Testis-specific fascin component FSCN3 is dispensable for mouse spermatogenesis and fertility

Background Fascins belong to a family of actin-bundling proteins that are involved in a wide range of biological functions. FSCN3, a newly identified testis-specific actin-bundling protein, is specifically expressed in elongated spermatids. However, its in vivo function in mouse spermiogenesis remains unknown. Methods and results We generated Fscn3 knockout mice through CRISPR/Cas9 gene-editing technology. Fscn3 −/− mice displayed normal testis morphology and testis to bodyweight ratio, and sperm concentrations did not differ significantly between Fscn3 + / + and Fscn3 −/− mice. Fertility assays consistently revealed that Fscn3 −/− mice are completely fertile and their reproductive status does not differ from that of wild-type. Moreover, hematoxylin and eosin staining of the testis sections of Fscn3 −/− mice detected various germ cells, ranging from spermatogonia to mature spermatozoa. Furthermore, the swimming velocity of the sperm of Fscn3 −/− mice was comparable to that of their wild-type littermates. Both Fscn3 + / + and Fscn3 −/− mice had normal sperm morphology, indicating that the disruption of Fscn3 does not affect sperm morphology. The analysis of meiotic prophase I progression demonstrated normal prophase-I phases (leptonema to diplonema) in both Fscn3 + / + and Fscn3 −/− mice, suggesting that Fscn3 is not essential for meiosis I. Conclusion Our study provides the first evidence that FSCN3 is a testis-specific actin-bundling protein that is not required for mouse spermatogenesis. Our results will help reproductive biologists focus their efforts on genes that are crucial for fertility and avoid research duplication.