In Drosophila one LMO protein is encoded by the dLmo locus, and has been studied primarily for its role in the development of the fly wing, which has led to a model for its function (Milan et al., 1998; Shoresh et al., 1998; Zeng et al., 1998). dLMO protein inhibits the activity of the LIM–HD transcription factor Apterous through its interactions with the co–activator Chip (the fly homologue of Clim/Ldb1/NL1) (Fernandez-Funez et al., 1998; Milan and Cohen, 1999; van Meyel et al., 1999; Weihe et al., 2001). Binding of Chip to Apterous leads to its dimerization and activation. dLMO competes for Chip binding; consequently, increased dLMO levels lead to inhibition of Apterous/LIM-HD function, while reduced dLMO levels cause increased Apterous/LIM-HD activity.