E10.5 mouse otocysts or E14 mouse cochleae were dissected, tissue was digested with Collagenase (C0130, Sigma, 0.3mg/ml) during 45 minutes at 37ºC and cells were suspended and counted in a Neubauer chamber. Assay for Transposase-Accessible Chromatin with high throughput sequencing (ATAC-Seq) experiments were performed as described in Buenrostro et al., 2015. Curr. Protoc. Mol. Biol. 109, 21.29.1-9. doi:10.1002/0471142727.mb2129s109