RNF212 is required for chiasma formation and assembly of crossover-specific recombination complexes. (a–c) Chromosome spreads of cells in diakinesis/metaphase I stained with Giemsa from wild-type (a) and Rnf212−/− (b,c) mice. (b) Nucleus with no chiasmata. (c) Nucleus with a single chiasmate bivalent (highlighted by an arrow). (d–k) Pachytene spermatocytes. (d–g) Wild-type cells immunostained for MLH1 and SYCP3 (d), MLH1 and SYCP3 (e) or CDK2 and SYCP3 (f). (g) Magnified view of a chromosome from f. (h–k) Rnf212−/− cells immunostained for MLH1 and SYCP3 (h), MLH3 and SYCP3 (i) or CDK2 and SYCP3 (j). (k) Magnified view of a chromosome from j. The arrowheads and arrow (f,g) highlight interstitial CDK2 foci. Scale bars, 10 μm in a–f,h–j and 1 μm in g,k.