The actin regulators Enabled and Diaphanous direct distinct protrusive behaviors in different tissues during Drosophila development.
Bottom Line: The actin elongation factors Diaphanous and Enabled both promote barbed-end actin polymerization and can stimulate filopodia in cultured cells.We hypothesized that differing Enabled and/or Diaphanous activity drives these differences.Combining gain- and loss-of-function with quantitative approaches revealed that Diaphanous and Enabled each regulate filopodial behavior in vivo and defined a quantitative "fingerprint"--the protrusive profile--which our data suggest is characteristic of each actin regulator.
Affiliation: Department of Biology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599.Show MeSH
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Mentions: Ena reduction had striking qualitative effects on filopodial behavior (Figure 7, A and B, and Supplemental Movie S8). We thus quantitated different filopodial parameters. Loss of zygotic Ena significantly reduced both filopodial maximum length and lifetime (Figure 7, E and F, and Supplemental Figure S1B), including effects on time spent extending and retracting (Supplemental Figure S1, C–F). Ena reduction had a parallel effect on the lifetime of the 20% longest-lived filopodia (Figure 7G). In contrast, lamellipodial area remained statistically indistinguishable from that of wild type (Figure 7H), and Ena reduction did not significantly alter AS filopodial number relative to that of wild type (Figure 7D), indicating that either Ena is not responsible for most filopodia initiation in the AS or residual maternal Ena is sufficient. This is in marked contrast to the LE, for which reducing Ena significantly reduces filopodia number (Homem and Peifer, 2009). Thus Ena reduction partially phenocopied FP4mito expression, suggesting that Ena does, in fact, help regulate filopodial behavior in this tissue. However, analysis of the protrusive profile of filopodia in ena mutants revealed that filopodia are both shorter and shorter-lived, and thus the slope of the protrusion profile was unchanged (Figure 7I and Supplemental Figure S2C). This suggested that Dia might elongate the remaining filopodia, consistent with the idea that Dia normally regulates the wild-type AS protrusion profile.
Affiliation: Department of Biology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599.