Germ Plasm Anchoring Is a Dynamic State that Requires Persistent Trafficking

Abstract

Summary Localized cytoplasmic determinants packaged as ribonucleoprotein (RNP) particles direct embryonic patterning and cell fate specification in a wide range of organisms. Once established, the asymmetric distributions of such RNP particles must be maintained, often over considerable developmental time. A striking example is the Drosophila germ plasm, which contains RNP particles whose localization to the posterior of the egg during oogenesis results in their asymmetric inheritance and segregation of germline from somatic fates in the embryo. Although actin-based anchoring mechanisms have been implicated, high-resolution live imaging revealed persistent trafficking of germ plasm RNP particles at the posterior cortex of the Drosophila oocyte. This motility relies on newly-identified cortical microtubules, is mediated by kinesin and dynein motors, and requires coordination between the microtubule and actin cytoskeletons. Finally, we show that RNP particle motility is required for long-term germ plasm retention. We propose that anchoring is a dynamic state that renders asymmetries robust to developmental time and environmental perturbations.

Somatic insulin signaling regulates a germline starvation response in Drosophila egg chambers

“…In S2 cells, disruption of Khc results in large parallel arrays of MTs, which is similar to the reorganization we observe in starved and Khc knockdown egg chambers. Dynein and Kinesin motors have also been shown to mediate MT function in mRNP trafficking and maintenance in the germ plasm (Sinsimer et al, 2013). Furthermore, Kinesin and Dynein are known to act antagonistically in the control of ooplasmic streaming in stage 10A–10B egg chambers, as Dynein inhibition allows premature Kinesin-driven fast streaming (Serbus et al, 2005).…”

Oyster reproduction is affected by exposure to polystyrene microplastics

“…Transcripts coding for proteins involved in Ca 2+ binding may have affected the Ca 2+ signaling pathway in exposed oocytes, thus affecting oocyte maturation (39). Severin is a Ca 2+ -dependent actin-binding protein regulating the completion of cell division (40); its up-regulation may reflect a deleterious effect of micro-PS on cytoskeletal dynamics, which are essential during oocyte maturation, fertilization, and subsequent embryo development (41). Other candidates, down-regulated in exposed oocytes, also indicate potential impairment of embryo development: transcripts in the categories of embryogenesis, cell differentiation, and proliferation, and the arginine kinase protein, responsible in invertebrates for ATP buffering on phosphagens, which are essential for embryo biosynthetic activities (42).…”

mRNA localization in theDrosophilagermline

“…23 At the posterior, the actin cytoskeleton, the actin binding proteins Lasp, Didum, Spire, Cappuccino, the Myosin-V motor, MTs and Dynein are all required for proper posterior accumulation and maintenance. [69][70][71][72][73][74][75] The involvement of both kinesin and Dynein in osk mRNA localization suggests that RNP particles are exposed to opposing directional forces during localization. How particles in vivo transition between plus and minus end movement remains unclear and an aim for future research.…”

“…88 For long-term maintenance of the germ plasm, live imaging shows that Kinesin, Dynein and cortical MTs are required for germ plasm RNP, containing nos mRNA, motility which is coordinated with Myosin V mediated tethering. 75 This multiple mechanism model stresses the importance of restricting mRNA to the correct cellular position for extended periods of time.…”