Published 29 August 2005. doi:10.1083/jcb.200505127
The Rockefeller University Press, 0021-9525 $8.00
JCB, Volume 170, Number 5, 813-823
The positioning and segregation of apical cues during epithelial polarity establishment in Drosophila
Tony J.C. Harris1 and
Mark Peifer1,2
1 Department of Biology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599
2 Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599
Correspondence to Mark Peifer: peifer{at}unc.edu; or Tony J.C. Harris: tonyh{at}email.unc.edu
Cell polarity is critical for epithelial structure and function. Adherens junctions (AJs) often direct this polarity, but we previously found that Bazooka (Baz) acts upstream of AJs as epithelial polarity is first established in Drosophila. This prompted us to ask how Baz is positioned and how downstream polarity is elaborated. Surprisingly, we found that Baz localizes to an apical domain below its typical binding partners atypical protein kinase C (aPKC) and partitioning defective (PAR)-6 as the Drosophila epithelium first forms. In fact, Baz positioning is independent of aPKC and PAR-6 relying instead on cytoskeletal cues, including an apical scaffold and dynein-mediated basal-to-apical transport. AJ assembly is closely coupled to Baz positioning, whereas aPKC and PAR-6 are positioned separately. This forms a stratified apical domain with Baz and AJs localizing basal to aPKC and PAR-6, and we identify specific mechanisms that keep these proteins apart. These results reveal key steps in the assembly of the apical domain in Drosophila.
Abbreviations used in this paper: AJ, adherens junction; aPKC, atypical protein kinase C; Arm, Armadillo; Baz, Bazooka; CD, cytochalasin D; Crb, Crumbs; DE-Cad, Drosophila E-cadherin; Dhc, dynein heavy chain; DIC, dynein intermediate chain; Dlg, Discs large; IP, immunoprecipitation; Lgl, lethal giant larvae; MT, microtubule; m/z, maternal/zygotic; PAR, partitioning defective; PMGI, posterior midgut invagination; WT, wild type.

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