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PubMed1991

A zinc finger protein-encoding gene expressed in the post-meiotic phase of spermatogenesis.

Spermatogenesis is the complex series of physiological and morphological changes that occur when spermatogonial stem cells differentiate into mature spermatozoa. Some of these changes are likely to be regulated at the level of transcription. To approach this problem, we have cloned a cDNA from mouse testis, encoding a protein (Zfp-29) with 14 copies of the zinc finger (Zf) motif commonly found in transcriptional regulatory proteins. The expression of this gene, Zfp-29, is restricted to the testis in adult mice, but also occurs during embryonic development. Within the testis, Zfp-29 mRNA is enriched in round spermatids, the earliest post-meiotic cells. Thus, the putative Zfp-29-encoded protein may have a role in regulating the class of genes that are expressed in post-meiotic germ cells.

Amino Acid Sequence↗
PubMed2002

Cellular location and hormonal regulation of ghrelin expression in rat testis.

Ghrelin, the endogenous ligand for the growth hormone-secretagogue receptor, is a recently cloned 28-amino acid peptide, expressed primarily in the stomach and hypothalamus, with the ability to stimulate growth hormone (GH) release and food intake. However, the possibility of additional, as yet unknown biological actions of ghrelin has been suggested. As a continuation of our recent findings on the expression and functional role of ghrelin in rat testis, we report here the pattern of cellular expression of ghrelin peptide in rat testis during postnatal development and after selective Leydig cell elimination, and we assess hormonal regulation of testicular ghrelin expression, at the mRNA and/or protein levels, in different experimental models. Immunohistochemical analyses along postnatal development demonstrated selective location of ghrelin peptide within rat testis in mature fetal- and adult-type Leydig cells. In good agreement, ghrelin protein appeared undetectable in testicular interstitium after selective Leydig cell withdrawal. In terms of hormonal regulation, testicular ghrelin mRNA and protein expression decreased to negligible levels after long-term hypophysectomy, whereas replacement with human chorionic gonadotropin (CG) (as superagonist of LH) partially restored ghrelin mRNA and peptide expression. Furthermore, acute administration of human CG (25 IU) to intact rats resulted in a transient increase in testicular ghrelin mRNA levels, with peak values 4 h after injection, an effect that was not mimicked by FSH (12.5 IU/rat). In contrast, testicular expression of ghrelin mRNA remained unaltered in GH-deficient rats, under hyper- and hypothyroidism conditions, as well as in adrenalectomized animals. In conclusion, our results demonstrate that mature Leydig cells are the source of ghrelin expression in rat testis, the protein being expressed in both fetal- and adult-type Leydig cells. In addition, our data indicate that testicular expression of ghrelin is hormonally regulated and is at least partially dependent on pituitary LH.

Adrenalectomy↗
PubMed2001

Searching for missing pieces of the sex-determination puzzle.

Little is known of the mechanisms whereby the mammalian indifferent gonad develops into a testis or ovary. In XY individuals, Sry, the mammalian testis-determining gene, is expressed in the pre-Sertoli cells, which then differentiate into Sertoli cells. Other cell types, which include the germ cells, the steroidogenic cells and the connective tissue cells, must then be instructed to develop in a male-specific manner. Although some genes involved in sex-determination and differentiation processes have been identified, we know little of how they interact and cooperate to orchestrate the development of a testis or ovary. We have initiated an expression-screening program designed to identify additional genes, known or novel, which play a role in these processes. This approach is based on our belief that many of the genes we seek will be expressed in a sex-specific manner during the period of sex-determination and differentiation. Most of the genes identified previously are transcription factors and so we aim, in particular, to find genes involved in cell-to-cell communication, signal transduction, and transcriptional regulation, downstream of the differentiation of Sertoli cells. We have used a suppression subtractive-hybridization method to generate male- and female-enriched probes and libraries. Clones are validated as being sex-specific in their expression patterns by array screening and in situ hybridization. Here we report on our progress to date and the general applicability of the approach for studies in other systems. J. Exp. Zool. 290:517-522, 2001.

Animals↗
PubMed1999

Application of morphometric techniques to postnatal rat testes in organ culture: insights into testis growth.

The extent of Sertoli cell proliferation during fetal and neonatal development determines the final adult testis size and potential for sperm output. To gain further knowledge of the factors that regulate Sertoli cell proliferation, the present study used a new approach to analyse changes in morphology and proliferation in the postnatal testis by combining organ culture with morphometric analysis. Fragments of rat testes from days 0 to 10 postpartum were cultured in contact with DMEM for 6 h or 72 h and fixed. The effects of ovine follicle-stimulating hormone (FSH) and activin were studied in an additional 72-h organ culture experiment using day 9 testes. Bromodeoxyuridine (BrdU) was added for the last 6 h of culture to mark proliferating cells. Two-microm sections of the fragments were analysed for morphological changes of the seminiferous cords, and the proportion of BrdU-labelled Sertoli and germ cells was determined. Assessment of 6-h samples revealed growth characteristics consistent with those observed in vivo during days 1-10 of postnatal development. From day 2 onwards, the volume fraction of seminiferous cords began to increase, while significant growth in cross-sectional area of the cords occurred only after day 6. In these culture conditions, germ cell proliferation and testicular architecture was consistent with that expected for the age of the tissue at time of explant. The proportion of dividing Sertoli cells declined from 15-20% at days 0-4 postpartum to below % at day 10 postpartum in the 6-h culture, and it was low or abolished in the 3-day culture at all time points. Activin and FSH together, but not singly, stimulated Sertoli cell proliferation in the 72-h culture. This paper presents a new approach to analysis of in vitro testis development. The combination of fragment culture and stereological analysis permits rigorous and detailed assessment of developmental changes in the postnatal testis.

Activins↗
PubMed1997

Intersex disorders: shedding light on male sexual differentiation beyond SRY.

Male sexual differentiation involves a cascade of events initiated by the presence on the Y chromosome of the SRY gene, which causes the indifferent gonad to develop into a testis. Hormonal products of the testis, predominantly testosterone and Müllerian inhibiting substance (MIS), then control the sexual differentiation of the developing foetus. SRY is a transcription factor; however, target genes for its action have yet to be identified, because the DNA recognition sequence for SRY is found in many genes. Therefore the study of intersex disorders is being used to identify other genes active in the pathway of sexual differentiation. Genes identified as being important in the differentiation of the indifferent gonad include WT1 (abnormal in Denys Drash syndrome) and SF-1. The DSS locus may contain a gene that controls ovarian differentiation, and SOX9 (identified from campomelic dysplasia) is required for testis differentiation. In addition to playing a role in the development of the bipotential gonad, SF-1 may also activate MIS gene expression in the testis, causing regression of Müllerian structures. Luteinizing hormone and its receptor are required for Leydig cell differentiation, and the testosterone biosynthetic enzymes (P450scc, 3 beta-hydroxysteroid dehydrogenase, P45017 alpha and 17 beta-hydroxysteroid dehydrogenase) are all necessary for masculinization of external genitalia. 5 alpha-Reductase is required for the production of dihydrotestosterone, and the androgen receptor mediates the action of both testosterone and dihydrotestosterone. The identification of abnormal genes in other disorders of sexual differentiation is likely to provide further information about the factors required for testicular development and function.

DNA-Binding Proteins↗
PubMed2003

Expression of estrogen receptors alpha and beta in the fetal baboon testis and epididymis.

Although studies in transgenic mice suggest that estrogen is important for development of the testis, very little is known about the potential role of estrogen in maturation of the primate fetal testis. Therefore, as a first step to determine whether estrogen regulates maturation of the fetal primate testis, we used immunocytochemistry to determine estrogen receptor (ER) alpha and beta expression in the fetal baboon testis. Second, we established methods to quantify ERbeta mRNA levels by competitive reverse transcription-polymerase chain reaction in Sertoli cells isolated by laser capture microdissection (LCM) from the fetal baboon testis. ERbeta protein expression was abundant in the nuclei of Sertoli, peritubular, and interstitial cells in baboon fetuses at mid (Day 100) and late (Day 165) gestation (term is 184 days). ERbeta mRNA level was 0.03 attomole/femtomole 18S rRNA in Sertoli cell nuclei and associated cytoplasm isolated by LCM. ERalpha was expressed in low level in seminiferous tubules and in moderate level in peritubular cells on Day 165. Germ cells expressed very little ERalpha or ERbeta protein, whereas the baboon fetal epididymis exhibited extensive ERalpha and ERbeta immunostaining at mid- and late gestation. In contrast to the robust expression of ERbeta, androgen receptor protein was not demonstrable within the cells of the seminiferous cords but was abundantly expressed in epididymal epithelial cells of the fetal baboon. In summary, the results of this study show that the fetal baboon testis and epididymis expressed the ERalpha and ERbeta, and we suggest that our nonhuman primate baboon model can be used to study the potential role of estrogen on maturation of the fetal testis.

3-Hydroxysteroid Dehydrogenases↗
PubMed1990

[Venous drainage of the testis and the causes of the development of varicocele in children].

The article discusses the results of angiological examination of 42 children with primary and 13 with recurrent varicocele by the method of ++trans-scrotal antegrade venotesticulography. Three groups of patients were distinguished: I--with drainage of blood into the left testicular vein, II--with drainage into the left cremasteric vein, III--with simultaneous drainage into the two above-indicated veins. Incompetence of the valvular apparatus of the left testicular vein and impaired blood drainage from the left external iliac vein with the development of retrograde flow of blood along the left cremasteric vein are the most frequent causes of varicocele in children.

Adolescent↗
PubMed2006

Identification of a dendritic cell population in normal testis and in chronically inflamed testis of rats with autoimmune orchitis.

Experimental autoimmune orchitis (EAO) in the rat is the primary chronic animal model for the investigation of one of the main causes of male infertility, viz., testicular inflammation. Dendritic cells (DC) are potent antigen-presenting cells that play a fundamental role in autoimmune disease. We investigated the number of DC in normal testis and examined whether DC infiltrated the testis during the development of EAO. EAO was induced by active immunization with testis homogenate and adjuvants in two strains of rat (Wistar and Sprague Dawley). The presence of DC in testis was determined, 50 and 80 days after the first immunization, by immunohistochemical staining with specific antibodies (OX-62 and CD11c), and then the total number of DC was measured by stereological analysis. Labeled cells were found only in the interstitial compartment and within granulomas of EAO animals. The number of DC in EAO testes increased compared with control rats in both strains, whereas the number of OX-62+ and CD11c+ cells in adjuvant controls remained unchanged compared with untreated rats. Interspecies variations in the quantity of DC were found, with the total number of DC per testis in untreated and adjuvant control Sprague-Dawley rats being about three times higher than that seen in Wistar rats. Moreover, the increase in DC numbers at 80 days was less prominent in EAO testes of Sprague-Dawley rats than in the Wistar strain in which EAO was more severe and showed a higher number of granulomae. Thus, we have identified the DC population in normal and chronically inflamed testis. The increase in DC observed in EAO suggests that, under inflammatory conditions, the modified action(s) of these cells is a factor in the induction of the autoimmune response in testis.

Animals↗
PubMed1983

Compensatory development of a patent vascular supply to the testis after intra-abdominal transection of its main blood vessels.

The compensatory development of testicular vascular supply was studied in the pig after intra-abdominal transection of the testicular artery and vein at a young age (2 months). Post-pubertally (6 1/2 months) in these animals, normal spermatogenic epithelium and testosterone values were found. Functionally important anastomoses developed from latent connections between the vasal and testicular arteries at the coiled part of the latter and on the surface of the testis. Blood supply to the testes of operated animals reached 80% of values measured in control animals.

Animals↗
PubMed2000

Role of neurotropins in rat embryonic testis morphogenesis (cord formation).

The process of seminiferous cord formation is the first morphological event that differentiates a testis from an ovary and indicates male sex determination. Cord formation occurs by embryonic Day 14 (Day 0 = plug date; E14) in the rat. A series of experiments were conducted to determine if neurotropins and their receptors are important for the process of rat embryonic cord formation. The expression of low affinity neurotropin receptor (p75/LNGFR) was determined by immunohistochemistry on sections of both testis and ovary from E13 through birth (Day 0, P0) with an antibody to p75/LNGFR. The staining for p75/LNGFR was present in the mesonephros of E13 gonads and in a sex-specific manner appeared around developing cords at E14 in the embryonic testis. At birth, staining for p75/LNGFR was localized to a single layer of cells (i.e., peritubular cells) that surrounded the seminiferous cords. The genes for both neurotropin 3 (NT3) and for corresponding high affinity neurotropin trkC receptor were found to be expressed in the E14 rat testis, as well as other neurotropins and receptors. Immunocytochemical analysis of E14 rat testis demonstrated that NT3 was localized to the Sertoli cells and trkC was present in individual cells of the interstitium at E16 and in selected preperitubular cells at E18. Previously, the peritubular cells adjacent to the cords were demonstrated to be derived from migrating mesonephros cells around the time of cord formation. To determine if neurotropins were involved in cord formation, the actions of neurotropins were inhibited. A high affinity neurotropin receptor (trk)-specific kinase inhibitor, K252a, was used to treat organ cultures of testes from E13 rats prior to cord formation. Treatment of E13 testis organ cultures with K252a completely inhibited cord formation. K252a-treated organ cultures of E14 testis that contained cords did not alter cord morphology. A second experiment to inhibit neurotropin actions utilized a specific antagonist trk-IgG chimeric fusion protein and E13 testis organ cultures. The trk-IgG molecules dimerize with endogenous trk receptors and inhibit receptor signaling and activation of ligand function. Forty percent of E13 testis organ cultures treated with trkC-IgG had significantly reduced cord formation. TrkA-IgG had no effect on initiation of cords; however, in fifty percent of the treated organs, a "swollen" appearance of the cord structures was observed. Experiments using trkB-IgG chimeric protein on E13 organ cultures had no effect on cord formation or cord morphology. The testes from trkC and NT3 knockout mice were examined to determine if there were any morphological differences in the testis. NT3 knockouts appeared to have normal cord morphology in E15 and E17 testis. TrkC knockout mice also had normal cord morphology in E14 and P0 testis. Both NT3 and trkC knockout-mice testis had less interstitial area than wild-type controls. In addition, the trkC knockout mice have an increased number of cells expressing p75LNGFR within the cords when compared to controls or NT3 knockout mice. Combined observations suggest compensation between the different neurotropin ligands, receptors, and/or possibly different growth factors for this critical biological process. In summary, results suggest a novel nonneuronal role for neurotropins in the process of cord formation during embryonic rat testis development. The hypothesis developed is that neurotropins are involved in the progression of male sex differentiation and are critical for the induction of embryonic testis cord formation.

Animals↗
PubMed2005

Testis structure and function in a nongenetic hyperadipose rat model at prepubertal and adult ages.

There are few data for hormonal levels and testis structure and function during postnatal development in rats neonatally treated with monosodium L-glutamate (MSG). In our study, newborn male pups were ip injected with MSG (4 mg/g body weight) every 2 d up to 10 d of age and investigated at prepubertal and adult ages. Plasma levels of leptin, LH, FSH, prolactin, testosterone (T), corticosterone, and free T4 (FT4) were measured. MSG rats displayed elevated circulating levels of corticosterone and hyperadiposity/hyperleptinemia, regardless of the age examined; conversely, circulating prolactin levels were not affected. Moreover, prepubertal MSG rats revealed a significant (P < 0.05) reduction in testis weight and the number of Sertoli (SC) and Leydig cells per testis. Leptin plasma levels were severalfold higher (2.41 vs. 8.07; P < 0.05) in prepubertal MSG rats, and these animals displayed plasma LH, FSH, T, and FT4 levels significantly decreased (P < 0.05). Taken together, these data indicate that testis development, as well as SC and Leydig cell proliferation, were disturbed in prepubertal MSG rats. Adult MSG rats also displayed significantly higher leptin plasma levels (7.26 vs. 27.04; P < 0.05) and lower (P < 0.05) LH and FSH plasma levels. However, T and FT4 plasma levels were normal, and no apparent alterations were observed in testis structure of MSG rats. Only the number of SCs per testis was significantly (P < 0.05) reduced in the adult MSG rats. In conclusion, although early installed hyperadipose/hyperleptinemia phenotype was probably responsible for the reproductive axis damages in MSG animals, it remains to be investigated whether this condition is the main factor for hypothalamus-pituitary-gonadal axis dysfunction in MSG rats.

Adipose Tissue↗
PubMed1980

The effect of the Kn gene of the sexual development of cockerels.

The sexual development of cockerels of three feather growth rate genotypes, k+/k+, Kn/k+, and Kn/Kn, was studied at 2-week intervals from ages 1 to 31 weeks. Body, testis, and comb weights were collected. Histologic evaluation of testes and semen fertility tests were also made. The Kn gene, when homozygous, delayed body growth, and testis growth and development in homozygous males, thus delaying their sexual maturity 2 to 3 weeks. Body weights, relative testis weights, and seminiferous tubule diameters were similar for the k+/k+ and Kn/k+ males but significantly different from the Kn/Kn males. Stages of spermatozoic development were not significantly different between males of any of the genotypes. Regressions of relative testis weight on body weight and of seminiferous tubule size and stage of spermatozoic development on relative testis weight were not different for any of the genotypes. Relative comb size was significantly different between males of all three genotypes. When regressed against relative testis weight, the Kn/Kn males were significantly different from the other two groups of males. The Kn gene exerted an influence, directly or indirectly, which appeared to reduce testosterone production in the Kn/Kn males. The nature of the Kn gene's action was not evident from these data, nor was it clear whether it was acting on the Leydig cells of the testes or on the lutinizing hormone producing cells of the pituitary.

Animals↗
PubMed2004

A Sertoli cell-selective knockout of the androgen receptor causes spermatogenic arrest in meiosis.

Androgens control spermatogenesis, but germ cells themselves do not express a functional androgen receptor (AR). Androgen regulation is thought to be mediated by Sertoli and peritubular myoid cells, but their relative roles and the mechanisms involved remain largely unknown. Using Cre/loxP technology, we have generated mice with a ubiquitous knockout of the AR as well as mice with a selective AR knockout in Sertoli cells (SC) only. Mice with a floxed exon 2 of the AR gene were crossed with mice expressing Cre recombinase ubiquitously or selectively in SC (under control of the anti-Müllerian hormone gene promoter). AR knockout males displayed a complete androgen insensitivity phenotype. Testes were located abdominally, and germ cell development was severely disrupted. In contrast, SC AR knockout males showed normal testis descent and development of the male urogenital tract. Expression of the homeobox gene Pem, which is androgen-regulated in SC, was severely decreased. Testis weight was reduced to 28% of that in WT littermates. Stereological analysis indicated that the number of SC was unchanged, whereas numbers of spermatocytes, round spermatids, and elongated spermatids were reduced to 64%, 3%, and 0% respectively of WT. These changes were associated with increased germ cell apoptosis and grossly reduced expression of genes specific for late spermatocyte or spermatid development. It is concluded that cell-autonomous action of the AR in SC is an absolute requirement for androgen maintenance of complete spermatogenesis, and that spermatocyte/spermatid development/survival critically depends on androgens.

Animals↗
PubMed1990

Functional coupling of neonatal rat Sertoli cells and gonocytes in coculture.

Interaction between Sertoli cells and germ cells is likely to be critical for normal development of the testis. We have established and characterized cocultures of neonatal Sertoli cells and gonocytes and have begun to study the physical and functional relationship between these cells in vitro. Cells were isolated from rat pups by sequential enzymatic treatment and cultured in serum-free medium. When plated on Matrigel, Sertoli cells rapidly attach, and gonocytes adhere to the underlying Sertoli cells shortly thereafter. We observed that some of these germ cells develop cytoplasmic processes and elongate during the first day of culture, essentially mimicking their behavior in vivo. Electron microscopic examination of typical cultures revealed the presence of desmosome-like adhesion sites and apparent gap junctions between Sertoli cells and gonocytes. To determine whether Sertoli cells and gonocytes are functionally coupled in the cocultures, we used the glass bead-loading technique of McNeil and Warder to introduce Lucifer yellow (LY), a gap junction-permeant probe, and Rhodamine-dextran (RD), a larger marker excluded by gap junctions, simultaneously into cultures 24 h after plating. Immediate fixation and viewing of cultures with fluorescence microscopy indicated that all bead-loaded cells received both probes. We studied other living cultures 10 min after bead-loading and located RD-negative (i.e. nonbead-loaded) gonocytes that were in obvious contact with RD- and LY-positive bead-loaded Sertoli cells; these gonocytes were scored for the presence or absence of cytoplasmic LY. This analysis revealed that many gonocytes were able to obtain LY from adjacent Sertoli cells, presumably via gap junctions maintained with these cells. In addition, we quantified the percentage of gonocytes that elongated with increasing time in vitro and correlated the morphology of these cells with their ability to acquire LY from adjacent Sertoli cells. Our findings indicate that although the absolute numbers of gonocytes present decreases, more of those remaining elongate as time in vitro increases. We can also conclude from our data that gonocytes with and without processes are equally likely to be coupled with Sertoli cells under these conditions. These observations provide the first demonstration of functional coupling between Sertoli cells and premeiotic germ cells. Together with our morphological observations, they suggest that gap junction-mediated communication between these cells may be involved in stimulating or regulating changes in the gonocyte population during postnatal development of the testis.

Animals↗
PubMed1993

Effects of age and calcium ion on testis carbonyl reductase in rats.

To examine the role of carbonyl reductase (CR) in the development and function of testis, age-related changes in CR and the effect of exogenous calcium on CR in rat testis were studied. Testicular CR activity was the highest at 3 weeks of age when the enzyme activity was measured at 2, 3, 4, 8 and 20 weeks of age. The intensity of positive protein bands in testicular cytosol was similar among these age groups in Western blot analysis with anti-rat ovarian CR antibody. In 3-week-old rats, intravenous administration of 4 mg/kg calcium markedly suppressed the activity to about 50% of the control level 1 min after the treatment. Pretreatment with nicardipine prevented the inhibitory effect of exogenous calcium on the testicular CR activity in 3-week-old rats, indicating that the suppressing action of calcium on the enzyme activity was mediated by the entry of extracellular calcium via calcium channels. There were no significant changes in the CR activity following the treatment with calcium and nicardipine in the other 3 age groups examined. These findings suggest that testicular CR plays an important role in the functional development of the testis during the infantile period in rats.

Aging↗
PubMed1992

Developmental expression of the S35-S45/SGP-2/TRPM-2 gene in rat testis and epididymis.

Testosterone-repressed prostate message-2 (TRPM-2) was originally isolated and cloned from the regressing ventral prostate of the rat. In this tissue, and in other hormone-dependent tissues such as the mammary gland, this gene is induced in the absence of the appropriate trophic hormone. Sequence analysis of the cDNA and genomic clones of TRPM-2 have demonstrated that the coding sequence of this gene is identical to S35-S45 (also known as SGP-2 and clusterin), which is constitutively expressed by the Sertoli cells of the adult testis. Using Northern, slot blot, S1-nuclease analysis, and in situ hybridization, we have investigated the regulation of TRPM-2 expression in the testis and epididymis during development. Slot blot analysis of RNA extracted from the testis and epididymis of 7-, 14-, 28-, 35-, and 91-day-old rats demonstrates that the gene is induced to detectable levels between days 7 and 14 and that the relative level of expression does not change significantly after day 14. In situ hybridization using frozen sections of testis from day 2-, 7-, 14-, 28-, 35-, and 91-day-old rats confirms that there is little expression of TPRM-2 in the seminiferous epithelium of 7-day-old rats, but this increases considerably after 14 days, primarily in Sertoli cells but also in association with meiotic developing spermatogenic cells. However, TRPM-2 mRNA is expressed in the rete testis at 2 days of age, reaches a peak at 35 days of age, and continues to be expressed in the adult. Slot blot analysis demonstrates that TRPM-2 is also induced in the epididymis between 7 and 14 days of age, although, as has been demonstrated by in situ hybridization, TRPM-2 mRNA is detectable in the epithelial cells in the head of the epididymis but is barely detectable in the midportion or tail regions. Northern analysis suggests that the size of the TRPM-2 transcript in the testis also changes during development. In the early stages of testicular development, the TRPM-2 transcript appears to be a broad band of approximately 1.5 kb, while the transcript in the adult appears to be approximately 1.8 kb in length. S1-nuclease protection assays suggest that this increase in size is not due to differential splicing of the first exon of TRPM-2/SGP-2 and most probably reflects a difference in the polyadenylation of the mRNA in the testis at different times during development.

Animals↗
PubMed1998

Occludin is concentrated at tight junctions of mouse/rat but not human/guinea pig Sertoli cells in testes.

Occludin is the only integral membrane protein identified to date as a component of tight junctions (TJs). Here, we examined the distribution and expression of occludin in murine testis bearing well-developed TJ. In the adult mouse testis, occludin was concentrated at TJ strands, which are located at the most basal regions of lateral membranes of Sertoli cells. In immunoblotting, occludin showed a characteristic multiple banding pattern, suggesting that occludin is highly phosphorylated in the testis. In 1-wk-old mouse testis, occludin was distributed diffusely at the lateral membranes of Sertoli cells, and even at this stage, highly phosphorylated occludin was detected. With development, occludin gradually became concentrated at the most basal regions of Sertoli cells. The same results were obtained in rat, but unexpectedly occludin was not detected in human or guinea pig Sertoli cells by immunofluorescence microscopy as well as by immunoblotting. Inasmuch as TJs are also well developed in Sertoli cells of these species, we concluded that, at least in the testes of these species, there are some Sertoli cell-specific isoforms of occludin or other TJ-associated integral membrane proteins that differ from occludin.

Animals↗
PubMed1995

The marsupial male: a role model for sexual development.

Sexual differentiation in male marsupials has many similarities with that of eutherians. Marsupials have an XX-XY sex determining mechanism, and have a homologue of the testis-determining SRY gene on their Y-chromosome. However, the development pattern of SRY gene expression is different from the mouse in that it is expressed for a much longer period. SRY is expressed in a range of non-gonadal tissues in male pouch young and adults which is similar to the human pattern, and raises questions as to its particular role(s) in sexual differentiation. Similarly Müllerian inhibiting substance (MIS) is produced in the developing testis over a longer period than in the mouse. Since ovaries cultured with MIS or transplanted into male recipient pouch young develop tubular structures, MIS may induce Sertoli cell formation. Testosterone is produced by the neonatal testis, and this stimulates Wolffian duct development to form the vas deferens and epididymis. Virilization of urogenital sinus is also androgen-dependent. However, virilization of the prostate and phallus occurs more than three weeks after the onset of testosterone production, suggesting that the timing of this may be regulated by delayed activation of the androgen receptor pathway. Unlike in eutherians, differentiation of the scrotum and mammary glands is not dependent on testicular hormones, but is independently regulated by an X-linked genetic mechanism. Clearly marsupials provide a unique perspective to help us clarify the mechanisms underlying sexual development in all mammals.

Androgens↗