Date Published: July 5, 2017
Publisher: Public Library of Science
Author(s): Prabuddha Gupta, René Martin, Hans-Joachim Knölker, Deepak Nihalani, Deepak Kumar Sinha, Miklos S. Kellermayer.
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.
Myo1 proteins are ATP-driven actin-bound motor proteins that are commonly monomeric (single headed) in nature, unlike dimeric Myosin II (Myo2) molecules . Myo1 isoforms associate with cell membrane by the Tail Homology 1 (TH1) domain that contains a lipid-binding, PH like domain [2, 3]. Myo1 proteins are further classified as short tailed (eg 1B/1C/1D) or long tailed (eg 1E/1F) based on the absence or presence of glycine/proline/alanine rich (TH2) and SH3 domains (TH3) in the tail region (Fig 1A) . Collectively, Myo1 isoforms help in mechanical regulation of membrane architecture by coupling it with actin cytoskeleton [4, 5]. Various Myo1 isoforms have specialized functions [6, 7]. The common theme behind Myo1 function is that they are activated in the presence of F-actin, near membranous structures, eg in membrane-cytoskelatal adhesion, during microvilli vesicle shedding, endo-exocytosis, lipid raft transport and sensory channel gating/adaptation [4, 8].