Microtubules and Lis-1/NudE/Dynein Regulate Invasive Cell-on-Cell Migration in Drosophila

Abstract

The environment through which cells migrate in vivo differs considerably from the in vitro environment where cell migration is often studied. In vivo many cells migrate in crowded and complex 3-dimensional tissues and may use other cells as the substratum on which they move. This includes neurons, glia and their progenitors in the brain. Here we use a Drosophila model of invasive, collective migration in a cellular environment to investigate the roles of microtubules and microtubule regulators in this type of cell movement. Border cells are of epithelial origin and have no visible microtubule organizing center (MTOC). Interestingly, microtubule plus-end growth was biased away from the leading edge. General perturbation of the microtubule cytoskeleton and analysis by live imaging showed that microtubules in both the migrating cells and the substrate cells affect movement. Also, whole-tissue and cell autonomous deletion of the microtubule regulator Stathmin had distinct effects. A screen of 67 genes encoding microtubule interacting proteins uncovered cell autonomous requirements for Lis-1, NudE and Dynein in border cell migration. Net cluster migration was decreased, with initiation of migration and formation of dominant front cell protrusion being most dramatically affected. Organization of cells within the cluster and localization of cell-cell adhesion molecules were also abnormal. Given the established role of Lis-1 in migrating neurons, this could indicate a general role of Lis-1/NudE, Dynein and microtubules, in cell-on-cell migration. Spatial regulation of cell-cell adhesion may be a common theme, consistent with observing both cell autonomous and non-autonomous requirements in both systems.

The Hippo Pathway Controls Border Cell Migration Through Distinct Mechanisms in Outer Border Cells and Polar Cells of the Drosophila Ovary

“…We did find strong migratory defects when we overexpressed hpo with slbo-Gal4, suggesting that the slbo-Gal4 driver indeed promoted transgene expression efficiently in outer border cells. Therefore, it is likely that driving RNAi with slbo-Gal4 may not efficiently knock down genes prior to or during border cell migration in outer border cells when the target protein is stable (Yang et al 2012).…”

asunder is required for dynein localization and dorsal fate determination during Drosophila oogenesis

“…In addition to the functions reported for dynein within the germ cells, two major functions have been identified for dynein within the somatic follicle cells: dynein is required for the normal polarization of the epithelial follicle cells as well as for the normal migration of the border cells (Horne-Badovinac and Bilder, 2008; Van de Bor et al, 2011; Yang et al, 2012). To determine if ASUN is required for dynein functions within the follicle cells, we assessed whether asun d93 egg chambers exhibited defects in these processes.…”

“…Additionally, dynein is critical for the transport and normal localizations of various patterning factors throughout oogenesis as well as maintenance of the anterior-dorsal positioning of the oocyte nucleus in late-stage egg chambers (Clark et al, 2007; Duncan and Warrior, 2002; Januschke et al, 2002; Lan et al, 2010; Lei and Warrior, 2000; Rom et al, 2007; Swan et al, 1999). Within the somatic follicle cells, dynein plays a role in maintaining apical-basal polarity as well as in the migration of border cells (Horne-Badovinac and Bilder, 2008; Van de Bor et al, 2011; Yang et al, 2012). …”

“…During Drosophila oogenesis, dynein is required within the germ cells for maintenance of fusome integrity, centrosome migration, oocyte determination, migration of the oocyte nucleus, transport into the oocyte of various mRNAs and proteins that play critical roles in axis determination of the embryo, and localization of these mRNAs and proteins within the oocyte (Bolivar et al, 2001; Januschke et al, 2002; Lei and Warrior, 2000; McGrail and Hays, 1997; Schnorrer et al, 2000; Swan et al, 1999). Dynein is also important within the somatic follicle cells for maintenance of their apical-basal polarity as well as for the migration of the border cells from the anterior of the egg chamber to the anterior of the oocyte (Horne-Badovinac and Bilder, 2008; Van de Bor et al, 2011; Yang et al, 2012). …”

Nuclear positioning by actin cables and perinuclear actin

“…Before dumping, nurse cells nuclei are highly polyploid (1024C), 31 relative round, and dynamic with their "wriggling" mobility depending on microtubules. 32 When nurse cells build their actin cables and dumping starts, their nuclei stop moving and are multilobed, indicating a lower stiffness of the nuclear envelope. Shortly after that, or at the same time, nurse cells initiate a cell death program that involves so far unknown molecular mechanisms.…”