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Published on: March 15, 2019
Multi-modal comparison of molecular programs driving nurse cell death and clearance in Drosophila melanogaster
Shruthi Bandyadka1,2, Diane P V Lebo2, Albert A Mondragon2,3
1Graduate Program in Bioinformatics, Boston University, Boston Massachusetts, United States of America.
Abstract:
The death and clearance of nurse cells is a consequential milestone in Drosophila melanogaster oogenesis. In preparation for oviposition, the germline-derived nurse cells bequeath to the developing oocyte all their cytoplasmic contents and undergo programmed cell death. The death of the nurse cells is controlled non-autonomously and is precipitated by epithelial follicle cells of somatic origin acquiring a squamous morphology and acidifying the nurse cells externally. Alternatively, stressors such as starvation can induce the death of nurse cells earlier in mid-oogenesis, manifesting apoptosis signatures, followed by their engulfment by epithelial follicle cells. To identify and contrast the molecular pathways underlying these morphologically and genetically distinct cell death paradigms, both mediated by follicle cells, we compared their genome-wide transcriptional, translational, and secretion profiles before and after differentiating to acquire a phagocytic capability, as well as during well-fed and nutrient-deprived conditions. By coupling the GAL4-UAS system to Translating Ribosome Affinity Purification (TRAP-seq) and proximity labeling (HRP-KDEL) followed by Liquid Chromatography tandem mass-spectrometry, we performed high-throughput screens to identify pathways selectively activated or repressed by follicle cells to employ nurse cell-clearance routines. We also integrated two publicly available single-cell RNAseq atlases of the Drosophila ovary to define the transcriptomic profiles of follicle cells. In this report, we describe the genes and major pathways identified in the screens and the striking consequences to Drosophila melanogaster oogenesis caused by RNAi perturbation of prioritized candidates. To our knowledge, our study is the first of its kind to comprehensively characterize two distinct apoptotic and non-apoptotic cell death paradigms in the same multi-cellular system. Beyond molecular differences in cell death, our investigation may also provide insights into how key systemic trade-offs are made between survival and reproduction when faced with physiological stress.
Insights
Nurse cell death in Drosophila oogenesis involves two distinct pathways mediated by follicle cells. This study identifies the molecular mechanisms underlying these processes, offering insights into reproduction and survival trade-offs during stress.
Area of Science:
- Developmental Biology
- Cell Biology
- Genetics
Background:
- Nurse cell death is crucial for Drosophila oogenesis, preparing for oviposition.
- Two distinct nurse cell death paradigms exist: one triggered by follicle cell differentiation and another by stressors like starvation.
Purpose of the Study:
- To identify and contrast the molecular pathways governing two distinct nurse cell death paradigms in Drosophila.
- To investigate the roles of follicle cells in mediating nurse cell clearance.
Main Methods:
- Genome-wide transcriptional, translational, and secretion profiling.
- Translating Ribosome Affinity Purification (TRAP-seq) and proximity labeling (HRP-KDEL) coupled with mass spectrometry.
- Integration of single-cell RNA sequencing atlases of the Drosophila ovary.
Main Results:
- Identification of specific genes and molecular pathways activated or repressed by follicle cells during nurse cell clearance.
- Characterization of distinct molecular signatures for apoptotic and non-apoptotic nurse cell death.
- Demonstration of significant consequences of RNAi perturbation of key candidate genes on oogenesis.
Conclusions:
- This study provides the first comprehensive molecular characterization of two distinct cell death paradigms in a multicellular system.
- Findings offer insights into the molecular basis of nurse cell clearance and potential trade-offs between reproduction and survival under stress.
