title: Endophilin B is required for the Drosophila oocyte to endocytose yolk downstream of Oskar.
abstract: The nutritional environment is crucial for Drosophila oogenesis in terms of controlling hormonal conditions that regulate yolk production and the progress of vitellogenesis. Here, we discovered that Drosophila Endophilin B (D-EndoB), a member of the endophilin family, is required for yolk endocytosis as it regulates membrane dynamics in developing egg chambers. Loss of D-EndoB leads to yolk content reduction, similar to that seen in yolkless mutants, and also causes poor fecundity. In addition, mutant egg chambers exhibit an arrest at the previtellogenic stage. D-EndoB displayed a crescent localization at the oocyte posterior pole in an Oskar-dependent manner; however, it did not contribute to pole plasm assembly. D-EndoB was found to partially colocalize with Long Oskar and Yolkless at the endocytic membranes in ultrastructure analysis. Using an FM4-64 dye incorporation assay, D-EndoB was also found to promote endocytosis in the oocyte. When expressing the full-length D-endoB(FL) or D-endoB(ΔSH3) mutant transgenes in oocytes, the blockage of vitellogenesis and the defect in fecundity in D-endoB mutants was restored. By contrast, a truncated N-BAR domain of the D-EndoB only partially rescued these defects. Taken together, these results allow us to conclude that D-EndoB contributes to the endocytic activity downstream of Oskar by facilitating membrane dynamics through its N-BAR domain in the yolk uptake process, thereby leading to normal progression of vitellogenesis.
authors.affiliation: Graduate Institute of Biomedical Sciences, College of Medicine, Chang Gung University, Tao-Yuan, 333, Taiwan.
authors.forename: Yi-Cheng
authors.initials: YC
authors.lastname: Tsai
authors.forename: Wei
authors.initials: W
authors.lastname: Chiang
authors.forename: Willisa
authors.initials: W
authors.lastname: Liou
authors.forename: Wei-Hao
authors.initials: WH
authors.lastname: Lee
authors.forename: Yu-Wei
authors.initials: YW
authors.lastname: Chang
authors.forename: Pei-Yu
authors.initials: PY
authors.lastname: Wang
authors.forename: Yi-Chen
authors.initials: YC
authors.lastname: Li
authors.forename: Tsubasa
authors.initials: T
authors.lastname: Tanaka
authors.forename: Akira
authors.initials: A
authors.lastname: Nakamura
authors.forename: Li-Mei
authors.initials: LM
authors.lastname: Pai
mesh_terms: D000217:Acyltransferases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D002462:Cell Membrane / Q000378:metabolism; D016764:Cell Polarity / Q000235:genetics; D053487:DEAD-box RNA Helicases / Q000378:metabolism; D029721:Drosophila Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D004331:Drosophila melanogaster / Q000166:cytology* / Q000235:genetics / Q000378:metabolism* / Q000648:ultrastructure; D004530:Egg Yolk / Q000166:cytology* / Q000378:metabolism; D004705:Endocytosis; D005260:Female; D005298:Fertility / Q000235:genetics; D020869:Gene Expression Profiling; D009154:Mutation / Q000235:genetics; D009865:Oocytes / Q000166:cytology* / Q000378:metabolism / Q000648:ultrastructure; D020033:Protein Isoforms / Q000378:metabolism; D017434:Protein Structure, Tertiary; D021381:Protein Transport; D015398:Signal Transduction / Q000235:genetics
chemical_list: D029721:Drosophila Proteins; D020033:Protein Isoforms; C091675:osk protein, Drosophila; D000217:Acyltransferases; C587140:endophilin B, Drosophila; C088269:vas protein, Drosophila; D053487:DEAD-box RNA Helicases
keywords: Drosophila; Endophilin B; Fecundity; Oskar; Vitellogenesis; Yolk protein