MKRN3 inhibits puberty onset via interaction with IGF2BP1 and regulation of hypothalamic plasticity

Mom genes and dad genes: genomic imprinting in the regulation of social behaviors

Genomic imprinting is an epigenetic phenomenon in mammals that affects brain development and behavior. Imprinting involves the regulation of allelic expression for some genes in offspring that depends on whether alleles are inherited from mothers compared to fathers, and is thought to provide parental control over offspring social behavior phenotypes. Imprinted gene expression is prevalent in the mammalian brain, and human imprinted gene mutations are associated with neurodevelopmental disorders and neurodivergent social behavior in Prader-Willi Syndrome, Angelman Syndrome, and autism. Here, we provide a review of the evidence that imprinted genes influence social behaviors across major neurodevelopmental stages in humans and mouse animal models that include parent-infant interactions, juvenile sociability, and adult aggression, dominance, and sexual behavior.

A Case of Prader-Willi Syndrome With a Deletion Including MAGEL2, NDN, and MKRN3, but Excluding SNRPN and SNORD116

Prader-Willi syndrome (PWS) is a neurodevelopmental disorder typically caused by large deletions or imprinting defects on chromosome 15q11.2, encompassing multiple genes. While the contribution of individual genes to the PWS phenotype remains unclear, previous studies suggested that isolated deletions of MAGEL2, NDN, and MKRN3, excluding the SNRPN/SNORD116 locus, were insufficient to cause PWS. Here, we present a case report of a patient with an isolated deletion of MAGEL2, NDN, and MKRN3 who exhibits the full PWS phenotype, including neonatal hypotonia, developmental delay, hyperphagia, obesity, and behavioral issues. We explore the potential mechanisms underlying this case and investigate the potential contribution of the deleted genes to the observed phenotype. This case challenges previous findings and highlights the complexity of genotype-phenotype correlations in PWS. We compare the clinical data of our patient with previous reports and discuss the discrepancy with earlier findings. Our findings underscore the need for further research to fully elucidate the roles of individual genes within the PWS locus and the mechanisms underlying the phenotypic spectrum of this complex disorder.

Exploration of the molecular mechanism of modified Danggui Liuhuang Decoction in treating central precocious puberty and its effects on hypothalamic-pituitary-gonadal axis hormones

AIM

To evaluate the molecular mechanism of modified Danggui Liuhuang Decoction (MDGLHD) in treating central precocious puberty (CPP).

METHODS

CPP-related genes were obtained from GEO dataset, MalaCard, DisGeNET and GeneCards databases. MDGLHT ingredients and targets were obtained in TCMSP, HERB, and SwissTargetPrediction databases. Protein-protein interaction (PPI) network was constructed and analyzed using STRING database and Cytoscape 3.9.1. Genetic ontological (GO) analysis and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis were performed with DAVID and Metascape databases. Molecular docking was performed with PyMoL and AutoDock-Vina software. The GnRH secretion model was established by E2 induction of GT1-7 cells. CCK-8, ELISA and qRT-PCR were used to detect the effects of MDGLHD on gonadotropin-releasing hormone (GnRH) secretion and endocrine signaling receptor gene expression.

RESULTS

318 potential targets of MDGLHD in CPP treatment were screened out. Quercetin, kaempferol, and (S)-Canadine were considered to be the most important active ingredients in MDGLHD. Bioinformatics analysis showed that these targets were associated with response to hormone, JAK-STAT signaling pathway and HIF-1 signaling pathway. Quercetin, kaempferol, and (s)-Canadine had good binding affinity with tumor protein p53 (TP53), estrogen receptor 1(ESR1), Jun proto-oncogene (JUN), MYC proto-oncogene (MYC) and AKT serine/threonine kinase 1 (AKT1). In vitro experiments showed that MDGLHD extract can inhibit GnRH secretion and the expression of neuroendocrine signaling receptor protein gene.

CONCLUSION

MDGLHD treatment of CPP is achieved through multi-components, multi-targets and multi-pathways, and inhibition of GnRH secretion and neuroendocrine signaling.

Reduction in minipubertal gonadotropin levels alters reproductive lifespan and ovarian follicular loss in female mice

STUDY QUESTION

What is the effect of attenuating the physiological hypergonadotropic activity encountered at minipuberty on female reproductive function in a mouse model?

SUMMARY ANSWER

Decreasing the surge of gonadotropins at minipuberty extended reproductive lifespan, coinciding with alterations in neuroendocrine and ovarian aging.

WHAT IS KNOWN ALREADY

Minipuberty is characterized by the tremendous activation of the gonadotrope axis, as evidenced by elevated levels of gonadotropins regulating folliculogenesis and the synthesis of ovarian hormones, but its role in fertility remains unclear.

STUDY DESIGN, SIZE, DURATION

To determine the link between gonadotrope axis activity at minipuberty and reproductive parameters, we used a pharmacological approach to suppress gonadotropin levels in Swiss mice by injecting daily a GnRH receptor antagonist (GnRHR) (Ganirelix, 10 µg/mouse) or its vehicle between 10 and 16 postnatal days, to cover the entire duration of minipuberty. We analyzed the onset of puberty and estrous cyclicity as well as fertility in young (3-5 months) and middle-aged (11 months) mice from control (CTR) and antagonist-treated groups (n = 17-20 mice/age and treatment group). Ovaries and brains were collected, fixed, and sectioned (for histology, follicle count, and immunohistochemistry) or frozen (for analysis of follicular markers, aging, and inflammation) from adult females, and blood was collected by cardiac puncture for hormonal assays (n = 3-8 mice/age and treatment group).

PARTICIPANTS/MATERIALS, SETTING, METHODS

To analyze the initiation of puberty, we monitored vaginal opening and performed vaginal smears in CTR and antagonist-treated mice. We studied estrous cyclicity on vaginal smears at the beginning of reproductive life. Mice were mated several times with males to assess fertility rates, delay of conception, and litter size. To evaluate ovarian function, we counted follicles at different stages and corpora lutea, and we determined the relative intra-ovarian abundance of key follicular markers by real-time RT-PCR, as well as the levels of circulating anti-Müllerian hormone (AMH) and progesterone by ELISA and GC-MS, respectively. We also analyzed features of ovarian aging and inflammation by histology and by measuring the relative intra-ovarian abundance of some markers using real-time RT-PCR. To determine the impact on neuroendocrine determinants related to the CTR of reproduction, we analyzed circulating gonadotropin levels using Luminex assays as well as kisspeptin and GnRH immunoreactivity in the hypothalamus by immunohistochemistry.

MAIN RESULTS AND THE ROLE OF CHANCE

Our results show that the treatment had no impact on the initiation of puberty, estrous cyclicity, or fertility at the beginning of reproductive life. However, it increased reproductive lifespan, as shown by the higher percentage of antagonist-treated females than CTRs still fertile at 11 months of age (33% versus 6%; P = 0.0471). There were no significant differences in the number of kisspeptin and GnRH neurons, nor in the density of kisspeptin- and GnRH-immunoreactive neurons in the hypothalamic areas involved in reproduction between the two groups of mice studied at either 4 or 11 months. In addition, basal levels of FSH were comparable between the two groups at 4 and 11 months, but not those of LH at 11 months which were much lower in females treated with antagonist than in their age-matched CTRs (237 ± 59.6 pg/ml in antagonist-treated females versus 1027 ± 226.3 pg/ml in CTRs, P = 0.0069). Importantly, at this age, antagonist-treated mice had basal LH levels comparable to young mice (e.g. in 4-month-old CTRs: 294 ± 71.75 pg/ml, P > 0.05). Despite their prolonged reproductive lifespan and delayed neuroendocrine aging, antagonist-treated mice exhibited earlier depletion of their follicles, as shown by lower numbers of primordial, primary, and preantral follicles associated with lower circulating AMH levels and relative intra-ovarian abundance of Amh transcripts than CTR mice. However, they exhibited comparable completion of folliculogenesis, as suggested by the numbers of antral follicles and corpora lutea, relative intra-ovarian abundance of Cyp19a1, Inhba, and Inhbb transcripts, and circulating progesterone levels that all remained similar to those of the CTR group. These observed alterations in ovarian function were not associated with increased ovarian aging or inflammation.

LARGE-SCALE DATA

None.

LIMITATIONS, REASONS FOR CAUTION

This study was carried out on mice, which is a validated research model. However, human research is needed for further validation.

WIDER IMPLICATIONS OF THE FINDINGS

This study, which is the first to investigate the physiological role of minipuberty on reproductive parameters, supports the idea that suppressing the high postnatal levels of gonadotropins may have long-term effects on female fertility by extending the duration of reproductive life. Perturbations in gonadotropin levels during this period of life, such as those observed in infants born prematurely, may thus have profound consequences on late reproductive functions.

STUDY FUNDING/COMPETING INTEREST(S)

This research was conducted with the financial support of ANR AAPG2020 (ReproFUN), CNRS, Inserm, Université Paris Cité, and Sorbonne Université. The authors declare that they have no conflicts of interest.

Shared Pathophysiological Mechanisms and Genetic Factors in Early Menarche and Polycystic Ovary Syndrome

Early age at menarche (early AAM) and polycystic ovary syndrome (PCOS) are reproductive and metabolic disorders with overlapping pathophysiological and genetic features. Epidemiological studies suggest a link between these two conditions, both of which are characterized by dysregulation of the neuroendocrine pathways that control pulsatile gonadotropin-releasing hormone secretion, thus affecting gonadotropin release, particularly luteinizing hormone secretion. A common pathophysiology involving positive energy balance and abnormal metabolic status is evident in both disorders. Genetic and epigenetic factors influence the onset of puberty and reproductive outcomes. Genome-wide association studies have identified common genetic variants associated with AAM and PCOS, particularly in genes related to the neuroendocrine axis (e.g., FSHB) and obesity (e.g., FTO). In addition, high-throughput sequencing has revealed rare loss-of-function variants in the DLK1 gene in women with central precocious puberty (CPP), early menarche, and PCOS, who experienced adverse metabolic outcomes in adulthood. This review explores the shared pathophysiological mechanisms between CPP/early AAM and PCOS, examines potential genetic and epigenetic factors that may link these neuroendocrine reproductive conditions, and offers insights into future research and treatment strategies. Understanding these connections may provide new targets for therapeutic interventions and improve outcomes for individuals with these reproductive disorders.

A novel model of central precocious puberty disease: Paternal MKRN3 gene-modified rabbit

BACKGROUND

Makorin ring finger protein 3 gene (MKRN3) gene mutation is the most common genetic cause of central precocious puberty (CPP) in children. Due to the lack of ideal MKRN3-modified animal model (MKRN3-modified mice enter puberty only 4-5 days earlier than normal mice), the related research is limited.

METHODS

Therefore, the MKRN3-modified rabbit was developed using CRISPR (clustered regularly interspaced short palindromic repeats) gene editing technology. The genotype identification and phenotype evaluation of MKRN3-modified rabbits were carried out.

RESULTS

The first estrus of MKRN3-modified female rabbits was observed ~27 days earlier than that of wild-type female rabbits, with a typical CPP phenotype. This study found increased gonadotropin releasing hormone (GnRH) and decreased gonadotropin inhibiting hormone (GnIH) in the hypothalamus of the CPP rabbit model with MKRN3 gene mutation. Although this study failed to fully clarify the pathogenesis of CPP caused by MKRN3 mutation, it found some differentially expressed genes and potential pathways through transcriptome sequencing.

CONCLUSIONS

This study established a novel CPP model: paternal MKRN3 gene-modified rabbit. It is hoped that the establishment of this model will help researchers better understand, treat, and prevent CPP in the future.

Genetics and Epigenetics of Human Pubertal Timing: The Contribution of Genes Associated With Central Precocious Puberty

Human puberty is a dynamic biological process determined by the increase in the pulsatile secretion of GnRH triggered by distinct factors not fully understood. Current knowledge reveals fine tuning between an increase in stimulatory factors and a decrease in inhibitory factors, where genetic and epigenetic factors have been indicated as key players in the regulation of puberty onset by distinct lines of evidence. Central precocious puberty (CPP) results from the premature reactivation of pulsatile secretion of GnRH. In the past decade, the identification of genetic causes of CPP has largely expanded, revealing hypothalamic regulatory factors of pubertal timing. Among them, 3 genes associated with CPP are linked to mechanisms involving DNA methylation, reinforcing the strong role of epigenetics underlying this disorder. Loss-of-function mutations in Makorin Ring-Finger Protein 3 (MKRN3) and Delta-Like Non-Canonical Notch Ligand 1 (DLK1), 2 autosomal maternally imprinted genes, have been described as relevant monogenic causes of CPP with the phenotype exclusively associated with paternal transmission. MKRN3 has proven to be a key component of the hypothalamic inhibitory input on GnRH neurons through different mechanisms. Additionally, rare heterozygous variants in the Methyl-CpG-Binding Protein 2 (MECP2), an X-linked gene that is a key factor of DNA methylation machinery, were identified in girls with sporadic CPP with or without neurodevelopmental disorders. In this mini-review, we focus on how the identification of genetic causes of CPP has revealed epigenetic regulators of human pubertal timing, summarizing the latest knowledge on the associations of puberty with MKRN3, DLK1, and MECP2.

NAGK regulates the onset of puberty in female mice

This study examines the role of N-acetylglucosamine kinase (NAGK) in initiating puberty in female mice. We employed real-time quantitative reverse transcription polymerase chain reaction (RT-qPCR) and immunofluorescence to measure NAGK expression in the hypothalamic-pituitary-ovarian axis across various developmental stages: infant, prepuberty, puberty, and adult. We further investigated the impact of Nagk gene knockdown on puberty in female mice. This included assessing the expression of puberty-related genes both in vivo and in vitro, GT1-7 cells proliferation and apoptosis, concentrations of GnRH and Kisspeptin, puberty onset timing, serum levels of progesterone (P4) and estradiol (E2), and ovarian morphology. Results revealed that Nagk mRNA is present in the hypothalamus, pituitary, and ovaries throughout different developmental stages in female mice. In the hypothalamus, Nagk mRNA levels were comparable during infant and prepuberty, lowest during puberty, and highest in adult. In the pituitary, Nagk mRNA peaked in adult, with no significant variation between infant, prepuberty, and puberty. In the ovaries, Nagk mRNA levels increased during puberty and peaked in adult. NAGK is predominantly located in the arcuate nucleus (ARC), periventricular nucleus (PeN), dorsomedial hypothalamic nucleus (DMH), paraventricular nucleus (PVN), adenohypophysis, and in the ovarian oocytes, interstitium, and granulosa cells across all developmental stages in female mice. Nagk knockdown in GT1-7 cells decreased the transcriptional level of Gnrh, Kiss1, Gpr54, Igf1 and Mapk14 mRNA and cell proliferation but increased the level of β-catenin mRNA and cell apoptosis, while reducing GnRH secretion. Following ICV injection, Nagk gene knockdown mice exhibited delayed the timing of vaginal opening (VO) and reduced hypothalamic levels of Gnrh, Kiss1, Gpr54, Igf1, Mapk14, and β-catenin mRNA. Additionally, serum concentrations of E2 in Nagk gene knockdown mice were significantly lower compared to the control group. These findings indicate that Nagk regulates the expression of Gnrh and Kiss1 mRNA in GT1-7 cells, affects hypothalamus Gnrh mRNA levels and serum E2 concentration, and that its knockdown can delay puberty onset in female mice.

Disorders of puberty and neurodevelopment: A shared etiology?

The neuroendocrine control of puberty and reproduction is fascinatingly complex, with up- and down-regulation of key reproductive hormones during fetal, infantile, and later childhood periods that determine the correct function of the hypothalamic-pituitary-gonadal axis and the timing of puberty. Neuronal development is a vital element of these processes, and multiple conditions of disordered puberty and reproduction have their etiology in abnormal neuronal migration or function. Although there are numerous documented cases across multiple conditions wherein patients have both neurodevelopmental disorders and pubertal abnormalities, this has mostly been described ad hoc and the associations are not clearly documented. In this review, we aim to describe the overlap between these two groups of conditions and to increase awareness to ensure that puberty and reproductive function are carefully monitored in patients with neurodevelopmental conditions, and vice versa. Moreover, this commonality can be explored for clues about the disease mechanisms in these patient groups and provide new avenues for therapeutic interventions for affected individuals.

Developmental exposure to environmentally relevant doses of phthalates alters the neural control of male and female reproduction in mice

The present study aims to analyze the effects of developmental exposure to phthalates at environmentally relevant doses on the neural control of male and female reproduction. For this purpose, C57Bl/6J mice were exposed to di-(2-ethylexyl) phthalate (DEHP) alone (5 or 50 μg/kg/d), or DEHP (5 μg/kg/d) in a phthalate mixture. Exposure through diet started 6 weeks before the first mating and lasted until weaning of litters from the second gestation (multiparous dams). Analyses of offspring born from multiparous dams exposed to DEHP alone or in a phthalate mixture showed that females experienced a delayed pubertal onset, and as adults they had prolonged estrous cyclicity and reduced Kiss1 expression in the preoptic area and mediobasal hypothalamus. Male littermates showed a reduced anogenital distance and delayed pubertal onset compared with controls. However, in adulthood the weight of androgen-sensitive organs and hypothalamic Kiss1 expression were unaffected, suggesting normal functioning of the male gonadotropic axis. Developmental exposure to DEHP alone or in a phthalate mixture reduced the ability of intact males and ovariectomized and hormonally primed females to attract a sexual partner and to express copulatory behaviors. In addition, females were unable to discriminate between male and female stimuli in the olfactory preference test. Social interaction was also impaired in females, while locomotor activity and anxiety-like behavior in both sexes were unaffected by the treatment. The sexual deficiencies were associated with reduced expression of the androgen receptor in the preoptic area and progesterone receptor in the mediobasal hypothalamus, the key regions involved in male and female sexual behavior, respectively. Thus, the neural structures controlling reproduction are vulnerable to developmental exposure to phthalates at environmentally relevant doses in male and female mice. Adult females had an impaired gonadotropic axis and showed more affected behaviors than adult males.

Diversity of Molecular Functions of RNA-Binding Ubiquitin Ligases from the MKRN Protein Family

Makorin RING finger protein family includes four members (MKRN1, MKRN2, MKRN3, and MKRN4) that belong to E3 ubiquitin ligases and play a key role in various biological processes, such as cell survival, cell differentiation, and innate and adaptive immunity. MKRN1 contributes to the tumor growth suppression, energy metabolism, anti-pathogen defense, and apoptosis and has a broad variety of targets, including hTERT, APC, FADD, p21, and various viral proteins. MKRN2 regulates cell proliferation, inflammatory response; its targets are p65, PKM2, STAT1, and other proteins. MKRN3 is a master regulator of puberty timing; it controls the levels of gonadotropin-releasing hormone in the arcuate nucleus neurons. MKRN4 is the least studied member of the MKRN protein family, however, it is known to contribute to the T cell activation by ubiquitination of serine/threonine kinase MAP4K3. Proteins of the MKRN family are associated with the development of numerous diseases, for example, systemic lupus erythematosus, central precocious puberty, Prader-Willi syndrome, degenerative lumbar spinal stenosis, inflammation, and cancer. In this review, we discuss the functional roles of all members of the MKRN protein family and their involvement in the development of diseases.

Endocrine features of Prader-Willi syndrome: a narrative review focusing on genotype-phenotype correlation

Prader-Willi syndrome (PWS) is a complex genetic disorder caused by three different types of molecular genetic abnormalities. The most common defect is a deletion on the paternal 15q11-q13 chromosome, which is seen in about 60% of individuals. The next most common abnormality is maternal disomy 15, found in around 35% of cases, and a defect in the imprinting center that controls the activity of certain genes on chromosome 15, seen in 1-3% of cases. Individuals with PWS typically experience issues with the hypothalamic-pituitary axis, leading to excessive hunger (hyperphagia), severe obesity, various endocrine disorders, and intellectual disability. Differences in physical and behavioral characteristics between patients with PWS due to deletion versus those with maternal disomy are discussed in literature. Patients with maternal disomy tend to have more frequent neurodevelopmental problems, such as autistic traits and behavioral issues, and generally have higher IQ levels compared to those with deletion of the critical PWS region. This has led us to review the pertinent literature to investigate the possibility of establishing connections between the genetic abnormalities and the endocrine disorders experienced by PWS patients, in order to develop more targeted diagnostic and treatment protocols. In this review, we will review the current state of clinical studies focusing on endocrine disorders in individuals with PWS patients, with a specific focus on the various genetic causes. We will look at topics such as neonatal anthropometry, thyroid issues, adrenal problems, hypogonadism, bone metabolism abnormalities, metabolic syndrome resulting from severe obesity caused by hyperphagia, deficiencies in the GH/IGF-1 axis, and the corresponding responses to treatment.

Metabolic control of puberty: 60 years in the footsteps of Kennedy and Mitra's seminal work

An individual's nutritional status has a powerful effect on sexual maturation. Puberty onset is delayed in response to chronic energy insufficiency and is advanced under energy abundance. The consequences of altered pubertal timing for human health are profound. Late puberty increases the chances of cardiometabolic, musculoskeletal and neurocognitive disorders, whereas early puberty is associated with increased risks of adult obesity, type 2 diabetes mellitus, cardiovascular diseases and various cancers, such as breast, endometrial and prostate cancer. Kennedy and Mitra's trailblazing studies, published in 1963 and using experimental models, were the first to demonstrate that nutrition is a key factor in puberty onset. Building on this work, the field has advanced substantially in the past decade, which is largely due to the impressive development of molecular tools for experimentation and population genetics. In this Review, we discuss the latest advances in basic and translational sciences underlying the nutritional and metabolic control of pubertal development, with a focus on perspectives and future directions.

Hormonal Imbalances in Prader-Willi and Schaaf-Yang Syndromes Imply the Evolution of Specific Regulation of Hypothalamic Neuroendocrine Function in Mammals

The hypothalamus regulates fundamental aspects of physiological homeostasis and behavior, including stress response, reproduction, growth, sleep, and feeding, several of which are affected in patients with Prader-Willi (PWS) and Schaaf-Yang syndrome (SYS). PWS is caused by paternal deletion, maternal uniparental disomy, or imprinting defects that lead to loss of expression of a maternally imprinted region of chromosome 15 encompassing non-coding RNAs and five protein-coding genes; SYS patients have a mutation in one of them, MAGEL2. Throughout life, PWS and SYS patients suffer from musculoskeletal deficiencies, intellectual disabilities, and hormonal abnormalities, which lead to compulsive behaviors like hyperphagia and temper outbursts. Management of PWS and SYS is mostly symptomatic and cures for these debilitating disorders do not exist, highlighting a clear, unmet medical need. Research over several decades into the molecular and cellular roles of PWS genes has uncovered that several impinge on the neuroendocrine system. In this review, we will discuss the expression and molecular functions of PWS genes, connecting them with hormonal imbalances in patients and animal models. Besides the observed hormonal imbalances, we will describe the recent findings about how the loss of individual genes, particularly MAGEL2, affects the molecular mechanisms of hormone secretion. These results suggest that MAGEL2 evolved as a mammalian-specific regulator of hypothalamic neuroendocrine function.

Mouse Testicular Mkrn3 Expression Is Primarily Interstitial, Increases Peripubertally, and Is Responsive to LH/hCG

Studies in humans and mice support a role for Makorin RING finger protein 3 (MKRN3) as an inhibitor of gonadotropin-releasing hormone (GnRH) secretion prepubertally, and its loss of function is the most common genetic cause of central precocious puberty in humans. Studies have shown that the gonads can synthesize neuropeptides and express MKRN3/Mkrn3 mRNA. Therefore, we aimed to investigate the spatiotemporal expression pattern of Mkrn3 in gonads during sexual development, and its potential regulation in the functional testicular compartments by gonadotropins. Mkrn3 mRNA was detected in testes and ovaries of wild-type mice at all ages evaluated, with a sexually dimorphic expression pattern between male and female gonads. Mkrn3 expression was highest peripubertally in the testes, whereas it was lower peripubertally than prepubertally in the ovaries. Mkrn3 is expressed primarily in the interstitial compartment of the testes but was also detected at low levels in the seminiferous tubules. In vitro studies demonstrated that Mkrn3 mRNA levels increased in human chorionic gonadotropin (hCG)-treated Leydig cell primary cultures. Acute administration of a GnRH agonist in adult mice increased Mkrn3 expression in testes, whereas inhibition of the hypothalamic-pituitary-gonadal axis by chronic administration of GnRH agonist had the opposite effect. Finally, we found that hCG increased Mkrn3 mRNA levels in a dose-dependent manner. Taken together, our developmental expression analyses, in vitro and in vivo studies show that Mkrn3 is expressed in the testes, predominantly in the interstitial compartment, and that Mkrn3 expression increases after puberty and is responsive to luteinizing hormone/hCG stimulation.