Team:Kyoto/CiC/Introduction

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Our project aims to reconstruct mitochondria, but our ultimate goal was once creating a cell.
Our project aims to reconstruct mitochondria, but our ultimate goal was once creating a cell.
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I'll tell you why we got interested in reconstruction of Mitochondria.

Revision as of 18:17, 19 October 2009

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Project2 -- Cells in Cells --

Our project aims to reconstruct mitochondria, but our ultimate goal was once creating a cell. I'll tell you why we got interested in reconstruction of Mitochondria.


Minimalized Genomes?

Inspired by the idea of minimum genomes and synthesizing cells, one of Kyoto iGEM team members came up with the idea of reconstructing mitochondria or chloroplasts, whose genomes have been minimalized in evolutionary history. According to endosymbiotic theory, these organelles originated as bacterial endosymbionts. So reconstructing such organellas, in other words ex-cells, seems to us as interesting as synthesis of the present bacterial cells. We are also interested in what scientists aiming to syntesize "cells today" think of when mitochondria or chloroplasts are completely reconstructed.


What is the Difference between Cells and Mitochondria or Chloroplasts?

They have lost many genes in the evolutionary process of adaptation to environment. Mitochondria and chloroplasts are strongly dependent on nuclear genome for their proteins needed to maintain their functions. This is why they cannot be cultured in medium as E.coli is easily cultured. Many proteins with signal peptides are translated in cytoplasm and imported into mitochondria or chloroplasts through a few translocases on their membranes. They also have their own genetic systems but even the systems do not work without imported cytoplasmic proteins. Only in host cells they look and act partially like living cells In a sense, they can be regarded as cells which remain alive only in host cells.


Synthesis of Cells?

We consider reconstructing mitochondria or chloroplasts as poor man's synthesis of cells. Technologically or financially speaking, a mitochondrion or chloroplast seems easier to reconstruct than a whole cell because components required to do that are much less. We mentioned an extreme argument that mitochondria and chloroplasts are potentially cells above. The reason why we mentioned it is that this project originally had a nuance of irony toward the overwhelming difficulty in and ambiguous definition of synthesizing cells.


What is Interesting in This Project?

Apart from such irony, reconstruction of mitochondria itself seems interesting and exciting, doesn't it? Though cells are too complicated system, mitochondria and chloroplasts themselves are also complicated enough to tackle. Then one of the keys to solve the problem is the fact that mitochondria and chloroplasts contribute little to maintaining themselves as mentioned above. They cannot manufacture what they need by themselves, so they need to import them through special loopholes. Imagine what will happen if liposomes with such loopholes (translocases) are put into host cells full of products of translation. Such "prepared liposomes" can act like mitochondria or chloroplasts by eating and using proteins for these organelles.


Mitochondria or Chloroplast?

We have designed many types of prepared liposome, such as one with mitochondrial Inner membrane translocases, one with mitochondrial outer membrane translocase, one with chloroplastic Inner or outer membrane translocases, each one with its genome and so on. At first we planned to select both mitochondrion and chloroplast as model organisms. Chloroplasts seemed easiler to observe because they have more bacteria-like system than mitochondria. And translocases of chloroplasts seemed easier to use because they don't require H+gradient when precursor proteins go across double membranes. But we had difficulty in getting enough information on translocases of chloroplasts. In addition to that, we thought it so difficult to introduce prepared liposomes into plant cells because of cell wall. Then we selected mitochondria as model organism, for mitochondria and mammalian cells are easier to deal with.

We set two subgoals. 1. Designing and constructing liposomes which can take in mitochondrial proteins from cytoplasm. 2. Introducing them into host cells.