How does the spiral intestine form?

Spirals are rarely found in nature, and how they form is different from snail shells to plant tendriles. Our lab is exploring how the spiral forms inside the tube of the skate intestine. We want to understand how it is initiated early in the embryo, and how it continues to wrap tightly through later stages of development. The image on the left is a cross-section of the spiral intestine stained for F-actin in green. Constrictive forces resulting from the differentiation of muscle fibers seen with the F-actin staining may be involved in spiraling.

Are the genes that pattern the digestive tract organs conserved in the skate?    Several groups including our own have identified genes that subdivide the embryonic gut tube into different regions, and instruct the regions to form distinct organs along the gut tube. The expression of these genes are tightly regulated so that organs appear in a functional order. For example, the stomach breaks down the food you eat comes before the small intestine that absorbs nutrients. Different animals have variations in the organs of their digestive tracts based on the animal’s diet and environment. Because skates are ancient fich and have a unqiuely-shaped spiral intestine, we wonder if the same genetic program to make the organs of the digestive tracts of other animals (like the chicken and mouse) exist in the skate.

What is the structure-function relationship of a spiral intestine versus a long coiled intestine? Can we design better organs?  All sharks, skates and rays have a spiral intestine.  Unlike us, with 15-20 feet of coiled intestine, skates have narrow abdominal cavities filled with two large liver lobes – the liver enables buoyancy in the water. The spiral intestine is thought to create a large surface-area for absorbing nutrients within a shorter stretch of intestine. We are collaborating with Prof. Wang (Math) to quantitate and explore the spiral structure in relationship to the fish’s metabolism. Is there an advantage to having a spiral intestine? Perhaps instead of bioprinting intestinal tubes, we can design a better organ for patients with malabsorption.

Can we simulate morphogenesis during evolution?

The spiral valve intestine appears as an intermediate structure during evolution, between the straight digestive tracts of jawless fish (they also lack a stomach) to elongated intestines like ours that are coiled. Through computer simulations we aim to better understand how the intestines changed their shape and make predictions of how morphology evolved in animals.