PAX9
Protein-coding gene in humans
From Wikipedia, the free encyclopedia
Paired box gene 9, also known as PAX9, is a protein which in humans is encoded by the PAX9 gene.[5][6] It is also found in other mammals.[7]
Expression and function
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.[8][9] Later on, Pax9 is also expressed in the axial skeleton.[8] Pax9 is required for craniofacial, tooth and limb development,[7][8] and may more generally involve development of stratified squamous epithelia as well as various organs and skeletal elements.[5] PAX9 plays a role in the absence of wisdom teeth in some human populations (possibly along with the less well studied AXIN2 and MSX1).[7]
Clinical significance
This gene was found amplified in lung cancer. The amplification covers three tissue developmental genes - TTF1, NKX2-8, and PAX9.[10] It appears that certain lung cancer cells select for DNA copy number amplification and increased RNA/protein expression of these three coamplified genes for functional advantages.
Oligodontia
Oligodontia is a genetic disorder caused by the mutation of the PAX9 gene. This disorder results in the congenital absence of 6 or more permanent teeth not including wisdom teeth.[11] Also known as selective tooth agenesis (STHAG), it is the most common disorder in regard to human dentition, affecting a little less than one fourth of the population.[11] The gene PAX9 which can be found on chromosome 14 encodes a group of transcription factors that play an important role in early tooth development.[12] In humans, a frameshift mutation in the paired domain of PAX9 was discovered in those affected with oligodontia.[13] Multiple mechanisms are possible by which the mutation may arise. Recently, a study involving the missense mutation of a PAX9 gene suggests that the loss of function due to the absence DNA binding domain is a mechanism that causes oligodontia.[14] Those who express the PAX9 mutation and develop the disorder continue to have a normal life expectancy. Along with the mutation of the PAX9 gene, MSX1 gene mutations have also shown to affect dental development in fetuses.[14]