A crayfish insulin-like-binding protein: another piece in the androgenic gland insulin-like hormone puzzle is revealed

The Masculinizing gene is a candidate male pathway developmental factor in the mud crab Scylla paramamosain

The Masculinizer (Masc) gene plays a crucial role in masculinization during insect embryonic gonadal development. Nevertheless, the Masc expression pattern and function in crabs remain largely unknown. In the present study, we screened and validated the Masc gene from transcriptome data of mud crab S. paramamosain. The Masc relative transcript level in the testis was significantly higher than that of ovaries and other tissues, as measured by quantitative real-time PCR. In situ hybridization showed that Masc exhibited a significant signal throughout all stages of testicular development. The phylogenetic analysis revealed conservation in the evolution of crustaceans, potentially indicating its functional importance. Masc RNA interference showed that the expression of testis bias-related genes decreased significantly while the ovary bias-related genes increased significantly. Transcriptome data suggested that Masc regulates several signaling pathways, including the mTOR, Wnt, insulin, and other sex-related pathways. These results indicate that Masc may play a role in mud crab male development with possible application in sex control in aquaculture.

A study on the functional role of the DHCR24 gene in gonadal differentiation and development of Macrobrachium nipponense

Sex differentiation in crustaceans is a complex process influenced by various factors, including the androgenic gland and sex-related genes. This study characterized the role of the Mn-DHCR24 gene in the oriental river prawn (Macrobrachium nipponense). We used bioinformatics to analyze sequence features and phylogenetic relationships of a single Mn-DHCR24 gene. The expression patterns of Mn-DHCR24 across different tissues and developmental stages were determined by real-time PCR, and its localization in testis was determined by in situ hybridization. RNA interference was used to knock down Mn-DHCR24 expression, followed by examining changes in sex ratio and gonadal development at the PL10 stage. Additionally, an enzyme-linked immunosorbent assay measured 17α-methyltestosterone levels, and tissue sections were used to characterize gonadal development. The results indicated that Mn-DHCR24 was high expression in testis, which was critical for sperm maturation and gonadal differentiation. RNAi experiments showed the role of Mn-DHCR24 during reproductive regulation rather than as a master gene for sex differentiation. This study further showed that Mn-DHCR24 regulated sex and hormone-related genes, influencing steroid biosynthesis pathways. Together, these findings provided valuable insights into the genetic and hormonal mechanisms of gonadal differentiation in M. nipponense, and supported the development of monosex culture technology.

The effects of Panax ginseng on growth enhancement, innate immunity, and microbiome profiling in Penaeus vannamei

Background

In aquaculture, feed additives are widely explored. Among them, Panax ginseng Meyer, a natural herbal remedy, has demonstrated its efficacy in many aquaculture species. However, research regarding Penaeus vannamei shrimp, one of the most significant species in aquaculture, remains limited.

Methods

This study investigates the benefits of P. ginseng for P. vannamei, specifically its effects on growth, innate immunity, and shrimp microbiome. Juvenile P. vannamei were fed commercial feed mixed with red ginseng extract at 5 concentrations (0.00 %, 0.05 %, 0.10 %, 0.50 %, and 1.00 %) for 6 weeks. Body weight was measured on days 21 and 42. On day 42, three shrimp per group were selected for further analysis.

Results

In the growth study, Group 0.10 % displayed significantly improved FBW, WG, SGR, and FCR compared to those in Group 0.00 % on day 42. The qPCR assay showed significantly higher IGF-BP gene expression in Groups 0.05 %, 0.10 %, and 1.00 % compared to Group 0.00 %. In the innate immunity analysis, SOD activity was significantly higher in Groups 0.05 % and 0.50 % compared to that in Group 0.00 %. In the bacterial community analysis, Group 0.10 % exhibited higher Flavobacteriaceae and lower Vibrionaceae at the family level compared to Group 0.00 %. At the genus level, Group 0.10 % showed increased unspecified Flavobacteriaceae and decreased Vibrio compared to Group 0.00 %.

Conclusion

Adding P. ginseng to the feed enhanced growth, immune response, and microbiome composition in P. vannamei. Further research on refining dosage levels and utilizing red ginseng residues could boost commercial productivity and economic benefits in aquaculture practices.

Transcriptomic Analysis across Crayfish (Cherax quadricarinatus) Claw Regeneration Reveals Potential Stem Cell Sources for Cultivated Crustacean Meat

In the face of rising global demand and unsustainable production methods, cultivated crustacean meat (CCM) is proposed as an alternative means to produce delicious lobster, shrimp, and crab products. Cultivated meat requires starting stem cells that may vary in terms of potency and the propensity to proliferate or differentiate into myogenic (muscle-related) tissues. Recognizing that regenerating limbs are a non-lethal source of tissue and may harbor relevant stem cells, we selected those of the crayfish Cherax quadricarinatus as our model. To investigate stem cell activity, we conducted RNA-Seq analysis across six stages of claw regeneration (four pre-molt and two post-molt stages), along with histology and real-time quantitative PCR (qPCR). Our results showed that while genes related to energy production, muscle hypertrophy, and exoskeletal cuticle synthesis dominated the post-molt stages, growth factor receptors (FGFR, EGFR, TGFR, and BMPR) and those related to stem cell proliferation and potency (Cyclins, CDKs, Wnts, C-Myc, Klf4, Sox2, PCNA, and p53) were upregulated before the molt. Pre-molt upregulation in several genes occurred in two growth peaks; Stages 2 and 4. We therefore propose that pre-molt limb regeneration tissues, particularly those in the larger Stage 4, present a prolific and non-lethal source of stem cells for CCM development.

Considerations for cultivated crustacean meat: potential cell sources, potential differentiation and immortalization strategies, and lessons from crustacean and other animal models

Cultivated crustacean meat (CCM) is a means to create highly valued shrimp, lobster, and crab products directly from stem cells, thus removing the need to farm or fish live animals. Conventional crustacean enterprises face increasing pressures in managing overfishing, pollution, and the warming climate, so CCM may provide a way to ensure sufficient supply as global demand for these products grows. To support the development of CCM, this review briefly details crustacean cell culture work to date, before addressing what is presently known about crustacean muscle development, particularly the molecular mechanisms involved, and how this might relate to recent work on cultivated meat production in vertebrate species. Recognizing the current lack of cell lines available to establish CCM cultures, we also consider primary stem cell sources that can be obtained non-lethally including tissues from limbs which are readily released and regrown, and putative stem cells in circulating hemolymph. Molecular approaches to inducing myogenic differentiation and immortalization of putative stem cells are also reviewed. Finally, we assess the current status of tools available to CCM researchers, particularly antibodies, and propose avenues to address existing shortfalls in order to see the field progress.

Identification of a Putative CFSH Receptor Inhibiting IAG Expression in Crabs

The crustacean female sex hormone (CFSH) is a neurohormone peculiar to crustaceans that plays a vital role in sexual differentiation. This includes the preservation and establishment of secondary female sexual traits, as well as the inhibition of insulin-like androgenic gland factor (IAG) expression in the androgenic gland (AG). There have been no reports of CFSH receptors in crustaceans up to this point. In this study, we identified a candidate CFSH receptor from the mud crab Scylla paramamosain (named Sp-SEFIR) via protein interaction experiments and biological function experiments. Results of GST pull-down assays indicated that Sp-SEFIR could combine with Sp-CFSH. Findings of in vitro and in vivo interference investigations exhibited that knockdown of Sp-SEFIR could significantly induce Sp-IAG and Sp-STAT expression in the AG. In brief, Sp-SEFIR is a potential CFSH receptor in S. paramamosain, and Sp-CFSH controls Sp-IAG production through the CFSH-SEFIR-STAT-IAG axis.

IAG Regulates the Expression of Cytoskeletal Protein-Encoding Genes in Shrimp Testis

Insulin-like androgenic gland hormone (IAG) is the master regulator of sexual differentiation and testis development in male crustaceans. However, the molecular mechanism on how IAG functions during testis development is still largely unknown. Here, the transcriptional changes were analyzed in the testes of shrimp after LvIAG knockdown in Litopenaeus vannamei. Differential expression analysis identified 111 differentially expressed genes (DEGs), including 48 upregulated DEGs and 63 downregulated DEGs, in testes of shrimp after LvIAG knockdown. Gene ontology (GO) analysis showed that these DEGs were apparently enriched in cytoskeleton-related GO items. Gene function analysis showed that genes enriched in these GO items mainly encoded actin, myosin, and heat shock protein. Interestingly, these genes were all downregulated in testis after LvIAG knockdown, which was confirmed by qRT-PCR detection. Furthermore, injection of LvIAG protein that was recombinantly expressed in insect cells upregulated the expression levels of these genes. The present study revealed that shrimp IAG might function in testis development through regulating the expression of cytoskeletal protein-encoding genes, which would provide new insights into understanding the functional mechanisms of IAG on male sexual development of crustaceans.

Transcriptomic Changes Following Induced De-Masculinisation of Australian Red Claw Crayfish Cherax quadricarinatus

The Australian red claw crayfish Cherax quadricarinatus, an emerging species within the freshwater aquaculture trade, is not only an ideal species for commercial production due to its high fecundity, fast growth, and physiological robustness but also notoriously invasive. Investigating the reproductive axis of this species has been of great interest to farmers, geneticists, and conservationists alike for many decades; however, aside from the characterisation of the key masculinising insulin-like androgenic gland hormone (IAG) produced by the male-specific androgenic gland (AG), little remains known about this system and the downstream signalling cascade involved. This investigation used RNA interference to silence IAG in adult intersex C. quadricarinatus (Cq-IAG), known to be functionally male but genotypically female, successfully inducing sexual redifferentiation in all individuals. To investigate the downstream effects of Cq-IAG knockdown, a comprehensive transcriptomic library was constructed, comprised of three tissues within the male reproductive axis. Several factors known to be involved in the IAG signal transduction pathway, including a receptor, binding factor, and additional insulin-like peptide, were found to not be differentially expressed in response to Cq-IAG silencing, suggesting that the phenotypic changes observed may have occurred through post-transcriptional modifications. Many downstream factors displayed differential expression on a transcriptomic level, most notably related to stress, cell repair, apoptosis, and cell proliferation. These results suggest that IAG is required for sperm maturation, with necrosis of arrested tissue occurring in its absence. These results and the construction of a transcriptomic library for this species will inform future research involving reproductive pathways as well as biotechnological developments in this commercially and ecologically significant species.

Molecular identification and putative role of insulin growth factor binding protein-related protein (IGFBP-rp) in the swimming crab Portunus trituberculatus

The insulin-like growth factor/insulin-like polypeptide (IGF/ILP) signaling is vital for growth, physiological metabolism, development, and reproduction. Insulin-like growth factor-binding protein (IGFBP) is involved in the insulin signaling pathway in both vertebrates and invertebrates and is critical for various physiology functions. Herein, we cloned and characterized the full-length cDNA of IGFBP-rp in the swimming crab, Portunus trituberculatus (PtIGFBP-rp). The deduced amino acid sequence of PtIGFBP-rp was found to contain three key domains (insulin-like binding (IB) domain, the kazale-type serine protease inhibitor (KAZAL) domain, and the immunoglobulin-like C2 (IGc2) domain). Results showed that PtIGFBP-rp shared the same expression pattern as P. trituberculatus insulin androgenic gland hormone (PtIAG) transcripts during the embryonic larval, juvenile crab stage and the androgenic gland (AG) developmental cycle. Moreover, PtIGFBP-rp transcripts were also present in high abundance in hepatopancreas, muscle, and androgenic glands. The regulatory relationship between PtIGFBP-rp and PtIAG was investigated by RNA interference and co-localization assays, which showed a co-localization relationship and feedback regulation between them. Bilateral eye stalk ablation (ESA) increased the expression of PtIGFBP-rp in the AG at 7 d after surgery. These results demonstrate the involvement of PtIGFBP-rp in the signaling regulatory network of IAG in P. trituberculatus.

Insulin-like growth factor signalling and its significance as a biomarker in fish and shellfish research

The insulin-like growth factor signalling system comprises insulin-like growth factors, insulin-like growth factor receptors and insulin-like growth factor-binding proteins. Along with the growth hormones, insulin-like growth factor signalling is very pivotal in the growth and development of all vertebrates. In fishes, insulin-like growth factors play an important role in osmoregulation, besides the neuroendocrine regulation of growth. Insulin-like growth factor concentration in plasma can assess the growth in fishes and shellfishes and therefore widely applied in nutritional research as an indicator to evaluate the performance of selected nutrients. The present review summarizes the role of insulin-like growth factor signalling in fishes and shellfishes, its significance in aquaculture and in evaluating growth, reproduction and development, and discusses the utility of this system as biomarkers for early indication of growth in aquaculture.

Feminising Wolbachia disrupt Armadillidium vulgare insulin-like signalling pathway

The endosymbiont Wolbachia feminises male isopods by making them refractory to the insulin-like masculinising hormone, which shunts the autocrine development of the androgenic glands. It was, therefore, proposed that Wolbachia silences the IR receptors, either by preventing their expression or by inactivating them. We describe here the two IR paralogs of Armadillidium vulgare. They displayed a conventional structure and belonged to a family widespread among isopods. Av-IR1 displayed an ubiquist expression, whereas the expression of Av-IR2 was restricted to the gonads. Both were constitutively expressed in males and females and throughout development. However, upon silencing, altered gland physiology and gene expression therein suggested antagonistic roles for Av-IR1 (androinhibiting) and Av-IR2 (androstimulating). They may function in tandem with regulating neurohormones, as a conditional platform that conveys insulin signalling. Wolbachia infection did not alter their expression patterns: leaving the IRs unscathed, the bacteria would suppress the secretion of the neurohormones, thus inducing body-wide IR deactivation and feminisation. Adult males injected with Wolbachia acquired an intersexed physiology. Their phenotypes and gene expressions mirrored the silencing of Av-IR1 only, suggesting that imperfect feminisation stems from a flawed invasion of the androstimulating centre, whereas in fully feminised males invasion would be complete in early juveniles. TAKE AWAY: Two antagonistic Insulin Receptors were characterised in Armadillidium vulgare. The IRs were involved in androstimulating and androinhibiting functions. Wolbachia-induced feminisation did not prevent the expression of the IRs. Imperfectly feminised intersexes phenocopied the silencing of Av-IR1 only. Wolbachia would deactivate the IRs by suppressing neurosecretory co-factors.

Insulin-Like Peptide Receptor-Mediated Signaling Pathways Orchestrate Regulation of Growth in the Pacific Oyster (Crassostrea gigas), as Revealed by Gene Expression Profiles

The involvement of insulin/insulin-like growth factor signaling (IIS) pathways in the growth regulation of marine invertebrates remains largely unexplored. In this study, we used a fast-growing Pacific oyster (Crassostrea gigas) variety “Haida No.1” as the material with which to unravel the role of IIS systems in growth regulation in oysters. Systematic bioinformatics analyses allowed us to identify major components of the IIS signaling pathway and insulin-like peptide receptor (ILPR)-mediated signaling pathways, including PI3K-AKT, RAS-MAPK, and TOR, in C. gigas. The expression levels of the major genes in IIS and its downstream signaling pathways were significantly higher in “Haida No.1” than in wild oysters, suggesting their involvement in the growth regulation of C. gigas. The expression profiles of IIS and its downstream signaling pathway genes were significantly altered by nutrient abundance and culture temperature. These results suggest that the IIS signaling pathway coupled with the ILPR-mediated signaling pathways orchestrate the regulation of energy metabolism to control growth in Pacific oysters.

The Chinese mitten crab genome provides insights into adaptive plasticity and developmental regulation

The infraorder Brachyura (true or short-tailed crabs) represents a successful group of marine invertebrates yet with limited genomic resources. Here we report a chromosome-anchored reference genome and transcriptomes of the Chinese mitten crab Eriocheir sinensis, a catadromous crab and invasive species with wide environmental tolerance, strong osmoregulatory capacity and high fertility. We show the expansion of specific gene families in the crab, including F-ATPase, which enhances our knowledge on the adaptive plasticity of this successful invasive species. Our analysis of spatio-temporal transcriptomes and the genome of E. sinensis and other decapods shows that brachyurization development is associated with down-regulation of Hox genes at the megalopa stage when tail shortening occurs. A better understanding of the molecular mechanism regulating sexual development is achieved by integrated analysis of multiple omics. These genomic resources significantly expand the gene repertoire of Brachyura, and provide insights into the biology of this group, and Crustacea in general.

Sex Determination and Differentiation in Decapod and Cladoceran Crustaceans: An Overview of Endocrine Regulation

Mechanisms underlying sex determination and differentiation in animals are known to encompass a diverse array of molecular clues. Recent innovations in high-throughput sequencing and mass spectrometry technologies have been widely applied in non-model organisms without reference genomes. Crustaceans are no exception. They are particularly diverse among the Arthropoda and contain a wide variety of commercially important fishery species such as shrimps, lobsters and crabs (Order Decapoda), and keystone species of aquatic ecosystems such as water fleas (Order Branchiopoda). In terms of decapod sex determination and differentiation, previous approaches have attempted to elucidate their molecular components, to establish mono-sex breeding technology. Here, we overview reports describing the physiological functions of sex hormones regulating masculinization and feminization, and gene discovery by transcriptomics in decapod species. Moreover, this review summarizes the recent progresses of studies on the juvenile hormone-driven sex determination system of the branchiopod genus Daphnia, and then compares sex determination and endocrine systems between decapods and branchiopods. This review provides not only substantial insights for aquaculture research, but also the opportunity to re-organize the current and future trends of this field.

Characterization and Expression Analysis of Insulin Growth Factor Binding Proteins (IGFBPs) in Pacific White Shrimp Litopenaeus vannamei

The insulin signaling (IIS) pathway plays an important role in the metabolism, growth, development, reproduction, and longevity of an organism. As a key member of the IIS pathway, insulin-like growth factor binding proteins (IGFBPs) are widely distributed a family in invertebrates and vertebrates that are critical in various aspects of physiology. As an important mariculture species, the growth of Pacific white shrimp, Litopenaeus vannamei, is one of the most concerning characteristics in this area of study. In this study, we identified three IGFBP genes in the genome of L. vannamei and analyzed their gene structures, phylogenetics, and expression profiles. LvIGFBP1 was found to contain three domains (the insulin growth factor binding (IB) domain, the Kazal-type serine proteinase inhibitor (Kazal) domain, and the immunoglobulin C-2 (IGc2) domain), while LvIGFBP2 and LvIGFBP3 only contained a single IB domain. LvIGFBP1 exhibited high expression in most tissues and different developmental stages, while LvIGFBP2 and LvIGFBP3 were only slightly expressed in hemocytes. The RNA interference of LvIGFBP1 resulted in a significantly smaller increment of body weight than that of control groups. These results will improve our understanding of the conservative structure and function of IGFBPs and show potential applications for the growth of shrimp.

The presence of an insulin-like peptide-binding protein (ILPBP) in the ovary and its involvement in the ovarian development of the red deep-sea crab, Chaceon quinquedens

Invertebrate insulin-like peptide-binding proteins (ILPBPs) are structurally homologous to vertebrate insulin-like growth factor binding protein 7 (IGFBP7). One of the invertebrate ILPBPs is considered as a potential binding protein of insulin-like androgenic gland factor (IAG) in males of crayfish, Cherax quadricarinatus. However, the ILPBP expression is not limited in the androgenic gland and found in most examined tissues, implicating that ILPBP may have additional functions in crustaceans. Here, the full-length cDNA sequence of ILPBP (termed ChqILPBP) is isolated from the ovary of the red deep-sea crab, Chaceon quinquedens. ChqILPBP transcripts are present in the various tissues, as similar to other crab species. The crustacean ILPBPs have their putative amino acid sequences conserved much less than vertebrate IGFBP7s. To understand if ChqILPBP is involved in ovarian development, examined are levels of ChqILPBP, together with vitellogenin (ChqVTG) in the same ovary and hepatopancreas of adult females at the different ovarian stages: 2, 3, and 5. Chaceon hepatopancreas exhibits as the primary VTG synthesis site, while VTG transcript levels do not differ by the ovarian stages. The ovary contains ChqILPBP transcripts ~10-fold higher than hepatopancreas that changes significantly from stage 2 to 3. Such an expression pattern mirrors that of ovarian ChqVTG. In hepatopancreas, ChqILPBP transcripts are similar at stages 2 and 3 and increase significantly at stage 5. The data indicate that ovarian ILPBP may function differently from that of the hepatopancreas and may play a role in ovarian development. ChqAK transcripts are ~six folds higher in the ovary than the hepatopancreas. While they do not differ by ovarian stages, suggesting that AK may not be involved in vitellogenesis of the cold water crustacean species.

Multi-Tissue Transcriptome Analysis Identifies Key Sexual Development-Related Genes of the Ornate Spiny Lobster (Panulirus ornatus)

Sexual development involves the successive and overlapping processes of sex determination, sexual differentiation, and ultimately sexual maturation, enabling animals to reproduce. This provides a mechanism for enriched genetic variation which enables populations to withstand ever-changing environments, selecting for adapted individuals and driving speciation. The molecular mechanisms of sexual development display a bewildering diversity, even in closely related taxa. Many sex determination mechanisms across animals include the key family of "doublesex- and male abnormal3-related transcription factors" (Dmrts). In a few exceptional species, a single Dmrt residing on a sex chromosome acts as the master sex regulator. In this study, we provide compelling evidence for this model of sex determination in the ornate spiny lobster Panulius ornatus, concurrent with recent reports in the eastern spiny lobster Sagmariasus verreauxi. Using a multi-tissue transcriptomic database established for P. ornatus, we screened for the key factors associated with sexual development (by homology search and using previous knowledge of these factors from related species), providing an in-depth understanding of sexual development in decapods. Further research has the potential to close significant gaps in our understanding of reproductive development in this ecologically and commercially significant order.

The "IAG-Switch"-A Key Controlling Element in Decapod Crustacean Sex Differentiation

The androgenic gland (AG)-a unique crustacean endocrine organ that secretes factors such as the insulin-like androgenic gland (IAG) hormone-is a key player in crustacean sex differentiation processes. IAG expression induces masculinization, while the absence of the AG or a deficiency in IAG expression results in feminization. Therefore, by virtue of its universal role as a master regulator of crustacean sexual development, the IAG hormone may be regarded as the sexual "IAG-switch." The switch functions within an endocrine axis governed by neuropeptides secreted from the eyestalks, and interacts downstream with specific insulin receptors at its target organs. In recent years, IAG hormones have been found-and sequenced-in dozens of decapod crustacean species, including crabs, prawns, crayfish and shrimps, bearing different types of reproductive strategies-from gonochorism, through hermaphroditism and intersexuality, to parthenogenesis. The IAG-switch has thus been the focus of efforts to manipulate sex developmental processes in crustaceans. Most sex manipulations were performed using AG ablation or knock-down of the IAG gene in males in order to sex reverse them into "neo-females," or using AG implantation/injecting AG extracts or cells into females to produce "neo-males." These manipulations have highlighted the striking crustacean sexual plasticity in different species and have permitted the manifestation of either maleness or femaleness without altering the genotype of the animals. Furthermore, these sex manipulations have not only facilitated fundamental studies of crustacean sexual mechanisms, but have also enabled the development of the first IAG-switch-based monosex population biotechnologies, primarily for aquaculture but also for pest control. Here, we review the crustacean IAG-switch, a unique crustacean endocrine mechanism, from the early discoveries of the AG and the IAG hormone to recent IAG-switch-based manipulations. Moreover, we discuss this unique early pancrustacean insulin-based sexual differentiation control mechanism in contrast to the extensively studied mechanisms in vertebrates, which are based on sex steroids.

Characterization of Insulin-Like Growth Factor Binding Protein 7 (Igfbp7) and Its Potential Involvement in Shell Formation and Metamorphosis of Pacific Abalone, Haliotis discus hannai

Insulin-like growth factor binding proteins (IGFBPs) are secreted proteins that play an important role in IGF regulation of growth and development of vertebrate and invertebrates. In this study, the IGFBP7 gene was cloned and characterized from mantle tissues of H. discus hannai, and designated as Hdh IGFBP7. The full-length cDNA sequence transcribed from the Hdh IGFBP7 gene was 1519-bp long with an open reading frame of 720-bp corresponding to a putative polypeptide of 239 amino acids. The molecular mass of its mature protein was approximately 23.44 KDa with an estimated isoelectric point (pI) of 5.35, and it shared significant homology with IGFBP7 gene of H. madaka. Hdh IGFBP7 has a characteristic IGFBP N-terminal domain (22–89 aa), a kazal-type serine proteinase inhibitor domain (77–128), and an immunoglobulin-like C2 domain (144–223). Furthermore, twelve cysteine residues and a signature motif of IGFBPs (XCGCCXXC) were found in its N-terminal domain. Phylogenetic analysis revealed that Hdh IGFBP7 was aligned with IGFBP7 of H. madaka. Tissue distribution analysis showed that the mRNA of Hdh IGFBP7 was expressed in all examined tissues, with the highest expression level observed in the mantle and gill tissues. The expression level of Hdh IGFBP7 mRNA was relatively higher at the juvenile stage during its metamorphosis period. In situ hybridization showed that Hdh IGFBP7 transcript was expressed in epithelial cells of the dorsal mantle pallial and mucus cells of the branchial epithelium in gill. These results provide basic information for future studies on the role of IGFBP7 in IGF regulation of shell growth, development and metamorphosis of abalone.

Characterization of Insulin-Like Growth Factor Binding Protein-5 (IGFBP-5) Gene and Its Potential Roles in Ontogenesis in the Pacific Abalone, Haliotis discus hannai

Insulin-like growth factor binding protein family is known to be involved in regulating biological actions of insulin-like growth factors (IGFs). In the present study, a full-length cDNA encoding the IGFBP-5 gene was cloned and characterized from the cerebral ganglion of Haliotis discus hannai. The 921-bp full-length sequence of Hdh IGFBP-5 cDNA transcript had an open reading frame of 411 bp encoding a predicted polypeptide of 136 amino acids, sharing high sequence identities with IGFBP-5 of H. diversicolor. The deduced Hdh IGFBP-5 protein contained a putative transmembrane domain (13-35 aa) in the N-terminal region. It also possessed a signature domain of IGFBP protein family (IB domain, 45-120 aa). Six cysteine residues (Cys-47, Cys-55, Cys-73, Cys-85, Cys-98, and Cys-118) in this cloned sequence could potentially form an intrachain disulfide bond. Phylogenetic analysis indicated that the Hdh IGFBP-5 gene was robustly clustered with IGFBP-5 of H. diversicolor. Tissue distribution analysis based on qPCR assay showed that Hdh IGFBP-5 was widely expressed in all examined tissues, with significantly (p < 0.05) higher expression in the cerebral ganglion. In male and female gametogenetic cycles, Hdh IGFBP-5 mRNA was expressed at all stages, showing significantly higher level at ripening stage. The expression level of Hdh IGFBP-5 mRNA was significantly higher in the polar body stage than in other ontogenic stages. In situ hybridization revealed that Hdh IGFBP-5 mRNA was present in the neurosecretory cells of the cerebral ganglion. This is the first study describing IGFBP-5 in H. discus hannai that might be synthesized in the neural ganglia. Our results demonstrate Hdh IGFBP-5 is involved in regulating ontogenic development and reproductive regulation of H. discus hannai.

Insights into carbohydrate metabolism from an insulin-like peptide in Macrobrachium rosenbergii

This study identified an insulin-like peptide (ILP) in Macrobrachium rosenbergii termed Mr-ILP and further investigated its function through glucose injection and RNAi. With the analysis of five other glucose metabolism related genes, this study shed light on the molecular mechanism of carbohydrate metabolism in crustaceans. Mr-ILP shared the typical skeleton with six conserved cysteine and mainly expressed in neuroendocrine system. In M. rosenbergii, the elevated hemolymph glucose concentration after glucose injection returned to basal levels in short time, implying an efficient regulatory system in carbohydrate metabolism. Hyperglycemic related genes answered the elevated hemolymph glucose concentration quickly with significant decreased expression level, while Mr-ILP showed delayed response. Instead, glycolysis increased after glucose injection, which indicated glycolysis might play an important role in lowering the abnormally high glucose level. In vivo silencing of Mr-ILP, by injecting the prawns with double-stranded RNA (dsRNA) for 21 days reduced its expression by approximately 75%. Accordingly, glycogen synthase decreased and the trehalose and glycogen level in the hepatopancreas were significantly reduced, indicating the function of Mr-ILP in oligosaccharide and polysaccharide accumulation. When Mr-ILP was silenced, the expression of hyperglycemic related genes were enhanced, but the hemolymph glucose level was not elevated significantly, which might attribute to the increased glycolysis to keep a balanced glucose level in hemolymph.

Insight into the Regulatory Relationships between the Insulin-Like Androgenic Gland Hormone Gene and the Insulin-Like Androgenic Gland Hormone-binding Protein Gene in Giant Freshwater Prawns (Macrobrachium rosenbergii)

Giant freshwater prawns (Macrobrachium rosenbergii) are commonly found throughout the world. The size of the male giant freshwater prawn is much larger than that of the female. Therefore, understanding the molecular mechanism that underlies the sexual differentiation of M. rosenbergii is of both commercial and scientific importance. Insulin-like androgenic gland hormone (IAG) plays a key role in the differentiation of sex in M. rosenbergii. Although IAG has been investigated, the regulatory relationship between IAG and its binding protein partner, the insulin-like androgenic gland hormone-binding protein (IAGBP), has not been studied in M. rosenbergii. Here, we cloned and characterized the IAGBP from M. rosenbergii (Mr-IAGBP) for the very first time. Transcriptomic analysis showed that Mr-IAGBP mRNA was detected in a wide array of tissues with the highest expression found in the androgenic gland. The importance of IAG in male development was further demonstrated by an increase in IAG transcripts during the development of the androgenic gland and Mr-IAG was only highly transcribed in the androgenic gland of M. rosenbergii. Interestingly, we found that the Mr-IAG gene expression started during the 20th-day larva after hatching stage (LH20), followed (20th-day post-larval stage, PL20) by a gradual elevation of Mr-IAGBP levels. The levels of both genes peaked at the adult stage. The relationship between Mr-IAGBP and Mr-IAG was further analyzed using RNA interference. The injection of Mr-IAGBP double-stranded RNA (dsRNA) significantly reduced the transcription of Mr-IAG, while the amount of Mr-IAGBP mRNA and the translation of IAGBP protein was significantly reduced by the injection of Mr-IAG dsRNA. These results revealed that IAGBP is involved in IAG signaling. Furthermore, our data supports the hypothesis that (IAG and IAGBP)-IAG receptor signaling schemes exist in M. rosenbergii. Our results will provide important information for the further study of determining the sex of M. rosenbergii.

Molecular Characterization of the Insulin-Like Androgenic Gland Hormone in the Swimming Crab, Portunus trituberculatus, and Its Involvement in the Insulin Signaling System

The insulin-like androgenic gland hormone (IAG) is mainly produced in the androgenic gland (AG) of the male crustaceans and is a crucial regulator in male sexual differentiation. In the current study, the full-length cDNA of IAG in the swimming crab, Portunus trituberculatus (Pt-IAG), was cloned and characterized. Similar to other reported IAGs, the deduced amino acid sequence of Pt-IAG consists of signal peptide, B chain, C peptide, and A chain, containing six conserved cysteines that form two interchain disulfide bonds and one intra-B chain disulfide bond. Tissue distribution analysis suggested that the Pt-IAG cDNA was highly expressed in the AG and was slightly expressed in several other tissues. A short-term silencing of PtIAG with double-stranded RNA was found to reduce the transcript levels of insulin receptor (Pt-IR) and insulin-like growth factor-binding protein (Pt-IGFBP), suggesting the Pt-IAG might perform its biological function through the insulin family-based signaling system. Bilateral eyestalk ablation (ESA) induced the expression of Pt-IAG in the AG at 4 and 7 days after surgery, while the transcript levels of Pt-IR in the AG and testis and Pt-IGFBP in the muscle, testis, and thoracalia ganglia were significantly decreased from 1 day after surgery. The results suggested that the Pt-IR and Pt-IGFBP might also be the targets of eyestalk neuropeptides and responded to the ESA independent of IAG regulation.

IGFBP-rP1, a strongly conserved member of the androgenic hormone signalling pathway in Isopoda

The first protein which has been described to interact with the malacostracan Androgenic Gland Hormone (AGH) is a binding protein called IGFBP-rP1. It has been identified and studied in several species of decapods, in which its interaction with the masculinizing hormone and its expression patterns have been established in several ways. However, this protein remains uncharacterised to date in the other malacostracan orders, like Amphipoda and Isopoda, although they were historically the first ones in which the androgenic gland and the corresponding hormone were respectively described. In this article, we identified the IGFBP-rP1 of isopods and established its implication in the pathway of the AGH with a silencing approach in the model species Armadillidium vulgare. We also showed that this gene is expressed in all the tissues of males and females, with a similar pattern in animals infected with Wolbachia, a feminizing endosymbiont of several isopod species. The expression pattern did not differ during the development of uninfected and infected animals either. We finally studied the evolution of the IGFBP-rP1 in 68 isopod species, looking for conserved motifs and evidence of natural selection. Altogether, our results showed that this gene is constitutively expressed and strongly conserved in isopods, in which it likely constitutes a key element of the insulin/IGF signalling pathway. However, we also illustrated that IGFBP-rP1 is not sufficient on its own to explain the different developmental paths taken by the males and the females or feminized genetic males.

Divergent evolution and clade-specific duplications of the Insulin-like Receptor in malacostracan crustaceans

The Insulin-like Receptors (IRs) are an important protein family, represented by three members in vertebrates, two of which are well-known for their implication in metabolism (Insulin Receptor) and growth (IGF Receptor). In contrast, little is known about these receptors in invertebrates, in which a single gene generally exists except for a part of insects and other occasional species-specific duplications. In this study, we used publicly available sequences as well as de novo assembled transcriptomes to investigate the IR evolution in malacostracan crustaceans, animals in which the Insulin/IGF pathway is known to be implicated in sexual development through the androgenic gland hormone. We described the evolutionary divergence of malacostracan IRs compared to all the other metazoan sequences, including other pancrustaceans. We also demonstrated two well conserved duplications of IRs: one specific to the whole malacostracan class, another one specific to the decapod order. The potential implications for malacostracan biology are discussed.

Molecular identification of an insulin growth factor binding protein (IGFBP) and its potential role in an insulin-like peptide system of the pearl oyster, Pinctada fucata

Insulin-like growth factors (IGFs) play critical roles in regulating metabolism, growth, and reproduction in invertebrates. IGF binding proteins (IGFBPs) serve as major regulators of IGF activity and regulate endocrine system. In the present study, the full-length cDNA of an igfbp was identified from the pearl oyster, Pinctada fucata, using expressed sequence tag (EST) sequence. The 1124bp Pfigfbp cDNA contains a 465bp open reading frame (ORF) encoding a putative protein of 154 amino acids, a 5'-untranslated region (UTR) of 238bp, and a 3'-UTR of 394bp (not including polyA+). Multiple sequence alignment of the deduced IB domain sequences revealed that twelve conserved Cys and ILP binding site in PfIGFBP were well aligned with human IGFBPs1-7, Mizuhopecten yessoensis IGFBP5 and Eriocheir sinensis IGFBP7. Gene expression analysis indicated that Pfigfbp mRNA was expressed in all the tissues and developmental stages examined, with a higher level in the foot than in other tissues and a higher level in the polar body stage and 32-cell stage than in the other stages. Pfigfbp and PfILP (insulin-like peptide) mRNA levels significantly increased in the digestive gland after feeding, while levels were dramatically reduced during a week of food deprivation and increased upon refeeding. In vitro experiments indicated that Pfigfbp mRNA expression in mantle cells was affected by insulin/IGFs (IGF-I, IGF-II). Our data suggests that Pfigfbp may be involved in endocrine signaling in P. fucata via the regulation of insulin-like peptide signaling.

Understanding Insulin Endocrinology in Decapod Crustacea: Molecular Modelling Characterization of an Insulin-Binding Protein and Insulin-Like Peptides in the Eastern Spiny Lobster, Sagmariasus verreauxi

The insulin signalling system is one of the most conserved endocrine systems of Animalia from mollusc to man. In decapod Crustacea, such as the Eastern spiny lobster, Sagmariasus verreauxi (Sv) and the red-claw crayfish, Cherax quadricarinatus (Cq), insulin endocrinology governs male sexual differentiation through the action of a male-specific, insulin-like androgenic gland peptide (IAG). To understand the bioactivity of IAG it is necessary to consider its bio-regulators such as the insulin-like growth factor binding protein (IGFBP). This work has employed various molecular modelling approaches to represent S. verreauxi IGFBP and IAG, along with additional Sv-ILP ligands, in order to characterise their binding interactions. Firstly, we present Sv- and Cq-ILP2: neuroendocrine factors that share closest homology with Drosophila ILP8 (Dilp8). We then describe the binding interaction of the N-terminal domain of Sv-IGFBP and each ILP through a synergy of computational analyses. In-depth interaction mapping and computational alanine scanning of IGFBP_N' highlight the conserved involvement of the hotspot residues Q₆₇, G₇₀, D₇₁, S₇₂, G₉₁, G₉₂, T₉₃ and D₉₄. The significance of the negatively charged residues D₇₁ and D₉₄ was then further exemplified by structural electrostatics. The functional importance of the negative surface charge of IGFBP is exemplified in the complementary electropositive charge on the reciprocal binding interface of all three ILP ligands. When examined, this electrostatic complementarity is the inverse of vertebrate homologues; such physicochemical divergences elucidate towards ligand-binding specificity between Phyla.

Isolation and Tissue Distribution of an Insulin-Like Androgenic Gland Hormone (IAG) of the Male Red Deep-Sea Crab, Chaceon quinquedens

The insulin-like androgenic gland hormone (IAG) found in decapod crustaceans is known to regulate sexual development in males. IAG is produced in the male-specific endocrine tissue, the androgenic gland (AG); however, IAG expression has been also observed in other tissues of decapod crustacean species including Callinectes sapidus and Scylla paramamosain. This study aimed to isolate the full-length cDNA sequence of IAG from the AG of male red deep-sea crabs, Chaceon quinquedens (ChqIAG), and to examine its tissue distribution. To this end, we employed polymerase chain reaction cloning with degenerate primers and 5′ and 3′ rapid amplification of cDNA ends (RACE). The full-length ChqIAG cDNA sequence (1555 nt) includes a 366 nt 5′ untranslated region a 453 nt open reading frame encoding 151 amino acids, and a relatively long 3′ UTR of 733 nt. The ORF consists of a 19 aa signal peptide, 32 aa B chain, 56 aa C chain, and 44 aa A chain. The putative ChqIAG amino acid sequence is most similar to those found in other crab species, including C. sapidus and S. paramamosain, which are clustered together phylogenetically.

The presence of an insulin-like androgenic gland factor (IAG) and insulin-like peptide binding protein (ILPBP) in the ovary of the blue crab, Callinectes sapidus and their roles in ovarian development

Insulin-like androgenic gland factor (IAG) that is produced by the male androgenic gland (AG), plays a role in sexual differentiation and maintenance of male secondary sex characteristics in decapod crustaceans. With an earlier finding of IAG expression in a female Callinectes sapidus ovary, we aimed to examine a putative role of IAG during the ovarian development of this species. To this end, the full-length cDNA sequence of the ovarian CasIAG (termed CasIAG-ova) has been isolated. The predicted mature peptide sequence of CasIAG-ova is identical to that of the IAG from the AG, except in their signal peptide regions. The CasIAG-ova contains an alternative initiation codon (UUG) as the start codon, which suggests that the translational regulation of CasIAG-ova may differ from that of the IAG from AG. To define the function of CasIAG-ova, the expressions of CasIAG-ova as well as its putative binding protein, insulin-like peptide binding protein (ILPBP), are measured in the ovaries at various developmental stages obtained from different seasons. Season affects both CasIAG and ILPBP expression in the ovary. Overall, summer females at earlier ovarian stages contain high levels of CasIAG and ILPBP than spring or fall females. These findings indicate that CasIAG-ova and CasILPBP may be involved in the ovarian development. When comparing the levels of CasIAG and CasILPBP in the ovary, the latter are much higher (∼10-10000 fold) than the former. Expression patterns of CasILPBP differ from those of CasIAG-ova during ovarian development and by season, suggesting that ILPBP may have an additional role in ovarian development rather than a function of a putative binding protein of IAG.

Does a blue crab putative insulin-like peptide binding protein (ILPBP) play a role in a virus infection?

Insulin-like peptides (ILPs) have regulatory roles in reproduction, development and metabolism in invertebrates. The mode of ILP actions has not been well studied in invertebrates in regard to the role of binding partners, i.e., ILP binding protein (ILPBP). In this study, the full-length cDNA of Callinectes sapidus ILPBP (Cas-ILPBP, 960 bp) has been isolated using RACE cloning, having short 5' and 3' UTRs of 30 and 162 bp, respectively. The predicted precursor of Cas-ILPBP (255 aa) contains, in order a signal peptide (23 aa), an insulin-like growth factor (IGF) binding (IB) domain (79 aa), a kazal-type serine protease inhibitor (KI) domain (36 aa) and an immunoglobulin (Ig) domain (101 aa). Phylogenetic analysis shows that Cas-ILPBP is grouped with the ILPBPs of other crustacean species, and it shares the closest relationship with the ILPBP from another crab species, Scylla paramamosain. Transcripts of Cas-ILPBP are found in all examined tissues, with the highest levels in the nervous tissues (eyestalk ganglia, brain and thoracic ganglia complex) and followed by midgut, the pericardial organ, abdominal muscle and the heart. As Cas-ILPBP contains a putative Ig domain, it is hypothesized that this protein may be involved in immunity, particularly in the adult females infected with a reo-like virus (CsRV1). The expression levels of Cas-ILPBP are examined in several tissues (hemocytes, midgut, eyestalk ganglia) from the animals carrying varying levels of CsRV1 at 17 and 23 °C water temperatures. Cas-ILPBP levels in the midgut are most significantly affected by high levels of CsRV1 infection. Reduction in Cas-ILPBP levels in the midguts is noted from the animals infected with high levels of CsRV1 that show reduced or stop feeding activity, indicating that it may play an important role in midgut functions such as digestion and nutrient absorption.

Applying the Power of Transcriptomics: Understanding Male Sexual Development in Decapod Crustacea

The decapod Crustacea are the most species-rich order of the Crustacea and include some of the most charismatic and highly valued commercial species. Thus the decapods draw a significant research interest in relation to aquaculture, as well as gaining a broader understanding of these species' biology. However, the diverse physiology of the group considered with the lack of a model species have presented an obstacle for comparative analyses. In reflection of this, the recent integration of comparative transcriptomics has rapidly advanced our understanding of key regulatory pathways and developmental phenomena, an example being our understanding of sexual development. We discuss our work in the Eastern spiny lobster, Sagmariasus verreauxi, in the context of what is currently known about male sexual development in the decapods, highlighting the importance of transcriptomic techniques in achieving our recent advancements. We describe the progression made in our understanding of male sexual differentiation and maturation, as mediated by the insulin-like androgenic gland hormone (IAG), integrating the role of regulatory binding proteins (IGFBPs), a tyrosine kinase insulin receptor (TKIR), as well as the upstream effect of neuroendocrine hormones (GIH and MIH). We then consider the less well understood mechanism of male sex determination, with an emphasis on what we believe to be the key regulatory factors, the Dsx- and mab-3-related transcription factors (Dmrts). Finally, we discuss the function of the antennal gland (AnG) in sexual development, relating to the emergence of male-biased upregulation in the AnG in later sexual maturation and the sexually dimorphic expression of two key genes Sv-TKIR and Sv-Dmrt1 We then present the AnG as a case study to illustrate how comparative transcriptomic techniques can be applied to guide preliminary analyses, like the hypothesis that the AnG may function in pheromone biosynthesis. In summary, we describe the power of transcriptomics in facilitating the progress made in our understanding of male sexual development, as illustrated by the commercial decapod species, S. verreauxi Considering future directions, we suggest that the integration of multiple omics-based techniques offers the most powerful tool to ensure we continue to piece together the biology of the important group of decapod Crustacea.

Identification of putative regulatory region of insulin-like androgenic gland hormone gene (IAG) in the prawn Macrobrachium nipponense and proteins that interact with IAG by using yeast two-hybrid system

Insulin-like androgenic gland hormone gene (IAG) is a sex regulator specifically expressed in male crustaceans, controlling the male sexual differentiation, spermatogenesis and reproductive strategy. Our previous study reported the cloning and characterization of the prawn Macrobrachium nipponense IAG (MnIAG). In this study, we further identified a 2214-bp MnIAG 5'-flanking region, and analyzed its transcription factor binding sites and transcriptional activity. The results showed that there were two potential promoter core sequences, three TATA boxes and one CAAT box existing in the MnIAG 5'-flanking region as well as many potential transcription factor binding sites, such as SRY, Sox-5, GATA-1, etc. Notably, the transcriptional activity was weak in this region, and a negative regulatory region was found in -604 to -231bp. In addition, we constructed M. nipponense yeast libraries and identified proteins interacting with the MnIAG protein by yeast two hybridization assay. The yeast two-hybrid screening yielded ten positive clones, of which five were annotated by NCBI database, namely heat shock protein 21, NADH dehydrogenase, zinc finger protein, beta-N-acetylglucosaminidase and a hypothetical protein. The identification of MnIAG putative regulatory region and proteins that interact with IAG will facilitate our understanding of the regulatory role of MnIAG and provide a foundation for deep insight into the prawn sex differentiation mechanism and signaling transduction pathways.

Male Sexual Development and the Androgenic Gland: Novel Insights through the de novo Assembled Transcriptome of the Eastern Spiny Lobster, Sagmariasus verreauxi

The Eastern spiny lobster, Sagmariasus verreauxi, is commercially important in fisheries, with growing aquaculture potential, driving an interest to better understand male sexual differentiation. Amongst the Decapoda, the androgenic gland (AG) and the insulin-like androgenic gland hormone (IAG) have a well-defined function in male sexual differentiation. However, IAG is not a sex determinant and therefore must be considered as part of a broader, integrated pathway. This work uses a transcriptomic, multi-tissue approach to provide an integrated description of male-biased expression as mediated through the AG. Transcriptomic analyses demonstrate that IAG expression is stage- and eyestalk-regulated (low in immature, high in mature and 6-times higher in hypertrophied glands), with IAG being the predominant AG-specific factor. The low expression of this key factor in immature males suggests the involvement of other tissues in male sexual differentiation. Across tissues, the gonad (87.8%) and antennal gland (73.5%) show the highest male-biased differential expression of transcripts and also express 4 sex-determination regulators, known as Dmrts, with broader expression of Sv-Sxl and Sv-TRA-2. In order to better understand male sexual differentiation, tissues other than the AG must also be considered. This research highlights the gonad and antennal gland as showing significant male-biased expression patterns, including the Sv-Dmrts.

Insulin/IGF signaling in Drosophila and other insects: factors that regulate production, release and post-release action of the insulin-like peptides

Insulin, insulin-like growth factors (IGFs) and insulin-like peptides (ILPs) are important regulators of metabolism, growth, reproduction and lifespan, and mechanisms of insulin/IGF signaling (IIS) have been well conserved over evolution. In insects, between one and 38 ILPs have been identified in each species. Relatively few insect species have been investigated in depth with respect to ILP functions, and therefore we focus mainly on the well-studied fruitfly Drosophila melanogaster. In Drosophila eight ILPs (DILP1-8), but only two receptors (dInR and Lgr3) are known. DILP2, 3 and 5 are produced by a set of neurosecretory cells (IPCs) in the brain and their biosynthesis and release are controlled by a number of mechanisms differing between larvae and adults. Adult IPCs display cell-autonomous sensing of circulating glucose, coupled to evolutionarily conserved mechanisms for DILP release. The glucose-mediated DILP secretion is modulated by neurotransmitters and neuropeptides, as well as by factors released from the intestine and adipocytes. Larval IPCs, however, are indirectly regulated by glucose-sensing endocrine cells producing adipokinetic hormone, or by circulating factors from the intestine and fat body. Furthermore, IIS is situated within a complex physiological regulatory network that also encompasses the lipophilic hormones, 20-hydroxyecdysone and juvenile hormone. After release from IPCs, the ILP action can be modulated by circulating proteins that act either as protective carriers (binding proteins), or competitive inhibitors. Some of these proteins appear to have additional functions that are independent of ILPs. Taken together, the signaling with multiple ILPs is under complex control, ensuring tightly regulated IIS in the organism.

Insights into insulin-like peptide system in invertebrates from studies on IGF binding domain-containing proteins in the female mud crab, Scylla paramamosain

Insulin-like peptides (ILPs) have been proved to exist extensively in invertebrates and play critical roles in regulating growth, metabolism and reproduction. ILP signaling system has been well defined in insects, with all key components homologous with vertebrate IGF signaling; however, counterparts of IGF binding proteins (IGFBPs) in vertebrates are not included in this system because of lacking sufficient researches in the related aspect. The present study firstly reports the identification of three kinds of invertebrate IGF binding (IB) domain-containing protein genes from the mud crab Scylla paramamosain. Gene expression analysis suggested that they might be closely involved in ovarian development, but with separate roles. Subsequent bioinformatics analysis and in vitro experiments indicated that they are likely to serve as endogenous ILP-specific binding proteins in invertebrates. More importantly, based on the current evidence we inferred that in invertebrate, ILP system might take the place of IGF system in vertebrate species.

Implication for the regulation of catabolism drawn from the single insulin-like growth factor binding domain protein (SIBD) gene in the mud crab, Scylla paramamosain

Insulin-like growth factor (IGF) signaling system holds a central position in regulating growth and metabolism in vertebrates. As critical components of this system, the IGF-binding proteins (IGFBPs) play important roles in regulating the biological activities of IGFs. Recently, the single IGF-binding domain protein (SIBD) was identified in invertebrates and its sequence was highly homologous with the N-terminal domain of IGFBP. In view of the possible role as counterparts of vertebrate IGFBPs, SIBDs have attracted the ever-increasing attention. This study reports the identification of a 1284bp SIBD gene (Sp-SIBD) from a member of commercially important family of Portunidae. The tissue distribution analysis showed that Sp-SIBD was mainly expressed in the nervous tissues and hepatopancreas. RNA in situ hybridization analysis showed that the positive signals were predominantly distributed in the secretory cells of the hepatopancreas. Subsequently, we examined the effects of various stresses, including hyperosmotic stress, hyperthermia, activated stress and fasting, on glucose levels in the hemolymph and Sp-SIBD expressions in the hepatopancreas. Interestingly, we found that Sp-SIBD expression was strongly up-regulated in response to these catabolic circumstances. Given the previous findings of insulin-like peptides (ILPs) in invertebrates, we speculate that invertebrate ILPs and SIBDs promise to serve as a pair of counterparts of IGFs and IGFBPs from vertebrate species respectively. In this context, the combined results suggested, by analogy with IGFBP 1 from vertebrates, for the first time that SIBD might play a key physiological role by sequestering ILPs to inhibit energy-expensive growth until conditions are more favorable.

Molecular characterization of insulin-like androgenic gland hormone-binding protein gene from the oriental river prawn Macrobrachium nipponense and investigation of its transcriptional relationship with the insulin-like androgenic gland hormone gene

Insulin-like androgenic gland hormone-binding protein (IAGBP) has been investigated in crustaceans in vitro. However, the relationship between IAGBP and its putative binding protein partner insulin-like androgenic gland hormone (IAG) has not been studied at the transcriptional level in vivo. In the current study, we cloned the full-length cDNA of IAGBP from the oriental river prawn Macrobrachium nipponense (Mn-IAGBP) and investigated the transcriptional patterns of Mn-IAGBP and the M. nipponense IAG gene (Mn-IAG) at different developmental stages and in different tissues. Mn-IAGBP mRNA was detected in all examined tissues from adult male prawns, with the highest transcriptional levels in the testis. Mn-IAG mRNA was detected in the androgenic gland and hepatopancreas. The genomic sequences of Mn-IAGBP and Mn-IAG were isolated by genome walking and two gene copies were found in both Mn-IAGBP and Mn-IAG. The relationship between Mn-IAGBP and Mn-IAG at the transcriptional level was studied by RNA interference. Injection of Mn-IAGBP double-stranded RNA (dsRNA) significantly reduced the transcription of Mn-IAG, while injection of Mn-IAG dsRNA significantly reduced the transcription of Mn-IAGBP in testis, muscle, androgenic gland, and hepatopancreas. These results demonstrate the involvement of the IAGBP gene in IAG signaling in M. nipponense.

Discovery of a novel insulin-like peptide and insulin binding proteins in the Eastern rock lobster Sagmariasus verreauxi

This study reports, for the first time in any of the commercially important decapod species, the identification of an insulin-like peptide (ILP), distinct from the androgenic gland hormone. Bioinformatics analysis of the de novo assembled spiny lobster, (Sagmariasus verreauxi) transcriptome, allowed identification of Sv-ILP1 as well as eight binding proteins. Binding proteins were termed as Sv-IGFBP, due to homology with the vertebrate insulin-like growth-factor binding protein and Sv-SIBD1-7, single insulin-binding domain protein (SIBD), similar to those identified in other invertebrate species. Sv-ILP1 was found to be expressed in the eyestalk, gonads and antennal gland of both sexes and to a lesser extent in male muscle, androgenic gland and hepatopancreas. The expression profiles of each binding protein were found to vary across tissues, with Sv-SIBD5, 6 and 7 showing higher expression in the gonad, demonstrated by PCR and digital gene expression. Further spatial investigations, using in-situ hybridisation, found Sv-ILP1 to be expressed in the neurosecretory cells of the thoracic ganglia, in keeping with the tissue expression of Drosophila ILP7 (DILP7). This correlative tissue expression, considered with the phylogenetic clustering of Sv-ILP1 and DILP7, suggests Sv-ILP1 to be a DILP7 orthologue. The broad expression of Sv-ILP1 strongly suggests that ILPs have a role beyond that of masculinisation in decapods. The function of these novel peptides may have application in enhancing aquaculture practices in the commercially important decapod species.

Apoptogenic metabolites in fractions of the Benthic diatom Cocconeis scutellum parva

Benthic diatoms of the genus Cocconeis contain a specific apoptogenic activity. It triggers a fast destruction of the androgenic gland in the early post-larval life of the marine shrimp Hippolyte inermis, leading to the generation of small females. Previous in vitro investigations demonstrated that crude extracts of these diatoms specifically activate a dose-dependent apoptotic process in human cancer cells (BT20 breast carcinoma) but not in human normal lymphocytes. Here, a bioassay-guided fractionation has been performed to detect the apoptogenic compound(s). Various HPLC separation systems were needed to isolate the active fractions, since the apoptogenic metabolite is highly active, present in low amounts and is masked by abundant but non-active cellular compounds. The activity is due to at least two compounds characterized by different polarities, a hydrophilic and a lipophilic fraction. We purified the lipophilic fraction, which led to the characterization of an active sub-fraction containing a highly lipophilic compound, whose molecular structure has not yet been identified, but is under investigation. The results point to the possible medical uses of the active compound. Once the molecular structure has been identified, the study and modulation of apoptotic processes in various types of cells will be possible.