The CPEB translational regulator, Orb, functions together with Par proteins to polarize the Drosophila oocyte

Abstract

orb is a founding member of the CPEB family of translational regulators and is required at multiple steps during Drosophila oogenesis. Previous studies showed that orb is required during mid-oogenesis for the translation of the posterior/germline determinant oskar mRNA and the dorsal-ventral determinant gurken mRNA. Here, we report that orb also functions upstream of these axes determinants in the polarization of the microtubule network (MT). Prior to oskar and gurken translational activation, the oocyte MT network is repolarized. The MT organizing center at the oocyte posterior is disassembled, and a new MT network is established at the oocyte anterior. Repolarization depends upon cross-regulatory interactions between anterior (apical) and posterior (basal) Par proteins. We show that repolarization of the oocyte also requires orb and that orb is needed for the proper functioning of the Par proteins. orb interacts genetically with aPKC and cdc42 and in egg chambers compromised for orb activity, Par-1 and aPKC protein and aPKC mRNA are mislocalized. Moreover, like cdc42-, the defects in Par protein localization appear to be connected to abnormalities in the cortical actin cytoskeleton. These abnormalities also disrupt the localization of the spectraplakin Shot and the microtubule minus-end binding protein Patronin. These two proteins play a critical role in the repolarization of the MT network.

The role of CPEB family proteins in the nervous system function in the norm and pathology

“…The functioning of the CPEB family proteins is essential at all stages of ontogeny. CPEBs play an important role in the formation and maintenance of cell polarity, participating in mRNA transport and localization, translational repression or activation of target mRNAs [ 30 , 81 – 83 ]. In the nervous system, this function is manifested in the participation of the CPEB proteins in neurogenesis and the functioning of neurons.…”

Atypical cadherin, Fat2, regulates axon terminal organization in the developing Drosophila olfactory receptor neurons

“…Based on the literature CG17528 and Apc play important roles in regulating actin and microtubule cytoskeleton, while dop encodes a kinase that regulates protein localization and transport. 52 , 53 , 54 , 55 , 56 , 57 , 58 , 59 , 60 , 61 , 62 , 63 , 64 , 65 , 66 If Fat2 intracellular domain indeed interacts with these proteins, we imagine that Fat2 gathers the appropriate cytoskeletal effectors to regulate the cytoskeletal framing of axon terminals and thus affect axon behavior. We further investigated whether any of these genes genetically interacted with fat2 by asking if reducing the dose of fat2 by half in the ORN-specific RNAi knockdown background enhanced or suppressed phenotypes observed ( Figures 7 A and 7B).…”

Mapping parameter spaces of biological switches

“…The process of oocyte selection within such clusters is one of the key unresolved questions in oogenesis [ 9 , 13 , 14 ]. Recent studies in Drosophila revealed that oocyte selection is foreshadowed by autoregulated accumulation of oocyte-specific mRNA and proteins [ 16 , 19 , 20 , 23 , 33 ]. Even the simplest models of molecular and cellular processes in early stages of animal oogenesis contain a large number of parameters.…”