This week, Kathy, Usman, and I split up to learn more about different aspects of PathLinker. I researched the Wnt/β-catenin signaling pathway, precision-recall curves, and the role of CFTR and Dab2. On Wednesday, we all presented the topics we had researched to each other and Anna and Ibrahim.
To briefly summarize what I learned, the Wnt/β-catenin pathway regulates the transcription of certain genes related to cell proliferation, cell attachment, and growth. When the Wnt/β-catenin signaling pathway is dysregulated, a number of pathologies can develop including cancer and heart disease. In fact, in a study on colon adenocarcinoma by the Cancer Genome Atlas, 93% of tested tumors had a mutation that affected the Wnt/β-catenin signaling pathway (TCGA, 2012). At the most basic level theWnt/β-catenin signaling pathway is turned on when Wnt proteins bind to “frizzled” a 7-pass transmembrane receptor which halts the destruction of β-catenin in the cell. Usually, when the pathway is off, β-catenin is constantly being produced and destroyed. When β-catenin destruction is interrupted, β-catenin will build up in the cytoplasm and move into the nucleus where it will bind to LEF and the TCF promoter to promote the transcription of specific genes that were previously being inhibited by a transcription factor that was bound to TCF. The Wnt/β-catenin signaling pathway involves many proteins and interactions, some of which we still do not understand. The PathLinker algorithm succesfully identified a path in the Wnt/β-catenin signaling pathway that was not in the KEGG or NetPath database: the Ryk-CFTR-Dab2 path (Ritz et al, 2016). The authors of the paper hypothesized that Ryk would interact with CFTR (Cystic Fibrosis Transmembrane-conductance Regulator), a chlorine ion channel previously studied for its role in cystic fibrosis, which would activate Dab2 to inhibit β-catenin activity. This hypothesis was experimentally confirmed by silencing Ryk, CFTR and Dab2 individually using RNA interference and then testing transcription levels of β-catenin controlled genes using a TCF/LEF luciferase activity and levels of β-catenin in the cell using a Western Blot assay.
We also attended a data management workshop taught by David Isaak, Reed’s data science librarian to learn how to use Git and GitHub. Because I’ve never really used terminal before (I usually use repl.it), I worked through a command line tutorial to learn more about it.
On Thursday, Kathy, Usman, and I went through our Dijkstra code with Anna, and finally got it to work the way we wanted it to. Anna added us to the cancer-linker repository on GitHub so we can all begin to actually work on PathLinker now.
My next project is to figure out how to take data from FireBrowse, a database containing data from TCGA on 38 different cancer types, put it into a format we can use, and apply several statistical analyses to the information. I’m hoping to base it off of PepperPathway, a program written by Nicholas Egan, a student in Anna’s lab last summer, that uses data from FireBrowse, GeneCards and NetPath and to create a visual representation on GraphSpace. I’m struggling to make sense of the PepperPathway program because there are a lot of files on the GitHub repository and I’m not really sure where to begin. I’m going to try to make sense of it this weekend.
References
- TCGA Research Network. Comprehensive Molecular Characterization of Human Colon and Rectal Tumors. July 19, 2012. Nature. DOI: 10.1038/nature11252.
- Ritz, Anna et al. “Pathways on Demand: Automated Reconstruction of Human Signaling Networks.” Npj Systems Biology And Applications 2 (2016): 16002. Web.