expression is observed in dorsal mesoderm and ectoderm during gastrulation, with dynamic changes during neurulation and post-neurulation stages in amphioxus.
- Comparison of Zic expression patterns in amphioxus, ascidian, and vertebrates allowed for the definition of homologous compartments in somites and identified neural Zic expression as a chordate synapomorphy.
Conclusions:
- The evolution of a dorsal neural expression domain of Zic genes in vertebrate neurulae was a significant step in the evolution of the neural crest.
- Zic gene expression patterns provide insights into the primitive subdivision of vertebrate segmented mesoderm and the evolutionary diversification of neural expression within chordates.