The foggy mutant zebrafish show severe deficits in dopaminergic neurons, thus is an important tool to understanding the development of these neurons, which undergo degeneration in Parkinson's disease. Molecular study reveals that the foggy gene encodes a regulator of transcription elongation. Biochemical study suggests that the repressive activity of the Foggy protein is lost in the foggy mutant. The genes whose expression is normally repressed by Foggy are likely to play important roles in dopamine neuron development. However, their identity is unknown. Finding out these target genes of Foggy will provide important insights into dopamine neuron development and regeneration. They will also serve as an entry point to elucidate the role of transcription elongation in controlling neuronal development.