As explained in Project #2, many genes are turned off by chemical modifications (epigenetic marks) that silence genes and prevent their activation. This inactivation often occurs at enhancers, which are regions of DNA that control the activation of genes. In this project, Piotrowski will use the ATAC-seq and H3K27ac ChIP-seq methods, which were successful for the mouse inner ear, to find enhancers that are active during hair cell regeneration in the fish. Identification of regeneration enhancers will enable the HRP to examine epigenetic marks comparatively—to determine whether regenerating species, such as the zebrafish and chick, utilize different enhancers than non-regenerating species like the mouse, or whether these enhancers are inactive in mammals.