Introduction: Deficiencies of guanylyl Cyclase C (GCC), a transmembrane receptor of large intestine epithelial cells, is associated with an increased risk for colorectal cancer (CRC) in mice. Therefore, elucidating the downstream pathways associated with GCC may help inform new therapeutic targets for treating CRC. We performed an RNA-sequencing analysis of GCC+/+ and GCC-/- mice and hypothesizes that the two groups would demonstrate significant variations in gene products that may be tied to the GCC signaling pathway.
Methods: Cells from five GCC+/+ and five GCC-/- mice were collected and analyzed for mRNA expression levels of over 20,000 genes. mRNA expression levels were compared between the two groups using RStudio to assess for differences in gene expression that may be attributable to a lack of GCC. Differences in mRNA expression levels were calculated using RStudio, and the gene ontology database PANTHER was then used to identify specific downstream proteins and cellular pathways that may be tied to GCC expression levels.
Results: Mean total mRNA expression levels between each of the mice were comparable. mRNA expression levels for GCC greatly differed between the two groups (p < 2x10-40).However, multiple dimension analysis (MDA) of the ten mice did not show significant overlap between the GCC+/+ and GCC-/- mice. Cellular enrichment pathways did not identify any proteins of interest.
Discussion: The differences in GCC mRNA levels indicates successful knockout of the gene of interest. MDA suggest that the mice within each test group may have significant baseline differences, which could have confounded the results. Proteins identified using PANTHER were not known to have correlations with GCC. Ensuring the mice are genetically identical and identifying a new gene ontology database represent critical next steps.
Hoeltzel, Gerard and Waldman, MD, PhD, Scott, "Using RNA-seq to Identify Biomarkers for Guanylyl Cyclase C Activity" (2021). Phase 1. Paper 71.