Glutamine synthetase gene expression during the regeneration of the annelid Enchytraeus japonensis

Identification of astrocyte-like cells in an adult ascidian during regeneration of the central nervous system

The mechanisms underlying regeneration of the central nervous system (CNS) following lesions have been studied extensively in both vertebrate and invertebrate models. To shed light on regeneration, ascidians, a sister group of vertebrates and with remarkable ability to regenerate their brains, constitute an appropriate model system. Glial cells have been implicated in regeneration in vertebrates; however, their role in the adult ascidian CNS regeneration is unknown. A model of degeneration and regeneration using the neurotoxin 3-acetylpyridine (3AP) in the brain of the ascidian Styela plicata was used to identify astrocyte-like cells and investigate their role. We studied the CNS of control ascidians (injected with artificial sea water) and of ascidians whose CNS was regenerating (1 and 10 days after the injection with 3AP). Our results show that the mRNA of the ortholog of glutamine synthetase (GS), a glial-cell marker in vertebrates, is increased during the early stages of regeneration. Confirming the identity of GS, the protein was identified via immunostaining in a cell population during the same regeneration stage. Last, a single ortholog of GS (GSII) is present in ascidian and amphioxus genomes, while two types exist in fungi, some invertebrates, and vertebrates, suggesting that ascidians have lost the GSI type. Taken together, our findings revealed that a cell population expressing glial-cell markers may play a role in regeneration in adult ascidians. This is the first report of astrocyte-like cells in the adult ascidian CNS, and contributes to understanding of the evolution of glial cells among metazoans.

Integrated transcriptomic and metabolomic analyses reveal mechanism underlying higher resistance of the marine oligochaete Thalassodrilides cf. briani (Clitellata: Naididae) to heavy contamination of sediments with polycyclic aromatic hydrocarbons

In some coastal areas, sediments are contaminated with various chemical compounds, causing significant threats to marine organisms. Therefore, the development of remediation techniques is important. Here, we focused on bioremediation using marine benthic animals such as aquatic oligochaetes. The oligochaete Thalassodrilides cf. briani is highly resistant to contamination of sediments with toxic chemicals. We examined whether T. cf. briani could decompose high-concentration polycyclic aromatic hydrocarbons (PAHs) in sediments. Furthermore, relevant genes expressed in T. cf. briani exposed to contaminated sediment were comprehensively examined using next-generation sequencing, and its metabolites were identified by metabolomic analysis using gas chromatography-mass spectrometry. T. cf. briani reduced the concentration of 16 PAHs in the sediment from 55,900 to 45,200 ng/g dry weight in 50 days, thereby reducing total PAH concentrations by approximately 20%. The results of transcriptomic analysis suggest that activation of a drug-metabolizing enzyme system may promote the metabolism of harmful chemical substances during excretion of chemicals from the body. According to the results of principal component analysis based on the values of 43 types of metabolomes identified by metabolomic analysis, groups were divided according to the difference in the number of exposure days. In addition, levels of glutamine, which is important for maintaining digestive tract functions, increased. This suggests that the digestive tract function promotes the metabolism and detoxification of foreign substances. Furthermore, transcriptome analysis revealed that glutamate dehydrogenase increased 1.3-fold and glutamine synthetase increased 1.7-fold, confirming the increase in glutamine. Thus, we conclude that T. cf. briani adapted to the polluted sediment by regulating its metabolism.

Comparative Aspects of Annelid Regeneration: Towards Understanding the Mechanisms of Regeneration

The question of why animals vary in their ability to regenerate remains one of the most intriguing questions in biology. Annelids are a large and diverse phylum, many members of which are capable of extensive regeneration such as regrowth of a complete head or tail and whole-body regeneration, even from few segments. On the other hand, some representatives of both of the two major annelid clades show very limited tissue regeneration and are completely incapable of segmental regeneration. Here we review experimental and descriptive data on annelid regeneration, obtained at different levels of organization, from data on organs and tissues to intracellular and transcriptomic data. Understanding the variety of the cellular and molecular basis of regeneration in annelids can help one to address important questions about the role of stem/dedifferentiated cells and "molecular morphallaxis" in annelid regeneration as well as the evolution of regeneration in general.

Injury-Induced Innate Immune Response During Segment Regeneration of the Earthworm, Eisenia andrei

Regeneration of body parts and their interaction with the immune response is a poorly understood aspect of earthworm biology. Consequently, we aimed to study the mechanisms of innate immunity during regeneration in Eisenia andrei earthworms. In the course of anterior and posterior regeneration, we documented the kinetical aspects of segment restoration by histochemistry. Cell proliferation peaked at two weeks and remitted by four weeks in regenerating earthworms. Apoptotic cells were present throughout the cell renewal period. Distinct immune cell (e.g., coelomocyte) subsets were accumulated in the newly-formed blastema in the close proximity of the apoptotic area. Regenerating earthworms have decreased pattern recognition receptors (PRRs) (e.g., TLR, except for scavenger receptor) and antimicrobial peptides (AMPs) (e.g., lysenin) mRNA patterns compared to intact earthworms. In contrast, at the protein level, mirroring regulation of lysenins became evident. Experimental coelomocyte depletion caused significantly impaired cell divisions and blastema formation during anterior and posterior regeneration. These obtained novel data allow us to gain insight into the intricate interactions of regeneration and invertebrate innate immunity.

Comparative transcriptomics in Syllidae (Annelida) indicates that posterior regeneration and regular growth are comparable, while anterior regeneration is a distinct process

Background

Annelids exhibit remarkable postembryonic developmental abilities. Most annelids grow during their whole life by adding segments through the action of a segment addition zone (SAZ) located in front of the pygidium. In addition, they show an outstanding ability to regenerate their bodies. Experimental evidence and field observations show that many annelids are able to regenerate their posterior bodies, while anterior regeneration is often limited or absent. Syllidae, for instance, usually show high abilities of posterior regeneration, although anterior regeneration varies across species. Some syllids are able to partially restore the anterior end, while others regenerate all lost anterior body after bisection. Here, we used comparative transcriptomics to detect changes in the gene expression profiles during anterior regeneration, posterior regeneration and regular growth of two syllid species: Sphaerosyllis hystrix and Syllis gracilis; which exhibit limited and complete anterior regeneration, respectively.

Results

We detected a high number of genes with differential expression: 4771 genes in S. hystrix (limited anterior regeneration) and 1997 genes in S. gracilis (complete anterior regeneration). For both species, the comparative transcriptomic analysis showed that gene expression during posterior regeneration and regular growth was very similar, whereas anterior regeneration was characterized by up-regulation of several genes. Among the up-regulated genes, we identified putative homologs of regeneration-related genes associated to cellular proliferation, nervous system development, establishment of body axis, and stem-cellness; such as rup and JNK (in S. hystrix); and glutamine synthetase, elav, slit, Hox genes, β-catenin and PL10 (in S. gracilis).

Conclusions

Posterior regeneration and regular growth show no significant differences in gene expression in the herein investigated syllids. However, anterior regeneration is associated with a clear change in terms of gene expression in both species. Our comparative transcriptomic analysis was able to detect differential expression of some regeneration-related genes, suggesting that syllids share some features of the regenerative mechanisms already known for other annelids and invertebrates.

Possible roles of glutamine synthetase in responding to environmental changes in a scleractinian coral

Glutamine synthetase is an enzyme that plays an essential role in the metabolism of nitrogen by catalyzing the condensation of glutamate and ammonia to form glutamine. In this study, the activity and responses of glutamine synthetase towards environmental changes were investigated in the scleractinian coral Pocillopora damicornis. The identified glutamine synthetase (PdGS) was comprised of 362 amino acids and predicted to contain one Gln-synt_N and one Gln-synt_C domain. Expression of PdGS mRNA increased significantly after 12 h (1.28-fold, p < 0.05) of exposure to elevated ammonium, while glutamine synthetase activity increased significantly from 12 to 24 h, peaking at 12 h (54.80 U mg^-1, p < 0.05). The recombinant protein of the mature PdGS (rPdGS) was expressed in E. coli BL21, and its activities were detected under different temperature, pH and glufosinate levels. The highest levels of rPdGS activity were observed at 25 °C and pH 8 respectively, but decreased significantly at lower temperature, and higher or lower pH. Furthermore, the level of rPdGS activities was negatively correlated with the concentration of glufosinate, specifically decreasing at 10^-5 mol L^-1 glufosinate to be less than 50% (p < 0.05) of that in the blank. These results collectively suggest that PdGS, as a homologue of glutamine synthetase, was involved in the nitrogen assimilation in the scleractinian coral. Further, its physiological functions could be suppressed by high temperature, ocean acidification and residual glufosinate, which might further regulate the coral-zooxanthella symbiosis via the nitrogen metabolism in the scleractinian coral P. damicornis.

Developmental and molecular biology of annelid regeneration: a comparative review of recent studies

Studies of annelid regeneration have greatly increased in frequency in recent years, providing new insights into the developmental basis and evolution of regeneration. In this review, we summarize recent findings related to regeneration in annelids, focusing on molecular and developmental studies of epimorphic (blastema-based) regeneration, morphallactic (tissue-remodeling based) regeneration, and development and regeneration of putative stem cells of the posterior growth zone and germline. Regeneration is being investigated in a broad range of annelids spanning the phylum, and comparing findings among species reveals both widely conserved features that may be ancestral for the phylum as well as features that are variable across the group.

Molecular cloning and characterization of glutamine synthetase, a tegumental protein from Schistosoma japonicum

Glutamine synthetase catalyzes the synthesis of glutamine, providing nitrogen for the production of purines, pyrimidines, amino acids, and other compounds required in many pivotal cellular events. Herein, a full-length cDNA encoding Schistosoma japonicum glutamine synthetase (SjGS) was isolated from 21-day schistosomes. The entire open reading frame of SjGS contains a 1,095-bp coding region corresponding to 364 amino acids with a calculated molecular weight of 40.7 kDa. NCBIP blast shows that the putative amino acid of SjGS contains a classic β-grasp domain and a catalytic domain of glutamine synthetase. The relative mRNA expression of SjGS was evaluated in 7-, 13-, 21-, 28-, 35-, and 42-day worms of S. japonicum in the final host and higher expression at day 21, and 42 worms were observed. This protein was also detected in worm extracts using Western blot. Immunofluorescence studies indicated that the SjGS protein was mainly distributed on tegument and parenchyma in 28-day adult worms. The recombinant glutamine synthetase with a molecular weight of 45 kDa was expressed in Escherichia coli and purified in its active form. The enzyme activity of the recombinant protein was 3.30 ± 0.67 U.μg-1. The enzyme activity was highly stable over a wide range of pH (6-9) and temperature (25-40 °C) under physiological conditions. The transcription of SjGS was upregulated in praziquantel-treated worms at 2-, 4-, and 24-h posttreatment compared with the untreated control. As a first step towards the clarification of the role of glutamine synthetase in schistosome species, we have cloned and characterized cDNAs encoding SjGS in S. japonicum, and the data presented suggest that SjGS is an important molecule in the development of the schistosome.

What role do annelid neoblasts play? A comparison of the regeneration patterns in a neoblast-bearing and a neoblast-lacking enchytraeid oligochaete

The term ‘neoblast’ was originally coined for a particular type of cell that had been observed during annelid regeneration, but is now used to describe the pluripotent/totipotent stem cells that are indispensable for planarian regeneration. Despite having the same name, however, planarian and annelid neoblasts are morphologically and functionally distinct, and many annelid species that lack neoblasts can nonetheless substantially regenerate. To further elucidate the functions of the annelid neoblasts, a comparison was made between the regeneration patterns of two enchytraeid oligochaetes, Enchytraeus japonensis and Enchytraeus buchholzi, which possess and lack neoblasts, respectively. In E. japonensis, which can reproduce asexually by fragmentation and subsequent regeneration, neoblasts are present in all segments except for the eight anterior-most segments including the seven head-specific segments, and all body fragments containing neoblasts can regenerate a complete head and a complete tail, irrespective of the region of the body from which they were originally derived. In E. japonensis, therefore, no antero-posterior gradient of regeneration ability exists in the trunk region. However, when amputation was carried out within the head region, where neoblasts are absent, the number of regenerated segments was found to be dependent on the level of amputation along the body axis. In E. buchholzi, which reproduces only sexually and lacks neoblasts in all segments, complete heads were never regenerated and incomplete (hypomeric) heads could be regenerated only from the anterior region of the body. Such an antero-posterior gradient of regeneration ability was observed for both the anterior and posterior regeneration in the whole body of E. buchholzi. These results indicate that the presence of neoblasts correlates with the absence of an antero-posterior gradient of regeneration ability along the body axis, and suggest that the annelid neoblasts are more essential for efficient asexual reproduction than for the regeneration of missing body parts.

Isolation of genes involved in pancreas regeneration by subtractive hybridization

The deterioration of β cells in the pancreas is a crucial factor in the progression of diabetes mellitus; therefore, the recovery of β cells is of vital importance for effective diabetic therapeutic strategies. Partially pancreatectomized rats have been used for the investigation of pancreatic regeneration. Because it was determined that tissue extract from the partially-dissected pancreas induces pancreatic differentiation in embryonic stem cells, paracrine factors were thought to be involved in the regeneration. In this study, we screened for genes that had higher mRNA levels 2 days after 60%-pancreatectomy. The genes were isolated using subtractive hybridization and DNA sequencing. Twelve genes (adipsin, Aplp2, Clu, Col1a2, Glul, Krt8, Lgmn, LOC299907, LOC502894, Pla2g1b, Reg3α and Xbp1) were identified, and RT-PCR and real-time PCR analyses were performed to validate their expression levels. Among the genes identified, three genes (Glul, Lgmn and Reg3a) were selected for further analyses. Assays revealed that Glul and Reg3α enhance cell growth. Glul, Lgmn and Reg3α change the expression level of islet marker genes, where NEUROD, NKX2.2, PAX4 and PAX6 are up-regulated and somatostatin is down-regulated. Thus, we believe that Glul, Lgmn and Reg3a can serve as novel targets in diabetes mellitus genetic therapy.

Expression level of glutamine synthetase is increased in hepatocellular carcinoma and liver tissue with cirrhosis and chronic hepatitis B

Studies have suggested that glutamine synthetase (GS) is a potential marker of hepatocellular carcinoma (HCC). We aimed to evaluate the expression of GS in non-malignant liver tissue and serum GS levels in HCC, liver cirrhosis (LC), chronic hepatitis B (CHB), five kinds of extrahepatic diseases patients and healthy subjects. Immunohistochemistry (IHC) was used to assess GS expression in 260 liver tissue samples (from 120 HCC, 90 CHB stage 4, and 50 CHB stage 1-3 patients). Enzyme-linked immunosorbent assays of 325 samples (from 100 healthy donors, 33 CHB stage 1-3, 43 CHB stage 4, 111 HCC, and 45 extrahepatic diseases patients) were used to further analyze GS levels in serum. IHC studies showed the expression of GS in 70% of HCC patients, 46.7% of CHB stage 4 patients and 38% of CHB stage 1-3 patients. The χ(2) tests showed significant difference between HCC samples and non-tumor tissues (P = 0.001 for HCC vs. CHB stage 4, P = 0.000 for HCC vs. CHB). Consistent with this, serum GS levels are increased in HCC and CHB stage 1-4 patients. There are significant differences among all samples (P = 0.000 for all), except CHB stage 1-3 versus CHB stage 4 (P = 0.552). Based on multiple linear regressions, HCC, CHB stage 1-4 and AFP were significantly associated with serum GS levels. In addition, in HCC group, TNM and Child-Pugh were significantly associated with GS levels. Expression of GS is increased in HCC, LC, and CHB. It may be a new serum marker for liver disease.

The evolutionary origins of glia

The evolutionary origins of glia are lost in time, as soft tissues rarely leave behind fossil footprints, and any molecular footprints they might have been left we have yet to decipher. Nevertheless, because of the growing realization of the importance glia plays in the development and functioning of the nervous system, lessons we can draw about commonalities among different taxa (including vertebrates) brought about either from a common origin, or from common adaptational pressures, shed light on the roles glia play in all nervous systems. The Acoelomorpha, primitive interstitial flatworms with very simple cellular organization and currently at the base of the bilaterian phylogeny, possess glia-like cells. If they indeed represent the ancestors of all other Bilateria, then it is possible that all glias derive from a common ancestor. However, basal taxa lacking convincing glia are found in most major phyletic lines: urochordates, hemichordates, bryozoans, rotifers, and basal platyhelminths. With deep phylogenies currently in flux, it is equally possible that glia in several lines had different origins. If developmental patterns are any indication, glia evolved from ectodermal cells, possibly from a mobile lineage, and even possibly independently in different regions of the body. As to what functions might have brought about the evolution of glia, by-product removal, structural support, phagocytic needs, developmental programming, and circuit modulation may be the more likely. Explaining possible cases of glial loss is more difficult, as once evolved, glia appears to keep inventing new functions, giving it continued value even after the original generative need becomes obsolete. Among all the uncertainties regarding the origin of glia, one thing is certain: that our ideas about those origins will change with every rearrangement in deep phylogeny and with continued advances in invertebrate molecular and developmental areas.