Functions as a transcriptional repressor. May repress OTX2-mediated transactivation by forming a heterodimer with OTX2 on the P3C (5'-TAATCCGATTA-3') sequence. Required for brain development (By similarity). Homodimer or heterodimer. Forms heterodimers with OTX2 (By similarity). Belongs to the paired homeobox family. Extended N-terminus.