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

Abstract

Summary ― The histones H2B, H3 and H4, the transition protein TP1 and protamine were localised using ultrastructural immunocytochemistry in nuclei of rabbit spermatids and spermatozoa. Histones are present in round spermatid nuclei and are lost during the elongation of nuclei. TP1 and protamine appear simultaneously in all nuclei during this period. TP1 is located at the periphery of chromatin cords, while protamine seems to be located at random in the same cords. TP1 is lost in most elongated spermatids during step 13 of spermiogenesis, and the protamine stays in all sperm nuclei. TP1 remains present in some old spermatids and ejaculated spermatozoa. In the rabbit, 3-6% of sperm nuclei decondense spontaneously.

Novel Aspect of Perinuclear Theca Assembly Revealed by Immunolocalization of Non-Nuclear Somatic Histones During Bovine Spermiogenesis1

“…These modifications have been proposed to be the mechanism for histone-chromatin dissociation and eventual histone degradation. The absence of histone immunodetection in spermatid nuclei from late step 11 and beyond also concur with immunolocalization studies performed in several species [35,36].…”

Are there molecules of nucleoprotamine?

“…1) and possibly of nucleosomes and phosphorylases could be imaged as an instrument for setting free the consecutive binding sites for a following protamine molecule. Transition proteins have been shown to be located close to the external surface of the growing chromatin threads (62) in agreement with our model. It must be borne in mind that phosphorylated protamines are used for building the DNP, (51) whereas hyperacetylation is used to remove somatic histones.…”

Expression of mammalian spermatozoal nucleoproteins

“…The pattern of protamine deposition is roughly identical in all the mammals studied. A detectable amount of protamine is present in elongated spermatids at step 12 in the mouse (Biggiogera et al, 1992), step 10 in the rabbit (Courtens et al, 1995), step 12 in the ram (Courtens et al, 1983), step 10 in the boar (Courtens et al, 1988), and steps 4 -5 in man (Roux et al, 1987(Roux et al, , 1988Lescoat et al, 1993;Le Lannic et al, 1993;Prigent et al, 1996). Immunoelectron microscopic data indicate that the human proprotamine pHP2 (previously named HPI1) is synthesized in large amounts in spermatids during the elongation phase.…”