pentachloropseudilin and blebbistatin

Myosin-1 (Myo1) represents a mechanical link between the membrane and actin-cytoskeleton in animal cells. We have studied the effect of Myo1 inhibitor PClP in 1-8 cell Zebrafish embryos. Our results indicate a unique involvement of Myo1 in early development of Zebrafish embryos. Inhibition of Myo1 (by PClP) and Myo2 (by Blebbistatin) lead to arrest in cell division. While Myo1 isoforms appears to be important for both the formation and the maintenance of cleavage furrows, Myo2 is required only for the formation of furrows. We found that the blastodisc of the embryo, which contains a thick actin cortex (~13 μm), is loaded with cortical Myo1. Myo1 appears to be crucial for maintaining the blastodisc morphology and the actin cortex thickness. In addition to cell division and furrow formation, inhibition of Myo1 has a drastic effect on the dynamics and distribution of lipid droplets (LDs) in the blastodisc near the cleavage furrow. All these results above are effects of Myo1 inhibition exclusively; Myo2 inhibition by blebbistatin does not show such phenotypes. Therefore, our results demonstrate a potential role for Myo1 in the maintenance and formation of furrow, blastodisc morphology, cell-division and LD organization within the blastodisc during early embryogenesis.

Topics: Actin Cytoskeleton; Actins; Animals; Blastomeres; Blotting, Western; Cell Division; Cell Membrane; Embryo, Nonmammalian; Gene Expression Regulation, Developmental; Heterocyclic Compounds, 4 or More Rings; Hydrocarbons, Chlorinated; Lipid Droplets; Microscopy, Electron, Scanning; Microscopy, Fluorescence; Myosin Heavy Chains; Pyrroles; Reverse Transcriptase Polymerase Chain Reaction; Zebrafish; Zebrafish Proteins

Primitive streak formation in the chick embryo involves large-scale highly coordinated flows of more than 100,000 cells in the epiblast. These large-scale tissue flows and deformations can be correlated with specific anisotropic cell behaviours in the forming mesendoderm through a combination of light-sheet microscopy and computational analysis. Relevant behaviours include apical contraction, elongation along the apical-basal axis followed by ingression, and asynchronous directional cell intercalation of small groups of mesendoderm cells. Cell intercalation is associated with sequential, directional contraction of apical junctions, the onset, localization and direction of which correlate strongly with the appearance of active myosin II cables in aligned apical junctions in neighbouring cells. Use of class specific myosin inhibitors and gene-specific knockdown shows that apical contraction and intercalation are myosin II dependent and also reveal critical roles for myosin I and myosin V family members in the assembly of junctional myosin II cables.

Topics: Animals; Animals, Genetically Modified; Cell Line; Cell Movement; Cell Proliferation; Cell Shape; Chick Embryo; Chickens; Gastrulation; HEK293 Cells; Heterocyclic Compounds, 4 or More Rings; Humans; Hydrocarbons, Chlorinated; Myosin Type I; Myosin Type II; Myosin Type V; Phosphorylation; Primitive Streak; Pyrroles; RNA Interference; RNA, Small Interfering