Essential for segmentation and CNS development. May modulate the actions of other transcription factors, including gap and pair-rule proteins. Initially expressed in a pair-rule-like pattern which is rapidly replaced by strong neuroectoderm expression. Expressed during embryogenesis. Flies exhibit severe segmentation defects, including loss and/or fusion of abdominal denticle belts and stripe-specific defects in pair-rule and segment polarity gene expression. Mutant embryos also exhibit loss of specific neurons, fusion of adjacent ventral nerve cord ganglia and aberrant axon scaffold organization.