The role of Teashirt in proximal leg development in Drosophila: Ectopic teashirt expression reveals different cell behaviours in ventral and dorsal domains

Localised transcription factors specify the identity of developmental domai ns. Here we analyse the function of the Teashirt zinc finger protein, which is expressed in the proximal domain of the Drosophila leg. By ectopic expr ession of a teashirt transgene we show that Teashirt contributes to the dif ferences in cell-cell adhesion between proximal and distal leg cells. Where as clones of cells expressing the teashirt transgene survive in the endogen ous Teashirt domain, most cells expressing Teashirt in an ectopic distal po sition are lost from the epithelium. In clones which were recovered in the distal domain, different effects were seen dependent on position with respe ct to the dorsal-ventral axis. In the ventral region, where Wingless is sig nalling, surviving clones express Teashirt and cause abnormalities in the a dult leg. Contrarily, lateral and dorsal clones generally do not accumulate Teashirt and have no effect on patterning. One exception to the differenti al dorsal-ventral effects occurs at the boundary between Teashirt-expressin g and -nonexpressing cells. Both ectopic and hypomorphic loss of teashirt a ffects patterning at all positions at the boundary, suggesting that Teashir t plays a crucial role in boundary formation. The results are discussed wit h respect to the roles of transcriptional and posttranscriptional mechanism s in proximal-distal axis patterning of the Drosophila legs. (C) 1999 Acade mic Press.