Sertoli Cell Microtubules Research Articles

Association between an alternative promoter polymorphism and sperm deformity rate is due to modulation of the expression of KATNAL1 transcripts in Chinese Holstein bulls.

Katanin p60 subunit A-like 1 (KATNAL1) is an ATPase that regulates Sertoli cell microtubule dynamics and sperm retention. We evaluated one novel splice variant and characterized the promoter and a functional single nucleotide polymorphism (SNP) of the bovine KATNAL1 gene to explore its expression pattern, possible regulatory mechanism and relationship with semen traits in Chinese Holstein bulls. A novel splice variant, KATNAL1 transcript variant 2 (KATNAL1-TV2) of the retained 68bp in intron 2, was identified by RT-PCR and compared with KATNAL1 transcript variant 1 (KATNAL1-TV1, NM 001192918.1) in various tissues. Bioinformatics analyses predicted that KATNAL1 transcription was regulated by two promoters: P1 in KATNAL1-TV1 and P2 in KATNAL1-TV2. Results of qRT-PCR revealed that KATNAL1-TV1 had higher expression than did KATNAL1-TV2 in testes of adult bulls (P<0.05). Promoter luciferase activity analysis suggested that the core sequences of P1 and P2 were mapped to the region of c.-575˜c.-180 and c.163-40˜c.333+59 respectively. One novel SNP (c.163-210T>C, ss836312085) located in intron 1 was found using sequence alignment. The SNP in P2 resulted in the presence of the DeltaE binding site, improving its basal promoter activity (P<0.05); and we observed a greater sperm deformity rate in bulls with the genotype CC than in those with the genotype TT (P<0.05), which indicated that different genotypes were associated with the bovine semen traits. Bioinformatics analysis of the KATNAL1 protein sequence predicted that the loss of the MIT domain in the KATNAL1-TV2 transcript resulted in protein dysfunction. These findings help us to understand that a functional SNP in P2 and subsequent triggering of expression diversity of KATNAL1 transcripts are likely to play an important role with regard to semen traits in bull breeding programs.

KATNAL1 regulation of sertoli cell microtubule dynamics is essential for spermiogenesis and male fertility.

Spermatogenesis is a complex process reliant upon interactions between germ cells (GC) and supporting somatic cells. Testicular Sertoli cells (SC) support GCs during maturation through physical attachment, the provision of nutrients, and protection from immunological attack. This role is facilitated by an active cytoskeleton of parallel microtubule arrays that permit transport of nutrients to GCs, as well as translocation of spermatids through the seminiferous epithelium during maturation. It is well established that chemical perturbation of SC microtubule remodelling leads to premature GC exfoliation demonstrating that microtubule remodelling is an essential component of male fertility, yet the genes responsible for this process remain unknown. Using a random ENU mutagenesis approach, we have identified a novel mouse line displaying male-specific infertility, due to a point mutation in the highly conserved ATPase domain of the novel KATANIN p60-related microtubule severing protein Katanin p60 subunit A-like1 (KATNAL1). We demonstrate that Katnal1 is expressed in testicular Sertoli cells (SC) from 15.5 days post-coitum (dpc) and that, consistent with chemical disruption models, loss of function of KATNAL1 leads to male-specific infertility through disruption of SC microtubule dynamics and premature exfoliation of spermatids from the seminiferous epithelium. The identification of KATNAL1 as an essential regulator of male fertility provides a significant novel entry point into advancing our understanding of how SC microtubule dynamics promotes male fertility. Such information will have resonance both for future treatment of male fertility and the development of non-hormonal male contraceptives.

Altered phosphorylation and distribution status of vimentin in rat seminiferous epithelium following 17β-estradiol treatment

Vimentin, type III intermediate filament, has stage-specific localization in the Sertoli cell. In the rat, during stages I-V and XI-XIV of the seminiferous epithelium, vimentin is localized in the perinuclear area with filaments projecting into the apical region toward the developing germ cells. These filaments decrease in length at stages VI-VII with perinuclear staining in stages VIII-IX, when spermiation occurs. Our earlier studies following 17β-estradiol treatment to adult male rats demonstrated an increase in germ cell apoptosis, spermiation failure and disruption of Sertoli cell microfilaments and microtubules. The present study was undertaken to determine the stage-specific distribution of vimentin and its involvement in spermiation failure and germ cell apoptosis. Immunofluorescence studies revealed that in contrast to the perinuclear localization with small extensions in control stages VII-IX, long extensions radiating apically to the spermatids in deep recess were observed in the treated group. Immunoprecipitation studies showed marked absence of phosphorylated vimentin in stages VII-VIII in the treated group. Further, localization of plectin, cytoskeletal linker protein, showed decrease in all the stages of spermatogenesis following estradiol treatment. Interestingly, for the first time the localization of plectin in the tubulobulbar complex was observed. In conclusion, the study suggests that estradiol treatment leads to an effect on vimentin phosphorylation, which could have inhibited the disassembly of vimentin leading to retention of apical projection in stages VII-VIII. These effects could be presumably due to a decrease in plectin, affecting the reorganization of vimentin and therefore the apical movement of spermatids, leading to spermiation failure.

APC (Adenomatous Polyposis Coli), a Tumor Suppressor Gene, Is Required for Maintenance of Sertoli Cell Polarity and Microtubules Integrity.

APC (Adenomatous Polyposis Coli), a Tumor Suppressor Gene, Is Required for Maintenance of Sertoli Cell Polarity and Microtubules Integrity.

Effect of nitric oxide on Sertoli cell microtubule of piglets

AbstractTo illustrate the effect of nitric oxide (NO) on the microtubules of Sertoli cells (SC), SCs of piglets were treated with sodium nitroprusside (SNP). Changes in cell viability, anti-oxidant activity, enzyme activity and p38 mutagen-activated protein kinase (p38MAPK) activation were detected. The results were as follows. A low concentration of NO can keep SC microtubule and cell viability normal, and a high concentration of NO could increase p38MAPK activation, decrease anti-oxidant activity and transferrin secretion, and destroy the structure and distribution of the microtubules. The results suggest that SNP treatment results in an increase in NO in SCs and decreased cell anti-oxidant activity. The high concentration of NO destroys cell microtubules by activating p38MAPK.

Mechanism of Action of l-CDB-4022, a Potential Nonhormonal Male Contraceptive, in the Seminiferous Epithelium of the Rat Testis

The present study was conducted to elucidate the possible molecular mechanisms involved in the antispermatogenic activity of l-CDB-4022, an indenopyridine. In this study 45-d-old male Sprague-Dawley rats were treated with a single oral dose of l-CDB-4022 (2.5 mg/kg) or vehicle, and blood and testes were collected at various time points. The rate of body weight gain was not affected, but a significant loss of testes weight was induced by l-CDB-4022. Serum hormones were assayed using specific RIAs or ELISAs, and testicular protein and RNA were analyzed by Western blotting and RT-PCR, respectively. There was a significant decrease in inhibin B and concomitant increase in FSH in serum from l-CDB-4022-treated rats, but serum levels of activin A, testosterone, and LH were unchanged. Western analysis of testicular lysates from l-CDB-4022-treated rats exhibited phosphorylation of ERK1/2 at 4 h and later time points. Loss of nectin/afadin complex occurred at 48 h, but there was an increase in levels of integrin-beta1, N-cadherin, alpha-catenin, and beta-catenin protein at 24 h and later time points. Increase in expression of Fas ligand and Fas receptor was detected 8 and 24 h after l-CDB-4022 treatment. The ratio of the membrane to soluble form of stem cell factor mRNA was decreased. Immunohistochemical analysis of testicular sections indicated a dramatic disruption of the Sertoli cell microtubule network in l-CDB-4022-treated rats. Collectively, these results suggest that l-CDB-4022 activates the MAPK pathway, reduces expression of prosurvival factors such as the membrane form of stem cell factor, alters expression of Sertoli-germ cell adherens junction proteins, disrupts Sertoli cell microtubule structure, and induces the proapoptotic factor, Fas, culminating in germ cell loss from the seminiferous epithelium.

Evidence that a kinesin is associated with ectoplasmic specializations in the testis

During spermatogenesis, spermatids undergo a “down and up” translocation event in the seminiferous epithelium. This event has been proposed to be microtubule-based and to result from the movement of apical “ectoplasmic specializations” (adhesion junctions) along adjacent Sertoli cell microtubule tracts. Dynein is present at the junctions and is likely responsible for the upward movement of spermatids. A kinesin is likely responsible for the downward movement of spermatids. To test the hypothesis that a kinesin is associated with the junctions, we generated an antibody to the “LAGSE” sequence conserved amongst kinesins, and reacted the antibody with fixed frozen sections of epithelium or fixed epithelial fragments. In tissue processed for immunofluorescensce, the antibody reacted at sites known to contain apical ectoplasmic specializations, in addition to reacting with other structures in the epithelium known to contain kinesins. In material processed for immunogold localization, the antibody reacted with the cytoplasmic face of the endoplasmic reticulum component of ectoplasmic specializations. Kinesin mRNA transcript screens using mouse GeneChip arrays of testis and Sertoli cells indicated that a possible candidate kinesin for spermatid translocation is Rab6KIFL. Antibodies generated against a peptide sequence that is unique to this kinesin reacted with regions associated with spermatid heads, and with a band on immunoblots that is not present in other tissues and migrates at a higher molecular weight than that known for Rab6KIFL. We are currently identifying the protein. Our results are consistent with the prediction that a kinesin is associated with ectoplasmic specializations. CIHR MOP 62768

Atypical development of Sertoli cells and impairment of spermatogenesis in the hypogonadal (hpg) mouse

Testes of hypogonadal (hpg) mice show arrested postnatal development due to congenital deficiencies of gonadotrophin-releasing hormone (GnRH) and gonadotrophin synthesis and secretion. Follicle-stimulating hormone (FSH), androgen or oestrogen treatment restore qualitatively normal spermatogenesis in hpg testes. Understanding the cellular and molecular changes accompanying hormone-induced spermatogenesis in hpg mice requires detailed morphological analyses of the germ cells and Sertoli cells in the untreated hpg testis. We compared seminiferous epithelial cytology in adult hpg, immature and adult wild-type mice using unbiased optical disector-based stereology, immunolocalization of Sertoli cell microtubules (MT), espin (a component of the blood-testis barrier), markers of Sertoli cell maturity (p27(kip1) and WT-1), and electron microscopy. Hpg testes had marked reductions in weight, seminiferous cord volume and length, and severe spermatogenic impairment with germ cells per testis < 1% of adult wild-type testes. Sertoli cell nuclei expressed WT-1 in hpg testes, but often were centrally located, similar to 9-14-day-old wild-type testes, and they expressed p27(kip1), indicating that hpg Sertoli cells were post-mitotic. Hpg testes had significantly (P < 0.05) reduced Sertoli cells per testis (0.56 million) compared with 10-day wild-type (1.15 million) and adult wild-type testes (2.06 million). Immunofluorescence labelling of normal adult Sertoli cells showed supranuclear MT columns and basally located espin, but these features were absent in 10-day-old and hpg Sertoli cells. Hpg Sertoli cells showed pleomorphic nuclear ultrastructure with mature-type nucleoli, similar to normal adult-type Sertoli cells, but hpg Sertoli cells exhibited incomplete tight junctions that lacked ectoplasmic specializations. We conclude that in hpg mice, chronic gonadotrophin insufficiency restrains Sertoli cell proliferation and maturation, forming pseudo-adult-type Sertoli cells that are incapable of supporting germ cell proliferation and maturation.

Synopsis: 2003 Annual Meeting of the American Society of Andrology.

Synopsis: 2003 Annual Meeting of the American Society of Andrology.

Gamma-Tubulin overexpression in Sertoli cells in vivo: I. Localization to sites of spermatid head attachment and alterations in Sertoli cell microtubule distribution.

Sertoli cells play a number of roles in supporting spermatogenesis, including structural organization, physical and paracrine support of germ cells, and secretion of factors necessary for germ cell development. Studies with microtubule disrupting compounds indicate that intact microtubule networks are crucial for normal spermatogenesis. However, treatment with toxicants and pharmacologic agents that target microtubules lack cell-type selectivity and may therefore elicit direct effects on germ cells, which also require microtubule-mediated activities for division and morphological transformation. To evaluate the importance of Sertoli cell microtubule-based activities for spermatogenesis, an adenoviral vector that overexpresses the microtubule nucleating protein, gamma-tubulin, was used to selectively disrupt microtubule networks in Sertoli cells in vivo. gamma-Tubulin overexpression was observed to cause redistribution of Sertoli cell microtubule networks, and overexpression of a gamma-tubulin-enhanced green fluorescent protein fusion protein was observed to localize to the site of elongate spermatid head attachment to the seminiferous epithelium.

Gamma-Tubulin overexpression in Sertoli cells in vivo. II: Retention of spermatids, residual bodies, and germ cell apoptosis.

The degree of germ cell dependence on Sertoli cell-mediated activities has been a subject of considerable attention. Sertoli cell secretory pathways have been extensively studied both in an effort to understand their normal physiologic roles and as targets for pharmacologic and toxicant activity. To determine the degree to which normal spermatogenesis depends on key functions of the Sertoli cell microtubule network, adenoviral vectors that overexpress the microtubule nucleating protein, gamma-tubulin, were delivered to Sertoli cells in vivo. gamma-Tubulin overexpression disrupts the Sertoli cell microtubule network (as described in the companion article); leads to gross disorganization of the seminiferous epithelium, inducing retention of spermatids and residual bodies; and causes germ cell apoptosis. These data are consistent with earlier studies in which toxicants and pharmacologic agents were used to disrupt microtubule networks. These data confirm that Sertoli cell microtubule networks play an important role in maintaining the organization of the seminiferous epithelium and that in the absence of an intact Sertoli cell microtubule network, germ cell viability is impaired.

Stage-specific effects of the fungicide carbendazim on Sertoli cell microtubules in rat testis

The aim of the present study is to provide a morphological explanation of carbendazim (CBZ)-induced sloughing of germ cells that occurs in a stage-specific manner. Therefore, very early alterations in the seminiferous tubule epithelium were examined histologically in the rat testis after oral administration of CBZ (400 mg/kg). Gaps between the elongated and round spermatids, the first indication of germ cell sloughing (pre-sloughing), were observed in stage late VI–early VII seminiferous tubules at 90-min post-treatment. Tubulin immunoreaction in the Sertoli cells was reduced in intensity in tubules with pre-sloughing. However, electron microscopy demonstrated that there were some intact microtubules in these cells. At 120 min, sloughing was seen in stage late VI–early VII and XIII–XIV. Tubulin immunoreaction in the Sertoli cells was greatly decreased in intensity in tubules where cell sloughing was observed. Electron microscopy showed that there were few microtubules in the body region of these cells. Stages II–V and mid-VII–VIII were exempt from the sloughing effect at 180 min. These changes in microtubules were not observed in Sertoli cells that did not exhibit sloughing characteristics, regardless of the post-treatment intervals. The present results suggest that stage specificity of sloughing is due to the stage-specific susceptibility of Sertoli cell microtubules to CBZ.

E-MAP-115, encoding a microtubule-associated protein, is a retinoic acid-inducible gene required for spermatogenesis

Cell type-specific microtubules, such as the Sertoli cell microtubules and the manchette and flagellum microtubules of the spermatids, play essential roles in spermatogenesis. We identified the gene encoding E-MAP-115 (epithelial microtubule-associated protein of 115 kD) as a retinoic acid-inducible gene using gene trap mutagenesis in mouse embryonic stem cells. The gene trap insertion led to a null allele of the E-MAP-115 gene and, in agreement with its high expression in the testis, male mice homozygous for the mutation were sterile because of deformation of spermatid nuclei and subsequent gradual loss of germ cells. Consistent with a possible role for E-MAP-115 in stabilizing microtubules, microtubule associations in the mutant were morphologically abnormal in the manchette of spermatids and in Sertoli cells. We hypothesize that the abnormal microtubules in these two cell types are responsible for deformation of spermatid nuclei and germ cell loss, respectively, and indicate an essential role for E-MAP-115 in microtubule functions required for spermatogenesis.

Characterization of stage-specific tyrosinated α-tubulin immunoperoxidase staining patterns in Sertoli cells of rat seminiferous tubules by light microscopic image analysis

Microtubules are involved in many structural and functional changes that occur in Sertoli cells during the cycle of the seminiferous epithelium. However, few studies have addressed stage-specific changes in the distribution of microtubules that accompany the process of spermatogenesis. This study provides a stage-by-stage immunohistochemical evaluation of Sertoli cell microtubules in paraffin sections of whole rat testes using an antibody to tyrosinated α-tubulin. Microtubules that contain tyrosinated tubulin are considered to be less stable and are therefore expected to populate Sertoli cells undergoing dynamic changes during spermatogenesis. A quatitative method was developed to analyze the relative tyrosinated α-tubulin staining in different stages of the cycle. Immunostaining patterns of the stages were separated into five different groups. Stages VII–VIII had the least amount of tyrosinated α-tubulin, while stages IX–XI contained the greatest amount. The staining patterns were consistent with established structural changes in the seminiferous epithelium, such as the formation of ectoplasmic specializations, the presence of microtubule nucleation sites along the periphery of the apical cytoplasm, and the translocation of elongate spermatids from deep crypts in the Sertoli cell to the tubule lumen. These data should provide improved methods for the evaluation of microtubules in the study of Sertoli cell responses to environmental toxicants and testicular diseases.

Colchicine effects on meiosis in the male mouse. I. Meiotic prophase: synaptic arrest, univalents, loss of damaged spermatocytes and a possible checkpoint at pachytene.

Antimitotic agents administered at the time of synapsis (leptotene/zygotene) have been shown to induce synaptic abnormalities visible during pachytene in the male mouse. The object of this study was to test the hypothesis that cells with relatively large amounts of colchicine-induced damage to the synaptonemal complex (SC) are eliminated from prophase whereas cells with relatively small amounts of SC damage proceed through to the end of prophase. Male mice were injected with tritiated thymidine to mark a cohort of spermatocytes at premeiotic S-phase for tracking through pachytene. Forty-eight hours later, when those cells were at leptotene/zygotene, colchicine was administered intratesticularly. Whole-mount SC spreads were made from animals sacrificed at various times following colchicine administration, and prepared for autoradiography. The marked cells were examined by light and electron microscopy and the kind and number of synaptic abnormalities were scored throughout pachytene. Colchicine-induced SC damage included single axial elements (univalents), together with partially synapsed and nonhomologously synapsed SCs. The amount of SC damage (amount and type per cell and frequency of cells with damage) scored at early pachytene exceeded by three- to fivefold the amount at late pachytene. This is consistent with spermatogenic cell loss from the seminiferous tubule via colchicine-induced destruction of Sertoli cell microtubules. The presence of spermatocytes with no more than four autosomal univalents at late pachytene indicates that some cells with low amounts of synaptic damage progress to the end of pachytene. The loss of the most severely damaged cells may represent a meiotic checkpoint at early pachytene in the male mouse.

Distribution of Sertoli cell microtubules, microtubule‐dependent motors, and the Golgi apparatus before and after tight junction formation in developing rat testis

Sertoli cells are polarized epithelial cells of the seminiferous epithelium which provide structural and physiological support for differentiating germ cells. They establish different basal and adluminal environments for the selective nurturing of pre- and post-meiotic germ cells within the seminiferous epithelium, segregated by the Sertoli-Sertoli cell tight junctional complex, the blood-testis barrier. Tight junction formation between epithelial cells in vitro is a critical polarizing event associated with changes in polarized targeting of membrane-specific proteins and reorganization of microtubules, centrioles, and the Golgi apparatus. To investigate whether tight junction formation is associated with organelle reorganization in Sertoli cells in vivo, we have characterized distribution patterns of Sertoli cell microtubules, the mechanoenzymes kinesin and cytoplasmic dynein, and the Golgi apparatus during tight junction formation in developing rat testis. Immunocytochemistry on samples taken at 5, 10, 15, 20, and 25 days of age was used to examine the distribution of these proteins during the extensive cellular reorganization that culminates in the formation of the blood-testis barrier at 19 days of age. Our data show that the distribution patterns reflect the extensive intercellular repositioning of tubule cells in developing seminiferous tubules, but that changes in intracellular organization are not temporally associated with formation of the blood-testis barrier.

Seminiferous Tubule Fluid Secretion Is a Sertoli Cell Microtubule-Dependent Process Inhibited by 2,5-Hexanedione Exposure

Mammalian Sertoli cells are responsible for the formation and secretion of seminiferous tubule fluid (STF) which provides the nutritional and hormonal microenvironment necessary for spermatogenesis. Exposure of rats to 2,5-hexanedione (2,5-HD) results in testicular injury characterized by a decrease of STF secretion which immediately precedes bulk germ cell necrosis. The earliest biochemical change in 2,5-HD-exposed rats is an alteration in testicular microtubule assembly kinetics. In this study, we investigate the relationship between microtubule-dependent processes and STF secretion in adult Sprague-Dawley CD rats by exposing seminiferous tubules to two types of toxicants: (1) those which alter microtubules (colchicine and 2,5-HD) and (3) an inhibitor of protein secretion (brefeldin A, [BFA]). Secretion of STF is quantitated by monitoring the rate of transport of a microinjected oil droplet in the lumen of isolated seminiferous tubules using time-lapse stereoscopic microscopy. The rate of oil droplet transport in seminiferous tubules isolated from testis pretreated in vivo for 2 hr with colchicine (40 μg/testis) was significantly decreased. Exposure of isolated seminiferous tubules to BFA(IO μg/ml) for 10 min also significantly decreased the transport of lumenal oil droplets. Exposure of rats to 1% 2,5-HD in drinking water decreased transport of injected oil droplets in seminiferous tubules beginning at 3 weeks of exposure in the absence of significant alterations in testicular morphology. These data demonstrate that normal STF secretion requires an intact, microtubule-dependent intracellular membrane transport pathway and strengthen the association between 2,5-HD-induced disruption of Sertoli cell STF secretion and 2,5-HD-induced alterations in Sertoli cell microtubules.

Colchicine Disrupts the Cytoskeleton of Rat Testis Seminiferous Epithelium in a Stage-Dependent Manner1

Sertoli cell microtubules play an important role in the process of spermatogenesis. We investigated the effects of colchicine, a microtubule-disrupting agent, on the seminiferous epithelium. Rats were injected intratesticularly with 0.004-40 micrograms colchicine/testis. Colchicine had a dose-related effect on seminiferous tubule fluid secretion and completely blocked secretion at a dose of 40 micrograms colchicine/testis. Colchicine also resulted in a dose-related decrease in testes weight 2 and 8 wk after injection. When 40 micrograms colchicine/testis was used, testis morphology showed a time-dependent increase in the incidence of sloughing over a time course of 1, 3, 6, and 16 h. Quantitative analysis demonstrated that stage IX-XIV seminiferous tubules were most sensitive to sloughing. Changes in the distribution of tubulin immunostaining within Sertoli cells occurred preferentially in stage VII-VIII seminiferous tubules, which were most resistant to sloughing. In addition, colchicine resulted in disruption of vimentin filaments in stage IX-XIV seminiferous tubules, which correlated with the stage-dependent sensitivity of sloughing. We propose that the stage dependence of colchicine-induced effects reflects the dynamic and stage-dependent role of microtubules in spermatogenesis. Furthermore, cellular structures other than microtubules, such as vimentin filaments, may be important for maintaining the structural integrity of the seminiferous epithelium.

Distribution of the microtubule-dependent motors cytoplasmic dynein and kinesin in rat testis.

To examine the possible role of microtubule-based transport in testicular function, we used immunofluorescent techniques to study the presence and localization of the microtubule mechanoenzymes cytoplasmic dynein (a slow-growing end-directed motor) and kinesin (a fast-growing end-directed motor) within rat testis. Cytoplasmic dynein immunofluorescence was observed in Sertoli cells during all stages of spermatogenesis, with a peak in apical cytoplasm during stages IX-XIV. Cytoplasmic dynein immunofluorescence was also localized within Sertoli cells to steps 9-14 (stages IX-XIV) germ cell-associated ectoplasmic specializations. In germ cells, cytoplasmic dynein immunofluorescence was observed in manchettes of steps 15-17 (stages I-IV) spermatids, and small, hollow circular structures were seen in the cytoplasm of step 17 and step 18 spermatids during stages V and VI. Kinesin immunofluorescence was observed in manchettes of steps 10-18 spermatids (stages X-VI). The stage-dependent apical Sertoli cell cytoplasmic dynein immunofluorescence, in conjunction with the previously reported orientation of Sertoli cell microtubules (slow-growing ends toward the lumen) and peak secretion of androgen-binding protein and transferrin, is consistent with the hypothesis that cytoplasmic dynein is involved in Sertoli cell protein transport and secretion. Further, the localization of cytoplasmic dynein and kinesin to manchettes is consistent with current hypotheses concerning manchette function.

Spermiogenesis in Xenopus laevis: From late spermatids to spermatozoa

Spermatogenesis is a complex morphogenetic process in which microfilaments and microtubules have been shown to play an important role. The last steps of Xenopus spermatogenesis, i.e., the corkscrew shaping of the sperm head, have been followed to study actin and microtubule distribution by conventional and immunoelectron microscopy. During sperm head morphogenesis, actin is absent in the elongating spermatids, but it is present in the Sertoli cells where results localized at the periphery of their cytoplasm that surrounds the developing germ cells. Sertoli cell actin and microtubules may assist the elongation and the shaping of the spermatids and function in maintaining the Sertoli-spermatid association.