Transcription factor involved in developmental processes such as cell fate determination, gene transcriptional regulation and progenitor cell regulation in a number of organs. Plays a critical role in embryonic development and functions as a key regulatory protein in neurogenesis and the development of the heart, eye lens, liver, pancreas and the lymphatic system. Involved in the regulation of the circadian rhythm. Represses: transcription of the retinoid-related orphan receptor RORG, transcriptional activator activity of RORA and RORG and the expression of RORA/G-target genes including core clock components: ARNTL/BMAL1, NPAS2 and CRY1 and metabolic genes: AVPR1A and ELOVL3. Interacts with RORA and RORG (via AF-2 motif). RORG promotes its nuclear localization. Expressed in the young neurons of the subventricular region of the CNS, developing eye lens and pancreas. It is also found in the developing liver, heart and skeletal muscle. In the eye, expressed in the lens and retina at postnatal day 10. In the retina, localized to the inner nuclear layer. In the lens, localized to epithelial and fiber cells. Expressed in a circadian manner in the liver with a peak at ZT4. The Prospero-type homeodomain and the adjacent Prospero domain act as a single structural unit, the Homeo-Prospero domain (Potential). The Prospero-type homeodomain is essential for repression of RORG transcriptional activator activity (PubMed:23723244). Belongs to the Prospero homeodomain family.