Dorsal closure is a stage of Drosophila embryogenesis in which lateral epidermal cell sheets bordering an eye-shaped dorsal opening ”zip” together to form a seamed and then seamless epithelium. Understanding this process is important because it models cell sheet movements such as neural tube closure and palate formation as well as wound healing in vertebrates. The dorsal opening itself is filled by a layer of thin, flat amnioserosal cells. The amnioserosa is bordered by actomyosin-rich purse strings that provide tension and maintain the shape of the opening as it closes. The expression of Echinoid in the lateral epidermis and the lack of expression in the amnioserosa is known to be essential for actomyosin cable formation, but what proteins govern the formation and stability of the purse string are not fully understood. I used a GFP-tagged alpha-Actinin fusion protein to visualize alpha-Actinin localization in Zasp52 and Echinoid double mutants as well as in Echinoid mutants only. Fluorescent imaging revealed that in Zasp52 and Echinoid double mutants, alpha-Actinin does not appear to localize to the purse string, while in Echinoid mutants it does. This provides evidence that it is Zasp52 that recruits alpha-Actinin to the purse string.
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