Date of Award


Document Type


Degree Name

Bachelor of Science


Biochemistry & Molecular Biol.

First Advisor

Isaac Skromne


The Caudal Type Homeobox transcription factors cdx are a family of genes found in vertebrates that regulates body regionalization and anterior-posterior patterning. They are also responsible for regulating axial elongation, but the mechanisms behind this behavior are not known. Previous studies in mouse embryonic stem cells have shown that the cdx genes are necessary for upregulating the gene sp5 which may be linked to axial elongation. Sp5 is a zinc-finger transcription factor belonging to the specificity protein (sp) family. Our group has used in-situ hybridization experiments on zebrafish embryos to show that sp5-like (sp5l) is transcribed within tailbud tissues that develop into paraxial mesoderm and ultimately give rise to the somites. We also found that sp5l expression in the tailbud and paraxial mesoderm is diminished when cdx4 or the signaling factor Wnt is inhibited. Lastly, we found that inhibiting Wnt and upregulating cdx4 can rescue sp5l expression. Additionally, using CRISPR gene editing we found that sp5l knockouts in zebrafish cause distortions in the somites and deformations in the tail and spinal column. Together, our results show that sp5l regulation by Wnt signaling is mediated by cdx4, and that this regulation is necessary for tailbud posteriorization and somitogenesis. These results shed new light on the mechanisms of axial elongation.