library_construction_protocol: Cochlea (2-4) from P3 pups were collected and incubated with 1 mL Accutase solution (Innovative Cell Technologies) for 15 minutes at 37°C.  The Accutase solution was removed and cochlea were gentle washes in ice cold Ca2+, Mg2+ - free HBSS buffer.  Organs were dissociated by trituration for 2-3 minutes.  Cells were then filtered with a 40 μm cell strainer (BD Biosciences) and kept on ice until sorted.  For the exclusion of dead cells and debris from the samples during sorting, a single-cell suspension was stained with DAPI.  Sorting was performed at 4°C in a FACSAria II cell sorter (BD Biosciences) using a 130 μm nozzle.  Scatter discrimination was used to eliminate doublets and samples were negatively selected with DAPI to remove dead cells and debris.  For scRNA-seq, single GFP+ cells were captured into 96-well plate with 11.5 ml lysis buffer and RNase Inhibitor without the CDS IIA Oligo (Takara Bio, Mountain View, CA), and stored at -80°C until used for construction of cDNA libraries. Single-cell RNA-seq libraries were constructed according to the SMART-Seq Single PLUS protocol (Takara Bio, Mountain View, CA).  Frozen 96-well plates with single cells were thawed on ice.  Next, cDNA was generated with the addition of the 3' SMART-Seq CDS Primer II A and SMARTScribe II RT reagents.  cDNA was amplified via 20 cycles of PCR, purified, and assessed for quantity and quality by Qubit dsDNA assay (ThermoFisher, Waltham, MA) and Fragment Analyzer (Agilent, Santa Clara, CA) analysis, respectively.  For each well, 1 ng amplified cDNA was fragmented and prepared for library construction with the addition of stem-loop adapters.  Final library amplification and indexing was performed through 16 cycles of PCR amplification.  Following bead purification, individual library profiles were assessed by Fragment Analyzer and quantified by Qubit dsDNA assay.  Libraries were diluted, pooled in equimolar amounts, and sequenced on a NovaSeq S1 flowcell (Illumina, San Diego, CA) to generate an average of 10 million reads per cell.