The molecular motor KIFC1 associates with a complex containing nucleoporin NUP62 that is regulated during development and by the small GTPase RAN

Screening of Reference Genes for Quantitative Real-Time PCR Analysis in Tissues and during Testis Development, and Application to Analyze the Expression of kifc1 in Hemibarbus labeo (Teleostei, Cypriniformes, Cyprinidae)

The selection of proper reference genes is vital for ensuring precise quantitative real-time PCR (qPCR) assays. This study evaluates the stability of the expression of nine candidate reference genes in different tissues and during testicular development in H. labeo. The results show that eef1a is recommended as a reference gene for qPCR analysis in tissues and during testicular development. Furthermore, we evaluated the optimal number of reference genes needed when calculating gene expression levels using the geomean method, revealing that two reference genes are sufficient. Specifically, eef1a and rps27 are recommended for analysis of gene expression in tissues, whereas eef1a and actb are advised for evaluating gene expression during testicular development. In addition, we examined the expression pattern of kifc1, a kinesin involved in the reshaping of spermatids. We detected peak expression levels of kifc1 in testes, with its expression initially increasing before decreasing throughout testicular development. The highest expression of kifc1 was observed in stage IV testes, the active period of spermiogenesis, suggesting a possible role for kifc1 in the regulation of the reshaping of spermatids and hence testicular development. This study represents the first investigation of reference genes for H. labeo, providing a foundation for studying gene expression patterns and investigating gene expression regulation during testicular development.

Kinesin-14 KIFC1 promotes acrosome formation and chromatin maturation during mouse spermiogenesis

KIFC1, a member of kinesin-14 subfamily motors, is essential for meiotic cell division and acrosome formation during spermatogenesis. However, the functions of KIFC1 in the formation and maintenance of the acrosome in male germ cells remain to be elucidated. In this study, we report the structural deformities of acrosomes in the in vivo KIFC1 inhibition mouse models. The proacrosomal vesicles diffuse into the cytoplasm and form atypical acrosomal granules. This phenotype is consistent with globozoospermia patients and probably results from the failure of the Golgi-derived vesicle trafficking and actin filament organization. Moreover, the multinucleated and undifferentiated spermatogenic cells in the epidydimal lumen after KIFC1 inhibition reveal the specific roles of KIFC1 in regulating post-meiotic maturation. Overall, our results uncover KIFC1 as an essential regulator in the trafficking, fusion and maturation of acrosomal vesicles during spermiogenesis.

DNALI1 interacts with the MEIG1/PACRG complex within the manchette and is required for proper sperm flagellum assembly in mice

The manchette is a transient and unique structure present in elongating spermatids and required for proper differentiation of the germ cells during spermatogenesis. Previous work indicated that the MEIG1/PACRG complex locates in the manchette and is involved in the transport of cargos, such as SPAG16L, to build the sperm flagellum. Here, using co-immunoprecipitation and pull-down approaches in various cell systems, we established that DNALI1, an axonemal component originally cloned from Chlamydomonas reinhardtii, recruits and stabilizes PACRG and we confirm in vivo, the co-localization of DNALI1 and PACRG in the manchette by immunofluorescence of elongating murine spermatids. We next generated mice with a specific deficiency of DNALI1 in male germ cells, and observed a dramatic reduction of the sperm cells, which results in male infertility. In addition, we observed that the majority of the sperm cells exhibited abnormal morphology including misshapen heads, bent tails, enlarged midpiece, discontinuous accessory structure, emphasizing the importance of DNALI1 in sperm differentiation. Examination of testis histology confirmed impaired spermiogenesis in the mutant mice. Importantly, while testicular levels of MEIG1, PACRG, and SPAG16L proteins were unchanged in the Dnali1 mutant mice, their localization within the manchette was greatly affected, indicating that DNALI1 is required for the formation of the MEIG1/PACRG complex within the manchette. Interestingly, in contrast to MEIG1 and PACRG-deficient mice, the DNALI1-deficient mice also showed impaired sperm spermiation/individualization, suggesting additional functions beyond its involvement in the manchette structure. Overall, our work identifies DNALI1 as a protein required for sperm development.

Expression of kinesin family member C1 in pancreatic ductal adenocarcinoma affects tumor progression and stemness

Pancreatic ductal adenocarcinoma (PDAC) is an aggressive cancer and the third leading cause of cancer-related deaths. Therefore, there is an urgent need for a novel molecular target for the treatment of PDAC. Kinesin family member C1 (KIFC1) belongs to the kinesin superfamily proteins and has been reported to be involved in the pathogenesis of a wide variety of carcinomas. However, the role of KIFC1 in PDAC remains unknown. This study aimed to analyze the expression and biological function of KIFC1 in PDAC. Immunohistochemically, KIFC1 was found in 37 of 81 PDAC cases (46%). A high expression of KIFC1 was significantly related to tumor size (p = 0.023) and poor overall survival (p = 0.011). Univariate and multivariate analysis indicated that KIFC1 expression was a prognostic factor in PDAC cases. As for cancer stem cell markers, KIFC1 expression tended to co-express significantly with CD44 (p < 0.01). The growth and spheroid colony formation of KIFC1 small interfering RNA (siRNA)-transfected PDAC cells were significantly lower than those of negative control siRNA-transfected cells. Therefore, our findings suggest that KIFC1 is an independent prognostic factor in PDAC and may represent a new promising therapeutic target in PDAC.

Kinesins in Mammalian Spermatogenesis and Germ Cell Transport

In mammalian testes, the apical cytoplasm of each Sertoli cell holds up to several dozens of germ cells, especially spermatids that are transported up and down the seminiferous epithelium. The blood-testis barrier (BTB) established by neighboring Sertoli cells in the basal compartment restructures on a regular basis to allow preleptotene/leptotene spermatocytes to pass through. The timely transfer of germ cells and other cellular organelles such as residual bodies, phagosomes, and lysosomes across the epithelium to facilitate spermatogenesis is important and requires the microtubule-based cytoskeleton in Sertoli cells. Kinesins, a superfamily of the microtubule-dependent motor proteins, are abundantly and preferentially expressed in the testis, but their functions are poorly understood. This review summarizes recent findings on kinesins in mammalian spermatogenesis, highlighting their potential role in germ cell traversing through the BTB and the remodeling of Sertoli cell-spermatid junctions to advance spermatid transport. The possibility of kinesins acting as a mediator and/or synchronizer for cell cycle progression, germ cell transit, and junctional rearrangement and turnover is also discussed. We mostly cover findings in rodents, but we also make special remarks regarding humans. We anticipate that this information will provide a framework for future research in the field.

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.

Molecular characterization, dynamic transcription, and potential function of KIF3A/KIF3B during spermiogenesis in Opsariichthys bidens

Spermiogenesis is the final phase of spermatogenesis, wherein the spermatids differentiate into mature spermatozoa via complex morphological transformation. In this process, kinesin plays an important role. Here, we observed the morphological transformation of spermatids and analyzed the characterization, dynamic transcription, and potential function of kinesin KIF3A/KIF3B during spermiogenesis in Chinese hook snout carp (Opsariichthys bidens). We found that the full-length cDNAs of O. bidens kif3a and kif3b were 2544 and 2806 bp in length comprising 119 bp and 259 bp 5' untranslated region (UTR), 313 bp and 222 bp 3' UTR, and 2112 bp and 2325 bp open reading frame encoding 703 and 774 amino acids, respectively. Ob-KIF3A/KIF3B proteins have three domains, namely N-terminal head, coiled-coil stalk, and C-terminal tail, and exhibit high similarity with homologous proteins in vertebrates and invertebrates. Ob-kif3a/kif3b mRNAs were ubiquitously expressed in all tissues examined, with the highest expression in the brain and stage-IV testis. Immunofluorescence results showed that Ob-KIF3A was co-localized with tubulin and the mitochondria. Particularly, in early spermatids, Ob-KIF3A, tubulin, and the mitochondrial signals were evenly distributed in the cytoplasm, whereas in middle spermatids, they were distributed around the nucleus. In the late stage, the signals were concentrated on one side of the nucleus, where the tail is formed, whereas in mature sperms, they were detected in the midpiece and flagellum. These results indicate that Ob-KIF3A/KIF3B may participate in nuclear reshaping, flagellum formation, and mitochondrial aggregation in the midpiece during spermiogenesis.

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.

Sperm Differentiation: The Role of Trafficking of Proteins

Sperm differentiation encompasses a complex sequence of morphological changes that takes place in the seminiferous epithelium. In this process, haploid round spermatids undergo substantial structural and functional alterations, resulting in highly polarized sperm. Hallmark changes during the differentiation process include the formation of new organelles, chromatin condensation and nuclear shaping, elimination of residual cytoplasm, and assembly of the sperm flagella. To achieve these transformations, spermatids have unique mechanisms for protein trafficking that operate in a coordinated fashion. Microtubules and filaments of actin are the main tracks used to facilitate the transport mechanisms, assisted by motor and non-motor proteins, for delivery of vesicular and non-vesicular cargos to specific sites. This review integrates recent findings regarding the role of protein trafficking in sperm differentiation. Although a complete characterization of the interactome of proteins involved in these temporal and spatial processes is not yet known, we propose a model based on the current literature as a framework for future investigations.

Kinesin Family Member C1 (KIFC1) Accelerates Proliferation and Invasion of Endometrial Cancer Cells Through Modulating the PI3K/AKT Signaling Pathway

Endometrial cancer (EC) is one of the most common cancers among women worldwide. Kinesin family member C1 (KIFC1) has been demonstrated to play crucial roles in various tumors. However, the function of KIFC1 in EC remains to be revealed. In this study, upregulation of KIFC1 expression in human EC tissues was found from analysis on data from The Cancer Genome Atlas (TCGA), and positively correlated with short survival outcome of EC patients. In addition, the mRNA and protein levels of KIFC1 were confirmed to be up-regulated in EC cells (Ishikawa, HEC-1B, HEC-1A and KLE) compared to human normal endometrial stromal cells (hESCs) by quantitative real time PCR and western blot. In vitro functional experiments showed that overexpression of KIFC1 promoted proliferation, migration and invasion of EC cells, while KIFC1 depletion showed the opposite results. Moreover, KIFC1 knockdown suppressed tumor growth in mice. Further mechanism analysis showed that KIFC1 participated in the regulation of EC progression through regulating the PI3K/AKT signaling pathway. Collectively, KIFC1 promoted proliferation and invasion through modulating PI3K/AKT signaling pathway in EC, implying that KIFC1 might provide a promising therapeutic target for the therapy of EC.

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.

DYT1 Dystonia Patient-Derived Fibroblasts Have Increased Deformability and Susceptibility to Damage by Mechanical Forces

DYT1 dystonia is a neurological movement disorder that is caused by a loss-of-function mutation in the DYT1/TOR1A gene, which encodes torsinA, a conserved luminal ATPases-associated with various cellular activities (AAA+) protein. TorsinA is required for the assembly of functional linker of nucleoskeleton and cytoskeleton (LINC) complexes, and consequently the mechanical integration of the nucleus and the cytoskeleton. Despite the potential implications of altered mechanobiology in dystonia pathogenesis, the role of torsinA in regulating cellular mechanical phenotype, or mechanotype, in DYT1 dystonia remains unknown. Here, we define the deformability of mouse fibroblasts lacking functional torsinA as well as human fibroblasts isolated from DYT1 dystonia patients. We find that the deletion of torsinA or the expression of torsinA containing the DYT1 dystonia-causing ΔE302/303 (ΔE) mutation results in more deformable cells. We observe a similar increased deformability of mouse fibroblasts that lack lamina-associated polypeptide 1 (LAP1), which interacts with and stimulates the ATPase activity of torsinA in vitro, as well as with the absence of the LINC complex proteins, Sad1/UNC-84 1 (SUN1) and SUN2, lamin A/C, or lamin B1. Consistent with these findings, we also determine that DYT1 dystonia patient-derived fibroblasts are more compliant than fibroblasts isolated from unafflicted individuals. DYT1 dystonia patient-derived fibroblasts also exhibit increased nuclear strain and decreased viability following mechanical stretch. Taken together, our results establish the foundation for future mechanistic studies of the role of cellular mechanotype and LINC-dependent nuclear-cytoskeletal coupling in regulating cell survival following exposure to mechanical stresses.

Kinesin-14 motor protein KIFC1 participates in DNA synthesis and chromatin maintenance

The nuclear localization signal (NLS) in kinesin-14 KIFC1 is associated with nuclear importins and Ran gradient, but detailed mechanism remains unknown. In this study, we found that KIFC1 proteins have specific transport characteristics during cell cycle. In the absence of KIFC1, cell cycle kinetics decrease significantly with a prolonged S phase. After KIFC1 overexpression, the duration of S phase becomes shorten. KIFC1 may transport the recombinant/replicate-related proteins into the nucleus, meanwhile avoiding excessive KIFC1 in the cytoplasm, which results in aberrant microtubule bundling. Interestingly, the deletion of kifc1 in human cells results in a higher ratio of aberrant nuclear membrane, and the degradation of lamin B and lamin A/C. We also found that kifc1 deletion leads to defects in metaphase mitotic spindle assembly, and then results in chromosome structural abnormality. The kifc1^-/- cells finally form micronuclei in daughter cells, and results in aneuploidy and chromosome loss in cell cycle. In this study, we demonstrate that kinesin-14 KIFC1 proteins involve in regulating DNA synthesis in S phase, and chromatin maintenance in mitosis, and maintain cell growth in a nuclear transport-independent way.

KIFC1, a novel potential prognostic factor and therapeutic target in hepatocellular carcinoma

Kinesin family member C1 (KIFC1, also known as HSET) is a minus end-directed motor protein, which is critical in centrosome clustering. The present study investigated the expression of KIFC1 in paired hepatocellular carcinoma (HCC) tissues and adjacent non-cancerous tissues from 91 patients by immunohistochemical analysis; clinical data were concomitantly collected. KIFC1 was expressed at high levels in HCC tissues, compared with that in peritumoral tissues (54.9 vs. 14.3%; P<0.01), and its expression correlated with tumor emboli, metastasis, recurrence and time of recurrence. Kaplan-Meier analysis showed that the expression of KIFC1 was significantly associated with tumor-free survival rates. In addition, multivariate analyses revealed that the overexpression of KIFC1was an independent predictive marker in patients with HCC. Consistently, data derived from GEPIA was in agreement with the results. In vitro, KIFC1 knockdown effectively decreased HCC cell viability, and induced apoptosis and cell death. KIFC1 knockdown also significantly suppressed tumor cell migration and invasion in vitro. Mechanistically, the apoptosis-related protein, B-cell lymphoma-2 (Bcl-2), was downregulated in KIFC1 small interfering RNA-treated groups, whereas thee levels of Bcl-2-associated X protein and p53 were upregulated. In addition, the expression levels of phosphorylated phosphoinositide 3-kinase and phosphorylated AKT were decreased significantly when KIFC1 was silenced. The epithelial-mesenchymal transition-related proteins, N-cadherin, matrix metalloproteinase-2 (MMP-2), β-catenin, Slug, and Zinc finger E-box-binding homeobox 1, were downregulated, whereas the expression of E-cadherin was upregulated. The overexpression of KIFC1 was correlated closely with the progression of HCC and poor prognosis, and suggested that the expression levels of KIFC1 are a potential prognostic biomarker and therapeutic target in HCC.

The C-terminal kinesin motor KIFC1 may participate in nuclear reshaping and flagellum formation during spermiogenesis of Larimichthys crocea

Spermatogenesis is a highly ordered process in the differentiation of male germ cells. Nuclear morphogenesis is one of the most fundamental cellular transformations to take place during spermatogenesis. These striking transformations from spermatogonia to spermatozoa are a result of phase-specific adaption of the cytoskeleton and its association with molecular motor proteins. KIFC1 is a C-terminal kinesin motor protein that plays an essential role in acrosome formation and nuclear reshaping during spermiogenesis in mammals. To explore its functions during the same process in Larimichthys crocea, we cloned and characterized the cDNA of a mammalian KIFC1 homolog (termed lc-KIFC1) from the total RNA of the testis. The 2481 bp complete lc-KIFC1 cDNA contained a 53 bp 5' untranslated region, a 535 bp 3' untranslated region, and a 1893 bp open reading frame that encoded a special protein of 630 amino acids. The predicted lc-KIFC1 protein possesses a divergent tail region, stalk region, and conserved carboxyl motor region. Protein alignment demonstrated that lc-KIFC1 had 73.2, 49.8, 49.3, 54.6, 56.5, 53.1, and 52.1% identity with its homologs in Danio rerio, Eriocheir sinensis, Octopus tankahkeei, Gallus gallus, Xenopus laevis, Mus musculus, and Homo sapiens, respectively. Tissue expression analysis revealed that lc-kifc1 mRNA was mainly expressed in the testis. The trend of lc-kifc1 mRNA expression at different growth stages of the testis showed that the expression increased first and then decreased, in the stage IV of testis, its expression quantity achieved the highest level. In situ hybridization and immunofluorescence results showed that KIFC1 was localized around the nucleus in early spermatids. As spermatid development progressed, the signals increased substantially. These signals peaked and were concentrated at one end of the nucleus when the spermatids began to undergo dramatic changes. In the mature sperm, the signal for KIFC1 gradually became weak and was mainly localized in the tail. In summary, evaluation of the expression pattern for lc-KIFC1 at specific stages of spermiogenesis has shed light on the potential functions of this motor protein in major cytological transformations. In addition, this study may provide a model for researching the molecular mechanisms involved in spermatogenesis in other teleost species, which will lead to a better understanding of the teleost fertilization process.

Multi-institutional study of nuclear KIFC1 as a biomarker of poor prognosis in African American women with triple-negative breast cancer

Nuclear KIFC1 (nKIFC1) predicts worse outcomes in breast cancer, but its prognostic value within racially distinct triple-negative breast cancer (TNBC) patients is unknown. Thus, nKIFC1 expression was assessed by immunohistochemistry in 163 African American (AA) and 144 White TNBC tissue microarrays (TMAs) pooled from four hospitals. nKIFC1 correlated significantly with Ki67 in White TNBCs but not in AA TNBCs, suggesting that nKIFC1 is not merely a surrogate for proliferation in AA TNBCs. High nKIFC1 weighted index (WI) was associated with significantly worse overall survival (OS), progression-free survival (PFS), and distant metastasis-free survival (DMFS) (Hazard Ratios [HRs] = 3.5, 3.1, and 3.8, respectively; P = 0.01, 0.009, and 0.007, respectively) in multivariable Cox models in AA TNBCs but not White TNBCs. Furthermore, KIFC1 knockdown more severely impaired migration in AA TNBC cells than White TNBC cells. Collectively, these data suggest that nKIFC1 WI an independent biomarker of poor prognosis in AA TNBC patients, potentially due to the necessity of KIFC1 for migration in AA TNBC cells.

The overexpression of KIFC1 was associated with the proliferation and prognosis of non-small cell lung cancer

BACKGROUND

The kinesin family member C1 (KIFC1, also known as HSET) is a kinesin superfamily protein (KIFs). Although KIFC1 acts as a crucial role in the development of several human cancers, the KIFC1 expression profile and functional remain unclear in non-small cell lung cancer (NSCLC).

METHODS

We collected the fresh NSCLC samples and paired normal lung tissue in patients with lung cancer operation, and detected KIFC1 expression using quantitative reverse-transcription polymerase chain reaction (qRT-PCR) and Western blotting. To expand on previous smaller-scale studies, NSCLC tissue microarrays (TMA) were analyzed by IHC. Finally, cell lines were employed to further probe the potential mechanisms.

RESULTS

In this study, we described that KIFC1 was significantly upregulated in NSCLC tissues compared with the corresponding normal tissues. Moreover, KIFC1 overexpression was associated with the poor overall survival (OS) of NSCLC patients, and siRNA-mediated knockdown of KIFC1 significantly suppressed tumor cell proliferation in vitro. Further verification showed that inhibition of KIFC1 gene expression caused the upregulation of the cyclin-dependent kinases inhibitor p21 and downregulation of the cell cycle driver protein cdc2, which arrested cells in the G2-M phase.

CONCLUSIONS

we report that increased KIFC1 expression may promote cell proliferation and identified it as a biomarker of unfavorable prognosis in NSCLC patients.

Decreased Expression of KIFC1 in Human Testes with Globozoospermic Defects

Globozoospermia is a rare (prevalence of <0.1%) but severe male infertility condition. In our previous study, we found that robust KIFC1 immunostaining was detected in the human elongating/elongated spermatids during human acrosomogenesis. However, the relationship between the decreased expression of KIFC1 and human globozoospermia remains largely unknown. Testicular biopsies of 30 globozoospermia and 30 obstructive azoospermia patients who underwent infertility evaluation and treatment were utilized in this study. Reverse transcriptase polymerase chain reaction (RT-PCR), Western blots, immunohistochemistry, an in vivo model, and intratesticular injection of small inhibitory RNA (siRNA) against the Kifc1 gene were employed, and sperm abnormalities were evaluated by hematoxylin and eosin (H&E) staining and immunocytochemistry. We revealed that the testicular level of KIFC1 mRNA in globozoospermia was significantly reduced compared with that in obstructive azoospermia, and the KIFC1 protein was barely detectable in testicular specimens in 30% (9 of 30) of patients with globozoospermia. Furthermore, knockdown of the Kifc1 gene in mice increased the percentage of sperm with globozoospermic defects (26.5%). Decreased KIFC1 expression was mainly observed in the testes of patients with globozoospermia at the spermatid stage, which may be useful for counseling and management of such patients.

KIFC1: a promising chemotherapy target for cancer treatment?

The kinesin motor KIFC1 has been suggested as a potential chemotherapy target due to its critical role in clustering of the multiple centrosomes found in cancer cells. In this regard, KIFC1 seems to be non-essential in normal somatic cells which usually possess only two centrosomes. Moreover, KIFC1 is also found to initiatively drive tumor malignancy and metastasis by stabilizing a certain degree of genetic instability, delaying cell cycle and protecting cancer cell surviving signals. However, that KIFC1 also plays roles in other specific cell types complicates the question of whether it is a promising chemotherapy target for cancer treatment. For example, KIFC1 is found functionally significant in vesicular and organelle trafficking, spermiogenesis, oocyte development, embryo gestation and double-strand DNA transportation. In this review we summarize a recent collection of information so as to provide a generalized picture of ideas and mechanisms against and in favor of KIFC1 as a chemotherapy target. And we also drew the conclusion that KIFC1 is a promising chemotherapy target for some types of cancers, because the side-effects of inhibiting KIFC1 mentioned in this review are theoretically easy to avoid, while KIFC1 is functionally indispensable during mitosis and malignancy of multi-centrosome cancer cells. Further investigations of how KIFC1 is regulated throughout the mitosis in cancer cells are needed for the understanding of the pathways where KIFC1 is involved and for further exploitation of indirect KIFC1 inhibitors.

Formation and function of the manchette and flagellum during spermatogenesis

The last phase of spermatogenesis involves spermatid elongation (spermiogenesis), where the nucleus is remodeled by chromatin condensation, the excess cytoplasm is removed and the acrosome and sperm tail are formed. Protein transport during spermatid elongation is required for correct formation of the sperm tail and acrosome and shaping of the head. Two microtubular-based protein delivery platforms transport proteins to the developing head and tail: the manchette and the sperm tail axoneme. The manchette is a transient skirt-like structure surrounding the elongating spermatid head and is only present during spermatid elongation. In this review, we consider current understanding of the assembly, disassembly and function of the manchette and the roles of these processes in spermatid head shaping and sperm tail formation. Recent studies have shown that at least some of the structural proteins of the sperm tail are transported through the intra-manchette transport to the basal body at the base of the developing sperm tail and through the intra-flagellar transport to the construction site in the flagellum. This review focuses on the microtubule-based mechanisms involved and the consequences of their disruption in spermatid elongation.

Shaping of interphase chromosomes by the microtubule network

It is well established that microtubule dynamics play a major role in chromosome condensation and localization during mitosis. During interphase, however, it is assumed that the metazoan nuclear envelope presents a physical barrier, which inhibits interaction between the microtubules located in the cytoplasm and the chromatin fibers located in the nucleus. In recent years, it has become apparent that microtubule dynamics alter chromatin structure and function during interphase as well. Microtubule motor proteins transport several transcription factors and exogenous DNA (such as plasmid DNA) from the cytoplasm to the nucleus. Various soluble microtubule components are able to translocate into the nucleus, where they bind various chromatin elements leading to transcriptional alterations. In addition, microtubules may apply force on the nuclear envelope, which is transmitted into the nucleus, leading to changes in chromatin structure. Thus, microtubule dynamics during interphase may affect chromatin spatial organization, as well as transcription, replication and repair.

Gene expression pattern of KIFC3 during spermatogenesis of the skink Eumeces chinensis

Kinesin superfamily is a class of microtubule-dependent motors that play crucial roles in acrosome biogenesis, nuclear reshaping and flagellum formation during spermiogenesis. We have cloned kinesin-like gene kifc3 (termed ec-kifc3) from the total RNA of the testis of the skink Eumeces chinensis. The cDNA sequence of ec-kifc3 had a full-length of 3033bp, including a 260bp 5'-untranslated region (5'UTR), a 445bp 3'-untranslated region (3'UTR) and an open reading frame that encoded a 775-amino-acid protein. Additionally, the calculated molecular weight of the putative ec-KIFC3 was 87kDa and its estimated isoelectric point was 6.18. Structurally, the putative ec-KIFC3 had three domains: head domain, neck domain and tail domain. Protein alignment demonstrated that ec-KIFC3 had 47.2%, 67.8%, 68.8%, 69.3% and 76.8% identity with its homologues in Xenopus laevis, Mus musculus, Cricetulus griseus, Homo sapiens, and Gallus gallus. The phylogenetic analysis showed that ec-KIFC3 was more related to KIFC3 in vertebrates than invertebrates. Tissue expression results showed the presence of ec-KIFC3 in various tissues with its highest expression in the testis. In situ hybridization demonstrated that ec-KIFC3 mRNA was distributed around the nucleus in early and middle stage spermatids and expressed in the nucleus in the elongating spermatids during spermiogenesis. Besides, the ec-KIFC3 mRNA was expressed in the acrosome of the developmental spermatids. From the results of in situ hybridization and previous researches, we speculated that ec-KIFC3 may play a role in nuclear morphogenesis and acrosome formation during spermiogenesis of E. chinensis.

Ubiquitination regulates the morphogenesis and function of sperm organelles

It is now understood that protein ubiquitination has diverse cellular functions in eukaryotes. The molecular mechanism and physiological significance of ubiquitin-mediated processes have been extensively studied in yeast, Drosophila and mammalian somatic cells. Moreover, an increasing number of studies have emphasized the importance of ubiquitination in spermatogenesis and fertilization. The dysfunction of various ubiquitin systems results in impaired sperm development with abnormal organelle morphology and function, which in turn is highly associated with male infertility. This review will focus on the emerging roles of ubiquitination in biogenesis, function and stability of sperm organelles in mammals.

Acroframosome-dependent KIFC1 facilitates acrosome formation during spermatogenesis in the caridean shrimp Exopalaemon modestus

Background

Acrosome formation and nuclear shaping are the main events in spermatogenesis. During spermiogenesis in Exopalaemon modestus, a unique microtubular structure called the acroframosome (AFS) forms in spermatids. The AFS links to a temporary organelle called the lamellar complex (LCx) leading to the formation of an everted umbrella-shaped acrosome and a dish-shaped nucleus in the mature sperm. These morphological changes require complex cell motility in which the C-terminal kinesin motor protein called KIFC1 is involved. In this study, we demonstrate that KIFC1 moves along the AFS and plays an important role in acrosome formation and nuclear shaping during spermatogenesis in E. modestus.

Methodology/Principal Findings

We cloned a 3125 bp complete cDNA of kifc1 from the testis of E. modestus by PCR. The predicted secondary and tertiary structures of E. modestus KIFC1 contain three domains: a) the C-terminus, b) the stalk region, and the c) N-terminusl. Semi-quantitative RT-PCR detected the expression of kifc1 mRNA in different tissues of E. modestus. In situ hybridization demonstrated the temporal and spatial expression profile of kifc1 during spermiogenesis. Western blot identified the expression of KIFC1 in different tissues of E. modestus, including the testis. Immunofluorescence localized KIFC1, tubulin, GM130, and mitochondria in order to elucidate their role during spermiogenesis in E. modestus.

Conclusion/Significance

Our results indicate that KIFC1 transports the Golgi complex, mitochondria, and other cellular components that results in acrosome formation and nuclear shaping in E. modestus. The KIFC1 transport function depends upon the microtubular structure called the acroframosome (AFS). This study describes some of the molecular mechanisms involved in the acrosome formation and nuclear shaping in E. modestus. In addition, this study may provide a model for studying the molecular mechanisms involved in spermatogenesis in other crustacean species and lead to a better understanding of the fertilization process in crustaceans.

Molecular characterization and expression analysis of a KIFC1-like kinesin gene in the testis of Eumeces chinensis

The member of the kinesin-14 subfamily, KIFC1, is a carboxyl-terminal motor protein that plays an important role in the elongation of nucleus and acrosome biogenesis during the spermiogenesis of mammals. Here, we had cloned and sequenced the cDNA of a mammalian KIFC1 homologue (termed ec-KIFC1) from the total RNA of the testis of the reptile Eumeces chinensis. The full-length sequence was 2,339 bp that contained a 216 bp 5'-untranslated region (5'UTR), a 194 bp 3'-untranslated region (3'UTR) and a 1,929 bp open reading frame that encoded a special protein of 643 amino acids (aa). The calculated molecular weight of the putative ec-KIFC1 was 71 kDa and its estimated isoelectric point was 9.47. The putative ec-KIFC1 protein owns a tail domain from 1 to 116 aa, a stalk domain from 117 to 291 aa and a conserved carboxyl motor domain from 292 to 642 aa. Protein alignment demonstrated that ec-KIFC1 had 45.6, 42.8, 44.6, 36.9, 43.7, 46.4, 45.1, 55.6 and 49.8 % identity with its homologues in Mus musculus, Salmo salar, Danio rerio, Eriocheir sinensis, Rattus norvegicus, Homo sapiens, Bos taurus, Gallus gallus and Xenopus laevis, respectively. Tissue expression analysis showed the presence of ovary, heart, liver, intestine, oviduct, testis and muscle. The phylogenetic tree revealed that ec-KIFC1 was more closely related to vertebrate KIFC1 than to invertebrate KIFC1. In situ hybridization showed that the ec-KIFC1 mRNA was localized in the periphery of the nuclear membrane and the center of the nucleus in early spermatids. In mid spermatids, the ec-KIFC1 had abundant expression in the center of nucleus, and was expressed in the tail and the anterior part of spermatids. In the late spermatid, the nucleus gradually became elongated, and the ec-KIFC1 mRNA signal was still centralized in the nucleus. In mature spermatids, the signal of the ec-KIFC1 gradually became weak, and was mainly located at the tail of spermatids. Therefore, the ec-KIFC1 probably plays a critical role in the spermatogenesis of E. chinensis.

The expression pattern of the C-terminal kinesin gene kifc1 during the spermatogenesis of Sepiella maindroni

In this study, we investigated the gene sequence and characteristic of kifc1 in Sepiella maindroni through PCR and RACE technology. Our research aimed particularly at the spatio-temporal expression pattern of kifc1 in the developmental testis through in situ hybridization. The particular role of kifc1 in the spermatogenesis of S. maindroni was our particular interest. Based on multiple protein sequence alignments of KIFC1 homologues, kifc1 gene from the testis of S. maindroni was identified, which consisted of 2432bp including a 2109 in-frame ORF corresponding to 703 continuous amino acids. The encoded polypeptide shared highest similarity with Octopus tankahkeei. Through the prediction of the secondary and tertiary structures, the motor domain of KIFC1 was conserved at the C-terminal, having putative ATP-binding and microtubule-binding motifs, while the N-terminal was more specific to bind various cargoes for cellular events. The stalk domain connecting between the C-terminal and N-terminal determined the direction of movement. According to RT-PCR results, the kifc1 gene is not tissue-specific, commonly detected in different tissues, for example, the testis, liver, stomach, muscle, caecum and gills. Through an in situ hybridization method, the expression pattern of KIFC1 protein mimics in the spermatogenesis of S. maindroni. During the primary stage of the spermatogenesis, the kifc1 mRNA signal was barely detectable. At the early spermatids, the signal started to be present. With the elongation of spermatids, the signals increased substantially. It peaked and gathered around the acrosome area when the spermatids began to transform to spindle shape. As the spermatids developed into mature sperm, the signal vanished. In summary, the expression of kfic1 at specific stages during spermiogenesis and its distribution shed light on the potential functions of this motor in major cytological transformations. The KIFC1 homologue may provide a direct shaping force to the nucleus or influence the shaping process through indirect regulation.

LINCing the nuclear envelope to gametogenesis

Gametogenesis combines two important features: reduction of the genome content from diploid to haploid by carefully partitioning chromosomes, and the subsequent differentiation into fertilization-competent gametes, which in males is characterized by profound nuclear restructuring. These are quite difficult tasks and require a tight coordination of different cellular mechanisms. Recent studies in the field established a key role for LINC complexes in both meiosis and sperm head formation. LINC complexes comprise SUN and KASH domain proteins that form nuclear envelope (NE) bridges, linking the nucleoskeleton to the cytoskeleton. They are well known for their crucial roles in diverse cellular and developmental processes, such as nuclear positioning and cell polarization. In this review, we highlight key roles ascribed to LINC complexes and to the nucleocytoskeletal connection in gametogenesis. First, we give a short overview about the general features of LINC components and the profound reorganization of the NE in germ cells. We then focus on specific roles of LINC complexes in meiotic chromosome dynamics and their impact on pairing, synapsis, and recombination. Finally, we provide an update of the mechanisms controlling sperm head formation and discuss the role of sperm-specific LINC complexes in nuclear shaping and their relation to specialized cytoskeletal structures that form concurrently with nuclear restructuring and sperm elongation.

MARCH7 E3 ubiquitin ligase is highly expressed in developing spermatids of rats and its possible involvement in head and tail formation

Spermatogenesis is a highly complicated metamorphosis process of male germ cells. Recent studies have provided evidence that the ubiquitin-proteasome system plays an important role in sperm head shaping, but the underlying mechanism is less understood. In this study, we localized membrane-associated RING-CH (MARCH)7, an E3 ubiquitin ligase, in rat testis. Northern blot analysis showed that March7 mRNA is expressed ubiquitously but highly in the testis and ovary. In situ hybridization of rat testis demonstrated that March7 mRNA is expressed weakly in spermatogonia and its level is gradually increased as they develop. Immunohistochemical analysis detected MARCH7 protein expression in spermiogenic cells from late round spermatids to elongated spermatids and in epididymal spermatozoa. Moreover, MARCH7 was found to be localized to the caudal end of the developing acrosome of late round and elongating spermatids, colocalizing with β-actin, a component of the acroplaxome. In addition, MARCH7 was also detected in the developing flagella and its expression levels were prominent in elongated spermatids. We also showed that MARCH7 catalyzes lysine 48 (K48)-linked ubiquitination. Immunolocalization studies revealed that K48-linked ubiquitin chains were detected in the heads of elongating spermatids and in the acrosome/acroplaxome, neck, midpiece and cytoplasmic lobes of elongated spermatids. These results suggest that MARCH7 is involved in spermiogenesis by regulating the structural and functional integrity of the head and tail of developing spermatids.

Changing subcellular localization of nuclear transport factors during human spermatogenesis

Spermatogenesis requires progressive changes in gene expression mediated by hormonal and local factors. Regulated macromolecular movement between nuclear and cytoplasmic compartments enables these essential responses to changing extracellular cues, and dynamic production of the nucleocytoplasmic transporters and importin proteins, throughout gametogenesis in rodents implicates them as key mediators of germline differentiation. We examined normal adult human testis expression profiles of six importins plus five additional proteins involved in nucleocytoplasmic transport. Although most were detected in the nucleus during germline differentiation, importin α4 was exclusively observed in Sertoli and germ cell cytoplasm. Many proteins were present in round spermatid nuclei (importins α1, α3, β1, β3; exportin-1, Nup62, Ran, RanBP1, RCC1), and remarkable intense nuclear and/or nuclear-associated signals were detected for importin α1, importin α3 and Nup62 in spermatocytes. This study identifies conserved aspects of nucleocytoplasmic transport during spermatogenesis and extends our knowledge of the dynamic presence of these proteins, which indicates that they contribute to germ cell-specific cargo trafficking and potentially to other functions during human spermatogenesis. We also demonstrate for the first time that importin α3 is nuclear in spermatocytes, when exportin-1 is cytoplasmic, suggesting that nuclear transport is altered during meiosis.

Characterization and expression pattern of KIFC1-like kinesin gene in the testis of the Macrobrachium nipponense with discussion of its relationship with structure lamellar complex (LCx) and acroframosome (AFS)

Spermiogenesis is a developmental process undergoing continuous differentiation to drive a diploid spermatogonium towards a haploid sperm cell. This striking transformation from spermatogonium to spermatozoa is made possible by the stage-specific adaption of cytoskeleton and associated molecular motor proteins. KIFC1 is a C-terminal kinesin motor found to boast essential roles in acrosome biogenesis and nuclear reshaping during spermiogenesis in rat. To explore its functions during the same process in Macrobrachium nipponense, we have cloned and sequenced the cDNA of a mammalian KIFC1 homologue (termed mn-KIFC1) from the total RNA of the testis. The 2,296 bp mn-KIFC1 cDNA contained a 87 bp 5' untranslated region, a 211 bp 3' untranslated region and a 1,998 bp open reading frame. Protein alignment demonstrated that mn-KIFC1 had 37.7, 58.7, 38.4, 37.2, 38.9 and 37.8% identity with its homologues in Salmo salar, Eriocheir sinensis, Homo sapiens, Mus musculus, Danio rerio and Xenopus laevis respectively. The phylogenetic tree revealed that mn-KIFC1 is most related to E. Sinensis KIFC1 among the examined species. Tissue expression analysis showed the presence of mn-KIFC1 in the testis, hepatopancreas, gill, muscle and heart. In situ hybridization showed that the mn-KIFC1 mRNA was localized at the periphery of the nuclear membrane and in the proacrosomal vesicle in early and middle spermatids. In late spermatids and spermatozoa, mn-KIFC1 was expressed in the acrosome and in the spike. In situ hybridization also indicated that KIFC1 works together with lamellar complex (LCx) and acroframosome (AFS) to drive acrosome formation and cellular transformation. LCx and AFS have both been previously proved to have essential roles during spermiogenesis in M. nipponense. In conclusion, the expression of mn-kifc1 at specific stages of spermiogenesis suggests a role in cellular transformations in M. nipponense.

Regulated nucleocytoplasmic transport during gametogenesis

Gametogenesis is the process by which sperm or ova are produced in the gonads. It is governed by a tightly controlled series of gene expression events, with some common and others distinct for males and females. Nucleocytoplasmic transport is of central importance to the fidelity of gene regulation that is required to achieve the precisely regulated germ cell differentiation essential for fertility. In this review we discuss the physiological importance for gamete formation of the molecules involved in classical nucleocytoplasmic protein transport, including importins/karyopherins, Ran and nucleoporins. To address what functions/factors are conserved or specialized for these developmental processes between species, we compare knowledge from mice, flies and worms. The present analysis provides evidence of the necessity for and specificity of each nuclear transport factor and for nucleoporins during germ cell differentiation. This article is part of a Special Issue entitled: Nuclear Transport and RNA Processing.

Molecular characterization of a KIF3B-like kinesin gene in the testis of Octopus tankahkeei (Cephalopoda, Octopus)

KIF3B is known for maintaining and assembling cilia and flagellum. To date, the function of KIF3B and its relationship with KIF3A during spermiogenesis in the cephalopod Octopus tankahkeei remains unknown. In the present study, we characterized a gene encoding a homologue of rat KIF3B in the O. tankahkeei testis and examined its temporal and spatial expression pattern during spermiogenesis. The cDNA of KIF3B was obtained with degenerate and RACE PCR and the distribution pattern of ot-kif3b were observed with RT-PCR. The morphological development during spermiogenesis was illustrated by histological and transmission electron microscopy and mRNA expression of ot-kif3b was observed by in situ hybridization. The 2,365 nucleotides cDNA consisted of a 102 bp 5' untranslated region (UTR), a 2,208 bp open reading frame (ORF) encoding a protein of 736 amino acids, and a 55 bp 3' UTR. Multiple alignments revealed that the putative Ot-KIF3B shared 68, 68, 69, 68, and 67% identity with that of Homo sapiens, Mus musculus, Gallus gallus, Danio rerio, and Xenopus laevis, respectively, along with high identities with Ot-KIF3A in fundamental structures. Ot-kif3b transcripts appeared gradually in early spermatids, increased in intermediate spermatids and maximized in drastically remodeled and final spermatids. The kif3b gene is identified and its expression pattern is demonstrated for the first time in O. tankahkeei. Compared to ot-kif3a reported by our laboratory before, our data suggested that the putative heterodimeric motor proteins Ot-KIF3A/B may be involved in intraspermatic transport and might contribute to structural changes during spermiogenesis.

KIFC1-like motor protein associates with the cephalopod manchette and participates in sperm nuclear morphogenesis in Octopus tankahkeei

Background

Nuclear morphogenesis is one of the most fundamental cellular transformations taking place during spermatogenesis. In rodents, a microtubule-based perinuclear structure, the manchette, and a C-terminal kinesin motor KIFC1 are believed to play crucial roles in this process. Spermatogenesis in Octopus tankahkeei is a good model system to explore whether evolution has created a cephalopod prototype of mammalian manchette-based and KIFC1-dependent sperm nuclear shaping machinery.

Methodology/Principal Findings

We detected the presence of a KIFC1-like protein in the testis, muscle, and liver of O. tankahkeei by Western Blot. Then we tracked its dynamic localization in spermatic cells at various stages using Immunofluorescence and Immunogold Electron Microscopy. The KIFC1-like protein was not expressed at early stages of spermatogenesis when no significant morphological changes occur, began to be present in early spermatid, localized around and in the nucleus of intermediate and late spermatids where the nucleus was dramatically elongated and compressed, and concentrated at one end of final spermatid. Furthermore, distribution of the motor protein during nuclear elongation and condensation overlapped with that of the cephalopod counterpart of manchette at a significant level.

Conclusions/Significance

The results support the assumption that the protein is actively involved in sperm nuclear morphogenesis in O. tankahkeei possibly through bridging the manchette-like perinuclear microtubules to the nucleus and assisting in the nucleocytoplasmic trafficking of specific cargoes. This study represents the first description of the role of a motor protein in sperm nuclear shaping in cephalopod.

Self/nonself perception, reproduction and the extended MHC

Self/nonself perception governs mate selection in most eukaryotic species. It relies on a number of natural barriers that act before, during and after copulation. These hurdles prevent a costly investment into an embryo with potentially suboptimal genetic and immunological properties and aim at discouraging fertilization when male and female gametes exhibit extensive sharing of alleles. Due to the fact that several genes belonging to the extended major histocompatibility complex (xMHC) carry out crucial immune functions and are the most polymorphic within vertebrate genomes, it is likely that securing heterozygosity and the selection of rare alleles within this gene complex contributes to endowing the offspring with an advantage in fighting infections. Apart from MHC class I and II antigens, the products of several other genes within the xMHC are candidates for participating in mate choice, especially since the respective loci are subject to long-range linkage disequilibrium which may aid to preserve functionally connected alleles within a given haplotype. Among these loci are polymorphic odorant receptor genes that are expressed not only in the olfactory epithelium, but also within male reproductive tissues. They may thus not only be of importance in olfaction-influenced mate choice, by recognizing MHC-dependent individual-specific olfactory signals, but could also guide spermatozoa along chemical gradients to their target, the oocyte. By focusing on the human HLA complex and genes within its vicinity, we show here that the products of several xMHC-specified molecules might be involved in self/nonself perception during reproduction. Although the molecular details are often unknown, the existence of highly diverse, yet intertwined pre- and post-copulatory barriers suggests that xMHC-encoded proteins may be important for various stages of mate choice, germ cell development, as well as embryonic and foetal life in mammals and other vertebrates. Many of these genes should thus be regarded as crucial not only within the immune system, but also in reproduction.

Surfing the wave, cycle, life history, and genes/proteins expressed by testicular germ cells. Part 2: changes in spermatid organelles associated with development of spermatozoa

Spermiogenesis is a long process whereby haploid spermatids derived from the meiotic divisions of spermatocytes undergo metamorphosis into spermatozoa. It is subdivided into distinct steps with 19 being identified in rats, 16 in mouse and 8 in humans. Spermiogenesis extends over 22.7 days in rats and 21.6 days in humans. In this part, we review several key events that take place during the development of spermatids from a structural and functional point of view. During early spermiogenesis, the Golgi apparatus forms the acrosome, a lysosome-like membrane bound organelle involved in fertilization. The endoplasmic reticulum undergoes several topographical and structural modifications including the formation of the radial body and annulate lamellae. The chromatoid body is fully developed and undergoes structural and functional modifications at this time. It is suspected to be involved in RNA storing and processing. The shape of the spermatid head undergoes extensive structural changes that are species-specific, and the nuclear chromatin becomes compacted to accommodate the stream-lined appearance of the sperm head. Microtubules become organized to form a curtain or manchette that associates with spermatids at specific steps of their development. It is involved in maintenance of the sperm head shape and trafficking of proteins in the spermatid cytoplasm. During spermiogenesis, many genes/proteins have been implicated in the diverse dynamic events occurring at this time of development of germ cells and the absence of some of these have been shown to result in subfertility or infertility.

Molecular cloning and characterization of KIFC1-like kinesin gene (ot-kifc1) from Octopus tankahkeei

Spermiogenesis in Octopus tankahkeei involves striking cellular reorganization to generate a mature spermatozoon. This process may require spermatid-specific adaptation of cytoskeleton and associated molecular motor proteins. KIFC1 is a C-terminal kinesin motor with important roles in acrosome biogenesis and nuclear reshaping during spermiogenesis in rat. Here, we have cloned and characterized the gene encoding a homologue of rat KIFC1, termed as ot-kifc1, from the testis of O. tankahkeei. The 2229 bp complete cDNA contains a 75 bp 5'-untranslated region, a 1992 bp open reading frame and a 162 bp 3'-untranslated region. The deduced protein shares an overall identity of 40%, 41%, 39% and 41% with its counterpart from human, rat, mouse and African clawed frog, respectively. Tissue expression analysis revealed ot-kifc1 was expressed in testis, gill and hepatopancreas, but not in other tissues examined. In situ hybridization result showed the ot-kifc1 message was hardly detectable in early spermatid, concentrated at the tail region of intermediate spermatid, abundant in spermatid undergoing dramatic elongation and compression, enriched at one end in late spermatids and disappeared in mature sperm. In conclusion, the expression of ot-kifc1 at specific stages of spermiogenesis suggests a role for this motor in major cytological transformations.

Redistribution of nuclear pores during formation of the redundant nuclear envelope in mouse spermatids

Extensive morphological modification occurs during mammalian spermiogenesis when spermatids change their spherical shape into cells with a compact head and a long tail. In this study, freeze-fracture was used to elucidate the alteration of the nuclear envelope during this process. Nuclear condensation resulted in a great reduction of spermatid nuclear volume and the formation of the redundant nuclear envelope. During nuclear condensation, distribution patterns of nuclear pores were greatly affected by the developing acrosome and manchette. As the acrosome enlarged to cap the nucleus, the pores redistributed caudally in the nuclear membranes and became exclusively localized to the redundant nuclear envelope. Manchette microtubules play an important role in shaping the nucleus, and formation of the manchette was associated with exclusion of nuclear pores from the underlying nuclear envelope; therefore, it is likely that the redistribution of nuclear pores was aided by manchette development. The appearance of an electron-lucent nuclear region surrounded by the nascent redundant nuclear envelope indicated a pathway for transporting degradation products through the nuclear pores to the residual cytoplasm. The packaging of the nuclear pores into the redundant nuclear envelope suggests that they play a role in late stages of sperm maturation or in fertilization, as most other unnecessary organelles of sperm are discarded during spermiogenesis or during shedding of the cytoplasmic droplet.

The presence of kinesin superfamily motor proteins KIFC1 and KIF17 in normal and pathological human placenta

Kinesin superfamily proteins (KIFs) are motor proteins that participate in chromosomal and spindle movements during mitosis and meiosis, and transport membranous organelles and macromolecules fundamental for cellular functions. Although the roles of KIFs in axonal and dendritic transports have been studied extensively, their role in intracellular transport in general is less well known. The diversity of kinesins suggests that each kinesin may have a specific function. Therefore, in this study we aimed to investigate the presence and cellular localization of KIFC1 and KIF17 in normal and pathological human placentas. First-trimester (22-56 days) and normal, preeclamptic (PE), and diabetic-term placental tissues were obtained and further studied by immunohistochemistry (IHC) and Western blot methods. KIFC1 was mainly localized to the syncytiotrophoblast both in early and term placental samples. However, a stronger immunoreactivity was observed both in PE and diabetic placentas compared to normal-term placentas. KIF17 was most intensively localized in developing vascular endothelium in early pregnancy. Even though KIF17 was moderately stained in the endothelium of villi from normal human-term placentas, stronger immunoreactivity was observed in all types of villi of both PE and diabetic placentas. Western blotting of tissue extracts confirmed the IHC results. Here, we demonstrate the presence of KIFC1 and KIF17 in human placenta for the first time. The intense expression of KIFC1 in syncytiotrophoblast and KIF17 in vascular endothelium suggests that both the proteins might be important in a cargo-transport system. An increased expression pattern of both KIFC1 and KIF17 in PE and diabetes might suggest that these proteins may be involved in complex trophoblast functions and placental pathologies. Further studies will clarify the physiological role of KIFs in human placental transport and development.

KIFC1 participates in acrosomal biogenesis, with discussion of its importance for the perforatorium in the Chinese mitten crab Eriocheir sinensis

Spermatogenesis is a complicated process during which spermatogonia undergo proliferation and divisions leading, after a series of dramatic changes, to the production of mature spermatozoa. Many molecular motors are involved in this process. KIFC1, a C-terminal kinesin motor, participates in acrosome biogenesis and nuclear shaping. We report here the expression profile of KIFC1 during spermatogenesis in the Chinese mitten crab, Eriocheir sinensis. KIFC1 mainly localizes around the nucleus but is also present within the nucleus of the spermatogonium and spermatocyte. At the early spermatid stage, KIFC1 begins to be distributed on the nuclear membrane at the region where the proacrosomal vesicle is located. By the late spermatid stage, KIFC1 is found on the acrosome. Immunocytochemical and ultrastructural analyses have shown that KIFC1 localizes on the perforatorium, which is composed of an apical cap and an acrosomal tubule. We demonstrate that, during spermatogenesis in E. sinensis, KIFC1 probably plays important roles in the biogenesis of the acrosome and in its maintenance. KIFC1 may also be essential for the eversion of the acrosome during fertilization.

RIM-BP3 is a manchette-associated protein essential for spermiogenesis

During spermiogenesis, round spermatids are converted into motile sperm in mammals. The mechanisms responsible for sperm morphogenesis are poorly understood. We have characterized a novel protein, RIM-BP3, with a specialized function in spermatid development in mice. The RIM-BP3 protein is associated with the manchette, a transient microtubular structure believed to be important for morphogenesis during spermiogenesis. Targeted deletion of the RIM-BP3 gene resulted in male infertility owing to abnormal sperm heads, which are characterized by a deformed nucleus and a detached acrosome. Consistent with its role in morphogenesis, the RIM-BP3 protein physically associates with Hook1, a known manchette-bound protein required for sperm head morphogenesis. Interestingly, RIM-BP3 does not interact with the truncated Hook1 protein characterized in azh (abnormal spermatozoon head) mutant mice. Moreover, RIM-BP3 and Hook1 mutant mice display several common abnormalities, in particular with regard to the ectopic positioning of the manchette within the spermatid, a presumed cause of sperm head deformities. These observations suggest an essential role for RIM-BP3 in manchette development and function through its interaction with Hook1. As the occurrence of deformed spermatids is one of the common abnormalities leading to malfunctional sperm, identification of RIM-BP3 might provide insight into the molecular cue underlying causes of male infertility in humans.

Identification of a novel Leucine-rich repeat protein and candidate PP1 regulatory subunit expressed in developing spermatids

Background

Spermatogenesis is comprised of a series of highly regulated developmental changes that transform the precursor germ cell into a highly specialized spermatozoon. The last phase of spermatogenesis, termed spermiogenesis, involves dramatic morphological change including formation of the acrosome, elongation and condensation of the nucleus, formation of the flagella, and disposal of unnecessary cytoplasm. A prominent cytoskeletal component of the developing spermatid is the manchette, a unique microtubular structure that surrounds the nucleus of the developing spermatid and is thought to assist in both the reshaping of the nucleus and redistribution of spermatid cytoplasm. Although the molecular motor KIFC1 has been shown to associate with the manchette, its precise role in function of the manchette and the identity of its testis specific protein partners are unknown. The purpose of this study was to identify proteins in the testis that interact with KIFC1 using a yeast 2 hybrid screen of a testis cDNA library.

Results

Thirty percent of the interacting clones identified in our screen contain an identical cDNA encoding a 40 kD protein. This interacting protein has 4 leucine-rich repeats in its amino terminal half and is expressed primarily in the testis; therefore we have named this protein testis leucine-rich repeat protein or TLRR. TLRR was also found to associate tightly with the KIFC1 targeting domain using affinity chromatography. In addition to the leucine-rich repeats, TLRR contains a consensus-binding site for protein phosphatase-1 (PP1). Immunocytochemistry using a TLRR specific antibody demonstrates that this protein is found near the manchette of developing spermatids.

Conclusion

We have identified a previously uncharacterized leucine-rich repeat protein that is expressed abundantly in the testis and associates with the manchette of developing spermatids, possibly through its interaction with the KIFC1 molecular motor. TLRR is homologous to a class of regulatory subunits for PP1, a central phosphatase in the reversible phosphorylation of proteins that is key to modulation of many intracellular processes. TLRR may serve to target this important signaling molecule near the nucleus of developing spermatids in order to control the cellular rearrangements of spermiogenesis.