Critique of “A universal RNAi -based logic evaluator that operates in mammalian cells”

1. Critique of “A universal RNAi-based logic evaluator that operates in mammalian cells”

2. Lack of description of sensing • Want to measure presence or absence of certain states (endogenous mRNA in the cell) • For this, need them to repress RNAi (sensing mechanism), which the paper does not discuss

3. General criticisms • Can we really call this an in vivo study? The researchers are manipulating immortalized cell lines • Need to give cells the genes for the circuitry • Unintended changes from this manipulation of the cell (cell could now be in a very different state) • For what molecules are there always RNAi enabling this construction? Could there be interference for some?

4. Theoretical questions • Is there any “positive” constructs we can make (instead of A represses RNAi-A, which, if present, would repress translation) • Amount of the different components to add seems fairly arbitrary, and perhaps can be manipulated to make the results nice • Is there any way of being able to set the concentration levels a priori?

5. Applicability • It can potentially be useful to evaluate a logic expression of endogenous states of a cell (even if it is simplistic) • However, the need to transfer the circuitry into the cell raises questions about whether you can do this evaluation, and whether you could do this in vivo • Real human cells are a lot more difficult to manipulate than the human embryonic kidney 293-H cells that the authors used • How robust would the method be under individual variations? • However, we may eventually have a biotechnology allowing us to infect people with cancer-curing viruses

6. Warning! Cancer-curing virus could kill most of the human population, and turn the rest into darkness-seeking zombies