An amphioxus Krox gene: insights into vertebrate hindbrain evolution.
The transcription factor Krox-20 has roles in the maintenance of segmentation and specification of segment identity in the vertebrate hindbrain. Overt hindbrain segmentation is a vertebrate novelty, and is not seen in invertebrate chordates such as amphioxus and tunicates. To test if the roles of Krox-20 are also derived, we cloned a Krox-20 related gene, AmphiKrox, from amphioxus. AmphiKrox is related to a small family of vertebrate Krox genes and is expressed in the most anterior region of the amphioxus brain and in the club shaped gland, a secretory organ that develops in the anterior pharynx. Neither expression domain overlaps with the expression of AmphiHox-1, -2, -3 or -4, suggesting that the roles of Krox-20 in hindbrain segmentation and in Hox gene regulation were acquired concomitant with the duplication of Krox genes in vertebrate evolution.
Knight
R D
RD
School of Animal and Microbial Sciences, University of Reading, Whiteknights, PO Box 228, Reading RG6 6AJ, UK.
Panopoulou
G D
GD
Holland
P W
PW
Shimeld
S M
SM
D000595:Amino Acid Sequence; D000818:Animals; D002816:Chordata, Nonvertebrate / Q000235:genetics*; D018076:DNA, Complementary; D004268:DNA-Binding Proteins / Q000737:chemistry / Q000235:genetics*; D051767:Early Growth Response Protein 2; D006801:Humans; D008969:Molecular Sequence Data; D012249:Rhombencephalon / Q000196:embryology*; D017386:Sequence Homology, Amino Acid; D014157:Transcription Factors / Q000737:chemistry / Q000235:genetics*
D018076:DNA, Complementary; D004268:DNA-Binding Proteins; C497326:EGR2 protein, human; D051767:Early Growth Response Protein 2; D014157:Transcription Factors