Hemocyte Proliferation Research Articles

E3 Ubiquitin Ligase CHIP Inhibits Haemocyte Proliferation and Differentiation via the Ubiquitination of Runx in the Pacific Oyster.

Mollusca first evolve primitive immune cells (namely, haemocytes), which assemble a notable complex innate immune system, which are continuously produced through proliferation and differentiation and infused in the haemolymph. As a typical E3 ligase, CHIP is critical for immune cell turnover and homeostasis in vertebrates. In this study, a CHIP homolog (CgCHIP) with a high expression in haemocytes was identified in oysters to investigate its role in the proliferation and differentiation of ancient innate immune cells. CgCHIP exhibited a widespread distribution across all haemocyte subpopulations, and the knockdown of CgCHIP altered the composition of haemocytes as examined by flow cytometry. Mechanistically screened with bioinformatics and immunoprecipitation, a key haematopoietic transcription factor CgRunx was identified as a substrate of CgCHIP. Moreover, amino acids in the interacted intervals of CgCHIP and CgRunx were determined by molecular docking. Experimental evidence from an in vitro culture model of an agranulocyte subpopulation and an in vivo oyster model revealed that the knockdown of CgCHIP and CgRunx had opposing effects on agranulocyte (precursor cells) differentiation and granulocyte (effector cells) proliferation. In summary, CgCHIP negatively regulated agranulocyte differentiation and granulocyte proliferation by mediating the ubiquitination and degradation of CgRunx in oysters. These results offer insight into the involvement of ubiquitylation in controlling haemocyte turnover in primitive invertebrates.

Assessing the Effects of a Diet of BPA Analogue-Exposed Microalgae in the Clam Ruditapes philippinarum.

In our previous study, we demonstrated that the microalgae Phaeodactylum tricornutum can bioaccumulate bisphenol A analogues. Since this microalgae species is part of the diet of marine filter-feeding organisms, such as bivalves, in this study we tested the hypothesis that a diet based on exposed microalgae can exert negative effects on the clam Ruditapes philippinarum. Microalgae were exposed for 7 days to 300 ng/L of bisphenol AF (BPAF), bisphenol F (BPF), and bisphenol S (BPS), alone or as a mixture (MIX), to allow bioaccumulation. Microalgae were then supplied as food to bivalves. After 7 and 14 days of diet, the effects of exposed microalgae were evaluated on a battery of biomarkers measured in haemolymph/haemocytes, gills and digestive glands of clams. In addition, bioaccumulation of the three bisphenols was investigated in clams by UHPLC-HRMS. The results obtained demonstrated that total haemocyte count (THC) increased in clams following ingestion for 7 days of BPAF- and BPF-exposed microalgae, while BPS-exposed microalgae significantly reduced THC after 14 days of diet. MIX- and BPS-exposed microalgae increased haemocyte proliferation. The diet of exposed microalgae affected acid and alkaline phosphatase activity in clams, with an opposite response between haemolymph and haemocytes. Regarding antioxidants, an increase in catalase activity was observed in clams after ingestion of BPA analogue-exposed microalgae. The results also demonstrated marked oxidative stress in gills, the first tissue playing an important role in the feeding process. Oxidative damage was recorded in both the gills and digestive glands of clams fed BPA analogue-exposed microalgae. Alterations in epigenetic-involved enzyme activity were also found, demonstrating for the first time that BPA analogue-exposed food can alter epigenetic mechanisms in marine invertebrates. No bioaccumulation of BPA analogues was detected in clam soft tissues. Overall, this study demonstrated that a diet of BPA analogue-exposed microalgae can induce significant alterations of some important biological responses of R. philippinarum. To our knowledge, this is the first study demonstrating the effects of ingestion of BPA analogue-exposed microalgae in the clam R. philippinarum, suggesting a potential ecotoxicological risk for the marine food chain, at least at the first levels.

Protein phosphatase 2A regulates blood cell proliferation and differentiation in Drosophila larval lymph glands.

Protein phosphatase 2A (PP2A), one of the most abundant protein phosphatases, has divergent functions in multiple types of cells. Its inactivation has been closely associated with leukemia diseases. However, the physiological function of PP2A for hematopoiesis has been poorly understood in organisms. Drosophila hematopoiesis parallels the vertebrate counterpart in developmental and functional features but involves a much simpler hematopoietic system. Here, utilizing the Drosophila major larval hematopoietic organ lymph gland, we studied the function of PP2A for hematopoiesis in vivo. By knocking down the expression of Pp2A-29B that encodes the scaffold subunit of the PP2A holoenzyme complex, we found that PP2A silencing in the differentiating hemocytes resulted in their excessive proliferation. Furthermore, this PP2A inhibition downregulated the expression of Smoothened (Smo), a crucial component in the Hedgehog pathway, and smo overexpression was able to rescue the phenotypes of PP2A depletion, indicating that Smo functions as a downstream effector of PP2A to restrict the hemocyte proliferation. PDGF/VEGF-receptor (Pvr) overexpression also restored the Smo expression and lymph gland morphology of PP2A silencing, suggesting a PP2A-Pvr-Smo axis to regulate lymph gland growth and hemocyte proliferation. Moreover, inhibiting PP2A activity in the blood progenitor cells promoted their differentiation, but which was independent with Smo. Together, our data suggested that PP2A plays a dual role in the Drosophila lymph gland by preserving the progenitor population and restraining the hemocyte proliferation, to properly regulate the hematopoietic process.

Regulatory role of ETS1 transcription factor in hemocytes proliferation in Anadara granosa

The ETS1 transcription factor is crucial in the process of biological development. In vertebrate, ETS1 plays a pivotal role in promoting endothelial cell proliferation and angiogenesis. However, the identity and function of ETS1 remains unclear in mollusks. In this study, an ETS1 homolog (named as AgETS1) was identified in blood clam Anadara granosa (synonym: Tegillarca granosa). The full length of the AgETS1 transcription factor is 1569 bp, consisting of 539 amino acids, including the Sterile Alpha Motif (SAM) domain, which can recognize and bind to sequence of GGAA. Tissue expression analysis of A. granosa showed that AgETS1 exhibits the highest expression level in the gill tissues (51.5-fold of that in hemocyte, p < 0.05). AgETS1 mRNA transcripts were predominantly expressed during larval development, from zygote to trochophore stage. Moreover, the expression levels of AgETS1 in blood clams with high hemoglobin concentration (hemocyte count >1.75 × 108 cells/mL) were significantly higher than that in blood clams with low hemoglobin concentration (hemocyte count <8.5 × 107 cells/mL) (p < 0.05). RNA interfering (RNAi) of AgETS1 induced a corresponding decrease in the number of hemocytes in the hemolymph and a reduction in EdU-marked proliferating cells in the gill tissue. These results indicated that the ETS1 actively regulated the proliferation of hemocytes in A. granosa.

Phytic acid inhibits RafGOFScrib−/− tumor growth and invasion by suppressing the Yki-mediated JAK/STAT pathway in Drosophila melanogaster

Metastasis is one of the most important factors related to malignant tumor development and therapeutic failure. Phytic acid (PA), a poly-phosphorylated inositol derivative in plant seeds and grains, has been shown to have antitumoral activity. However, the effect of PA on tumor metastasis and the underlying mechanisms remain uncharacterized. In the current study, we aimed to identify the effect of PA on tumor metastasis by employing a Drosophila model of malignant tumor RafGOFScrib−/−. We observed that PA supplementation in food inhibited the invasion and migration of tumors. Further studies indicated that PA drives Yki phosphorylation and inactivation through Lats kinase, which subsequently results in decreased expression of the JAK/STAT pathway ligands unpaired cytokines (Upds). Moreover, the reduced JAK/STAT pathway inhibits the recruitment and proliferation of hemocytes. To summarize, these findings provide valuable pathological and mechanistic insights into the potential application of PA for functional food or natural medicine development.

The involvement of interferon regulatory factor 8 in regulating the proliferation of haemocytes in oyster Crassostrea gigas

Interferon regulatory factor 8 (IRF8) is an important transcriptional regulatory factor involving in multiple biological process, such as the antiviral immune response, immune cell proliferation and differentiation. In the present study, the involvement of a previously identified IRF8 homologue (CgIRF8) in regulating haemocyte proliferation of oyster were further investigated. CgIRF8 mRNA transcripts were detectable in all the stages of C. gigas larvae with the highest level in D-veliger (1.76-fold of that in zygote, p < 0.05). Its mRNA transcripts were also detected in all the three haemocyte subpopulations of adult oysters with the highest expression in granulocytes (2.79-fold of that in agranulocytes, p < 0.01). After LPS stimulation, the mRNA transcripts of CgIRF8 in haemocytes significantly increased at 12 h and 48 h, which were 2.04-fold and 1.65-fold (p < 0.05) of that in control group, respectively. Meanwhile, the abundance of CgIRF8 protein in the haemocytes increased significantly at 12 h after LPS stimulation (1.71-fold of that in seawater, p < 0.05). The immunofluorescence assay and Western blot showed that LPS stimulation induced an obvious nucleus translocation of CgIRF8 protein in haemocytes. After the expression of CgIRF8 was inhibited by the injection of CgIRF8 siRNA, the percentage of EdU positive haemocytes, the proportion of granulocytes, and the mRNA expression levels of CgGATA and CgSCL all declined significantly at 12 h after LPS stimulation, which was 0.64-fold (p < 0.05), 0.7-fold (p < 0.05), 0.31-fold and 0.54-fold (p < 0.001) of that in the NC group, respectively. While the expression level of cell proliferation-related protein CgCDK2, CgCDC6, CgCDC45 and CgPCNA were significantly increased (1.99-fold, and 2.41-fold, 3.76-fold and 4.79-fold compared to that in the NC group respectively, p < 0.001). Dual luciferase reporter assay demonstrated that CgIRF8 was able to activate the CgGATA promoter in HEK293T cells after transfection of CgGATA and CgIRF8. These results collectively indicated that CgIRF8 promoted haemocyte proliferation by regulating the expression of CgGATA and other related genes in the immune response of oyster.

TAL1-mediated regulation of hemocyte proliferation influences red blood phenotype in the blood clam Tegillarca granosa

Red blood phenotype, indicating the degree of red color in blood or hemolymph, is a significant economic trait in Tegillarca granosa, closely associated with its health condition and nutritive value. However, the molecular regulatory processes that account for the variation in the blood clams' red blood phenotype remain largely unexplored. In our previous studies, weighted gene co-expression network analysis (WGCNA) showed that TAL1 exhibits high intramodular connectivity in red blood-related module. Furthermore, TAL1 serves as a critical transcription factor in the survival and quiescence of hematopoietic stem cells, along with being essential in the terminal maturation processes in vertebrates. Consequently, we investigated the function of the TAL1 in blood clams by conducting a comparative analysis between high total hemocyte count (HTHC: THC ≥ 14 × 104 cells/μL) and low total hemocyte count (LTHC: THC ≤ 2.5 × 104 cells/μL) groups, as well as between negative control and Tg-TAL1 RNA interference groups of blood clams. The results revealed that, compared to LTHC group, there was a significant upregulation of TAL1 mRNA and protein expression levels in the HTHC group, which may be a crucial factor contributing to the alterations observed in THC. RNA interference of the TAL1 in blood clams resulted in a significant decline in THC, causing the blood color to become lighter. EdU staining experiments further confirmed a diminished cell proliferative vitality within T. granosa gills after TAL1 knockdown. Moreover, immunohistochemical analysis and immunofluorescence assays revealed a gradual escalation in TAL1 protein expression and cytoplasmic/nuclear ratio from gill filament chamber endothelial cells to gill filament chamber cells in gills, potentially representing different cell types in the maturation process of erythrocytes in blood clams. It suggesting that the gills might act as one of the hematopoietic tissues in blood clams, with hemocytes potentially originating from the gill filament chamber endothelium of the gills through division and differentiation. This research improves comprehension of the molecular mechanisms behind the variation in T. granosa's red blood phenotype, potentially assisting in the selective breeding of high THC T. granosa populations.

Tick hemocytes have a pleiotropic role in microbial infection and arthropod fitness

Uncovering the complexity of systems in non-model organisms is critical for understanding arthropod immunology. Prior efforts have mostly focused on Dipteran insects, which only account for a subset of existing arthropod species in nature. Here we use and develop advanced techniques to describe immune cells (hemocytes) from the clinically relevant tick Ixodes scapularis at a single-cell resolution. We observe molecular alterations in hemocytes upon feeding and infection with either the Lyme disease spirochete Borrelia burgdorferi or the rickettsial agent Anaplasma phagocytophilum. We reveal hemocyte clusters exhibiting defined signatures related to immunity, metabolism, and proliferation. Depletion of phagocytic hemocytes affects hemocytin and astakine levels, two I. scapularis hemocyte markers, impacting blood-feeding, molting behavior, and bacterial acquisition. Mechanistically, astakine alters hemocyte proliferation, whereas hemocytin affects the c-Jun N-terminal kinase (JNK) signaling pathway in I. scapularis. Altogether, we discover a role for tick hemocytes in immunophysiology and provide a valuable resource for comparative biology in arthropods.

Tick innate immune responses to hematophagy and Ehrlichia infection at single-cell resolution.

Ticks rely on robust cellular and humoral responses to control microbial infection. However, several aspects of the tick's innate immune system remain uncharacterized, most notably that of the immune cells (called hemocytes), which are known to play a significant role in cellular and humoral responses. Despite the importance of hemocytes in regulating microbial infection, our understanding of their basic biology and molecular mechanisms remains limited. Therefore, we believe that a more detailed understanding of the role of hemocytes in the interactions between ticks and tick-borne microbes is crucial to illuminating their function in vector competence and to help identify novel targets for developing new strategies to block tick-borne pathogen transmission. This study examined hemocytes from the lone star tick (Amblyomma americanum) at the transcriptomic level using the 10X genomics single-cell RNA sequencing platform to analyze hemocyte populations from unfed, partially blood-fed, and Ehrlichia chaffeensis-infected ticks. The functional role of differentially expressed hemocyte markers in hemocyte proliferation and Ehrlichia dissemination was determined using an RNA interference approach. Our data exhibit the identification of fourteen distinct hemocyte populations. Our results uncover seven distinct lineages present in uninfected and Ehrlichia-infected hemocyte clusters. The functional characterization of hemocytin, cystatin, fibronectin, and lipocalin demonstrate their role in hemocyte population changes, proliferation, and Ehrlichia dissemination. Our results uncover the tick immune responses to Ehrlichia infection and hematophagy at a single-cell resolution. This work opens a new field of tick innate immunobiology to understand the role of hemocytes, particularly in response to prolonged blood-feeding (hematophagy), and tick-microbial interactions.

MicroRNA-125 modulates hemocyte proliferation through regulating Astakine expression and participate the disease resistant in Scylla paramamosain

The innate immunity is widely regulated by microRNAs (miRNAs) and that miRNA-125 (miR-125) is involved in many diseases and host immune response. This research was aimed to explore how miR-125 regulates innate immunity in Scylla paramamosain when response to pathogen infection. AMO-miR-125 (anti-miRNA-125 oligonucleotide) was applied to specifically inhibit miR-125 in mud crabs. We found that miR-125 induced hemocyte proliferation, enhanced total hemocyte count in the crabs and protected crabs from challenged with white spot syndrome virus (WSSV) and Vibrio parahaemolyticus. Astakine regulates hemocyte proliferation, and the expression of Astakine increased after miR-125 knockdown, the results indicated that miR-125 may regulate hemocyte proliferation and total hemocyte count by regulating the expression of Astakine. Moreover, miR-125 knockdown also reduced phagocytosis and apoptosis, showing that miR-125 could affect the two processes in crab hemocytes. And the cumulative mortality of WSSV or V. parahaemolyticus infected crabs increased after AMO-miR-125 treatment, which indicated that miR-125 could reduce the death of crab caused by the pathogens and significantly affect the crab's immune response to pathogen. In summary, our data confirmed that miR-125 participates in hemocyte proliferation, the innate immunity, and the resistance to microbial disease in Scylla paramamosain.

CBFA2T3 affects red blood phenotype in the blood clam Tegillarca granosa by regulating hemocyte proliferation

The red blood phenotype of blood clam Tegillarca granosa, is tightly linked to its health conditions and nutritional benefits, making it an economically important trait. Despite its significance, the molecular regulatory mechanisms responsible for red blood phenotype variation in blood clams still poorly understood. Our previous study shows that hemocyte proliferation may affect hemoglobin concentration (HGC) and cause the red blood phenotype variation in T. granosa. Thus, we defined total hemocyte counts (THC) and HGC as red blood-related traits. In this research, we discovered that blood clams with higher THC exhibited elevated HGC and a darker blood color. To gain insights into the genes associated with THC in T. granosa, we conducted RNA-Seq analysis. Our transcriptome analysis identified 682 genes exclusively highly expressed in high THC clams (HTHC:THC ≥ 15.5 × 104 cells/mL), and 709 genes highly expressed in low THC clams (LTHC:THC ≤ 6.5 × 104 cells/mL). Furthermore, the weighted gene co-expression network analysis (WGCNA) revealed that the grey60 module exhibited significant positive correlations with THC and HGC, implying an association of this module with the red-blood phenotype. Subsequently, the red blood-related module exhibited a significant positive correlation with gill tissue, providing an alternative perspective to support the hypothesis that gills serve as the primary hematopoietic organ in T. granosa. By employing differential expression analysis and WGCNA, CBFA2T3, TAL1, and FLI1 are potentially key genes involved in the regulation of hemocyte proliferation and differentiation. RNA interference of CBFA2T3 gene led to a remarkable decrease in HGC and THC in T. granosa, resulting in a lighter blood color. EdU staining further confirmed the decrease of cell proliferation activity in the gills of T. granosa after knockdown of CBFA2T3. This study enhances our apprehending of the molecular mechanisms in red blood phenotype variation in T. granosa, and potential contributes to the selection breeding of high THC blood clams.

Genome-wide identification and characteristic analysis of ETS gene family in blood clam Tegillarca granosa

BackgroundETS transcription factors, known as the E26 transformation-specific factors, assume a critical role in the regulation of various vital biological processes in animals, including cell differentiation, the cell cycle, and cell apoptosis. However, their characterization in mollusks is currently lacking.ResultsThe current study focused on a comprehensive analysis of the ETS genes in blood clam Tegillarca granosa and other mollusk genomes. Our phylogenetic analysis revealed the absence of the SPI and ETV subfamilies in mollusks compared to humans. Additionally, several ETS genes in mollusks were found to lack the PNT domain, potentially resulting in a diminished ability of ETS proteins to bind target genes. Interestingly, the bivalve ETS1 genes exhibited significantly high expression levels during the multicellular proliferation stage and in gill tissues. Furthermore, qRT-PCR results showed that Tg-ETS-14 (ETS1) is upregulated in the high total hemocyte counts (THC) population of T. granosa, suggesting it plays a significant role in stimulating hemocyte proliferation.ConclusionOur study significantly contributes to the comprehension of the evolutionary aspects concerning the ETS gene family, while also providing valuable insights into its role in fostering hemocyte proliferation across mollusks.

Gcm counteracts Toll-induced inflammation and impacts hemocyte number through cholinergic signaling.

Hemocytes, the myeloid-like immune cells of Drosophila, fulfill a variety of functions that are not completely understood, ranging from phagocytosis to transduction of inflammatory signals. We here show that downregulating the hemocyte-specific Glial cell deficient/Glial cell missing (Glide/Gcm) transcription factor enhances the inflammatory response to the constitutive activation of the Toll pathway. This correlates with lower levels of glutathione S-transferase, suggesting an implication of Glide/Gcm in reactive oxygen species (ROS) signaling and calling for a widespread anti-inflammatory potential of Glide/Gcm. In addition, our data reveal the expression of acetylcholine receptors in hemocytes and that Toll activation affects their expressions, disclosing a novel aspect of the inflammatory response mediated by neurotransmitters. Finally, we provide evidence for acetylcholine receptor nicotinic acetylcholine receptor alpha 6 (nAchRalpha6) regulating hemocyte proliferation in a cell autonomous fashion and for non-cell autonomous cholinergic signaling regulating the number of hemocytes. Altogether, this study provides new insights on the molecular pathways involved in the inflammatory response.

Effects of the tumor necrosis factor on hemocyte proliferation and bacterial infection in Chinese mitten crab (Eriocheir sinensis)

Tumor necrosis factor (TNF) is an important cytokine that can regulate a variety of cellular responses by binding tumor necrosis factor receptor (TNFR). We studied whether the TNF of Eriocheir sinensis can regulate hemocyte proliferation. The results showed that the EsTNF and EsTNFR were constitutively expressed in all tested tissues, including the heart, hepatopancreas, muscles, gills, stomachs, intestines, and hemocytes. We found that low levels of EsTNF and EsTNFR transcripts were present in hemocytes. The gene expression levels were significantly increased in the hemocytes after being stimulated by Staphylococcus aureus or Vibrio parahaemolyticus. We also found some genes related to cell proliferation were expressed at a higher level in pulsing rTNF-stimulated hemocytes compared with the control group. We also knocked down the EsTNFR gene with RNAi technology. The results showed that the expression level of these genes related to cell proliferation was significantly down-regulated compared with the control group when the TNF does not bind TNFR. We used Edu technology to repeat the above experiments and the results were similar. Compared with the control group, the hemocytes stimulated by rTNF showed more significant proliferation, and the proliferation rate was significantly down-regulated after knocking down the EsTNFR gene. Therefore, we indicate that TNF binding TNFR can affect the proliferation of E. sinensis hemocytes, which might be manifested by affecting the expression of some proliferation-related genes.

The effect of reactive oxygen species (ROS) in immunity and WSSV infection of Scylla paramamosain

Reactive oxygen species (ROS) are typically regarded as being generated by the cellular respiratory chain or by cells under pathological damage, which play a crucial role as signaling molecules in promoting hemocytes circulation and normal cellular physiological functions. In this study, the antioxidant N-acetylcysteine (NAC) was used to reduce ROS in vivo and in vitro, which to analyze the effect of ROS on innate immunity and viral infection of mud crab. The total hemocyte count (THC), phenoloxidase (PO), superoxide dismutase (SOD) activity, immune-relative genes were analyzed, respectively. Moreover, the effect of ROS on WSSV infection was analyzed by THC and hemocytes apoptosis. The data showed that NAC could effectively remove and inhibit intracellular ROS. The THC of NAC group was reduced at 12 h and 24 h compared with that of control. And the inhibition of ROS by NAC could increase the SOD activity with control group, while increased the PO activity caused by early WSSV infection. And NAC could up-regulate the expression of MCM7, JAK, TLR and proPO significantly, while down-regulate the expression of Astakine, proPO, caspase and p53. Similarly, NAC could inhibit WSSV-induced apoptosis of S. paramamosain hemocytes. The data illustrated that ROS participates in the interaction between hemocytes and virus infection by regulating innate immunity. Especially, after NAC inhibited ROS, the expression of hemocytes proliferation gene Astakine was also inhibited, which may indicate that ROS is related to the process of hemocytes proliferation. The data will show a preliminary exploration on the regulatory role of ROS in crustacean immune system.

Potential molecular mechanism underlying the harmed haemopoiesis upon Benzo[a]pyrene exposure in Chlamys farreri

Benzo[a]pyrene (B[a]P), a ubiquitous contamination in the marine environments, has the potential to impact the immune response of bivalves by affecting the hemocyte parameters, especially total hemocyte count (THC). THC is mainly determined by haematopoietic mechanisms and apoptosis of hemocytes. Many studies have found that B[a]P can influence the proliferation and differentiation of hemocytes. However, the link between the toxic mechanisms of haematopoietic and environmental pollutants is not explicitly stated. This study is to investigate the toxic effects of B[a]P on haematopoietic mechanisms in C. farreri. Through the tissue expression distribution experiment and EDU assay, gill is identified as a potential haematopoietic tissue in C. farreri. Subsequently, the scallops were exposed to B[a]P (0.05, 0.5, 5 μg/L) for 1d, 3d, 6d, 10d and 15d. Then BPDE content, DNA damage, gene expression of haematopoietic factors and haematopoietic related pathways were determined in gill and hemocytes. The results showed that the expression of CDK2 was significantly decreased under B[a]P exposure through three pathways: RYR/IP3-calcium, BPDE-CHK1 and Notch pathway, resulting in cell cycle arrest. In addition, B[a]P also significantly reduced the number of proliferating hemocytes by affecting the Wnt pathway. Meanwhile, B[a]P can significantly increase the content of ROS, causing a downregulation of FOXO gene expression. The gene expression of Notch pathway and ERK pathway was also detected. The present study suggested that B[a]P disturbed differentiation by multiple pathways. Furthermore, the expression of SOX11 and CD9 were significantly decreased, which directly indicated that differentiation of hemocytes was disturbed. In addition, phagocytosis, phenoloxidase activity and THC were also significant decreased. In summary, the impairment of haematopoietic activity in C. farreri further causes immunotoxicity under B[a]P exposure. This study will improve our understanding of the immunotoxicity mechanism of bivalve under B[a]P exposure.

CgWnt-1 regulates haemocyte proliferation during immune response of oyster Crassostrea gigas

Recent findings regarding the immunomodulatory role of Wnt signaling suggest that it is significant in regulating the differentiation and proliferation of immune cells. In the present study, a Wnt-1 homolog (designated as CgWnt-1) with a conserved WNT1 domain was identified from oyster Crassostrea gigas. The transcripts of CgWnt-1 were barely expressed in egg to gastrula stage during early embryogenesis, and up-regulated significantly in the trochophore to juvenile stage. The mRNA transcripts of CgWnt-1 were detected in different tissues of adult oyster, with an extremely high expression level in the mantle, which was 77.38-fold (p < 0.05) of that in labial palp. After Vibrio splendidus stimulation, the mRNA expression levels of CgWnt-1 and Cgβ-catenin in haemocytes up-regulated significantly at 3, 12, 24, and 48 h (p < 0.05). After injection of recombinant protein (rCgWnt-1) into oyster in vivo, the expressions of Cgβ-catenin, cell proliferation related genes CgRunx-1 and CgCDK-2 in haemocytes significantly up-regulated, which were 4.86-fold (p < 0.05), 9.33-fold (p < 0.05), 6.09-fold (p < 0.05) of those in rTrx group, respectively. The percentage of EDU+ cells in haemocytes also significantly increased (2.88-fold of that in control group, p < 0.05) at 12 h after rCgWnt-1 treatment. When the Wnt signal inhibitor C59 was injected simultaneously with rCgWnt-1, the expressions of Cgβ-catenin, CgRunx-1, and CgCDK-2 were significantly reduced, which were 0.32-fold (p < 0.05), 0.16-fold (p < 0.05), and 0.25-fold (p < 0.05) of that in rCgWnt-1 group, respectively, and the percentage of EDU+ cells in haemocytes was also significantly inhibited (0.15-fold compared with that in rCgWnt-1 group, p < 0.05). These results suggested that the conserved CgWnt-1 could modulate haemocytes proliferation via regulating cell cycle related genes and involved in the immune response of oysters.

Hemocyte proliferation is associated with blood color shade variation in the blood clam, Tegillarca granosa

Blood color shade is closely related to the health status and nutritional value of the blood clam, Tegillarca granosa. The blood color shade of T. granosa shows great variation and is considered as an economically importantly trait. However, the molecular regulatory mechanism of blood color shade variation is unclear. In this study, the total hemocyte count (THC) and hemoglobin concentration (HGC) were verified to be related to blood color shade. RNA-seq analysis was performed to explore the blood color shade-related genes in T. granosa. Transcriptome analysis revealed 399 and 467 genes that were exclusively highly expressed in light-blood clams (HGC > 45.7 g/L, designated TL) and dark-blood clams (HGC < 31.3 g/L, designated TH), respectively. Differentially expressed genes were enriched in cell cycle, and several key genes (such as CDC42 and CDC20) involved in hematopoietic processes were upregulated in the TH group, which means that the variation of blood color shade is probably related to hematopoietic cell proliferation. Knockdown of CDC42 gene expression resulted in a significant reduction in THC in blood clams, and EdU staining revealed that cell proliferation activity of the clam gills is higher in the TH group than in the TL group, which confirmed our assumption. The present study improves our understanding of the molecular mechanisms underlying blood color shade variation in marine clams and facilitates the selection of blood clams with higher hemoglobin contents.

Gbb Regulates Blood Cell Proliferation and Differentiation through JNK and EGFR Signaling Pathways in the Drosophila Lymph Gland.

The Drosophila lymph gland is an ideal model for studying hematopoiesis, and unraveling the mechanisms of Drosophila hematopoiesis can improve our understanding of the pathogenesis of human hematopoietic malignancies. Bone morphogenetic protein (BMP) signaling is involved in a variety of biological processes and is highly conserved between Drosophila and mammals. Decapentaplegic (Dpp)/BMP signaling is known to limit posterior signaling center (PSC) cell proliferation by repressing the protooncogene dmyc. However, the role of two other TGF-β family ligands, Glass bottom boat (Gbb) and Screw (Scw), in Drosophila hematopoiesis is currently largely unknown. Here, we showed that the loss of Gbb in the cortical zone (CZ) induced lamellocyte differentiation by overactivation of the EGFR and JNK pathways and caused excessive differentiation of plasmatocytes, mainly by the hyperactivation of EGFR. Furthermore, we found that Gbb was also required for preventing the hyperproliferation of the lymph glands by inhibiting the overactivation of the Epidermal Growth Factor Receptor (EGFR) and c-Jun N-terminal Kinase (JNK) pathways. These results further advance our understanding of the roles of Gbb protein and the BMP signaling in Drosophila hematopoiesis and the regulatory relationship between the BMP, EGFR, and JNK pathways in the proliferation and differentiation of lymph gland hemocytes.

Histone lysine-specific demethylase 1 regulates the proliferation of hemocytes in the oyster Crassostrea gigas.

Lysine-specific demethylase 1 (LSD1) is an essential epigenetic regulator of hematopoietic differentiation, which can specifically mono-methylate H3K4 (H3K4me1) and di-methylate H3K4 (H3K4me2) as a transcriptional corepressor. Previous reports have been suggested that it participated in hematopoiesis and embryonic development process. Here, a conserved LSD1 (CgLSD1) with a SWIRM domain and an amino oxidase (AO) domain was identified from the Pacific oyster Crassostrea gigas. We conducted a comprehensive analysis by various means to verify the function of CgLSD1 in hematopoietic process, including quantitative real-time PCR (qRT-PCR) analysis, western blot analysis, immunofluorescence assay, RNA interference (RNAi) and flow cytometry. The qRT-PCR analysis revealed that the transcripts of CgLSD1 were widely expressed in oyster tissues with the highest level in the mantle. And the transcripts of CgLSD1 were ubiquitously expressed during larval development with the highest expression level at the early D-veliger larvae stage. In hemocytes after Vibrio splendidus stimulation, the transcripts of CgLSD1 were significantly downregulated at 3, 6, 24, and 48 h with the lowest level at 3 h compared to that in the Seawater group (SW group). Immunocytochemical analysis showed that CgLSD1 was mainly distributed in the nucleus of hemocytes. After the CgLSD1 was knocked down by RNAi, the H3K4me1 and H3K4me2 methylation level significantly increased in hemocyte protein. Besides, the percentage of hemocytes with EdU-positive signals in the total circulating hemocytes significantly increased after V. splendidus stimulation. After RNAi of CgLSD1, the expression of potential granulocyte markers CgSOX11 and CgAATase as well as oyster cytokine-like factor CgAstakine were increased significantly in mRNA level, while the transcripts of potential agranulocyte marker CgCD9 was decreased significantly after V. splendidus stimulation. The above results demonstrated that CgLSD1 was a conserved member of lysine demethylate enzymes that regulate hemocyte proliferation during the hematopoietic process.