Involvement of the fusome-related protein Add1 in spermatogenesis of the Chinese mitten crab ( Eriocheir sinensis ) by organization of cytoskeleton

The sperm nucleus of the decapod crustacean Chinese mitten crab, Eriocheir sinensis , is loose and fibrous, which is a non-condensed nucleus. Our purpose was to analyze the structural distribution of the fusome-related protein Add1 during the spermatogenesis in E. sinensis to better understand the non-condensed nucleus of E. sinensis . RT-qPCR and western blot results showed that Add1 was expressed at the transcriptional and translational level during spermatogenesis of E. sinensis . Immunofluorescence results showed that Add1 was widely distributed in the process of spermatogenesis, including spermatogonia, spermatocytes, spermatids, and sperm. In the initial stage of sperm nucleus decondensation of E. sinensis , Add1 was widely expressed in the cytoplasm of spermatogonia. In the process from stage III spermatids to sperm, Add1 is mainly expressed in the nucleus. With the continuous differentiation of cells, Add1 gradually transferred from the cytoplasm to the nucleus. Our results indicated that the fusome-related protein Add1 might be involved in the spermiogenesis through the construction of a new nuclear skeleton to participate in the decondensation of sperm nuclei and the maintenance and protection of non-condensed chromatin.