The functional study of a novel MKRN3 missense mutation associated with familial central precocious puberty

Central precocious puberty (CPP) refers to a syndrome of early puberty initiation with a characteristic increase in the release of gonadotropin-releasing hormone (GnRH); therefore, it is also called GnRH-related precocious puberty. About a quarter of idiopathic central precocious puberty (ICPP) may be familial. Studies suggest that mutations of makorin ring finger protein 3 (MKRN3) can cause familial central precocious puberty (FCPP). In this report, we describe a Chinese female patient carrying a novel MKRN3 variant (c.980G>A/p.Arg327His) and presenting the CPP phenotype. This novel variant attenuated its own ubiquitination, degradation, and inhibition on the transcriptional and translational activity of GNRH1, which was verified through functional tests. We can consider this variant as a loss-of-function mutation, which subsides the inhibition of GnRH1-related signaling and gives rise to GnRH-related precocious puberty.

Novel variants ensued genomic imprinting in familial central precocious puberty

INTRODUCTION

Central precocious puberty (CPP) is characterized by the early onset of puberty and is associated with the critical processes involved in the pubertal switch. The puberty-related gene pool in the human genome is considerably large though few have been described in CPP. Within those genes, the genomic imprinting features of the MKRN3 and DLK1 genes add additional complexity to the understanding of the pathologic pathways. This study aimed to investigate the molecular etiology in the CPP cohort.

METHODS

Eighteen familial CPP cases were investigated by Sanger sequencing for five CPP-related genes; DLK1, KISS1, KISS1R, MKRN3, and PROKR2. Segregation analysis was performed in all patients with pathogenic variants. Using an ELISA test, the functional pathogenicity of novel variants was also investigated in conjunction with serum delta-like 1 homolog (DLK1) concentrations.

RESULTS

In three probands, a known variant in the MKRN3 gene (c.982C>T/p.(Arg328Cys)) and two novel variants in the DLK1 gene (c.357C>G/p.(Tyr119Ter) and c.67+78C>T) were identified. All three were inherited from the paternal allele. The individuals carrying the DLK1 variants had low detectable DLK1 levels in their serum.

CONCLUSIONS

The frequencies were 5.5% (1/18) for MKRN3 11% (2/18) for DLK1, and none for either KISS1, KISS1R, and PROKR2. Low serum DLK1 levels in affected individuals supported the relationship between here described novel DLK1 gene variants with CPP. Nonsense nature of c.357C>G/p.(Tyr119Ter) and an alteration in the evolutionarily conserved nucleotide c.67+78C>T suggested the disruptive nature of the variant's compatibility with CPP.

MKRN3 circulating levels in girls with central precocious puberty caused by MKRN3 gene mutations

PURPOSE

MKNR3 is a paternally expressed gene whose mutations are the main cause of central precocious puberty (CPP). Protein circulating levels can be easily measured, as demonstrated in idiopathic CPP and healthy controls. No data are available for patients harboring an MKRN3 mutation. Our aim was to perform MKRN3 mutation screening and to investigate if circulating protein levels could be a screening tool to identify MKRN3 mutation in CPP patients.

METHODS

We enrolled 140 CPP girls and performed MKRN3 mutation analysis. Patients were stratified into two groups: idiopathic CPP (iCPP) and MKRN3 mutation-related CPP (MKRN3-CPP). Clinical characteristics were collected. Serum MKRN3 values were measured by a commercially available ELISA assay kit in MKRN3-CPP and a subgroup of 15 iCPP patients.

RESULTS

We identified 5 patients with MKRN3 mutations: one was a novel mutation (p.Gln352Arg) while the others were previously reported (p.Arg328Cys, p.Arg345Cys, p.Pro160Cysfs*14, p.Cys410Ter). There was a significant difference in circulating MKRN3 values in MKRN3-CPP compared to iCPP (p < 0.001). In MKRN3-CPP, the subject harboring Pro160Cysfs*14 presented undetectable levels. Subjects carrying the missense mutations p.Arg328Cys and p.Gln352Arg showed divergent circulating protein levels, respectively 40.56 pg/mL and undetectable. The patient with the non-sense mutation reported low but measurable MKRN3 levels (12.72 pg/mL).

CONCLUSIONS

MKRN3 defect in patients with CPP cannot be predicted by MKRN3 circulating levels, although those patients presented lower protein levels than iCPP. Due to the great inter-individual variability of the assay and the lack of reference values, no precise cut-off can be identified to suspect MKRN3 defect.

Differential Expression of RNAseq Imprinted Genes from Bovine Females Before and After Puberty

The productivity of beef cows depends on early reproduction traits such as puberty and has an economic impact on the efficiency of production system. Imprinted genes modulate many important endocrine processes such as growth, the onset of puberty and maternal reproductive and behavior. The role of imprinted genes in puberty is a challenging subject since they show the reciprocal role of maternal and paternal genomes in progeny. Although, there are evidences of the involvement of imprint genes in puberty in human, the role of this type of genes in the onset of puberty in cattle has not been studied yet. Here we examined the expression of 27 imprinted genes in pre and post puberty in a bovine model to find differentially expressed imprinted genes in maternal-paternal purebreds and reciprocal crosses across eight tissues and discussed the task of these genes in this crucial process of development and in onset of puberty. DLK1 and MKRN3 that previously described as cause of the central precocious puberty (CPP) in human were differentially expressed in this study. Functional annotation analysis of differentially imprinted genes in different tissues showed significant biological processes of cellular response to growth factor stimulus, response to growth factor, response to parathyroid hormone, developmental growth and the importance of alternative splicing. The results of this study have implications in understanding the role of imprinted genes in the onset of puberty in cattle.

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.

Novel MKRN3 Missense Mutations Associated With Central Precocious Puberty Reveal Distinct Effects on Ubiquitination

CONTEXT

Loss-of-function mutations in the maternally imprinted genes, MKRN3 and DLK1, are associated with central precocious puberty (CPP). Mutations in MKRN3 are the most common known genetic etiology of CPP.

OBJECTIVE

This work aimed to screen patients with CPP for MKRN3 and DLK1 mutations and analyze the effects of identified mutations on protein function in vitro.

METHODS

Participants included 84 unrelated children with CPP (79 girls, 5 boys) and, when available, their first-degree relatives. Five academic medical institutions participated. Sanger sequencing of MKRN3 and DLK1 5' upstream flanking and coding regions was performed on DNA extracted from peripheral blood leukocytes. Western blot analysis was performed to assess protein ubiquitination profiles.

RESULTS

Eight heterozygous MKRN3 mutations were identified in 9 unrelated girls with CPP. Five are novel missense mutations, 2 were previously identified in patients with CPP, and 1 is a frameshift variant not previously associated with CPP. No pathogenic variants were identified in DLK1. Girls with MKRN3 mutations had an earlier age of initial pubertal signs and higher basal serum luteinizing hormone and follicle-stimulating hormone compared to girls with CPP without MRKN3 mutations. Western blot analysis revealed that compared to wild-type MKRN3, mutations within the RING finger domain reduced ubiquitination whereas the mutations outside this domain increased ubiquitination.

CONCLUSION

MKRN3 mutations were present in 10.7% of our CPP cohort, consistent with previous studies. The novel identified mutations in different domains of MKRN3 revealed different patterns of ubiquitination, suggesting distinct molecular mechanisms by which the loss of MRKN3 results in early pubertal onset.

Clinical and Genetic Characterization of Familial Central Precocious Puberty

CONTEXT

Central precocious puberty (CPP) can have a familial form in approximately one-quarter of the children. The recognition of this inherited condition increased after the identification of autosomal dominant CPP with paternal transmission caused by mutations in the MKRN3 and DLK1 genes.

OBJECTIVE

We aimed to characterize the inheritance and estimate the prevalence of familial CPP in a large multiethnic cohort; to compare clinical and hormonal features, as well as treatment response to GnRH analogs (GnRHa), in children with distinct modes of transmission; and to investigate the genetic basis of familial CPP.

METHODS

We retrospectively studied 586 children with a diagnosis of CPP. Patients with familial CPP (n = 276) were selected for clinical and genetic analysis. Data from previous studies were grouped, encompassing sequencing of MKRN3 and DLK1 genes in 204 patients. Large-scale parallel sequencing was performed in 48 individuals from 34 families.

RESULTS

The prevalence of familial CPP was estimated at 22%, with a similar frequency of maternal and paternal transmission. Pedigree analyses of families with maternal transmission suggested an autosomal dominant inheritance. Clinical and hormonal features, as well as treatment response to GnRHa, were similar among patients with different forms of transmission of familial CPP. MKRN3 loss-of-function mutations were the most prevalent cause of familial CPP, followed by DLK1 loss-of-function mutations, affecting, respectively, 22% and 4% of the studied families; both affected exclusively families with paternal transmission. Rare variants of uncertain significance were identified in CPP families with maternal transmission.

CONCLUSION

We demonstrated a similar prevalence of familial CPP with maternal and paternal transmission. MKRN3 and DLK1 loss-of-function mutations were the major causes of familial CPP with paternal transmission.

The Congenital and Acquired Mechanisms Implicated in the Etiology of Central Precocious Puberty

The etiology of central precocious puberty (CPP) is multiple and heterogeneous, including congenital and acquired causes that can be associated with structural or functional brain alterations. All causes of CPP culminate in the premature pulsatile secretion of hypothalamic GnRH and, consequently, in the premature reactivation of hypothalamic-pituitary-gonadal axis. The activation of excitatory factors or suppression of inhibitory factors during childhood represent the 2 major mechanisms of CPP, revealing a delicate balance of these opposing neuronal pathways. Hypothalamic hamartoma (HH) is the most well-known congenital cause of CPP with central nervous system abnormalities. Several mechanisms by which hamartoma causes CPP have been proposed, including an anatomical connection to the anterior hypothalamus, autonomous neuroendocrine activity in GnRH neurons, trophic factors secreted by HH, and mechanical pressure applied to the hypothalamus. The importance of genetic and/or epigenetic factors in the underlying mechanisms of CPP has grown significantly in the last decade, as demonstrated by the evidence of genetic abnormalities in hypothalamic structural lesions (eg, hamartomas, gliomas), syndromic disorders associated with CPP (Temple, Prader-Willi, Silver-Russell, and Rett syndromes), and isolated CPP from monogenic defects (MKRN3 and DLK1 loss-of-function mutations). Genetic and epigenetic discoveries involving the etiology of CPP have had influence on the diagnosis and familial counseling providing bases for potential prevention of premature sexual development and new treatment targets in the future. Global preventive actions inducing healthy lifestyle habits and less exposure to endocrine-disrupting chemicals during the lifespan are desirable because they are potentially associated with CPP.

Circulating levels and the bioactivity of miR-30b increase during pubertal progression in boys

BACKGROUND

Puberty marks the transition from childhood to adulthood and is initiated by activation of a pulsatile GnRH secretion from the hypothalamus. MKRN3 functions as a pre-pubertal break on the GnRH pulse generator and hypothalamic expression and circulating levels of MKRN3 decrease peri-pubertally. In rodents, microRNA miR-30b seems to directly target hypothalamic MKRN3 expression - and in boys, circulating levels of miR-30b-5p increase when puberty is pharmacologically induced. Similarly, miR-200b-3p and miR-155-5p have been suggested to inhibit expression of other proteins potentially involved in the regulation of GnRH secretion. Here we measure circulating levels of these three miRNAs as boys progress through puberty.

MATERIALS AND METHODS

Forty-six boys from the longitudinal part of the Copenhagen Puberty Study were included. All boys underwent successive clinical examinations including estimation of testis size by palpation. miR-30b-5p, miR-200b-3p, and miR-155-5p were measured in serum by RT-qPCR using a kit sensitive to the phosphorylation status of the miRNAs. Thirty-nine boys had miRNA levels measured in three consecutive samples (pre-, peri-, and post-pubertally) and seven boys had miR-30b-5p levels measured in ten consecutive samples during the pubertal transition.

RESULTS

When circulating levels of miR-30b-5p in pre- and peri-pubertal samples were compared with post-pubertal levels, we observed a significant increase of 2.3 and 2.2-fold (p-value<6.0×10^-4), respectively, and a larger fraction of miR-30b-5p appeared to be phosphorylated post-pubertally indicating an increase in its bioactivity. We also observed a negative correlation between circulating levels of miR-30b-5p and MKRN3. The inter-individual variation in circulating miR-30b levels was substantial and we could not define a clinical threshold for miR-30b-5p suggestive of imminent puberty. Also, miR-155-5p showed significantly increasing levels from the peri- to the post-pubertal stage (p=3.0×10^-3), whereas miR-200b-3p did not consistently increase.

CONCLUSION

Both circulating levels of miR-30b-5p and its bioactivity increase during the pubertal transition in boys supporting its role in the activation of the HPG axis at the onset of physiologically normal puberty.

Effect of CPP-related genes on GnRH secretion and Notch signaling pathway during puberty

Puberty is a complex biological process of sexual development, influenced by genetic, metabolic-nutritional, environmental and socioeconomic factors, characterized by the development of secondary sexual characteristics, maturation of the gonads, leading to the acquisition of reproductive capacity. The onset of central precocious puberty (CPP) is mainly associated with the early activation of the hypothalamic-pituitary-gonadal (HPG) axis and increased secretion of gonadotropin-releasing hormone (GnRH), leading to increased pituitary secretion of luteinizing hormone (LH) and follicle-stimulating hormone (FSH) and activation of gonadal function. Due to the expense and invasiveness of current diagnostic testing and drug therapies for CPP, it would be helpful to find serum and genetic markers to facilitate diagnosis. In this paper, we summarized the related factors that may affect the expression of GnRH1 gene and the secretion and action pathway of GnRH and related sex hormones, and found several potential targets, such as MKRN3, DLK1 and KISS1. Although, the specific mechanism still needs to be further studied, we would be encouraged if the insights from this review could provide new insights for future research and clinical diagnosis and treatment of CPP.

MKRN3 circulating levels in Prader-Willi syndrome: a pilot study

CONTEXT

Hypogonadism in Prader-Willi syndrome (PWS) is generally attributed to hypothalamic dysfunction or to primary gonadal defect. MKRN3, a maternal imprinted gene located on 15q11.2-q13 region, encodes makorin ring finger protein 3, whose deficiency causes precocious puberty, an extremely rare symptom in PWS.

OBJECTIVE

This study aimed to evaluate MKRN3 levels in patients with PWS and to analyze its correlation with sexual hormone levels, insulin resistance and Body Mass Index (BMI).

METHODS

We performed an observational cross-sectional study and enrolled 80 patients with genetically confirmed diagnosis of PWS with median age of 9.6 years.

RESULTS

MKRN3 levels were measurable in 49 PWS patients with a geometric mean of 34.9 ± 22 pg/ml (median: 28.4). Unmeasurable levels of MKRN3 were found in 31 patients. No statistically significant differences were found between patients with and without measurable MKRN3 levels for any clinical, biochemical, or genetic characteristics. However, MKRN3 levels were inversely correlated with HOMA-IR index (p: 0.005) and HbA1c (p: 0.046) values. No statistically significant correlations were found between MKRN3 and LH, estradiol and testosterone concentrations, pubertal development and genetic defect, whereas a direct correlation with FSH was found (p: 0.007).

CONCLUSIONS

The typical genetic defect of PWS should lead to unmeasurable levels of the MKRN3 protein due to the inactivation of the paternal allele. Measurable circulating MKRN3 could suggest the possible involvement of tissue-specific imprinting mechanisms and other regulatory factors in gene expression. Correlations with HOMA-IR index, HbA1c, and FSH suggest peripheral actions of MKRN3, but future studies are warranted to investigate this topic.

Hypothalamic Overexpression of Makorin Ring Finger Protein 3 Results in Delayed Puberty in Female Mice

Makorin ring finger protein 3 (MKRN3) is an important neuroendocrine player in the control of pubertal timing and upstream inhibitor of gonadotropin-releasing hormone secretion. In mice, expression of Mkrn3 in the hypothalamic arcuate and anteroventral periventricular nucleus is high early in life and declines before the onset of puberty. Therefore, we aimed to explore if the persistence of hypothalamic Mkrn3 expression peripubertally would result in delayed puberty. Female mice that received neonatal bilateral intracerebroventricular injections of a recombinant adeno-associated virus expressing Mkrn3 had delayed vaginal opening and first estrus compared with animals injected with control virus. Subsequent estrous cycles and fertility were normal. Interestingly, male mice treated similarly did not exhibit delayed puberty onset. Kiss1, Tac2, and Pdyn mRNA levels were increased in the mediobasal hypothalamus in females at postnatal day 28, whereas kisspeptin and neurokinin B protein levels in the arcuate nucleus were decreased, following Mkrn3 overexpression, compared to controls. Cumulatively, these data suggest that Mkrn3 may directly or indirectly target neuropeptides of Kiss1 neurons to degradation pathways. This mouse model suggests that MKRN3 may be a potential contributor to delayed onset of puberty, in addition to its well-established roles in central precocious puberty and the timing of menarche.

The key roles of Makorin RING finger protein 3 (MKRN3) during the development of pubertal initiation and central precocious puberty (CPP)

Puberty is initiated from the continuous and growing pulsatile secretion of gonadotropin-releasing hormone (GnRH) in the hypothalamus and then the activation of the hypothalamic-pituitary-gonadal (HPG) axis. Numerous factors involve pubertal initiation whose abnormality may come from dysfunction of these regulators. Makorin RING finger protein 3 (MKRN3) inhibits the secretion of GnRH and plays indispensable roles during the development of pubertal onset, and mutations of MKRN3 showed the commonest genetic cause of central precocious puberty (CPP). Recently, growing studies have revealed the functional mechanisms of MKRN3 in the pubertal initiation and the occurrence of CPP. In this review, we mainly summarized the research advances on the roles of MKRN3 in the development of pubertal onset and their underpinning mechanisms, contributing to the better understanding of the precise mechanisms of pubertal initiation and the pathogenesis of CPP.

Precocious sexual maturation: Unravelling the mechanisms of pubertal onset through clinical observations

Puberty is a crucial biological process normally occurring at a specific time during the lifespan, during which sexual and somatic maturation are completed, and reproductive capacity is reached. Pubertal timing is not only determined by genetics, but also by endogenous and environmental cues, including nutritional and metabolic signals. During the last decade, we have learned much regarding the essential roles of kisspeptins and the neuropeptide pathways that converge on these neurones to modulate kisspeptin signalling, as well as neurokinin B and dynorphin, the co-transmitters of Kiss1 neurones in the arcuate nucleus, and the effects of melanocortins on puberty. Indeed, melanocortins are involved in transmitting the regulatory actions of metabolic cues on pubertal maturation. Intracellular metabolic sensors, such as the AMP-activated protein kinase and the fuel-sensing deacetylase SIRT1, have been shown to contribute to puberty. Further understanding of these signals and regulatory circuits will help uncover the intimacies of the central control of puberty, as well as how alterations in metabolic status, ranging from undernutrition to obesity, affect the pubertal process. Precocious puberty is rare and has a clear female predominance. Central precocious puberty (CPP) is diagnosed when premature activation of the hypothalamic-pituitary axis occurs. Its causes are heterogeneous, with alterations of the central nervous system being of special interest, and with environmental factors also playing a role in some cases. During the last decade, several mutations in different genes (including KISS1, KISS1R, MKRN3 and DLK1) that cause CPP have been discovered. Loss-of-function mutations in MKRN3 are the most common monogenic cause of CPP known to date. Here, we review and update what is known regarding the genotype-phenotype relationship in patients with CPP.

MKRN3 role in regulating pubertal onset: the state of art of functional studies

Puberty is a critical process characterized by several physical and psychological changes that culminate in the achievement of sexual maturation and fertility. The onset of puberty depends on several incompletely understood mechanisms that certainly involve gonadotropin-releasing hormone (GnRH) and its effects on the pituitary gland. The role of makorin ring finger protein 3 (MKRN3) in the regulation of pubertal timing was revealed when loss-of-function mutations were identified in patients with central precocious puberty (CPP), which to date, represent the most commonly known genetic cause of this condition. The MKRN3 gene showed ubiquitous expression in tissues from a broad spectrum of species, suggesting an important cellular role. Its involvement in the initiation of puberty and endocrine functions has just begun to be studied. This review discusses some of the recent approaches developed to predict MKRN3 functions and its involvement in pubertal development.

Difference of Precocious Puberty Between Before and During the COVID-19 Pandemic: A Cross-Sectional Study Among Shanghai School-Aged Girls

OBJECTIVE

To compared the incidence rates and clinical features of precocious girls before and during the COVID-19 pandemic among Shanghai school-aged girls, and explored the potential mechanisms.

METHODS

This cross-sectional study collected medical data about precocious girls between 2016 and 2020 from Shanghai Children's Medical Center. Data of inpatient precocious girls from March to August in 2016-2019 (n=246) and 2020 (n=237) were collected. Subjects with abnormal brain and pituitary gland MRI reports, other endocrine diseases or chronic diseases were excluded. Finally, 209 precocious girls were included in the 2016-2019 group and 191 precocious girls were include in the 2020 group. Monthly incidence rates and clinical features were compared between before and during the COVID-19 pandemic. Linear regression models were used to examine the associations between biomarkers to explore the potential mechanisms.

RESULTS

Monthly incidence rates of precocious puberty in outpatient girls from March to December 2020 (0.44-1.36%) and in inpatient girls from March to August 2020 (27.04-47.83%) were higher than those in 2016-2019 (0.30-0.52% and 10.53-18.42%, respectively). Serum concentrations of GnRH were higher in the 2020 group than in the 2016-2019 group (2.81 vs 1.99 mg/L). Serum concentrations of MKRN3 (1.02 vs 1.93 ng/ml) and ghrelin (0.38 vs 0.88 ng/ml) were lower in the 2020 group than in the 2016-2019 group. Moreover, the serum concentration of ghrelin was positively associated with the serum concentration of MKRN3 [β=0.891 (95% CI, 0.612, 1.171); p<0.001].

CONCLUSIONS

These findings suggest an increased incidence of precocious puberty during the COVID-19 pandemic among Shanghai school-aged girls, which may be associated with decreased serum concentrations of MKRN3 and ghrelin, and indicated ghrelin as a potential regulatory mechanism of puberty.

Methylation status of hypothalamic Mkrn3 promoter across puberty

Makorin RING finger protein 3 (MKRN3) is an important factor located on chromosome 15 in the imprinting region associated with Prader-Willi syndrome. Imprinted MKRN3 is expressed in hypothalamic regions essential for the onset of puberty and mutations in the gene have been found in patients with central precocious puberty. The pubertal process is largely controlled by epigenetic mechanisms that include, among other things, DNA methylation at CpG dinucleotides of puberty-related genes. In the present study, we investigated the methylation status of the Mkrn3 promoter in the hypothalamus of the female mouse before, during and after puberty. Initially, we mapped the 32 CpG dinucleotides in the promoter, the 5'UTR and the first 50 nucleotides of the coding region of the Mkrn3 gene. Moreover, we identified a short CpG island region (CpG islet) located within the promoter. Methylation analysis using bisulfite sequencing revealed that CpG dinucleotides were methylated regardless of developmental stage, with the lowest levels of methylation being found within the CpG islet region. In addition, the CpG islet region showed significantly lower methylation levels at the pre-pubertal stage when compared with the pubertal or post-pubertal stage. Finally, in silico analysis of transcription factor binding sites on the Mkrn3 CpG islet identified the recruitment of 29 transcriptional regulators of which 14 were transcriptional repressors. Our findings demonstrate the characterization and differential methylation of the CpG dinucleotides located in the Mkrn3 promoter that could influence the transcriptional activity in pre-pubertal compared to pubertal or post-pubertal period. Further studies are needed to clarify the possible mechanisms and effects of differential methylation of the Mkrn3 promoter.

Elevated expression of MKRN3 in squamous cell carcinoma of the head and neck and its clinical significance

BACKGROUND

Squamous cell carcinoma of the head and neck (SCCHN) is one of the most common types of cancer that cause a substantial number of cancer-related deaths. Our previous study has revealed that makorin ring finger protein 3 (MKRN3) may act as a key regulator of the SCCHN tumorigenesis; however, its specific role in SCCHN progression has not been reported.

METHODS

The Cancer Genome Atlas (TCGA) data analysis and quantitative polymerase chain reaction (qPCR) were used to quantify the MKRN3 mRNA expression levels in SCCHN; immunohistochemical staining or immunoblotting analyses were performed to detect MKRN3 protein expression. Kaplan-Meier plotter was used to assess the prognostic values of MKRN3 in terms of overall survival and disease-free survival. The expression differences based on various clinicopathological features were evaluated using subgroup analysis and forest map analysis. The regulatory mechanism of MKRN3 was further investigated using gene ontology and Kyoto Encyclopedia of Genes and Genomes analyses. Subsequently, STRING was used to perform a co-expression and enrichment analysis for MKRN3. Homologous modeling, molecular docking, and western blot analyses were performed to investigate the relationship between MKRN3 and its potential target gene P53.

RESULTS

MKRN3 was ectopically expressed between cancerous and noncancerous SCCHN tissues, and its expression level was tightly associated with high T classifications as well as advanced clinical stages. qPCR analysis revealed that MKRN3 was upregulated in the SCCHN cell line. Moreover, Kaplan-Meier and Cox regression analyses indicated that SCCHN patients with high MKRN3 expression had poorer prognosis and that MKRN3 was a potential prognostic marker for SCCHN. Using gene ontology and Kyoto Encyclopedia of Genes and Genomes analyses, we determined that MKRN3 may be involved in the regulation of synthesis and metabolism and cell growth, death and motility, as well as cancer pathways associated with SCCHN progression. Mechanism investigation further revealed that P53, a potential target of MKRN3, may be involved in the SCCHN tumorigenesis mediated by MKRN3.

CONCLUSIONS

We performed a comprehensive evaluation of the clinical significance of MKRN3 and explored its underlying mechanisms. We concluded that MKRN3 represents a valuable predictive biomarker and potential therapeutic target in SCCHN.

Pathogenic and Low-Frequency Variants in Children With Central Precocious Puberty

Background

Central precocious puberty (CPP) due to premature activation of GnRH secretion results in early epiphyseal fusion and to a significant compromise in the achieved final adult height. Currently, few genetic determinants of children with CPP have been described. In this translational study, rare sequence variants in MKRN3, DLK1, KISS1, and KISS1R genes were investigated in patients with CPP.

Methods

Fifty-four index girls and two index boys with CPP were first tested by Sanger sequencing for the MKRN3 gene. All children found negative (n = 44) for the MKRN3 gene were further investigated by whole exome sequencing (WES). In the latter analysis, the status of variants in genes known to be related with pubertal timing was compared with an in-house Cypriot control cohort (n = 43). The identified rare variants were initially examined by in silico computational algorithms and confirmed by Sanger sequencing. Additionally, a genetic network for the MKRN3 gene, mimicking a holistic regulatory depiction of the crosstalk between MKRN3 and other genes was designed.

Results

Three previously described pathogenic MKRN3 variants located in the coding region of the gene were identified in 12 index girls with CPP. The most prevalent pathogenic MKRN3 variant p.Gly312Asp was exclusively found among the Cypriot CPP cohort, indicating a founder effect phenomenon. Seven other CPP girls harbored rare likely pathogenic upstream variants in the MKRN3. Among the 44 CPP patients submitted to WES, nine rare DLK1 variants were identified in 11 girls, two rare KISS1 variants in six girls, and two rare MAGEL2 variants in five girls. Interestingly, the frequent variant rs10407968 (p.Gly8Ter) of the KISS1R gene appeared to be less frequent in the cohort of patients with CPP.

Conclusion

The results of the present study confirm the importance of the MKRN3-imprinted gene in genetics of CPP and its key role in pubertal timing. Overall, the results of the present study have emphasized the importance of an approach that aligns genetics and clinical aspects, which is necessary for the management and treatment of CPP.

A Novel Loss-of-Function MKRN3 Variant in a Chinese Patient With Familial Precocious Puberty: A Case Report and Functional Study

Background: Central precocious puberty (CPP) is one of the most common and complex problems in clinical pediatric endocrinology practice. Mutation of the MKRN3 gene can cause familial CPP. Methods and Results: Here we reported a Chinese patient bearing a novel MKRN3 mutation (c.G277A/p.Gly93Ser) and showing the CPP phenotype. Functional studies found that this mutation of MKRN3 attenuated its autoubiquitination, degradation, and inhibition on the transcriptional activity of GNRH1, KISS1, and TAC3 promoters. Conclusion: MKRN3 (Gly93Ser) is a loss-of-function mutation, which attenuates the inhibition on GnRH1-related signaling, suggesting that this mutant can lead to central precocious puberty.

Serum level of NPTX1 is independent of serum MKRN3 in central precocious puberty

OBJECTIVES

Makorin ring finger protein 3 (MKRN3) is associated with the initiation of puberty, and loss of function mutation of MKRN3 is the most common genetic cause of central precocious puberty (CPP). A recent study reported that MKRN3 interacts with and suppresses neural pentraxin-1 precursor (NPTX1) activity via polyubiquitination during early puberty in the mouse hypothalamus. This study investigated the correlation between serum NPTX1 and MKRN3 in CPP girls and predicted the potential role of NPTX1 in pubertal progression.

METHODS

In this case-control study, we examined 34 girls diagnosed with CPP and 34 healthy prepubertal girls. Anthropometric and hormonal parameters were measured and serum levels of NPTX1 and MKRN3 were evaluated with commercial enzyme-linked immunosorbent assay kits.

RESULTS

Serum MKRN3 level decreased significantly in CPP patients compared to controls (344.48 ± 333.77 and 1295.21 ± 780.80 pg/mL, respectively, p<0.001). Serum MKRN3 tended to decrease as Tanner breast stage increased. However, no significant difference was observed in serum NPTX1 levels between patients and controls (20.14 ± 31.75 ng/mL and 12.93 ± 8.28 ng/mL, respectively, p=0.248). The serum level of NPTX1 did not change significantly with the Tanner breast stage. Serum NPTX1 was correlated with the height standard deviation score (r=0.255; p<0.05), but was not correlated with serum MKRN3 level or the others. Conclusion: Although serum NPTX1 level was independent of serum MKRN3 level, the possibility they might be involved in the progression of puberty or CPP remains. Further research is needed to determine their role in the hypothalamus.

The Peripubertal Decline in Makorin Ring Finger Protein 3 Expression is Independent of Leptin Action

A critical body weight is necessary for pubertal development, an effect mediated in part by leptin. The potential regulation by leptin of Makorin Ring Finger Protein 3 (MKRN3), in which loss-of-function mutations are the most common genetic cause of central precocious puberty, has not been previously explored. In mice, expression of Mkrn3 in the hypothalamic arcuate nucleus is high early in life and declines before the onset of puberty. Therefore, we aimed to explore if leptin contributes to the decrease in hypothalamic Mkrn3 mRNA levels observed in mice during pubertal development. We first used a leptin-deficient (ob/ob) mouse model. Mkrn3 mRNA levels in the mediobasal hypothalamus (MBH), which includes the arcuate nucleus, and in the preoptic area (POA), both showed a significant decrease with age from postnatal day (PND) 12 to PND30 in ob/ob mice in both males and females, similar to that observed in wild-type mice. To further explore the effects of leptin on Mkrn3 expression, we exposed prepubertal wild-type mice to high levels of leptin from age PND9-12, which did not result in any significant difference in Mkrn3 expression levels in either the MBH or POA. In summary, regulation of Mkrn3 expression by leptin was not observed in either the MBH or the POA, 2 hypothalamic sites important for pubertal maturation. These data suggest that the decline in Mkrn3 at the onset of puberty may occur independently of leptin and support our hypothesis that MKRN3 is a bona fide controller of puberty initiation.

Outcomes of Patients with Central Precocious Puberty Due to Loss-of-Function Mutations in the MKRN3 Gene after Treatment with Gonadotropin-Releasing Hormone Analog

INTRODUCTION

Loss-of-function mutation of MKRN3 represents the most frequent genetic cause of familial central precocious puberty (CPP). The outcomes of gonadotropin-releasing hormone analog (GnRHa) treatment in CPP patients with MKRN3 defects are unknown.

OBJECTIVE

To describe the clinical and hormonal features of patients with CPP with or without MKRN3 mutations after GnRHa treatment. Anthropometric, metabolic and reproductive parameters were evaluated.

PATIENTS AND METHODS

Twenty-nine female patients with CPP due to loss-of-function mutations in the MKRN3 and 43 female patients with idiopathic CPP were included. Their medical records were retrospectively evaluated for clinical, laboratory, and imaging study, before, during, and after GnRHa treatment. All patients with idiopathic CPP and 11 patients with CPP due to MKRN3 defects reached final height (FH).

RESULTS

At the diagnosis, there were no significant differences between clinical and laboratory features of patients with CPP with or without MKRN3 mutations. A high prevalence of overweight and obesity was observed in patients with CPP with or without MKRN3 mutations (47.3 and 50%, respectively), followed by a significant reduction after GnRHa treatment. No significant differences in the values of mean FH and target height were found between the 2 CPP groups after GnRHa treatment. Menarche occurred at the expected age in patients with or without CPP due to MKRN3 mutations (11.5 ± 1.3 and 12 ± 0.6 years, respectively). The prevalence of polycystic ovarian syndrome was 9.1% in patients with CPP due to MKRN3 mutations and 5.9% in those with idiopathic CPP.

CONCLUSION

Anthropometric, metabolic, and reproductive outcomes after GnRHa treatment were comparable in CPP patients, with or without MKRN3 mutations, suggesting the absence of deleterious effects of MKRN3 defects in young female adults' life.

Serum Makorin ring finger protein 3 values for predicting Central precocious puberty in girls

This study evaluated the serum level of MKRN3 and investigated its diagnostic usefulness in girls with central precocious puberty (CPP). In total, 41 girls with CPP and 35 age-matched normal control girls were enrolled. Serum values of MKRN3 were measured in both groups. Gonadotropin and estradiol concentrations were evaluated after 6 and 12 months of GnRH agonist (GnRHa) treatment in CPP patients. The MKRN3 concentrations were much lower in the patient group than in the control group (p = .005). Over 1 year of GnRHa treatment in patients, the gonadotropin concentrations were significantly decreased (p < .05), while the MKRN3 concentrations were unchanged (p > .05). MKRN3 levels were inversely correlated to standard deviation (SD) in height (r = -0.46, p = .000), SD in weight (r = -0.32, p = .005), Tanner stage (r = -0.41, p = .000), and bone age (r = -0.46, p = .000). Based on ROC analysis, the area under curve was 0.758 for MKRN3, with 82.9% sensitivity and 68.5% specificity. The measurement of serum MKRN3 level may provide some help for CPP prediction, but relatively various values need further validation.

MKRN3 Mutations in Central Precocious Puberty: A Systematic Review and Meta-Analysis

MKRN3 mutations represent the most common genetic cause of central precocious puberty (CPP) but associations between genotype and clinical features have not been extensively explored. This systematic review and meta-analysis investigated genotype-phenotype associations and prevalence of MKRN3 mutations in CPP. The search was conducted in seven electronic databases (Cochrane, EMBASE, LILACS, LIVIVO, PubMed, Scopus, and Web of Science) for articles published until 4 September 2018. Studies evaluating MKRN3 mutations in patients with CPP were considered eligible. A total of 22 studies, studying 880 subjects with CPP, fulfilled the inclusion criteria. Eighty-nine subjects (76 girls) were identified as harboring MKRN3 mutations. Girls, compared with boys, exhibited earlier age at pubertal onset (median, 6.0 years; range, 3.0 to 7.0 vs 8.5 years; range, 5.9 to 9.0; P < 0.001), and higher basal FSH levels (median, 4.3 IU/L; range, 0.7 to 13.94 IU/L vs 2.45 IU/L; range, 0.8 to 13.70 IU/L; P = 0.003), and bone age advancement (ΔBA; median, 2.3 years; range, -0.9 to 5.2 vs 1.2 years; range, 0.0 to 2.3; P = 0.01). Additional dysmorphisms were uncommon. A total of 14 studies evaluating 857 patients were included for quantitative analysis, with a pooled overall mutation prevalence of 9.0% (95% CI, 0.04 to 0.15). Subgroup analysis showed that prevalence estimates were higher in males, familial cases, and in non-Asian countries. In conclusion, MKRN3 mutations are associated with nonsyndromic CPP and manifest in a sex-dimorphic manner, with girls being affected earlier. They represent a common cause of CPP in western countries, especially in boys and familial cases.

Evolutionary Analysis of Makorin Ring Finger Protein 3 Reveals Positive Selection in Mammals

Makorin ring finger proteins (MKRNs) are part the of ubiquitin-proteasome system; a complex system important for cell functions. Ubiquitin fate through proteolytic, non-proteolytic pathways varies, depending on covalent linkage between ubiquitin and protein substrates. Makorin ring finger protein 3 is an integral part of covalent linkage of ubiquitin to protein substrates. Similar to others imprinted genes, MKRN3 also evolve under positive selection; however, which codons are specifically selected in MKRN3 during evolution are needed to be explored. Different maximum-likelihood (ML) codon-based methodologies were used to ascertain positive selection signatures in 22 mammalian sequences of MKRN3 to probe an individual codon for positive selection signatures. By applying the HyPhy software package implemented in the Data Monkey Web Server and CODEML implemented in PAML, evolutionary analysis based on two Ml frameworks were conducted. The analysis was executed by comparing M1a against M2a, M7 against M8, and PAML models and 2∆Lnl (LRT) was resulted by likelihood logs. M1a contributed ω1 (dN/dS) with LRT value (∆Lnl) 12.01, and positive selection was found in M2a with ω3 = 2.23603. To further improve selection test, M8 was compared to M7 with 2∆Lnl (LRT) 30.17, and M8 showed positive selection with ω = 1.55759. The data were fit to M8 than M7, which suggests that M8 was the most significant model of selection. M8 was judged encouraging for this analysis and used to establish a positive selection of MKRN3 proteins. We found Gly312 as a positively selected amino acid in a zinc finger motif/Really Interesting New Gene (RING) finger motif; the former ones’ region is involved in RNA binding and the later ones in ubiquitin ligase activity of the protein, vital for protein function. Selection analyses of MKRNs might advance the developments in unique approaches that could lead to genetic progress over the selection of superior individuals with the breeding values higher for certain traits as ancestries to get the next generation.

MKRN3 Levels in Girls with Central Precocious Puberty during GnRHa Treatment: A Longitudinal Study

BACKGROUND

Recently, mutations of makorin RING finger protein 3 (MKRN3) have been identified in familial central precocious puberty (CPP). Serum levels of this protein decline before the pubertal onset in healthy girls and boys and are lower in patients with CPP compared to prepubertal matched pairs. The aim of our study was to investigate longitudinal changes in circulating MKRN3 levels in patients with CPP before and during GnRH analogs (GnRHa) treatment.

METHODS

We performed a longitudinal prospective study. We enrolled 15 patients with CPP aged 7.2 years (range: 2-8) with age at breast development onset < 8 years and 12 control girls matched for the time from puberty onset (mean age 11.8 ± 1.2 years). Serum values of MKRN3, gonadotropins, and 17β-estradiol were evaluated before and during treatment with GnRHa (at 6 and 12 months). The MKRN3 gene was genotyped in CPP patients. In the girls from the control group, only basal levels were analyzed.

RESULTS

No MKRN3 mutations were found among CPP patients. MKRN3 levels declined significantly from baseline to 6 months of GnRHa treatment (p = 0.0007) and from 6 to 12 months of treatment (p = 0.003); MKRN3 levels at 6 months were significantly lower than in the control girls (p < 0.0001).

CONCLUSIONS

We showed that girls with CPP had a decline in peripheral levels of MKRN3 during GnRHa treatment. Our data suggest a suppression of MKRN3 by continuous pharmacological administration of GnRHa.

Central Precocious Puberty Caused by Novel Mutations in the Promoter and 5'-UTR Region of the Imprinted MKRN3 Gene

Background: Central Precocious Puberty (CPP) is clinically defined by the development of secondary sexual characteristics before the age of 8 years in girls and 9 years in boys. To date, mutations in the coding region of KISS1, KISS1R, PROKR2, DLK1, and MKRN3 genes have been reported as causative for CPP. This study investigated the presence of causative mutations in both the promoter and the 5'-UTR regions of the MKRN3 gene. Methods: Sanger DNA sequencing was used for screening the proximal promoter and 5'-UTR region of the MKRN3 gene in a group of 73 index girls with CPP. Mutations identified were cloned in luciferase reporter gene vectors and transiently transfected in GN11 cells in order to check for changes in the activity of the MKRN3 promoter. GN11 cells were previously checked for Mkrn3 expression using lentivirus mediated knock-down. In silico analysis was implemented for the detection of changes in the mRNA secondary structure of the mutated MKRN3 5'-UTR. Results: Three novel heterozygous mutations (-166, -865, -886 nt upstream to the transcription start site) located in the proximal promoter region of the MKRN3 gene were identified in six non-related girls with CPP. Four of these girls shared the -865 mutation, one the -166, and another one the -886. A 5'-UTR (+13 nt downstream to the transcription start site) novel mutation was also identified in a girl with similar clinical phenotype. Gene reporter assay evaluated the identified promoter mutations and demonstrated a significant reduction of MKRN3 promoter activity in transfected GN11 cells. In silico analysis for the mutated 5'-UTR predicted a significant change of the mRNA secondary structure. The minimum free energy (MFE) of the mutated 5'-UTR was higher when compared to the corresponding wild-type indicating less stable RNA secondary structure. Conclusion: Our findings demonstrated novel genetic alterations in the promoter and 5'-UTR regulatory regions of the MKRN3 gene. These changes add to another region to check for the etiology of CPP.

MKRN3 Interacts With Several Proteins Implicated in Puberty Timing but Does Not Influence GNRH1 Expression

Paternally-inherited loss-of-function mutations in makorin ring finger protein 3 gene (MKRN3) underlie central precocious puberty. To investigate the puberty-related mechanism(s) of MKRN3 in humans, we generated two distinct bi-allelic MKRN3 knock-out human pluripotent stem cell lines, Del 1 and Del 2, and differentiated them into GNRH1-expressing neurons. Both Del 1 and Del 2 clones could be differentiated into neuronal progenitors and GNRH1-expressing neurons, however, the relative expression of GNRH1 did not differ from wild type cells (P = NS). Subsequently, we investigated stable and dynamic protein-protein interaction (PPI) partners of MKRN3 by stably expressing it in HEK cells followed by mass spectrometry analyses. We found 81 high-confidence novel protein interaction partners, which are implicated in cellular processes such as insulin signaling, RNA metabolism and cell-cell adhesion. Of the identified interactors, 20 have been previously implicated in puberty timing. In conclusion, our stem cell model for generation of GNRH1-expressing neurons did not offer mechanistic insight for the role of MKRN3 in puberty initiation. The PPI data, however, indicate that MKRN3 may regulate puberty by interacting with other puberty-related proteins. Further studies are required to elucidate the possible mechanisms and outcomes of these interactions.

Molecular Screening of MKRN3, DLK1, and KCNK9 Genes in Girls with Idiopathic Central Precocious Puberty

BACKGROUND

Mutations in the imprinted gene MKRN3 have been described as a common genetic cause of idiopathic central precocious puberty (CPP), in particular in familial cases. However, the exact prevalence of mutations is unknown. Single nucleotide polymorphisms in 2 other imprinted genes, DLK1 and KCNK9, have been associated with age at menarche. We investigated the prevalence of mutations in MKRN3, DLK1, and KCNK9 genes in a cohort of girls with idiopathic CPP.

METHODS

MKRN3, DLK1, and KCNK9 coding regions were sequenced in 60 girls with idiopathic CPP (familial in 23 cases).

RESULTS

Three mutations, including a new one, in MKRN3 were found in 2 familial cases (c.1229G>A; p.Cys410Ter and c.477_485del; p.Pro160Cysfs*14) (8.7%) and in 1 sporadic case (c.982C>T; p.Arg328Cys) (2.8%). We did not find rare variants in DLK1 and KCNK9 genes.

CONCLUSIONS

(1) The prevalence of MKRN3 mutations in our cohort was similar to that reported in the literature in sporadic cases but lower than previously described in familial ones. This could be due to different inheritance patterns of families studied; (2) we expanded the phenotype of MKRN3 defects describing 3 more patients with MKRN3 mutations; and (3) point mutations in DLK1 and KCNK9 at least do not seem to be a common cause of CPP in girls.

MKRN3 levels in girls with central precocious puberty and correlation with sexual hormone levels: a pilot study

PURPOSE

Recently, mutations of makorin RING-finger protein 3 (MKRN3) have been described in familial central precocious puberty. Serum levels of this protein decline before the pubertal onset in healthy girls and boys. The aim of the study is to investigate MKRN3 circulating levels in patients with central precocious puberty.

METHODS

We performed an observational cross-sectional study. We enrolled 17 patients with central precocious puberty aged 7 years (range: 2-8 years) and breast development onset <8 years; 17 prepubertal control age-matched patients aged 6.3 years (2-8.2); and 10 pubertal stage-matched control patients aged 11.4 years (9-14). Serum values of MKRN3, gonadotropins, (17)estradiol and Anti-Müllerian Hormone were evaluated and the MKRN3 genotyped in central precocious puberty patients.

RESULTS

No MKRN3 mutation was found among central precocious puberty patients. MKRN3 levels were lower in patients with central precocious puberty compared to prepubertal age-matched ones (p: 0.0004) and comparable to those matched for pubertal stage. MKRN3 levels were inversely correlated to Body Mass Index Standard Deviations (r:-0.35; p:0.02), Luteinizing Hormone (r:-0.35; p:0.03), FSH (r:-0.37; p:0.02), and (17)estradiol (r: -0.36; p:0.02).

CONCLUSIONS

We showed that girls with central precocious puberty had lower peripheral levels of MKRN3 compared to age-matched pairs and that they negatively correlated to gonadotropins, estrogen, and BMI. Our findings support the MKRN3 involvement in central precocious puberty also in absence of deleterious mutations, although our sample size is small. In addition our data suggest the role of MKRN3 in the complex mechanism controlling puberty onset and its interaction with other factors affecting puberty such as nutrition.

Disruption of NNAT, NAP1L5 and MKRN3 DNA methylation and transcription in rabbit parthenogenetic fetuses

Parthenogenetically activated oocytes cannot develop to term in mammals due to lack of paternal gene expression. Disruption of imprinted gene expression and DNA methylation status in parthenogenetic fetuses has been reported in mice and pigs, but not in rabbits. In this study, the genomic imprinting status of the paternally expressed genes Neuronatin (NNAT), Nucleosome assembly protein 1-like 5 (NAP1L5), and Makorin ring finger protein 3 (MKRN3) was compared between rabbit parthenogenetic (PA) and normally fertilized fetuses (Con) using quantitative real-time PCR (qRT-PCR) and bisulfite sequencing PCR (BSP). The results revealed a significantly reduced expression of NNAT, NAP1L5, and MKRN3 in rabbit PA fetuses compared with Con fetuses (p<0.05). In addition, the BSP results demonstrated hypermethylation in the differentially methylated regions (DMRs) of NNAT, NAP1L5, and MKRN3 in rabbit PA fetuses. Taken together, these results suggest that hypermethylation of DMRs is associated with decreased NNAT, NAP1L5, and MKRN3 expression, which may be responsible for developmental failure of rabbit PA fetuses.