Presence of RNA in the sperm nucleus

Expression of the platelet-activating factor receptor in human spermatozoa: differences in messenger ribonucleic acid content and protein distribution between normal and abnormal spermatozoa

OBJECTIVE

To determine the expression and distribution of the platelet-activating factor (PAF) receptor in normal and abnormal specimens of human spermatozoa.

DESIGN

Prospective analysis of membrane-bound PAF receptors by immunofluorescence and PAF receptor messenger RNA by quantitated reverse transcription-polymerase chain reaction in normal and abnormal spermatozoa.

SETTING

University-based reproductive genetics laboratory.

PATIENT(S)

Men undergoing routine semen analysis.

INTERVENTION(S)

Normal and abnormal spermatozoa were exposed to rabbit anti-PAF receptor antibody, fluorescein isothiocyanate-conjugated goat anti-rabbit antibody, and fluorescent microscopy or subjected to RNA isolation by acid-phenol extraction and quantitated (MIMIC Construction Kit [Clontech Laboratories, Inc., Palo Alto, CA]) reverse transcription-polymerase chain reaction.

MAIN OUTCOME MEASURE(S)

Fluorescent intensities at six locations along spermatozoa (end piece, principal tail, midpiece, neck, proximal head, and acrosomal region) and PAF receptor expression (messenger RNA) levels.

RESULT(S)

Immunofluorescence demonstrated a significant difference in PAF receptor distribution between normal and abnormal human spermatozoa, specifically at the neck region. Additionally, abnormal spermatozoa were found to have statistically significantly more PAF receptor messenger RNA than normal spermatozoa.

CONCLUSION(S)

Platelet-activating factor receptor expression and distribution are significantly altered in abnormal spermatozoa and this may be the result of some defect in gene transcription.

Presence of ribonucleic acid in human spermatozoa: differences in content between normal and abnormal spermatozoa

OBJECTIVE

Our purpose was to determine whether there are any differences in total ribonucleic acid content between normal and abnormal human spermatozoa.

STUDY DESIGN

Spermatozoa were obtained from men undergoing routine semen analysis at a university-based reproductive genetics laboratory. Specimens were classified as normal or abnormal according to World Health Organization criteria. Total ribonucleic acid was removed by acid-phenol extraction, and ribonucleic acid expression levels were determined by spectrophotometric analysis.

RESULTS

Abnormal spermatozoa were found to have significantly more ribonucleic acid (0.14 +/- 0.02 mg/10(6) spermatozoa) than normal spermatozoa (0.05 +/- 0.01 mg/10(6) spermatozoa; P <.001).

CONCLUSION

Ribonucleic acid content is significantly altered in abnormal spermatozoa, and this alteration may be the result of some defect in the posttranscriptional pathway.

Expression of protamine-1 and -2 mRNA during human spermiogenesis

During spermiogenesis, the histone-to-protamine replacement causes the compaction of the spermatid chromatin. The genes for protamines, PRM-1 and PRM-2, are transcribed in round and elongating spermatids. The transcripts are stored in a translationally-repressed state by the binding of protein repressors before being translated in elongating and elongated spermatids. RNA extracts from homogenized whole testis samples supply only average data, and cell-specific and stage-specific expression cannot be addressed. Therefore, we used UV-laser-assisted cell-picking (UV-LACP) to select spermatids of defined differentiation steps. Subsequent reverse transcription-polymerase chain reaction (RT-PCR) with intron-spanning primer pairs allowed the detection of DNA-free and pseudogene-free PRM-1 and PRM-2 cDNA. Additional in-situ hybridization with digoxygenin-labelled cRNA probes exhibited PRM-1 and PRM-2 mRNA from step 1/2 spermatids to step 4 spermatids, but not in elongated spermatids. RT-PCR revealed amplicons for PRM-1 and PRM-2 in all spermatids except step 3 round spermatids. Applying proteinase K digestion, PRM-1 and PRM-2 transcripts were also detected in step 3 spermatids indicating that protein repressors may bind to both PRM-1 and PRM-2 mRNA in step 3 round spermatids. These data demonstrate that the combination of UV-LACP and non-radioactive in-situ hybridization appear to be a suitable approach for the study of cell-specific and stage-specific gene expression during spermiogenesis.

Effect of actinomycin D and cycloheximide on human sperm function

The effects of actinomycin D and cycloheximide on human spermatozoal function were examined to investigate the potential transcriptional and translational activities of human sperm cell during capacitation/acrosome reaction. Treatment with actinomycin D significantly increased and treatment with cycloheximide decreased the acrosome reaction, and the penetration rates in the human sperm penetration of zona-free hamster oocytes assay (SPA). [35(S)]Methionine got incorporated into 3-9 de novo synthesized proteins present in the head and midpiece regions of the swim-up population of human sperm. Treatment with actinomycin D completely blocked and treatment with cycloheximide slightly reduced the synthesis of proteins. There seem to be some transcriptional and translational activities in the head and midpiece regions of human sperm during capacitation/acrosome reaction.

The nuclear status of human sperm cells

In the last decade, and in particular since the development of in vitro fertilization techniques, the nuclear status of human sperm cells has shown to be a key parameter in the assessment of male fertility. The shape and condensed state of the mature sperm nucleus are determined by structural and functional events that occur during spermiogenesis. This paper reviews essential findings on re-organization of the nucleus during sperm differentiation and maturation, and reports recent data on the architecture, biochemical composition and stability of the nucleus in human ejaculated spermatozoa. Different methods used to evaluate nuclear maturity in relation to male fertility are critically appraised.

A cytochemical study of the nucleolus and nucleolus-related structures during human spermatogenesis

Besides the components of typical nucleoli, three other nuclear structures were identified in spermatogonia by positive silver staining: dense centers, fibrillar regions, and dense granules. There was a close relationship between the dense centers and fibrillar regions in spermatogonia and spermatocytes, whereas the dense granules, which appeared dispersed throughout the nucleoplasm of spermatogonia, became localized at the periphery of chromosomes in spermatocytes. From the beginning of spermiogenesis, these three structures then appeared in direct relationship with the dense fibrillar component of the nucleolus. At the Golgi phase, a new nuclear structure also appeared in close relationship with the dense fibrillar component. As it was morphologically similar to the fibrillar region, but not silver stained, it was designated fibrillar structure. With further spermatid development, as the dense fibrillar component gradually disappeared, a sharp increase in the number of the associated dense granules was observed; these granules then disappeared as well. In spermatids at cap phase, each fibrillar region appeared intimately associated with several fibrillar structures. In maturing spermatids, silver staining became confined to the fibrils that appeared located inside the nuclear vacuole. The nuclear vacuole also contained a dense fibrillar structure in intimate relationship with these fibrils and the peripheral condensed chromatin. Ethidium bromide-PTA, Na-tungstate and EDTA regressive staining suggest the presence of RNP in the fibrillar regions, dense granules and intravacuolar fibrils, and the presence of DNP in the fibrillar structures.

Nuclear Sm antigens in the sperm of different organisms

Immunoblot analysis of sperm protein from several species revealed the presence of polypeptides recognised by anti-Sm sera obtained from patients with systemic lupus erythematosus. Immunoreactive polypeptides in human, bull, mouse and rat sperm were identified as protein B', B and D as compared with the Sm polypeptides of HeLa cells. In the sperm of rooster, the teleost fish Cyprinus carpio and the mussel Choromytilus chorus, the immunoreactive polypeptide profile was more complex. To ascertain the sperm origin of the Sm antigens, immunolocalisation with anti-Sm serum was carried out. The results demonstrated that in all the species studied staining was confined to the sperm nucleus, confirming that some polypeptides of the small nuclear ribonucleoprotein complex are present in the gamete.

Small nuclear ribonucleoprotein polypeptides in rat sperm

1. Immunoblot analysis of rat sperm head proteins revealed the presence of polypeptides recognized by anti-Sm serum obtained from patients with systemic lupus erythematosus. 2. Two of these polypeptides have molecular weights of 26,000 and 15,000 and they were identified as small nuclear ribonucleoprotein components present in other rat tissues. 3. When the autoimmune serum was used in the immuno-gold procedure for electron microscopy, gold particles were found only on the sperm nucleus. 4. The results indicate that some polypeptides of the small nuclear ribonucleoprotein complex are components of the rat sperm chromatin.

Cytochemical variations in the nucleolus during spermiogenesis in man and monkey

The fine structure, nature and fate of the components of the nucleolus were studied in young (steps 1, 2), intermediate (steps 3, 4, 5) and mature spermatids (steps 6, 7, 8) of man and monkey, by use of several cytochemical techniques (alcoholic PTA; sodium tungstate: EDTA; HAPTA; nuclease-gold complexes; NOR silver staining). As controls, comparative ultrastructural and cytochemical observations of the nucleolus in spermatids and Sertoli cells were made in the same sections of seminiferous tubules. In the young spermatids of the two species studied, the nucleolar masses exhibited identical features. Segregation of the nucleolar components took place in the nuclei of step 1 spermatids. No typical fibrillar center was observed. In spermatids at steps 1 and 2, the nucleolar masses appeared to be made up of two fibrillar components of equal density, one spherule-shaped, the other forming cords, both surrounded by clusters of 15-20 nm-diameter granules. Alcoholic PTA and sodium tungstate yielded a selective positive contrast of the two fibrillar components whereas EDTA and RNase-gold reacted with the peripheral granular material. Treatment with RNase-gold and DNase-gold complexes resulted in preferential labeling at the periphery of the fibrillar components. After NOR silver staining, numerous small silver grains were localized over the fibrillar cords, suggesting the persistence of specific acidic non-histone proteins. On the contrary, the spherule was never stained. In intermediate spermatids, when the nucleolar components were dissociated, scattered clusters of granules stained by EDTA and HAPTA remained in the entire nucleoplasm. Nucleolar disintegration was accompanied by dispersion of argyrophilic material.(ABSTRACT TRUNCATED AT 250 WORDS)