Establishment and Analysis of ArpM1/Actrt3 deficient mice – a tool to study male factor infertility

• Applicant: Professor Dr. Hubert Schorle
• Subject Area: Reproductive Medicine, Urology ; Developmental Biology ; Cell Biology
• Term: since 2025
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 546839078

Actin related protein T3 (ACTRT3, aka: Actin related protein M1 (Arpm1)) is a cytoskeletal protein exclusively expressed during spermiogenesis in the phase of tremendous re-shaping from round to elongating spermatids. ACTRT3 is detected in the perinuclear theca (PT), which is a thin, protein-rich layer between the developing Acrosome and the hypercondensing nucleus. ACTRT3 has been shown to bind to Profilin3 (PFN3), a protein which is necessary for proper Acrosome formation and function. We demonstrated, that ACTRT3 protein is lost in sperm of PFN3-deficient mice suggesting, that the interaction is crucial for stability of the protein (complex). Here, we have established an ACTRT3 deficient mouse model and show, that such males are subfertile. Preliminary data suggest a defect in the Acrosome structure and function. We hypothesize, that ACTRT3, in conjunction with PFN3 acts as molecular glue to connect PT and Acrosome. We propose to i) analyze the phenotype in detail, ii) use IP-MassSpec to determine interaction partners of ACTRT3, iii) validate the interaction by CoIP (in testes extracts and using cell culture systems) and iv) use a proximity ligation assay (PLA) to determine the location and the interaction of partner proteins in vivo. These experiments will give us information about the role and the interaction partners of ACTRT3 during spermiogenesis. In comparing our data with the genetic variants of infertile men collected by the MERGE consortium, we will be able to determine the impact of mutations in ACTRT3 and potential interaction partners on human male fertility. Thus, the proposed experiments will not only help in understanding the various sperm specific structural proteins involved in Acrosome-PT formation, but also advance our knowledge of male infertility and help to diagnose and develop of treatment regimen.

• DFG Programme: Research Grants