Deletion of a Seminal Gene Cluster Reinforces a Crucial Role of SVS2 in Male Fertility

Multiple genes, whose functions or expression are overlapping, compensate for the loss of one gene. A gene clusterin the mouse genome encodes five seminal vesicleproteins (SVS2, SVS3, SVS4, SVS5, and SVS6). These proteins are produced by male rodents and function in formation of the copulatory plug following mating. SVS2 plays an essential role in the successful internal fertilizationby protecting the sperm membrane against a uterine immune attack. We hypothesized that the four remaining seminal vesicleproteins (SVPs) of this gene clustermay partially/completely compensate for the deficiency of SVS2. For confirming our hypothesis, we generated mice lacking the entire SVP-encoding gene clusterand compared their fecunditywith Svs2-deficient (Svs2−/−) mice; that is, mice deficient in Svs2 alone. A single loxP site remained after the deletion of the Svs2 gene. Therefore, we inserted another loxP site by combining the CRISPR/ Cas9system with single-stranded oligodeoxynucleotides (ssODN). Male mice lacking the entire SVP-encoding gene cluster(Svs2–6−/− mice) and thereby all five SVP proteins, generated by the deletion of 100kbp genomic DNA, showed low fecundity. However, the fecunditylevel was comparable with that from Svs2−/− male mice. Our results demonstrate that SVS3, SVS4, SVS5, and SVS6 do not function in the protection of sperm against a uterine immune attack in the absence of SVS2. Thus, Svs2 is the critical gene in the SVP gene cluster.