Somatic Cell Encystment Promotes Abscission in Germline Stem Cells following a Regulated Block in Cytokinesis

Abstract

SUMMARY In many tissues the stem cell niche must coordinate behavior across multiple stem cell lineages. How this is achieved is largely unknown. We have identified delayed completion of cytokinesis in germline stem cells (GSCs) as a mechanism that regulates the production of stem cell daughters in the Drosophila testis. Through live imaging, we show that a secondary F-actin ring is formed through regulation of Cofilin activity to block cytokinesis progress after contractile ring disassembly. The duration of this block is controlled by Aurora B kinase. Additionally, we have identified a requirement for somatic cell encystment of the germline in promoting GSC abscission. We suggest that this non-autonomous role promotes coordination between stem cell lineages. These findings reveal the mechanisms by which cytokinesis is inhibited and reinitiated in GSCs and why such complex regulation exists within the stem cell niche.

Neural Stem Cells to Cerebral Cortex: Emerging Mechanisms Regulating Progenitor Behavior and Productivity

“…Overall, a direct relationship between cleavage orientation and fate determination remains unclear. Moreover, inheritance of additional asymmetric factors aside from the apical membrane, such as the mother centrosome Paridaen et al, 2013), the basal process (Tsunekawa et al, 2012), or the midbody (Ettinger et al, 2011;Kuo et al, 2011) have been reported to influence fate specification.…”

“…Cleavage is often approximately perpendicular to the apical membrane (Noctor et al, 2008). A prevailing hypothesis holds that asymmetric neurogenic divisions result from unequal inheritance of apical membrane or junctions due to unequal cleavage of the apical membrane (Kosodo et al, 2004;Marthiens and ffrenchConstant, 2009). This is analogous to Drosophila neuroblasts, where a 90-degree change in cleavage angle determines whether one or both daughters inherit the apical membrane (Rhyu et al, 1994;Chenn and McConnell, 1995).…”

“…The cleavage furrow ingresses from the basal side toward the apical membrane. The furrow may split the basal process in two (Kosodo et al, 2008), or form next to it, segregating it to one daughter cell . Cleavage is often approximately perpendicular to the apical membrane (Noctor et al, 2008).…”

“…If this model is correct, then a truly symmetric division requires exquisite coordination of spindle orientation, furrow ingression, and abscission with distribution of apical domain components. The model was revised when cleavage angle failed to always predict daughter fate (Noctor et al, 2008), and mutations that cause irregular cleavage angles affect cortical thickness in some mutants (Postiglione et al, 2011), but not others (Konno et al, 2008). Interestingly, oblique cleavages that segregate the apical endfoot to only one daughter may serve to expand outer RGCs in the primate cortex (LaMonica et al, 2013).…”

“…Concurrently, APs begin to express glial markers but maintain their polarized, radial morphology with apical endfoot in, and the tip of their basal process out; hence their alternative name radial glial cells (RGCs). Cell divisions still occur at the VZ surface; however, the neuronal daughters detach or "delaminate" from the apical membrane to migrate out of the VZ to form the first neuronal layer, the preplate Haubensak et al, 2004). Beginning a few days later, some of the daughters of asymmetric divisions adopt an intermediate progenitor (IP) identity.…”