1
|
Wesel J, Shuman J, Bastuzel I, Dickerson J, Ingram-Smith C. Encystation of Entamoeba histolytica in Axenic Culture. Microorganisms 2021; 9:873. [PMID: 33919506 PMCID: PMC8074197 DOI: 10.3390/microorganisms9040873] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2021] [Revised: 04/15/2021] [Accepted: 04/16/2021] [Indexed: 12/16/2022] Open
Abstract
Entamoeba histolytica is a parasitic protozoan that causes amoebic dysentery, which affects approximately 90 million people each year worldwide. E. histolytica is transmitted through ingestion of food and water contaminated with the cyst form, which undergoes excystation in the small intestine to the trophozoite form that colonizes the large intestine. The reptile pathogen Entamoeba invadens has served as a model for studying stage conversion between the trophozoite and cyst form due to lack of reproducible encystation of E. histolytica in the laboratory. Although much has been learned about encystation and excystation using E. invadens, the findings do not fully translate to E. histolytica due to the extensive genetic and host differences between these species. Here, we present the first reproducible encystation of E. histolytica in vitro. The cysts produced were viable and displayed the four characteristic hallmarks: round shape, chitinous cell wall, tetranucleation, and detergent resistance. Using flow cytometry analysis, glucose limitation and high cell density were key for encystation, as for E. invadens. Entry into encystation was enhanced by the short-chain fatty acids acetate and propionate, unlike for E. invadens. This new model will now allow the further study of E. histolytica stage conversion, transmission, and treatment.
Collapse
Affiliation(s)
- Jordan Wesel
- Department of Genetics and Biochemistry, Clemson University, Clemson, SC 29634, USA; (J.W.); (J.S.); (I.B.); (J.D.)
- Eukaryotic Pathogens Innovation Center, Clemson University, Clemson, SC 29634, USA
| | - Jennifer Shuman
- Department of Genetics and Biochemistry, Clemson University, Clemson, SC 29634, USA; (J.W.); (J.S.); (I.B.); (J.D.)
- Eukaryotic Pathogens Innovation Center, Clemson University, Clemson, SC 29634, USA
| | - Irem Bastuzel
- Department of Genetics and Biochemistry, Clemson University, Clemson, SC 29634, USA; (J.W.); (J.S.); (I.B.); (J.D.)
- Eukaryotic Pathogens Innovation Center, Clemson University, Clemson, SC 29634, USA
| | - Julie Dickerson
- Department of Genetics and Biochemistry, Clemson University, Clemson, SC 29634, USA; (J.W.); (J.S.); (I.B.); (J.D.)
- Eukaryotic Pathogens Innovation Center, Clemson University, Clemson, SC 29634, USA
| | - Cheryl Ingram-Smith
- Department of Genetics and Biochemistry, Clemson University, Clemson, SC 29634, USA; (J.W.); (J.S.); (I.B.); (J.D.)
- Eukaryotic Pathogens Innovation Center, Clemson University, Clemson, SC 29634, USA
| |
Collapse
|
2
|
Bínová E, Bína D, Nohýnková E. DNA content in Acanthamoeba during two stress defense reactions: Encystation, pseudocyst formation and cell cycle. Eur J Protistol 2020; 77:125745. [PMID: 33218872 DOI: 10.1016/j.ejop.2020.125745] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2020] [Revised: 08/22/2020] [Accepted: 10/19/2020] [Indexed: 12/01/2022]
Abstract
During environmental stress, the vegetative cells of the facultative pathogenic amoeba Acanthamoeba castellanii reversibly differentiate into resistant dormant stages, namely, cysts or pseudocysts. The type of resistant stage depends on the nature and duration of the stressor. Cell differentiation is accompanied by changes in morphology and cellular metabolism. Moreover, cell differentiation is also expected to be closely linked to the regulation of the cell cycle and, thus, to cellular DNA content. While the existence of the resistant stages in A. castellanii is well known, there is no consensus regarding the relationship between differentiation and cell cycle progression. In the present work, we used flow cytometry analysis to explore the changes in the DNA content during Acanthamoeba encystation and pseudocyst formation. Our results strongly indicate that A. castellanii enters encystation from the G2 phase of the cell cycle. In contrast, differentiation into pseudocysts can begin in the G1 and G2 phases. In addition, we present a phylogenetic analysis and classification of the main cell cycle regulators, namely, cyclin-dependent kinases and cyclins that are found in the genome of A. castellanii.
Collapse
Affiliation(s)
- Eva Bínová
- Institute of Immunology and Microbiology, First Faculty of Medicine, Charles University, Studnickova 7, 128 00 Prague 2, Czech Republic
| | - David Bína
- Faculty of Science, University of South Bohemia, Branišovská 1760 and The Czech Academy of Sciences, Biology Centre, Branišovská 31, 370 05 České Budějovice, Czech Republic
| | - Eva Nohýnková
- Institute of Immunology and Microbiology, First Faculty of Medicine, Charles University, Studnickova 7, 128 00 Prague 2, Czech Republic.
| |
Collapse
|
3
|
Singh N, Bhattacharya A, Bhattacharya S. Homologous Recombination Occurs in Entamoeba and Is Enhanced during Growth Stress and Stage Conversion. PLoS One 2013; 8:e74465. [PMID: 24098652 PMCID: PMC3787063 DOI: 10.1371/journal.pone.0074465] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2013] [Accepted: 08/01/2013] [Indexed: 12/28/2022] Open
Abstract
Homologous recombination (HR) has not been demonstrated in the parasitic protists Entamoeba histolytica or Entamoeba invadens, as no convenient method is available to measure it. However, HR must exist to ensure genome integrity, and possible genetic exchange, especially during stage conversion from trophozoite to cyst. Here we show the up regulation of mitotic and meiotic HR genes in Entamoeba during serum starvation, and encystation. To directly demonstrate HR we use a simple PCR-based method involving inverted repeats, which gives a reliable read out, as the recombination junctions can be determined by sequencing the amplicons. Using this read out, we demonstrate enhanced HR under growth stress in E. histolytica, and during encystation in E. invadens. We also demonstrate recombination between chromosomal inverted repeats. This is the first experimental demonstration of HR in Entamoeba and will help future investigations into this process, and to explore the possibility of meiosis in Entamoeba.
Collapse
Affiliation(s)
- Nishant Singh
- School of Environmental Sciences, Jawaharlal Nehru University, New Delhi, India
| | - Alok Bhattacharya
- School of Life Sciences, Jawaharlal Nehru University, New Delhi, India
| | - Sudha Bhattacharya
- School of Environmental Sciences, Jawaharlal Nehru University, New Delhi, India
- * E-mail:
| |
Collapse
|
4
|
Actin, RhoA, and Rab11 participation during encystment in Entamoeba invadens. BIOMED RESEARCH INTERNATIONAL 2013; 2013:919345. [PMID: 24175308 PMCID: PMC3794519 DOI: 10.1155/2013/919345] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/06/2013] [Revised: 08/09/2013] [Accepted: 08/09/2013] [Indexed: 11/17/2022]
Abstract
In the genus Entamoeba, actin reorganization is necessary for cyst differentiation; however, its role is still unknown. The aim of this work was to investigate the role of actin and encystation-related proteins during Entamoeba invadens encystation. Studied proteins were actin, RhoA, a small GTPase involved through its effectors in the rearrangement of the actin cytoskeleton; Rab11, a protein involved in the transport of encystation vesicles; and enolase, as an encystment vesicles marker. Results showed a high level of polymerized actin accompanied by increased levels of RhoA-GTP during cell rounding and loss of vacuoles. Cytochalasin D, an actin polymerization inhibitor, and Y27632, an inhibitor of RhoA activity, reduced encystment in 80%. These inhibitors also blocked cell rounding, disposal of vacuoles, and the proper formation of the cysts wall. At later times, F-actin and Rab11 colocalized with enolase, suggesting that Rab11 could participate in the transport of the cyst wall components through the F-actin cytoskeleton. These results suggest that actin cytoskeleton rearrangement is playing a decisive role in determining cell morphology changes and helping with the transport of cell wall components to the cell surface during encystment of E. invadens.
Collapse
|
5
|
Singh N, Bhattacharya S, Paul J. Entamoeba invadens: dynamics of DNA synthesis during differentiation from trophozoite to cyst. Exp Parasitol 2010; 127:329-33. [PMID: 20727884 DOI: 10.1016/j.exppara.2010.08.013] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2010] [Revised: 05/26/2010] [Accepted: 08/13/2010] [Indexed: 11/24/2022]
Abstract
The DNA dynamics which mediate conversion of uni-nucleate trophozoite into quadrinucleate cyst in Entamoeba histolytica is not well understood. Here, we have addressed this question in Entamoeba invadens (a model system for encystation) through a detailed time course study of the differentiation process. We combined flow cytometric analysis with the change in rate of thymidine incorporation and the number of nuclei per cell. Our data shows that during encystment the cell population passes through three phases: (1) Early phase (0-8h); of rapid DNA synthesis which may correspond to completion of ongoing DNA replication. Bi-nucleated cells increase with concomitant drop in uni-nucleated cells. (2) Commitment phase (8-24h); in which DNA synthesis rate slows down. Possibly new rounds of replication are initiated which proceed slowly, followed by mitosis at 20 h. After this the number of bi- and uni-nucleated cells gradually decline and the tri- and tetra-nucleated cells begin to increase. (3) Consolidation phase (24-72 h); in which the rate of DNA synthesis shows a small increase till 32 h and then begins to decline. The G2/M peak reappears at 48 h, showing that more rounds of DNA replication may be getting completed, followed by nuclear division. By 72 h the encystment is virtually complete. The bi-nucleated stage could be an intermediate both in the conversion of trophozoite to cyst and back. Our study provides a comprehensive view of DNA dynamics during encystation and excystation of E. invadens.
Collapse
Affiliation(s)
- Nishant Singh
- School of Environmental Sciences, Jawaharlal Nehru University, New Delhi, India
| | | | | |
Collapse
|
6
|
Aguilar-Díaz H, Díaz-Gallardo M, Laclette JP, Carrero JC. In vitro induction of Entamoeba histolytica cyst-like structures from trophozoites. PLoS Negl Trop Dis 2010; 4:e607. [PMID: 20169067 PMCID: PMC2821915 DOI: 10.1371/journal.pntd.0000607] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2009] [Accepted: 12/29/2009] [Indexed: 11/18/2022] Open
Abstract
Inhibition of encystment can be conceived as a potentially useful mechanism to block the transmission of Entamoeba histolytica under natural conditions. Unfortunately, amoeba encystment has not been achieved in vitro and drugs inhibiting the formation of cysts are not available. Luminal conditions inducing encystment in vivo are also unknown, but cellular stress such as exposure to reactive oxygen species from immune cells or intestinal microbiota could be involved. A role for certain divalent cations as cofactors of enzymes involved in excystment has also been described. In this study, we show that trophozoite cultures, treated with hydrogen peroxide in the presence of trace amounts of several cations, transform into small-sized spherical and refringent structures that exhibit resistance to different detergents. Ultrastructural analysis under scanning and transmission electron microscopy revealed multinucleated structures (some with four nuclei) with smooth, thick membranes and multiple vacuoles. Staining with calcofluor white, as well as an ELISA binding assay using wheat germ agglutinin, demonstrated the presence of polymers of N-acetylglucosamine (chitin), which is the primary component of the natural cyst walls. Over-expression of glucosamine 6-phosphate isomerase, likely to be the rate-limiting enzyme in the chitin synthesis pathway, was also confirmed by RT-PCR. These results suggest that E. histolytica trophozoites activated encystment pathways when exposed to our treatment.
Collapse
Affiliation(s)
- Hugo Aguilar-Díaz
- Department of Immunology, Instituto de Investigaciones Biomédicas, Universidad Nacional Autónoma de México, Ciudad de México, México
| | - Martha Díaz-Gallardo
- Department of Developmental Genetics and Molecular Physiology, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Morelos, México
| | - Juan P. Laclette
- Department of Immunology, Instituto de Investigaciones Biomédicas, Universidad Nacional Autónoma de México, Ciudad de México, México
- * E-mail: (JPL); (JCC)
| | - Julio C. Carrero
- Department of Immunology, Instituto de Investigaciones Biomédicas, Universidad Nacional Autónoma de México, Ciudad de México, México
- * E-mail: (JPL); (JCC)
| |
Collapse
|
7
|
Mukherjee C, Clark CG, Lohia A. Entamoeba shows reversible variation in ploidy under different growth conditions and between life cycle phases. PLoS Negl Trop Dis 2008; 2:e281. [PMID: 18714361 PMCID: PMC2500184 DOI: 10.1371/journal.pntd.0000281] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2008] [Accepted: 07/18/2008] [Indexed: 11/18/2022] Open
Abstract
Under axenic growth conditions, trophozoites of Entamoeba histolytica contain heterogenous amounts of DNA due to the presence of both multiple nuclei and different amounts of DNA in individual nuclei. In order to establish if the DNA content and the observed heterogeneity is maintained during different growth conditions, we have compared E. histolytica cells growing in xenic and axenic cultures. Our results show that the nuclear DNA content of E. histolytica trophozoites growing in axenic cultures is at least 10 fold higher than in xenic cultures. Re-association of axenic cultures with their bacterial flora led to a reduction of DNA content to the original xenic values. Thus switching between xenic and axenic growth conditions was accompanied by significant changes in the nuclear DNA content of this parasite. Changes in DNA content during encystation-excystation were studied in the related reptilian parasite E. invadens. During excystation of E. invadens cysts, it was observed that the nuclear DNA content increased approximately 40 fold following emergence of trophozoites in axenic cultures. Based on the observed large changes in nuclear size and DNA content, and the minor differences in relative abundance of representative protein coding sequences, rDNA and tRNA sequences, it appears that gain or loss of whole genome copies may be occurring during changes in the growth conditions. Our studies demonstrate the inherent plasticity and dynamic nature of the Entamoeba genome in at least two species. In contrast to the perception that DNA content of an organism is stable and maintained during different conditions and life cycle stages, new evidence shows that many organisms display changes in their DNA content at different stages of their life cycle. We have earlier identified intra-cellular and inter-cellular differences in DNA content of the protist pathogen Entamoeba histolytica and established that this organism can tolerate large variations in DNA content during axenic culture. In this study we have made an important advancement in the understanding of amoeba biology where we have shown that changes in growth conditions and life cycle stages are accompanied by large differences in DNA content involving gain or loss of whole genome copies. This property may well regulate the outcome of infection and subsequently the disease.
Collapse
Affiliation(s)
| | - C. Graham Clark
- Department of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, London, United Kingdom
| | - Anuradha Lohia
- Department of Biochemistry, Bose Institute, Kolkata, India
- * E-mail:
| |
Collapse
|
8
|
Lohia A, Mukherjee C, Majumder S, Dastidar PG. Genome re-duplication and irregular segregation occur during the cell cycle of Entamoeba histolytica. Biosci Rep 2008; 27:373-84. [PMID: 17592766 DOI: 10.1007/s10540-007-9058-8] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
Abstract
Heterogeneity of genome content is commonly observed in axenic cultures of Entamoeba histolytica. Cells with multiple nuclei and nuclei with heterogenous genome contents suggest that regulatory mechanisms that ensure alternation of DNA synthesis and mitosis are absent in this organism. Therefore, several endo-reduplicative cycles may occur without mitosis. The data also shows that unlike other endo-reduplicating organisms, E.histolytica does not undergo a precise number of endo-reduplicative cycles. We propose that irregular endo-reduplication and genome partitioning lead to heterogeneity in the genome content of E.histolytica trophozoites in their proliferative phase. The goal of future studies should be aimed at understanding the mechanisms that are involved in (a) accumulation of multiple genome contents in a single nucleus; (b) genome segregation in nuclei that contain multiple genome contents and (c) maintenance of genome fidelity in E. histolytica.
Collapse
Affiliation(s)
- Anuradha Lohia
- Department of Biochemistry, Bose Institute, Kolkata, 700054, India.
| | | | | | | |
Collapse
|
9
|
Meza I, Talamás-Rohana P, Vargas MA. The Cytoskeleton of Entamoeba histolytica: Structure, Function, and Regulation by Signaling Pathways. Arch Med Res 2006; 37:234-43. [PMID: 16380324 DOI: 10.1016/j.arcmed.2005.09.008] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2005] [Accepted: 09/26/2005] [Indexed: 01/16/2023]
Abstract
Pathogenesis in the parasite Entamoeba histolytica has been related to motility of the trophozoites. Motility is an important feature in amebas as they perform multiple motile functions during invasion of host tissues. As motility depends on the organization and regulation of the cytoskeleton elements, in particular of the actin cytoskeleton, the study of the molecular components of the machinery responsible for movement has been a key aspect to study in this parasite. Although many of the components have high homology in amino acid sequence and function to those characterized in higher eukaryotic cells, there are important differences to suggest that parasitic organisms may have developed adaptative differences that could be useful as targets to stop invasion. The purpose of this review is to evaluate current knowledge about the cytoskeleton of E. histolytica and the ways in which the parasite controls motility.
Collapse
Affiliation(s)
- Isaura Meza
- Departamentos de Biomedicina Molecular, Centro de Investigación y de Estudios, Avanzados del IPN, México D.F., México.
| | | | | |
Collapse
|
10
|
Bhattacharya A, Padhan N, Jain R, Bhattacharya S. Calcium-Binding Proteins of Entamoeba histolytica. Arch Med Res 2006; 37:221-5. [PMID: 16380322 DOI: 10.1016/j.arcmed.2005.10.002] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2005] [Accepted: 10/04/2005] [Indexed: 10/25/2022]
Abstract
Calcium plays an essential role in many fundamental processes in almost all eukaryotic cells including protozoan parasite Entamoeba histolytica. Many of the calcium-mediated processes are carried out through the help of calcium-binding proteins (CaBPs). A few of these E. histolytica CaBPs have been described before. These proteins are unique to this organism and are thought to be essential. Availability of genome sequence has opened up the possibility of studying CaBPs at the whole genome level. In this preliminary report, we describe the complement of CaBPs present in E. histolytica. A large fraction of these genes are expressed in the trophozoites and are likely to be functional. The results suggest a number of pathways that are involved in calcium signaling and may be unique for this organism.
Collapse
Affiliation(s)
- Alok Bhattacharya
- School of Life Sciences, Jawaharlal Nehru University, New Delhi, India.
| | | | | | | |
Collapse
|
11
|
Byers J, Eichinger D. Entamoeba invadens: restriction of ploidy by colonic short chain fatty acids. Exp Parasitol 2005; 110:203-6. [PMID: 15955313 DOI: 10.1016/j.exppara.2005.02.019] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2005] [Revised: 02/21/2005] [Accepted: 02/23/2005] [Indexed: 10/25/2022]
Abstract
The DNA content of Entamoeba parasites appears to be regulated by an unusual mechanism. This conclusion, however, was based on experiments that examined parasites grown in media that did not contain short chain fatty acids (SCFAs) normally found in the colonic lumen. Since one of these SCFAs, butyrate, is known to affect DNA replication in eukaryotic cells, we examined the effect of SCFAs on Entamoeba trophozoite DNA content. Similar to reports from others, we found that Entamoeba invadens trophozoite cultures grown in conventional medium (TYI-S-33) contained cells with 2N, 4N, 8N, and 16N amounts of DNA. In contrast, cultures grown in TYI medium containing colonic SCFAs added in place of glucose contained a minor population with 2N, a major population with 4N, and very few cells with higher amounts of DNA. SCFAs also prevented the normal increase in the number of nuclei per cell in trophozoites that were induced to encyst. These results suggest that E. invadens trophozoite stage parasites growing in the intestine in the presence of high amounts of SCFAs have a ploidy range restricted to 2N/4N. Axenic growth of trophozoites in the absence of SCFAs, however, appears to allow trophozoites to increase the amount of DNA per cell, which they must do during the normal encystment process.
Collapse
Affiliation(s)
- Jennifer Byers
- Department of Medical Parasitology, New York University School of Medicine, New York, NY 10010, USA
| | | |
Collapse
|
12
|
Chakrabarty P, Sethi DK, Padhan N, Kaur KJ, Salunke DM, Bhattacharya S, Bhattacharya A. Identification and characterization of EhCaBP2. A second member of the calcium-binding protein family of the protozoan parasite Entamoeba histolytica. J Biol Chem 2004; 279:12898-908. [PMID: 14711825 DOI: 10.1074/jbc.m304716200] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Entamoeba histolytica, an early branching eukaryote, is the etiologic agent of amebiasis. Calcium plays a pivotal role in the pathogenesis of amebiasis by modulating the cytopathic properties of the parasite. However, the mechanistic role of Ca(2+) and calcium-binding proteins in the pathogenesis of E. histolytica remains poorly understood. We had previously characterized a novel calcium-binding protein (EhCaBP1) from E. histolytica. Here, we report the identification and partial characterization of an isoform of this protein, EhCaBP2. Both EhCaBPs have four canonical EF-hand Ca(2+) binding domains. The two isoforms are encoded by genes of the same size (402 bp). Comparison between the two genes showed an overall identity of 79% at the nucleotide sequence level. This identity dropped to 40% in the 75-nucleotide central linker region between the second and third Ca(2+) binding domains. Both of these genes are single copy, as revealed by Southern hybridization. Analysis of the available E. histolytica genome sequence data suggested that the two genes are non-allelic. Homology-based structural modeling showed that the major differences between the two EhCaBPs lie in the central linker region, normally involved in binding target molecules. A number of studies indicated that EhCaBP1 and EhCaBP2 are functionally different. They bind different sets of E. histolytica proteins in a Ca(2+)-dependent manner. Activation of endogenous kinase was also found to be unique for the two proteins and the Ca(2+) concentration required for their optimal functionality was also different. In addition, a 12-mer peptide was identified from a random peptide library that could differentially bind the two proteins. Our data suggest that EhCaBP2 is a new member of a class of E. histolytica calcium-binding proteins involved in a novel calcium signal transduction pathway.
Collapse
Affiliation(s)
- Paramita Chakrabarty
- School of Environmental Sciences, Jawaharlal Nehru University, New Mehrauli Road, New Delhi-110067, India
| | | | | | | | | | | | | |
Collapse
|
13
|
|
14
|
Abstract
The alternation of DNA replication in S phase and chromosome segregation in M phase is a hallmark in the cell cycle of most well-studied eukaryotes and ensures that the progeny do not have more than the normal complement of genes and chromosomes. An exception to this rule has been described in cancer cells that occasionally become polyploid as a result of failure to restrain S phase despite the failure to undergo complete mitosis. Here, we describe the cell division cycle of the human pathogen, Entamoeba histolytica, which routinely accumulates polyploid cells. We have studied DNA synthesis in freshly subcultured cells and show that, unlike most eukaryotes, Entamoeba cells reduplicate their genome several times before cell division occurs. Furthermore, polyploidy may occur without nuclear division so that single nuclei may contain 1-10 times or more genome contents. Multinucleated cells may also accumulate several genome contents in each nuclei of one cell. Thus, checkpoints that normally prevent DNA reduplication until after cytokinesis in most eukaryotes are not observed in E. histolytica.
Collapse
Affiliation(s)
- Suchismita Das
- Department of Biochemistry, Bose Institute, P1/12 CIT Scheme VIIM, Calcutta 700 054, India
| | | |
Collapse
|