Towards sequencing by synthesis In Situ

Abstract

The development of fluorescence in situ nucleic acid sequencing (FISSEQ) will permit investigators to answer scientific questions in which the spatial context of gene expression rather than just identity and abundance - must be taken into account; recent progress in biological sample engineering, including physical expansion of tissue (i.e. Expansion Microscopy), will radically empower this technology (ExSEQ). However, in situ sequencing is technically difficult to implement, requiring an investigator to be familiar with a wide variety of techniques in molecular biology, microfluidics, fluorescence microscopy, image processing, and bioinformatics, and improvements are still needed before it is widely practicable. In this work, we investigate the use of sequencing by synthesis - as opposed to the currently practiced method of sequencing by ligation - in order to realize improvements in usability and performance. We demonstrate the viability of sequencing by synthesis reactions in situ, characterize their performance, and describe a route from demonstration to practice.