The digestive tract of vertebrates is a complicated organ system that is essential for the digestion of food and absorption of nutrients. Leucoraja erinacea, a Chondrichthyan fish otherwise known as little skate, has a very unique digestive system primarily due to the structure of its intestine. The intestine is in the shape of a 3D spiral within the casing of the intestine. I wanted to understand how the skate spiral valve intestine is patterned by gene expression in the embryo given its unique 3D spiral shape. Therefore, I first isolated and cloned Cdx2, a transcription factor known to induce formation of the intestines, using bioinformatics and PCR. The entire Cdx2 sequence for the PCR fragments was successfully cloned. To detect Cdx2 expression in skate embryos, I created an antisense RNA probe and performed an RNA whole mount in situ hybridization. Comparing the expression patterns in skate and chicken embryos helped determine that Cdx2 expression is found in the developing endoderm, which is similar to that of chicken. I also studied the structure of the 3D spiral valve of micro-CT skate embryos by measuring the angle of the spiral folds to determine the extent to which the spiral folding varies throughout the gut tube. Overall, Cdx2 expression aids in the patterning of the spiral valve intestine in skate and therefore is conserved in the digestive tracts of other vertebrates.
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