Inhibition of autophagy impairs acrosome and mitochondrial crista formation during spermiogenesis in turtle: Ultrastructural evidence

Autophagy is a subcellular process that is extensively involved in spermiogenesis. In this study, we observed ultrastructural malformation of acrosome and mitochondrial cristae during the spermiogenesis of Chinese soft-shelled turtle due to the inhibition of autophagy. Autophagy was blocked with 3-MA, and the inhibition of autophagy was confirmed through western blot analysis. The morphological abnormalities of acrosomes and mitochondria were observed under transmission electron microscopy (TEM). In the early spermiogenesis (Golgi and cap phases), damaged macrovesicle was observed, and its proper expansion over the nucleus failed to be form a normal acrosomal cap. As spermiogenesis proceeded, the malformation of the acrosome in spermatids became more severe. In the late spermiogenesis (acrosomal and maturation phases), defective acrosome with damaged acrosomal membrane that was detached from the nucleus was observed. Along with malformed acrosome, elongation failed nucleus having oval or round shaped morphology was also observed. Moreover, morphological damage to the mitochondrial cristae was observed. Lacuna formation, half and complete loss of cristae were observed in the mitochondria of developing spermatids. We proposed that autophagy is required for normal formation of the acrosome and mitochondrial cristae during turtle spermiogenesis.