The Three Line PST Stem Cell System of Entamoeba Invadens As One of the Earliest Stem Cell

II. The three line PST stem cell system ofEntamoeba invadensas one of the earliest stem cell systemstoday*

(revised*)

Vladimir F. Niculescu*

*Present address: D-86420 Diedorf, Germany; E-mail:

ABSTRACT The pathogen protistEntamoeba invadens contains relict mitochondria (mitosomes)

and adapts its anaerobic energy metabolism to environmental conditions that change constantly.We identified in hypoxic cultures of E. invadens three ancient stem cell types (AnSC)and athree line stem cell system (P-S-T)containing primary, secondary and tertiary self renewing lines (SRL).Each SRL produces a differentiated cell fraction composed of mitotically arrested cells(MAC)exiting cell cycle. The primary self-renewing line p-SRL is astem cell linegenerated by the eight metacystic amoebulae (A) via A/P conversion. The p-SRLcell line has bilateral conversion capacity, converting by passaging either to the secondary s-SRL (oxygenic P/S conversion) or,alternatively, to the tertiary t-SRL(hypoxic P/T conversion). Advanced hypoxia blocks s-SRLproliferationand leads to S/T conversion.P and T subpopulations are cyst-free, comprising long-livingMAC fractions (p-MAC,t-MAC) that re-enter the cell cycle in order to replenishthemotherSRL.s-SRL produces precysts for cyclic-encystment (CE) giving rise to CEcysts by an autonomous terminal differentiation. (ATD). Another pathway of encystment is the induced terminal differentiation (ITD) of T cells in OCB sediments without nutrients (hypoosmotic encystment medium, AaEM). Hypoxic starvation induces T cells to totipotent iTP progenitors, the innercyst cell of the cysts. Both ATD and ITDcysts are viable. Ancient single- celled organisms with anaerobe energy metabolismas E. invadensposess early mechanisms for induced totipotency recovery (iTR).

Abreviations: P cells, primary cells; S cells, secondary stem cells; T cells, tertiary stem cells; p-SRL, primary self renewing stem cell line (D1 cells); s-SRL, secondary self renewing stem cell lines (D1 cells); t-SRL, tertiary self renewing stem cell lines(D1 cells); D1, D2 cells, products of asymmetric cell division;iTR, induced totipotency recovery;

ATDcysts, cyclic encysted S cells (D2 cells) by autonomous terminal differentiation; ITD cysts, T cells induced to encyst in AaEM encystment medium; MAC, mitotic arrested cells (mitotic quiescent cells);OCB, oxygen consuming bacteria

* Revised version of the formerly manuscript “Ancient stem cells AnSC” registered byResearchgate on March 25, 2013; Views: 51; Downloads: 73