Expression of an Androgenic Gland-Specific Insulin-Like Peptide during the Course of Prawn Sexual and Morphotypic Differentiation

The crustacean male-specific androgenic gland (AG) regulates sexual differentiation. In the prawn Macrobrachium rosenbergii, silencing an AG-specific insulin-like encoding transcript (Mr-IAG) inhibited the development of male sexual characters, suggesting that Mr-IAG is a key androgenic hormone. We used recombinant pro-Mr-IAG peptide to generate antibodies that recognized the peptide in AG cells and extracts, as verified by mass spectrometry. We revealed the temporal expression pattern of Mr-IAG and studied its relevance to the timetable of sex differentiation processes in juveniles and after puberty. Mr-IAG was expressed from as early as 20 days after metamorphosis, prior to the appearance of external male sexual characters. Mr-IAG expression was lower in the less reproductively active orange-clawed males than in both the dominant blue-clawed males and the actively sneak mating small males. These results suggest a role for Mr-IAG both in the timing of male sexual differentiation and in regulating reproductive strategies

Intracellular Ca2+ Regulates the Phosphorylation and the Dephosphorylation of Ciliary Proteins Via the NO Pathway

The phosphorylation profile of ciliary proteins under basal conditions and after stimulation by extracellular ATP was investigated in intact tissue and in isolated cilia from porcine airway epithelium using anti-phosphoserine and anti-phosphothreonine specific antibodies. In intact tissue, several polypeptides were serine phosphorylated in the absence of any treatment (control conditions). After stimulation by extracellular ATP, changes in the phosphorylation pattern were detected on seven ciliary polypeptides. Serine phosphorylation was enhanced for three polypeptides (27, 37, and 44 kD), while serine phosphorylation was reduced for four polypeptides (35, 69, 100, and 130 kD). Raising intracellular Ca2+ with ionomycin induced identical changes in the protein phosphorylation profile. Inhibition of the NO pathway by inhibiting either NO syntase (NOS), guanylyl cyclase (GC), or cGMP-dependent protein kinase (PKG) abolished the changes in phosphorylation induced by ATP. The presence of PKG within the axoneme was demonstrated using a specific antibody. In addition, in isolated permeabilized cilia, submicromolar concentrations of cGMP induced protein phosphorylation. Taken together, these results suggest that the axoneme is an integral part of the intracellular NO pathway. The surprising observation that ciliary activation is accompanied by sustained dephosphorylation of ciliary proteins via NO pathway was not detected in isolated cilia, suggesting that the protein phosphatases were either lost or deactivated during the isolation procedure. This work reveals that any pharmacological manipulation that abolished phosphorylation and dephosphorylation also abolished the enhancement of ciliary beating. Thus, part or all of the phosphorylated polypeptides are likely directly involved in axonemal regulation of ciliary beating

A Sexual Shift Induced by Silencing of a Single Insulin-Like Gene in Crayfish: Ovarian Upregulation and Testicular Degeneration

In sequential hermaphrodites, intersexuality occurs naturally, usually as a transition state during sexual re-differentiation processes. In crustaceans, male sexual differentiation is controlled by the male-specific androgenic gland (AG). An AG-specific insulin-like gene, previously identified in the red-claw crayfish Cherax quadricarinatus (designated Cq-IAG), was found in this study to be the prominent transcript in an AG cDNA subtractive library. In C. quadricarinatus, sexual plasticity is exhibited by intersex individuals in the form of an active male reproductive system and male secondary sex characters, along with a constantly arrested ovary. This intersexuality was exploited to follow changes caused by single gene silencing, accomplished via dsRNA injection. Cq-IAG silencing induced dramatic sex-related alterations, including male feature feminization, a reduction in sperm production, extensive testicular degeneration, expression of the vitellogenin gene, and accumulation of yolk proteins in the developing oocytes. Upon silencing of the gene, AG cells hypertrophied, possibly to compensate for low hormone levels, as reflected in the poor production of the insulin-like hormone (and revealed by immunohistochemistry). These results demonstrate both the functionality of Cq-IAG as an androgenic hormone-encoding gene and the dependence of male gonad viability on the Cq-IAG product. This study is the first to provide evidence that silencing an insulin-like gene in intersex C. quadricarinatus feminizes male-related phenotypes. These findings, moreover, contribute to the understanding of the regulation of sexual shifts, whether naturally occurring in sequential hermaphrodites or abnormally induced by endocrine disruptors found in the environment, and offer insight into an unusual gender-related link to the evolution of insulins

Hemocyanin Modification of Chitosan Scaffolds with Calcium Phosphate Phases Increase the Osteoblast/Osteoclast Activity Ratio—A Co-Culture Study

The ongoing research on biomaterials that support bone regeneration led to the quest for materials or material modifications that can actively influence the activity or balance of bone tissue cells. The bone biocompatibility of porous chitosan scaffolds was modified in the present study by the addition of calcium phosphates or hemocyanin. The first strategy comprised the incorporation of calcium phosphates into chitosan to create a biomimetic chitosan—mineral phase composite. The second strategy comprised dip-coating of chitosan scaffolds with hemocyanin extracted from crayfish hemolymph. The cytocompatibility was assessed in a mono-culture of human bone marrow stromal cells (hBMSCs) and their differentiation to osteoblasts; in a mono-culture of human monocytes (hMs) and their maturation to osteoclasts; and in a co-culture of hBMSC/osteoblasts—hM/osteoclasts. Mineral incorporation caused an increase in scaffold bioactivity, as shown by reduced calcium concentration in the cell culture medium, delayed differentiation of hBMSCs, and reduced osteoclastic maturation of hMs in mono-culture. Dip-coating with hemocyanin led to increased proliferation of hBMSCs and equivalent osteoclast maturation in mono-culture, while in co-culture, both an inhibitory effect of mineral incorporation on osteoblastogenesis and stimulatory effects of hemocyanin were observed. It was concluded that highly bioactive scaffolds (containing mineral phases) restrain osteoblast and osteoclast development, while hemocyanin coating significantly supports osteoblastogenesis. These influences on the osteoblasts/osteoclasts activity ratio may support scaffold-driven bone healing in the future

Crayfish hemocyanin on chitin bone substitute scaffolds promotes the proliferation and osteogenic differentiation of human mesenchymal stem cells

Crustacean chitin-hemocyanin-calcium mineral complexes were designed as bone biomimetics, with emphasis on their ability to bind or release calcium ions. Chitin scaffolds were prepared by dissolving chitin flakes in LiCl/dimethylacetamide, followed by gel formation and freeze-drying. Some of these scaffolds were modified by incorporation of CaCO3. In some of the chitin-CaCO3 scaffolds, macroporosity was introduced by HCl treatment. Hemocyanin from the crayfish Cherax quadricarinatus was used to further modify the chitin scaffolds by dip coating. Cytocompatibility, cellular adherence and proliferation of human mesenchymal stem cells (hMSCs) were evaluated in terms of cell number as reflected in lactate dehydrogenase activity. The chitin, chitin-CaCO3, and porous chitin-CaCO3 scaffolds were all found to facilitate cell attachment. Hemocyanin dip-coating of these scaffolds led to increased initial cell adhesion, enhanced proliferation, and osteogenic differentiation. Since the hemocyanin loading of the scaffolds was impaired by sterilization by gamma-irradiation (as required for biomedical applications), the hemocyanin loading was performed on previously sterilized scaffolds. All scaffolds facilitated osteogenic differentiation of osteoblasts, with the highest cell ALP-activity being found on hemocyanin-modified porous chitin-CaCO3 scaffolds. Thus, chitin-hemocyanin scaffolds enhanced the initial stages of bone cell development and could serve as promising biomaterials for bone regeneration

Temporal silencing of an androgenic gland-specific insulin-like gene affecting phenotypical gender differences and spermatogenesis

Androgenic glands (AGs) of the freshwater prawn Macrobrachium rosenbergii were subjected to endocrine manipulation, causing them to hypertrophy. Transcripts from these glands were used in the construction of an AG cDNA subtractive library. Screening of the library revealed an AG-specific gene, termed the M. rosenbergii insulin-like AG (Mr-IAG) gene. The cDNA of this gene was then cloned and fully sequenced. The cysteine backbone of the predicted mature Mr-IAG peptide (B and A chains) showed high similarity to that of other crustacean AG-specific insulin-like peptides. In vivo silencing of the gene, by injecting the prawns with Mr-IAG double-stranded RNA, temporarily prevented the regeneration of male secondary sexual characteristics, accompanied by a lag in molt and a reduction in growth parameters, which are typically higher in males of the species. In terms of reproductive parameters, silencing of Mr-IAG led to the arrest of testicular spermatogenesis and of spermatophore development in the terminal ampullae of the sperm duct, accompanied by hypertrophy and hyperplasia of the AGs. This study constitutes the first report of the silencing of a gene expressed specifically in the AG, which caused a transient adverse effect on male phenotypical gender differences and spermatogenesis. (Endocrinology 150: 1278 -1286, 2009) E ver since it was first proposed as the source of a hypothetical masculinizing hormone in crustaceans, the androgenic gland (AG) has been studied thoroughly in many crustacean species. The consensus emerging from these studies is that the AG plays a unifying role in the bewilderingly varied sex differentiation mechanisms in crustaceans (1-5). The AG constitutes a feature unique to male crustaceans in that it is an organ regulating sex differentiation separated from the gametogenic organ (unlike the single organ of vertebrate species). This separation enables manipulation of sex differentiation without affecting the gonads (6). In decapod male crustaceans, there are two AGs, each attached to the ejaculatory region of a vas deferens. In research spanning several decades, the functioning of the AG was investigated in a number of crustacean species by following the morphological and physiological effects of AG removal or transplantation on primary and secondary sex characteristics. In the amphipod Orchestia gamarella, for example, bilateral AG ablation decreased spermatogenesis and prevented the development of secondary male characteristics (7). In the crayfish Procambarus clarkii, injection of AG extracts accelerated the development of external male characteristics (8). In the giant freshwater prawn, Macrobrachium rosenbergii, a degree of masculinization was recorded in AG-implanted females (9). In the same species, fully functional sex reversal from males to neo-females (10) and from females to neo-males (11) was achieved by bilateral AG ablation and transplantation, respectively. The possibility of sex reversal has economical implications for the farming of this sexually dimorphic species because males grow faster than females (12). It is currently widely accepted that the AG of decapod crustaceans secretes the hormone(s) responsible for male differentiation, with a high probability of such a hormone(s) being proteinaceous in nature (13). This premise is supported by a histological study in the shore crab Phachygrapsus crassipes Multicellular organisms express various insulin-like peptides differentially. The insulin-like peptides discovered in inverte- Abbreviations: AG, Androgenic gland; CHH, crustacean hyperglycemic hormone; dsRNA, double-stranded RNA; GFP, green fluorescent protein; hAG, hypertrophy and hyperplasia of the androgenic gland; Mr-IAG, Macrobrachium rosenbergii insulin-like androgenic gland gene; RNAi, RNA interference; T7P, T7 promoter site at the 5Ј of one primer; UTR, untranslated region; XO-SG, X-organ sinus gland complex