In areas of Sertoli cell crypts attached to the heads of elongate spermatids occurs a unique class of actin-related adhesion junctions termed ectoplasmic specializations. These structures each consist of the plasma membrane in regions adherent to the spermatid head, a cistern of endoplasmic reticulum, and an intervening layer of hexagonally packed actin filaments. The three elements of the plaque occur as a structural unit that remains attached to the spermatid when the latter is mechanically separated from the epithelium. In vivo, the endoplasmic reticulum component of the plaque is related, on its cytoplasmic face, to microtubules.
Microtubules are prominent elements of the Sertoli cell cytoskeleton. They surround apical crypts containing elongate spermatids, are generally arranged parallel to the axis of spermatid translocation, and have their positive ends positioned at the base of the epithelium. buy yasmin online
Our working hypothesis of spermatid translocation is that motor proteins are anchored to the cytoplasmic face of the endoplasmic reticulum component of ectoplasmic specializations and that they move the junction plaques, and therefore the attached spermatids, along Sertoli cell microtubule tracts. The nature of the putative motor proteins involved in transport of the spermatid/junction complexes along microtubules is as yet unknown.