Figure 3 : The stem cell lineage (life cycle) of E. invadens.

M, metacyst (hatched innercyst cell), A amoebulae of the first and second generation. Green
represents the moderate hypoxic stage in the life cycle (MH), yellow the most oxygenic stage
(MO) and red the strong hypoxic stage (SH) of the stem cell lineage as observed in MH, MO
and SH culture conditions (OCB niches). The life cycle of E. invadens consists of three self
renewing stem cell lines: the primary line p-SRL, the secondary line s-SRL and the tertiary line
t-SRL. Each stem cell line that consists of cycling cells (D1 cells) produces differentiated/
quiescent D2 cells (mitotic arrested cells, MA cells). Primary MAP cells and tertiary MAT cells
are reversible differentiated cells capable of cell cycle reentry. MAS cells are irreversibly
committed to endopolyploidization and oxygenic terminal differentiation (ATD cysts). MAT cells
are long living quiescent cells capable of producing ITD cysts, when induced in strong hypoxic/
hypoosmotic, non-nutrient media. P/S and P/T are alternative conversion events that depend
on the pO2 value of the niche. S/T conversion occured when the MO niche become less
oxygenic. Checkpoints (switching points): (I) switching point for asymmetric proliferation; (II)
checkpoint for RSC reactivation and cell cycle re-entry; (III) switching point for fast or slow
cycling; (IV) checkpoint for symmetric cell fate; (V) checkpoint for T cell return. RSC, reserve
stem cells, ATD oxygenic terminal differentiation producing ATD cysts, ITD, more hypoxic
terminal differentiation producing ITD cysts.

Vladimir F Niculescu Stem Cell Biology and Research  2015 2:2DOI : 10.7243/2054-717X-2-2