Distal-less function during Drosophila appendage and sense organ development

The Drosophila Distal-less (Dll) gene was identified in the early 1980s by means of dominant and recessive mutations that caused both striking antenna -to-leg transformations and leg truncations, The gene initially was named " Bristle on arista" or "Brista" because one aspect of the phenotype is the f ormation of leg bristles on the antenna (Sato [1984] Drosophila Information Service 60:180-182; Sunkel and Whittle [1987] Wilhelm Roux's. Arch. Dev. B iol. 196:124-132). Subsequent studies have revealed that Dll encodes a home odomain transcription factor (Cohen et al. [1989] Nature 338:432-434) that is expressed throughout limb development from embryogenesis on (Cohen [1990 ] Nature 343:173-177; Weigmann and Cohen [1999] Development 126:3823-3830). Dll is required for the elaboration of distal pattern elements in the ante nna, the legs, the limb-derived gnathal structures (Cohen and Jurgens [1989 ] Nature 482-485), and the anal plate (Gorfinkiel et al. [1999] Mech. Dev. 868:113-123) and can initiate proximodistal axis formation when expressed e ctopically (Gorfinkiel et al. [1997] Genes Dev. 11: 2259-2271). Dll homolog s are expressed in developing appendages in at least six coelomate phyla, i ncluding chordates (Akimenko et al. [1994] J. Neurosci. 14:3475-3486; Beauc hemin and Savard [1992] Dev. Biol. 154:55-65; Bulfone et al. [1993] Mech. D ev. 40:129-140; Dolle et al. [1992] Differentiation 49:93-99; Ferrari et ai . [1995] Mech. Dev, 52:257-264; Panganiban ct al. [1997] Proc. Natl. Acad. Sci. USA 94:5162-5166; Simeone et al. [1994] Proc. Natl. Acad. Sci. USA 91: 2250-2254), consistent with requirements for Dlx function in normal limb de velopment across the animal kingdom. Distal-less also has been implicated i n various aspects of vertebrate neurogenesis (see reviews by Kraus and Lufk in [1999] J. Cell, Biochem, 32-33:133-140 and the accompanying review by Be anan and Sargent [2000] Dev. Dyn, 218:545-553), Here, I outline what is kno wn about Dll function and regulation in Drosophila. (C) 2000 Wiley-Liss, In c.