RAD21 and neural tube defect: Loop extrusion is mediated by cohesion, and CTCF mediates the formation of chromatin loops and self‐interacting TADs.[21] The cohesion complex is an important architectural protein that organizes the 3D genome and is necessary for DSB repair.[22] To investigate the relationship between chromatin loops and DSBs during neural tube closure, we examined the expression of the cohesion subunit RAD21 and the DNA damage marker gH2AX in E9.5 NTD embryos using immunofluorescence staining.