RAD21L is transcribed abundantly in testis and localized to the lateral and axial elements of the synaptonemal complex playing an essential role in homologous chromosome synapsis during meiotic prophase I. Male mice deficient in RAD21L are defective in homologous chromosome synapsis which in turn leads to zygonema arrest and subsequent azoospermia with male sterility in mice (Herran et al., 2011). The gene discussed is RAD21L1; the disease is Azoospermia.