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New insights into the apoptotic process in mollusks: characterization of caspase genes in Mytilus galloprovincialis.

Romero A, Estévez-Calvar N, Dios S, Figueras A, Novoa B - PLoS ONE (2011)

Bottom Line: Caspase proteins constitute the core of the apoptotic machinery and can be categorized as either initiators or effectors of apoptosis.Evaluation of the genes' tissue expression patterns revealed extremely high expression levels within the gland and gills, where the apoptotic process is highly active due to the clearance of damaged cells.Hemocytes also showed high expression values, probably due to of the role of apoptosis in the defense against pathogens.

View Article: PubMed Central - PubMed

Affiliation: Instituto de Investigaciones Marinas, Consejo Superior de Investigaciones Científicas, Vigo, Spain.

ABSTRACT
Apoptosis is an essential biological process in the development and maintenance of immune system homeostasis. Caspase proteins constitute the core of the apoptotic machinery and can be categorized as either initiators or effectors of apoptosis. Although the genes encoding caspase proteins have been described in vertebrates and in almost all invertebrate phyla, there are few reports describing the initiator and executioner caspases or the modulation of their expression by different stimuli in different apoptotic pathways in bivalves. In the present work, we characterized two initiator and four executioner caspases in the mussel Mytilus galloprovincialis. Both initiators and executioners showed structural features that make them different from other caspase proteins already described. Evaluation of the genes' tissue expression patterns revealed extremely high expression levels within the gland and gills, where the apoptotic process is highly active due to the clearance of damaged cells. Hemocytes also showed high expression values, probably due to of the role of apoptosis in the defense against pathogens. To understand the mechanisms of caspase gene regulation, hemocytes were treated with UV-light, environmental pollutants and pathogen-associated molecular patterns (PAMPs) and apoptosis was evaluated by microscopy, flow cytometry and qPCR techniques. Our results suggest that the apoptotic process could be tightly regulated in bivalve mollusks by overexpression/suppression of caspase genes; additionally, there is evidence of caspase-specific responses to pathogens and pollutants. The apoptotic process in mollusks has a similar complexity to that of vertebrates, but presents unique features that may be related to recurrent exposure to environmental changes, pollutants and pathogens imposed by their sedentary nature.

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Histological changes related to the apoptotic process observed in hemocytes treated with UV light.A and D: Control granulocytes and small hyalinocytes not treated with UV-light. B: Slight chromatin condensation in granulocytes observed after 3 h pt. C and F: Appearance of intracellular bodies, positive stained for DNA, inside the cytoplasm of granulocytes and hyalinocytes, respectively after 24 h pt. E: Chromatin condensation in small hyalinocytes after 6 h pt.
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pone-0017003-g006: Histological changes related to the apoptotic process observed in hemocytes treated with UV light.A and D: Control granulocytes and small hyalinocytes not treated with UV-light. B: Slight chromatin condensation in granulocytes observed after 3 h pt. C and F: Appearance of intracellular bodies, positive stained for DNA, inside the cytoplasm of granulocytes and hyalinocytes, respectively after 24 h pt. E: Chromatin condensation in small hyalinocytes after 6 h pt.

Mentions: Histological changes related to the apoptotic process were observed in hemocytes treated with UV-light (Figure 6). A sequential increase in morphological changes was observed during the time course. As early as 3 h post treatment (pt), a slight chromatin condensation was observed. Due to the small size of hyalinocytes, this characteristic was more clearly observed in granulocytes (Figure 6B). No morphological changes were observed at 0 and 1 h pt (data not shown). After 6 h pt, morphological changes were more evident and many dense particles were observed inside the nuclei in both types of hemocytes (Figure 6E). Apoptotic changes were highly evident after 24 h pt, when cytoplasmic vacuolization and intracellular bodies were present. These intracellular bodies were positive stained for DNA and appeared to be nuclear fragments commonly seen inside the apoptotic cells (Figures 6C and 6F). None of the related histological changes were detected in the control groups (Figures 6A and 6D).


New insights into the apoptotic process in mollusks: characterization of caspase genes in Mytilus galloprovincialis.

Romero A, Estévez-Calvar N, Dios S, Figueras A, Novoa B - PLoS ONE (2011)

Histological changes related to the apoptotic process observed in hemocytes treated with UV light.A and D: Control granulocytes and small hyalinocytes not treated with UV-light. B: Slight chromatin condensation in granulocytes observed after 3 h pt. C and F: Appearance of intracellular bodies, positive stained for DNA, inside the cytoplasm of granulocytes and hyalinocytes, respectively after 24 h pt. E: Chromatin condensation in small hyalinocytes after 6 h pt.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3037946&req=5

pone-0017003-g006: Histological changes related to the apoptotic process observed in hemocytes treated with UV light.A and D: Control granulocytes and small hyalinocytes not treated with UV-light. B: Slight chromatin condensation in granulocytes observed after 3 h pt. C and F: Appearance of intracellular bodies, positive stained for DNA, inside the cytoplasm of granulocytes and hyalinocytes, respectively after 24 h pt. E: Chromatin condensation in small hyalinocytes after 6 h pt.
Mentions: Histological changes related to the apoptotic process were observed in hemocytes treated with UV-light (Figure 6). A sequential increase in morphological changes was observed during the time course. As early as 3 h post treatment (pt), a slight chromatin condensation was observed. Due to the small size of hyalinocytes, this characteristic was more clearly observed in granulocytes (Figure 6B). No morphological changes were observed at 0 and 1 h pt (data not shown). After 6 h pt, morphological changes were more evident and many dense particles were observed inside the nuclei in both types of hemocytes (Figure 6E). Apoptotic changes were highly evident after 24 h pt, when cytoplasmic vacuolization and intracellular bodies were present. These intracellular bodies were positive stained for DNA and appeared to be nuclear fragments commonly seen inside the apoptotic cells (Figures 6C and 6F). None of the related histological changes were detected in the control groups (Figures 6A and 6D).

Bottom Line: Caspase proteins constitute the core of the apoptotic machinery and can be categorized as either initiators or effectors of apoptosis.Evaluation of the genes' tissue expression patterns revealed extremely high expression levels within the gland and gills, where the apoptotic process is highly active due to the clearance of damaged cells.Hemocytes also showed high expression values, probably due to of the role of apoptosis in the defense against pathogens.

View Article: PubMed Central - PubMed

Affiliation: Instituto de Investigaciones Marinas, Consejo Superior de Investigaciones Científicas, Vigo, Spain.

ABSTRACT
Apoptosis is an essential biological process in the development and maintenance of immune system homeostasis. Caspase proteins constitute the core of the apoptotic machinery and can be categorized as either initiators or effectors of apoptosis. Although the genes encoding caspase proteins have been described in vertebrates and in almost all invertebrate phyla, there are few reports describing the initiator and executioner caspases or the modulation of their expression by different stimuli in different apoptotic pathways in bivalves. In the present work, we characterized two initiator and four executioner caspases in the mussel Mytilus galloprovincialis. Both initiators and executioners showed structural features that make them different from other caspase proteins already described. Evaluation of the genes' tissue expression patterns revealed extremely high expression levels within the gland and gills, where the apoptotic process is highly active due to the clearance of damaged cells. Hemocytes also showed high expression values, probably due to of the role of apoptosis in the defense against pathogens. To understand the mechanisms of caspase gene regulation, hemocytes were treated with UV-light, environmental pollutants and pathogen-associated molecular patterns (PAMPs) and apoptosis was evaluated by microscopy, flow cytometry and qPCR techniques. Our results suggest that the apoptotic process could be tightly regulated in bivalve mollusks by overexpression/suppression of caspase genes; additionally, there is evidence of caspase-specific responses to pathogens and pollutants. The apoptotic process in mollusks has a similar complexity to that of vertebrates, but presents unique features that may be related to recurrent exposure to environmental changes, pollutants and pathogens imposed by their sedentary nature.

Show MeSH
Related in: MedlinePlus