Nuclear positioning by actin cables and perinuclear actin: Special and general?

Abstract

Nuclear positioning is an important process during development and homeostasis. Depending on the affected tissue, mislocalized nuclei can alter cellular processes such as polarization, differentiation, or migration and lead ultimately to diseases. Many cells actively control the position of their nucleus using their cytoskeleton and motor proteins. We have recently shown that during Drosophila oogenesis, nurse cells employ cytoplasmic actin cables in association with perinuclear actin to position their nucleus. Here, we briefly summarize our work and discuss why nuclear positioning in nurse cells is specialized but the molecular mechanisms are likely to be more generally used.

Keywords: Drosophila; LINC complex; actin cables; dumping; filamin; nuclear positioning; nurse cells; perinuclear actin.

Figure 1. Nuclear positioning in Drosophila nurse cells. Nuclear positioning is essential during oogenesis for the development of layed eggs (above). Before dumping (until stage 10A), the round nurse cell nuclei have perinuclear actin, to which filamin localizes. At stage 10B filopodia-like actin cables in association with perinuclear actin position nuclei toward the outside, away from the ring canals. Filamin localizes to the perinuclear ends of actin cables. Dumping, a process in which nurse cells expel their content into the oocyte (orange arrow), starts at the same time. The continuous contraction of nurse cells leads to nuclei turning in order to accommodate the long actin cables in the shrinking cells (here shown at stage 12). The middle row shows egg chambers of the mentioned stages, each egg chamber with one nurse cell marked by a blue nucleus. Zooms into these marked nurse cells are shown in the row below (nc, nurse cell; oc, oocyte; A, anterior; P, posterior; D, dorsal; V, ventral).