2000 testes from w1118 males were dissected and fixed (see Materials and Methods section for details). Fixed testes were stored at 4°C in wash B. Testes were hand-dissected in wash B to remove the accessory glands. Pools of 1000 testes were transferred in 700ul of sonication buffer dissected in wash B to remove the accessory glands. Pools of 1000 testes were transferred in 700ml of sonication buffer. Conditions were established to obtain chromatin fragments 200-500 bp in length. ChIP-seq, library construction, cluster generation and Sequencing analysis were performed using the Illumina HiSeq2000, sequencing type SR50, following manufacture's protocols (www.illumina.com). In brief, libraries were prepared using Illumina's ChIP-Seq Sample Prep Kit from 3.5 ng of ChIP/Input DNA. Samples were size selected to ̴300-350 bp using DNA magnetic beads. Adaptor-modified DNA fragments were subjected to limited PCR amplification (18 cycles). Using Illumina's Cluster Generation Kit, libraries were subject to cluster generation for subsequent sequencing.