ABSTRACT
Biological processes depend on the differential expression of genes over time, but methods to make physical recordings of these processes are limited. Here we report a molecular system for making time-ordered recordings of transcriptional events into living genomes. We do this via engineered RNA barcodes, based on prokaryotic retrons1, which are reverse-transcribed into DNA and integrated into the genome using the CRISPR-Cas system2. The unidirectional integration of barcodes by CRISPR integrases enables reconstruction of transcriptional event timing based on a physical record via simple, logical rules rather than relying on pre-trained classifiers or post-hoc inferential methods. For disambiguation in the field, we will refer to this system as a Retro-Cascorder.
Competing Interest Statement
S.L.S., G.M.C, M.G.S., and J.N. are named inventors on a patent application related to the technologies described in this work.
Footnotes
Additional work added including computational modeling of Retro-Cascorder system, testing expression levels from inducible promoters, and testing fitness effects of Retro-Cascorder components