Figure 4.

Meiotic DNA Double-Strand Breaks Are Initiated but No Crossovers Are Formed In Vitro

(A and B) DSBs marked by RAD51 (A) are initiated in in vitro-generated leptotene spermatocytes but are not completely resolved at the pachytene-like stage. Stained for SYCP3 (green), RAD51 (red), centromeres (CREST, white), and DNA (DAPI, blue in merged images). Regions inside dashed boxes are shown at higher magnification in the following image. Meiotic crossovers marked by MLH1 (B) are not formed in vitro (top) as compared with in vivo (bottom); SYCP3 (red) and MLH1 (green).

(C) Karyotype of in vitro-generated meiotic M-phase cells displaying univalents (pairs of sister chromosomes). Scale bars, 5 μm.