Quantitative proteomics reveals the dynamics of protein changes during Drosophila oocyte maturation and the oocyte-to-embryo transition

Abstract

The onset of development is marked by two major, posttranscriptionally controlled, events: oocyte maturation (release of the prophase I primary arrest) and egg activation (release from the secondary meiotic arrest). Using quantitative mass spectrometry, we previously described proteome remodeling during Drosophila egg activation. Here, we describe our quantitative mass spectrometry-based analysis of the changes in protein levels during Drosophila oocyte maturation. This study presents the first quantitative survey, to our knowledge, of proteome changes accompanying oocyte maturation in any organism and provides a powerful resource for identifying both key regulators and biological processes driving this critical developmental window. We show that Muskelin, found to be up-regulated during oocyte maturation, is required for timely nurse cell nuclei clearing from mature egg chambers. Other proteins up-regulated at maturation are factors needed not only for late oogenesis but also completion of meiosis and early embryogenesis. Interestingly, the down-regulated proteins are predominantly involved in RNA processing, translation, and RNAi. Integrating datasets on the proteome changes at oocyte maturation and egg activation uncovers dynamics in proteome remodeling during the change from oocyte to embryo. Notably, 66 proteins likely act uniquely during late oogenesis, because they are up-regulated at maturation and down-regulated at activation. We find down-regulation of this class of proteins to be mediated partially by APC/C CORT , a meiosis-specific form of the E3 ligase anaphase promoting complex/ cyclosome (APC/C).he change from oocyte to embryo marks the onset of development. Oocyte maturation is a prerequisite for the oocyte-toembryo transition. In most animals, oocytes undergo a prolonged arrest in prophase I to permit oocyte growth, differentiation, and stockpiling of maternal components. This arrest is released at oocyte maturation, commonly in response to hormonal cues. The nuclear envelope then breaks down, followed by assembly of the meiotic spindle. A secondary meiotic arrest ensues, occurring at metaphase II in most vertebrates and metaphase I in insects (1). The oocyte-to-embryo transition initiates with egg activation, which causes the release of the secondary arrest and the completion of meiosis. In many organisms, egg activation requires fertilization, but egg activation is independent of fertilization in Drosophila (1). In all cases, the onset of embryogenesis requires sperm entry, fusion of the male and female pronuclei, and the start of the mitotic embryonic divisions.How is this complex transition from differentiated oocyte into totipotent embryo regulated? Both oocyte maturation and egg activation occur in a transcriptionally silent context (2-4). These events are thus posttranscriptionally controlled, and translational regulation has been shown to play a crucial role. For example, resumption of meiosis in Xenopus depends on translational activation of cyclin B and mos mRNA by CPEB-mediated polyad...

Prolonged ovarian storage of matureDrosophilaoocytes dramatically increases meiotic spindle instability

“…These studies were consistent with previous analyses of gene expression during late oogenesis and oocyte maturation and showing large increases to genes involved in cell cycle control (Cui et al, 2013;Kronja et al, 2014b;Sieber and Spradling, 2015;Tootle et al, 2011). RNA level changes analyzed by gene ontology reflect completion of follicle growth, nurse cell dumping, reactivation of oocyte meiotic progression from diplotene to a new arrest in metaphase I, and reduced ribosomal production ( Fig.…”

The developmental proteome of Drosophila melanogaster

“…In contrast, proteomic studies in Drosophila have been restricted to certain developmental stages. For example, changes in the proteome during aging from eclosure to 60-d-old flies (Sowell et al 2007), the adult itself (Sury et al 2010;Xing et al 2014), larva and pupa (Chang et al 2013), the embryo (Fabre et al 2016), and the oocyte-to-embryo transition (Kronja et al 2014) have been investigated. However, these studies have relatively low proteome coverage (around 2000 proteins), do not cover the complete developmental process, and are not directly comparable because of technical differences.…”

APC/CFzr/Cdh1-Dependent Regulation of Planar Cell Polarity Establishment via Nek2 Kinase Acting on Dishevelled

“…During meiosis, its co-activator is Cortex (Kronja et al, 2014; Pesin and Orr-Weaver, 2007), and in mitotic cell cycle progression Cdc20 is the activating subunit (rev. in Pines, 2011).…”