Expression of MAEL in nuage and non-nuage compartments of rat spermatogenic cells and colocalization with DDX4, DDX25 and MIWI.

The functions of MAELSTROM protein (MAEL) in spermatogenesis are gradually being identified but the precise distribution of MAEL in spermatogenic cells during spermatogenesis has not yet been mapped. We studied the expression of MAEL in rat testis by immunofluorescence and immunoelectron microscopy (IEM). Immunofluorescence staining showed that MAEL was localized in intermitochondrial cement, irregularly-shaped perinuclear granules and satellite bodies of pachytene spermatocytes, and in chromatoid bodies of spermatids. The SBs appeared exclusively in pachytene spermatocytes at stages IX-X and were stained strongly for MAEL. In step 12-19 spermatids, many granules stained for MAEL but not DDX4. These granules were confirmed to be non-nuage structures, including mitochondria-associated granules, reticulated body, granulated body by IEM. In the neck region of late spermatids and sperm, MAEL-positive small granules were found. MAEL is colocalized with MIWI in nuage and non-nuage. The results suggest that MAEL seems to function in nuage and non-nuage structures and interacts with MIWI.