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)

Transcriptome analysis of reproductive tract tissues of male river prawn Macrobrachium americanum

BACKGROUND

The river prawn, Macrobrachium americanum (M. americanum), is one of the largest prawns of the genus in Latin America and is an amphidromous species distributed along the Pacific coast of America. This prawn has commercial value due to its size and taste, making it a good option for aquaculture production. Its culture has been attempted in ponds and concrete tanks, but no successful technique can still support commercial production. Understanding the mechanisms that regulate reproduction at the molecular level is very important. This knowledge can provide tools for manipulating transcripts, which could increase the number or size of animals in the culture. Our understanding of the mechanism that regulates the reproduction of M. americanum at the molecular level is limited.

AIM

Perform and analyze the transcriptome assembly of the testes, vas deferens, and terminal ampulla of M. americanum. to provide new molecular information about its reproduction.

METHODS AND RESULTS

The cDNA library was constructed and sequenced for each tissue to identify novel transcripts. A combined transcriptome with the three tissues was assembled using Trinity software. Unigenes were annotated using BLASTx and BLAST2GO. The transcriptome assembly generated 1,059,447 unigenes, of which 7222 genes had significant hits (e-value < 1 × 10-5) when compared against the Swiss-Prot database. Around 75 genes were related to sex determination, testis development, spermatogenesis, spermiogenesis, fertilization, maturation of testicular cells, neuropeptides, hormones, hormone receptors, and/or embryogenesis.

CONCLUSIONS

These results provide new molecular information about M. americanum reproduction, representing a reference point for further genetic studies of this species.

Dynamic cellular and molecular characteristics of spermatogenesis in the viviparous marine teleost Sebastes schlegelii†

Spermatogenesis is a dynamic cell developmental process that is essential for reproductive success. Vertebrates utilize a variety of reproductive strategies, including sperm diversity, and internal and external fertilization. Research on the cellular and molecular dynamic changes involved in viviparous teleost spermatogenesis, however, is currently lacking. Here, we combined cytohistology, 10 × genomic single-cell RNA-seq, and transcriptome technology to determine the dynamic development characteristics of the spermatogenesis of Sebastes schlegelii. The expressions of lhcgr (Luteinizing hormone/Choriogonadotropin receptor), fshr (follicle-stimulating hormone receptor), ar (androgen receptor), pgr (progesterone receptor), and cox (cyclo-oxygen-ase), as well as the prostaglandin E and F levels peaked during the maturation period, indicating that they were important for sperm maturation and mating. Fifteen clusters were identified based on the 10 × genomic single-cell results. The cell markers of the sub-cluster were identified by their upregulation; piwil, dazl, and dmrt1 were upregulated and identified as spermatogonium markers, and sycp1/3 and spo11 were identified as spermatocyte markers. For S. schlegelii, the sperm head nucleus was elongated (spherical to streamlined in shape), which is a typical characteristic for sperm involved in internal fertilization. We also identified a series of crucial genes associated with spermiogenesis, such as spata6, spag16, kif20a, trip10, and klf10, while kif2c, kifap3, fez2, and spaca6 were found to be involved in nucleus elongation. The results of this study will enrich our cellular and molecular knowledge of spermatogenesis and spermiogenesis in fish that undergo internal fertilization.

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.

Homologues of Piwi control transposable elements and development of male germline in Penaeus monodon

PIWI belongs to the Argonaute protein family, which is a major protein component in RNA silencing pathway. Piwi proteins play roles in the control of transposons and germline development. They have been widely studied in vertebrates and flies, while very little is known in crustacean so far. We have previously identified and characterized a cDNA encoding Piwi protein (PmPiwi1) in the black tiger shrimp Penaeus monodon. In this study, a cDNA encoding another Piwi protein namely PmPiwi2 was identified by rapid amplification of cDNA ends (RACEs). PmPiwi2 was expressed solely in shrimp testis and ovary, indicating its potential role in germ cell development. Similar to PmPiwi1, PmPiwi2 also plays a part in the control of transposons as PmPiwi2-knockdown shrimp showed a significant increase in the expression of gypsy2 retrotransposon and mariner element in the testis. In addition, a reduction of sperm numbers in the spermatophore of PmPiwi2-knockdown shrimp suggests that PmPiwi2 is required for spermatogenesis similar to PmPiwi1. This study further demonstrated that apoptotic cell death was strongly detected in spermatogonia and spermatocyte cells of both PmPiwi-knockdown shrimp and thus, could be the cause of reduced sperm count. Investigation of sperm morphology showed a remarkably high proportion of abnormal sperms in the spermatophore of the PmPiwi1-knockdown shrimp, while PmPiwi2-knockdown shrimp had comparable percentage of abnormal sperms to the control shrimp. Consistently, the expression of KIFC1, a gene that is necessary for spermiogenesis was significantly reduced upon PmPiwi1 silencing, but not in the PmPiwi2-knockdown shrimp. Our results suggested that while both PmPiwis are required for the development of spermatid, only PmPiwi1 is possibly involved in the final stage of sperm maturation.

De novo gonad transcriptome analysis of the common littoral shrimp Palaemon serratus: novel insights into sex-related genes

BACKGROUND

The common littoral shrimp Palaemon serratus is an economically important decapod resource in some European communities. Aquaculture practices prevent the genetic deterioration of wild stocks caused by overfishing and at the same time enhance the production. The biotechnological manipulation of sex-related genes has the proved potential to improve the aquaculture production but the scarcity of genomic data about P. serratus hinders these applications. RNA-Seq analysis has been performed on ovary and testis samples to generate a reference gonadal transcriptome. Differential expression analyses were conducted between three ovary and three testis samples sequenced by Illumina HiSeq 4000 PE100 to reveal sex-related genes with sex-biased or sex-specific expression patterns.

RESULTS

A total of 224.5 and 281.1 million paired-end reads were produced from ovary and testis samples, respectively. De novo assembly of ovary and testis trimmed reads yielded a transcriptome with 39,186 transcripts. The 29.57% of the transcriptome retrieved at least one annotation and 11,087 differentially expressed genes (DEGs) were detected between ovary and testis replicates. Six thousand two hundred seven genes were up-regulated in ovaries meanwhile 4880 genes were up-regulated in testes. Candidate genes to be involved in sexual development and gonadal development processes were retrieved from the transcriptome. These sex-related genes were discussed taking into account whether they were up-regulated in ovary, up-regulated in testis or not differentially expressed between gonads and in the framework of previous findings in other crustacean species.

CONCLUSIONS

This is the first transcriptome analysis of P. serratus gonads using RNA-Seq technology. Interesting findings about sex-related genes from an evolutionary perspective (such as Dmrt1) and for putative future aquaculture applications (Iag or vitellogenesis genes) are reported here. We provide a valuable dataset that will facilitate further research into the reproductive biology of this shrimp.

Manchette-acrosome disorders and testicular efficiency decline observed in hypercholesterolemic rabbits are recovered with olive oil enriched diet

High-fat diet is associated with hypercholesterolemia and seminal alterations in White New Zealand rabbits. We have previously reported disorders in the development of the manchette-acrosome complex during spermiogenesis and decreased testicular efficiency in hypercholesterolemic rabbits. On the other hand, olive oil incorporated into the diet improves cholesterolemia and semen parameters affected in hypercholesterolemic rabbits. In this paper, we report the recovery—with the addition of olive oil to diet—from the sub-cellular mechanisms involved in the shaping of the sperm cell and testicular efficiency altered in hypercholesterolemic rabbits. Using morphological (structural, ultra-structural and immuno-fluorescence techniques) and cell biology techniques, a reorganization of the manchette and related structures was observed when olive oil was added to the high-fat diet. Specifically, actin filaments, microtubules and lipid rafts—abnormally distributed in hypercholesterolemic rabbits—were recovered with dietary olive oil supplementation. The causes of the decline in sperm count were studied in the previous report and here in more detail. These were attributed to the decrease in the efficiency index and also to the increase in the apoptotic percentage in testis from animals under the high-fat diet. Surprisingly, the addition of olive oil to the diet avoided the sub-cellular, efficiency and apoptosis changes observed in hypercholesterolemic rabbits. This paper reports the positive effects of the olive oil addition to the diet in the recovery of testicular efficiency and normal sperm shaping, mechanisms altered by hypercholesterolemia.

Prohibitin-mediated mitochondrial ubiquitination during spermiogenesis in Chinese mitten crab Eriocheir sinensis

The sperm of Eriocheir sinensis has a cup-shaped nucleus that contains several mitochondria embedded at the opening of the cup. The acrosome vesicle also contains derivants of mitochondria. The mitochondria distribution pattern involves a decrease in the number and changes in the structure and transportation of these organelles. The decreased number of sperm mitochondria is achieved through autophagy or the ubiquitination pathway. Prohibitin (PHB), the mitochondria inner membrane protein, is an evolutionarily highly conserved protein, is closely associated with spermatogenesis and sperm quality control and is also a potential substrate of ubiquitination. However, whether PHB protein mediates the ubiquitination pathway of sperm mitochondria in crustacean animals remains poorly understood. In the present study, we revealed that PHB, a substrate of ubiquitin, participates in the ubiquitination and degradation of mitochondria during spermiogenesis in E. sinensis. To confirm this finding, we used shRNA interference to reduce PHB expression and an overexpression technique to increase PHB expression in vitro. The interference experiment showed that the reduced PHB expression directly affected the polyubiquitination level and mitochondria status, whereas PHB overexpression markedly increased the polyubiquitination level. In vitro experiments also showed that PHB and its ubiquitination decide the fate of mitochondria.

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.

Dynamic transcription and expression patterns of KIF3A and KIF3B genes during spermiogenesis in the shrimp, Palaemon carincauda

Spermiogenesis is a highly ordered and complex process in the male germ cell differentiation. The microtubule-based motor proteins KIF3A and KIF3B are required for the progression of the stages of spermiogenesis. In this study, the main goal was to determine whether KIF3A and KIF3B have a key role in spermiogenesis in Palaemon carincauda. The complete cDNA of KIF3A/3B from the testis of P. carincauda was cloned by using PCR and rapid amplification of cDNA ends (RACE). The predicted secondary and tertiary structures of KIF3A/3B contained three domains which were the: a) head region, b) stalk region, and c) tail region. Real-time quantitative PCR (qPCR) results revealed that KIF3A and KIF3B mRNAs were obtained for all the tissues examined, with the greatest gene expression in the testis. In situ hybridization indicated the KIF3A and KIF3B mRNAs were distributed in the periphery of the nuclear in the early spermatid of spermiogenesis. In the middle and late spermatid stages, KIF3A and KIF3B mRNAs were gradually upregulated and assembled to one side where acrosome biogenesis begins. In the mature sperm, KIF3A and KIF3B mRNAs were distributed in the acrosome cap and spike. Immunofluorescence studies indicated that KIF3A, tubulin, mitochondria, and Golgi were co-localized in different stages during spermiogenesis in P. carincauda. The temporal and spatial gene expression dynamics of KIF3A/3B indicate that KIF3A and KIF3B proteins may be involved in acrosome formation and nucleus shaping. Moreover, these proteins can transport the mitochondria and Golgi that facilitate acrosome formation in P. carincauda.

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.

Myosin superfamily: The multi-functional and irreplaceable factors in spermatogenesis and testicular tumors

Spermatogenesis is a fundamental process in sexual development and reproduction, in which the diploid spermatogonia transform into haploid mature spermatozoa. This process is under the regulation of multiple factors and pathway. Myosin has been implicated in various aspects during spermatogenesis. Myosins constitute a diverse superfamily of actin-based molecular motors that translocate along microfilament in an ATP-dependent manner, and six kinds of myosins have been proved that function during spermatogenesis. In mitosis and meiosis, myosins play an important role in spindle assembly and positioning, karyokinesis and cytokinesis. During spermiogenesis, myosins participate in acrosomal formation, nuclear morphogenesis, mitochondrial translocation and spermatid individualization. In this review, we summarize current understanding of the functions of myosin in spermatogenesis and some reproductive system diseases such as testicular tumors and prostate cancer, and discuss the roles of possible upstream molecules which regulate myosin in these processes.

Significant fluctuations in ecdysteroid receptor gene (EcR) expression in relation to seasons of molt and reproduction in the grapsid crab, Metopograpsus messor (Brachyura: Decapoda)

Metopograpsus messor, a brachyuran crab inhabiting the estuaries of North Kerala (India), is a prolific breeder releasing approximately 14-16 broods a year. The present paper reports the sequence information on the DNA binding domain (C domain, DBD), linker (D domain) and ligand binding domain (E domain, LBD) of M. messor ecdysteroid receptor (MmEcR) gene, the first grapsid brachyuran crab EcR examined. We have also measured MmEcR transcript levels in the ovary and the hepatopancreas throughout the annual cycle, with special reference to seasons of molt and reproduction. MmEcR expression in both the tissues is found to be at its peak (P<0.05) in late premolt crabs (January/May, molt/reproduction season); the expression levels are lowest (P<0.05) during June/July, when the females would neither molt nor reproduce (season for molt/reproduction repose). Intermediate levels of expression were found during the breeding season (August/December). Interestingly, this pattern of gene expression is in concordance with the fluctuating ecdysteroid levels of the hemolymph and Y organ secretory activity. The significant levels of fluctuation in the ovarian expression of MmEcR strongly suggest the ovary as a potential target for ecdysteroid action. A season-wise comparison of the gene expression reveals that ovarian MmEcR transcript levels are higher in breeding crabs (August/December) than the non-breeding animals (June/July), implicating a possible ecdysteroid role in reproduction in M. messor.

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.

Ecdysone receptor gene from the freshwater prawn Macrobrachium nipponense: identification of different splice variants and sexually dimorphic expression, fluctuation of expression in the molt cycle and effect of eyestalk ablation

The full-length cDNA of an ecdysone receptor gene (MnEcR) from Macrobrachium nipponense was cloned and the expression of the gene was investigated. MnEcR maintained a relatively low expression level in the early stages of embryos, but from nauplius stage, a steady increase in MnEcR expression was detected, it had the highest expression level in zoea stage. MnEcR was highly expressed in the hepatopancreas and gills among ten different tissues examined. MnEcR was rapidly upregulated in the premolt stage and rapidly downregulated in the postmolt stage. The expression of MnEcR was remarkably downregulated after eyestalk ablation in M. nipponense. An 18-amino-acid insertion/deletion and a 49-amino-acid substitution were found in the coding region of MnEcR, resulting in four splice variants: MnEcR-L1, -L2, -S1 and-S2. The expression of four splice variants of MnEcR in gonads was investigated using RT-PCR. Interestingly, the expression patterns of these splice variants differed between males and females. The dominant splice variants in testis were MnEcR-S1 and -S2, while in ovary they were MnEcR-L1 and -S2, indicating specific roles for these splice variants in male and female individuals.

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.

Transcriptome analysis of the oriental river prawn, Macrobrachium nipponense using 454 pyrosequencing for discovery of genes and markers

Background

The oriental river prawn, Macrobrachium nipponense, is an economically and nutritionally important species of the Palaemonidae family of decapod crustaceans. To date, the sequencing of its whole genome is unavailable as a non-model organism. Transcriptomic information is also scarce for this species. In this study, we performed de novo transcriptome sequencing to produce the first comprehensive expressed sequence tag (EST) dataset for M. nipponense using high-throughput sequencing technologies.

Methodology and Principal Findings

Total RNA was isolated from eyestalk, gill, heart, ovary, testis, hepatopancreas, muscle, and embryos at the cleavage, gastrula, nauplius and zoea stages. Equal quantities of RNA from each tissue and stage were pooled to construct a cDNA library. Using 454 pyrosequencing technology, we generated a total of 984,204 high quality reads (338.59Mb) with an average length of 344 bp. Clustering and assembly of these reads produced a non-redundant set of 81,411 unique sequences, comprising 42,551 contigs and 38,860 singletons. All of the unique sequences were involved in the molecular function (30,425), cellular component (44,112) and biological process (67,679) categories by GO analysis. Potential genes and their functions were predicted by KEGG pathway mapping and COG analysis. Based on our sequence analysis and published literature, many putative genes involved in sex determination, including DMRT1, FTZ-F1, FOXL2, FEM1 and other potentially important candidate genes, were identified for the first time in this prawn. Furthermore, 6,689 SSRs and 18,107 high-confidence SNPs were identified in this EST dataset.

Conclusions

The transcriptome provides an invaluable new data for a functional genomics resource and future biological research in M. nipponense. The molecular markers identified in this study will provide a material basis for future genetic linkage and quantitative trait loci analyses, and will be essential for accelerating aquaculture breeding programs with this species.