Pattern of silver nitrate-staining during meiosis and spermiogenesis in testicular lobes of Antiteuchus tripterus (Heteroptera: Pentatomidae)

The pattern of silver nitrate (Ag)-staining differed among testicular lobes of Antiteuchus tripterus. In general, these differences are in regard to the number, size, shape, coloring intensity, and location of the stained bodies or masses, observed during meiosis and spermiogenesis. These characteristics were similar in lobes 1-3. Lobes 4-6, however, differed from each other and from lobes 1-3 as well. Because the Ag-staining method is specific for nucleolar organizing regions and nucleolar material, the observations in meiosis of lobes 1-3 suggested the presence of a single pair of nucleolar organizing region-bearing chromosomes in A. tripterus, as previously found in other Pentatomidae species. In general, the amount of Ag-stained material seen in meiosis of the testicular lobes 1-3 of A. tripterus is smaller than in the other lobes. The differences among lobes observed during spermiogenesis included a striking variation in morphology of the Ag-stained material found in the head and tail of the spermatids. Given that the key role of the nucleolar material is to participate in protein synthesis, interlobular variations seem to be related to the different functions attributed to each lobe (reproduction to lobes 1-3 and basically nutrition to lobes 4-6). To our knowledge, this is the first time that the nucleolar material was studied in each testicular lobe during spermatogenesis. The present observations encourage further studies since, in addition to being of basic biological interest, several Pentatomidae species are agricultural pests and added knowledge of their biology, mainly in reproduction, may be important for the development of control strategies.     

Spermiogenesis in the rainbow trout (Salmo gairdneri)

In an ultrastructural study on the spermiogenesis of the rainbow trout (Salmo gairdneri R.) four spermatogenetic stages were identified. In young round spermatids, the nuclear chromatin was first heterogeneous (euchromatin and heterochromatin). Subsequently, it became more homogeneous and started to condense in the form of coarse granules and fibers and then into fibrils associated in ribbon-like elements which eventually partly fused together. During early spermiogenesis, a juxtanuclear vacuole appeared in the area where the nuclear envelope was specialized due to condensation of material between the two envelopes and a slight accumulation of nuclear material. This area was finally located in the anterior part of spermatids and spermatozoa; it probably plays a role during fertilization. A flagellar rootlet appeared early in spermiogenesis; it may play a role in the attachment of the flagellum to the nucleus since it persisted until the centriolar complex was definitively fixed in the implantation fossa. The flagellum did not display a plasma membrane and was first located in the cytoplasm, but when it was later extruded from the cell, it acquired a membrane. The cytoplasm was rich in ribosomes (free or in small groups) but poor in membranous organelles. The few mitochondria polarized around the centriolar complex were finally organized into an annular mid-piece. The spermatids remained connected by intercellular bridges until the end of spermiogenesis. The complexity of trout spermiogenesis is intermediate between that in poecilids and that in carp and pike, which have very simple spermatozoa. The role of the material from the nucleus and the cytoplasm reaching the Sertoli cell in the control of spermatogenesis has been discussed.     

Carbendazim-induced abnormal development of the acrosome during early phases of spermiogenesis in the rat testis

Effects of a single, high dose of orally administered carbendazim (100 mg/kg) on acrosome formation in the early phases of spermiogenesis were examined by electron microscopy and immunocytochemistry up to day 7.5 post-treatment. No obvious abnormality of acrosome development was noted in the Golgi phase spermatids on day 1.5 post-treatment. On day 3, step 1 spermatids were seen in stage III seminiferous tubules. In stage V tubules at this post-treatment interval, direct connections between the trans-side saccules of the Golgi stacks and the outer acrosomic membranes were observed in step 5 spermatids. Similar direct connections between these two organelles were also observed in the advanced round spermatids in later stages at days 4.5 and 7.5. On day 4.5, step 1 and 3 spermatids were seen in stage V tubules. On day 7.5, round spermatids with various abnormalities of acrosome development were observed in stage VII tubules, in addition to the discontinuous and granular acrosomes reported previously. These features were not observed in testes of control animals. In the immunocytochemical analysis using an antibody mMN7 that recognizes a protein delivered from the Golgi apparatus to the acrosome, spermatids exposed to carbendazim showed various abnormal immunostaining patterns in the acrosomes. On the other hand, strong immunoreactivity was observed in the Golgi saccules connecting to the acrosomes. These results suggest that in testis treated with carbendazim acrosome development is impaired during the early phases of spermiogenesis, and material supply from the Golgi apparatus to the acrosome is perturbed, which is a possible cause of the abnormal development. Received: 31 March 1998 / Accepted: 28 May 1998     

Ethanol-phosphotungstic acid and bismuth staining of spermatid nucleoli in mouse spermiogenesis.

The nucleoli of developing mouse spermatids were examined with ethanol-phosphotungstic acid (E-PTA) staining, and also with bismuth staining following formaldehyde fixation (FA-Bi staining) and glutaraldehyde fixation (GA-Bi staining). Only the cortical zone of the nucleolar dense fibrillar component (DFC) in the round spermatids was stained with E-PTA, while the inner area remained either faintly (early Golgi-phase spermatids) or completely unstained (cap-phase spermatids). Incubation of the fixed testis with dithiothreitol before E-PTA staining resulted in homogeneously intense staining of the DFC. The facts suggest that numerous E-PTA-positive basic proteins were present in the DFC, but disulfide crosslinks formed in the DFC proteins prevent penetration of PTA into the DFC interior. The DFC was stained with bismuth after FA-Bi and GA-Bi staining until the disappearance of the nucleoli occurring in acrosome-phase spermatids. The fibrillar center, homogeneously stained using E-PTA, FA-Bi, and GA-Bi methods was present in the nucleoli of Golgi-phase and early cap-phase spermatids, but disappeared in the nucleoli of late cap-phase spermatids. These results are discussed based on the previous studies dealing with the ribosomal RNA synthesis in mouse spermiogenesis.     

Meiotic chromosomes and nucleolar behavior in testicular cells of the grassland spittlebugs Deois flavopicta, Mahanarva fimbriolata and Notozulia entreriana (Hemiptera, Auchenorrhyncha)

Spittlebugs annually infest pastures and cause severe damage, representing a serious problem for the tropical American beef cattle industry. Spittlebugs are an important biotic constraint to forage production and there is a lack of cytogenetic data for this group of insects. For these reasons, we conducted this work, in which the spermatogenesis and nucleolar behavior of Deois flavopicta, Mahanarva fimbriolata and Notozulia entreriana were studied. The males possessed testes in the shape of a "bunch of grapes"; a variable number of testicular lobes per individual and polyploid nuclei composed of several heteropycnotic bodies. A heteropycnotic area was located in the periphery of the nucleus (prophase I); the chiasmata were terminal or interstitial; metaphases I were circular or linear and anaphase showed late migration of the sex chromosome. The chromosome complement had 2n = 19, except for N. entreriana (2n = 15); the spermatids were round with heteropycnotic material in the center and elongated with conspicuos chromatin. The analysis of testes after silver nitrate staining showed polyploid nuclei with three large and three smaller nucleolar bodies. Early prophase cells had an intensely stained nucleolar body located close to the chromatin and another less evident body located away from the chromatin. The nucleolar bodies disintegrated during diplotene. Silver staining occurred in two autosomes, in terminal and subterminal locations, the latter probably corresponding to the nucleolus organizer regions (NORs). The spermatids were round with a round nucleolar body and silver staining was observed in the medial and posterior region of the elongated part of the spermatid head.     

The differential expression of the actins and tubulins during spermatogenesis in the mouse

Following intratesticular injection of [35S]methionine, the multiple isoforms of actin and tubulin from highly purified mouse testicular meiotic and post-meiotic cells have been analysed by high resolution two-dimensional gel electrophoresis. In pachytene spermatocytes both beta and gamma actin are synthesized, gamma actin being made in a significantly greater amount. The relative proportion of synthesis of beta and gamma actin changes during spermiogenesis, beta actin increasing and gamma actin decreasing in round spermatids, elongating spermatids, and residual bodies. Both alpha and beta tubulin are synthesized in approximately equal proportion in pachytene spermatocytes. In addition to the tubulin isoforms synthesized during meiosis, at least one new form of both alpha and beta tubulin first appears in post-meiotic (haploid) cells. In elongating spermatids and residual bodies, the synthesis of alpha tubulin is drastically reduced.     

Characterization of Sptrx, a novel member of the thioredoxin family specifically expressed in human spermatozoa

Thioredoxins (Trx) are small ubiquitous proteins that participate in different cellular processes via redox-mediated reactions. We report here the identification and characterization of a novel member of the thioredoxin family in humans, named Sptrx (sperm-specific trx), the first with a tissue-specific distribution, located exclusively in spermatozoa. Sptrx open reading frame encodes for a protein of 486 amino acids composed of two clear domains: an N-terminal domain consisting of 23 highly conserved repetitions of a 15-residue motif and a C-terminal domain typical of thioredoxins. Northern analysis and in situ hybridization shows that Sptrx mRNA is only expressed in human testis, specifically in round and elongating spermatids. Immunostaining of human testis sections identified Sptrx protein in spermatids, while immunofluorescence and immunogold electron microscopy analysis demonstrated Sptrx localization in the cytoplasmic droplet of ejaculated sperm. Sptrx appears to have a multimeric structure in native conditions and is able to reduce insulin disulfide bonds in the presence of NADPH and thioredoxin reductase. During mammalian spermiogenesis in testis seminiferous tubules and later maturation in epididymis, extensive reorganization of disulfide bonds is required to stabilize cytoskeletal sperm structures. However, the molecular mechanisms that control these processes are not known. The identification of Sptrx with an expression pattern restricted to the postmeiotic phase of spermatogenesis, when the sperm tail is organized, suggests that Sptrx might be an important factor in regulating critical steps of human spermiogenesis.     

Immunohistochemical localization of a water channel, aquaporin 7 (AQP7), in the rat testis

Cell volume reduction is one of the most distinct morphological changes during spermiogenesis and may be largely attributable to water efflux from the cell. A strong candidate for a water efflux route, aquaporin 7 (AQP7), which is a water channel, was studied immunohistochemically in the rat testis. Immunoreactivity was restricted within the elongated spermatids, testicular spermatozoa, and residual bodies remaining in the seminiferous epithelium. Weak but distinct immunoreactivity was first observed in the cytoplasmic mass of the spermatid at step 8 of spermiogenesis. The Golgi-like apparatus became steadily immunoreactive at step 10. The plasma membrane covering the cytoplasmic mass showed strong immunoreactivity after step 16. At this step, the middle piece of the tail also showed immunoreactivity at the portion protruding into the lumen. The whole head and distal tail, where the elongated spermatid had only a limited amount of cytoplasm, showed no immunoreactivity throughout spermiogenesis. After spermiation, the immunoreactivity of AQP7 remained at the middle piece and in the cytoplasmic droplet in the testicular spermatozoon. The present observations suggest that AQP7 contributes to the volume reduction of spermatids, since this water channel protein is localized on the plasma membrane covering the condensing cytoplasmic mass of the elongated spermatid, and since the seminiferous tubule fluid is hypertonic.     

La spermatide, cette méconnue

The use of microinsemination of round or elongated spermatids into ovocytes, in certain cases of male infertility, requires re-examination of the sequence of morphological and functional changes that occur throughout spermiogenesis. This paper reviews essential findings on morphogenesis of spermatids, genome expression during sperm differentiation and cellular interactions between spermatids themselves and between spermatids and Sertoli cells. Round and elongated spermatids appear to represent two classes of structuraly and functionnaly different cells. One question remains: on what criteria can one claim that a round spermatid functions normally when spermiogenesis is blocked or impaired?     

Effects of photoperiod and temperature on testicular function in amphibians

Most amphibians present an annual testicular cycle characterized by a quiescent period (late autumn-winter) and a spermatogenic period (spring and summer). At the end of the period of spermatogenesis undifferentiated interstitial cells transform into steroid-secreting Leydig cells which regress in spring at the beginning of the new spermatogenetic cycle. The testicular cycle is controlled by the pituitary gonadotropin levels which are high in autumn and winter, low in spring and increase temporarily in the middle of summer. Photoperiod and temperature seem to be the most important external factors involved in the regulation of this cycle in many amphibian species since the colder the geographic area, the longer the quiescent period and the shorter the spermatogenic period. This suggests the occurrence of a potentially continuous cycle in these species, in contrast with that which occurs in other species having an endogenous rhythm of testicular function which is much less sensitive to environmental factors. Although the specific response to temperature can vary widely between species, the most frequent observation in amphibians with a potentially continuous cycle is that exposure to mild temperatures (15-20 degrees C, according to the spring temperatures of the different geographic areas) stimulates spermatogenesis even during the period of testicular quiescence. If this mild temperature is combined with a long photoperiod, complete spermatogenesis is attained. Experiments performed during the period of germ-cell proliferation (development from spermatogonia to round spermatids) indicated that low temperatures (below 11 degrees C) as well as short photoperiods (less than 8 h of light) hinder germ-cell proliferation. Moderately high temperatures (about 30 degrees C) do not impair this proliferation. In the newt Triturus marmoratus, it has been shown that an excessively long photoperiod (over 16 h) has the same effect as a short photoperiod. In this species eyes are not required for the testicular photoperiodic response. Photoperiod appears to have no effect on spermiogenesis (differentiation of round spermatids into spermatozoa), because once round spermatids are formed, spermiogenesis will occur even in total darkness. Mild temperatures seem to be necessary for spermiogenesis as well as for androgen biosynthesis because neither process will take place at extreme temperatures. Results on the effect of photoperiod in steroidogenesis differ between species.     

OBSERVATIONS ON THE FINE STRUCTURE OF THE DEVELOPING SPERMATID IN THE DOMESTIC CHICKEN

The kinetic apparatus, the acrosome and associated structures, and the manchette of the spermatid of the domestic chicken have been studied with the electron microscope. The basic structural features of the two centrioles do not change during spermiogenesis, but there is a change in orientation and length. The proximal centriole is situated in a groove at the edge of the nucleus and oriented normal to the long axis of the nucleus and at right angles to the elongate distal centriole. The tail filaments appear to originate from the distal centriole. The plasma membrane is invaginated along the tail filaments. A dense structure which appears at the deep reflection of the plasma membrane is identified as the ring. The fine structure of the ring has no resemblance to that of a centriole and there is no evidence that it is derived from or related to the centrioles. The tail of the spermatid contains nine peripheral pairs and one central pair of tubular filaments. The two members of each pair of peripheral filaments differ in density and in shape: one is dense and circular, and the other is light and semilunar in cross-section. The dense filaments have processes. A manchette consisting of fine tubules appears in the cytoplasm of the older spermatid along the nucleus, neck region, and proximal segment of the tail. The acrosome is spherical in young spermatids and becomes crescentic and, finally, U-shaped as spermiogenesis proceeds. A dense granule is observed in the cytoplasm between acrosome and nucleus. This granule later becomes a dense rod which is interpreted as the perforatorium.     

Brg1 subunit of chromatin remodelling complex is present during Chara vulgaris (Charophyceae) spermatogenesis

ABSTRACT

During spermatogenesis, cells developed as a result of numerous mitotic and meiotic divisions transform into mature spermatozoids. In spermatids, remodelling of chromatin structure takes place which is connected with nuclear protein exchange, DNA double strand breaks and epigenetic modifications. Chromatin remodelling complexes, which have mostly been studied in animals, also participate in this process. The Brg1 protein, a functional homologue of the yeast Swi2/Snf2 catalytic subunit of the SWI/SNF complex, is engaged in regulation of cell proliferation and highly expressed in round spermatids in mammals. Immunocytochemical studies with the anti-Brg1 antibody revealed positive reactions in nuclei of the green alga Chara vulgaris at the 64-cell proliferative stage and in spermatid nuclei at the I/II–VII spermiogenesis stages. The most intensive reaction was observed at the early spermiogenesis stages (I/II–III), while at the initial stages of a proliferative phase (4-, 8- and 16-cell) the reaction was not observed, and at 32-cell and VII stages the immunosignals were very weak. Ultrastructural studies with the immunogold technique confirmed the results of the immunocytochemical studies. The highest numbers of gold grains were observed at stages I/II and III of spermiogenesis, and together they constituted above 48% of the total number of gold grains. A much lower, but still substantial, amount of these grains was observed at the 64-cell stage and IV stage (>15% and 17%), respectively. Percentage analysis revealed the lowest number of gold particles at stage VII (3.72%). The significant presence of Brg1 protein at early spermiogenesis stages is correlated with acetylation of the H4K12 histone. It may also be hypothesized that in C. vulgaris the Brg1 subunit participates in processes important for proper chromatin condensation and facilitates maintenance of the correct shape of the spermatid nucleus. On the basis of earlier and current studies it seems that chromatin remodelling in spermatids of this model alga proceeds according to the model presented for mammals.     

Behaviour of microchromosome-associated satellite DNA in the banded krait,Bungarus fasciatus (Ophidia,Elapidae)

Banded krait(Bungarus fasciatus) major satellite DNA (p = 1.700 g/cm³) is mainly localized in the C-band-positive regions of all the microchromosomes. Our study of the behaviour of this satellite DNA byin situ hybridization has revealed a striking polarization of this DNA in the follicular epithelial cells of the ovary during oogenesis and in the spermatids during spermiogenesis. The major satellite DNA is localized at the point of the subsequent protrusion of the acrosomal pole of the round spermatid nuclei and remains in close contact with the developing sperm tip during the process of spermiogenesis. There appears to be an attraction between a specific region of the nuclear membrane and satellite-rich chromatin of the microchromosomes that brings about their polarization. We discuss possible functions of such extreme polarization of microchromosomes in specific cell types during oogenesis and spermiogenesis.     

Further ultrastructural research of Chara vulgaris spermiogenesis: endoplasmic reticulum,structure of chromatin, 3H-lysine and 3H-arginine incorporation

On the basis of morphological features, 10 consecutive structural phases of spermatids were identified in Chara vulgaris spermiogenesis. They were schematically presented. In early and middle spermiogenesis, i.e. during the period preceding formation of fibrillar structure of mature spermatozoid nucleus, a slight remodelling of chromatin, accompanied by proplastid transformation into an amyloplast as well as by development of 2 flagella and a microtubular manchette, is observed. First, condensed chromatin concentrates around the nuclear envelope (phases III-V) and then it transforms into a network-like structure (phase VI). This change in chromatin structure is preceded by nucleolar extrusion to the cytoplasm where nucleoli become degraded (phase IV) and by a dynamic development of rough endoplasmic reticulum (RER) (phase V) which is continuous with the nuclear envelope and with RER of the adjacent spermatids via plasmodesmata. The inner membrane of the nuclear envelope invaginates into the nucleoplasm in which "nuclear reticulum" appears. It all happens during increased 3H-arginine and 3H-lysine incorporation into proteins which are rapidly translocated into the nucleus. In medium-late spermiogenesis (phases VI-VIII), network-like condensed chromatin disappears. Next, the structure of the nucleus changes dramatically. Short, randomly positioned fibrils (phase VII) appear and gradually become longer (phase VIII), thicker (phase IX) and more distinct, lying parallel to the surface of elongating and curling nucleus. Membranes of the nuclear envelope become closer to each other and a distinct dark layer--probably lamin--appears adhering to the inner membrane of the nuclear envelope. Towards the end of spermiogenesis (phase X), very densely packed parallel helices, ca 2 nm in diameter, are visible. The surfaces of flagella and the spermatozoid are covered with diamond-shaped larger and smaller scales, respectively. Helically coiled spermatozoids are liberated from antheridial filament cells through earlier created (phase VIII) "liberation pores" with pads of unknown nature.     

Nuclear protein transitions in cuttle-fish spermiogenesis: Immunocytochemical localization of a protein specific for the spermatid stage

The changes in basic nuclear proteins throughout cuttle-fish spermiogenesis were investigated both by immunocytochemical procedures and by isolation of late spermatid nuclei (by virtue of their resistance to sonication). Antibodies were raised in rabbits to a protein, named protein T, isolated from testis chromatin. The anti-protein T immune serum was found to recognize protein T and not histones from the testis. Immunoperoxidase staining of sections or of smears of testis with anti-protein T antibodies showed that protein T appears in the nuclei of round spermatids, is abundant in elongating spermatid nuclei, but cannot be detected in elongated spermatids. Nuclei from these elongated spermatids were isolated by sonication treatment of testis cells. A protein, named protein Sp, with the characteristic mobility of a protamine, was isolated from elongated spermatid nuclei. This protein has the same mobility as the protamine present in mature spermatozoa. Taken together, the results indicate that in cuttle-fish, nuclear protein transitions involve the replacement of histones by a spermatid-specific protein (protein T), which is replaced at the end of elongation of the nucleus by a protamine (protein Sp). Thus, spermiogenesis of the cuttle-fish (and perhaps of other cephalopods), shows two basic nuclear protein transitions, which are similar to the transitions observed in higher vertebrates such as mammals.     

Structure, development, and cytochemical properties of the nucleolus-associated "round body" in rat spermatocytes and early spermatids

The "round body," a spherical structure typically associated with a nucleolus in male germ cells of the rat, has been examined in the electron microscope using routine and cytochemical methods to determine its structure, composition, and mode of development. Cytochemical analysis indicates that the round body includes neither nucleic acid nor lipid, but is composed of nonhistone protein which appears in the form of 1.6-nm-wide fibrils. Development begins in late leptotene, when a single round body appears in each spermatocyte as an irregular spheroid located along the inner surface of the nuclear envelope. During subsequent stages of the meiotic prophase, the round body leaves the nuclear envelope, becomes a regular sphere, and gradually enlarges from a diameter of 0.4 micron in leptotene to 1.6 micron in diplotene. Concurrently, lacunae appear within its substance and enlarge. At each maturation division, the amount of round-body material is decreased by about half, presumably because the constituent proteins are dissociated at metaphase, distributed between the two daughter cells at telophase, and reconstituted into half-sized round bodies. As spermiogenesis proceeds, the round body shrinks gradually and disappears at step 8. Soon after its appearance at leptotene, the round body becomes associated with and is surrounded by the pars granulosa of one of the nucleoli. Moreover, 3H-uridine incorporation into nucleolar RNA is high as long as the size of the round body increases, but is low or absent when it decreases. It is possible, therefore, that the round body exerts some control on nucleolar activity in meiotic cells.     

Perinuclear cytoskeleton of acrosome-less spermatids in the blind sterile mutant mouse.

The perinuclear cytoskeleton of mammalian spermatids is thought to play a major role in nucleus-acrosome association and in shape changes of the head during spermiogenesis. To test these hypotheses acrosome-less spermatids in blind-sterile mutant mice were investigated for the development of the subacrosomal layer. Immunogold procedures were used for the detection of actin and calmodulin. In addition to various other abnormalities many acrosome-less round and elongating spermatids developed a subacrosomal layer with an actin and calmodulin distribution similar to that observed in normal spermatids. However, in mutant elongating spermatids the apical part of the nucleus was truncated and/or folded. The expected elongation and shaping of the nucleus only occurred in its caudal part associated with an hypertrophied and somewhat ectopic manchette. These abnormalities and those previously observed in mutant and experimental models indicated that the subacrosomal layer may form independently of the acrosome. It is suggested that the subacrosomal filamentous actin is a transitory scaffolding which might be involved in the assemblage of other proteins of the perinuclear cytoskeleton. However, by itself, this layer is not sufficient to ensure a normal shaping of the nucleus. Acrosome-nucleus interactions mediated by the subacrosomal layer seem necessary to shape the cranial spermatid head. The manchette appears to be involved only in the caudal nuclear shaping.     

Rat Sertoli and spermatogenic cells express a similar gene, and its product is antigenically related to an outer dense fiber-associated protein.

We have previously reported that a heterodimeric protein secreted by rat Sertoli cells is antigenically related to a protein associated with outer dense fibers of the sperm tail. Therefore, we have explored the possibility that Sertoli and spermatogenic cells express a similar gene encoding a homologous protein. A Sertoli cell heterodimeric protein cDNA probe recognizes specific mRNA in pachytene and round spermatids fractionated by centrifugal elutriation; however, this specific mRNA was less prominent than in cultured Sertoli cells. In agreement with these observations, in situ hybridization experiments show that Sertoli cells are predominantly engaged in active heterodimeric protein mRNA synthesis, while meiotic prophase spermatocytes and spermatids also show significant but less abundant specific mRNA. Immunoblotting experiments demonstrate that, while Sertoli cells synthesize a heterodimeric protein consisting of two disulfide-linked components with molecular masses of 45 and 35 kD, both primary spermatocytes and round spermatids synthesize single 30 kD monomers not associated by disulfide linkage but recognized by antisera to Sertoli cell heterodimeric protein. Immunoblotting and immunogold electron microscopic studies show that antisera to Sertoli cell heterodimeric protein recognize a protein associated with outer dense fibers. This immunoreactivity was abolished by a 5-min pronase treatment, without affecting the integrity of outer dense fibers. Results of this study and previous studies demonstrate that both Sertoli and spermatogenic cells express a similar gene and that an antigenically related product encoded by this gene becomes associated with outer dense fibers during their assembly at spermiogenesis.