Epigenomic analysis of Formalin-Fixed Paraffin-Embedded samples by CUT&Tag

For more than a century, Formalin Fixed Paraffin Embedded (FFPE) sample preparation has been the preferred method for long-term preservation of biological material. However, the use of FFPE samples for epigenomic studies has been difficult because of chromatin damage from long exposure to high concentrations of formaldehyde. Previously, we introduced Cleavage Under Targeted Accessible Chromatin (CUTAC), an antibody-targeted chromatin accessibility mapping protocol based on CUT&Tag. Here we show that simple modifications of our single-tube CUTAC protocol are sufficient to produce high-resolution maps of paused RNA Polymerase II (RNAPII) at enhancers and promoters using FFPE samples. We find that transcriptional regulatory element differences produced by FFPE-CUTAC distinguish between mouse brain tumor specimens and identify regulatory element markers with high confidence and precision. Our simple workflow is suitable for automation, making possible affordable epigenomic profiling of archived biological samples for biomarker identification, clinical applications and retrospective studies. We used FFPE-CUTAC, a modification of the CUT&Tag chromatin profiling strategy, whereby antibody-targeted controlled integration of DNA sequencing adapters at sites of paused RNA Polymerase II or between nucleosomes flanking open chromatin sites produces libraries for paired-end sequencing from Formalin-Fixed Paraffin-Embedded (FFPE) sections. Grant information: T32CA009515 - Ronald M. Paranal - National Cancer Institute