Cross-linked neuronal progenitor cells (2 days) and E15.5 mouse embryonic brain tissue were lysated, and neuclei were isolated. The nuclear pellet was re-suspended in 1 ml of cold shearing buffer (10 mM Tris-HCl pH 8.1, 1 mM EDTA, and 0.1% SDS) and chromatin was then sheared to 100-300 bp fragments using a Covaris S220 sonicator (Covaris; Woburn, MA) with the following settings; 12.5 min, 5% duty cycle, 140 Watts peak incident power, 200 cycles per burst. After adding 1% Triton X-100 and 150 mM NaCl (final concentrations) to the sheared chromatin and mixing, the solution was cleared by centrifugation at 14,000xg for 10 min at 4°C. Chromatin fragments were incubated with 2.5 μg of affinity purified anti-Tet3FL antibody (raised against a region of Tet3FL, amino acids 1-102) or IgG control (Santa Cruz; SC-2027) overnight at 4°C with rotation, and then immunoprecipitated using protein A magnetic beads (Millipore; Billerica, MA). Libraries were prepared according to Illumina's instructions accompanying the DNA Sample Kit (Part# 0801-0303).