Abstract
Cell division consists of nuclear division (mitosis for somatic cells and meiosis for germ cells) and cytoplasmic division (cytokinesis). Embryonic developments are highly programmed, and thus, each cellular event during early embryo development is stable. For mouse embryos, the first time of mitosis is completed about 22 h after fertilization. However, it remains unclear when the embryo completes its first cytokinesis. Here, we microinjected only one cell in the 2-cell stage mouse embryos with mRNA, which encodes green fluorescence protein (GFP). By monitoring the GFP protein transport dynamics between the two cells, we demonstrated that the first time of cytokinesis in mouse embryos is completed about 15 h after mitosis, namely 37 h after fertilization. In addition, our results indicate that the cytoplasmic protein transport between daughter cells is very effective, which relies on microtubules instead of microfilaments in 2-cell mouse embryos. These results should enrich people’s understanding of the first cell division and cytoskeleton in mouse embryos and then learn more about the mechanisms of early embryo development in mammals.
Highlights
Cell division is the foundation of life
After 4 h of the mouse embryos divided into 2-cell stage, mRNA expressing green fluorescence protein (GFP) and mitochondrial localized red fluorescence proteins (RFP) were microinjected into any one of the daughter cells (Figure 1A)
The cytoplasmic GFP is evenly distributed in the two daughter cells, while the mitochondrial localized RFP only appeared in the daughter cell, which was injected with the mRNA. These results indicate that the intercellular bridge can transport the cytoplasmic localized proteins while not the organelles between the two daughter cells
Summary
Cell division is the foundation of life. Unicellular life directly utilizes it to produce offspring, and multicellular life utilizes it to generate new cells to grow bigger. Cell division usually consists of two steps. One is genome separation, which is called mitosis or meiosis, depending on somatic or germ cells. The other one is cytokinesis, which includes the separation of cytoplasm and other organelles, such as mitochondria, endoplasmic reticulum (ER), ribosomes, etc. People usually indicate mitosis or meiosis as the cell division, including nuclear and cytoplastic separation. Mitosis or meiosis only is the nuclear separation at first (Glotzer 2001; Eggert et al, 2006; Ruchaud et al, 2007), so we insist on this statement and distinguish them from cytokinesis in this study. Nuclear and cytoplastic separation is not strictly distinguished. Cytokinesis plays a vital role in cell proliferation and differentiation as the final step of cell division
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