scholarly journals Independent cadherin–catenin and Bazooka clusters interact to assemble adherens junctions

2009 ◽  
Vol 185 (5) ◽  
pp. 787-796 ◽  
Author(s):  
Melanie A. McGill ◽  
R.F. Andrew McKinley ◽  
Tony J.C. Harris
Keyword(s):  
Drosophila Melanogaster ◽  
Fluorescence Recovery After Photobleaching ◽  
Molecular Level ◽  
Adherens Junctions ◽  
Adherens Junction ◽  
Drosophila Embryo ◽  
Fluorescence Recovery ◽  
Early Drosophila Embryo ◽  
Epithelial Structure ◽  
Independent Protein

Proper epithelial structure requires adherens junction (AJ) assembly. In the early Drosophila embryo, AJ assembly depends on Bazooka (Baz; PAR-3), but it is unclear how Baz affects AJ assembly and what precursors are involved. To understand this process at the molecular level, we counted the number of core AJ proteins and Baz proteins at an average spot AJ (SAJ) and determined their dynamics with fluorescence recovery after photobleaching experiments. These data reveal that SAJs are subdivided into Baz clusters and cadherin–catenin clusters with independent protein numbers and dynamics. This independence suggests that precursory cadherin–catenin clusters might form before SAJ assembly. We identify cadherin–catenin clusters forming between apical microvilli. Further analyses show that they form independently of Baz and that Baz functions in repositioning them to apicolateral sites for full SAJ assembly. Our data implicate cell protrusions in initial cadherin–catenin clustering in the Drosophila melanogaster embryo. Then, independent Baz clusters appear to engage the cadherin–catenin clusters to assemble SAJs.

scholarly journals Morphogenetic forces planar polarize LGN/Pins in the embryonic head during Drosophila gastrulation

2022 ◽  
Author(s):  
Jaclyn M Camuglia ◽  
Soline Chanet ◽  
Adam C Martin
Keyword(s):  
Planar Cell Polarity ◽  
Adherens Junction ◽  
Drosophila Embryo ◽  
Spindle Orientation ◽  
Planar Polarity ◽  
Ventral Furrow ◽  
Adherens Junction Protein ◽  
Early Drosophila Embryo ◽  
Junction Protein

Spindle orientation is often achieved by a complex of Pins/LGN, Mud/NuMa, Gαi, and Dynein, which interacts with astral microtubules to rotate the spindle. Cortical Pins/LGN recruitment serves as a critical step in this process. Here, we identify Pins-mediated planar cell polarized divisions in several of the mitotic domains of the early Drosophila embryo. We found that neither planar cell polarity pathways nor planar polarized myosin localization determined division orientation; instead, our findings strongly suggest that Pins planar polarity and force generated from mesoderm invagination are important. Disrupting Pins polarity via overexpression of a myristoylated version of Pins caused randomized division angles. We found that disrupting forces through chemical inhibitors, laser ablation, and depletion of an adherens junction protein disrupted Pins planar polarity and spindle orientation. Furthermore, snail depletion, which abrogates ventral furrow forces, disrupted Pins polarization and spindle orientation, suggesting that morphogenetic movements and resulting forces transmitted through the tissue can polarize Pins and orient division. Thus, morphogenetic forces associated with mesoderm invagination result in planar polarized Pins to mediate division orientation at a distant region of the embryo during morphogenesis. To our knowledge, this is the first in vivo example where mechanical force has been shown to polarize Pins to mediate division orientation.

scholarly journals Microtubules promote intercellular contractile force transmission during tissue folding

2019 ◽  
Vol 218 (8) ◽  
pp. 2726-2742 ◽  
Author(s):  
Clint S. Ko ◽  
Vardges Tserunyan ◽  
Adam C. Martin
Keyword(s):  
Drosophila Melanogaster ◽  
Cell Shape ◽  
Adherens Junctions ◽  
Adherens Junction ◽  
Contractile Force ◽  
Force Transmission ◽  
Microtubule Network ◽  
Apical Constriction ◽  
Actomyosin Contractility ◽  
Actomyosin Contraction

During development, forces transmitted between cells are critical for sculpting epithelial tissues. Actomyosin contractility in the middle of the cell apex (medioapical) can change cell shape (e.g., apical constriction) but can also result in force transmission between cells via attachments to adherens junctions. How actomyosin networks maintain attachments to adherens junctions under tension is poorly understood. Here, we discovered that microtubules promote actomyosin intercellular attachments in epithelia during Drosophila melanogaster mesoderm invagination. First, we used live imaging to show a novel arrangement of the microtubule cytoskeleton during apical constriction: medioapical Patronin (CAMSAP) foci formed by actomyosin contraction organized an apical noncentrosomal microtubule network. Microtubules were required for mesoderm invagination but were not necessary for initiating apical contractility or adherens junction assembly. Instead, microtubules promoted connections between medioapical actomyosin and adherens junctions. These results delineate a role for coordination between actin and microtubule cytoskeletal systems in intercellular force transmission during tissue morphogenesis.

scholarly journals Influence of cyclin type and dose on mitotic entry and progression in the early Drosophila embryo

2009 ◽  
Vol 184 (5) ◽  
pp. 639-646 ◽  
Author(s):  
Mark L. McCleland ◽  
Jeffrey A. Farrell ◽  
Patrick H. O'Farrell
Keyword(s):  
Cell Cycle ◽  
Drosophila Melanogaster ◽  
Drosophila Embryo ◽  
Cell Cycle Regulators ◽  
Mitotic Progression ◽  
Mitotic Entry ◽  
Early Drosophila Embryo ◽  
Real Time Visualization ◽  
The One

Cyclins are key cell cycle regulators, yet few analyses test their role in timing the events that they regulate. We used RNA interference and real-time visualization in embryos to define the events regulated by each of the three mitotic cyclins of Drosophila melanogaster, CycA, CycB, and CycB3. Each individual and pairwise knockdown results in distinct mitotic phenotypes. For example, mitosis without metaphase occurs upon knockdown of CycA and CycB. To separate the role of cyclin levels from the influences of cyclin type, we knocked down two cyclins and reduced the gene dose of the one remaining cyclin. This reduction did not prolong interphase but instead interrupted mitotic progression. Mitotic prophase chromosomes formed, centrosomes divided, and nuclei exited mitosis without executing later events. This prompt but curtailed mitosis shows that accumulation of cyclin function does not directly time mitotic entry in these early embryonic cycles and that cyclin function can be sufficient for some mitotic events although inadequate for others.

scholarly journals The AF-6 Homolog Canoe Acts as a Rap1 Effector During Dorsal Closure of the Drosophila Embryo

Genetics ◽  
2003 ◽  
Vol 165 (1) ◽  
pp. 159-169
Author(s):  
Benjamin Boettner ◽  
Phoebe Harjes ◽  
Satoshi Ishimaru ◽  
Michael Heke ◽  
Hong Qing Fan ◽  
...  
Keyword(s):  
Molecular Mechanisms ◽  
Genetic Interaction ◽  
Critical Role ◽  
Adherens Junction ◽  
Small Gtpases ◽  
Drosophila Embryo ◽  
Dorsal Closure ◽  
Cell Sheets ◽  
Jnk Pathway

Abstract Rap1 belongs to the highly conserved Ras subfamily of small GTPases. In Drosophila, Rap1 plays a critical role in many different morphogenetic processes, but the molecular mechanisms executing its function are unknown. Here, we demonstrate that Canoe (Cno), the Drosophila homolog of mammalian junctional protein AF-6, acts as an effector of Rap1 in vivo. Cno binds to the activated form of Rap1 in a yeast two-hybrid assay, the two molecules colocalize to the adherens junction, and they display very similar phenotypes in embryonic dorsal closure (DC), a process that relies on the elongation and migration of epithelial cell sheets. Genetic interaction experiments show that Rap1 and Cno act in the same molecular pathway during DC and that the function of both molecules in DC depends on their ability to interact. We further show that Rap1 acts upstream of Cno, but that Rap1, unlike Cno, is not involved in the stimulation of JNK pathway activity, indicating that Cno has both a Rap1-dependent and a Rap1-independent function in the DC process.

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