Andrew Pagel, “Modeling a Human Noonan Syndrome Mutation in Caenorhabditis elegans Raf”
Mentor: Claire de la Cova, Biological Sciences
Poster #138

The MAP Kinase (MAPK) pathway allows animal cells to communicate signals relating to cell proliferation, differentiation, and apoptosis. Extracellular growth factors initiate signaling by binding to receptor tyrosine kinases (RTKs). The small GTPase Ras is one downstream effector of RTK signaling, and stimulates a kinase cascade comprised of Raf, MEK, and the MAPK ERK. Mutations in the human RAF1 gene are linked to Noonan Syndrome (NS), a developmental disorder involving heart defects, short stature, and cognitive deficits. Causative mutations associated with NS have been identified in three distinct conserved regions of the RAF1 protein: a 14-3-3 binding site, the kinase domain, and the C-terminal domain. These mutations have been shown to be gain-of-function and increase ERK signaling. However, the mechanisms by which mutations alter signaling and affect protein-protein interactions in NS are unknown. Using the nematode Caenorhabditis elegans, our lab has generated mutations in C. elegans Raf equivalent to those seen in the human RAF1 gene of NS patients. We have used gene editing to insert green fluorescent protein (GFP) at the N-terminus of the Raf gene. This endogenous GFP-tagged Raf, along with the transparent nature of C. elegans, allows us to observe Raf protein levels and localization with confocal microscopy. During my SURF (Support for Undergraduate Research Fellows) experience, I generated the NS mutation L648V. I am planning to investigate how L648V affects Raf protein levels, localization, and ERK activity in the C. elegans germline and vulval precursor cells. Our long-term goal is to gain a better understanding of Raf function and to develop treatments that normalize Raf activity in human NS patients.