PITX3 encodes a member of the RIEG/PITX homeobox family, which is in the bicoid class of homeodomain proteins. Members of this family act as transcription factors. Mutations of this gene have been associated with anterior segment mesenchymal dysgenesis (ASMD) and congenital cataracts. This protein is involved in lens formation during eye development.

MiR133B regulates the maturation and function of midbrain dopaminergic neurons within a negative feedback circuit that includes the paired-like homeodomain transcription factor PITX3. The authors found that PITX3 induces transcription of miR133B, which in turn suppresses PITX3 expression.