Dr. Potts and his team have studied cells from PWS ‘baby teeth’ to identify changes in cellular function in PWS. They found that the vesicle recycling is altered in PWS cells, and that this is a consequence of loss of the gene, MAGEL2. They also described that developmental changes in cells from children with PWS compared to typical children. In their second year of funding, they will characterize and quantify these developmental changes, in order to not only understand how PWS genes work at the cellular level, also working towards developing a platform to screen drugs that might help restore normal function in PWS cells.
Dr. Theresa Strong, Director of Research Programs, shares details on this project in this short video clip.
Watch the full webinar describing the 9 research projects funded in this grant cycle here.
MAGEL2 is a gene frequently deleted or mutated in individuals affected with PWS. Furthermore, mice lacking MAGEL2 display symptoms similar to those seen in PWS children. However, a critical barrier to our understanding of MAGEL2’s link to PWS has been determining its function within cells. Recently, my group has solved this enigmatic question. We showed that MAGE-L2 functions to prevent aberrant degradation of proteins that normal reside in the plasma membrane. It does so through the specific modification of another protein, called WASH. This modification, termed ubiquitination, activates the WASH protein that facilitates recycling of proteins sparing them from aberrant degradation in the lysosome, the garbage can of a cell.
In year 1 of this proposal, we aimed to determine whether MAGEL2’s function in endosomal recycling is observed in patient-derived primary neuronal cells that originate from dental pulp stem cells taken from discarded ‘baby teeth’. Furthermore, we aimed to determine whether there is a genotype-to-phenotype relationship between the genetic causes of PWS (deletion or uniparental disomy), presence of autism spectrum disorder, and defects in endosomal trafficking. Finally, we aimed to move beyond characterization of the cellular defects of PWS to explore proof-of-principle treatment strategies to rescue endosomal recycling pathways in the hope to discovering new therapeutic avenues. From our studies thus far, we have confirmed that indeed neurons derived from PWS patient cells, regardless of genotype, have defective endosomal trafficking. Furthermore, we can rescue this defect by expression of wild-type MAGEL2. Thus, our findings from year 1 suggest that loss or mutation of MAGEL2 has a direct impact on relevant patient-derived cells.
Having validated this cellular model, we now propose to extend these studies in year 2 to track developmental differences between the generation of PWS and healthy neurons. After the neurons are generated, we will examine and compare their cellular structure and function, including protein trafficking controlled by MAGEL2. We predict that neurons generated from PWS patients may be morphologically different from healthy neurons and show defective protein trafficking. We will also examine novel missense MAGEL2 mutations reported in individuals with phenotypes overlapping with PWS and SHFYNG. These MAGEL2 mutations cause certain PWS and SHFYNG symptoms in affected individuals, but they have not been previously characterized. Together, findings from our study will enable better understanding of the cellular defects in PWS and SHFYNG disorders. Moreover, our work lays the foundation for a disease-relevant cellular model to allow screening of novel therapeutics.
Ryan Potts, Ph.D
Ryan Potts, Ph.D