Dynamic organelle localization and cytoskeletal reorganization during preimplantation mouse embryo development revealed by live imaging of genetically encoded fluorescent fusion proteins

Abstract

Summary Live imaging is one of the most powerful technologies for studying the behaviors of cells and molecules in living embryos. Previously, we established a series of reporter mouse lines in which specific organelles are labeled with various fluorescent proteins. In this study, we examined the localizations of fluorescent signals during preimplantation development of these mouse lines, as well as a newly established one, by time‐lapse imaging. Each organelle was specifically marked with fluorescent fusion proteins; fluorescent signals were clearly visible during the whole period of time‐lapse observation, and the expression of the reporters did not affect embryonic development. We found that some organelles dramatically change their sub‐cellular distributions during preimplantation stages. In addition, by crossing mouse lines carrying reporters of two distinct colors, we could simultaneously visualize two types of organelles. These results confirm that our reporter mouse lines can be valuable genetic tools for live imaging of embryonic development.

Evolution of the ribbon-like organization of the Golgi apparatus in animal cells

“…Indeed, we observed Golgi stack clustering and ribbon-like formation during development in cells of two non-vertebrate chordates, the sea squirt Ciona robusta (tunicate) and the lancelet Branchiostoma lanceolatum (cephalochordate) (Figure 1E and 1F). As Golgi centralization also occurs in mammalian early embryos 27 , our observations not only show that it is a conserved feature across deuterostomes, but also suggest that it might play a role during the initial stages of their development. Our findings also raise the intriguing possibility that Golgi centralization may have evolved before the split between deuterostomes and other animal groups.…”

“…As the biological roles of the ribbon remain unclear, we can only speculate. In deuterostomes, Golgi centralization occurs in early embryogenesis (this report and reference 27 ). This may indicate that the primordial function of the ribbon-like architecture could have been in development, explaining why some differentiated mammalian tissues can forgo Golgi ribbons [28][29][30] .…”

The transition from local to global patterns governs the differentiation of mouse blastocysts

“…However, transcriptomic techniques disrupt the cell positional information within the ICM [8,9,11,18,19]. A complementary approach is single cell resolution imaging based on immunofluorescence stainings [4][5][6]9,13,[20][21][22] or fluorescent reporters [10,[23][24][25][26][27][28][29][30][31][32]. Combined with quantitative image analysis, the immunofluorescence approach provides protein expression levels together with cell positional information.…”

The ribbon architecture of the Golgi apparatus is not restricted to vertebrates

“…Interestingly, Golgi ribbon formation in early embryos is observed also in mammals. In mouse blastomeres, the Golgi is formed by separate elements, likely mini-stacks, that cluster by the blastocyst stage 46 . Formation of the Golgi ribbon in embryonic cells thus occurs at early developmental stages in both sea urchins and mammals and may indicate that this centralized Golgi organization plays a role during embryogenesis.…”