To help molecular biologists in the difficult task of keeping abreast of current events in the world of cells and organisms, they employ reporter genes to 'broadcast' specific happenings. For example, if a scientist is interested in the whereabouts and activities of a certain gene, the reporter 'follows' it, and when this gene is activated in any way, the reporter gene produces an easily detectable protein, such as green fluorescent protein (GFP). The scientists are then able to 'read' this 'report' and learn about the specific events that are occurring and in what regions.
The light given off by these proteins is scattered in the tissue, however, reducing the resolution of many images. An alternative to fluorescent proteins is reporters that would be detectable via magnetic resonance imaging (MRI). But for most of the candidate reporters proposed so far, a second material needs to be administered in addition to the reporter gene to allow the MRI to detect its signals. Unfortunately, processes such as fetal development and those that take place within the central nervous system present barriers to these additional substances.
Prof. Michal Neeman and Dr. Batya Cohen of the Weizmann Institutes Biological Regulation Department, along with Ph.D. students Keren Ziv and Vicki Plaks and colleagues, have now developed genetically modified mice that carry a promising candidate reporter named ferritin, which could circumvent these problems. Ferritin works by sequestering iron from cells. When it is overexpressed, iron uptake increases, causing signal changes in the surrounding environment that can be detected by MRI, without the need to administer an additional substance.
As recently described in the journal Nature Medicine, ferritin has so far successfully broadcast live reports via MRI detection from the liver, endothelial cells and even during fetal development in pregnant mice, without the need for additional substances.