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An amphioxus Krox gene: insights into vertebrate hindbrain evolution.
R D Knight1, G D Panopoulou, P W Holland
1School of Animal and Microbial Sciences, University of Reading, Whiteknights, PO Box 228, Reading RG6 6AJ, UK.
Development Genes and Evolution
|February 17, 2001
Summary
The study cloned AmphiKrox from amphioxus, finding its expression differs from vertebrate Krox-20. This suggests Krox-20
Area of Science:
- Developmental Biology
- Evolutionary Biology
- Genetics
Background:
- Vertebrate hindbrain segmentation is a unique evolutionary development.
- The transcription factor Krox-20 is crucial for vertebrate hindbrain segmentation and segment identity.
- Invertebrate chordates like amphioxus lack overt hindbrain segmentation.
Purpose of the Study:
- To investigate the evolutionary origins of Krox-20's role in hindbrain segmentation.
- To determine if Krox-20 functions in invertebrate chordates are ancestral or derived.
Main Methods:
- Cloning of a Krox-20 related gene, AmphiKrox, from amphioxus.
- Analysis of AmphiKrox gene expression patterns in amphioxus.
- Comparison of AmphiKrox expression with amphioxus Hox genes (AmphiHox-1, -2, -3, -4).
Main Results:
- AmphiKrox is expressed in the anterior brain and club-shaped gland of amphioxus.
- AmphiKrox expression domains do not overlap with AmphiHox genes.
- AmphiKrox shows a distinct expression pattern compared to vertebrate Krox-20 in the hindbrain.
Conclusions:
- The specific roles of Krox-20 in hindbrain segmentation and Hox gene regulation appear to be vertebrate innovations.
- These functions likely arose following the duplication of Krox genes during vertebrate evolution.
- AmphiKrox's expression pattern suggests a different ancestral role for Krox genes before vertebrate radiation.