Basic nuclear protein pattern and chromatin condensation in the male germ cells of a tropical abalone,Haliotis asinina

Morphological and biochemical alterations of abalone testicular germ cells and spawned sperm and their fertilizing ability

In this study, we aimed to detect morphological and biochemical changes in developing germ cells (Gc), testicular sperm (Tsp), and spawned sperm (Ssp) using capacitation-associated characteristics. Gradual changes in the profiles of two membrane proteins, namely NaCl- and detergent-extractable proteins, were observed as compared Gc with Tsp and Tsp with Ssp. These membrane modifications were accomplished mostly through the introduction of new protein sets, both peripheral and integral, into Tsp and Ssp membranes. Activation of serine proteases, particularly in Ssp detergent-extracted proteins with the molecular masses of 38-130 kDa was evident and marked a major difference between Ssp and Tsp. An increase in the level of tyrosine phosphorylation of the proteins ranging from 15 to 20 kDa was noted in Tsp and remained constant in Ssp. Specifically, these three capacitation-associated characteristics could be detected in Ssp, possessing full fertilizing capacity. The lack of an activated proteolytic activity in Tsp resulted in a delayed fertilization, but not affected fertilizing ability. We believe that these characteristics should be advantageous in predicting abalone sperm fertilizing capability, particularly in cases when isolated germ cells or purified Tsp are used in place of spawned sperm in abalone aquaculture.

Spermiogenesis and chromatin condensation in the common tree shrew, Tupaia glis

We have investigated the cellular characteristics, especially chromatin condensation and the basic nuclear protein profile, during spermiogenesis in the common tree shrew, Tupaia glis. Spermatids could be classified into Golgi phase, cap phase, acrosome phase, and maturation phase. During the Golgi phase, chromatin was composed of 10-nm and 30-nm fibers with few 50-nm to 60-nm knobby fibers. The latter were then transformed into 70-nm knobby fibers during the cap phase. In the acrosome phase, all fibers were packed into the highest-order knobby fibers, each about 80-100 nm in width. These chromatin fibers became tightly packed in the maturation phase. In a mature spermatozoon, the discoid-shaped head was occupied by the acrosome and completely condensed chromatin. H3, the core histone, was detected by immunostaining in all nuclei of germ cell stages, except in spermatid steps 15-16 and spermatozoa. Protamine, the basic nuclear protein causing the tight packing of sperm chromatin, was detected by immunofluorescence in the nuclei of spermatids at steps 12-16 and spermatozoa. Cross-immunoreactivity of T. glis H3 and protamine to those of primates suggests the evolutionary resemblance of these nuclear basic proteins in primate germ cells.

Transition of nuclear proteins and chromatin structure in spermiogenesis of Sepia officinalis

During spermiogenesis of Sepia officinalis histones are directly substituted by a molecule of precursor protamine, which is later transformed into the protamine through a deletion of the amino terminal end. In the present work, it is shown that the pattern of spermiogenic chromatin condensation consists of a phase of "patterning" and a phase of "condensation." In the phase of patterning, three structural remodelings are produced in the chromatin structure: [somatic-like chromatin --> 18 nm granules --> 25 nm fibers --> 44 nm fibers]. The first remodeling of the chromatin into granules of 18 nm takes place without the entrance of specific proteins in the spermiogenic nuclei. The second remodeling [granules of 18 nm --> fibers of 25 nm] is due to the entrance of the precursor protamine and its interaction with the DNA-histone complex. The third remodeling [fibers of 25 nm --> fibers of 44 nm] occurs simultaneously with the disappearance of histones from the chromatin. In the phase of condensation, the fibers of 44 nm coalesce among themselves to form progressively larger aggregates of chromatin. In this phase there are no substantial variations in the nuclear proteins, so that the condensation of the chromatin must respond to posttranscriptional changes of the precursor protamine (dephosphorylation, deletion of the amino-terminal end).

Immunohistochemical distribution of hyperacetylated histone H4 in testis of paddlefish Polyodon spathula: ultrastructural correlation with chromatin condensation

The acetylation of core histones has been correlated with the deposition of free histones onto newly replicated DNA, transcriptional activity and the displacement of histones by protamines during spermiogenesis. The aim of the present study was to investigate the immunohistochemical distribution of hyperacetylated H4 during spermatogenesis in Polyodon spathula and to correlate these findings with the pattern of chromatin condensation in spermatids. In immature testis, the Sertoli cells showed more intense immunoreactivity for highly acetylated H4 than that of most primary spermatogonia. The testis of paddlefish at the beginning of spermatogenesis possessed early secondary spermatogonia and late secondary spermatogonia/preleptotene primary spermatocyte with intense nuclear immunoreactivity for highly acetylated H4. In seminiferous tubules in which secondary spermatogonia nuclei were intensely immunostained, Sertoli cell nuclei were unstained. Testes in late spermatogenesis contained tubules in which the immunohistochemical reaction for highly acetylated H4 was positive in the nuclei of preleptotene primary spermatocytes and secondary spermatocytes and in spermatids at the beginning of the elongation process. No immunostaining was found in round spermatids and spermatozoa. During the resting stage, immunostaining was confined to the nuclei of spermatogonia and the cells from the interstitial tissue. Transmission electron microscopy revealed that early spermatids had a round nucleus with filaments of fine chromatin that were dispersed or condensed in clumps. In later stages of maturation, the spermatids had slightly oval nuclei and homogeneous granular chromatin. The chromatin of advanced spermatids was organized into thick fibres. At the end of spermiogenesis, spermatozoan nuclei consisted of homogeneous highly compacted chromatin.