Eicosapentaenoic acid changes muscle transcriptome and intervenes in aging-related fiber type transition in male mice.

Age-related sarcopenia is associated with a variety of changes in skeletal muscle. These changes are interrelated with each other and associated with systemic metabolism, the details of which, however, are largely unknown. Eicosapentaenoic acid (EPA) is a promising nutrient against sarcopenia and has multifaceted effects on systemic metabolism. In this study, we hypothesized that the aging process in skeletal muscle can be intervened by the administration of EPA. Seventy-five-week-old male mice were assigned to groups fed an EPA-deprived diet (EPA-) or an EPA-enriched diet with 1 wt% EPA (EPA+) for 12 wk. Twenty-four-week-old male mice fed with normal chow were also analyzed. At baseline, the grip strength of the aging mice was lower than that of the young mice. After 12 wk, EPA+ showed similar muscle mass but increased grip strength compared with EPA-. EPA+ displayed higher insulin sensitivity than EPA-. Immunohistochemistry and gene expression analysis of myosin heavy chains (MyHCs) revealed fast-to-slow fiber type transition in aging muscle, which was partially inhibited by EPA. RNA sequencing (RNA-Seq) analysis suggested that EPA supplementation exerts pathway-specific effects in skeletal muscle including the signatures of slow-to-fast fiber type transition. In conclusion, we revealed that aging skeletal muscle in male mice shows lower grip strength and fiber type changes, both of which can be inhibited by EPA supplementation irrespective of muscle mass alteration.NEW & NOTEWORTHY This study demonstrated that the early phenotype of skeletal muscle in aging male mice is characterized by muscle weakness with fast-to-slow fiber type transition, which could be ameliorated by feeding with EPA-enriched diet. EPA induced metabolic changes such as an increase in systemic insulin sensitivity and altered muscle transcriptome in the aging mice. These changes may be related to the fiber type transition and influence muscle quality.

Timing of adrenal regression controlled by synergistic interaction between Sf1 SUMOylation and Dax1.

The nuclear receptor steroidogenic factor 1 (Sf1, Nr5a1, Ad4bp) is crucial for formation, development and function of steroidogenic tissues. A fetal adrenal enhancer (FAdE) in the Sf1 gene was previously identified to direct Sf1 expression exclusively in the fetal adrenal cortex and is bound by both Sf1 and Dax1. Here, we have examined the function of Sf1 SUMOylation and its interaction with Dax1 on FAdE function. A diffused prolonged pattern of FAdE expression and delayed regression of the postnatal fetal cortex (X-zone) were detected in both the SUMOylation-deficient-Sf12KR/2KR and Dax1 knockout mouse lines, with FAdE expression/activity retained in the postnatal 20αHSD-positive postnatal X-zone cells. In vitro studies indicated that Sf1 SUMOylation, although not directly influencing DNA binding, actually increased binding of Dax1 to Sf1 to further enhance transcriptional repression of FAdE. Taken together, these studies define a crucial repressor function of Sf1 SUMOylation and Dax1 in the physiological cessation of FAdE-mediated Sf1 expression and the resultant regression of the postnatal fetal cortex (X-zone).

Three populations of adult Leydig cells in mouse testes revealed by a novel mouse HSD3B1-specific rat monoclonal antibody.

Leydig cells play a pivotal function in the synthesis of a male sex steroid, testosterone. The ability of the steroid production is dependent on the expression of the steroidogenic genes, such as HSD3B (3ß-hydroxysteroid dehydrogenase/Δ5- Δ4 isomerase). It has been established that two different types of Leydig cells, fetal Leydig cells (FLCs) and adult Leydig cells (ALCs), are developed in mammalian testes. FLCs and ALCs are characterized by different sets of marker gene expression. In the case of mouse Leydig cells, Hsd3b1 (Hsd3b type 1) is expressed both in FLCs and ALCs whereas Hsd3b6 (Hsd3b type 6) is expressed in ALCs but not in FLCs. However, because the antibodies established so far for HSD3B were unable to distinguish between the HSD3B1 and HSD3B6 isoforms, it remained unclear whether both of them are expressed in every ALC. Therefore, in the present study, we generated a rat monoclonal antibody specific for mouse HSD3B1. Intriguingly, this monoclonal antibody together with an antibody specific for HSD3B6 identified three populations of ALCs based on the expression levels of these HSD3Bs.

Identical NR5A1 Missense Mutations in Two Unrelated 46,XX Individuals with Testicular Tissues.

The role of monogenic mutations in the development of 46,XX testicular/ovotesticular disorders of sex development (DSD) remains speculative. Although mutations in NR5A1 are known to cause 46,XY gonadal dysgenesis and 46,XX ovarian insufficiency, such mutations have not been implicated in testicular development of 46,XX gonads. Here, we identified identical NR5A1 mutations in two unrelated Japanese patients with 46,XX testicular/ovotesticular DSD. The p.Arg92Trp mutation was absent from the clinically normal mothers and from 200 unaffected Japanese individuals. In silico analyses scored p.Arg92Trp as probably pathogenic. In vitro assays demonstrated that compared with wild-type NR5A1, the mutant protein was less sensitive to NR0B1-induced suppression on the SOX9 enhancer element. Other sequence variants found in the patients were unlikely to be associated with the phenotype. The results raise the possibility that specific mutations in NR5A1 underlie testicular development in genetic females.

Role of Ad4-binding protein/steroidogenic factor 1 in regulating NADPH production in adrenocortical Y-1 cells.

Ad4-binding protein/steroidogenic factor 1 (Ad4BP/SF-1), a member of the nuclear receptor superfamily, is expressed in steroidogenic cells and regulates all steroidogenic gene expression. We recently employed mRNA and chromatin immunoprecipitation sequence (ChIP-seq) to demonstrate that Ad4BP/SF-1 directly regulates the expression of nearly all glycolytic genes. The pentose phosphate pathway (PPP) contributes to the production of nicotinamide adenine dinucleotide phosphate (NADPH). Although the expression of PPP genes and intracellular NADPH were decreased by Ad4BP/SF-1 knockdown, these genes were not the direct targets of Ad4BP/SF-1. This study therefore investigates whether Ad4BP/SF-1 directly regulates genes implicated in NADPH production. Examination of previously published data sets of mRNA sequence (mRNA-seq) and ChIP-seq strongly suggested a possibility that other NADPH-producing genes, such as malic enzyme 1 (Me1) and methylenetetrahydrofolate dehydrogenase 2 (Mthfd2), are the direct targets of Ad4BP/SF-1. Reporter gene assays and determination of intracellular NADPH concentration supported the notion that Ad4BP/SF-1 regulates NADPH production by regulating these genes. NADPH is required for macromolecule synthesis of compounds such as steroids, and for detoxification of reactive oxygen species. When synthesizing steroid hormones, steroidogenic cells consume NADPH through enzymatic reactions mediated by steroidogenic P450s. NADPH is also consumed through elimination of reactive oxygen species produced as the byproducts of the P450 reactions. Overall, Ad4BP/SF-1 potentially maintains the intracellular NADPH level through cooperative regulation of genes involved in the biological processes for consumption and supply.

Identification of myelin transcription factor 1 (MyT1) as a subunit of the neural cell type-specific lysine-specific demethylase 1 (LSD1) complex.

Regulation of spatiotemporal gene expression in higher eukaryotic cells is critical for the precise and orderly development of undifferentiated progenitors into committed cell types of the adult. It is well known that dynamic epigenomic regulation (including chromatin remodeling and histone modifications by transcriptional coregulator complexes) is involved in transcriptional regulation. Precisely how these coregulator complexes exert their cell type and developing stage-specific activity is largely unknown. In this study we aimed to isolate the histone demethylase lysine-specific demethylase 1 (LSD1) complex from neural cells by biochemical purification. In so doing, we identified myelin transcription factor 1 (MyT1) as a novel LSD1 complex component. MyT1 is a neural cell-specific zinc finger factor, and it forms a stable multiprotein complex with LSD1 through direct interaction. Target gene analysis using microarray and ChIP assays revealed that the Pten gene was directly regulated by the LSD1-MyT1 complex. Knockdown of either LSD1 or MyT1 derepressed the expression of endogenous target genes and inhibited cell proliferation of a neuroblastoma cell line, Neuro2a. We propose that formation of tissue-specific combinations of coregulator complexes is a critical mechanism for tissue-specific transcriptional regulation.

Heterogeneity in sexual bipotentiality and plasticity of granulosa cells in developing mouse ovaries.

In mammalian sex determination, SRY directly upregulates the expression of SOX9, the master regulatory transcription factor in Sertoli cell differentiation, leading to testis formation. Without SRY action, the bipotential gonadal cells become pre-granulosa cells, which results in ovarian follicle development. When, where and how pre-granulosa cells are determined to differentiate into developing ovaries, however, remains unclear. By monitoring SRY-dependent SOX9 inducibility (SDSI) in an Sry-inducible mouse system, we were able to identify spatiotemporal changes in the sexual bipotentiality/plasticity of ovarian somatic cells throughout life. The early pre-granulosa cells maintain the SDSI until 11.5 d.p.c., after which most pre-granulosa cells rapidly lose this ability by 12.0 d.p.c. Unexpectedly, we found a subpopulation of the pre-granulosa cells near the mesonephric tissue that continuously retains SDSI throughout fetal and early postnatal stages. After birth, these SDSI-positive pre-granulosa cells contribute to the initial round of folliculogenesis by the secondary follicle stage. In experimental sex reversal of 13.5-d.p.c. ovaries grafted into adult male nude mice, the differentiated granulosa cells re-acquire the SDSI before other signs of masculinization. Our data provide direct evidence of an unexpectedly high sexual heterogeneity of granulosa cells in developing mouse ovaries in a stage- and region-specific manner. Discovery of such sexually bipotential granulosa cells provides a novel entry point to the understanding of masculinization in various cases of XX disorders of sexual development in mammalian ovaries.

CXorf6 is a causative gene for hypospadias.

46,XY disorders of sex development (DSD) refer to a wide range of abnormal genitalia, including hypospadias, which affects approximately 0.5% of male newborns. We identified three different nonsense mutations of CXorf6 in individuals with hypospadias and found that its mouse homolog was specifically expressed in fetal Sertoli and Leydig cells around the critical period for sex development. These data imply that CXorf6 is a causative gene for hypospadias.

Development of sexual dimorphism of skeletal muscles through the adrenal cortex, caused by androgen-induced global gene suppression.

The zona fasciculata (zF) in the adrenal cortex contributes to multiple physiological actions through glucocorticoid synthesis. The size, proliferation, and glucocorticoid synthesis characteristics are all female biased, and sexual dimorphism is established by androgen. In this study, transcriptomes were obtained to unveil the sex differentiation mechanism. Interestingly, both the amount of mRNA and the expressions of nearly all genes were higher in females. The expression of Nr5a1, which is essential for steroidogenic cell differentiation, was also female biased. Whole-genome studies demonstrated that NR5A1 regulates nearly all gene expression directly or indirectly. This suggests that androgen-induced global gene suppression is potentially mediated by NR5A1. Using Nr5a1 heterozygous mice, whose adrenal cortex is smaller than the wild type, we demonstrated that the size of skeletal muscles is possibly regulated by glucocorticoid synthesized by zF. Taken together, considering the ubiquitous presence of glucocorticoid receptors, our findings provide a pathway for sex differentiation through glucocorticoid synthesis.

Mutation of ARX causes abnormal development of forebrain and testes in mice and X-linked lissencephaly with abnormal genitalia in humans.

Male embryonic mice with mutations in the X-linked aristaless-related homeobox gene (Arx) developed with small brains due to suppressed proliferation and regional deficiencies in the forebrain. These mice also showed aberrant migration and differentiation of interneurons containing gamma-aminobutyric acid (GABAergic interneurons) in the ganglionic eminence and neocortex as well as abnormal testicular differentiation. These characteristics recapitulate some of the clinical features of X-linked lissencephaly with abnormal genitalia (XLAG) in humans. We found multiple loss-of-function mutations in ARX in individuals affected with XLAG and in some female relatives, and conclude that mutation of ARX causes XLAG. The present report is, to our knowledge, the first to use phenotypic analysis of a knockout mouse to identify a gene associated with an X-linked human brain malformation.

Tmsb10 triggers fetal Leydig differentiation by suppressing the RAS/ERK pathway.

Leydig cells in fetal testes play crucial roles in masculinizing fetuses through androgen production. Gene knockout studies have revealed that growth factors are implicated in fetal Leydig cell (FLC) differentiation, but little is known about the mechanisms regulating this process. We investigate this issue by characterizing FLC progenitor cells using single-cell RNA sequencing. The sequence datasets suggest that thymosin ß10 (Tmsb10) is transiently upregulated in the progenitors. While studying the function of Tmsb10, we reveal that platelet-derived growth factor (PDGF) regulates ciliogenesis through the RAS/ERK and PI3K/AKT pathways, and thereby promotes desert hedgehog (DHH)-dependent FLC differentiation. Tmsb10 expressed in the progenitor cells induces their differentiation into FLCs by suppressing the RAS/ERK pathway. Through characterizing the transiently expressed Tmsb10 in the FLC progenitors, this study unveils the molecular process of FLC differentiation and shows that it is cooperatively induced by DHH and PDGF.

Prostaglandin E2 receptor Ptger4b regulates female-specific peptidergic neurons and female sexual receptivity in medaka.

In vertebrates, female receptivity to male courtship is highly dependent on ovarian secretion of estrogens and prostaglandins. We recently identified female-specific neurons in the medaka (Oryzias latipes) preoptic area that express Npba, a neuropeptide mediating female sexual receptivity, in response to ovarian estrogens. Here we show by transcriptomic analysis that these neurons express a multitude of neuropeptides, in addition to Npba, in an ovarian-dependent manner, and we thus termed them female-specific, sex steroid-responsive peptidergic (FeSP) neurons. Our results further revealed that FeSP neurons express a prostaglandin E2 receptor gene, ptger4b, in an ovarian estrogen-dependent manner. Behavioral and physiological examination of ptger4b-deficient female medaka found that they exhibit increased sexual receptivity while retaining normal ovarian function and that their FeSP neurons have reduced firing activity and impaired neuropeptide release. Collectively, this work provides evidence that prostaglandin E2/Ptger4b signaling mediates the estrogenic regulation of FeSP neuron activity and female sexual receptivity.

Sex differences in metabolic pathways are regulated by Pfkfb3 and Pdk4 expression in rodent muscle.

Skeletal muscles display sexually dimorphic features. Biochemically, glycolysis and fatty acid ß-oxidation occur preferentially in the muscles of males and females, respectively. However, the mechanisms of the selective utilization of these fuels remains elusive. Here, we obtain transcriptomes from quadriceps type IIB fibers of untreated, gonadectomized, and sex steroid-treated mice of both sexes. Analyses of the transcriptomes unveil two genes, Pfkfb3 (phosphofructokinase-2) and Pdk4 (pyruvate dehydrogenase kinase 4), that may function as switches between the two sexually dimorphic metabolic pathways. Interestingly, Pfkfb3 and Pdk4 show male-enriched and estradiol-enhanced expression, respectively. Moreover, the contribution of these genes to sexually dimorphic metabolism is demonstrated by knockdown studies with cultured type IIB muscle fibers. Considering that skeletal muscles as a whole are the largest energy-consuming organs, our results provide insights into energy metabolism in the two sexes, during the estrus cycle in women, and under pathological conditions involving skeletal muscles.

VCAM1-α4ß1 integrin interaction mediates interstitial tissue reconstruction in 3-D re-aggregate culture of dissociated prepubertal mouse testicular cells.

Roles of interstitial tissue in morphogenesis of testicular structures remain less well understood. To analyze the roles of CD34+ cells in the reconstruction of interstitial tissue containing Leydig cells (LCs), and testicular structures, we used 3D-reaggregate culture of dissociated testicular cells from prepubertal mouse. After a week of culture, adult Leydig cells (ALCs) were preferentially incorporated within CD34+ cell-aggregates, but fetal LCs (FLCs) were not. Immunofluorescence studies showed that integrins α4, α9 and ß1, and VCAM1, one of the ligands for integrins α4ß1 and α9ß1, are expressed mainly in CD34+ cells and ALCs, but not in FLCs. Addition of function-blocking antibodies against each integrin and VCAM1 to the culture disturbed the reconstruction of testicular structures. Antibodies against α4 and ß1 integrins and VCAM1 robustly inhibited cell-to-cell adhesion between testicular cells and between CD34+ cells. Cell-adhesion assays indicated that CD34+ cells adhere to VCAM1 through the interaction with α4ß1 integrin. Live cell imaging showed that CD34+ cells adhered around ALC-aggregates. CD34+ cells on the dish moved toward the aggregates, extending filopodia, and entered into them, which was disturbed by VCAM1 antibody. These results indicate that VCAM1-α4ß1 integrin interaction plays pivotal roles in formation of testicular interstitial tissues in vitro and also in vivo.

GC-MS-based metabolic signatures reveal comparative steroidogenic pathways between fetal and adult mouse testes.

BACKGROUND: Previous studies on gonadal steroidogenesis have not compared metabolic pathways between fetal and adult mouse testes to date. OBJECTIVES: To evaluate comparative metabolic signatures of testicular steroids between fetus and adult mice using gas chromatography-mass spectrometry (GC-MS)-based steroid profiling. MATERIALS AND METHODS: GC-MS with molecular-specific scan modes was optimized for selective and sensitive detection of 23 androgens, 7 estrogens, 14 progestogens, and 13 corticoids from mouse testes with a quantification limit of 0.1-5.0 ng/mL and reproducibility (coefficient of variation: 0.3%-19.9%). Based on 26 steroids quantitatively detected in testes, comparative steroid signatures were analyzed for mouse testes of 8 fetuses on embryonic day 16.5 and 8 adults on postnatal days 56-60. RESULTS: In contrast to large amounts of steroids in adult testes (P < .0002), all testicular levels per weight unit of protein were significantly increased in fetal testes (P < .002, except 6ß-hydroxytestosterone of P = .065). Both 11ß-hydroxyandrostenedione and 7α-hydroxytestosterone were only measurable in fetal testes, and metabolic ratios of testosterone to androstenediol and androstenedione were also increased in fetal testes (P < .05 for both). DISCUSSION AND CONCLUSION: Testicular steroid signatures showed that both steroidogenic Δ4 and Δ5 pathways in the production of testosterone were activated more during prenatal development. Both 7α- and 11ß-hydroxylations were predominant, while hydroxylations at C-6, C-15, and C-16 of testosterone and androstenedione were decreased in the fetus. The present GC-MS-based steroid profiling may facilitate understanding of the development of testicular steroidogenesis.

Gene expression and functional abnormalities in XX/Sry Leydig cells.

The SRY gene induces testis development even in XX individuals. However, XX/Sry testes fail to produce mature sperm, due to the absence of Y chromosome carrying genes essential for spermatogenesis. XX/Sry Sertoli cells show abnormalities in the production of lactate and cholesterol required for germ cell development. Leydig cells are essential for male functions through testosterone production. However, whether XX/Sry adult Leydig cells (XX/Sry ALCs) function normally remains unclear. In this study, the transcriptomes from XY and XX/Sry ALCs demonstrated that immediate early and cholesterogenic gene expressions differed between these cells. Interestingly, cholesterogenic genes were upregulated in XX/Sry ALCs, although downregulated in XX/Sry Sertoli cells. Among the steroidogenic enzymes, CYP17A1 mediates steroid 17α-hydroxylation and 17,20-lyase reaction, necessary for testosterone production. In XX/Sry ALCs, the latter reaction was selectively decreased. The defects in XX/Sry ALCs, together with those in the germ and Sertoli cells, might explain the infertility of XX/Sry testes.

Generation of ovarian follicles from mouse pluripotent stem cells.

Oocytes mature in a specialized fluid-filled sac, the ovarian follicle, which provides signals needed for meiosis and germ cell growth. Methods have been developed to generate functional oocytes from pluripotent stem cell-derived primordial germ cell-like cells (PGCLCs) when placed in culture with embryonic ovarian somatic cells. In this study, we developed culture conditions to recreate the stepwise differentiation process from pluripotent cells to fetal ovarian somatic cell-like cells (FOSLCs). When FOSLCs were aggregated with PGCLCs derived from mouse embryonic stem cells, the PGCLCs entered meiosis to generate functional oocytes capable of fertilization and development to live offspring. Generating functional mouse oocytes in a reconstituted ovarian environment provides a method for in vitro oocyte production and follicle generation for a better understanding of mammalian reproduction.

Coordination of Multiple Cellular Processes by NR5A1/Nr5a1.

The agenesis of the gonads and adrenal gland in revealed by knockout mouse studies strongly suggested a crucial role for Nr5a1 (SF-1 or Ad4BP) in organ development. In relation to these striking phenotypes, NR5A1/Nr5a1 has the potential to reprogram cells to steroidogenic cells, endow pluripotency, and regulate cell proliferation. However, due to limited knowledge regarding NR5A1 target genes, the mechanism by which NR5A1/Nr5a1 regulates these fundamental processes has remained unknown. Recently, newlyestablished technologies have enabled the identification of NR5A1 target genes related to multiple metabolic processes, as well as the aforementioned biological processes. Considering that active cellular processes are expected to be accompanied by active metabolism, NR5A1 may act as a key factor for processes such as cell differentiation, proliferation, and survival by coordinating these processes with cellular metabolism. A complete and definite picture of the cellular processes coordinated by NR5A1/Nr5a1 could be depicted by accumulating evidence of the potential target genes through whole genome studies.

Two-step regulation of Ad4BP/SF-1 gene transcription during fetal adrenal development: initiation by a Hox-Pbx1-Prep1 complex and maintenance via autoregulation by Ad4BP/SF-1.

The orphan nuclear receptor Ad4BP/SF-1 (adrenal 4 binding protein/steroidogenic factor 1) is essential for the proper development and function of reproductive and steroidogenic tissues. Although the expression of Ad4BP/SF-1 is specific for those tissues, the mechanisms underlying this tissue-specific expression remain unknown. In this study, we used transgenic mouse assays to examine the regulation of the tissue-specific expression of Ad4BP/SF-1. An investigation of the entire Ad4BP/SF-1 gene locus revealed a fetal adrenal enhancer (FAdE) in intron 4 containing highly conserved binding sites for Pbx-Prep, Pbx-Hox, and Ad4BP/SF-1. Transgenic assays revealed that the Ad4 sites, together with Ad4BP/SF-1, develop an autoregulatory loop and thereby maintain transcription, while the Pbx/Prep and Pbx/Hox sites initiate transcription prior to the establishment of the autoregulatory loop. Indeed, a limited number of Hox family members were found to be expressed in the adrenal primordia. Whether a true fetal-type adrenal cortex is present in mice remained controversial, and this argument was complicated by the postnatal development of the so-called X zone. Using transgenic mice with lacZ driven by the FAdE, we clearly identified a fetal adrenal cortex in mice, and the X zone is the fetal adrenal cells accumulated at the juxtamedullary region after birth.

Pituitary homeobox 2 regulates adrenal4 binding protein/steroidogenic factor-1 gene transcription in the pituitary gonadotrope through interaction with the intronic enhancer.

Ad4BP/SF-1 [adrenal4 binding protein/steroidogenic factor-1 (NR5A1)] is a factor important for animal reproduction and endocrine regulation, and its expression is tightly regulated in the gonad, adrenal gland, ventromedial hypothalamic nucleus, and pituitary gonadotrope. Despite its functional significance in the pituitary, the mechanisms underlying pituitary-specific expression of the gene remain to be uncovered. In this study, we demonstrate by transgenic mouse assays that the pituitary gonadotrope-specific enhancer is localized within the sixth intron of the gene. Functionally, the enhancer recapitulates endogenous Ad4BP/SF-1 expression in the fetal Rathke's pouch to the adult pituitary gonadotrope. Structurally, the enhancer consists of several elements conserved among animal species. Mutational analyses confirmed the significance of these elements for the enhancer function. One of these elements was able to interact both in vitro and in vivo with Pitx2 (pituitary homeobox 2), demonstrating that pituitary homeobox 2 regulates Ad4BP/SF-1 gene transcription in the pituitary gonadotrope via interaction with the gonadotrope-specific enhancer.