Sertoli cell processes have axoplasmic features: an ordered microtubule distribution and an abundant high molecular weight microtubule-associated protein (cytoplasmic dynein).

Abstract

Abstract. Microtubules in the cytoplasm of rat Sertoli cell stage VI-VIII testicular seminiferous epithelium were studied morphometrically by electron microscopy. The Sertoli cell microtubules demonstrated axonal features, being largely parallel in orientation and predominantly spaced one to two microtubule diameters apart, suggesting the presence of microtubule-bound spacer molecules. Testis microtubule-associated proteins (MAPs) were isolated by a taxol, salt elution procedure. Testis MAPs promoted microtubule assembly, but to a lesser degree than brain MAPs. High molecular weight MAPs, similar in electrophoretic mobilities to brain MAP-1 and MAP-2, were prominent components of total testis MAPs, though no shared immunoreactivity was detected between testis and brain high molecular weight MAPs using both polyclonal and monoclonal antibodies. Unlike brain high molecular weight MAPs, testis high molecular weight MAPs were not heat stable. Testis MAP composition, studied on postnatal days 5, 10, 15, and 24 and in the adult, changed dramatically during ontogeny. However, the expression of the major testis high molecular weight MAP, called HMW-2, was constitutive and independent of the development of mature germ cells. The Sertoli cell origin of HMW-2 was confirmed by identifying this protein as the major MAP found in an enriched Sertoli cell preparation and in two rat models of testicular injury characterized by germ cell depletion. HMW-2 was selectively released from testis microtubules by ATP and co-purified by sucrose density gradient centrifugation with MAP-1C, a neuronal cytoplasmic dynein. The inhibition of the microtubuleactivated ATPase activity of HMW-2 by vanadate and erythro-(2-hydroxy-3-nonyl)adenine and its proteolytic breakdown by vanadate-dependent UV photocleavage confirmed the dynein-like nature of HMW-2. As demonstrated by this study, the neuronal and Sertoli cell cytoskeletons share morphological, structural and functional properties.

Testicular cell cytoskeleton in the newt,Triturus marmoratus marmoratus, during the annual cycle

“…Electron microscopic studies of mammalian testes have revealed that the Sertoli cell contains abundant microtubules which are parallelly arranged along the major cell axis (Neely and Boekelheide, 1988). Other parallel arrays of microtubules run from the nucleus towards the cytoplasmic crypts that surround spermatids (Amlani and Vogl, 1988;Russell, 1977).…”

Preparation of microtubules from rat liver and testis: Cytoplasmic dynein is a major microtubule associated protein

“…As was found here for cytoplasmic dynein, Tetrahymena ciliary dynein exhibits a much higher Km for CTP than that for ATP [Shimizu, 19871. Our results indicate that the characteristics of brain cytoplasmic dynein that distinguish it from axonemal dyneins are common to other forms of cytoplasmic dynein as well. These characteristics should serve as a basis for comparison with other high molecular weight ATPases that have at least some of the properties we have reported for brain cytoplasmic dynein [Pallini et al, 1983; Hollenbeck and Chapman, 1986; Gilbert and Sloboda, 1986;Pratt, 1986; Lye et al, 1987;Euteneuer et al, 1988; Neely and Boekelheide, 1988). The same characteristics should also be useful diagnostically to distinguish true cytoplasmic dyneins from soluble forms of axonemal dynein.…”

Testicular histopathology associated with disruption of the Sertoli cell cytoskeleton

“…1,2 For structural support, the Sertoli cell cytoplasmic stalk and apical extensions contain numerous microtubules oriented parallel to the Sertoli cell long axis. 9,10 This pattern also allows the Sertoli cell microtubules to function as a platform upon which microtubule motors attach to specialized Sertoli-spermatid adhesion junctions (ectoplasmic specializations) and move elongating spermatids within the seminiferous epithelium along the Sertoli cell apicobasal axis. 11,12 Other functions ascribed to Sertoli cell microtubules include secretion of seminiferous tubule fluid, 13 intracellular movement of germ cell residual bodies from the apical to basal Sertoli cell subcellular compartments, 14,15 and release of mature spermatids from the seminiferous epithelium (spermiation).…”