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Cleavage is a common process during early embryogenesis. Similar to conventional cytokinesis, Drosophila cellularization, a unique form of cleavage, requires precise regulation of non-muscle myosin II ("myosin") at cleavage furrows, where myosin forms an interconnected basal array before reorganizing into individual cytokinetic rings. However, how myosin is regulated through both conserved and cellularization-specific mechanisms during this special form of cytokinesis remains unclear.
In my first project, I investigated the molecular mechanisms by which the cellularization-specific zygotic gene dunk regulates myosin at the basal array. I identified anillin (Scraps in Drosophila), a conserved scaffolding protein in cytokinesis, as the primary binding partner of Dunk. We discovered that Dunk colocalizes with and regulates anillin's localization at cleavage furrows during early cellularization. Additionally, we demonstrated that anillin colocalizes with myosin and controls myosin recruitment at the basal array, preceding anillin's well-documented function in regulating cytokinetic ring assembly. Finally, we found that Dunk genetically interacts with anillin, indicating that the two proteins regulate myosin organization within the same pathway. Based on these findings, we propose that Dunk modulates myosin recruitment and organization during early cellularization by interacting with and regulating anillin.
In my second project, I explored the roles of Dunk and anillin in regulating myosin cortical flow, a process contributing to myosin recruitment at the basal array. We uncovered the colocalization and co-movement of anillin and myosin puncta within the cortical flow and demonstrated that anillin regulates the formation of myosin puncta. Furthermore, we showed that Dunk influences the size and distribution of cortical myosin puncta by modulating anillin. This study revealed a previously unrecognized function of Dunk and anillin in myosin regulation at the onset of cellularization and may provide a foundation for understanding the subsequent myosin mislocalization phenotype at the basal array in dunk and anillin mutants.
Together, my thesis work provides a thorough investigation of the regulation of myosin by Dunk and anillin during the early stage of cellularization, shedding light on how embryos manage to use the interplay between zygotically expressed master regulators and maternally provided common structural elements to control morphogenesis.
Chen, Jiayang, "Anillin and Dunk: The Conserved and Non-conserved Players Regulating Myosin Dynamics in Drosophila Cleavage" (2023). Dartmouth College Ph.D Dissertations. 146.
Available for download on Wednesday, May 14, 2025