Squash preparations were performed as described previously (Kotaja et al. 2004 ). Germ cells were spread out of seminiferous tubules to mono-layers, snap-frozen in liquid nitrogen and fixed in 4% PFA. After washing three times in PBS, germ cells were treated with 0.1% Triton X-100 (Sigma) in PBS for 5 min and then incubated for 1 h in 0.5% BSA in PBS. Cells were incubated with primary antibodies: rabbit anti-KSRP (Bethyl Laboratories, Montogomery, AL), rabbit anti-DDX5 (Bethyl Laboratories) in dilution 1:200 overnight at 4°C.
For paraffin-embedded testes slides, IF analysis was performed as described by Liang and coworkers (Liang et al. 2011) . The primary antibodies of mouse anti-MVH (Abcam) and rabbit anti-KSRP (Bethyl Laboratories) were used in dilution 1:200. Alexa Fluor 488/555 conjugated secondary antibodies (Life Technologies) were used in dilution 1:200. Nuclei were stained with Hoechst 33342 (Sigma). Fluorescent signals were observed using an epifluorescence microscope (Eclipse 80i, Nikon).
For paraffin-embedded testes slides, IF analysis was performed as described by Liang and coworkers (Liang et al. 2011) . The primary antibodies of mouse anti-MVH (Abcam) and rabbit anti-KSRP (Bethyl Laboratories) were used in dilution 1:200. Alexa Fluor 488/555 conjugated secondary antibodies (Life Technologies) were used in dilution 1:200. Nuclei were stained with Hoechst 33342 (Sigma). Fluorescent signals were observed using an epifluorescence microscope (Eclipse 80i, Nikon).