Molecular Biologists Receive Live Broadcasts Via MRI

Ferritin, the iron storage protein, is being evaluated to be a candidate reporter for the detection of gene expression by magnetic resonance imaging (MRI).

To help molecular biologists in the difficult task of keeping abreast of current activity in cells and organisms, they utilize reporter genes to ‘broadcast' specific happenings. For example, if a scientist is interested in the location 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 in what regions.

The light given off by these proteins is scattered in the tissue, 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 from the Weizmann Institute's (Rehovot, Israel) biological regulation department and coworkers have now developed genetically engineered 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 alterations in the surrounding environment that can be detected by MRI, without the need to administer an additional substance.

As recently described in the April 1, 2007, issue of 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.


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Weizmann Institute