[Regulation of Metabolism and the Role of Redox Factors in the Energy Control of Quiescence and Proliferation of Hematopoietic Cells]

One of the key regulators of hematopoietic stem cell (HSC) maintenance is cellular metabolism. Resting HSCs use anaerobic glycolysis as the main source of energy. During expansion and differentiation under conditions of steady state hematopoiesis, the energy needs of activated HSCs increase by many fold. To meet the increased demands, cells switch to mitochondrial oxidative phosphorylation, which is accompanied by an increase in reactive oxygen species (ROS) production. Here, the molecular mechanisms maintaining glycolysis in HSCs, as well as the factors determining the increase in metabolic activity and the transition to mitochondrial biogenesis during HSC activation are discussed. We focus on the role of HIF (hypoxia-inducible factor) proteins as key mediators of the cellular response to hypoxia, and also consider the phenomenon of extraphysiological oxygen shock (EPHOSS), leading to the forced differentiation of HSCs as well as methods of overcoming it. Finally, the role of fatty acid oxidation (FAO) in hematopoiesis is discussed. Understanding the metabolic needs of normal HSCs and precursors is crucial for the development of new treatments for diseases related to the hematopoietic and immune systems.

[Mitomycin C Treatment of Stromal Layers Enhances the Support of In Vitro Hematopoiesis in Co-Culture Systems]

A study was made of the effect that mitomycin C (MitC) treatment of stromal layers of NIH 3T3 cells expressing Jagged1, a ligand of the Notch receptor, exerts on the growth of hematopoietic Lin(-) mouse bone marrow cells in a co-culture system. MitC treatment of stromal cells significantly increased the number of hematopoietic cells and the frequency of colony-forming cells in stromal co-cultures. Transcriptome analysis of control and MitC-treated stromal cell samples was performed by differential RNA sequencing, and genes downregulated by MitC treatment were predominantly associated with the control of cell proliferation, the cell cycle, chromosome segregation, and DNA metabolism. Induction of key hematopoietic cytokines by MitC was not detected by the transcriptome analysis and was therefore not a main factor in the activation of hematopoiesis on the treated stroma. At the same time, the set of the genes most strongly upregulated by MitC treatment is enriched in the genes for cytokines, growth factors, and cell surface proteins, which presumably contribute to enhanced hematopoiesis support on the MitC-treated stroma. Products of some of these genes have been implicated in expansion of hematopoietic stem/progenitor cells in vitro or in vivo.

[Maintenance of Plasmid Expression in vivo Depends Primarily on the CpG Contents of the Vector and Transgene]

Plasmid-mediated gene therapy, being a safe and relatively inexpensive therapeutic strategy, is plagued by a fast silencing of transgene expression. The silencing severely reduces the long-term efficiency of plasmid vectors. We have earlier constructed a low-CpG pMBR2 plasmid vector supporting prolonged expression of transgenes in mesenchymal stem cells in vitro. Long-term expression from the pMBR2 vector was studied for the wild-type mouse secreted alkaline phosphatase gene (mSEAPTwt) and its version devoid of CpGs (mSEAP0) after vector electroporation into mouse hindlimb muscles and hydrodynamic delivery to the liver. The mSEAP levels in the blood were measured over one year. With the pMBR2-mSEAP0 construct, the mSEAP levels in leg muscles increased more than 2.5-fold in the first two months and remained higher than the initial level until the end of the experiment. Far lower expression levels were observed with the control pCDNA3.1-mSEAP0 construct. Expression from pMBR2-mSEAPwt decreased to about 40% after 6 months and remained at similar levels thereafter. In the mouse liver, expression from pMBR2-mSEAP0 was approximately halved within the first 18 weeks and then decrease slowly to the final 17% level. Expression from pMBR2-mSEAPwt initially dropped to 18% and remained at approximately 10% thereafter. In contrast, expression from pCDNA3.1-mSEAP0 sharply dropped to 5% after 2 weeks and remained at nearly zero levels throughout the rest of the experiment. Thus, both vector and transgene should have significantly reduced CpG contents to ensure prolonged plasmid-mediated expression in the liver, while minimizing the vector CpG content is sufficient for expression in skeletal muscles. The results suggested additionally that the localization of S/MAR elements within the transcription unit, in contrast to their outside location, results in significant reduction of the level of secreted, but not cytoplasmic, proteins.

[Factors Affecting the Labeling of NIH 3T3 Cells with Magnetic Nanoparticles]

The factors that affect the labeling of NIH 3T3 murine fibroblasts with Fe3O4-based magnetic nanoparticles (MNPs) were studied using MNPs produced by the gas condensation and solution precipitation methods and MNPs surface-modified with 3-aminopropylsilane or L-lysine. The production method, surface modifications, the particle concentration and size, the state of the cell population, and the method of MNP introduction were found to substantially affect the efficiency of MNP binding by cells. In particular, large MNP clusters may occur in MNP suspensions in DMSO, and their disruption by sonication increased the percent yield of magnetically labeled cells. Static incubation of a cell suspension led to a more efficient labeling as compared with continuous agitation. Cells attached to a plastic support could be labeled to a higher degree than cells in suspension, but required substantially longer incubations with MNPs. MNP centrifugation on cell layers (magnetic spinoculation) significantly increased the rate and efficiency of labeling. The stability of magnetic labeling was shown to depend on the MNP dose during labeling. Electron microscopy studies demonstrated that MNPs were associated with the cell surface after 20-min incubation with cells and were mostly in the cell interior after 4-h incubation. The results of the study may be useful for preparation and application of magnetized cell samples.

[Niches of Hematopoietic Stem Cells in Bone Marrow]

Hematopoietic stem cells (HSCs) exist in a close contact with their specific microenvironment, called a niche, which supports the HSC function and significantly influences the HSC properties. The existence of the HSC niche, which was proposed as a purely theoretical concept in 1978, finds increasing experimental evidence and is now generally accepted by specialists in the field of hematopoiesis. The review briefly describes various cell components of the HSC niche in bone marrow, considers the metabolic states of the niche and HSCs, and discusses other aspects of niche biology. Increasing knowledge of the HSC niche will help to create in vitro cell models of the HSC niche, to modulate the HSC properties, and to achieve multifold HSC expansion in culture for further applications in therapeutic practice.

[Hydrogen Sulfide Donor NaHS Protects Mesenchymal Stem and Melanoma Cells from the Negative Effects of Infrared Laser Irradiation]

We have established earlier that 835-nm infrared laser irradiation results in a dose-dependent growth inhibition of human mesenchymal stem and melanoma cells and is able to induce cell death. In this work we have demonstrated that hydrogen sulfide donor NaHS is able to protect both cell types from the negative action of laser irradiation and the magnitude of protection depends on NaHS concentration. The mechanism of cell protection by NaHS is primarily attributable to its effects on intracellular processes occurring after irradiation, since the protective effect does not depend on whether NaHS is added before or after irradiation. Moreover, NaHS is able to exert its protective effect even when added 6 hours post irradiation.

[Cytotoxic Effect of Low-Intensity Infrared Laser Irradiation on Human Melanoma Cells]

Continuous low-intensity laser irradiation (LILI) affects the state of cells in culture, including their proliferation rate. Data collected with various cell models vary significantly, but most studies have reported positive effects of LILI on cell proliferation. The effects of continuous infrared LILI (835 nm) was studied using three independent different melanoma cell lines. The LILI effect was shown to strongly depend on the irradiation dose. Higher doses (230 kJ/m^(2)) significantly suppressed the cell growth. A further increase in LILI dose led to a significant cytotoxic effect, which increased disproportionately quickly with the increasing light intensity. Human mesenchymal stem cells (MSCs) were found to be significantly more resistant to the cytotoxic effect of higher-dose LILI. Importantly, the effects were not due to the difference in culture conditions. Control experiments showed that 15 non-melanoma tumor cell lines were more resistant to LILI than melanoma cells. Selective sensitivity of melanoma cells to LILI in vitro was assumed to provide a basis for LILI-based approaches to melanoma treatment.

[Modulation of Luciferase Production in Melanoma Cells in vitro]

Reporter proteins find increasing application in biomedical studies in vitro and in vivo. However, to correctly interpret the results based on their use, it is important to understand whether reporter protein production is modulated in model cells and in what conditions such modulation may occur. Reporter activity was studied in Mel IL melanoma cells transiently transfected with a pCpG vector-based plasmid construct expressing firefly luciferase. Luciferase expression quickly dropped during the first two culture passages, which were followed by a quasi-stable period, when luciferase expression relatively slightly decreased with time. Phases of maximal and minimal luciferase production, which corresponded to the exponential and stationary growth phases, respectively, were observed during batch culture. When the medium was changed, luciferase production was stimulated in the stationary, but not exponential, cell growth phase. Severe hypoxia (0.1% O2) decreased the luciferase amount, suggesting substantial modulation of cell metabolism in total and luciferase production in particular. The targeted drug vemurafenib suppressed the luciferase production in Mel IL cells, whereas DMSO, which is often used as a drug solvent in experiments with cells, stimulated the luciferase production. Based on the results, it was hypothesized that modulation of reporter protein production in mammalian cells reflects the adaptation of intracellular metabolism to external conditions and may be a source of incorrect interpretations of experiments using reporter proteins.

[Murine and human hematopoietic progenitor cultures grown on stromal layers expressing Notch ligands]

The ex vivo maintenance and expansion of hematopoietic stem cells and early progenitors is necessary for the successful treatment of hematopoietic and immune diseases. Multiple attempts to improve the expansion of hematopoietic stem cells (HSCs) by their cultivation in the presence of growth factor cocktails have so far failed. Novel approaches aimed at conserving the earliest precursors in their undifferentiated state are needed. These approaches should take into account local regulatory factors that are present in the HSC microenvironment and the three-dimensional architecture of their niche. In the present study, we compared the effects of two Notch ligands, i.e., Jagged1 and DLL1, on murine and human hematopoiesis in vitro. Our observations indicate that the stromal expression of Notch ligands increases the production of both the total and phenotypically early murine and human hematopoietic cells in the co-culture. On one hand, this study demonstrates the similarity of effects of stromal expression of Notch ligands on murine and human hematopoiesis in vitro. On the other hand, our study revealed a number of cell type and ligand-specific variations that are systematically described below. It seems that the effects of SCF cytokine addition on murine hematopoiesis in vitro depend on the stromal context and are oppositely directed for Jagged1 and DLL1.

Controlled formaldehyde fixation of fibronectin layers for expansion of mesenchymal stem cells

Extracellular cell matrices deposited by cells stimulate cell proliferation. However, their generation is cumbersome and time consuming. We show here that controlled fixation of fibronectin layers after coating culture vessels significantly enhances expansion of murine and human mesenchymal stem cells (MSCs) and, to a lesser extent, primary fibroblasts. In contrast, fibronection fixation did not stimulate proliferation of established cancer cell lines. Fixed vitronectin or collagen IV layers also enhanced proliferation of murine MSCs. Thus, controlled formaldehyde fixation of layers formed by fibronectin or some other extracellular matrix components represents a simple and reproducible way to enhance proliferation of primary cells.

Analysis of Proliferation of Melanoma Cells and Mesenchymal Stem Cells in Co-Culture and Contribution of Experimental Conditions into Interpretation of the Results

A series of experiments on co-culturing of Mel IL melanoma cells and mesenhymal stem cells showed that these cells do not influence proliferation of each other, but we observed weaker adhesion of stromal stem cells to plastic in cocultures where with melanoma cells were grown on mesenhymal stem cells feeder. Cell proliferation was also considerably influenced by experimental conditions, which should be taken into account for correct interpretation of obtained results. The principles of experiments on co-culturing of cancer and stromal cells are formulated that take into account the most important factors influencing cell behavior and minimize the probability of artifact results. It was concluded that co-culturing conditions cells significantly affect the experimental results and can be the source of conflicting conclusions on mutual influence of stromal and cancer cells in vitro.

Recombinant HSP70 and mild heat shock stimulate growth of aged mesenchymal stem cells

Heat shock proteins including the major stress protein HSP70 support intracellular homeostasis and prevent protein damage after a temperature increase and other stressful environmental stimuli, as well as during aging. We have shown earlier that prolonged administration of recombinant human HSP70 to mice exhibiting Alzheimer's-like neurodegeneration as well as during sepsis reduces the clinical manifestations of these pathologies. Herein, we studied the action of recombinant human HSP70 on young and aged mouse mesenchymal stem cells (MSCs) in culture. The results obtained indicate that HSP70 at concentrations of 2 μg/ml and higher significantly stimulates growth of aged but not young MSCs. A similar effect is produced by application of a mild heat shock (42 °C 5 min) to the cells. Importantly, responses of young and aged MSCs to heat shock treatment of various durations differed drastically, and aged MSCs were significantly more sensitive to higher heat stress exposures than the young cells. Western blotting and protein labeling experiments demonstrated that neither mild heat shock nor exogenous HSP70 administration resulted in significant endogenous HSP70 induction in young and aged MSCs, whereas mild heat shock increased HSC70 levels in aged MSCs. The results of this study suggest that the administration of exogenous HSP70 and the application of mild heat stress may produce a certain "rejuvenating" effect on MSCs and possibly other cell types in vivo, and these interventions may potentially be used for life extension by delaying various manifestations of aging at the molecular and cellular level.

[Key regulators of skeletal myogenesis]

Skeletal myogenesis has been extensively studied at both morphological and molecular levels. This review considers the main stages of embryonic skeletal myogenesis and myogenic factors that trigger their initiation, focusing on specific protein interactions involved in somitic myogenesis, head myogenesis, and limb myogenesis. The second part of the review describes the role of noncoding RNAs (microRNAs and long noncoding RNAs) in myogenesis. This information is of particular interest, because regulation of cell processes by noncoding RNAs is an actively developing field of molecular biology. Knowledge of mechanisms of skeletal myogenesis is of applied significance. Various transcription factors, noncoding RNAs, and other myogenic regulators can be employed in the induction of myogenic reprogramming in stem cells and differentiated somatic cells. Current trends and strategies in the field of skeletal myogenic reprogramming are discussed in the last part of the review.

[Mesenchymal stem cells expressing cytosine deaminase inhibit growth of murine melanoma B16F10 in vivo]

The aim of this study was to estimate the efficacy of mesenchymal stem cell-based suicide gene therapy in mice bearing murine melanoma B16F10. Adipose mesenchymal stem cells (MSCs) were transfected with plasmid constructs expressing cytosine deaminase fused with uracil phosphoribosyltransferase (CDA/UPRT) or CDA/UPRT fused with HSV-1 tegument protein VP22 (CDA/UPRT/VP22). In this study, we demonstrate that direct intratumoral transplantation of MSCs expressing CDA/UPRT or CDA/UPRT/VP22 followed by systemic administration of 5-fluorocytosine (5-FC) results in a significant inhibition of tumor growth. There was a 53% reduction in tumor volume in mice treated with CDA/UPRT-MSCs and 58% reduction in tumor volume in mice treated with CDA/UPRT/VP22-MSCs as compared with control animals transplanted with B16F10 melanoma alone. Injection of CDA/UPRT-MSC and CDA/UPRT/VP22-MSC prolonged the life span of mice bearing B16F10 melanoma by 15 and 26%, respectively. The data indicate that in murine B16F10 melanoma model, MSCs encoding CDA/UPRT suicide gene have a significant antitumor effect.

[Homogeneous and heterogeneous 3D melanoma models in vitro]

Growth of malignant tumors occurs in three-dimensional space and depends on a presence of stromal component, which performs critical functions of tumor cell protection and growth support. Therefore, development and analysis of tumor models in 3D cell cultures in vitro, including co-culture systems, presents a significant interest. In this study, the results of 3D culturing of two human melanoma cell lines using the hanging drop method, with or without human mesenchymal stem cells (MSCs), are presented. Melanoma lines were shown to behave differently in 3D cultures; in particular, Mel Cher melanoma cells have the ability to form uniform spheroids within 24 h, whereas MeWo cells under similar conditions failed to form spheroids even after 2 days of culture. However, co-culturing of melanoma cells with MSCs resulted in formation of compact 3D cell spheroids in both cases. Visualization of MeWo cells and MSCs in the mixed spheroids using fluorescent dyes revealed certain clustering of melanoma cells. The observed properties of melanoma cells in homogeneous and heterogeneous spheroids may be used in the complex analysis of results of testing of antimelanoma chemotherapy drugs and evaluation of their therapeutic properties.

Intracellular Localization of the HCS2 Gene Products in Identified Snail Neurons In Vivo and In Vitro

1. The HCS2 (Helix command specific 2) gene expressed in giant command neurons for withdrawal behavior of the terrestrial snail Helix lucorum encodes a unique hybrid precursor protein that contains a Ca-binding (EF-hand motif) protein and four small peptides (CNP1-CNP4) with similar Tyr-Pro-Arg-X aminoacid sequence at the C terminus. Previous studies suggest that under conditions of increased intracellular Ca(2+) concentration the HCS2 peptide precursor may be cleaved, and small physiologically active peptides transported to the release sites. In the present paper, intracellular localization of putative peptide products of the HCS2-encoded precursor was studied immunocytochemically by means of light and electron microscopy. 2. Polyclonal antibodies against the CNP3 neuropeptide and a Ca-binding domain of the precursor protein were used for gold labeling of ultrathin sections of identified isolated neurons maintained in culture for several days, and in same identified neurons freshly isolated from the central nervous system. 3. In freshly isolated neurons, the gold particles were mainly localized over the cytoplasmic secretory granules, with the density of labeling for the CNP3 neuropeptide being two-fold higher than for the calcium-binding domain. In cultured neurons, both antibodies mostly labeled clusters of secretory granules in growth cones and neurites of the neuron. The density of labeling for cultured neurons was the same for both antibodies, and was two-fold higher than for the freshly isolated from the central nervous system neurons. 4. The immunogold particles were practically absent in the bodies of cultured neurons. 5. The data obtained conform to the suggestion that the HCS2 gene products are transported from the cell body to the regions of growth or release sites.

Helix peptide immunoreactivity pattern in the nervous system of juvenile aplysia

Distribution of neurons immunopositive to antibody against the small peptides encoded by the Helix Command-Specific 2 (HCS2) gene in the central nervous system of juvenile Aplysia californica was investigated. The HCS2 gene is specifically expressed in the withdrawal behavior neurons of the terrestrial snail Helix lucorum. In Aplysia, 20-25 immunopositive neuronal somata were observed on dorsal surface of each pleural ganglion (including a giant pleural neuron). The HCS2-encoded peptide immunopositive fibers were observed in neuropiles of all ganglia and in many nerves. Functional significance of Aplysia immunopositive cells is discussed.

Overexpression of camello, a member of a novel protein family, reduces blastomere adhesion and inhibits gastrulation in Xenopus laevis

Vertebrate gastrulation involves complex coordinated movements of cells and cell layers to establish the axial structures and the general body plan. Adhesion molecules and the components of extracellular matrix were shown to be involved in this process. However, other participating molecules and detailed mechanisms of the control of gastrulation movements remain largely unknown. Here, we describe a novel Xenopus gene camello (Xcml) which is expressed in the suprablastoporal zone of gastrulating embryos. Injection of Xcml RNA into dorsovegetal blastomeres retards or inhibits gastrulation movements. Database searches revealed a family of mammalian mRNAs encoding polypeptides highly similar to Xcml protein. Characteristic features of the camello family include the presence of the central hydrophobic domain and the N-acetyltransferase consensus motifs in the C-terminal part, as well as functional similarity to Xcml revealed by overexpression studies in Xenopus embryos. Xcml expression results in the decrease of cell adhesion as demonstrated by the microscopic analysis and the blastomere aggregation assay. Cell fractionation and confocal microscopy data suggest that Xcml protein is localized in the secretory pathway. We propose that Xcml may fine tune the gastrulation movements by modifying the cell surface and possibly extracellular matrix proteins passing through the secretory pathway.

Up- and down-regulation of Helix command-specific 2 (HCS2) gene expression in the nervous system of terrestrial snail Helix lucorum

A novel gene named Helix command-specific 2 (HCS2) was shown to be expressed predominantly in four giant parietal interneurons involved in withdrawal behavior of the terrestrial snail Helix lucorum L. and several single neurons in other ganglia. Decrease in spontaneous electrophysiological activity of neurons in the isolated CNS by 24h incubation in saline with elevated Mg(2+) concentration significantly decreased the number of HCS2-expressing neurons. Five short-term serotonin applications (each of 10microM), during a 24h incubation of the nervous system in saline induced expression of the HCS2 gene in many cells in cerebral, parietal, pleural and pedal ganglia. Dopamine applications under similar conditions were not effective. Application of anisomycin or cycloheximide, known to block protein synthesis, did not prevent the induction of HCS2 expression under serotonin influence. Skin injury elicited a significant increase in the number of HCS2-expressing cells 24h later in pleural and cerebral ganglia. Incubation of the isolated nervous system preparations for three days in culture medium elicited close to a maximum increase in number of HCS2-expressing cells. Elevation of the normal Mg(2+) concentration in the culture medium significantly decreased the number of cells demonstrating HCS2 expression. Application of the cAMP activator forskolin (10microM) increased the expression under Mg(2+), indicating that cAMP was involved in the up-regulation of HCS2. Application of thapsigargin (10microM), known to release Ca(2+) from intracellular stores, was also effective in increasing expression, suggesting participation of Ca(2+) in regulation of HCS2 expression. Cellular groups expressing the HCS2 gene under different conditions seem to be functionally related since it was demonstrated earlier that some neurons constituting these clusters are involved in the withdrawal behavior and the response of the organism to stress stimuli. From these results we suggest that the HCS2 pattern of expression can be down-regulated by a decrease in synaptic activity in the nervous system, and up-regulated by external noxious inputs, as well as the application of neurotransmitters and second messengers known to be involved in the withdrawal behavior and maintenance of isolated ganglia in culture medium. When up-regulated, the HCS2 expression appears, at least in part in neurons, to be involved in the withdrawal behavior.

Two-dimensional gene expression fingerprinting

In the present study we have developed the two-dimensional Gene Expression Fingerprinting (2-D GEF) procedure suitable for gene expression analysis and new gene discovery. The procedure is based on the two-dimensional gel display of 3'-terminal cDNA restriction fragments produced by one primary (first dimension) and several sequential secondary restriction digestions. Many thousands of individual sequences per cDNA sample can be visualized using this approach, which is also characterized by a high reproducibility, predictable spatial location of cDNA fragments on 2-D gels, and the potential for identifying cDNA fragments solely on the basis of their two-dimensional coordinates. Using this 2-D GEF method, we analyzed and compared the gene expression patterns of two related primitive hematopoietic cell lines, Kg-1 and Kg-1a. A total of 25 candidate differentially expressed sequences were identified, and for 75% of them the presumed expression pattern was confirmed by Northern blotting or reverse transcription-polymerase chain reaction. We also demonstrated that for 70% of bands, correct prediction of their identity could be made on the basis of two-dimensional coordinates, whereas the major part of incorrect predictions was caused by insufficient database quality.

Analysis of gene expression in subpopulations of murine hematopoietic stem and progenitor cells

OBJECTIVE

The aim of the present work was to study how functional differences between subsets of the murine hematopoietic stem/progenitor cell compartment are manifested on the level of different patterns of gene expression in these subsets.

MATERIALS AND METHODS

Amplified 3' terminal total cDNA fragment populations from four stem and progenitor cell fractions sorted using differential staining with Rhodamine 123 were prepared, and gene expression patterns were analyzed by Southern hybridization with a panel of gene markers.

RESULTS

For the vast majority of lineage-specific markers, no expression was detected in the long-term repopulating stem cell fraction. Expression of a number of key genes positively regulating entry and progression through the cell cycle was down-regulated in long-term repopulating cells, in accordance with the quiescent state of the latter. In contrast, certain but not all cell division kinase inhibitors were significantly up-regulated in long- and short-term repopulating stem cell fractions. Expression of several genes important for entry into the apoptotic pathway was moderately reduced in long-term repopulating cells. Messenger RNA levels of the transcription factors GATA-1, GATA-2, c-Myb and SCL were down-regulated in long-term repopulating cells, as compared to more mature stem/progenitor cells. Finally, expression of the MDR1a gene encoding the Pgp efflux pump was highest in long-term repopulating cells, and progressively decreased with maturation.

CONCLUSION

The patterns of gene expression in the stem/progenitor cell fractions are in good correlation with the known properties of adult hematopoietic stem/progenitor cells and may provide insight into molecular mechanisms underlying stem cell physiology.

Putative neuropeptides and an EF-hand motif region are encoded by a novel gene expressed in the four giant interneurons of the terrestrial snail

Nine giant interneurons located in the pleural and parietal ganglia of the terrestrial snail Helix lucorum L. were reported to be a key element in the network controlling withdrawal behaviour of the animal. Using a combination of complementary DNA subtraction cloning and differential screening approaches we have isolated a novel gene named HCS2 which is expressed predominantly in a subset of these interneurons. The predicted amino acid sequence of the HCS2 protein contains at the N-terminus a hydrophobic leader sequence and four putative neuropeptides, and at the C-terminus a perfect match to the consensus motif of the EF-hand family of the Ca2+-binding proteins. All four predicted neuropeptides bear a C-terminal signature sequence Tyr-Pro-Arg-X (where X is Ile, Leu, Val or Pro), and three of them are likely to be amidated. Physiological action of three synthetic peptides corresponding to the predicted mature HCS2 peptides mimics fairly well the described action of parietal interneurons on follower motoneurons controlling pneumostome closure. In situ hybridization experiments demonstrated that the HCS2 gene is selectively expressed in the four parietal giant interneurons, as well as in several small unidentified neurons. The onset of the HCS2 transcription during embryogenesis coincides temporally with the time-point when the first withdrawal responses of the embryo to tactile stimulation appear. We propose that the HCS2 gene encodes a hybrid precursor protein whose processed products act as neuromodulators or neurotransmitters mediating the withdrawal reactions of the snail, and in addition may participate in the calcium regulatory pathways or calcium homeostasis in command neurons.

A novel neuropeptide precursor gene is expressed in the terrestrial snail central nervous system by a group of neurons that control mating behavior

We report the isolation of a cDNA clone encoding a neuropeptide precursor named preproGFAD from the central nervous system (CNS) of the snail Helix lucorum. Analysis of the expression of this gene shows that it is neurospecific and expressed in several groups of CNS neurons. Most notable is the expression of preproGFAD gene in the right mesocerebrum, where the neurons controlling mating behavior are located. The expression in this particular region is observed in adult animals but not in juvenile ones. The preprohormone is 108 amino acids long and contains a hydrophobic leader peptide and eight Lys-Arg recognition sites for endoproteolysis. The post-translational processing of the prohormone may lead to the generation of seven tetrapeptides, Gly-Phe-Ala-Asp-COOH (GFAD). This peptide has the same sequence as two previously isolated peptides from a related snail, Achatina fulica. The first of them (achatin-I) contains D-Phe; the second (achatin-II) is its L-Phe-containing stereoisomer. Injection of synthetic D-GFAD in nanomolar concentrations into intact animals caused an increase of the heartbeat rate and opening of the genital atrium. In preparations containing CNS with intact innervation of reproductive organs, bath application of D-GFAD caused extensive movements of the penis but not of other reproductive organs. Intracellular activation of individual neurons expressing the preproGFAD gene also elicited penis movements. D-GFAD also suppressed activity of neurons modulating feeding behavior. Our data therefore indicate that the preproGFAD gene encodes the precursor of a neuropeptide that participates in the regulation of male mating behavior.

A novel marker of early epidermal differentiation: cDNA subtractive cloning starting on a single explant of Xenopus laevis gastrula epidermis

To understand the molecular mechanism underlying in the earliest steps of the embryonic ectoderm subdivision into epidermis and neuroectoderm, it would be important to isolate differentially expressed genes in presumptive neuroectoderm and epidermis at the gastrula stage, the period of the divergence of the two adjacent ectodermal compartments. Meanwhile, the most direct approach for such a task, i.e. subtractive enrichment of cDNA from neuroectodermal and epidermal explants with differentially expressed gene sequences, was difficult to realize because of the high number of explants needed for this technique. In the present paper we report a novel effective and quite simple method of cDNA subtractive enrichment, based on amplification of cDNA in vitro by polymerase chain reaction (PCR) and allowing to use a very small amount of initial cDNA samples. With this method we have cloned cDNA of a novel gene of Xenopus laevis, which was named XEP-1 for its specific expression in the presumptive epidermis starting from the midgastrula stage.

Characterization of a cDNA clone encoding pedal peptide in the terrestrial snail

We report the isolation of a Helix lucorum cDNA clone encoding a precursor of neuropeptides that are closely related to Aplysia and Tritonia pedal peptides (Pep). The predicted propeptide contains 20 copies of the two variants of Helix Pep interspersed with Lys-Arg endopeptidase cleavage sites. Northern blot hybridization revealed multiple Pep-hybridizing species in the Helix CNS RNA. The Pep gene was expressed by several identified serotonergic neurones in pedal and cerebral ganglia, groups of sensory neurones in procerebrum, peripheral neurones in olfactory bulb, mantle and foot, and group of neurones in pedal ganglia presumably involved in locomotion control. Pep mRNA was detected in several neurones at the early stages of nervous system development.

A novel murine cathelin-like protein expressed in bone marrow

A novel cDNA encoding a putative secreted protein was isolated from murine bone marrow. The encoded protein named MCLP (murine cathelin-like protein) was found to be highly homologous to the pig cathelin, and to four neutrophil antimicrobial polypeptides: CAP 18, indolicidin, Bac 5 and FALL-39. Secondary structure prediction studies identified a highly cationic region in the C-terminal part of prepro-MCLP with a tendency to adopt an amphipathic alpha-helical conformation, as observed in many antimicrobial peptides. However, no antibacterial activity was observed with the synthetic peptide corresponding to this region of MCLP.

Identification of two novel genes specifically expressed in the D-group neurons of the terrestrial snail CNS

A search for genes specifically expressed in the giant interneurons of parietal ganglia of the snail Helix lucorum yielded, among others, two genes named HDS1 and HDS2. According to data obtained by Northern hybridization and whole-mount in situ hybridization, both genes are neurospecific and expressed almost exclusively in the peptidergic D-group neurons (Sakharov, 1974) located in the right parietal ganglion. In situ hybridization of the HDS1 and HDS2 probes with CNS of several related species of the Helicoidea superfamily identified in all cases similarly located homologous groups of neurons. Sequencing of the near full-length cDNA copies of the HDS1 and HDS2 genes revealed open reading frames 107 and 102 amino acids long for HDS1 and HDS2, respectively. Both putative proteins contain a hydrophobic leader peptide and putative recognition sites for furin-like and PC-like endopeptidases. Predicted amino acid sequences of the HDS1 and HDS2 proteins were found to be moderately homologous to each other, as well as to the LYCP preprohormone expressed by the light yellow cells of the freshwater snail Lymnaea stagnalis. These results confirm an earlier hypothesis that the D-group of the Helix family and the light yellow cells of Lymnaea stagnalis represent homologous neuronal groups. Our data suggest that the HDS1 and HDS2 genes encode precursors of secreted molecules, most likely neuropeptides or neurohormones.

Genomic structure and alternative splicing of the murine bhk/ctk/ntk gene

Recently, we and others have cloned cDNAs encoding a second member of the Csk family of inhibitory protein kinases, which we termed Bhk [M.A. Ershler et al. (1994) Dokl. Akad. Nauk. 339, 679-683]. In the present study, two new distinct types of bhk mRNA were found in addition to the third form described previously. Analysis of the bhk genomic structure established that three exons participate in the alternative splicing of bhk mRNA.

Identification of differentially expressed genes by restriction endonuclease-based gene expression fingerprinting

A novel method for identification of differentially expressed genes has been developed. It is based on the consecutive restriction digestions of 3' terminal cDNA fragments to produce a fingerprint of gene expression. cDNA molecules are synthesized using a biotinylated oligo(dT) primer, digested with a frequently cutting restriction endonuclease and the 3'-terminal restriction fragments are isolated using streptavidin microbeads. After amplification by PCR, cDNA fragments are immobilized again on streptavidin beads, radiolabeled and treated sequentially with a set of restriction endonucleases. The products of individual enzymatic reactions from two or more different RNA populations are resolved by polyacrylamide gel electrophoresis and compared to reveal differentially expressed genes. This strategy enabled us to identify and clone the fragments of five genes expressed differentially in murine thymus and spleen. One of the genes was found to encode terminal deoxynucleotidyl transferase; others are apparently previously unknown genes.

Sequence of the cDNA encoding murine CRK4 protein kinase

A cDNA clone encoding murine CRK4 protein kinase [Ershler et al., Gene 124 (1993) 305-306] has been isolated and sequenced. The deduced amino acid (aa) sequence shows 85% overall identity with the Xenopus laevis MO15 PK (the catalytic subunit of CAK). The central parts of the CRK4 and MO15 proteins are characterized by an unusually high (97.5%) degree of aa sequence conservation.

Novel gene HCS1 is specifically expressed in the giant interneurones of the terrestrial snail

The terrestrial snail Helix lucorum is a promising model for molecular neurobiology since its central nervous system (CNS) is simple and contains many morphologically and functionally identified large neurones. Among these, the giant interneurones located in pleural and parietal ganglia are especially interesting because they trigger the withdrawal behaviour of the snail and participate in aversive conditioning. Here we describe the identification and characterization of a gene named HCS1 which is preferentially expressed in these interneurones. It encodes a putative protein 100 amino acids long containing an N-terminal hydrophobic leader peptide. No sequences with significant homology to HCS1 were found in the protein (Swiss-Prot) and nucleotide (EMBLbank) data libraries. We suppose that the product of this gene is a secreted protein, presumably a neuropeptide or a growth factor.

Novel CDC2-related protein kinases produced in murine hematopoietic stem cells

The polymerase chain reaction with degenerate primers was used for the amplification of cDNA encoding CDC2-related protein kinase (PK) sequences from murine hematopoietic stem cells. In total, nine different PK-encoding sequences were obtained. At least four of them encode previously unknown PKs.