Paired box gene 9, also known as PAX9, is a protein which in humans is encoded by the PAX9 gene. This gene is a member of the paired box (PAX) family of transcription factors. During mouse embryogenesis Pax9 expression starts from embryonic day 8.5 and becomes more evident by E9.5; at this stage its expression is restricted to the pharyngeal endoderm. Later on, Pax9 is also expressed in the axial skeleton. Pax9 is required for craniofacial, tooth and limb development, and may more generally involve development of stratified squamous epithelia as well as various organs and skeletal elements. PAX9 plays a role in the absence of wisdom teeth in some human populations. It is a transcription factor required for normal development of thymus, parathyroid glands, ultimobranchial bodies, teeth, skeletal elements of skull and larynx as well as distal limbs.
