Electronic Thesis and Dissertation Repository


Master of Science


Medical Biophysics


Donna Goldhawk and Lisa Hoffman


Magnetic resonance imaging (MRI) is one of the non-invasive imaging modalities used in longitudinal cell tracking. Previous studies suggest that MagA, a putative iron transport protein from magnetotactic bacteria, is a useful gene-based magnetic resonance contrast agent. Hemagglutinin (HA)-tagged MagA was stably expressed in undifferentiated embryonic mouse teratocarcinoma, multipotent P19 stem cells to provide a suitable model for tracking these cells during differentiation. Western blot and immunocytochemistry confirmed the expression and membrane localization of MagA-HA in P19 cells. Elemental iron analysis using inductively-coupled plasma mass spectrometry revealed significant iron uptake in both parental and MagA-HA-expressing P19 cells, cultured in the presence of iron-supplemented medium. Withdrawal of this extracellular iron supplement revealed unexpected iron export activity in P19 cells, which MagA-HA expression attenuated. The influence of iron supplementation on parental and MagA-HA-expressing cells was not reflected by longitudinal relaxation rates. Measurement of transverse relaxation rates (R2* and R2) reflected changes in total cellular iron content. In particular, the reversible component R2′ (R2* ‒ R2) provided a moderately strong correlation to amount of cellular iron, normalized to amount of protein.