Transient X self-synapsis during pachytene in dog spermatocytes. A) Subregions of spermatocyte spread nuclei containing the X and Y at different substages of pachytene indicated on the left are shown at high resolution (Structured Illumination Microscopy (SIM)) to resolve the lateral elements of the synaptonemal complex immunostained for SYCP3 (white/green). The nuclei are costained for SYCP1 to identify regions of synapsis. To the right, drawings showing in white the X-specific and the Y-specific regions, in light blue PAR homologous synapsis and in red X chromosome heterologous self-synapsis. Bar represents 1 μm. B) As in A, but these nuclei were stained with antibodies against TEX12 (marker of synapsis), HORMAD1/2 (specifically localizes on unsynapsed axes) and CREST (to mark the centromeres) as indicated. To the right, drawings showing in white the X-specific and the Y-specific region , in light blue PAR homologous synapsis, in green X chromosome heterologous self-synapsis, and in orange the centromere locations. Scale bar represents 1 μm.