ABSTRACT
Spermatogenesis is highly dynamic and precisely controlled in space and time and is accompanied by extraordinary changes in each cell's cytoskeleton. This chapter provides an overview of the actin cytoskeleton in spermatogenesis, highlighting the role of actin dynamics in particular processes in the seminiferous epithelium. After the last meiotic division, haploid spermatids enter spermiogenesis as small, round, very transcriptionally active cells, yet they finish the process as long, transcriptionally inert spermatozoa with dense, characteristically shaped nuclei and long flagella capable of motility. Filamentous-actin tends to be concentrated at intercellular junctions between adjacent Sertoli cells where they contribute to the blood-testis barrier, and at junctions between Sertoli cells and elongating spermatids prior to their release from the epithelium at spermiation. The Sertoli cell ectoplasmic specialization consists of a layer of hexagonally packed actin filaments recognizable by electron microscopy located between the plasma membrane and a cistern of endoplasmic reticulum.
