Developmental Analysis of Genes Regulating Segmentation of Paraxial Mesoderm
Smith, Allanceson; Sewell, Will; and Kusumi, Kenro
School of Life Sciences, Arizona State University
Somites are segmented embryonic structures composed of paraxial mesoderm. Its proper formation is responsible for the development of crucial segmental structures, like vertebrae and axial muscles. Numerous congenial spinal deformations have been identified as a result of disruptions in somite development in both mice and humans. Spondylocostal dysostosis, Klippel Feil syndrome, and congenital scoliosis are some clinical diagnoses associated with somite anomalies in humans. Somites develop through a unique process that is regulated by an internal oscillating mechanism called the segmentation clock. This clock regulates the formation of somites through genes known as cycling genes. Cycling genes have expressions that oscillate posterior-anterior in PSM (presomitic mesoderm), establishing the boundaries of somites. Genes from the Notch, Wnt, and Fgf pathways are significant factors in the segmentation clock mechanism.
There are potentially hundreds of genes that could be cycling or oscillatory genes. Gene candidates have been gathered from microarray expression screens in our laboratory. Mouse gene homologues are being used to create anti-sense RNA probes, for whole mount in situ hybridization analysis of 9.5 day old embryos. In situ hybridization shows gene expression locations, and more importantly determines if the genes are expressed in the precursor tissue. We are documenting the results of our in situ hybridization analysis and comparing gene expression patterns during somite formation. Thus, we aim to identify additional cycling genes.