library_construction_protocol: Total RNA was extracted from sorted spermatocytes and also from total testis with TRIzol  reagent (Invitrogen Inc.) according to the manufacturer's guidelines. Total amount of RNA  was solubilized in RNAse free water and quantified using nanodrop for qPCR or  tapestation for RNA sequencing. mRNA was isolated from DNAse treated total RNA using the NEBNext rRNA depletion Kit (human, mouse, rat) from New England Biolabs (NEB) according to the manufacturer's instructions. Final elution was done in 5ul nuclease free water. Samples were then directly subjected to the workflow for strand specific RNA-Seq library preparation (NEBNext Ultra II Directional RNA Library Prep, NEB). For ligation custom adaptors were used (Adaptor-Oligo 1: 5'-ACA CTC TTT CCC TAC ACG ACG CTC TTC CGA TCT-3', Adaptor-Oligo 2: 5'-P-GAT CGG AAG AGC ACA CGT CTG AAC TCC AGT CAC-3'). After ligation adapters were depleted by a XP bead purification (Beckman Coulter) adding beads in a ratio of 1:0.9. Dual indexing was done during the following PCR enrichment (15 cycles, 65°C) using custom amplification primers carrying the index sequence indicated with 'NNNNNNN'. (Primer1: AAT GAT ACG GCG ACC ACC GAG ATC TAC ACT CTT TCC CTA CAC GAC GCT CTT CCG ATC T, primer2: CAA GCA GAA GAC GGC ATA CGA GAT NNNNNNNN GTG ACT GGA GTT CAG ACG TGT GCT CTT CCG ATC T). After two more XP bead purifications (1:0.9) libraries were quantified using the Fragment Analyzer (Agilent). Libraries were equimolarly pooled before sequencing them with a length of 75bp in single end mode on an Illumina NextSeq500 system to a depth of at least 40 mio reads.