The concentrations of vitellogenin (vitellin) and protein in hemolymph, ovary and hepatopancreas in different ovarian stages of the freshwater prawn, Macrobrachium rosenbergii

Abundances of vitellogenin and heat shock protein 90 during ovarian and embryonic development of Exopalaemon carinicauda

To evaluate functions of vitellogenin (Vg) and heat shock protein 90 (Hsp90) during ovarian and embryonic development of Exopalaemon carinicauda, the cDNA of Vg (Ec-Vg) was cloned, and the abundances of Ec-Vg and heat shock protein 90 (Hsp90) (Ec-Hsp90) were determined during ovarian and embryonic development. During ovarian development, the concentration of Vg protein in hemolymph was markedly greater than in the ovary and hepatopancreas, and was greatest at sexual maturity. The relative abundance of Ec-Vg mRNA transcript was greatest in the hepatopancreas and almost undetectable in hemocytes. By combining mRNA transcript relative abundances with morphological results, a model was developed to explain the mRNA transcript relative abundance of Ec-Hsp90 and Ec-Vg during ovarian and embryonic development. The relative abundance of Ec-Vg mRNA transcript was greatest during the recovery period after reproduction had occurred (Stage V) and mature stage (Stage IV) in the ovary or hepatopancreas, respectively. There were marked associations of the patterns of Ec-Hsp90 and Ec-Vg mRNA transcript abundances both in hepatopancreas and ovary. During embryonic development, the relative abundance of the two mRNA transcripts were greatest at the metazoea and protozoea stages, respectively. These results indicate that Ec-Vg is produced primarily in the hepatopancreas, secreted into the hemolymph and transported into growing oocytes. It, therefore, is believed that Ec-Vg has an important function in the overall ovarian development and late embryonic development of E. carinicauda. In contrast, Ec-Hsp90 is a regulatory factor for Vg transcription and is important during early organogenesis in E. carinicauda.

Genomic structure, expression, and functional characterization of checkpoint kinase 1 from Penaeus monodon

Chk1 is a cell-cycle regulator. Chk1 has been identified in organisms ranging from yeast to humans, but few researchers have studied Chk1 in shrimps. We cloned Chk1 from the black tiger shrimp (Penaeus monodon). The full-length cDNA sequence of PmChk1 had 3,334 base pairs (bp), with an open reading frame of 1,455 bp. The complete genomic sequence of PmChk1 (11,081 bp) contained 10 exons separated by nine introns. qRT-PCR showed that PmChk1 was highly expressed in the ovaries and gills of P. monodon. The lowest PmChk1 expression was noted in stage III of ovarian development in P. monodon. PmChk1 expression decreased significantly after injection of 5-hydroxytryptamine and eyestalk ablation in P. monodon ovaries. RNA interference experiments were undertaken to examine the expression of PmChk1, PmCDC2, and PmCyclin B. PmChk1 knockdown in the ovaries and hepatopancreas by dsRNA-Chk1 was successful. The localization and level of PmChk1 expression in the hepatopancreas was studied using in situ hybridization, which showed that data were in accordance with those of qRT-PCR. The Gonadosomatic Index of P. monodon after dsRNA-Chk1 injection was significantly higher than that after injection of dsRNA-GFP or phosphate-buffered saline. These data suggest that PmChk1 may have important roles in the ovarian maturation of P. monodon.

Controversial use of vitellogenin as a biomarker of endocrine disruption in crustaceans: New adverse pieces of evidence in the copepod Eurytemora affinis

In recent years, the interest in the use of vitellogenin (VTG) as a biomarker of endocrine disruption in fish has led to VTG being considered as a potential tool in invertebrates. Among aquatic invertebrate models in ecotoxicology, the copepods are considered as reference species in marine, estuarine and freshwater ecosystems. In this context, we identified a VTG cDNA in Eurytemora affinis. The Ea-VTG2 cDNA is 5416bp in length with an open reading frame (ORF) of 5310bp that encodes a putative protein of 1769 amino acids residues. Phylogenetic analysis confirmed the hypothesis of a VTG duplication event before the emergence of the copepod species. The analysis of the Ea-VTG2 expression by qPCR in males and females according to their reproductive stages allowed transcript basal levels to be determined. The expression pattern revealed a gradual increase of transcript levels during maturation in females. Important inter-sex differences were observed with a VTG level in males ranging from about 1900- to 6800-fold lower than in females depending on their stage. Moreover, the protein was only detected in ovigerous females. The inducibility of Ea-VTG2 by chemicals was studied in males exposed to either a model of endocrine disruptor in vertebrates i.e. 4-nonylphenol (4-NP) or a crustacean hormone i.e. Methyl Farnesoate (MF), and in males sampled from a multi-contaminated estuary. No induction was highlighted. The VTG should not be considered as an appropriate biomarker in E. affinis as previously suggested for other crustaceans.

Genomic structure, expression pattern, and functional characterization of transcription factor E2F-2 from black tiger shrimp (Penaeus monodon)

Transcription factor E2F-2 is a regulator of cell cycle. Researchers identified E2F-2 genes from yeasts to humans, but few reports investigated E2F-2 gene from black tiger shrimp. In the present study, we cloned E2F-2 gene from black tiger shrimp (Penaeus monodon). Full-length PmE2F-2 complementary DNA sequence measures 3,189 bp with an open reading frame of 1,371 bp. Complete PmE2F-2 genomic sequence (17,305 bp) of P. monodon contains nine exons, which are separated by eight introns. Quantitative real-time polymerase chain reaction (qRT-PCR) analysis indicated that PmE2F-2 is highly expressed in hepatopancreas and ovaries of P. monodon. Highest PmE2F-2 expression levels were observed in stage III ovarian development of P. monodon. PmE2F-2 expression levels were significantly augmented in ovaries of P. monodon after 5-hydroxytryptamine injection and eyestalk ablation. RNA interference experiments were conducted to examine PmE2F-2, PmCDK2, and PmCyclin E expression profiles. PmE2F-2 was successfully knocked down in ovaries and hepatopancreas via double-stranded RNA (dsRNA)-E2F-2 injection. In the same organs, PmE2F-2 expression localization and level were investigated through in situ hybridization, which revealed consistent results with those of qRT-PCR. After dsRNA-E2F-2 injection, gonadosomatic index of shrimp was significantly lower than those following dsRNA-GFP and phosphate-buffered solution injections. Therefore, PmE2F-2 may be involved in ovarian maturation in P. monodon.

Vitellogenin-like gene expression in freshwater amphipod Gammarus fossarum (Koch, 1835): functional characterization in females and potential for use as an endocrine disruption biomarker in males

The induction of vitellogenin (Vtg) synthesis is widely accepted as a biomarker of estrogenic exposure in male and juvenile fish. Vtg synthesis has emerged as an interesting endpoint to assess endocrine disruptor (ED) effects in crustaceans. However, studies reporting induction of Vtg in male crustaceans are lacking. This study investigated the expression of the Vtg gene in a freshwater amphipod, Gammarus fossarum, using calibrated real-time reverse transcription polymerase chain reaction (real-time RT PCR). First, we described the basal pattern of expression in healthy male and female organisms at different reproductive moult stages, in order to validate the function of this gene. Females expressed from 200 to 700 times more Vtg transcripts than males, depending on the female reproductive stage. Females displayed significant elevation of Vtg mRNA levels at the end of the inter-moult phase and at the beginning of the pre-moult phase. Second, male gammarids were exposed to the estrogenic compound nonylphenol (NP) (0.05, 0.5, 5 and 50 μg L(-1)) and to the anti-androgen cyproterone (1, 10, 100 and 1000 μg L(-1)) for 2, 4, 8 and 16 days. Both chemicals altered the pattern of interindividual variability of Vtg gene expression in males with strong induction in some individuals. Finally, the impact of urban wastewater treatment plants (WWTP) on male Vtg gene expression was assessed in organisms transplanted in the field during in situ bioassay campaigns in three different watersheds. Induction of the Vtg mRNA level was observed in males transplanted downstream from WWTP effluent discharge in two of the three study sites.

Characterization of vitellin from the ovaries of the banana shrimp Litopenaeus merguiensis

Vitellin (Vt) was purified from ovary extracts of mature females of the banana shrimp Litopenaeus merguiensis using DEAE-Sephacel and Superdex 200 columns. Native Vt had an apparent molecular mass of 398 kDa as determined by native PAGE and by gel filtration chromatography. Under reducing and denaturing conditions (SDS-PAGE), Vt is composed of two major subunits of 87 and 78 kDa, although some faint bands were also detected. The N-terminal 10 amino acids sequence of the 78 kDa subunit is identical to that of Litopenaeus vannamei Vt and very similar to that of Litopenaeus japonicus vitellogenin (Vg) as well as Litopenaeus semisulcatus Vt, with an identity of 89%. Anti-Vt polyclonal antibody raised against purified Vt shows a high specificity with only ovarian Vt and hemolymph Vg of vitellogenic shrimps in double immunodiffusion and Western blot assays. Vg and Vt concentrations in hemolymph, hepatopancreas and ovaries were measured by ELISA. Vg concentrations increased in the hemolymph in the early stages of ovarian development and declined in the maturation stages. As there were undetectable concentrations of Vg in the hepatopancreas while an elevation of Vg levels occurred in the hemolymph, during the time that Vt was accumulating in the ovaries during oogenesis, this would suggest that the contribution of Vg synthesized by the hepatopancreas only might be not sufficient for adequate development of the oocytes in the banana shrimp L. merguiensis during vitellogenesis.

Development of a quantitative enzyme-linked immunosorbent assay for vitellin in the mysid Neomysis integer (Crustacea: Mysidacea)

Mysid crustaceans have been put forward by several regulatory bodies as suitable test organisms to screen and test the potential effects of environmental endocrine disruptors. Despite the well-established use of mysid reproductive endpoints such as fecundity, egg development time, and time to first brood release in standard toxicity testing, little information exists on the hormonal regulation of these processes. Control of vitellogenesis is being studied intensively because yolk is an excellent model for studying mechanisms of hormonal control, and vitellogenesis can be chemically disrupted. Yolk protein or vitellin is a major source of nourishment during embryonic development of ovigorous egg-laying invertebrates. The accumulation of vitellin during oocyte development is vital for the production of viable offspring. In this context, we developed a competitive enzyme-linked immunosorbent assay (ELISA) for vitellin of the estuarine mysid Neomysis integer. Mysid vitellin was isolated using gel filtration, and the purified vitellin was used to raise polyclonal antibodies. The ELISA was sensitive within a working range of 4 to 500 ng vitellin/mL. Serial dilutions of whole body homogenates from female N. integer and the vitellin standard showed parallel binding curves, validating the specificity of the ELISA. The intra- and interassay coefficients of variation were 8.2% and 13.8%, respectively. Mysid vitellin concentrations were determined from ovigorous females and eggs at different developmental stages. The availability of a quantitative mysid vitellin ELISA should stimulate further studies on the basic biology of this process in mysids. Furthermore, it could provide a means to better understand and predict chemically induced reproductive effects in mysids.

Vitellogenin mRNA expression in Cherax quadricarinatus during secondary vitellogenic at first maturation females

PCR products of 1.1 and 0.9 kb were generated using Cherax quadricarinatus genomic DNA in the first case, and hepatopancreas and ovary cDNAs in the second case. These PCR products were cloned and analyzed for nucleotide sequences. The 1.1 kb fragment was used as a probe for Northern hybridization, revealing a transcript of approximately 8 kb in both tissues. Results from both Northern blot and RT-PCR analyses showed that the mRNA enconding the 3' end of the vitellogenin cDNA was present simultaneously in both hepatopancreas and ovary tissues in secondary vitellogenic at first maturation females, but was not detected in male hepatopancreas. The deduced amino acid sequences of Vitellogenin (Vg) cDNAs from ovary and hepatopancreas confirmed the existence at least two different Vg genes, and two different sites of synthesis.

Purification and characterization of vitellin from the estuarine mysid Neomysis integer (Crustacea; Mysidacea)

Invertebrates account for roughly 95% of all animals, yet surprisingly, little effort has been invested to understand their value in signaling potential environmental endocrine disruption. There has been, however, much recent attention on vitellogenin induction in egg-laying invertebrates and vertebrates as indicators of exposure to estrogenic xenobiotics. Mysid shrimp (Crustacea: Mysidacea) have been put forward by several researchers and regulatory bodies (e.g., US-EPA) as suitable test organisms for the evaluation of environmental endocrine disruption. In view of developing sensitive assays to study endocrine disruption in the estuarine mysid Neomysis integer, we isolated and characterized vitellin, the major yolk protein in eggs. Vitellin was purified using gel filtration and characterized by electrophoresis using different staining procedures. Specific (as shown by Western blotting) polyclonal antibodies were produced in rabbit against the purified vitellin of N. integer. These antisera will be used to develop immunoassays to study vitellogenesis in mysids and to detect potential stimulatory or inhibitory effects of endocrine disruptors on the production of vitellin.

Purification of vitellin from the ovary of Chinese mitten-handed crab (Eriocheir sinensis) and development of an antivitellin ELISA

Vitellin was purified from ovaries of mature female Chinese mitten-handed crab (Eriocheir sinensis) using gel filtration chromatography. Analysis by native PAGE showed the vitellin had a native molecular mass of 520 kDa, while denaturing SDS-PAGE revealed two subunits of 97 and 74 kDa. Purified vitellin was used to raise polyclonal antisera, with which an enzyme-linked immunosorbent assay (ELISA) was developed. The ELISA was sensitive and could effectively detect vitellin in the range of 7.8-500 ng. Furthermore, vitellin levels in various developmental stages of oogenesis were measured with the ELISA assay. The results indicated that levels of vitellin increased significantly from 0.22 mg/ovary at Stage II to 360.31 mg/ovary at Stage IV.

Localization of vitellogenin mRNA expression and vitellogenin uptake during ovarian maturation in the giant freshwater prawn Macrobrachium rosenbergii

In situ hybridization and immunohistochemical techniques were used to investigate the dynamics of vitellogenin (Vg) mRNA expression and Vg uptake during ovarian maturation in the hepatopancreas and ovary at differing stages of ovarian maturation in both intact and eyestalk ablated female Macrobrachium rosenbergii. In the hepatopancreas of intact animals, Vg mRNA expression was detected faintly two days after ecdysis, and signals showed a gradual increase as the molt cycle advanced to the premolt stages, but decreased at the late premolt stage. Vg mRNA was detected in the R-cells of the hepatopancreas, indicating that these cells are responsible for synthesizing Vg. No Vg mRNA expression was observed in the ovary. Immunohistochemistry results for the hepatopancreas showed a pattern of staining intensity similar to that of in situ hybridization. Increases in the accumulation of yolk protein in the oocytes occurred concomitantly with increasing Vg mRNA expression. In eyestalk ablated animals, Vg mRNA expression and Vg uptake showed similar but accelerated patterns to those of intact animals. This study has confirmed on the cellular level previous results that Vg synthesis is intrinsically correlated to ovarian maturation and the molt cycle in M. rosenbergii.

Yolk proteins during ovary and egg development of mature female freshwater crayfish (Cherax quadricarinatus)

Vitellins from ovaries and eggs at different stages of development in freshwater crayfish (Cherax quadricarinatus) were examined by chromatography, PAGE and SDS-PAGE. With these methods, two forms of vitellin (Vt1 and Vt2) were observed in ovaries and eggs (stages I and V). In ovaries in secondary vitellogenesis, native molecular mass was 470 (Vt1) and 440 (Vt2) kDa. The electrophoretic pattern of the eggs proved to be more complex. The protein molecular mass depend on the development stage of the egg: stage I, 650 kDa (Vt1) and 440 kDa (Vt2); stage V, 390 kDa (Vt1) and 340 kDa (Vt2). The identified vitellins appear to be lipo-glycocarotenoprotein. A similar vitellin polypeptide composition was observed in the two forms of vitellin from ovaries and eggs in stage V. In ovaries the SDS-PAGE analysis showed four subunits with molecular weights of approximately 180, 120, 95 and 80 kDa (Vt1 and Vt2). The polypeptide composition in the two forms of vitellins in stage I and stage III eggs were different at 195, 190, 130 and 110 kDa (Vt1) and 116 and 107 kDa (Vt2). On the other hand, in stage V eggs, 110, 95, 87 and 75 kDa (Vt1 and Vt2) were identified. Two antibodies (Ab1 and Ab2) were prepared against the purified proteins of stage V eggs and their specificity was demonstrated by radial immunoprecipitation, and Western blotting analysis. Two forms of vitellins were also found in stage V eggs after chromatography on Sepharose CL-2B column and hydroxylapatite and polyacrylamide gel electrophoresis.

Dynamics of vitellogenin mRNA expression and changes in hemolymph vitellogenin levels during ovarian maturation in the giant freshwater prawn Macrobrachium rosenbergii

The dynamics of vitellogenin mRNA expression during ovarian maturation in Macrobrachium rosenbergii were examined by measuring hemolymph vitellogenin (Vg) levels and Vg mRNA expression in the hepatopancreas and ovary at differing reproductive stages in both intact and eyestalk ablated animals. Vg mRNA was quantified using real-time RT-PCR and hemolymph Vg was measured by enzyme immunoassay. In intact animals, Vg mRNA levels in the hepatopancreas and hemolymph Vg levels showed a gradual increase during the molt cycle concomitant with increasing gonadosomatic index (GSI), with Vg levels decreasing prior to ecdysis although GSI continued to increase. Eyestalk ablation was seen to accelerate Vg synthesis as well as ovarian maturation, although it did not alter the overall pattern of Vg expression. Vg mRNA expression was negligible in the ovary of both intact and eyestalk ablated animals, confirming that the hepatopancreas is the principal site of Vg synthesis in M. rosenbergii with the ovary being only a minor contributor. This study has shown that Vg synthesis is correlated to ovarian maturation and the molt cycle in M. rosenbergii.

Molecular characterization of vitellin from the ovaries of the white shrimp Penaeus (Litopenaeus) vannamei

Vitellin (Vt) was purified from ovary extracts of mature females of the white shrimp Penaeus vannamei using Sepharose CL-4B and Q-Sepharose columns. Native Vt had an apparent molecular weight of 388 kDa as detected in Native-PAGE, bound the lipophilic dye Oil Red O and had a total lipid content of approximately 43.8%. Under reducing and denaturing conditions (SDS-PAGE), Vt is composed of three major subunits of 87, 78 and 46 kDa, although minor bands of 65, 61 and 31 kDa are also detected. The 87- and 78-kDa polypeptides were strongly recognized by Penaeus semisulcatus anti-Vt polyclonal and Penaeus monodon anti-Vt monoclonal antibodies. Furthermore, the N-terminal amino acid sequence of the 78-kDa polypeptide is very similar to Penaeus japonicus vitellogenin (Vg) and P. semisulcatus Vt, with an identity of 76%. Circular dichroism indicates that the beta-helix content of Vt is 25% while beta-sheets correspond to 37 and 14% of unordered secondary structure. These values are similar to insect microvitellogenin. Vt has an emission fluorescence maximum at 329 nm, comparable to the shrimp high-density lipoprotein/beta-glucan binding protein (HDL/BGBP).

Hepatopancreas is the likely organ of vitellogenin synthesis in the freshwater prawn, Macrobrachium rosenbergii

The objective of the present study was to investigate the source of vitellogenin in the freshwater prawn, Macrobrachium rosenbergii. Ovarian development of M. rosenbergii was classified into five stages (stage I-V). Vitellin/vitellogenin was detected in the ovary and the hepatopancreas in different stages by native-PAGE and Western blotting. Two and three subunits of vitellin were observed in the ovary at the early- (I-II), mid- and late- (III-V) stages, respectively. The subunit of vitellogenin was not detected in the hepatopancreas at different stages of prawns. Hepatopancreas had positive immunocytological staining (against vitellin antibody) in different ovarian stages of prawn. Only vitellogenic oocyte but not previtellogenic oocytes and follicle cells had a positive immunocytological staining. Hepatopancreas could synthesize radiolabeled immunoreactive proteins after incubation with radiolabeled glycine on the basis of immunoprecipitation (against vitellin antiserum). Therefore, it is concluded that hepatopancreas is the most likely organ to synthesize vitellogenin in the freshwater prawn, M. rosenbergii.

Site of vitellogenin synthesis determined from a cDNA encoding a vitellogenin fragment in the freshwater giant prawn, Macrobrachium rosenbergii

Vitellogenesis is an important part of reproductive process in crustaceans, and the process is characterized by the synthesis and accumulation of yolk protein in the developing oocytes. The yolk proteins in crustaceans mainly consist of vitellogenin (Vg) and vitellin (Vn), which are respectively present in extra-oocyte tissues and intra-oocytes. The site and the process of yolk protein synthesis in crustaceans are still controversial. The synthesis site of Vg in a crustacean species, Macrobrachium rosenbergii, is determined by immunological and immunohistochemical techniques, and molecular cloning of a cDNA encoding the primary structure of Vn in this study. The hepatopancrease is clearly shown to be the synthesis site of Vg in this species. The length of Vg mRNA was estimated as about 6 kb from Northern blotting analysis. The partial primary structure of Vg gene is presented, and the post-translational processing are further discussed. For the first time, the partial primary structure of Vg gene and the synthesis site of Vg approached by molecular cloning in crustaceans are presented.

A newly established ELISA showing the effect of the androgenic gland on secondary-vitellogenic-specific protein in the hemolymph of the crayfish Cherax quadricarinatus

A quantitative enzyme-linked immunosorbent assay (ELISA) was developed to monitor the onset of secondary vitellogenesis in Cherax quadricarinatus females and in intersex individuals (having both male and female reproductive systems) after removal of the androgenic gland (AG). As a prerequisite for the assay, the 106-kDa polypeptide was separated from newly laid C. quadricarinatus eggs by SDS-PAGE, and anti-106-kDa antibody was raised in rabbit. The specificity of the anti-106-kDa polypeptide for proteins specific for the hemolymph of secondary-vitellogenic females was confirmed by double immunodiffusion and immunoblot cross-reactivity tests. A characteristic standard ELISA curve, using egg high-density lipoprotein (HDL), showed linearity between 16 and 500 ng (r = 0. 953) and was sensitive for amounts as low as 8 ng. The inter- and intraassay coefficients of variance were 14.8 and 7.2%, respectively. Only traces of egg HDL equivalents were detected in the hemolymph of male and primary-vitellogenic females (11 to 110 microg/ml), confirming the specificity of the assay, whereas high levels of such a protein (8-35 mg/ml) were detected in the hemolymph of secondary-vitellogenic females. Removal of the AG from intersex individuals leads to a significant increase in the concentration of vitellogenic-specific protein in the hemolymph (up to 2 mg/ml). Moreover, a significantly lower concentration was found in females subjected to AG transplant (79.3 microg/ml). The ELISA thus provided an accurate and sensitive tool to investigate the influence of the AG on the expression of a vitellogenic-specific protein in female and intersex C. quadricarinatus, confirming the central role of this gland in tuning sexual plasticity in this species.

Isolation and characterization of the female-specific protein (vitellogenin) in mature female hemolymph of the freshwater prawn, Macrobrachium rosenbergii: comparison with ovarian vitellin

Purification and characterization of the female-specific protein (vitellogenin) from the hemolymph of mature female prawn, Macrobrachium rosenbergii, were the objectives of this study. The comparison of biochemical characteristics between vitellogenin and ovarian vitellin was also conducted. Hemolymph vitellogenin was purified with DEAE, hydroxylapatite, and another DEAE chromatographic column. The specific protein (vitellogenin) was shown in the fractions of chromatographic columns on the basis of ELISA, Western blotting, and immunoprecipitation. A purified vitellogenin was obtained with an apparent molecular weight of 700 kDa as determined by PAGE. The purified vitellogenin was considered as a lipoglycoprotein on the basis of staining data. Three subunits (170, 100, and 89 kDa) in purified vitellogenin and two subunits (100 and 89 kDa) in vitellin were detected with SDS-PAGE. Nondisulfide bonds were found in the binding of polypeptide subunits. Only the 89-kDa subunit was a glycopolypeptide in both vitellogenin and vitellin. The amino acid composition of vitellogenin differed from that of vitellin in a few amino acids. Eight amino acid sequences from the N-terminal end of 89- and 100-kDa subunits were determined and they were identical between vitellogenin and vitellin. Seven amino acid sequence from the N-terminal end of the 170-kDa subunit were also identical to the 100-kDa subunit. Purified vitellogenin was more susceptible to precipitation in a solution with low ionic strength than vitellin. This study suggests a close relationship between vitellogenin and vitellin in M. rosenbergii in their biochemical characteristics.