Gonadotropins, via cAMP, negatively regulate GATA-1 gene expression in testicular cells

ABCC4 impacts megakaryopoiesis and protects megakaryocytes against 6-mercaptopurine induced cytotoxicity

The role of ABCC4, an ATP-binding cassette transporter, in the process of platelet formation, megakaryopoiesis, is unknown. Here, we show that ABCC4 is highly expressed in megakaryocytes (MKs). Mining of public genomic data (ATAC-seq and genome wide chromatin interactions, Hi-C) revealed that key megakaryopoiesis transcription factors (TFs) interacted with ABCC4 regulatory elements and likely accounted for high ABCC4 expression in MKs. Importantly these genomic interactions for ABCC4 ranked higher than for genes with known roles in megakaryopoiesis suggesting a role for ABCC4 in megakaryopoiesis. We then demonstrate that ABCC4 is required for optimal platelet formation as in vitro differentiation of fetal liver derived MKs from Abcc4-/- mice exhibited impaired proplatelet formation and polyploidization, features required for optimal megakaryopoiesis. Likewise, a human megakaryoblastic cell line, MEG-01 showed that acute ABCC4 inhibition markedly suppressed key processes in megakaryopoiesis and that these effects were related to reduced cAMP export and enhanced dissociation of a negative regulator of megakaryopoiesis, protein kinase A (PKA) from ABCC4. PKA activity concomitantly increased after ABCC4 inhibition which was coupled with significantly reduced GATA-1 expression, a TF needed for optimal megakaryopoiesis. Further, ABCC4 protected MKs from 6-mercaptopurine (6-MP) as Abcc4-/- mice show a profound reduction in MKs after 6-MP treatment. In total, our studies show that ABCC4 not only protects the MKs but is also required for maximal platelet production from MKs, suggesting modulation of ABCC4 function might be a potential therapeutic strategy to regulate platelet production.

GATA-1 mutation alters the spermatogonial phase and steroidogenesis in adult mouse testis

GATA-1 is a transcription factor from the GATA family, which features zinc fingers for DNA binding. This protein was initially identified as a crucial regulator of blood cell differentiation, but it is currently known that the Gata-1 gene expression is not limited to this system. Although the testis is also a site of significant GATA-1 expression, its role in testicular cells remains considerably unexplored. In the present study, we evaluated the testicular morphophysiology of adult ΔdblGATA mice with a mutation in the GATA-1 protein. Regarding testicular histology, GATA-1 mutant mice exhibited few changes in the seminiferous tubules, particularly in germ cells. A high proportion of differentiated spermatogonia, an increased number of apoptotic pre-leptotene spermatocytes (Caspase-3-positive), and a high frequency of sperm head defects were observed in ΔdblGATA mice. The main differences were observed in the intertubular compartment, as ΔdblGATA mice showed several morphofunctional changes in Leydig cells. Reduced volume, increased number and down-regulation of steroidogenic enzymes were observed in ΔdblGATA Leydig cells. Moreover, the mutant animal showed lower serum testosterone concentration and high LH levels. These results are consistent with the phenotypic and biometric data of mutant mice, i.e., shorter anogenital index and reduced accessory sexual gland weight. In conclusion, our findings suggest that GATA-1 protein is an important factor for germ cell differentiation as well as for the steroidogenic activity in the testis.

Common markers of testicular Sertoli cells

INTRODUCTION

Sertoli cells play central roles in the development of testis formation in fetuses and the initiation and maintenance of spermatogenesis in puberty and adulthood, and disorders of Sertoli cell proliferation and/or functional maturation can cause male reproductive disorders at various life stages. It's well documented that various genes are either overexpressed or absent in Sertoli cells during the conversion of an immature, proliferating Sertoli cell to a mature, non-proliferating Sertoli cell, which are considered as Sertoli cell stage-specific markers. Thus, it is paramount to choose an appropriate Sertoli cell marker that will be used not only to identify the developmental, proliferative, and maturation of Sertoli cell status in the testis during the fetal period, prepuberty, puberty, or in the adult, but also to diagnose the mechanisms underlying spermatogenic dysfunction.

AREAS COVERED

In this review, we principally enumerated 5 categories of testicular Sertoli cell markers - including immature Sertoli cell markers, mature Sertoli cell markers, immature/mature Sertoli cell markers, Sertoli cell functional markers, and others.

EXPERT OPINION

By delineating the characteristics and applications of more than 20 Sertoli cell markers, this review provided novel Sertoli cell markers for the more accurate diagnosis and mechanistic evaluation of male reproductive disorders.

Baicalin inhibits recruitment of GATA1 to the HSD3B2 promoter and reverses hyperandrogenism of PCOS

High androgen levels in patients suffering from polycystic ovary syndrome (PCOS) can be effectively reversed if the herb Scutellaria baicalensis is included in traditional Chinese medicine prescriptions. To characterize the effects of baicalin, extracted from S. baicalensis, on androgen biosynthesis in NCI-H295R cells and on hyperandrogenism in PCOS model rats and to elucidate the underlying mechanisms. The optimum concentration and intervention time for baicalin treatment of NCI-H295R cells were determined by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide and enzyme-linked immunosorbent assays. The functional genes affected by baicalin were studied by gene expression profiling (GEP), and the key genes were identified using a dual luciferase assay, RNA interference technique, and genetic mutations. Besides, hyperandrogenic PCOS model rats were induced and confirmed before and after baicalin intervention. As a result, Baicalin decreased the testosterone concentrations in a dose-and time-dependent manner in NCI-H295R cells. GEP revealed that 3β-hydroxysteroid dehydrogenase type II (HSD3B2) was the key enzyme of androgen biosynthesis, and baicalin inhibited the expression of HSD3B2 by regulating the binding of transcription factor GATA-binding factor 1 (GATA1) to the HSD3B2 promoter. Hyperandrogenic PCOS model rats treated with baicalin significantly reversed the high androgen levels of serum and the abnormal ovarian status, restored the estrous cyclicity, and decreased the expression of HSD3B2 in ovarian. In summary , our data revealed that GATA1 is an important transcription factor activating the HSD3B2 promoter in steroidogenesis, and baicalin potentially be an effective therapeutic agent for hyperandrogenism in PCOS by inhibiting the recruitment of GATA1 to the HSD3B2 promoter in ovarian tissue.

The expression of CKLFSF2B is regulated by GATA1 and CREB in the Leydig cells, which modulates testicular steroidogenesis

CKLFSF is a protein family that serves as a functional bridge between chemokines and members of the transmembrane 4 superfamily (TM4SF). In the course of evolution, CKLFSF2 has evolved as two isoforms, namely CKLFSF2A and CKLFSF2B, in mice. CKLFSF2A, also known as CMTM2A and ARR19, is expressed in the testis and is important for testicular steroidogenesis. CKLFSF2B is also known to be highly expressed in the testis. In the prepubertal stage, CKLFSF2B is expressed only in Leydig cells, but it is highly expressed in haploid germ cells and Leydig cells in adult testis. CKLFSF2B is naturally processed inside the cell at its C-terminus to yield smaller proteins compared to its theoretical size of ≈25 kDa. The Cklfsf2b gene is regulated by GATA-1 and CREB protein, binding to their respective binding elements present in the 2-kb upstream promoter sequence. In addition, the overexpression of CKLFSF2B inhibited the activity of the Nur77 promoter, which consequently represses the promoter activity of Nur77-target steroidogenic genes such as P450c17, 3β-HSD, and StAR in MA-10 Leydig cells. Adenovirus-mediated overexpression of CKLFSF2B in primary Leydig cells isolated from adult mice shows a repression of steroidogenic gene expression and consequently testosterone production. Moreover, intratesticular injection of CKLFSF2B-expressing adenovirus in adult mice clearly had a repressive effect compared to the control injected with only GFP-expressing adenovirus. Altogether, these findings suggest that CKLFSF2B might be involved in the development and function of Leydig cells and regulate testicular testosterone production by fine-tuning the expression of steroidogenic genes.

The Role of GATA in Mammalian Reproduction

GATA transcription factors are emerging as critical players in mammalian reproductive development and function. GATA-4 contributes to fetal male gonadal development by regulating genes mediating Müllerian duct regression and the onset of testosterone production. GATA-2 expression appears to be sexually dimorphic being transiently expressed in the germ cell lineage of the fetal ovary but not the fetal testis. In the reproductive system, GATA-1 is exclusively expressed in Sertoli cells at specific seminiferous tubule stages. In addition, GATA-4 and GATA-6 are localized primary to ovarian and testicular somatic cells. The majority of cell transfection studies demonstrate that GATA-1 and GATA-4 can stimulate inhibin subunit gene promoter constructs. Other studies provide strong evidence that GATA-4 and GATA-6 can activate genes mediating gonadal cell steroidogenesis. GATA-2 and GATA-3 are found in pituitary and placental cells and can regulate alpha-glycoprotein subunit gene expression. Gonadal expression and activation of GATAs appear to be regulated in part by gonadotropin signaling via the cyclic AMP-protein kinase A pathway. This review will cover the current knowledge regarding GATA expression and function at all levels of the reproductive axis.

The mechanism and control of Jagged1 expression in Sertoli cells

The regulation of Sertoli cells by some hormones and signaling factors is important for normal spermatogenesis. Notch signaling is considered to be necessary for normal spermatogenesis in mouse. In this study, we revealed two new facts about Sertoli cells by western blotting experiments on different types of primary cells and microdissected tubules. The first is that Sertoli cells express the Jagged1 ligand in mice testes. The second is that the expression level of Jagged1 oscillates in the seminiferous epithelial cycle. Therefore, we inferred that Jagged1 in Sertoli cells contributes to the Notch signaling involved in spermatogenesis. Furthermore, we examined the regulation of Jagged1 expression and found that Jagged1 expression was suppressed by cAMP signaling and was promoted by TNF-α signaling in Sertoli cells. When cAMP and TNF-α were simultaneously added to Sertoli cells, Jagged1 expression was suppressed. Therefore, cAMP signaling dominates Jagged1 expression over TNF-α signaling. These results suggest that cAMP signaling may cause the periodicity of Jagged1 expression in the seminiferous epithelial cycle, and controlling Jagged1 expression by adding TNF-α or cAMP may contribute to normal spermatogenesis in vitro.

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Jagged1 was expressed in Sertoli cells in mouse testes.

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The expression of Jagged1 oscillated in the seminiferous epithelial cycle.

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The expression of Jagged1 in Sertoli cells was upregulated by TNF-α and downregulated by cAMP.

Differential role of the estrogen receptors ESR1 and ESR2 on the regulation of proteins involved with proliferation and differentiation of Sertoli cells from 15-day-old rats

The aim of the present study was to investigate the role of each estrogen receptors on the regulation of proteins involved with proliferation and differentiation of Sertoli cells from 15-day-old rats. Activation of ESR1 by 17β-estradiol (E2) and ESR1-selective agonist PPT increased CCND1 expression, and this effect was dependent on NF-kB activation. E2 and the ESR2-selective agonist DPN, but not PPT, increased, in a PI3K and CREB-dependent manner, the expression of CDKN1B and the transcription factors GATA-1 and DMRT1. Analyzing the expression of ESR1 and ESR2 in different stages of development of Sertoli cells, we observed that the ESR1/ESR2 ratio decreased with age, and this ratio seems to be important to determine the end of cell proliferation and the start of cell differentiation. In Sertoli cells from 15-day-old rats, the ESR1/ESR2 ratio favors the effect of ESR1 and the activation of this receptor increased [Methyl-(3)H]thymidine incorporation. We propose that in Sertoli cells from 15-day-old rats E2 modulates Sertoli cell proliferation through ESR1/NF-kB-mediated increase of CCND1, and cell cycle exit and differentiation through ESR2/CREB-mediated increase of CDKN1B, GATA-1 and DMRT1. The present study reinforces the important role of estrogen for normal testis development.

ARR19 (androgen receptor corepressor of 19 kDa), an antisteroidogenic factor, is regulated by GATA-1 in testicular Leydig cells

ARR19 (androgen receptor corepressor of 19 kDa), which encodes for a leucine-rich protein, is expressed abundantly in the testis. Further analyses revealed that ARR19 was expressed in Leydig cells, and its expression was differentially regulated during Leydig cell development. Adenovirus-mediated overexpression of ARR19 in Leydig cells inhibited testicular steroidogenesis, down-regulating the expression of steroidogenic enzymes, which suggests that ARR19 is an antisteroidogenic factor. Interestingly, cAMP/luteinizing hormone attenuated ARR19 expression in a fashion similar to that of GATA-1, which was previously reported to be down-regulated by cAMP. Sequence analysis of the Arr19 promoter revealed the presence of two putative GATA-1 binding motifs. Further analyses with 5' deletion and point mutants of putative GATA-1 binding motifs showed that these GATA-1 binding sites were critical for high promoter activity. CREB-binding protein coactivated GATA-1 and markedly increased the activity of the Arr19 promoter. Both GATA-1 and CREB-binding proteins occupied the GATA-1 motifs within the Arr19 promoter, which was repressed by cAMP treatment. Altogether, these findings demonstrate that ARR19 is the target gene of GATA-1 and suggest that ARR19 gene expression in testicular Leydig cells is regulated by luteinizing hormone/cAMP signaling via the control of GATA-1 expression, resulting in the control of testicular steroidogenesis.

Role of the GATA family of transcription factors in endocrine development, function, and disease

The WGATAR motif is a common nucleotide sequence found in the transcriptional regulatory regions of numerous genes. In vertebrates, these motifs are bound by one of six factors (GATA1 to GATA6) that constitute the GATA family of transcriptional regulatory proteins. Although originally considered for their roles in hematopoietic cells and the heart, GATA factors are now known to be expressed in a wide variety of tissues where they act as critical regulators of cell-specific gene expression. This includes multiple endocrine organs such as the pituitary, pancreas, adrenals, and especially the gonads. Insights into the functional roles played by GATA factors in adult organ systems have been hampered by the early embryonic lethality associated with the different Gata-null mice. This is now being overcome with the generation of tissue-specific knockout models and other knockdown strategies. These approaches, together with the increasing number of human GATA-related pathologies have greatly broadened the scope of GATA-dependent genes and, importantly, have shown that GATA action is not necessarily limited to early development. This has been particularly evident in endocrine organs where GATA factors appear to contribute to the transcription of multiple hormone-encoding genes. This review provides an overview of the GATA family of transcription factors as they relate to endocrine function and disease.

Cloning and characterization of rat spermatid protein SSP411: a thioredoxin-like protein

In an attempt to identify new sperm-specific genes that are involved in sperm maturation, fertilization, and embryo development, such as the mammalian ortholog of the sperm-supplied protein gene, spe-11, in Caenorhabditis elegans, we cloned and characterized a new spermatid-specific protein gene, ssp411, from adult rat testes. The ssp411 cDNA shared >85% sequence identity with an unnamed human protein, FLJ21347, and an uncharacterized mouse testicular protein called transcript increased in spermiogenesis 78 (TISP78). A 2.8-kb ssp411 mRNA was expressed in a testis-specific and age-dependent manner; the mRNA was evident at 28 days and remained at high levels throughout adulthood. An SSP411 protein of molecular weight 88 000 was detected in testicular extracts by Western blot analysis. Ssp411 mRNA and SSP411 protein, as analyzed by in situ hybridization and immunohistochemistry, were both expressed in a stage-dependent fashion during the cycle of the seminiferous epithelium. The ssp411 mRNA was predominantly localized to round and elongated spermatids, with maximal expression at stages VII-XII. The SSP411 protein was mainly observed in elongated spermatids and reached its highest levels during stages V-VI. A conserved thioredoxin-like domain was detected in the N-terminal region of SSP411 and its orthologs. An analysis of the predicted 3-dimensional structural modeling and folding pattern further suggested that SSP411 is identifiable as a member of thioredoxin family. In summary, we have identified a new rat spermatid protein gene, ssp411, and its orthologs in human and mouse and demonstrated that SSP411 might belong to a testis-specific thioredoxin family. This suggests that SSP411 may play a role in sperm maturation, fertilization, and/or embryo development, as has been shown in thioredoxin family.

Biochemical assessment of intracellular signal transduction pathways in eosinophils: implications for pharmacotherapy

Allergic asthma and allergic rhinitis are inflammatory diseases of the airway. Cytokines and chemokines produced by T helper (Th) type 2 cells (GM-CSF, IL-4, IL-5, IL-6, IL-9, IL-10 and IL-13), eotaxin, transforming growth factor-beta, and IL-11 orchestrate most pathophysiological processes of the late-phase allergic reaction, including the recruitment, activation, and delayed apoptosis of eosinophils, as well as eosinophilic degranulation to release eosinophilic cationic protein, major basic protein, and eosinophil-derived neurotoxin. These processes are regulated through an extensive network of interactive intracellular signal transduction pathways that have been intensively investigated recently. Our present review updates the cytokine and chemokine-mediated signal transduction mechanisms including the RAS-RAF-mitogen-activated protein kinases, Janus kinases (signal transducers and activators of transcription), phosphatidylinositol 3-kinase, nuclear factor-kappa B, activator protein-1, GATA, and cyclic AMP-dependent pathways, and describes the roles of different signaling pathways in the regulation of eosinophil differentiation, recruitment, degranulation, and expression of adhesion molecules. We shall also discuss different biochemical methods for the assessment of various intracellular signal transduction molecules, and various antagonists of receptors, modulators, and inhibitors of intracellular signaling molecules, many of which are potential therapeutic agents for treating allergic diseases.

Transcription factor GATA-4 is activated by phosphorylation of serine 261 via the cAMP/protein kinase a signaling pathway in gonadal cells

Gonadal gene expression is regulated by pituitary hormones acting through the cAMP/protein kinase A (PKA) signal transduction pathway. The downstream molecular effectors of these signals, however, have yet to be fully understood. We have recently shown that cAMP stimulation of gonadal cells leads to phosphorylation of the transcription factor GATA-4, a key regulator of gonadal gene expression, thus suggesting that this factor might be a novel target for the cAMP/PKA signaling pathway. We now show that the rapid phosphorylation of GATA-4 induced by cAMP in vivo can be blocked by a PKA-specific inhibitor but not by mitogen-activated protein kinase inhibitors, indicating that GATA-4 is predominantly phosphorylated by PKA in response to cAMP in gonadal cells. In addition, using in vitro kinase assays, we show that PKA phosphorylation of GATA-4 occurs predominantly on an evolutionarily conserved serine residue located at position 261. Phosphorylation of GATA-4 Ser261 by PKA enhances its transcriptional activity on different gonadal promoters, an effect that was markedly reduced with a S261A mutant. Moreover, the S261A mutant blunted cAMP-induced promoter activity in gonadal cells. Finally, PKA-dependent phosphorylation of GATA-4 also led to enhanced recruitment of the CREB-binding protein coactivator. This recruitment and transcriptional cooperation were dramatically impaired with the S261A mutant. Thus, our results identify GATA-4 as a novel downstream effector of cAMP/PKA signaling in gonadal cells, where phosphorylation of Ser261 and recruitment of CREB-binding protein likely represent a key mechanism for conveying the cAMP responsiveness of gonadal genes that lack classical cAMP regulatory elements.

FOG-2 and GATA-4 Are coexpressed in the mouse ovary and can modulate mullerian-inhibiting substance expression

Transcription factor GATA-4 has been suggested to have a role in mammalian gonadogenesis, e.g., through activation of the Müllerian-inhibiting substance (MIS) gene expression. Although the expression of GATA-4 during gonadogenesis has been elucidated in detail, very little is known about FOG-2, an essential cofactor for GATA-4, in ovarian development. We explored in detail the expression of FOG-2 and GATA-4 in the fetal and postnatal mouse ovary and in the fetal testis using Northern blotting, RNA in situ hybridization, and immunohistochemistry. GATA-4 and FOG-2 are evident in the bipotential urogenital ridge, and their expression persists in the fetal mouse ovary; this result is different from earlier reports of GATA-4 downregulation in the fetal ovary. In contrast to ovary, FOG-2 expression is lost in the fetal Sertoli cells along with the formation of the testicular cords, leading to the hypothesis that FOG-2 has a specific role in the fetal ovaries counteracting the transactivation of the MIS gene by GATA-4. In vitro transfection assays verified that FOG-2 is able to repress the effect of GATA-4 on MIS transactivation in granulosa cells. In postnatal ovary, granulosa cells of growing follicles express FOG-2, partially overlapping with the expression of MIS. These data suggest an important role for FOG-2 and the GATA transcription factors in the developing ovary.