mRNA
Meaning of mRNA: Measuring how much of it a cell holds is the standard way to judge whether a particular gene is switched on or off.
Definition of mRNA
mRNA is the standard abbreviation for messenger RNA, the RNA copy of a gene that carries its instructions to the machinery building proteins. The short form turns up in two very different settings: laboratory reports, where the amount of a gene's mRNA measures how active that gene is, and the names of vaccines built from manufactured mRNA.
Why do laboratories measure it?
| Method | What it measures | Typical use |
|---|---|---|
| Reverse transcription PCR | One or a few chosen transcripts, counted precisely | Confirming a single gene's activity, and detecting the RNA of viruses |
| Expression microarray | Thousands of known transcripts at once | DNA gene expression microarray profiling of tumor samples |
| RNA sequencing | Every transcript present, expected or not | Research, and a growing share of diagnostic work |
All three answer the same question: which genes is this tissue actually using right now. The genome of a tumor cell and a healthy cell may differ in only a handful of places, while their patterns of gene expression differ across thousands. That is why several tests guiding cancer treatment read RNA rather than DNA, scoring the activity of a panel of genes to estimate how a tumor is likely to behave.
Does more mRNA always mean more protein?
No, and treating the two as interchangeable is a common misreading of an expression result. A transcript still has to be exported, translated and left alone long enough to accumulate, and each of those steps is separately controlled. Small regulatory RNAs can silence a transcript that is present in quantity. Proteins differ enormously in how long they survive once made. Correlation between the amount of messenger RNA and the amount of protein is real but loose, which is why laboratories confirm an important finding by measuring the protein itself.
How do mRNA vaccines work?
A synthetic strand coding for one protein from a virus is packaged inside a lipid droplet that fuses with the cell membrane and releases its cargo. The cell reads the instructions and makes that protein, the immune system learns to recognize it, and the strand is degraded within days. The chemical building blocks are modified so the strand is not destroyed as an intruder before it can be read. It stays outside the nucleus and cannot be written back into DNA, so no permanent change is made to the cell.
Also known as
Used in a sentence
The vaccine relies on mRNA to prompt cells to produce a protein that triggers an immune response.
Good to know
Synthetic mRNA used in vaccines instructs cells to make a protein temporarily and is not integrated into the cell's own DNA.