Team:ASIJ TOKYO/Design
What is CRC?
Colorectal cancer is the second most lethal cancer in the United States, often beginning as benign polyps in the colon and rectum. Despite ease of treatment, cases of CRC are usually detected in its late stages, rendering care difficult. CRC results from the mutation of multiple genes involved with the regulation of cell proliferation and DNA repair, and this year ASIJ iGEM team focused in on the Wnt pathway. The activation of the Wnt pathway inhibits the degradation of beta-catenin, a protein that triggers the mutation of oncogenes and tumor suppressor genes. Through detection of these mutated genes and subsequent downstream proteins, our team aims to develop an early screening method that can be adapted to a home detection kit. Building off of a rapamycin induced split-luciferase system characterized by the 2015 Peking iGEM team, our construct consists of a promoter reporter system that looks at two downstream products, c-Myc and COX-2. The construct consists of a promoter-reporter system that looks specifically at two downstream genes, c-Myc and COX-2 These products are assembled into a construct composing of fusion proteins as well as split luciferase fragments: COX-2 - n-Luc - FRB and FKBP - c-Luc - c-Myc. In the presence of rapamycin, the interacting protein partners dimerize and subsequently cause luciferase to activate. In order to test this model, we created vectors of our constructs and inserted them into e-coli cells. We began our experiments with a competent cell check to find the optimal concentration of DNA for working with NEB 5-alpha Competent E. coli. Next, we found the ideal promoter strength for the growth of COX-2 and c-Myc by performing the Gibson Assembly with three different Anderson promoters of different strengths. In order to observe phenotypic proof of these results the competent cells were transformed and plated, as well as expanded into solution so both the number of colonies, as well as the optical density of the solutions were used to support the optimal promoter strength. The next step was to find the most efficient promoter-to-binding domain combinations for both the c-Myc and COX-2 genes by testing a variety of them and seeing which produced the most glowing colonies in the presence of rapamycin. We also utilized this phase to make sure that the combinations glowed only when rapamycin was present. We concluded this test with the combinations of the COX-2 promoter with the FRB domain, and the c-Myc promoter with the FKBP domain being the most efficient combinations. The last step was to ensure that the construct glowed only when all parts were present, and to prove that the promoters had altered the shape of the nonspecific binding domains to become specific to the corresponding proteins. We did this by expanding incomplete combinations into tubes and observing whether they glowed or not. We found that none of the tubes glowed, no matter if they were missing a gene, or one of the promoter-reporter systems. The only tube that glowed was the one containing both COX-2 and c-Myc promoter-reporter systems, both respective genes, as well as rapamycin.
