library_construction_protocol: HEART: Hearts were dissected and immediately transferred to 2% Fetal Bovine Serum (VWR Life Science Seradigm) in Dulbecco's Modified Eagle Medium (DMEM, 11965-092 GIBCO, USA) at 4 oC. Then, the hearts were minced with sterile scissors and digested in digestion buffer (100IU) of collagenase type II/ml in DMEM at 37 oC for 15 minutes. After this the tissue was triturated by pipetting up and down with serological pipettes 15 times, letting it rest 2 min, so the remaining tissue settled at the bottom. The supernatant was collected and centrifuged at 1000rpm for 3 minutes while the remaining tissue was digested again with collagenase (for 15 minutes). After centrifuging the supernatant was discarded and the pellet resuspended in DMEM and kept on ice. This sequence was repeated for 90 minutes (5 times) merging the supernatant of every digestion and keeping it on ice. After this process the isolated cells were treated with Red Blood Cells lysis (R7757, Sigma, USA) for 1 minute and then 15 ml of DMEM was added before centrifuging for 5 minutes at 1200 rpm. The supernatant was discarded, and the pellet was resuspended in PBS with 2mM EDTA to release clumps. SCIATIC NERVES: Sciatic nerves were dissected and immediately transferred to 2% Fetal Bovine Serum (VWR Life Science Seradigm) in Dulbecco's Modified Eagle Medium (DMEM, 11965-092 GIBCO, USA) at 4 oC. Next, the nerves were minced with sterile scissors in digestion buffer: 0.125% Trypsin + 0.3% Collagenase II, and then digested in thermoshaker at 37 oC (750 rpm) for 10 minutes. Finally, the digested nerves were mechanically dissociated by pipetting up and down 20 times and the digestion buffer was blocked by adding 10% FCS for 1 minute, on ice.  The cells were pelleted and then resuspended in FACS media: 0.5% BSA + 5mM EDTA in PBS, passing the suspension through a 40 μm strainer. FACS: Before Fluorescence-Activated Cell Sorting (FACS) the tdt+ cells, DRAQ7 was added to eliminate the dying cells. Viable tdt+/DRAQ7- cells were FACS sorted using a S3 Fluorescence-activated cell sorter (Bio-Rad, Hercules, CA, USA). The sorted tdt+ cells were collected in RLT plus (Qiagen, Venlo, Netherlands) and frozen at -80 oC. RNA-seq libraries were generated using the Ovation SoLo RNA-Seq kit (Tecan). Libraries were quantified using Qubit (Thermo Fisher) and qPCR (Quantabio) and size distribution was checked using a Tapestation 4150 (Agilent). Libraries were sequenced on a NovaSeq 6000 (Illumina).