Rec8 cohesin-mediated loop-axis chromatin architecture is required for meiotic recombination

During meiotic prophase, cohesin-dependent axial structures are formed in the synaptonemal complex (SC). However, functional correlation between these structure formation and cohesion remains elusive. Here we examined formation of the cohesin-dependent axial structure in fission yeast, which forms atypical SCs composed of linear elements (LinEs) resembling the lateral elements of SC but lacking the central elements, and found that Rec8 cohesin is crucial for the formation of the loop-axis structure within the atypical SC. Furthermore, the Rec8-mediated loop-axis structure is formed in the absence of LinEs, and provides a structural platform for aligning homologous chromosomes. We also succeeded to identify a rec8 mutant that lost the ability of assembling the loop-axis structure without losing cohesion. Remarkably, this mutant showed defects in LinE assembly, resulting in great reduction of meiotic recombination. Collectively, our results demonstrate an essential role of the Rec8-dependent loop-axis structure in LinE assembly, facilitating meiotic recombination. Overall design: Hi-C experiment during meiosis of fission yeast