Lipid droplets are formed in 2-cell-like cells

Abstract

Embryonic stem (ES) cells, derived from the inner cell mass of a blastocyst, are believed to pluripotent cells and give rise to embryonic, but not extraembryonic, tissues. In mice, totipotent 2-cell stage embryo-like (2-cell-like) cells, which are identified by reactivation of murine endogenous retrovirus with leucin transfer RNA primer (MuERV-L), arise at a very few frequencies in ES cell cultures. Here, we found that a lipid droplet forms during the transition from ES cells to 2-cell-like cells, and we propose that 2-cell-like cells utilize a unique energy storage and production pathway.

Keywords: 2-cell-like cells; Lipid droplet; MuERV-L positive cells.

Fig. 1.

The lipid droplet (LD)-like organelles in MuERV-L-positive cells. (A) Electron microscopic images of MuERV-L-positive, -negative ES cells, and 2-cell embryo. The right panel shows higher-magnification images of the boxed area. (B) Percentage of LD-like organelles in MuERV-L-positive (n = 13) and -negative (n = 13) ES cells. The scale bars of the MuERV-L(–) and (+) cells are 2.5 μm, while that of the 2-cell embryo is 20 μm.

Fig. 2.

Lipid droplets (LDs) in MuERV-L-positive cells. (A) Two-cell embryo was stained with BODIPY 493/503 (green) and observed by confocal fluorescence microscopy. (B) MuERV-L-positive and -negative ES cells were stained with BODIPY 493/503 and observed by confocal fluorescence microscopy. MuERV-L expression was detected by the fluorescence of tdTomato (red) and LDs stained by BODIPY 493/503 (green); nuclei were stained with DAPI (blue). (C) The percentages of BODIPY 493/503-positive LDs in MuERV-L-positive (n = 11) and -negative (n = 13) ES cells. Scale bars: 10 μm.