PAX3

PAX3 is a gene that belongs to the paired box (PAX) family of transcription factors. This gene was formerly known as splotch. PAX3 has been identified with ear, eye and facial development. Mutations in it can cause Waardenburg syndrome types 1 and 3 . It is expressed in early embryonic phases in dermatomyotome of paraxial mesoderm which it helps to demarcate. In that way PAX3 contributes to early striated muscle development since all myoblasts are derived from dermatomyotome of paraxial mesoderm.

Alternative splicing results in transcripts encoding isoforms with different C-termini.

Role in rhabdomyosarcoma

A PAX3/FKHR fusion gene is often associated with the alveolar type of rhabdomyosarcoma, a kind of cancer arisen from striated muscle cells. Translocation between chromosomes 2 & 13 produce fusion protein PAX3/FKHR which serves as a tumor marker in this type of RMS.Also in ARMS expressing PAX3/FKHR increased risk of metastasis to bone marrow and hence increased rate of failure and death were seen.