Cellular Events of Multinucleated Giant Cells Formation During the Encystation of Entamoeba invadens

Abstract

Entamoeba histolytica, the causative agent of amoebiasis, does not form cysts in vitro, so reptilian pathogen Entamoeba invadens is used as an Entamoeba encystation model. During the in vitro encystation of E. invadens, a few multinucleated giant cells (MGC) were also appeared in the culture along with cysts. Like the cyst, these MGC's were also formed in the multicellular aggregates found in the encystation culture. Time-lapse live cell imaging revealed that MGC's were the result of repeated cellular fusion with fusion-competent trophozoites as a starting point. The early MGC were non-adherent, and they moved slowly and randomly in the media, but under confinement, MGC became highly motile and directionally persistent. The increased motility resulted in rapid cytoplasmic fissions, which indicated the possibility of continuous cell fusion and division taking place inside the compact multicellular aggregates. Following cell fusion, each nucleus obtained from the fusion-competent trophozoites gave rise to four nuclei with half genomic content. All the haploid nuclei in MGC later aggregated and fused to form a polyploid nucleus. These observations have important implications on Entamoeba biology as they point toward the possibility of E. invadens undergoing sexual or parasexual reproduction.

The NAD+ Responsive Transcription Factor ERM-BP Functions Downstream of Cellular Aggregation and Is an Early Regulator of Development and Heat Shock Response in Entamoeba

“…Formation of a small numbers of multinucleated giant cells have been observed during encystation of E. invadens. In E. invadens, these MGCs were formed in multicellular aggregates through the cyto-fusion of multiple trophozoites in the encystation culture media due to osmotic stress and glucose depletion; however, other stress responses, such as heat shock or oxidative stress did not induce MGC formation in E. invadens as described earlier (Krishnan and Ghosh, 2018). Cell fusion and formation of MGC is a common feature that develops during various inflammatory reactions, such as infection with tuberculosis, herpes, HIV or other foreign body (Dargent et al, 2000;Brodbeck and Anderson, 2009;McClean and Tobin, 2016).…”

“…Formation of multi-nucleated giant cells (MGC) can increase in response to an infection, such as tuberculosis, herpes, HIV, or other foreign body (Anderson, 2000;Dargent et al, 2000;Brodbeck and Anderson, 2009;McClean and Tobin, 2016). Formation of MGC is also observed in the development of soildwelling amoeba Dictyostelium discoideum during macrocyst formation (Ishida et al, 2005) and in E. invadens during the encystation (Krishnan and Ghosh, 2018). In encystation media Entamoeba form aggregates and multiple cells go through cytofusion and transform into giant cells (Figure 2A).…”

Polarized Entamoeba: A model for stable bleb driven motility

“…During Under-agarose assay, the velocity of both Eh and Ei cells, under the agarose was found to be ~1 µm/s even in the absence of Ptx (Fig.3E Control). The multinucleated giant cells of Ei have shown a similar increase in motility under confinement (Krishnan and Ghosh, 2018) and this could be due to the induction of bleb-driven movement by mechanical resistance (Zatulovskiy et al, 2014). While velocity increased, motility remained random with directness values of 0.60 and 0.49 for Ei and Eh, respectively ( Fig.3F, control).…”

Stress‐responsive Entamoeba topoisomerase II: a potential antiamoebic target

“…Association of a sexual process like meiosis with encystation has long been a point of debate. Low levels of allelic heterozygosities [8], evidence of homologous recombination [9], the presence of meiotic genes and their upregulation during encystation [10], and the formation and aggregation of haploid nuclei in multinucleated giant cells during encystation [11] indicate the occurrence of meiosis-like processes and homologous recombination during glucose deprived encystation.Across the biological world, all key DNA processes are associated with a group of ubiquitous enzymes called topoisomerases. These enzymes maintain DNA topology by creating breaks in the DNA and allowing strand passage.…”

“…Association of a sexual process like meiosis with encystation has long been a point of debate. Low levels of allelic heterozygosities , evidence of homologous recombination , the presence of meiotic genes and their upregulation during encystation , and the formation and aggregation of haploid nuclei in multinucleated giant cells during encystation indicate the occurrence of meiosis‐like processes and homologous recombination during glucose deprived encystation.…”