Meeting Abstract
The vertebrate body is metameric, each species having a characteristic number of segments. As repeating units are generated through segmentation processes, their identity is bestowed through patterning processes. Segmentation is regulated by dynamic morphogen gradients coupled to a molecular oscillator, the ‘clock and wavefront’ model postulated in 1976 by Cooke and Zeeman. Patterning, on the other hand, is regulated by processes that sequentially, in a 3’ to 5’ direction, activate hox gene transcription. The processes coordinating segmentation and hox gene transcription are poorly understood. We have investigated the role of a gene involved in patterning during the process of somitogenesis, the transcription factor Cdx4. Despite of the fact that Cdx4 deficient embryos have defective somite morphology, its function in somitogenesis has not been established. Our preliminary studies suggest that Cdx4 is important for somite formation through the regulation of the ‘wavefront’ or morphogen gradient, but not the period of the segmentation clock. Loss of wavefront regulation leads to changes in somite size and an overall reduction in embryonic axis length, without affecting the total number of segments. Thus, Cdx4 could potentially be the link regulating somite formation and somite identity. Cdx4’s dual role in segmentation and patterning could prove important for understanding the evolutionary diversity of axis length in animals across various phyla.
