An interview with Dr Martin Hemberg, Wellcome Trust Sanger Institute, conducted by April Cashin-Garbutt, MA (Cantab)
What is single-cell RNA sequencing and how can it help define cell types?
RNA sequencing is basically the isolation of RNA from cells and the use of reverse transcriptase to turn the RNA into DNA. You can then use your standard DNA sequencing technologies to quantify the cDNA that you obtained from the reverse transcription reaction. The assay allows you to quantify the amount of RNA in a global- and genome-wide manner.
This technology became popular around ten years ago, but around say two or three years ago, the cost of the technologies, as well as the technologies themselves, were improved to the extent that it has become feasible for many labs to do this type of assay at a resolution of individual cells. This is quite different from what was done previously, where millions of cells were required to get enough RNA.
Before you had single cell, the problem was that having whole tissue, or a whole sample, which was almost certainly heterogeneous, is the equivalent of taking your sample and putting it through a blender. You then have a big, smooth sauce coming out of it and you don’t really know what the original components were.
With single cell, you can identify each individual cell that went into your sample. By characterizing individual cells, it’s possible to compare them and find cells that look similar and they are the ones that you’ll define as specific cell types.