Motivation

Celiac disease is a serious autoimmune disorder that is mainly caused by gluten, which is composed of gliadorphins. Among gliadorphin, amino acid called proline is abundant. This proline causes inflammation in intestinal immunocyte, triggering it to attack absorptive cells and damage small intestine.

This phenomenon causes celiac disease; in order to prevent this, enzyme called DPP4 is used. DPP4(Dipeptidyl peptidase-4) breaks proline down into dipeptide form in n-terminal as the picture explains.

However, the last tripeptide(gln-pro-phe) does not fully break down and eventually inhibits DPP4, slowing down its process. Therefore, additional input of DPP4 is important in digestion to catch up with the inhibition.

As the graph explains, the increasing incidence and altered presentation in a population-based study of pediatric celiac disease in North America was discovered. However, only temporary solutions exist: taking pills regularly or simply regulating the intake of gluten. From 2004 to 2005, sales of gluten-free foods increased by 77.8 million dollars (a growth of 14.6%). We discovered that more people are relying on temporary solutions and fundamental solution is needed, so that they can eat the gluten freely.

To find out the fundamental solution, we casted several questions to think about, focusing on DPP4:

• 1. What is the difference between gluten-digestion disabled and normal? Is it because of the host’s defect in gene regarding DPP4 or is it because of enterobacteria’s other potential cause of gluten digestion capability?
• 2. Analyzing the difference of intestinal flora between normal and disabled focusing on DPP4 using
• NGS (focusing on 16s RNA sequencing)
• Terminal RFLP (checking terminal unit’s number between floras)

As an answer of these questions, we thought of applying the normal enterobacteria’s property of DPP4 into the enterobacteria which is disabled. While brainstorming, we thought of two potential methods:

• 1. Transmuting the disabled intestinal flora by inserting the normal enterobacteria directly by eating yogurts and checking if the intestinal flora has changed its digesting capability
• 2. Directly changing the disabled intestinal flora by using synthetic biology: inserting the normal one’s DPP4 gene into the disabled one and improving the digesting capability

We definitely chose the method 2 as it was the one iGEM is particularly requiring to do. We learned about the general process we should be working on by reading and paraphrasing the protocols that are mentioned in the iGEM website. We each made questions about the protocol and asked each other about general process including mini prep, ligation, backbone plasmid, etc.

After we specified the method by several brainstorming, we looked up more about the DPP4 and found out that it accompanies several side-effects if it is in excess amount.

Accoding to World Preview 2016, Outlook to 2022's analysis of Anti-Diabetics Market to 2022, DPP4 inhibitor has been and will be commonly used as a cure of diabetes, which means that overexpression of DPP4 might lead into diabetes. Therefore, we recognized that we had to regulate the expression in order not to cause the overexpression. We thereby knew that additional gene should be used to regulate the expression of DPP4 to reach the best amount of DPP4 of individuals.