Comparative studies on mammalian Hoxc8 early enhancer sequence reveal a baleen whale-specific deletion of a cis-acting element.
Variations in regulatory regions of developmental control genes have been implicated in the divergence of axial morphologies. To find potentially significant changes in cis-regulatory regions, we compared nucleotide sequences and activities of mammalian Hoxc8 early enhancers. The nucleotide sequence of the early enhancer region is extremely conserved among mammalian clades, with five previously described cis-acting elements, A-E, being invariant. However, a 4-bp deletion within element C of the Hoxc8 early enhancer sequence is observed in baleen whales. When assayed in transgenic mouse embryos, a baleen whale enhancer (unlike other mammalian enhancers) directs expression of the reporter gene to more posterior regions of the neural tube but fails to direct expression to posterior mesoderm. We suggest that regulation of Hoxc8 in baleen whales differs from other mammalian species and may be associated with variation in axial morphology.
Shashikant
C S
CS
Department of Molecular, Cellular, and Developmental Biology, P.O. Box 208103, New Haven, CT 06520, USA. shashi@minerva.cis.yale.edu
Kim
C B
CB
Borbély
M A
MA
Wang
W C
WC
Ruddle
F H
FH
D000818:Animals; D001483:Base Sequence; D005314:Embryonic and Fetal Development; D004742:Enhancer Elements, Genetic; D019143:Evolution, Molecular; D018507:Gene Expression Regulation, Developmental; D018398:Homeodomain Proteins / Q000235:genetics*; D006801:Humans; D008322:Mammals / Q000145:classification / Q000235:genetics*; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D008969:Molecular Sequence Data; D016133:Polymerase Chain Reaction; D017384:Sequence Deletion; D014907:Whales; D001616:beta-Galactosidase / Q000235:genetics
D018398:Homeodomain Proteins; C105702:SpHox8 protein, Strongylocentrotus purpuratus; D001616:beta-Galactosidase