Deletion of a HoxD enhancer induces transcriptional heterochrony leading to transposition of the sacrum.
A phylogenetically conserved transcriptional enhancer necessary for the activation of Hoxd-11 was deleted from the HoxD complex of mice by targeted mutagenesis. While genetic and expression analyses demonstrated the role of this regulatory element in the activation of Hoxd-11 during early somitogenesis, the function of this gene in developing limbs and the urogenital system was not affected, suggesting that Hox transcriptional controls are different in different axial structures. In the trunk of mutant embryos, transcriptional activation of Hoxd-11 and Hoxd-10 was severely delayed, but subsequently resumed with appropriate spatial distributions. The resulting caudal transposition of the sacrum indicates that proper vertebral specification requires a precise temporal control of Hox gene expression, in addition to spatial regulation. A slight time delay in expression (transcriptional heterochrony) cannot be compensated for at a later developmental stage, eventually leading to morphological alterations.
Pubmed ID: 9250683 RIS Download
Animals | Cell Line | Enhancer Elements, Genetic | Forelimb | Gene Expression Regulation, Developmental | Genes, Homeobox | Homeodomain Proteins | In Situ Hybridization | Mice | Mice, Transgenic | Mutagenesis, Insertional | Sacrum | Sequence Deletion | Transcription Factors | Transcription, Genetic