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De Renzis GroupPublications

Plasma membrane phosphoinositide balance regulates cell shape during Drosophila embryo morphogenesis.
Reversi, A., Loeser, E., Subramanian, D., Schultz, C. & De Renzis, S.
J Cell Biol. 2014 May 12;205(3):395-408. doi: 10.1083/jcb.201309079. Epub 2014May 5.
Remodeling of cell shape during morphogenesis is driven by the coordinated expansion and contraction of specific plasma membrane domains. Loss of this coordination results in abnormal cell shape and embryonic lethality. Here, we show that plasma membrane lipid composition plays a key role in coordinating plasma membrane contraction during expansion. We found that an increase in PI(4,5)P2 levels caused premature actomyosin contraction, resulting in the formation of shortened cells. Conversely, acute depletion of PI(4,5)P2 blocked plasma membrane expansion and led to premature actomyosin disassembly. PI(4,5)P2-mediated contractility is counteracted by PI(3,4,5)P3 and the zygotic gene bottleneck, which acts by limiting myosin recruitment during plasma membrane expansion. Collectively, these data support a model in which the ratio of PI(4,5)P2/PI(3,4,5)P3 coordinates actomyosin contractility and plasma membrane expansion during tissue morphogenesis, thus ensuring proper cell shape.
Europe PMC

Tubular endocytosis drives remodelling of the apical surface during epithelial morphogenesis in Drosophila.
Fabrowski, P., Necakov, A.S., Mumbauer, S., Loeser, E., Reversi, A., Streichan, S., Briggs, J.A. & De Renzis, S.
Nat Commun. 2013;4:2244. doi: 10.1038/ncomms3244.
During morphogenesis, remodelling of cell shape requires the expansion or contraction of plasma membrane domains. Here we identify a mechanism underlying the restructuring of the apical surface during epithelial morphogenesis in Drosophila. We show that the retraction of villous protrusions and subsequent apical plasma membrane flattening is an endocytosis-driven morphogenetic process. Quantitation of endogenously tagged GFP::Rab5 dynamics reveals a massive increase in apical endocytosis that correlates with changes in apical morphology. This increase is accompanied by the formation of tubular plasma membrane invaginations that serve as platforms for the de novo generation of Rab5-positive endosomes. We identify the Rab5-effector Rabankyrin-5 as a regulator of this pathway and demonstrate that blocking dynamin activity results in the complete inhibition of tubular endocytosis, in the disappearance of Rab5 endosomes, and in the inhibition of surface flattening. These data collectively demonstrate a requirement for endocytosis in morphogenetic remodelling during epithelial development.
Europe PMC

The ubiquitin ligase HACE1 regulates Golgi membrane dynamics during the cell cycle.
Tang, D., Xiang, Y., De Renzis, S., Rink, J., Zheng, G., Zerial, M. & Wang, Y.
Nat Commun. 2011 Oct 11;2:501. doi: 10.1038/ncomms1509.
Partitioning of the Golgi membrane into daughter cells during mammalian cell division occurs through a unique disassembly and reassembly process that is regulated by ubiquitination. However, the identity of the ubiquitin ligase is unknown. Here we show that the Homologous to the E6-AP Carboxyl Terminus (HECT) domain containing ubiquitin ligase HACE1 is targeted to the Golgi membrane through interactions with Rab proteins. The ubiquitin ligase activity of HACE1 in mitotic Golgi disassembly is required for subsequent postmitotic Golgi membrane fusion. Depletion of HACE1 using small interfering RNAs or expression of an inactive HACE1 mutant protein in cells impaired postmitotic Golgi membrane fusion. The identification of HACE1 as a Golgi-localized ubiquitin ligase provides evidence that ubiquitin has a critical role in Golgi biogenesis during the cell cycle.
Europe PMC

Unmasking activation of the zygotic genome using chromosomal deletions in the Drosophila embryo.
De Renzis, S., Elemento, O., Tavazoie, S. & Wieschaus, E.F.
PLoS Biol. 2007 May;5(5):e117.
During the maternal-to-zygotic transition, a developing embryo integrates post-transcriptional regulation of maternal mRNAs with transcriptional activation of its own genome. By combining chromosomal ablation in Drosophila with microarray analysis, we characterized the basis of this integration. We show that the expression profile for at least one third of zygotically active genes is coupled to the concomitant degradation of the corresponding maternal mRNAs. The embryo uses transcription and degradation to generate localized patterns of expression, and zygotic transcription to degrade distinct classes of maternal transcripts. Although degradation does not appear to involve a simple regulatory code, the activation of the zygotic genome starts from intronless genes sharing a common cis-element. This cis-element interacts with a single protein, the Bicoid stability factor, and acts as a potent enhancer capable of timing the activity of an exogenous transactivator. We propose that this regulatory mode links morphogen gradients with temporal regulation during the maternal-to-zygotic transition.
Europe PMC

Dorsal-ventral pattern of Delta trafficking is established by a Snail-Tom-Neuralized pathway.
De Renzis, S., Yu, J., Zinzen, R. & Wieschaus, E.
Dev Cell. 2006 Feb;10(2):257-64.
The intracellular trafficking of the Notch ligand Delta plays an important role in the activation of the Notch pathway. We have addressed the snail-dependent regulation of Delta trafficking during the plasma membrane growth of the mesoderm in the Drosophila embryo. We show that Delta is retained in endocytic vesicles in the mesoderm but expressed on the surface of the adjacent ectoderm. This trafficking pattern requires Neuralized. We developed a protocol based on chromosomal deletion and microarray analysis that led to the identification of tom as the target of snail regulating Delta trafficking. Snail represses Tom expression in the mesoderm and thereby activates Delta trafficking. Overexpression of Tom abolishes Delta trafficking and signaling to the adjacent mesoectoderm. Loss of Tom produces mesoderm-type Delta trafficking in the entire blastoderm epithelium and an expansion of mesoectoderm gene expression. We propose that Tom antagonizes the activity of Neuralized and thus establishes a sharp mesoderm-mesoectoderm boundary of Notch signaling.
Europe PMC

Divalent Rab effectors regulate the sub-compartmental organization and sorting of early endosomes.
de Renzis, S., Sonnichsen, B. & Zerial, M.
Nat Cell Biol. 2002 Feb;4(2):124-33.
The three GTPases Rab5, Rab4 and Rab11 regulate sequential transport steps along the endocytic/recycling pathway, and occupy distinct membrane domains on early and recycling endosomes. To address the mechanisms that regulate communication between such domains, we searched for proteins that interact with both Rab5 and Rab4. Here, we report that Rabenosyn-5, a previously identified Rab5 effector, also binds to Rab4. Rabenosyn-5 overexpression increased the association between Rab5 and Rab4 endosomal domains and decreased the fraction of Rab4- and Rab11-positive structures. This redistribution was accompanied by a faster rate of transferrin recycling from early endosomes to the cell surface and reduced transport to Rab11-containing perinuclear recycling endosomes. These effects depend on the ability of Rabenosyn-5 to interact with Rab4. We propose that divalent Rab effectors regulate protein sorting and recycling by connecting Rab domains on early endosomes.
Europe PMC

Distinct membrane domains on endosomes in the recycling pathway visualized by multicolor imaging of Rab4, Rab5, and Rab11.
Sonnichsen, B., De Renzis, S., Nielsen, E., Rietdorf, J. & Zerial, M.
J Cell Biol. 2000 May 15;149(4):901-14.
Two endosome populations involved in recycling of membranes and receptors to the plasma membrane have been described, the early and the recycling endosome. However, this distinction is mainly based on the flow of cargo molecules and the spatial distribution of these membranes within the cell. To get insights into the membrane organization of the recycling pathway, we have studied Rab4, Rab5, and Rab11, three regulatory components of the transport machinery. Following transferrin as cargo molecule and GFP-tagged Rab proteins we could show that cargo moves through distinct domains on endosomes. These domains are occupied by different Rab proteins, revealing compartmentalization within the same continuous membrane. Endosomes are comprised of multiple combinations of Rab4, Rab5, and Rab11 domains that are dynamic but do not significantly intermix over time. Three major populations were observed: one that contains only Rab5, a second with Rab4 and Rab5, and a third containing Rab4 and Rab11. These membrane domains display differential pharmacological sensitivity, reflecting their biochemical and functional diversity. We propose that endosomes are organized as a mosaic of different Rab domains created through the recruitment of specific effector proteins, which cooperatively act to generate a restricted environment on the membrane.
Europe PMC