Expression and potential functions of KIF3A/3B to promote nuclear reshaping and tail formation during Larimichthys polyactis spermiogenesis
KIF3A and KIF3B are homologous motor subunits of the Kinesin II protein family. KIF3A, KIF3B, and KAP3 form a heterotrimeric complex and play a significant role in spermatogenesis. Here, we first cloned full-length kif3a/3b cDNAs from Larimichthys polyactis. Lp-kif3a/3b are highly related to their homologs in other animals. The proteins are composed of three domains, an N-terminal head domain, a central stalk domain, and a C-terminus tail domain. Lp-kif3a/3b mRNAs were found to be ubiquitously expressed in the examined tissues, with high expression in the testis. Fluorescence in situ hybridization (FISH) was used to analyze the expression of Lp-kif3a/3b mRNAs during spermiogenesis. The results showed that Lp-kif3a/3b mRNAs had similar expression pattern and were continuously expressed during spermiogenesis. From middle spermatid to mature sperm, Lp-kif3a/3b mRNAs gradually localized to the side of the spermatid where the midpiece and tail form. In addition, we used immunofluorescence (IF) to observe that Lp-KIF3A protein co-localizes with tubulin during spermiogenesis. In early spermatid, Lp-KIF3A protein and microtubule signals were randomly distributed in the cytoplasm. In middle spermatid, however, the protein was detected primarily around the nucleus. In late spermatid, the protein migrated primarily to one side of the nucleus where the tail forms. In mature sperm, Lp-KIF3A and microtubules accumulated in the midpiece. Moreover, Lp-KIF3A co-localized with the mitochondria. In mature sperm, Lp-KIF3A and mitochondria were present in the midpiece. Therefore, Lp-KIF3A/KIF3B may be involved in spermiogenesis in L. polyactis, particularly during nuclear reshaping and tail formation.
KeywordsKIF3A/3B Spermiogenesis Larimichthys polyactis Nuclear reshaping Tail formation
We are indebted to all members of the Fish Reproduction Physiology Laboratory at Ningbo University and the Sperm Laboratory at Zhejiang University for their enlightening discussions. This project was supported by the Scientific and Technical Project of Zhejiang Province (No. 2017C02013), the NSFC–Zhejiang Joint Fund for the Integration of Industrialization and Informatization (No. U1809212), the National Natural Science Foundation of China (No. 31602140, 31272642), the Collaborative Innovation Center for Zhejiang Marine High-Efficiency and Healthy Aquaculture, and the K.C. Wong Magna Fund in Ningbo University.
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