Project Summary - The Missing Genome:
Mitochondrial DNA Deletions in Stem Cells

    Although we all start out as embryonic stem cells (ESCs), a mass of cells that eventually differentiate into cells that comprise our complex bodies, they are also extremely applicable to medicine and research. These cells may be able to replace damaged cells and drastically change the way we treat diseases. Induced pluripotent stem cells (iPSCs) generated by a variety of methods also hold great promise for medical use in that they are similar to ESCs, but are easier to obtain as they are generated from somatic cells instead of embryos. Furthermore, these remarkable cells alleviate many of the issues relating to transplant rejection since they can be generated from a patient's own cells. Unfortunately, recent research has shown that iPSCs differ from ESCs in that they have a much higher rate of apoptosis, have a decreased rate of proliferation, and age prematurely. The reason for these anomalies has yet to be explained.

    Based on Harman's Free Radical Theory of Aging which states that organisms age because of accumulation of damage in the mitochondria over time, I hypothesized that this phenomenon of rapid senescence may be triggered by a large deletion in the mitochondrial DNA (mtDNA) of iPSCs. This specific deletion is known to be associated with aging cells and is in fact called the "common deletion" due to its prevalence among patients with mitochondrial myopathies. Other somatic mtDNA deletions and mutations often lead to several disorders including cancer and Parkinson’s disease.

    Presence of the "common deletion" was analyzed using polymerase chain reaction on the mtDNA of iPSCs generated by different methods, their source cells, and the mtDNA from a patient known to have the deletion as a positive control. This project demonstrated that iPSCs do, indeed, contain this specific deletion.

    In addition, transmission electron microscopy was utilized in order to determine whether any morphological differences exist between the mitochondria of iPSCs and their source cells. The results demonstrate that iPSCs have mtDNA deletions and morphological changes that may be the basis for their premature senescence. My research therefore suggests a diagnostic test for determining whether new methods of generating iPSCs hold capacity for medical use. All preparative methods that I have studied to date show evidence of the deletion, although additional experiments are currently in progress to determine whether the method of iPSC preparation affects the abundance of these deletions.


Disclaimer: All media contained within my Google Science Fair entry is original and was created on my own in accordance with the official 2012 Google Science Fair rules and guidelines.