Non-cell-autonomous control of denticle diversity in the Drosophila embryo.

Certain Drosophila embryonic epidermal cells construct actin-based protrusions, called denticles, which exhibit stereotyped, column-specific differences in size, density and hook orientation. This precise denticle pattern is conserved throughout all drosophilids yet studied, and screening for mutations that affect this pattern has been used to identify genes involved in development and signaling. However, how column-specific differences are specified and the mechanism(s) involved have remained elusive. Here, we show that the transcription factor Stripe is required for multiple aspects of this column-specific denticle pattern, including denticle hook orientation. The induction of stripe expression in certain denticle field cells appears to be the primary mechanism by which developmental pathways assign denticle hook orientation. Furthermore, we show that the cytoskeletal linker protein Short stop (Shot) functions both cell-autonomously and non-autonomously to specify denticle hook orientation via interaction with the microtubule cytoskeleton. We propose that stripe mediates its effect on hook orientation, in part, via upregulation of shot.