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From 2013.igem.org

Overall project

Abstract

Bloodletting consists of the withdrawal of blood for therapeutic purposes. It is one of the oldest medical techniques and is nowadays abandonned. However in hematology, bloodletting (also known as phlebotomy) seems to remain the only reliable solution to cure hemochromatosis and thalassemia. Both are genetic diseases diseases and consist of an iron overload. The iron ion is toxic due to its oxidative potential, and thus, has a very smooth regulation mechanism. In fact, the organism only absorbs the required amount of iron from the intestins. The pathogenic mechanism is due to a seemingly low iron rate in the organism and permanantly activate the absorption system by the instestins, thus leading to an iron overload. The consequences are mainly chronic insufficiencies (renal, hepatic, cardiac, ...). Despite the true efficiency of bloodletting, some patients cannot bear this archaic way of treating their disease. As a consequence, we decided to design an Escherichia coli capable of chelating iron in the intestins: Iron Coli. The bacterium will lower the amount of iron absorbed by the duodenum and reduce the frequency of bloodlettings. Also, certain patients are treated with iron chelators which have a lot of side effects. The reduction of iron absorption by Iron Coli will allow lower drug concentrations and improve the patient's comfort.

Targets

Hemochromatosis is a genetic disease responsible for an abnormal iron overload in blood and has a occurence of 1/30000 in Europe. The illness is due to a mutation on the HFE protein which leads to a massive iron absorption by the intestins. In fact, the duodenum is insensitive to the hepcidin hormon, normally responsible for the shutdown of iron absorption. As a consequence, there is a massive entry of iron. Our body is only able to regulate the flux by shutting down its absorption. As a consequence, it starts to stock the iron in all the tissues, leading to chronic deficiencies. Nowadays, the only effective way to treat hemochromatosis is by bleed draining. This treatment is invasive and archaic compared to the actual advances in the medical field.

Thalassemia is also a genetic disease and frequently encountered around the mediterranean sea. The mutations on the hemoglobin monomers reduces the amount of oxygen transported at the scale of the red cells, thus leading to mild or severe anemia. The lack of effective red cells in the oxygen transport results in the fake signal of low iron centration in blood, thus inducting overabsorption from the duodenum. Also, since the patient all have anemia, blood withdrawal is obviously not the way to treat them. The only solutions are the use of iron chelators, with severe side effects, and blood transfusions, which ironically lead to an iron overload.

Beside the two targeted diseases, iron is know to be responsible for increased occurence of

Constructions

Our goal is to lower the iron absorption from the intestines by using an iron chelating bacteria. The gain will be to decrease the frequency of blood draining process and improve the patients lifestyle. We have two main objectives: developping an iron-sensing promoter and overexpressing the siderophore pathway under the control of iron concentration.

Project Details

Part 1

Bacteria engineering and reversed Fur system for iron sensing

Part 2

Modeling on bacteria interaction with duodenum.

The Experiments

Part 3

Results