Transcription factor involved in neuronal fate specification. First required in embryonic CNS development to define the number of cells that express apterous (ap) in the ap thoracic cluster of interneurons. Later on, it plays a central role in the combinatorial code of transcription factors that specifies the fate of the Tv neuron in the ap cluster by participating in the transcription regulation of FMRFa in Tv cells. Also required for projection neuron dendritic targeting. Interacts with nab; which acts as a coactivator. Interacts with ap. Largely restricted to subsets of cells in the CNS throughout embryonic and first instar larval (L1) development. Expressed in a population of lateral interneurons, primarily projecting axons in the anterior and posterior commissures. Overlaps with ap within the thoracic ap cluster. By stage 17, it is restricted to 2 neurons within the ap-cluster, with one neuron typically continuing to display higher levels of expression. Selectively expressed at higher levels within the FMRFa Tv neurons. Expressed in all leucokinergic cells. Death at larval stage. Larvae display a motility defect whereby the body wall musculature overcontract radially during the peristaltic wave typical of insect larval motility, apparent as a 'squeezing' of intestine. Belongs to the krueppel C2H2-type zinc-finger protein family.