Immunofluorescence on sections and on surface-spread testicular cells were performed as previously described.15 (link), 65 (link) Antibody against DOT1L (ab-64077 from Abcam), H3K79me2 (ab-3594 from Abcam) or AcH4 (06-866 from Millipore) were diluted 1/100 to 1/200. Pictures were taken with an Olympus BX63 microscope. Quantification was performed on pictures obtained from six samples per genotype using ImageJ 1.48v (http://imagej.nih.gov/ij/). T-tests were performed with GraphPad Prism 5.02.