Generation of Rat Monoclonal Antibodies Specific for Ad4BPSF-1

FEAT enhances INSL3 expression in testicular Leydig cells

FEAT, the protein encoded by methyltransferase-like 13 (METTL13), is aberrantly upregulated in most human cancers and potently drives tumorigenesis in vivo; however, its role in normal tissues remains elusive. Immunoblotting has displayed weak FEAT expression in normal human tissues, including the testis. Here, we found that FEAT is expressed in fetal and adult Leydig cells in the testis. FEAT knockdown using siRNA increased primary cilia formation in MA-10 Leydig tumor cells, accompanied by enhanced 5' adenosine monophosphate-activated protein kinase (AMPK) activation. Immunofluorescence analyses of FEAT-silenced MA-10 cells showed diminished insulin-like factor 3 (INSL3) expression. A male Mettl13^+/- mouse developed bilateral intraabdominal cryptorchidism, suggesting defective INSL3 production by fetal Leydig cells. Leydig cells from the mouse showed markedly decreased INSL3 protein by immunohistochemistry. Together, these results suggest that FEAT facilitates the INSL3 production in testicular Leydig cells that is essential for transabdominal testis migration.

Isolation and Characterization of Fetal Leydig Progenitor Cells of Male Mice

Fetal and adult Leydig cells develop in mammalian prenatal and postnatal testes, respectively. In mice, fetal Leydig cells (FLCs) emerge in the interstitial space of the testis at embryonic day 12.5 and thereafter increase in number, possibly through differentiation from progenitor cells. However, the progenitor cells have not yet been identified. Previously, we established transgenic mice in which FLCs are labeled strongly with enhanced green fluorescent protein (EGFP). Interestingly, fluorescence-activated cell sorting provided us with weakly EGFP-labeled cells as well as strongly EGFP-labeled FLCs. In vitro reconstruction of fetal testes demonstrated that weakly EGFP-labeled cells contain FLC progenitors. Transcriptome from the 2 cell populations revealed, as expected, marked differences in the expression of genes required for growth factor/receptor signaling and steroidogenesis. In addition, genes for energy metabolisms such as glycolytic pathways and the citrate cycle were activated in strongly EGFP-labeled cells, suggesting that metabolism is activated during FLC differentiation.

Aristaless related homeobox gene, Arx, is implicated in mouse fetal Leydig cell differentiation possibly through expressing in the progenitor cells

Development of the testis begins with the expression of the SRY gene in pre-Sertoli cells. Soon after, testis cords containing Sertoli and germ cells are formed and fetal Leydig cells subsequently develop in the interstitial space. Studies using knockout mice have indicated that multiple genes encoding growth factors and transcription factors are implicated in fetal Leydig cell differentiation. Previously, we demonstrated that the Arx gene is implicated in this process. However, how ARX regulates Leydig cell differentiation remained unknown. In this study, we examined Arx KO testes and revealed that fetal Leydig cell numbers largely decrease throughout the fetal life. Since our study shows that fetal Leydig cells rarely proliferate, this decrease in the KO testes is thought to be due to defects of fetal Leydig progenitor cells. In sexually indifferent fetal gonads of wild type, ARX was expressed in the coelomic epithelial cells and cells underneath the epithelium as well as cells at the gonad-mesonephros border, both of which have been described to contain progenitors of fetal Leydig cells. After testis differentiation, ARX was expressed in a large population of the interstitial cells but not in fetal Leydig cells, raising the possibility that ARX-positive cells contain fetal Leydig progenitor cells. When examining marker gene expression, we observed cells as if they were differentiating into fetal Leydig cells from the progenitor cells. Based on these results, we propose that ARX acts as a positive factor for differentiation of fetal Leydig cells through functioning at the progenitor stage.

A report of two novel NR5A1 mutation families: possible clinical phenotype of psychiatric symptoms of anxiety and/or depression

OBJECTIVE

NR5A1 or steroidogenic factor 1 is a nuclear receptor that plays important roles in the hypothalamus-pituitary-steroidogenic axis. The clinical phenotype of most 46,XY mutation carriers includes disorders of sex development (DSD) without adrenal insufficiency, whereas 46,XX mutation carriers have phenotypes ranging from no symptoms to ovarian insufficiency. Although genetically engineered ventromedial hypothalamus-specific Nr5a1 knockout mice show anxiety behaviour, no psychiatric symptoms have been reported in human NR5A1 mutation carriers. We report clinical and molecular findings for individuals (from two families) with NR5A1 mutations, showing psychiatric symptoms.

DESIGN AND METHODS

We screened for NR5A1 mutations in a cohort of 34 patients with 46,XY DSD using PCR-based sequencing. Psychiatric symptoms were assessed using mental health assessment tools and structured clinical interviews. Functional properties of detected mutant NR5A1s were studied in silico and in vitro, including three-dimensional (3D) mutation models, subcellular NR5A1 protein localization and transactivation assays.

RESULTS

We found 2 (46,XY) patients with NR5A1 heterozygous novel mutations (p.D257fs and p.V424del), which were transmitted from their respective mothers. The patients' clinical findings indicated DSD without adrenal insufficiency. Both mothers showed psychiatric symptoms, including excessive anxiety and/or depression. The mother and grandmother of one patient had premature ovarian insufficiency. Functional studies showed altered 3D models of p.V424del and normal subcellular NR5A1 localization and impaired transcriptional activation without dominant-negative effects in both mutations.

CONCLUSIONS

We found 2 (46,XX) NR5A1 mutation carriers with excessive anxiety and/or depression. These results suggest that excessive anxiety and/or depression are possible clinical phenotypes of 46,XX NR5A1 mutations.

Contribution of Leydig and Sertoli cells to testosterone production in mouse fetal testes

Testosterone is a final product of androgenic hormone biosynthesis, and Leydig cells are known to be the primary source of androgens. In the mammalian testis, two distinct populations of Leydig cells, the fetal and the adult Leydig cells, develop sequentially, and these two cell types differ both morphologically and functionally. It is well known that the adult Leydig cells maintain male reproductive function by producing testosterone. However, it has been controversial whether fetal Leydig cells can produce testosterone, and the synthetic pathway of testosterone in the fetal testis is not fully understood. In the present study, we generated transgenic mice in which enhanced green fluorescence protein was expressed under the control of a fetal Leydig cell-specific enhancer of the Ad4BP/SF-1 (Nr5a1) gene. The transgene construct was prepared by mutating the LIM homeodomain transcription factor (LHX9)-binding sequence in the promoter, which abolished promoter activity in the undifferentiated testicular cells. These transgenic mice were used to collect highly pure fetal Leydig cells. Gene expression and steroidogenic enzyme activities in the fetal Leydig cells as well as in the fetal Sertoli cells and adult Leydig cells were analyzed. Our results revealed that the fetal Leydig cells synthesize only androstenedione because they lack expression of Hsd17b3, and fetal Sertoli cells convert androstenedione to testosterone, whereas adult Leydig cells synthesize testosterone by themselves. The current study demonstrated that both Leydig and Sertoli cells are required for testosterone synthesis in the mouse fetal testis.

Cbx2, a polycomb group gene, is required for Sry gene expression in mice

Mice lacking the function of the polycomb group protein CBX2 (chromobox homolog 2; also known as M33) show defects in gonadal, adrenal, and splenic development. In particular, XY knockout (KO) mice develop ovaries but not testes, and the gonads are hypoplastic in both sexes. However, how CBX2 regulates development of these tissues remains largely unknown. In the present study, we used microarray, RT-PCR, and immunohistochemical analyses to show that the expression of Sry, Sox9, Lhx9, Ad4BP/SF-1, Dax-1, Gata4, Arx, and Dmrt1, genes encoding transcription factors essential for gonadal development, is affected in Cbx2 KO gonads. Male-to-female sex reversal in Cbx2 KO mice was rescued by crossing them with transgenic mice displaying forced expression of Sry or Sox9. However, testes remained hypoplastic in these mice, indicating that the size and the sex of the gonad are determined by different sets of genes. Our study implicates Cbx2 in testis differentiation through regulating Sry gene expression.

Identification of an enhancer in the Ad4BP/SF-1 gene specific for fetal Leydig cells

Adrenal 4 binding protein/steroidogenic factor 1 (Ad4BP/SF-1) (Nr5a1) is a nuclear receptor essential for reproductive tissue development and endocrine regulation. This factor is expressed in steroidogenic tissues (e.g. adrenal glands and gonads), and expression of this factor is tightly regulated in a tissue and cell type-specific manner. Our previous studies have identified tissue and cell type-specific enhancers in the introns of the Ad4BP/SF-1 gene in fetal adrenal glands, ventromedial hypothalamus, and pituitary gonadotrope. Characterization of the enhancers had provided new insights into tissue and cell development. However, these studies have failed to identify any gonad-specific enhancer. Here, we identified a fetal Leydig cell-specific enhancer in the upstream region of the mouse Ad4BP/SF-1 gene using transgenic mouse assays. Alignment of the upstream regions among vertebrate animal species demonstrated that the enhancer consisted of three conserved regions, whereby the most highly conserved region contained an Ad4BP/SF-1 binding sequence and an E-box. Mutation of each sequence abolished the enhancer activity and led to a loss of reporter gene expression. These results suggested that Ad4BP/SF-1 gene expression in the fetal Leydig cell is regulated by a yet unidentified E-box binding protein(s) and by an autoregulatory loop formed by Ad4BP/SF-1. Although fetal Leydig cells have been thought to play crucial roles for masculinization of various fetal tissues through androgen production, other functions have remained elusive. Our identification of a fetal Leydig cell-specific enhancer in the Ad4BP/SF-1 gene would be a powerful tool to address these gaps in the knowledge base.

Rat monoclonal antibody specific for septin 9

The septin family of GTPase proteins has been shown to be important for cell division, cytoskeletal organization, and membrane-remodeling events. Septin 9 (SEPT9) is a member of the septin family (also designated MSF/eseptin/Sint1) and has been implicated in tumorigenesis. The present study reports on the preparation and properties of a monoclonal antibody (MAb) directed against SEPT9. The antibody was produced by hybridization of mouse myeloma cells with lymph node cells from an immunized rat. The MAb 7B5 specifically recognized SEPT9, as evidenced by immunoblotting using a variety of extracts from cultured cells. In immunostaining using MAb 7B5, a filamentous pattern near the plasma membrane was observed. The MAb 7B5 promises to be useful in immunoblotting and immunostaining experiments in various cells and tissues to determine the expression levels of SEPT9, as well as to further the analysis of the biological function of this protein.