Transcriptional regulator. May mediate transcription activation by binding to the E box-containing promoter (By similarity). Involved in neurogenesis. Involved in maintaining rhombomere boundaries in the hindbrain, probably via up-regulation of delta expression. May mediate transcription activation by binding to the E box-containing promoter. Efficient DNA binding requires dimerization with another bHLH protein. In the 24 hours embryo, expressed in hindbrain close to the anterior and posterior boundaries of rhombomeres 2-6 and in ventral cells close to the floor plate of most rhombomeres. Also expressed in the telencephalon, diencephalon, tegmentum and spinal cord at sites distinct from those expressing ascl1a. Not expressed in the adenohypophysis. First detected at 10 hours post-fertilization (hpf) increasing over the next 24 hours, then decreasing between 48 and 72 hours. Not detected in adult.