Abstract

In the past few decades synthetic biology and its interdisciplinary interplay with other scientific branches such as engineering has brought progress in various respects. However, practical usage of synthetic biological applications remains mainly restricted to the industrial field, fundamental research and medicine. Therefore, we rarely consciously encounter genetically engineered parts in our everyday life. We, the iGEM Team Freiburg 2014, are convinced that the future potential of synthetic biology concerning conceivable areas of applications has by no means been exhausted yet. With our project we want to demonstrate that synthetic biology is able to open up completely new fields of applications. Hence, we designed a novel communication tool that bridges the gap between synthetic biological and conventional technical components, thereby creating an innovative way of transmitting information. By connecting our biological system with the field of communication, which is an essential part of our social life, we hope to increase accessibility and acceptance towards genetically engineered devices. Our communication tool unites the benefits of several biological approaches. We use a light inducible gene expression system. Such optogenetic methods allow temporal and spatial induction of gene expression by the use of light. However, its biggest limitation is the time consuming introduction of transgenes into organisms or cell lines. Therefore we further use viral vectors, which in contrast, allow to achieve easy but unspecific gene delivery. The combination of the advantages of both approaches – the temporal and spatial resolution of optogenetics, and the simplicity of gene transfer offered by viruses makes it possible to design a system where the entry of a virus is enabled or prevented by exposing the target cells to light of distinct wavelengths.
The ecotropic murine leukemia virus (MuLV) is a retroviral vector which enters a cell by binding to the cationic amino acid transporter (CAT-1). CAT-1 is present in cells of all mammals, but displays a high variability between different species in the third extracellular loop, which is the recognition sequence for the virus. Therefore, even close relatives of mice, e.g. rats or hamsters, are immune to the MuLV, but upon exogenous expression of murine CAT-1, cell lines from these species can also be infected. Hence we use the popular Chinese hamster ovary cell line CHO in our experiments. For optogenetic targeting of specific subsets of cells, we employ three different systems: a red/far-red light system and a UVB light system based on proteins from the plant model organism Arabidopsis thaliana as well as a light-oxygen-voltage (LOV) system from the marine bacterium Erythrobacter litoralis. In all three light systems gene expression is induced by recruitment of engineered transcription factors to DNA. Without illumination the cells are in a dormant state and cannot be infected by the viral vector. Upon exposure to the appropriate wavelength, they start expressing the viral entry receptor CAT-1. Addition of the viral vector to the culture medium leads to infection of the activated subset of cells. Using these principcles we designed a device for secure communication, which works in a two-step process: First, to input the message to be transmitted, the sender has to specify the subset of cells by illumination through a patterned mask. In the second step, upon receiving the device the reader has to visualize the message by adding the appropriate viral vector containing a reporter gene. The unintended opening of the device by an unaware third person results in a complete illumination of the cells leading to the destruction of the message. The time gap between sending and receiving the device is limited by the half-life of the receptor, thus creating an additional safety level. An additional feature of our communication tool lies in the capability/ possibility to generate variable QR-Codes. This allows linking the electric and the biological tools for communication.
Our communication tool shows only one of many possible ways to implement biological technologies in information delivery and we hope to inspire an unconventional way of thinking of synthetic biology- reaching out to fields where nobody believed the biological potential would appear.