Project Outlines

Fig 1 Administration of L-DOPA via bacteria in the patient's gut

iGEM Manchester-Graz’s objective as a team is to find a better way to treat and alleviate the symptoms of Parkinson’s disease (PD) through the use of synthetic biology. Degradation of dopaminergic neurons and therefore low levels of dopamine is the main cause of Parkinson’s disease (PD), for which the current treatment involves oral doses of L-DOPA (or levodopa), which unlike dopamine itself is able to cross the blood-brain-barrier. Within the brain L-DOPA is enzymatically converted into dopamine and therefore able to relieve many of the motor symptoms of PD (Figure 1).

Our aim is to take the first steps in the development of a novel technology of drug delivery by developing self-regulating drug-producing bacterial strains that, in the future, could be incorporated into patients’ gut microflora to secrete medicines directly inside the body. To control the bacterial L-DOPA production, we plan to develop a multidimensional cell density dependent auto-regulation system that could also be used to control other multistep enzyme pathways.

Fig 2 dopamine and L-DOPA biosynthesis pathways

The Manchester section of the team are working on L-DOPA and dopamine biosynthesis in E. coli BL21 and Nissle 1917 via various enzyme pathways. The focus is on three enzyme pathways, the main one being the conversion of L-tyrosine to L-DOPA via tyrosine hydroxylase and tyrosinase. In addition we are also synthesising dopamine in two different ways using aromatic amino acid decarboxylase, cytochrome P450 and transaminase. Although the primary goal would be to implement the L-DOPA synthesis within patients, we also aim to create a greener, more efficient way of the industrial synthesis of each of the above products using our modified bacteria. (Figure 2)

The Graz section are using two quorum sensing based mechanisms for an auto-regulated and time shifted consecutive induction of protein expression, first demonstrated using fluorescent protein synthesis (Figure 3). The fluorescent protein could then be exchanged with genes for the L- DOPA production such that at low cell density levels tyrosine synthesis will be channeled. After a certain biomass is reached actual L-DOPA production will be induced.

Looking to the future this system could be further utilized to activate suicide genes in E.coli to avoid possible overgrowth of the native intestinal flora, which we aim to show proof of concept in both strains common to academic research as well as probiotics, specifically BL21 and Nissle 1917 respectively. Even though we cannot regulate the proliferation of our engineered strain yet, it allows us to provide an outlook of a possible application as a self-regulating drug dispensing system in the GI tract, which may have clinical applications in the future.

Fig 3 Fluorescent protein synthesis dependent on different levels of cell density

Throughout the course of the project we also aim to shape our actions in accordance to the opinions of academics, charities, industry leaders and the public. This includes what implications our project will have for patients both economically and in terms of quality of life and whether the real world implementation of this technology is feasible. We will also compare ethical opinions throughout outreach about our project and synthetic biology in general across the two countries our team spans and assess this in a wider sociological context. We feel as a team that the issues and human practices surrounding our project are just as important as the project itself and as such we endeavour to tackle a wide selection of concerns.