SPAG4L/SPAG4Lβ interacts with Nesprin2 to participate in the meiosis of spermatogenesis.

SUN domain proteins are identified as a novel family of nuclear envelope proteins which are involved in spermatogenesis. SPAG4L is identified as the fifth member of this family. Previous studies have revealed that SPAG4L is involved in spermatogenesis and the mutations occurring in SPAG4L will lead to male infertility. However, the transcriptions of SPAG4L and its interacting proteins in the testis are still unclear. In this study, we identified a shorter transcript variant of SPAG4L, named SPAG4Lβ, in human testis by northern blot and reverse transcription-polymerase chain reaction. Bioinformatics analysis showed that it encodes a protein consisting of 311 amino acids, and subcellular localization analysis revealed that it is mainly expressed in the cytoplasm. In situ hybridization and immunofluorescence assay revealed that SPAG4L/SPAG4Lβ is involved in meiosis. Furthermore, co-IP results demonstrated that SPAG4L/SPAG4Lβ interacts with Nesprin2, a KASH domain protein to form the LINC (linker of nucleoskeleton and cytoskeleton) complexes. Immunofluorescence results revealed that the LINC complexes of Spag4l/Nesprin2 in mouse are involved in spermatocyte division. Our data indicated that SPAG4L/SPAG4Lβ may play an important role in the meiotic process.