Rôles indirects des microtubules dans la morphogenèse nucléaire des spermatides

Abstract

Summary. The indirect roles of microtubules in the nuclear morphogenesis of spermatids.The depolymerization of the microtubules of the spermatid manchette was effective for 4 to 5 h in rat, starting 30 min after one intratesticular injection of colcemid in vivo. The manchette built up again later was normal in old elongating spermatids but very oddly shaped in young elongating spermatids in which the nuclear shape was abnormal and the relations between the nucleus and the endoplasmic reticulum aberrant, ie destruction of the apparatus for nucleocytoplasmic exchange. From 24 to 96 h after the injection, a progressive shifting of the cellular associations indicated that young spermatids elongating at the time of injection did not differentiate further. This could result from the lack of two roles not played by the new manchette : the guiding effect of the intranuclear chromatin and the role of skeleton for the cytoplasmic apparatus devoted to nucleocytoplasmic exchange.Step 14 to 16 spermatids were not modified by the removal of the manchette due to correct reformation of a typical manchette 4 to 5 h later. The associations of the microtubules and the nuclei and the speculative roles of the microtubules during spermiogenesis have been discussed.Introduction.

Nuclear morphogenesis during spermiogenesis in the nudibranch molluscHypselodoris tricolor (Gastropoda, opisthobranchia)

“…Besides, between the microtubules and the peripheral chromatin the perinuclear space is very small, which is consistent with the idea that there is a close interaction between the microtubules and the interior of the nucleus. The parallel orientation of microtubules and adjoining chromatin fibers strengthens this hypothesis and supports the theory of Courtens [1982], who attributes to the manchette the role of guiding the chromatin. Wilkinson et a1 [1974, 19751 andStanley et a1 [1972] likewise ascribe to the microtubules an important function in the specific pattern of chromatin condensation.…”

Le cytosquelette des gamètes mobiles des végétaux

“…Plusieurs auteurs ont supposé que la couche S 1 pouvait intervenir dans la circulation antéro-postérieure d'éléments synthétisés à un des pôles du gamète, métabolites ou molécules informatives (Kreitner, 1977;Courtens, 1982); pour certains (Moestrup, 1982) les microtubules correspondraient à la voie par laquelle est transmise au corps cellulaire l'information perçue au niveau des flagelles lorsque les gamètes arrivent au contact (Goodenough et Weiss, 1978 ;Lovlie et Bryhni, 1976).…”

Ultrastructural immunolocalisation of histones (H2B, H3, H4), transition protein (TP1) and protamine in rabbit spermatids and spermatozoa nuclei. Relation to condensation of the chromatin

“…In vitro, TP1 induces a pronounced equilibrium destabilisation of the DNA (Singh and Rao, 1987). In vivo, protamine can fix the chromatin structure, whatever the step at which it is introduced to nuclei and whatever the previous local arrangement of chromatin (Courtens, 1982;Biggiogera et al, 1992). The fact that TP1 is located at the periphery of threads, and seems to remain in that place, forming longitudinal decorations in older spermatids, may indicate that it is involved in the formation of the chromatin plates which are present in old spermatids and spermatozoa (Koehler, 1970;Courtens et al, 1991 This raises the question of how it is eliminated, meaning separation from the DNA and release from the dense chromatin.…”