The Drosophila tamou gene, a component of the activating pathway of extramacrochaetae expression, encodes a protein homologous to mammalian cell-cell junction-associated protein ZO-1.

In Drosophila sensory organ development, the balance of activities between proneural genes and repressor genes defines a proneural cluster as a population of competent cells for neural development. In this study, we report the isolation and analysis of the tamou (tam) gene that encodes a cell-cell junction-associated protein, which is homologous to mammalian ZO-1, a member of the membrane-associated guanylate kinase homolog family. The tam mutation reduces the transcription of a repressor gene, extramacrochaetae, and causes enlargement of a proneural cluster where supernumerary precursor cells emerge, resulting in extra mechanosensory organs in the fly. These results suggest that the membrane-associated Tam protein is involved in the signaling pathway that activates emc expression.