Germ Cell Membrane Research Articles

Stage-specific expression of three cell surface carbohydrate antigens during murine spermatogenesis detected with monoclonal antibodies

We have identified three germ cell surface carbohydrate antigens that exhibit a common, stage-specific pattern of expression during spermatogenesis in the mouse. IgM-class monoclonal antibodies designated “J1,” “C6,” and “A5” were absorbed by adult testis, but not by any adult somatic tissue tested. In indirect immunofluorescence assays using collagenase-dissociated prepuberal and adult testicular cells, these antibodies labeled the surfaces of early and late pachytene spermatocytes and round spermatids. Gonocytes from fetal and neonatal testes were not labeled. In paraffin sections of prepuberal and adult testes, sialidase treatment exposed antigens recognized by antibodies C6 and A5 on preleptotene, leptotene, and zygotene spermatocytes located near the perimeter of seminiferous tubules. The determinants recognized by antibodies J1, C6, and A5 were characterized partially using a sugar hapten inhibition assay. The binding of J1 to adult testicular cells was inhibited specifically by N-acetylglucosamine and the binding of both C6 and A5 was inhibited by N-acetyllactosamine. The glycoconjugates recognized by J1, C6, and A5 eluted from gel filtration columns with an apparent molecular weight > 1 × 10 6 and were sensitive to endo-β-galactosidase (keratanase) treatment. The apparent high molecular weight of these glycoconjugates was confirmed by immunolabeling Western blots of testis extracts separated by SDS-polyacrylamide gel electrophoresis. The results suggest that polylactosamine (keratan) glycoconjugates of high molecular weight are associated with the plasma membranes of meiotic and haploid male germ cells. The effects of sialidase on antibody labeling patterns suggest that changes in cell surface sialylation accompany the transition of early meiotic germ cells to pachytene spermatocytes during spermatogenesis.

Lamellar germ cell processes: structures for possible interaction between germs cells and Sertoli cells during spermatogonial differentiation and early meiotic prophase.

The recent finding of a stage-dependent topographical relationship of basally located germ cells to Sertoli-Sertoli interspaces in the rat testis ( Ulvik 1983a ) has suggested a focal interaction between Sertoli cells and early germ cells at the sites where 2 Sertoli cells meet over a basal germ cell. Focal, stage-dependent interaction between Sertoli cells and germ cells may require specializations of the germ cell membrane. Therefore, in the present work the surface of spermatogonia and spermatocytes has been studied under the electron microscope throughout the cycle of the seminiferous epithelium. Lamellar processes, 1-3 micron long, were found to emerge from germ cells and protrude into the spaces between the overlying Sertoli cells. The processes appeared on differentiating type A spermatogonia after stage VI, on intermediate and type B spermatogonia, and on leptotene, zygotene, and early pachytene spermatocytes; however, they were not found on type A spermatogonia prior to stage VII or on preleptotene spermatocytes at stage VII. The lamellar processes are thus stage-specific and may be sites of focal interaction with the Sertoli cells. Since the cell processes always protrude into the Sertoli-Sertoli interspaces this finding supports the hypothesis of focal, stage-dependent interaction between early germ cells and Sertoli cells via the narrow Sertoli-Sertoli interspaces.

Cell to cell relationships in the seminiferous epithelium in the mouse embryo.

Germ cells and Sertoli cells in embryonic mouse testes (day 14 to 20 of gestation) were examined by sectioning and freeze-fracture. Intercellular cytoplasmic bridges between the germ cells are observed in day 14 and older embryos. Membrane specializations with dense fuzzy material similar to the so-called "desmosome-like structures" are found between Sertoli cells and germ cells. A cell contact area with dense opposed membranes is also found between adjacent germ cells. Asymmetrical dense fuzzy lining of both Sertoli and germ cell membranes is noted. Pinocytotic pits or caveolae are frequently found in the Sertoli cell membrane. Between adjacent Sertoli cells, gap junctions of various sizes and focal meshworks of the occluding junctions are found. Most of the occluding junctional particles are located in the center of the grooves in the E face, and are similar to those in postnatal and adult Sertoli cell junctions. In addition, on both fractured faces there are ridges and grooves devoid of particles which are continuous with occluding junctions with particles, suggesting an initial stage in the formation of occluding junctions of the Sertoli cells. Particles gathered at the site of desmosome-like structures are present on the P face of the Sertoli cell.

Intercellular junctional complexes of the rat seminiferous tubules: a freeze-fracture study.

This paper provides a description of the intercellular junctions in the rat testis, as observed using the freeze fracture technique. These intercellular junctions were categorized into four general types: Sertoli cell tight junctions, myoid cell tight junctions, gap junctions, and "heterogeneous junctions." The Sertoli cell tight junctions had a mean depth of 3.1 micron in the basal to apical direction, and contained 25 to 50 (average: 36) parallel rows of particulate sealing elements. The myoid cell tight junction was neither continuous nor extensive, but focal in nature. Interestingly the sealing elements of this junction, like those of the Sertoli cell tight junction, were quite particulate in nature. Typical gap junctions were observed between Sertoli cells where they were intercalated between the parallel rows of the Sertoli cell tight junction. The most interesting observation was the identification of gap junction-like structures, in various stages of formation, on germ cell membrane fracture faces, both in the basal and adluminal compartments. Lastly, the unusual "heterogeneous junction" was observed on large membrane fracture faces in close proximity to cells in the adluminal compartment, presumably between Sertoli cells. These junctions appeared to consist of both tight and gap junction elements.

Polar granules of Drosophila. 3. The continuity of polar granules during the life cycle of Drosophila.

AbstractPolar granules of Drosophila embryos fragment into fibrous bodies which become associated with the nuclear envelope of pole cells prior to the formation of the embryonic gonad. Similar fibrous structures are found attached to the outer nuclear membrane of primordial germ cells and oogonia throughout the life cycle of the fly. These structures have not been found in any other cell type except the germ cell of the testis. During oogenesis, the oocyte nucleus loses the fibrous bodies associated with the nuclear membrane, but the 15 sister nurse cells retain these structures until the end of vitellogenesis. At this time the cytoplasm and fibrous bodies of the nurse cells are contributed to the ooplasm. Occasionally, polar granules are found in previtellogenic stages of oogenesis, but they only accumulate at the posterior tip of the egg during the latter portion of vitellogenesis. After polar granules have formed, they attach to mitochondria in three species studies, but fail to form this association in D. hydei. Fibrous structures in the egg, believed to be the fibrous bodies attached to the nuclear envelope of nurse cells, are found throughout the mature egg, and have the same species‐specific property of associating or not with mitochondria as was found for polar granules. These fibrous bodies are no longer found following fertilization. A possible role of these fibrous bodies in the egg is discussed.