DEVELOPMENT: No Cutting out of Bounds

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Science  12 Dec 2003:
Vol. 302, Issue 5652, pp. 1865a
DOI: 10.1126/science.302.5652.1865a

Mechanisms that support spatial patterning during development include the localized activation of regulatory factors and signaling pathways. In Drosophila, dorsal-ventral polarity is established in part by activation of the Toll receptor on the ventral side of the embryo. Its ligand, Spätzle, is processed by a serine protease called Easter, and the activation of Easter is realized via a cascade of three other extracellular serine proteases.

Hashimoto et al. and Ligoxygakis et al. have shown that Easter activity is spatially regulated in early embryos by the maternally expressed and secreted serine protease inhibitor serpin 27A (Spn27A), which was detected throughout the perivitellin fluid surrounding the embryo. Loss of Spn27A function resulted in increased Easter activity, an increase in processed Spätzle, unrestricted activation of Toll, and a ventralized embryonic phenotype, whereas injection of Spn27A restored normal polarity and cell differentiation. Spn27A and Easter were also detected in a stable 1:1 complex. In mammals, the serpin antithrombin inactivates the extracellular serine protease thrombin as it diffuses away from sites of vascular damage, thereby restricting the initiation of the blood-clotting protease cascade to sites of injury. — LDC

Dev. Cell 10.1016/S1534580703003381(2003); Curr. Biol. 13, 2097 (2003).

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