title: The Hippo pathway controls polar cell fate through Notch signaling during Drosophila oogenesis.
abstract: During Drosophila oogenesis, the somatic follicle cells form an epithelial layer surrounding the germline cells to form egg chambers. In this process, follicle cell precursors are specified into polar cells, stalk cells, and main-body follicle cells. Proper specification of these three cell types ensures correct egg chamber formation and polarization of the anterior-posterior axis of the germline cells. Multiple signaling cascades coordinate to control the follicle cell fate determination, including Notch, JAK/STAT, and Hedgehog signaling pathways. Here, we show that the Hippo pathway also participates in polar cell specification. Over-activation of yorkie (yki) leads to egg chamber fusion, possibly through attenuation of polar cell specification. Loss-of-function experiments using RNAi knockdown or generation of mutant clones by mitotic recombination demonstrates that reduction of yki expression promotes polar cell formation in a cell-autonomous manner. Consistently, polar cells mutant for hippo (hpo) or warts (wts) are not properly specified, leading to egg chamber fusion. Furthermore, Notch activity is increased in yki mutant cells and reduction of Notch activity suppresses polar cell formation in yki mutant clones. These results demonstrate that yki represses polar cell fate through Notch signaling. Collectively, our data reveal that the Hippo pathway controls polar cell specification. Through repressing Notch activity, Yki serves as a key repressor in specifying polar cells during Drosophila oogenesis.
authors.affiliation: Department of Life Sciences and Institute of Genome Sciences, National Yang-Ming University, Taipei 112, Taiwan.
authors.forename: Hsi-Ju
authors.initials: HJ
authors.lastname: Chen
authors.forename: Chi-Ming
authors.initials: CM
authors.lastname: Wang
authors.forename: Tsu-Wei
authors.initials: TW
authors.lastname: Wang
authors.forename: Gwo-Jen
authors.initials: GJ
authors.lastname: Liaw
authors.forename: Ta-Hsing
authors.initials: TH
authors.lastname: Hsu
authors.forename: Tzu-Huai
authors.initials: TH
authors.lastname: Lin
authors.forename: Jenn-Yah
authors.initials: JY
authors.lastname: Yu
mesh_terms: D000818:Animals; D002452:Cell Count; D002454:Cell Differentiation; D019070:Cell Lineage; D016764:Cell Polarity; D029721:Drosophila Proteins / Q000378:metabolism*; D004331:Drosophila melanogaster / Q000166:cytology*; D055785:Gene Knockdown Techniques; D047908:Intracellular Signaling Peptides and Proteins / Q000378:metabolism*; D009154:Mutation / Q000235:genetics; D009687:Nuclear Proteins / Q000378:metabolism; D009866:Oogenesis; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D051880:Receptors, Notch / Q000378:metabolism*; D015398:Signal Transduction; D015534:Trans-Activators / Q000378:metabolism; D000091102:YAP-Signaling Proteins; D000099317:Hippo Kinases
chemical_list: D029721:Drosophila Proteins; D047908:Intracellular Signaling Peptides and Proteins; D009687:Nuclear Proteins; D017346:Protein Serine-Threonine Kinases; D051880:Receptors, Notch; D015534:Trans-Activators; D000091102:YAP-Signaling Proteins; C497759:N protein, Drosophila; C503814:Yki protein, Drosophila; C499474:hpo protein, Drosophila; D000099317:Hippo Kinases