Fox tales: regulation of gonadotropin gene expression by forkhead transcription factors

Cross-species regulatory network analysis identifies FOXO1 as a driver of ovarian follicular recruitment

The transcriptional regulation of gene expression in the latter stages of follicular development in laying hen ovarian follicles is not well understood. Although differentially expressed genes (DEGs) have been identified in pre-recruitment and pre-ovulatory stages, the master regulators driving these DEGs remain unknown. This study addresses this knowledge gap by utilizing Master Regulator Analysis (MRA) combined with the Algorithm for the Reconstruction of Accurate Cellular Networks (ARACNe) for the first time in laying hen research to identify master regulators that are controlling DEGs in pre-recruitment and pre-ovulatory phases. The constructed ARACNe network included 10,466 nodes and 292,391 edges. The ARACNe network was then used in conjunction with the Virtual Inference of Protein-activity by Enriched Regulon (VIPER) for the MRA to identify top up- and down-regulated master regulators. VIPER analysis revealed FOXO1 as a master regulator, influencing 275 DEGs and impacting pathways related to apoptosis, proliferation, and hormonal regulation. Additionally, CLOCK, known as a crucial regulator of circadian rhythm, emerged as an upregulated master regulator in the pre-ovulatory stage. These findings provide new insights into the transcriptional landscape of laying hen ovarian follicles, offering a foundation for further exploration of follicle development and enhancing reproductive efficiency in avian species.

NEK2 promotes the development of ovarian endometriosis and impairs decidualization by phosphorylating FOXO1

Ovarian endometriosis is a common gynecological disease, and one of its most significant symptoms is infertility. In patients with endometriosis, defects in endometrial decidualization lead to impaired endometrial receptivity and embryo implantation, thus affecting early pregnancy and women's desire to have children. However, the mechanisms underlying the development of endometriosis and its associated defective decidualization are unclear. We find that NEK2 expression is increased in the ectopic and eutopic endometrium of patients with endometriosis. Meanwhile, NEK2 interacts with FOXO1 and phosphorylates FOXO1 at Ser184, inhibiting the stability of the FOXO1 protein. Importantly, NEK2-mediated phosphorylation of FOXO1 at Ser184 promotes cell proliferation, migration, invasion and impairs decidualization. Furthermore, INH1, an inhibitor of NEK2, inhibits the growth of ectopic lesions in mouse models of endometriosis and promotes endometrial decidualization in mouse models of artificially induced decidualization. Taken together, these findings indicate that NEK2 regulates the development of endometriosis and associated disorders of decidualization through the phosphorylation of FOXO1, providing a new therapeutic target for its treatment.

EGF-driven EGFR/miR-27b-3p/FOXO1 promotes rat FSH synthesis and secretion

The adenopituitary secretes follicle-stimulating hormone (FSH), which plays a crucial role in regulating the growth, development, and reproductive functions of organisms. Investigating the process of FSH synthesis and secretion can offer valuable insights into potential areas of focus for reproductive research. Epidermal growth factor (EGF) is a significant paracrine/autocrine factor within the body, and studies have demonstrated its ability to stimulate FSH secretion in animals. However, the precise mechanisms that regulate this action are still poorly understood. In this research, in vivo and in vitro experiments showed that the activation of epidermal growth factor receptor (EGFR) by EGF induces the upregulation of miR-27b-3p and that miR-27b-3p targets and inhibits Foxo1 mRNA expression, resulting in increased FSH synthesis and secretion. In summary, this study elucidates the precise molecular mechanism through which EGF governs the synthesis and secretion of FSH via the EGFR/miR-27b-3p/FOXO1 pathway.

Acne Transcriptomics: Fundamentals of Acne Pathogenesis and Isotretinoin Treatment

This review on acne transcriptomics allows for deeper insights into the pathogenesis of acne and isotretinoin's mode of action. Puberty-induced insulin-like growth factor 1 (IGF-1), insulin and androgen signaling activate the kinase AKT and mechanistic target of rapamycin complex 1 (mTORC1). A Western diet (hyperglycemic carbohydrates and milk/dairy products) also co-stimulates AKT/mTORC1 signaling. The AKT-mediated phosphorylation of nuclear FoxO1 and FoxO3 results in their extrusion into the cytoplasm, a critical switch which enhances the transactivation of lipogenic and proinflammatory transcription factors, including androgen receptor (AR), sterol regulatory element-binding transcription factor 1 (SREBF1), peroxisome proliferator-activated receptor γ (PPARγ) and signal transducer and activator of transcription 3 (STAT3), but reduces the FoxO1-dependent expression of GATA binding protein 6 (GATA6), the key transcription factor for infundibular keratinocyte homeostasis. The AKT-mediated phosphorylation of the p53-binding protein MDM2 promotes the degradation of p53. In contrast, isotretinoin enhances the expression of p53, FoxO1 and FoxO3 in the sebaceous glands of acne patients. The overexpression of these proapoptotic transcription factors explains isotretinoin's desirable sebum-suppressive effect via the induction of sebocyte apoptosis and the depletion of BLIMP1(+) sebocyte progenitor cells; it also explains its adverse effects, including teratogenicity (neural crest cell apoptosis), a reduced ovarian reserve (granulosa cell apoptosis), the risk of depression (the apoptosis of hypothalamic neurons), VLDL hyperlipidemia, intracranial hypertension and dry skin.

Dissecting multifunctional roles of forkhead box transcription factor D1 in cancers

As a member of the forkhead box (FOX) family of transcription factors (TF), FOXD1 has recently been implicated as a crucial regulator in a variety of human cancers. Accumulating evidence has established dysregulated and aberrant FOXD1 signaling as a prominent feature in cancer development and progression. However, there is a lack of systematic review on this topic. Here, we summarized the present understanding of FOXD1 functions in cancer biology and reviewed the downstream targets and upstream regulatory mechanisms of FOXD1 as well as the related signaling pathways within the context of current reports. We highlighted the functional features of FOXD1 in cancers to identify the future research consideration of this multifunctional transcription factor and potential therapeutic strategies targeting its oncogenic activity.

The impact of isotretinoin on the pituitary-ovarian axis: An interpretative review of the literature

Isotretinoin (13-cis-retinoic acid), a derivative of vitamin A, is used in the treatment of severe acne resulting in sebum suppression induced by sebocyte apoptosis. Isotretinoin treatment is associated with several adverse effects including teratogenicity, hepatotoxicity, and dyslipidemia. Isotretinoin's effects on endocrine systems and its potential role as an endocrine disruptor are not yet adequately investigated. This review presents clinical, endocrine, and molecular evidence showing that isotretinoin treatment adversely affects the pituitary-ovarian axis and enhances the risk of granulosa cell apoptosis reducing follicular reserve. Isotretinoin is associated with pro-apoptotic signaling in sebaceous glands through upregulated expression of p53, forkhead box O transcription factors (FOXO1, FOXO3), and tumor necrosis factor-related apoptosis inducing ligand (TRAIL). Two literature searches including clinical and experimental studies respectively support the hypothesis that isotretinoin's toxicological mode of action on the pituitary-ovarian axis might be caused by over-expressed p53/FOXO1 signaling resulting in gonadotropin suppression and granulosa cell apoptosis. The reduction of follicular reserve by isotretinoin treatment should be especially considered when this drug will be administered for the treatment of acne in post-adolescent women, in whom fertility may be adversely affected. In contrast, isotretinoin treatment may exert beneficial effects in states of hyperandrogenism, especially in patients with polycystic ovary syndrome.

Development of the Pituitary Gland

The development of the anterior pituitary gland occurs in distinct sequential developmental steps, leading to the formation of a complex organ containing five different cell types secreting six different hormones. During this process, the temporal and spatial expression of a cascade of signaling molecules and transcription factors plays a crucial role in organ commitment, cell proliferation, patterning, and terminal differentiation. The morphogenesis of the gland and the emergence of distinct cell types from a common primordium are governed by complex regulatory networks involving transcription factors and signaling molecules that may be either intrinsic to the developing pituitary or extrinsic, originating from the ventral diencephalon, the oral ectoderm, and the surrounding mesenchyme. Endocrine cells of the pituitary gland are organized into structural and functional networks that contribute to the coordinated response of endocrine cells to stimuli; these cellular networks are formed during embryonic development and are maintained or may be modified in adulthood, contributing to the plasticity of the gland. Abnormalities in any of the steps of pituitary development may lead to congenital hypopituitarism that includes a spectrum of disorders from isolated to combined hormone deficiencies including syndromic disorders such as septo-optic dysplasia. Over the past decade, the acceleration of next-generation sequencing has allowed for rapid analysis of the patient genome to identify novel mutations and novel candidate genes associated with hypothalmo-pituitary development. Subsequent functional analysis using patient fibroblast cells, and the generation of stem cells derived from patient cells, is fast replacing the need for animal models while providing a more physiologically relevant characterization of novel mutations. Furthermore, CRISPR-Cas9 as the method for gene editing is replacing previous laborious and time-consuming gene editing methods that were commonly used, thus yielding knockout cell lines in a fraction of the time. © 2020 American Physiological Society. Compr Physiol 10:389-413, 2020.

Identification and expression of forkhead box genes in the Chinese giant salamander Andrias davidianus

In the present study, 21 forkhead box (Fox) genes were identified in Andrias davidianus, including 13 full-length genes and eight partial sequences. Phylogenetic analysis showed that most were conserved in other investigated amphibians, whereas the Foxk1 gene was found exclusively in A. davidianus. Molecular evolution analysis indicated that most Fox genes underwent purifying selection, whereas two sites of the adFoxp4 gene showed positive selection and were located on the adFoxp4 protein surface. Expression profiles of all Fox genes identified were analysed in the hypothalamic-pituitary-gonad axis by reverse transcription-quantitative polymerase chain reaction. Eighteen genes exhibited sexually dimorphic expression (15 ovary-biased and three testis-biased genes), whereas two genes showed no difference between ovary and testis. Further investigation of 12 selected sexually dimorphic Fox genes showed changes in the expression profile of 11 genes in the ovary of larvae reared at high temperatures (28°C). The results of the present study provide information on Fox genes in an amphibian and suggest that they play key roles in sexual development and reproduction in A. davidianus.

The Sertoli cell marker FOXD1 regulates testis development and function in the chicken

FOXD1, one of the transcription factors of the FOX family, has been shown to be important for mammalian reproduction but little is known about its function in avian species. In the present study, we identified the expression pattern and location of FOXD1 in chicken tissues and testis by performing quantitative polymerase chain reaction, immunohistochemistry and immunofluorescence, and further investigated the regulatory relationship of FOXD1 with genes involved in testis development by RNA interference. Our results showed that FOXD1 is confirmed to be significantly male-biased expressed in the brain, kidney and testis of adults as well as in embryonic gonads, and it is localised in the testicular Sertoli cell in chicken, consistent with its localisation in mammals. After knock-down of FOXD1 in chicken Sertoli cells, the expression of anti-Müllerian hormone (AMH), sex-determining region Y-box 9 (SOX9) and PKA regulatory subunits type I α (RIα) was significantly downregulated, expression of androgen receptor (AR) was notably increased whereas double-sex and MAB-3-related transcription factor 1 (DMRT1) showed no obvious change in expression. These results suggest that FOXD1 is an essential marker for Sertoli cells upstream of SOX9 expression and a potential regulator of embryonic testis differentiation and development and of normal testis function in the chicken.

Gain-of-Function Genetic Models to Study FSH Action

Follicle-stimulating hormone (FSH) is a pituitary-derived gonadotropin that plays key roles in male and female reproduction. The physiology and biochemistry of FSH have been extensively studied for many years. Beginning in the early 1990s, coincident with advances in the then emerging transgenic animal technology, and continuing till today, several gain-of-function (GOF) models have been developed to understand FSH homeostasis in a physiological context. Our group and others have generated a number of FSH ligand and receptor GOF mouse models. An FSH GOF model when combined with Fshb null mice provides a powerful genetic rescue platform. In this chapter, we discuss different GOF models for FSH synthesis, secretion and action and describe additional novel genetic models that could be developed in the future to further refine the existing models.

Pharmacogenetics of FSH Action in the Male

Male infertility is a major contributor to couple infertility, however in most cases it remains "idiopathic" and putative treatment regimens are lacking. This leads to a scenario in which intra-cytoplasmic spermatozoa injection (ICSI) is widely used in idiopathic male infertility, though the treatment burden is high for the couple and it entails considerable costs and risks. Given the crucial role of the Follicle-stimulating hormone (FSH) for spermatogenesis, FSH has been used empirically to improve semen parameters, but the response to FSH varied strongly among treated infertile men. Single nucleotide polymorphisms (SNPs) within FSH ligand/receptor genes (FSHB/FSHR), significantly influencing reproductive parameters in men, represent promising candidates to serve as pharmacogenetic markers to improve prediction of response to FSH. Consequently, several FSH-based pharmacogenetic studies have been conducted within the last years with unfortunately wide divergence concerning selection criteria, treatment and primary endpoints. In this review we therefore outline the current knowledge on single nucleotide polymorphisms (SNPs) in the FSH and FSH receptor genes and their putative functional effects. We compile and critically assess the previously performed pharmacogenetic studies in the male and propose a putative strategy that might allow identifying patients who could benefit from FSH treatment.

MicroRNAs as regulators and mediators of forkhead box transcription factors function in human cancers

Evidence has shown that microRNAs are widely implicated as indispensable components of tumor suppressive and oncogenic pathways in human cancers. Thus, identification of microRNA targets and their relevant pathways will contribute to the development of microRNA-based therapeutics. The forkhead box transcription factors regulate numerous processes including cell cycle progression, metabolism, metastasis and angiogenesis, thereby facilitating tumor initiation and progression. A complex network of protein and non-coding RNAs mediates the expression and activity of forkhead box transcription factors. In this review, we summarize the current knowledge and concepts concerning the involvement of microRNAs and forkhead box transcription factors and describe the roles of microRNAs-forkhead box axis in various disease states including tumor initiation and progression. Additionally, we describe some of the technical challenges in the use of the microRNA-forkhead box signaling pathway in cancer treatment.

Conservation of Repeats at the Mammalian KCNQ1OT1-CDKN1C Region Suggests a Role in Genomic Imprinting

KCNQ1OT1 is located in the region with the highest number of genes showing genomic imprinting, but the mechanisms controlling the genes under its influence have not been fully elucidated. Therefore, we conducted a comparative analysis of the KCNQ1/KCNQ1OT1-CDKN1C region to study its conservation across the best assembled eutherian mammalian genomes sequenced to date and analyzed potential elements that may be implicated in the control of genomic imprinting in this region. The genomic features in these regions from human, mouse, cattle, and dog show a higher number of genes and CpG islands (detected using cpgplot from EMBOSS), but lower number of repetitive elements (including short interspersed nuclear elements and long interspersed nuclear elements), compared with their whole chromosomes (detected by RepeatMasker). The KCNQ1OT1-CDKN1C region contains the highest number of conserved noncoding sequences (CNS) among mammals, where we found 16 regions containing about 38 different highly conserved repetitive elements (using mVista), such as LINE1 elements: L1M4, L1MB7, HAL1, L1M4a, L1Med, and an LTR element: MLT1H. From these elements, we found 74 CNS showing high sequence identity (>70%) between human, cattle, and mouse, from which we identified 13 motifs (using Multiple Em for Motif Elicitation/Motif Alignment and Search Tool) with a significant probability of occurrence, 3 of which were the most frequent and were used to find transcription factor-binding sites. We detected several transcription factors (using JASPAR suite) from the families SOX, FOX, and GATA. A phylogenetic analysis of these CNS from human, marmoset, mouse, rat, cattle, dog, horse, and elephant shows branches with high levels of support and very similar phylogenetic relationships among these groups, confirming previous reports. Our results suggest that functional DNA elements identified by comparative genomics in a region densely populated with imprinted mammalian genes may be related to the regulation of imprinted gene expression.

FOXD1-ALDH1A3 Signaling Is a Determinant for the Self-Renewal and Tumorigenicity of Mesenchymal Glioma Stem Cells

Glioma stem-like cells (GSC) with tumor-initiating activity orchestrate the cellular hierarchy in glioblastoma and engender therapeutic resistance. Recent work has divided GSC into two subtypes with a mesenchymal (MES) GSC population as the more malignant subtype. In this study, we identify the FOXD1-ALDH1A3 signaling axis as a determinant of the MES GSC phenotype. The transcription factor FOXD1 is expressed predominantly in patient-derived cultures enriched with MES, but not with the proneural GSC subtype. shRNA-mediated attenuation of FOXD1 in MES GSC ablates their clonogenicity in vitro and in vivo Mechanistically, FOXD1 regulates the transcriptional activity of ALDH1A3, an established functional marker for MES GSC. Indeed, the functional roles of FOXD1 and ALDH1A3 are likely evolutionally conserved, insofar as RNAi-mediated attenuation of their orthologous genes in Drosophila blocks formation of brain tumors engineered in that species. In clinical specimens of high-grade glioma, the levels of expression of both FOXD1 and ALDH1A3 are inversely correlated with patient prognosis. Finally, a novel small-molecule inhibitor of ALDH we developed, termed GA11, displays potent in vivo efficacy when administered systemically in a murine GSC-derived xenograft model of glioblastoma. Collectively, our findings define a FOXD1-ALDH1A3 pathway in controling the clonogenic and tumorigenic potential of MES GSC in glioblastoma tumors. Cancer Res; 76(24); 7219-30. ©2016 AACR.

FOXL2 Is an Essential Activator of SF-1-Induced Transcriptional Regulation of Anti-Müllerian Hormone in Human Granulosa Cells

Anti-Müllerian hormone (AMH) is required for proper sexual differentiation by regulating the regression of the Müllerian ducts in males. Recent studies indicate that AMH could be an important factor for maintaining the ovarian reserve. However, the mechanisms of AMH regulation in the ovary are largely unknown. Here, we provide evidence that AMH is an ovarian target gene of steroidogenic factor-1 (SF-1), an orphan nuclear receptor required for proper follicle development. FOXL2 is an evolutionally conserved transcription factor, and its mutations cause blepharophimosis, ptosis, and epicanthus inversus syndrome (BPES), wherein affected females display eyelid defects and premature ovarian failure (POF). Notably, we found that functional FOXL2 is essential for SF-1-induced AMH regulation, via protein–protein interactions between FOXL2 and SF-1. A BPES-inducing mutant of FOXL2 (290–291delCA) was unable to interact with SF-1 and failed to mediate the association between SF-1 and the AMH promoter. Therefore, this study identified a novel regulatory circuit for ovarian AMH production; specifically, through the coordinated interplay between FOXL2 and SF-1 that could control ovarian follicle development.

Molecular cloning, computational analysis and expression pattern of forkhead box l2 (Foxl2) gene in catfish

Foxl2 belongs to forkhead/HNF-3-related family of transcription factors which is involved in ovarian differentiation and development. In present study, the Foxl2 mRNA was cloned from ovary of C. batrachus. The full length cDNA sequence of the Foxl2 was 1056bp which consists of 5' (41bp) and 3' (106bp) non-coding regions, as well as a 909bp of open reading frame (ORF) that encodes 302 amino acids. The putative protein was having the theoretical molecular weight (MW) of 34.018kD and a calculated isoelectric point (pI) of 9.38. There were 11 serine (Ser), 5 threonine (Thr), and 5 tyrosine (Tyr) phosphorylation sites and 2 putative N-glycosylation sites on the predicted protein. The ligand binding sites were predicted to be present on amino acids 42, 49, 50, 91, 92 and 95 respectively. The signal peptide analysis predicted that C. batrachus Foxl2 is a non-secretory protein. The hydropathy profile of Foxl2 protein revealed that this protein is hydrophilic in nature. Protein-protein interaction demonstrated that Foxl2 protein chiefly interacts with cytochrome P450 protein family. The mRNA transcript analysis of various tissues indicated that the C. batrachus Foxl2 mRNA was more expressed in the brain, pituitary and ovary in female while, the former two tissues and testis showed low expression in male. This study provides a basis for further structural and functional exploration of the Foxl2 from C. batrachus, including its deduced protein and its signal transduction function.

Genomic structure and promoter functional analysis of GnRH3 gene in large yellow croaker (Larimichthys crocea)

Gonadotropin-releasing hormone III (GnRH3) is considered to be a key neurohormone in fish reproduction control. In the present study, the cDNA and genomic sequences of GnRH3 were cloned and characterized from large yellow croaker Larimichthys crocea. The cDNA encoded a protein of 99 amino acids with four functional motifs. The full-length genome sequence was composed of 3797 nucleotides, including four exons and three introns. Higher identities of amino acid sequences and conserved exon-intron organizations were found between LcGnRH3 and other GnRH3 genes. In addition, some special features of the sequences were detected in partial species. For example, two specific residues (V and A) were found in the family Sciaenidae, and the unique 75-72 bp type of the open reading frame 2 and 3 existed in the family Cyprinidae. Analysis of the 2576 bp promoter fragment of LcGnRH3 showed a number of transcription factor binding sites, such as AP1, CREB, GATA-1, HSF, FOXA2, and FOXL1. Promoter functional analysis using an EGFP reporter fusion in zebrafish larvae presented positive signals in the brain, including the olfactory region, the terminal nerve ganglion, the telencephalon, and the hypothalamus. The expression pattern was generally consistent with the endogenous GnRH3 GFP-expressing transgenic zebrafish lines, but the details were different. These results indicate that the structure and function of LcGnRH3 are generally similar to the other teleost GnRH3 genes, but there exist some distinctions among them.

Linking diet to acne metabolomics, inflammation, and comedogenesis: an update

Acne vulgaris, an epidemic inflammatory skin disease of adolescence, is closely related to Western diet. Three major food classes that promote acne are: 1) hyperglycemic carbohydrates, 2) milk and dairy products, 3) saturated fats including trans-fats and deficient ω-3 polyunsaturated fatty acids (PUFAs). Diet-induced insulin/insulin-like growth factor (IGF-1)-signaling is superimposed on elevated IGF-1 levels during puberty, thereby unmasking the impact of aberrant nutrigenomics on sebaceous gland homeostasis. Western diet provides abundant branched-chain amino acids (BCAAs), glutamine, and palmitic acid. Insulin and IGF-1 suppress the activity of the metabolic transcription factor forkhead box O1 (FoxO1). Insulin, IGF-1, BCAAs, glutamine, and palmitate activate the nutrient-sensitive kinase mechanistic target of rapamycin complex 1 (mTORC1), the key regulator of anabolism and lipogenesis. FoxO1 is a negative coregulator of androgen receptor, peroxisome proliferator-activated receptor-γ (PPARγ), liver X receptor-α, and sterol response element binding protein-1c (SREBP-1c), crucial transcription factors of sebaceous lipogenesis. mTORC1 stimulates the expression of PPARγ and SREBP-1c, promoting sebum production. SREBP-1c upregulates stearoyl-CoA- and Δ6-desaturase, enhancing the proportion of monounsaturated fatty acids in sebum triglycerides. Diet-mediated aberrations in sebum quantity (hyperseborrhea) and composition (dysseborrhea) promote Propionibacterium acnes overgrowth and biofilm formation with overexpression of the virulence factor triglyceride lipase increasing follicular levels of free palmitate and oleate. Free palmitate functions as a "danger signal," stimulating toll-like receptor-2-mediated inflammasome activation with interleukin-1β release, Th17 differentiation, and interleukin-17-mediated keratinocyte proliferation. Oleate stimulates P. acnes adhesion, keratinocyte proliferation, and comedogenesis via interleukin-1α release. Thus, diet-induced metabolomic alterations promote the visible sebofollicular inflammasomopathy acne vulgaris. Nutrition therapy of acne has to increase FoxO1 and to attenuate mTORC1/SREBP-1c signaling. Patients should balance total calorie uptake and restrict refined carbohydrates, milk, dairy protein supplements, saturated fats, and trans-fats. A paleolithic-like diet enriched in vegetables and fish is recommended. Plant-derived mTORC1 inhibitors and ω-3-PUFAs are promising dietary supplements supporting nutrition therapy of acne vulgaris.

FOXO1 is regulated by insulin and IGF1 in pituitary gonadotropes

The FOXO1 transcription factor is important for multiple aspects of reproductive function. We previously reported that FOXO1 functions as a repressor of gonadotropin hormone synthesis, but how FOXO1 is regulated in pituitary gonadotropes is unknown. The growth factors, insulin and insulin-like growth factor I (IGF1), function as key regulators of cell proliferation, metabolism and apoptosis in multiple cell types through the PI3K/AKT signaling pathway. In this study, we found that insulin and IGF1 signaling in gonadotropes induced FOXO1 phosphorylation through the PI3K/AKT pathway in immortalized and primary cells, resulting in FOXO1 relocation from the nucleus to the cytoplasm. Furthermore, insulin administration in vivo induced phosphorylation of FOXO1 and AKT in the pituitary. Thus, insulin and IGF1 act as negative regulators of FOXO1 activity and may serve to fine-tune gonadotropin expression.

Combining RNA and protein profiling data with network interactions identifies genes associated with spermatogenesis in mouse and human

Genome-wide RNA profiling studies have identified hundreds of transcripts that are highly expressed in mammalian male germ cells, including many that are undetectable in somatic control tissues. Among them, genes important for spermatogenesis are significantly enriched. Information about mRNAs and their cognate proteins facilitates the identification of novel conserved target genes for functional studies in the mouse. By inspecting genome-wide RNA profiling data, we manually selected 81 genes for which RNA is detected almost exclusively in the human male germline and, in most cases, in rodent testicular germ cells. We observed corresponding mRNA/protein patterns in 43 cases using immunohistochemical data from the Human Protein Atlas and large-scale human protein profiling data obtained via mass spectroscopy. Protein network information enabled us to establish an interaction map of 38 proteins that points to potentially important testicular roles for some of them. We further characterized six candidate genes at the protein level in the mouse. We conclude that conserved genes induced in testis tend to show similar mRNA/protein expression patterns across species. Specifically, our results suggest roles during embryogenesis and adult spermatogenesis for Foxr1 and Sox30 and during spermiogenesis and fertility for Fam71b, 1700019N19Rik, Hmgb4, and Zfp597.

β-catenin stabilization in gonadotropes impairs FSH synthesis in male mice in vivo

Although classically considered a WNT signaling intermediary, β-catenin (CTNNB1) can also mediate GnRH induction of gonadotropin β-subunit (Fshb and Lhb) transcription in the murine gonadotrope-like cell line LβT2. Here, we assessed CTNNB1's role in gonadotropin synthesis in vivo. We used a Cre/lox approach to introduce both gain- and loss-of-function mutations in the murine Ctnnb1 gene in gonadotrope cells. Gonadotropin production and fertility were normal in Ctnnb1 knockout mice. Similarly, females harboring a deletion of exon 3 of Ctnnb1, which stabilizes the resulting CTNNB1 protein, showed normal fertility and gonadotropin synthesis. Interestingly, males with the activating CTNNB1-Δexon 3 mutation exhibited 50% reductions in FSH synthesis and secretion, without a corresponding change in LH. This selective regulation of FSH suggested an alteration in the activin/inhibin/follistatin system. Indeed, CTNNB1-Δexon 3 males showed a 60% increase in serum inhibin B levels, and in culture, their pituitaries exhibited a greater sensitivity to exogenous inhibin than controls. At the same time, pituitary, but not testicular, follistatin (Fst) expression was increased significantly in these mice. Castration normalized FSH levels in CTNNB1-Δexon 3 males to those seen in castrated controls. Paradoxically, pituitaries from CTNNB1-Δexon 3 males exhibited greater basal and activin-stimulated FSH synthesis in vitro. Similarly, CTNNB1-Δexon 3 overexpression potentiated activin A-induced murine Fshb promoter activity in LβT2 cells. Together, these results indicate that CTNNB1 is dispensable for gonadotropin synthesis in vivo. However, sustained CTNNB1 signaling potentiates activin-induced Fshb expression in gonadotropes, but this effect is overcome in vivo by enhanced inhibin feedback sensitivity and Fst expression.

Kisspeptin cell-specific PI3K signaling regulates hypothalamic kisspeptin expression and participates in the regulation of female fertility

Hypothalamic kisspeptin neurons integrate and translate cues from the internal and external environments that regulate gonadotropin-releasing hormone (GnRH) secretion and maintain fertility in mammals. However, the intracellular signaling pathways utilized to translate such information into changes in kisspeptin expression, release, and ultimately activation of the kisspeptin-receptive GnRH network have not yet been identified. PI3K is an important signaling node common to many peripheral factors known to regulate kisspeptin expression and GnRH release. We investigated whether PI3K signaling regulates hypothalamic kisspeptin expression, pubertal development, and adult fertility in mice. We generated mice with a kisspeptin cell-specific deletion of the PI3K catalytic subunits p110α and p110β (kiss-p110α/β-KO). Using in situ hybridization, we examined Kiss1 mRNA expression in gonad-intact, gonadectomized (Gdx), and Gdx + steroid-replaced mice. Kiss1 cell number in the anteroventral periventricular hypothalamus (AVPV) was significantly reduced in intact females but not in males. In contrast, compared with WT and regardless of steroid hormone status, Kiss1 cell number was lower in the arcuate (ARC) of kiss-p110α/β-KO males, but it was unaffected in females. Both intact Kiss-p110α/β-KO males and females had reduced ARC kisspeptin-immunoreactive (IR) fibers compared with WT animals. Adult kiss-p110α/β-KO males had significantly lower circulating luteinizing hormone (LH) levels, whereas pubertal development and fertility were unaffected in males. Kiss-p110α/β-KO females exhibited a reduction in fertility despite normal pubertal development, LH levels, and estrous cyclicity. Our data show that PI3K signaling is important for the regulation of hypothalamic kisspeptin expression and contributes to normal fertility in females.

Multi-tissue omics analyses reveal molecular regulatory networks for puberty in composite beef cattle

Puberty is a complex physiological event by which animals mature into an adult capable of sexual reproduction. In order to enhance our understanding of the genes and regulatory pathways and networks involved in puberty, we characterized the transcriptome of five reproductive tissues (i.e. hypothalamus, pituitary gland, ovary, uterus, and endometrium) as well as tissues known to be relevant to growth and metabolism needed to achieve puberty (i.e., longissimus dorsi muscle, adipose, and liver). These tissues were collected from pre- and post-pubertal Brangus heifers (3/8 Brahman; Bos indicus x 5/8 Angus; Bos taurus) derived from a population of cattle used to identify quantitative trait loci associated with fertility traits (i.e., age of first observed corpus luteum (ACL), first service conception (FSC), and heifer pregnancy (HPG)). In order to exploit the power of complementary omics analyses, pre- and post-puberty co-expression gene networks were constructed by combining the results from genome-wide association studies (GWAS), RNA-Seq, and bovine transcription factors. Eight tissues among pre-pubertal and post-pubertal Brangus heifers revealed 1,515 differentially expressed and 943 tissue-specific genes within the 17,832 genes confirmed by RNA-Seq analysis. The hypothalamus experienced the most notable up-regulation of genes via puberty (i.e., 204 out of 275 genes). Combining the results of GWAS and RNA-Seq, we identified 25 loci containing a single nucleotide polymorphism (SNP) associated with ACL, FSC, and (or) HPG. Seventeen of these SNP were within a gene and 13 of the genes were expressed in uterus or endometrium. Multi-tissue omics analyses revealed 2,450 co-expressed genes relative to puberty. The pre-pubertal network had 372,861 connections whereas the post-pubertal network had 328,357 connections. A sub-network from this process revealed key transcriptional regulators (i.e., PITX2, FOXA1, DACH2, PROP1, SIX6, etc.). Results from these multi-tissue omics analyses improve understanding of the number of genes and their complex interactions for puberty in cattle.