PAX7 is a paired box transcription factor involved in fetal development and carcinogenesis. It is thought to be involved in tumor suppression, as PAX7 gene fusions with the forkhead transcription factor FOXO1 are associated with and prognostic for alveolar rhabdomyosarcoma. In the developing nervous system, PAX7 expression guides cell fate and morphology in the neuroepithelial layer and promotes the differentiation of neural progenitor cells into neurons. In immunohistochemistry, PAX7 has high nuclear positivity in skeletal muscle and in the tongue. In the brain and central nervous system, it has moderate expression in the cerebral cortex, midbrain, pons and medulla, and lower levels of positivity in the hippocampus, amygdala, basal ganglia, hypothalamus and spinal cord, and some positivity in the epididymis. References: J Clin Oncol. 2002 Jun 1;20(11):2672-9, PMID: 12039929; Bol Med Hosp Infant Mex. 2016 Nov - Dec;73(6):405-410, PMID: 29421285; J Comp Neurol. 2016 Apr 1;524(5):940-62, PMID: 26287727;