Imaging filopodia dynamics in the mouse blastocyst

Abstract

During mammalian development, the first cell lineage diversification event occurs in the blastocyst, when the trophectoderm (TE) and the inner cell mass (ICM) become established. Part of the TE (polar) remains in contact with the ICM and differs from the mural TE (mTE) which is separated from the ICM by a cavity known as the blastocoele. The presence of filopodia connecting ICM cells with the distant mural TE cells through the blastocoelic fluid was investigated in this work. We describe two types of actin-based cell projections found in freshly dissected and in vitro cultured expanding blastocysts: abundant short filopodia projecting into the blastocoelic cavity that present a continuous undulating behavior; and long, thin traversing filopodia connecting the mural TE with the ICM. Videomicroscopy analyses revealed the presence of vesicle-like structures moving along traversing filopodia and dynamic cytoskeletal rearrangements. These observations, together with immunolocalization of the FGFR2 and the ErbB3 receptors to these cell extensions, suggest that they display signal transduction activity. We propose that traversing filopodia are employed by mitotic mTE cells to receive the required signals for cell division after they become distant to the ICM.

Membrane dynamics of cleavage furrow closure in Xenopus laevis

“…The motile protrusions we report are reminiscent of the filopodia that traverse the blastocoel in early cleaving sea urchin embryos (Vacquier, 1968), sea urchin blastulae Wolpert, 1962, 1967), and mouse blastocysts (Salas-Vidal and Lomeli, 2004), and suggest that a lot of unseen protrusive activity occurs along the walls of the nascent blastocoel. Whether protrusions there function exclusively in morphogenetic activities, e.g., by stabilizing blastomere-blastomere adhesion, or act as cell-signaling agents as proposed for cytonemes (Bryant, 1999) remains to be ascertained.…”

Regulatory microRNA Network Identification in Bovine Blastocyst Development

“…The only reports regarding cell projections in mammalian blastocysts mention trophectodermal pseudopodia in the blastocoelic cavity connecting the mural TE with the ICM [54]. These pseudopodia have later been characterized as parietal endoderm cells moving from the surface of the ICM facing the blastocoel cavity to line the inner surface of the TE [55].…”

Wiring through tunneling nanotubes – from electrical signals to organelle transfer

“…However, the fragility of TNTs and the lack of known molecular markers make it very difficult to observe these structures in their natural environment within tissues. Nevertheless, several studies indicate the presence of TNT-like bridges in vivo during certain developmental processes, such as blastocyst formation and neurulation in mice (Pyrgaki et al, 2010;Salas-Vidal and Lomeli, 2004), dorsal closure in Drosophila (Millard and Martin, 2008) and gastrulation in sea urchin (Miller et al, 1995) and zebrafish (Caneparo et al, 2011). TNTs were also found connecting dendritic cells in mouse cornea (Chinnery et al, 2008) and in other organisms, such as the malaria parasite Plasmodium falciparum (Rupp et al, 2011) and the bacterium Bacillus subtilis (Dubey and Ben-Yehuda, 2011).…”