Image based in situ sequencing for RNA analysis in tissue

Profiling of gene expression is necessary to study the function of cells, organs and ultimately organisms, in health and disease. However, the currently available mRNA sequencing methods are limited to homogenized tissue samples. Therefore, the obtained information represents either the average expression profile of the full tissue sample or expression profiles from isolated single cells extracted from the tissue. We have developed an image-based approach for sequencing of mRNA fragments directly in fixed tissue. As opposed to current routine techniques, this allows gene expression profiling in relation to the preserved morphological and spatial information of cells and tissue. We present here the details of the image analysis and demonstrate its application to breast cancer tissue samples.