Human DENND1A.V2 Drives Cyp17a1 Expression and Androgen Production in Mouse Ovaries and Adrenals

Ovarian-Specific Cyp17A1 Overexpression in Female Mice: A Novel Model of Endogenous Testosterone Excess

Excessive androgen levels can severely affect female health. However, most existing models of androgen excess rely on exogenous androgen administration, which does not fully capture the effect of elevated local ovarian testosterone on reproductive and metabolic functions. Here, we report the development of a novel hyperandrogenic mouse model, Cyp17TM-625, generated by combining CRISPR-Cas9 and a Tet-On doxycycline system to induce Cyp17A1 overexpression in ovarian theca-interstitial cells. As a result, Cyp17TM-625 mice exhibited significantly elevated Cyp17A1 messenger RNA and protein levels, accompanied by increased testosterone concentrations without alterations in basal levels of estradiol, progesterone, luteinizing hormone, or follicle-stimulating hormone. These mice demonstrated subfertility, evident by smaller and fewer litters, prolonged estrous cycles, and an increased number of unhealthy follicles with abnormally shaped oocytes. Despite these marked reproductive changes, body weight and glucose homeostasis remained comparable to Con-625 mice. Notably, withdrawal of doxycycline reversed testosterone overexpression and restored fertility over time. This model recapitulates reproductive dysfunction but not the metabolic disturbances, commonly observed in exogenous androgen models. The Cyp17TM-625 mouse line is a unique model for investigating the effects of local excess androgens on ovarian function. It also serves as a valuable tool for studying fertility restoration following the withdrawal of testosterone.

The Search for the Causes of Common Hyperandrogenism, 1965 to Circa 2015

From 1965 to 2015, immense strides were made into understanding the mechanisms underlying the common androgen excess disorders, premature adrenarche and polycystic ovary syndrome (PCOS). The author reviews the critical discoveries of this era from his perspective investigating these disorders, commencing with his early discoveries of the unique pattern of plasma androgens in premature adrenarche and the elevation of an index of the plasma free testosterone concentration in most hirsute women. The molecular genetic basis, though not the developmental biologic basis, for adrenarche is now known and 11-oxytestosterones shown to be major bioactive adrenal androgens. The evolution of the lines of research into the pathogenesis of PCOS is historically traced: research milestones are cited in the areas of neuroendocrinology, insulin resistance, hyperinsulinism, type 2 diabetes mellitus, folliculogenesis, androgen secretion, obesity, phenotyping, prenatal androgenization, epigenetics, and complex genetics. Large-scale genome-wide association studies led to the 2014 discovery of an unsuspected steroidogenic regulator DENND1A (differentially expressed in normal and neoplastic development). The splice variant DENND1A.V2 is constitutively overexpressed in PCOS theca cells in long-term culture and accounts for their PCOS-like phenotype. The genetics are complex, however: DENND1A intronic variant copy number is related to phenotype severity, and recent data indicate that rare variants in a DENND1A regulatory network and other genes are related to PCOS. Obesity exacerbates PCOS manifestations via insulin resistance and proinflammatory cytokine excess; excess adipose tissue also forms testosterone. Polycystic ovaries in 40 percent of apparently normal women lie on the PCOS functional spectrum. Much remains to be learned.

Genetic and Epigenetic Landscape for Drug Development in Polycystic Ovary Syndrome

The treatment of polycystic ovary syndrome (PCOS) faces challenges as all known treatments are merely symptomatic. The US Food and Drug Administration has not approved any drug specifically for treating PCOS. As the significance of genetics and epigenetics rises in drug development, their pivotal insights have greatly enhanced the efficacy and success of drug target discovery and validation, offering promise for guiding the advancement of PCOS treatments. In this context, we outline the genetic and epigenetic advancement in PCOS, which provide novel insights into the pathogenesis of this complex disease. We also delve into the prospective method for harnessing genetic and epigenetic strategies to identify potential drug targets and ensure target safety. Additionally, we shed light on the preliminary evidence and distinctive challenges associated with gene and epigenetic therapies in the context of PCOS.

Polycystic Ovary Syndrome, Insulin Resistance, and Cardiovascular Disease

PURPOSE OF REVIEW

Polycystic ovary syndrome (PCOS) is a prevalent endocrine disorder in women of reproductive age. It has been associated with metabolic, reproductive, and psychiatric disorders. Despite its association with insulin resistance (IR) and cardiovascular disease (CVD) risk factors, the association between PCOS and CVD outcomes has been conflicting. This review reports the updated evidence between PCOS, insulin resistance, and CVD events.

RECENT FINDINGS

IR is highly prevalent occurring in 50 to 95% of general and obese PCOS women. The etiology of PCOS involves IR and hyperandrogenism, which lead to CVD risk factors, subclinical CVD, and CVD outcomes. Multiple studies including meta-analysis confirmed a strong association between PCOS and CVD events including ischemic heart disease, stroke, atrial fibrillation, and diabetes, particularly among premenopausal women, and these associations were mediated by metabolic abnormalities. PCOS is highly familial and has substantial CVD risk and transgenerational effects regardless of obesity. A personalized approach to the CVD risk assessment and management of symptom manifestations should be conducted according to its phenotypes. Lifestyle modifications and reduction in environmental stressors should be encouraged for CVD prevention among PCOS women.

Body mass index stratified meta-analysis of genome-wide association studies of polycystic ovary syndrome in women of European ancestry

BACKGROUND

Polycystic ovary syndrome (PCOS) is a complex multifactorial disorder with a substantial genetic component. However, the clinical manifestations of PCOS are heterogeneous with notable differences between lean and obese women, implying a different pathophysiology manifesting in differential body mass index (BMI). We performed a meta-analysis of genome-wide association study (GWAS) data from six well-characterised cohorts, using a case-control study design stratified by BMI, aiming to identify genetic variants associated with lean and overweight/obese PCOS subtypes.

RESULTS

The study comprised 254,588 women (5,937 cases and 248,651 controls) from individual studies performed in Australia, Estonia, Finland, the Netherlands and United States of America, and separated according to three BMI stratifications (lean, overweight and obese). Genome-wide association analyses were performed for each stratification within each cohort, with the data for each BMI group meta-analysed using METAL software. Almost half of the total study population (47%, n = 119,584) were of lean BMI (≤ 25 kg/m2). Two genome-wide significant loci were identified for lean PCOS, led by rs12000707 within DENND1A (P = 1.55 × 10-12) and rs2228260 within XBP1 (P = 3.68 × 10-8). One additional locus, LINC02905, was highlighted as significantly associated with lean PCOS through gene-based analyses (P = 1.76 × 10-6). There were no significant loci observed for the overweight or obese sub-strata when analysed separately, however, when these strata were combined, an association signal led by rs569675099 within DENND1A reached genome-wide significance (P = 3.22 × 10-9) and a gene-based association was identified with ERBB4 (P = 1.59 × 10-6). Nineteen of 28 signals identified in previous GWAS, were replicated with consistent allelic effect in the lean stratum. There were less replicated signals in the overweight and obese groups, and only 4 SNPs were replicated in each of the three BMI strata.

CONCLUSIONS

Genetic variation at the XBP1, LINC02905 and ERBB4 loci were associated with PCOS within unique BMI strata, while DENND1A demonstrated associations across multiple strata, providing evidence of both distinct and shared genetic features between lean and overweight/obese PCOS-affected women. This study demonstrated that PCOS-affected women with contrasting body weight are not only phenotypically distinct but also show variation in genetic architecture; lean PCOS women typically display elevated gonadotrophin ratios, lower insulin resistance, higher androgen levels, including adrenal androgens, and more favourable lipid profiles. Overall, these findings add to the growing body of evidence supporting a genetic basis for PCOS as well as differences in genetic patterns relevant to PCOS BMI-subtype.

Evidence of positive selection of genetic variants associated with PCOS

STUDY QUESTION

Was polycystic ovary syndrome (PCOS), which impairs fertility and adheres to the evolutionary paradox, subject to evolutionary selection during ancestral times and did rapidly diminish in prevalence?

SUMMARY ANSWER

This study strengthened the hypothesis that positive selection of genetic variants occurred and may account for the high prevalence of PCOS observed today.

WHAT IS KNOWN ALREADY

PCOS is a complex endocrine disorder characterized by both reproductive and metabolic disturbances. As a heritable disease that impairs fertility, PCOS should diminish rapidly in prevalence; however, it is the most common cause of female subfertility globally. Few scientific genetic studies have attempted to provide evidence for the positive selection of gene variants underlying PCOS.

STUDY DESIGN, SIZE, DURATION

We performed an evolutionary analysis of 2,504 individuals from 14 populations of the 1000 Genomes Project.

PARTICIPANTS/MATERIALS, SETTING, METHODS

We tested the signature of positive selection for 37 single-nucleotide polymorphisms (SNPs) associated with PCOS in previous genome-wide association studies using six parameters of positive selection.

MAIN RESULTS AND THE ROLE OF CHANCE

Analyzing the evolutionary indices together, there was obvious positive selection at the PCOS-related SNPs loci, especially within the original evolution window of humans, demonstrated by significant Tajima's D values. Compared to the genome background, six of the 37 SNPs in or close to five genes (DENN domain-containing protein 1A: DENND1A, chromosome 9 open reading frame 3: AOPEP, aminopeptidase O: THADA, diacylglycerol kinase iota: DGKI, and netrin receptor UNC5C: UNC5C) showed significant evidence of positive selection, among which DENND1A, AOPEP, and THADA represent the set of most established susceptibility genes for PCOS.

LIMITATIONS, REASONS FOR CAUTION

First, only well-documented SNPs were selected from well-designed experiments. Second, it is difficult to determine which hypothesis of PCOS evolution is at play. After considering the most significant functions of these genes, we found that they had a wide variety of functions with no obvious association between them.

WIDER IMPLICATIONS OF THE FINDINGS

Our findings provide additional evidence for the positive evolution of PCOS. Our analyses require confirmation in a larger study with more evolutionary indicators and larger data range. Further research to identify the roles of the DENND1A, AOPEP, THADA, DGKI, and UNC5C genes is also necessary.

STUDY FUNDING/COMPETING INTEREST(S)

This study was supported by the National Key Research and Development Program of China (2021YFC2700400 and 2021YFC2700701), Basic Science Center Program of NSFC (31988101), CAMS Innovation Fund for Medical Sciences (2021-I2M-5-001), National Natural Science Foundation of China (82192874, 31871509, and 82071606), Shandong Provincial Key Research and Development Program (2020ZLYS02), Taishan Scholars Program of Shandong Province (ts20190988), and Fundamental Research Funds of Shandong University. The authors have no conflicts of interest to disclose.

TRIAL REGISTRATION NUMBER

N/A.

Transgenic Mouse Models to Study the Development and Maintenance of the Adrenal Cortex

The cortex of the adrenal gland is organized into concentric zones that produce distinct steroid hormones essential for body homeostasis in mammals. Mechanisms leading to the development, zonation and maintenance of the adrenal cortex are complex and have been studied since the 1800s. However, the advent of genetic manipulation and transgenic mouse models over the past 30 years has revolutionized our understanding of these mechanisms. This review lists and details the distinct Cre recombinase mouse strains available to study the adrenal cortex, and the remarkable progress total and conditional knockout mouse models have enabled us to make in our understanding of the molecular mechanisms regulating the development and maintenance of the adrenal cortex.

Update on Animal Models of Polycystic Ovary Syndrome

Polycystic ovary syndrome (PCOS) is a complex disease affecting up to 15% of women of reproductive age. Women with PCOS suffer from reproductive dysfunctions with excessive androgen secretion and irregular ovulation, leading to reduced fertility and pregnancy complications. The syndrome is associated with a wide range of comorbidities including type 2 diabetes, obesity, and psychiatric disorders. Despite the high prevalence of PCOS, its etiology remains unclear. To understand the pathophysiology of PCOS, how it is inherited, and how to predict PCOS, and prevent and treat women with the syndrome, animal models provide an important approach to answering these fundamental questions. This minireview summarizes recent investigative efforts on PCOS-like rodent models aiming to define underlying mechanisms of the disease and provide guidance in model selection. The focus is on new genetic rodent models, on a naturally occurring rodent model, and provides an update on prenatal and peripubertal exposure models.

The PCOS GWAS Candidate Gene ZNF217 Influences Theca Cell Expression of DENND1A.V2, CYP17A1, and Androgen Production

Polycystic ovary syndrome (PCOS), a common endocrine disorder of women, is characterized by increased ovarian androgen production and anovulatory infertility. Genome-wide association studies (GWAS) have identified more than 20 PCOS candidate loci. One GWAS candidate locus encompasses ZNF217, a zinc finger transcription factor. Immunohistochemical staining of ovarian tissue demonstrated significantly lower staining intensity for ZNF217 protein in PCOS theca interna compared to ovarian tissue from normal ovulatory women. Immunofluorescence staining of normal and PCOS theca cells demonstrated nuclear localization of ZNF217, with lower intensity in PCOS cells. Western blotting showed reduced ZNF217 protein in PCOS theca cells compared to normal theca cells, and that treatment with forskolin, which mimics the action of luteinizing hormone (LH), reduces ZNF217 expression. Lower ZNF217 expression in PCOS theca cells was confirmed by quantitative reverse transcription polymerase chain reaction. Notably, there was an inverse relationship between ZNF217 messenger RNA (mRNA) levels and theca cell androgen (dehydroepiandrosterone; DHEA) synthesis. The abundance of mRNA encoding a splice variant of DENND1A (DENND1A.V2), a PCOS candidate gene that positively regulates androgen biosynthesis, was also inversely related to ZNF217 mRNA levels. This relationship may be driven by increased miR-130b-3p, which targets DENND1A.V2 transcripts and is directly correlated with ZNF217 expression. Forced expression of ZNF217 in PCOS theca cells reduced androgen production, CYP17A1 and DENND1A.V2 mRNA, while increasing mIR-130b-3p. Conversely, knockdown of ZNF217 in normal theca cells with short hairpin RNA-expressing lentivirus particles increased DENND1A.V2 and CYP17A1 mRNA. These observations suggest that ZNF217 is part of a network of PCOS candidate genes regulating thecal cell androgen production involving DENND1A.V2 and miR-130b-3p.

Normal and Premature Adrenarche

Adrenarche is the maturational increase in adrenal androgen production that normally begins in early childhood. It results from changes in the secretory response to adrenocorticotropin (ACTH) that are best indexed by dehydroepiandrosterone sulfate (DHEAS) rise. These changes are related to the development of the zona reticularis (ZR) and its unique gene/enzyme expression pattern of low 3ß-hydroxysteroid dehydrogenase type 2 with high cytochrome b5A, sulfotransferase 2A1, and 17ß-hydroxysteroid dehydrogenase type 5. Recently 11-ketotestosterone was identified as an important bioactive adrenarchal androgen. Birth weight, body growth, obesity, and prolactin are related to ZR development. Adrenarchal androgens normally contribute to the onset of sexual pubic hair (pubarche) and sebaceous and apocrine gland development. Premature adrenarche causes ≥90% of premature pubarche (PP). Its cause is unknown. Affected children have a significantly increased growth rate with proportionate bone age advancement that typically does not compromise growth potential. Serum DHEAS and testosterone levels increase to levels normal for early female puberty. It is associated with mildly increased risks for obesity, insulin resistance, and possibly mood disorder and polycystic ovary syndrome. Between 5% and 10% of PP is due to virilizing disorders, which are usually characterized by more rapid advancement of pubarche and compromise of adult height potential than premature adrenarche. Most cases are due to nonclassic congenital adrenal hyperplasia. Algorithms are presented for the differential diagnosis of PP. This review highlights recent advances in molecular genetic and developmental biologic understanding of ZR development and insights into adrenarche emanating from mass spectrometric steroid assays.

Adrenal androgens, adrenarche, and zona reticularis: A human affair?

In humans, reticularis cells of the adrenal cortex fuel the production of androgen steroids, constituting the driver of numerous morphological changes during childhood. These steps are considered a precocious stage of sexual maturation and are grouped under the term "adrenarche". This review describes the molecular and enzymatic characteristics of the zona reticularis, along with the possible signals and mechanisms that control its emergence and the associated clinical features. We investigate the differences between species and discuss new studies such as genetic lineage tracing and transcriptomic analysis, highlighting the rodent inner cortex's cellular and molecular heterogeneity. The recent development and characterization of mouse models deficient for Prkar1a presenting with adrenocortical reticularis-like features prompt us to review our vision of the mouse adrenal gland maturation. We expect these new insights will help increase our understanding of the adrenarche process and the pathologies associated with its deregulation.

Genetics of Polycystic Ovary Syndrome: What is New?

Polycystic ovary syndrome (PCOS) is a complex genetic disorder with many genetic loci contributing small risk. Large genome-wide association studies identified 21 genetic risk loci for PCOS in European and Han Chinese women. The genetic architecture is similar across PCOS diagnostic categories. The next wave of analysis will incorporate large genotyped datasets linked to medical records, increasing numbers and ethnic subsets. The resulting genetic risk loci can then be used to create robust genetic risk scores enhanced with clinical information, environment and lifestyle data for a precision medicine approach to PCOS diagnosis and treatment.

Mid-Gestation lethality of Atxn2l-Ablated Mice

Depletion of yeast/fly Ataxin-2 rescues TDP-43 overexpression toxicity. In mouse models of Amyotrophic Lateral Sclerosis via TDP-43 overexpression, depletion of its ortholog ATXN2 mitigated motor neuron degeneration and extended lifespan from 25 days to >300 days. There is another ortholog in mammals, named ATXN2L (Ataxin-2-like), which is almost uncharacterized but also functions in RNA surveillance at stress granules. We generated mice with Crispr/Cas9-mediated deletion of Atxn2l exons 5-8, studying homozygotes prenatally and heterozygotes during aging. Our novel findings indicate that ATXN2L absence triggers mid-gestational embryonic lethality, affecting female animals more strongly. Weight and development stages of homozygous mutants were reduced. Placenta phenotypes were not apparent, but brain histology showed lamination defects and apoptosis. Aged heterozygotes showed no locomotor deficits or weight loss over 12 months. Null mutants in vivo displayed compensatory efforts to maximize Atxn2l expression, which were prevented upon nutrient abundance in vitro. Mouse embryonal fibroblast cells revealed more multinucleated giant cells upon ATXN2L deficiency. In addition, in human neural cells, transcript levels of ATXN2L were induced upon starvation and glucose and amino acids exposure, but this induction was partially prevented by serum or low cholesterol administration. Neither ATXN2L depletion triggered dysregulation of ATXN2, nor a converse effect was observed. Overall, this essential role of ATXN2L for embryogenesis raises questions about its role in neurodegenerative diseases and neuroprotective therapies.

Analysis of expression of candidate genes for polycystic ovary syndrome in adult and fetal human and fetal bovine ovaries†

Polycystic ovary syndrome (PCOS) appears to have a genetic predisposition and a fetal origin. We compared the expression levels of 25 PCOS candidate genes from adult control and PCOS human ovaries (n = 16) using microarrays. Only one gene was potentially statistically different. Using qRT-PCR, expression of PCOS candidate genes was examined in bovine fetal ovaries from early stages when they first developed stroma through to completion of development (n = 27; 60-270 days of gestation). The levels of ERBB3 mRNA negatively correlated with gestational age but positively with HMGA2, FBN3, TOX3, GATA4, and DENND1A.X1,2,3,4, previously identified as correlated with each other and expressed early. PLGRKT and ZBTB16, and less so IRF1, were also correlated with AMH, FSHR, AR, INSR, and TGFB1I1, previously identified as correlated with each other and expressed late. ARL14EP, FDFT1, NEIL2, and MAPRE1 were expressed across gestation and not correlated with gestational age as shown previously for THADA, ERBB4, RAD50, C8H9orf3, YAP1, RAB5B, SUOX, and KRR1. LHCGR, because of its unusual bimodal expression pattern, had some unusual correlations with other genes. In human ovaries (n = 15; <150 days of gestation), ERBB3.V1 and ERBB3.VS were expressed and correlated negatively with gestational age and positively with FBN3, HMGA2, DENND1A.V1,3,4, DENND1A.V1-7, GATA4, and FSHR, previously identified as correlated with each other and expressed early. Thus, the general lack of differential expression of candidate genes in adult ovaries contrasting with dynamic patterns of gene expression in fetal ovaries is consistent with a vulnerability to disturbance in the fetal ovary that may underpin development of PCOS.