Characterisation of the manchette architecture and its role as transport scaffold using cryo-electron tomography.

The development of correctly shaped sperm cells is crucial for male reproductive health and fertility. The manchette is a transient microtubule-based structure that assembles during spermiogenesis and contributes to sperm head shaping. Defects in the manchette can cause sperm deformations and subsequent infertility. Previous studies have suggested that the manchette acts as a cellular transport platform, distributing proteins and vesicles during spermiogenesis in a process known as intra-manchette transport. The manchette and intra-manchette transport are still poorly understood, as high-resolution imaging is missing. Here, we used cryo-electron tomography and proteomics to visualize the manchette and identify some of its transport components. We characterize the overall architecture of the manchette and show that its perinuclear ring thickens as the structure constricts. We observed for the first time dynein directly interacting with the manchette. We further find F-actin as single filaments and filament clusters intercalating with the manchette microtubules. Our results provide new insights into the manchette's architecture and potential role as a transport scaffold, highlighting its significance for the shaping of sperm cells during spermiogenesis.