A technique that measures gene expression while preserving the spatial context of cells within a tissue sample.Spatial transcriptomics is a family of laboratory methods that measure which genes are switched on in a tissue while keeping track of exactly where in that tissue each measurement came from. Traditional gene-expression profiling, such as bulk RNA sequencing, grinds up a sample and averages everything together; single-cell sequencing separates cells but loses their original positions. Spatial transcriptomics keeps the map. The result is a picture of a tissue in which each spot or cell carries a list of active genes, so you can see that, say, cells near a tumour's edge express different genes from cells at its centre. This matters because in biology location is often function: a liver lobule, a developing embryo, or a tumour is organised into zones whose behaviour only makes sense in context. The technique lets researchers compare healthy and diseased tissue not just by what genes are active, but by where, revealing spatial patterns that would otherwise be averaged into invisibility.
The approach emerged in the mid-2010s. A widely cited early demonstration was published in 2016 by Patrik Ståhl and colleagues, who combined positional barcoding with RNA sequencing on tissue sections; commercial platforms followed later, and the field expanded rapidly as methods for single-cell resolution were developed.
Most current methods work by placing a thin slice of tissue on a specially prepared surface. That surface is covered with thousands of tiny capture sites, each carrying a short DNA tag whose sequence encodes its own x-y coordinates. When the tissue is permeabilised, messenger RNA molecules leak out, bind to the nearest capture site, and are copied into stable DNA. Sequencing then reads both the gene identity of each captured RNA and its positional barcode, and software reassembles the data into a spatial map. Some approaches instead image individual RNA molecules directly inside intact tissue using fluorescent probes, trading some gene coverage for single-molecule resolution.
Used in cancer research to map tumour heterogeneity and the surrounding immune microenvironment, and in developmental biology to trace how gene activity is patterned across a growing embryo.
The positional barcodes on a spatial transcriptomics slide are essentially a microscopic grid of addresses, so a single glass slide can hold tens of thousands of uniquely identified capture spots.
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