Expression and putative functions of KIFC1 for nuclear reshaping and midpiece formation during spermiogenesis of Phascolosoma esculenta

Expression pattern and functional analysis of kinesin-14 KIFC1 in spermatogenesis of Macaca mulatta

C-terminal kinesin motor KIFC1 is increasingly concerned with an essential role in germ cell development. During the spermatogenesis of mice, rats, and crustaceans, KIFC1 functions in regulating meiotic chromosome separation, acrosome vesicle transportation, and nuclear morphology maintenance. The expression pattern of KIFC1 is conservatively concentrated at the acrosome and nucleus of haploid sperm cells. However, whether KIFC1 has similar functions in non-human primates remains unknown. In this study, we constructed the testis-specific cDNA library and cloned different transcripts of KIFC1 based on the genomic sequence. New variants of KIFC1 were identified, and showed different functional domains from the predicted isoforms. The spatio-temporal expression of KIFC1 proteins in seminiferous tubules of rhesus monkeys showed an obvious nuclear localization, specifically expressed in the spermatocytes and early haploid spermatids. The transcripts of KIFC1 also exhibited considerable expression in the nucleus of rhesus LLC-MK2 cells. Besides, we demonstrated that KIFC1 located at the acrosome and microtubule flagella of the mature sperm, and KIFC1 inhibition resulted in sperm tail deformation as well as increased the instability of head-to-tail connection. In summary, this study filled a gap in the reproductive research of the KIFC1 gene in non-human primates.

Expression Dynamics Indicate Potential Roles of KIF17 for Nuclear Reshaping and Tail Formation during Spermiogenesis in Phascolosoma esculenta

Kinesin family member17 (KIF17), a homologous dimer of the kinesin-2 protein family, has important microtubule-dependent and -independent roles in spermiogenesis. Little is known about KIF17 in the mollusk, Phascolosoma esculenta, a newly developed mariculture species in China. Here, we cloned the open reading frame of Pe-kif17 and its related gene, Pe-act, and performed bioinformatics analysis on both. Pe-KIF17 and Pe-ACT are structurally conserved, indicating that they may be functionally conserved. The expression pattern of kif17/act mRNA performed during spermiogenesis revealed their expression in diverse tissues, with the highest expression level in the coelomic fluid of P. esculenta. The expressions of Pe-kif17 and Pe-act mRNA were relatively high during the breeding season (July-September), suggesting that Pe-KIF17/ACT may be involved in spermatogenesis, particularly during spermiogenesis. Further analysis of Pe-kif17 mRNA via fluorescence in situ hybridization revealed the continuous expression of this mRNA during spermiogenesis, suggesting potential functions in this process. Immunofluorescence showed that Pe-KIF17 co-localized with α-tubulin and migrated from the perinuclear cytoplasm to one side of the spermatid, forming the sperm tail. Pe-KIF17 and Pe-ACT also colocalized. KIF17 may participate in spermiogenesis of P. esculenta, particularly in nuclear reshaping and tail formation by interacting with microtubule structures similar to the manchette. Moreover, Pe-KIF17 with Pe-ACT is also involved in nuclear reshaping and tail formation in the absence of microtubules. This study provides evidence for the role of KIF17 during spermiogenesis and provides theoretical data for studies of the reproductive biology of P. esculenta. These findings are important for spermatogenesis in mollusks.

Mitochondrial Features and Expressions of MFN2 and DRP1 during Spermiogenesis in Phascolosoma esculenta

Mitochondria can fuse or divide, a phenomenon known as mitochondrial dynamics, and their distribution within a cell changes according to the physiological status of the cell. However, the functions of mitochondrial dynamics during spermatogenesis in animals other than mammals and fruit flies are poorly understood. In this study, we analyzed mitochondrial distribution and morphology during spermiogenesis in Sipuncula (Phascolosoma esculenta) and investigated the expression dynamics of mitochondrial fusion-related protein MFN2 and fission-related protein DRP1 during spermiogenesis. The mitochondria, which were elliptic with abundant lamellar cristae, were mainly localized near the nucleus and distributed unilaterally in cells during most stages of spermiogenesis. Their major axis length, average diameter, cross-sectional area, and volume are significantly changed during spermiogenesis. mfn2 and drp1 mRNA and proteins were most highly expressed in coelomic fluid, a spermatid development site for male P. esculenta, and highly expressed in the breeding stage compared to in the non-breeding stage. MFN2 and DRP1 expression levels were higher in components with many spermatids than in spermatid-free components. Immunofluorescence revealed that MFN2 and DRP1 were consistently expressed and that MFN2 co-localizes with mitochondria during spermiogenesis. The results provide evidence for an important role of mitochondrial dynamics during spermiogenesis from morphology and molecular biology in P. esculenta, broadening insights into the role of mitochondrial dynamics in animal spermiogenesis.

Transcriptome analysis of the testes of male chickens with high and low sperm motility

The reproductive performance of chicken breeders has significant economic importance in the poultry industry, and sperm motility is an indicator of reproductive performance. This study performed RNA-seq of the testes of Gushi chicken roosters with high and low sperm motility and identified differentially expressed RNAs involved in sperm motility. RNA-seq analysis showed that 73 and 67 differentially expressed mRNAs were up- and downregulated, and 47 and 56 differentially expressed long non-coding RNAs were up- and downregulated, respectively. The genes related to sperm motility and spermatogenesis included KIFC1, KCNK2, and REC8. Functional enrichment analysis revealed that the pathways related to sperm motility included oxidative phosphorylation and glycine, serine, and threonine metabolism. In addition, the MSTRG.15920.1-REC8-MSTRG.11860.2-VWC2 pathway may regulate sperm motility. This study helped elucidate the molecular genetic mechanism of sperm motility in chicken.

Transport of Acrosomal Enzymes by KIFC1 via the Acroframosomal Cytoskeleton during Spermatogenesis in Macrobrachium rosenbergii (Crustacea, Decapoda, Malacostracea)

Simple Summary

In crustaceans, the sperm have no tail, and spermatogenesis consists only of acrosomal formation and nuclear deformation. The mechanism of acrosome formation during spermatogenesis of Macrobrachium rosenbergii is one of the hot topics in reproductive biology. Many motor proteins are involved in spermatogenesis. KIFC1, as a member of the kinesin family, is one of the motor proteins that our lab has been focusing on. The acrosome contains a large number of acrosomal enzymes for the hydrolysis of the egg envelope. In order to understand how these acrosomal enzymes are transported to the acrosome cap after synthesis, we cloned the KIFC1 and the Acrosin of M. rosenbergii. By detecting the localization of KIFC1 and Acrosin, we found that Mr-KIFC1 may be involved in acrosomal enzyme transport during spermiogenesis of M. rosenbergii. This study is to propose the function of KIFC1 to transport acrosomal enzymes along the acroframosome structure during crustacean spermatogenesis.

Abstract

The spermatogenesis of crustaceans includes nuclear deformation and acrosome formation. The mechanism of acrosome formation is one focus of reproductive biology. In this study, Macrobrachium rosenbergii was selected as the research object to explore the mechanism of acrosome formation. The acrosome contains a large number of acrosomal enzymes for the hydrolysis of the egg envelope. How these acrosomal enzymes are transported to the acrosomal site after synthesis is the key scientific question of this study. The acroframosome (AFS) structure of caridean sperm has been reported. We hypothesized that acrosomal enzymes may be transported along the AFS framework to the acrosome by motor proteins. To study this hypothesis, we obtained the full-length cDNA sequences of Mr-kifc1 and Mr-Acrosin from the testis of M. rosenbergii. The Mr-kifc1 and Mr-Acrosin mRNA expression levels were highest in testis. We detected the distribution of Mr-KIFC1 and its colocalization with Mr-Acrosin during spermatogenesis by immunofluorescence. The colocalization of Mr-KIFC1 and microtubule indicated that Mr-KIFC1 may participate in sperm acrosome formation and nucleus maturation. The colocalization of Mr-KIFC1 and Mr-Acrosin indicated that Mr-KIFC1 may be involved in Acrosin transport during spermiogenesis of M. rosenbergii. These results suggest that Mr-KIFC1 may be involved in acrosomal enzymes transport during spermiogenesis of M. rosenbergii.

Cloning, Functional Characterization and Response to Cadmium Stress of the Thioredoxin-like Protein 1 Gene from Phascolosoma esculenta

Cadmium (Cd) is a heavy metal toxicant and is widely distributed in aquatic environments. It can cause excessive production of reactive oxygen species (ROS) in the organism, which in turn leads to a series of oxidative damages. Thioredoxin (Trx), a highly conserved disulfide reductase, plays an important role in maintaining the intracellular redox homeostasis in eukaryotes and prokaryotes. Phascolosoma esculenta is an edible marine worm, an invertebrate that is extensively found on the mudflats of coastal China. To explore the molecular response of Trx in mudflat organisms under Cd stress, we identified a new Trx isoform (Trx-like protein 1 gene) from P. esculenta for the first time, designated as PeTrxl. Molecular and structural characterization, as well as multiple sequence and phylogenetic tree analysis, demonstrated that PeTrxl belongs to the Trx superfamily. PeTrxl transcripts were found to be ubiquitous in all tissues, and the highest expression level occurred in the coelomic fluid. Exposure to three sublethal concentrations of Cd resulted in the upregulation and then downregulation of PeTrxl expression levels over time in coelomic fluid of P. esculenta. The significant elevation of PeTrxl expression after 12 and 24 h of Cd exposure at 6 and 96 mg/L, respectively, might reflect its important role in the resistance to Cd stress. Recombinant PeTrxl (rPeTrxl) showed prominent dose-dependent insulin-reducing and ABTS free radical-scavenging abilities. After exposure to 96 mg/L Cd for 24 h, the ROS level increased significantly in the coelomic fluid, suggesting that Cd induced oxidative stress in P. esculenta. Furthermore, the injection of rPeTrxl during Cd exposure significantly reduced the ROS in the coelomic fluid. Our data suggest that PeTrxl has significant antioxidant capacity and can protect P. esculenta from Cd-induced oxidative stress.

Characterisation, expression and possible functions of prohibitin during spermatogenesis in the silver pomfret Pampus argenteus

Mitochondria play an important role in spermatogenesis, and some mitochondrial proteins are specifically related to this process. In this study we investigated the cytological characteristics of spermatogenic cells, including mitochondrial dynamics, during spermatogenesis in Pampus argenteus. In addition, we characterised the mitochondria-related protein prohibitin (PHB), which has been reported to play roles in mitochondrial dynamics and animal fertility. The full-length cDNA of the P. argenteus phb gene (Pa-phb) is 1687bp, including a 102-bp 5'-untranslated region (UTR), a 772-bp 3'-UTR and an 813-bp open reading frame encoding 271 amino acids. The predicted P. argenteus PHB protein (Pa-PHB) contains three functional domains (a transmembrane domain, an SPFH domain (the conserved region of stomatins, prohibitins, flotillins and HflK/C) and a coiled-coil domain) and exhibits high similarity with its homologue in other animals. The Pa-phb gene was widely expressed in all tissues examined, especially the liver and heart. We primarily focused on Pa-phb expression during spermatogenesis after observing the cytological features of male germ cells, and found that Pa-phb transcripts were detected throughout the course of development of male germ cells. Notably, we observed colocalised signals of Pa-PHB and mitochondria, which were distributed in the cytoplasm around the nucleus in spermatogonia, spermatocytes and early spermatids, tended to move to one side of the cell in middle spermatids and, finally, were colocalised in the sperm midpiece. These observations indicate that Pa-PHB is primarily localised in mitochondria during spermatogenesis, indicating that it has a role in mitochondria. Based on the results of this and previous studies regarding the essential roles of PHB in mitochondria and spermatogenesis in animals, we propose a functional model for PHB during spermatogenesis, including possible roles in the proliferation of spermatogonia and in the regulation of mitochondrial morphology and function in spermatogenic cells.

KIFC1 functions in nuclear reshaping and midpiece formation during the spermatogenesis of small yellow croaker Larimichthys polyactis

The C-terminal kinesin motor protein (KIFC1) has essential functions in spermatogenesis. To evaluate molecular mechanisms of KIFC1 during teleost fish spermatogenesis, there was cloning and sequencing the kifc1 cDNA in the testis of Larimichthys polyactis. Quantitative PCR results indicated there were Lp-kifc1 mRNA transcripts in the testes. Results from conducting fluorescence in situ hybridization and immunofluorescence procedures indicated there were trends in relative abundance changes in Lp-kifc1 mRNA transcripts that were associated with abundance of Lp-KIFC1 protein during spermatogenesis. The Lp-KIFC1 protein was detected at all stages of spermatogenesis. There was minimal Lp-KIFC1 in the cytoplasm of spermatogonia, with content being greater and concentrated in the perinuclear region in spermatocytes and during early/mid-stages of development of spermatids. There were large abundances of Lp-KIFC1 in spermatids at the mid-developmental stage. In late-developing spermatids, Lp-KIFC1 content was less and concentrated in the bottom of the nucleus, where the midpiece formed. There was a small Lp-KIFC1 in the midpiece of mature sperm. These findings indicate Lp-KIFC1 may have functions in L. polyactis spermatogenesis. Results from conducting immunofluorescence procedures indicated Lp-KIFC1 was co-localized microtubules and mitochondria throughout spermatogenesis. There were large abundances of Lp-KIFC1 and tubulin in spermatids during the mid-developmental stage, when there is a decrease in size and reshaping of the nucleus. During midpiece formation, there was co-localization of the Lp-KIFC1 and mitochondria in the spermatid perinuclear region to the midpiece. These findings indicate Lp-KIFC1 is involved in nuclear reshaping and midpiece formation during spermatogenesis in L. polyactis.

Cytological features of spermatogenesis in Opsariichthys bidens (Teleostei, Cyprinidae)

Spermatogenesis is important for male fertility, but has not been well-studied in Opsariichthys bidens, an economically important freshwater fish in China. In this study, there was investigation of the cytological features of spermatogenesis in O. bidens using light microscopy, transmission electron microscopy, and immunofluorescence detection of microtubules. O. bidens has tubular testis. Spermatogenesis in O. bidens is of the cystic type, in which the spermatogenic cells develop into spermatozoa in cysts. There was asynchronous development of primary spermatocytes within a single cyst. Spermiogenesis was classified as Type I, which develops into a Type I aquasperm with an oval nucleus, a small and simple midpiece, a flagellum and no acrosome. There was a nuage in spermatogonia, spermatocytes, and spermatids in different developmental stages of spermatids which may have important functions in fish spermatogenesis. Furthermore, microtubule dynamics may be involved in spermatid reshaping, material transport, and polar distribution of organelles during spermiogenesis.

KIFC1 is essential for normal spermatogenesis and its depletion results in early germ cell apoptosis in the Kuruma shrimp, Penaeus (Marsupenaeus) japonicus

In order to explore the dynamic mechanisms during spermatogenesis of the penaeid prawns, the full length of kifc1 was cloned from testis cDNA of Penaeus japonicus through RACE. Both semi-quantitative RT-PCR and Western blot results indicated that KIFC1 was extensive expressed in different tissue of P. japonicus. Compared with other tissue, the highest expression of KIFC1 occurred in the testis. According to the immunofluorescence results, the KIFC1 protein was detected at each stage of whole process of spermatogenesis. In the spermatogonial phase, KIFC1 mainly dispersed in cytoplasm and co-localized with microtubules, while abundant KIFC1 signal was detected in the nucleus of spermatocytes. At the early stage of spermatids, KIFC1 was transported from the nucleus into the cytoplasm, and it assisted microtubule assembly onto one side of the nucleus. Finally, in mature sperm, it was weakly expressed in the acrosome. This implies that KIFC1 may participate in the mitosis of spermatogonia, meiosis of spermatocyte, and acrosome formation during spermiogenesis; it may also play functions in acrosome maintaining in mature sperm. In addition, the results of KIFC1 knockdown by dsRNA injection in vivo reveal that decreased KIFC1 expression may induce aberrant microtubule assembly, and it leads to spermatogonia and spermatocyte apoptosis.