Modification of expression and cis-regulation of Hoxc8 in the evolution of diverged axial morphology.
Differential Hox gene expression between vertebrate species has been implicated in the divergence of axial morphology. To examine this relationship, we have compared expression and transcriptional regulation of Hoxc8 in chicken and mouse. In both species, expression of Hoxc8 in the paraxial mesoderm and neural tube is associated with midthoracic and brachial identities, respectively. During embryogenesis, there is a temporal delay in the activation of Hoxc8 in chicken compared with mouse. As a result, chicken Hoxc8 expression in the paraxial mesoderm is at a posterior axial level, extending over a smaller domain compared with mouse Hoxc8 expression. This finding is consistent with a shorter thoracic region in chicken compared with mouse. In addition, the chicken Hoxc8 early enhancer, differing from its mouse counterpart in only a few specific nucleotides, directs a reporter gene expression to a more posterior domain in transgenic mouse embryos. These findings are consistent with the concept that the diversification of axial morphology has been achieved through changes in cis-regulation of developmental control genes.
Belting
H G
HG
Department of Molecular, Cellular, and Developmental Biology, Yale University, POB 208103, New Haven, CT 06520, USA.
Shashikant
C S
CS
Ruddle
F H
FH
D000818:Animals; D001483:Base Sequence; D005075:Biological Evolution; D019521:Body Patterning / Q000235:genetics*; D002642:Chick Embryo; D002645:Chickens; D004622:Embryo, Mammalian / Q000502:physiology; D004625:Embryo, Nonmammalian; D004627:Embryonic Induction; D004742:Enhancer Elements, Genetic; D018507:Gene Expression Regulation, Developmental; D018398:Homeodomain Proteins / Q000096:biosynthesis* / Q000235:genetics*; D008648:Mesoderm / Q000502:physiology; D051379:Mice; D008822:Mice, Transgenic; D008969:Molecular Sequence Data; D009420:Nervous System / Q000196:embryology; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D013045:Species Specificity
D018398:Homeodomain Proteins; C489816:Hoxc8 protein, mouse