Examining the temporal expression and regulation of type I MAGE proteins in spermatogenesis (930.4)

Background: Type I Melanoma Antigen Gene (MAGE) proteins are normally expressed in the trophoblast and germline cell lineages, but are aberrantly expressed in various human cancers. Recently, MAGEs were shown to enhance the activity of E3 RING ligases, however the physiological function of MAGEs in the testis and tumorigenesis is yet unknown. With these questions in mind the aim of the project was to confirm germline specific expression of MAGE genes, and assess whether the temporal pattern of MAGE gene expression is associated with specific developmental stages of spermatogenesis. Methods Testes were collected from C57BI/6 mice at different times during postnatal development. Spermatogenic cells were isolated and enriched using velocity sedimentation in 2‐4% BSA gradient. Expression of type I MAGEs was measured from collected spermatogenic cells using RT‐QPCR. Interaction of type‐I human MAGEs and human ZBTB16/PLZF stem cell marker protein was explored by co‐immunoprecipiration experiments in HeLa cells using exogenously expressed tagged forms of the proteins. Results MAGE‐B4 was expressed in spermatogonia during mitosis. MAGE‐As were expressed in spermatogonia during mitosis and prepachytene spermatogonia before entering meiosis. MAGE‐B1, ‐Al1, and ‐Al2 were expressed in haploid spermatids in spermiogenesis. MAGE‐B3, ‐B16, ‐B18 and ‐Al3 were expressed in all germ cells and somatic cells during spermatogenesis. Additionally, human MAGE‐A11 and ‐A12 were shown to interact with human ZBTB16/PLZF. Conclusion Type I MAGEs are expressed in different developmental stages of spermatogenesis, suggesting diverse functions. Future investigation is necessary to determine if MAGE‐A genes regulate the activity of ZBTB16/PLZF. Grant Funding Source : CPRIT R117