The PAX7 gene encodes a member of the paired box family of transcription factors. While PAX7 is yet to be fully characterized, studies on its lower ortholog genes have helped elucidate its function. The protein is hence believed to play a key role in muscle tissue morphogenesis by regulating the proliferation of myoblast cells. This is mainly done by positively regulating histone methylation at target sites. Importantly, PAX7 only plays a role in the early developmental stages when progenitor cells make the transition into quiescence, and the protein is not found to have any effect on the proliferation of muscle precursor cells in adult muscles.
Translocations have been found to occur that fuse PAX7 with the Forkhead in Rhabdomyosarcoma (FKHR) gene, resulting in a PAX7/FKHR fusion gene encoding chimeric transcription factors. This fusion gene has been associated with Alveolar Rhabdomyosarcoma, a malignant soft tissue tumor commonly affecting children and adolescents.
The PAX7 gene is located on the short arm of chromosome 1. It spans a length of 117.8 kb of DNA and its coding sequence is spread across 9 exons. The gene encodes a 55 kDa protein product composed of 505 amino acids. Several additional isoforms of the PAX7 protein exist due to alternatively spliced transcript variants. The gene is found to be overexpressed in the skeletal muscle and brain.
Monies et al. (2017) assessed the genomic landscape of Saudi Arabia based on the findings of 1000 diagnostic panels and exomes. One patient, a 45-year-old female, presented with hypotonia, exercise intolerance, easy fatigue, muscle weakness, stroke or stroke-like episodes, recurrent headaches and creatine phosphokinase abnormalities. Whole exome sequencing helped identify a heterozygous mutation (c.433C>T, p.R145X) in exon 3 of the patient’s PAX7 gene. This gene mutation was considered a candidate for pathogenicity due to several reasons: it was a novel variant predicted to be deleterious, the PAX7 gene had an established role in skeletal muscle development and it had a low %HI score of 11.2. The authors noted the need for independent confirmation of this association.
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