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

The Role of DLK1 Deficiency in Central Precocious Puberty and Association with Metabolic Dysregulation

INTRODUCTION

Precocious puberty is defined as the appearance of secondary sexual characteristics before the age of 8 years in girls and 9 years in boys. Central precocious puberty (CPP) is a rare condition that is diagnosed when premature activation of the hypothalamic-pituitary-gonadal axis is detected, in association with precocious breast development or testicular growth. Idiopathic CPP is historically considered to be the most common form, but in recent years defects in a small but growing number of genes regulating the timing of puberty have been identified in an increasing proportion of cases of CPP. Delta-like non-canonical Notch ligand 1 (DLK1) is understood to be one of the key genes involved in the etiology of CPP, although its mechanistic role is not yet fully understood.

CASE PRESENTATION

We identified a novel de novo variant of DLK1 (c.835C>T; p.Gln279*) in an 8-year-old girl of Bangladeshi origin. She presented with an advanced Tanner staging of B4P4A2, significantly advanced bone age (BA, 13 years), a near-adult proportioned uterus, with a history of menarche at the age of 7.4 years. Diagnosis was confirmed by raised basal luteinizing hormone concentration. She was found to have truncal obesity associated with abnormal fasting insulin levels and mildly elevated cholesterol levels. These findings are consistent with previous literature describing an association between patients with DLK1 deficiency and an impaired metabolic profile. The patient was treated for 2 years with GnRH agonists with ongoing biochemical follow-up into adolescence.

CONCLUSION

This case illustrates the susceptibility to metabolic derangement for patients with mutations in DLK1 and the need for ongoing monitoring after puberty. Our summary of previously identified DLK1 variants and their metabolic consequences demonstrates the frequency of obesity, lipid abnormalities, and insulin dysregulation in this patient cohort in childhood and beyond. This knowledge can guide future clinical practice for patients with CPP patients due to DLK1 deficiency.

Zhibai dihuang pill (ZBDH) exhibits therapeutic effects on idiopathic central sexual precocity in rats by modulating the gut microflora

To reveal the role of gut microbiota (GM) in the occurrence and development of idiopathic central precocious puberty (ICPP) using 16S rDNA sequencing and bioinformatics analysis. The Danazol-induced ICPP model was successfully constructed in this study. ZBDH and GnRHa treatments could effectively inhibit ICPP in rats, as manifested by the delayed vaginal opening time, reduced weight, decreased uterine organ coefficient, and decreased uterine wall thickness and corpus luteum number, as well as remarkably reduced serum hormone (LH, FSH, and E2) levels. According to 16S rDNA sequencing analysis results, there was no significant difference in the GM community diversity across different groups; however, the composition of the microbial community and the abundance of the dominant microbial community were dramatically different among groups. ZBDH and GnRHa treatments could effectively reduce the abundance of Muribaculateae and Lactobacillus and promote Prevotella abundance. ZBDH and GnRHa were effective in treating Danazol-induced ICPP model rats. The therapeutic effects of ZBDH and GnRHa could be related to the changes in GM in rats.

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.

[Gonadotropin-dependent precocious puberty: genetic and clinical characteristics]

BACKGROUND

In 90% cases of girls and 25-60% cases of boys the cause of gonadotropin-dependent precocious puberty (PP) is unclear. Up to 25-27.5% of gonadotropin-dependent PP cases are monogenic and suggest autosomal-dominant inheritance with incomplete sex-dependent penetrance. To date, mutations in genes KISS1, KISS1R, MKRN3, DLK1 have been described as causal variants leading to precocious hypothalamic-pituitary axis activation in childhood. Genetic testing in patients with hereditary forms of PP can expand our knowledge of underlying molecular mechanisms of the disease and it  is also necessary for genetic counselling.

AIM

To study clinical features and genetic characteristics of patients with idiopathic gonadotropin-dependent precocious puberty.

MATERIALS AND METHODS

A group of patients with idiopathic gonadotropin-dependent precocious puberty and positive family history (early or precocious puberty) was examined. Laboratory and instrumental diagnostic tests, full-exome sequencing (NGS, next-generation sequencing) were provided for all patients.

RESULTS

The study included 30 patients (29 girls, 1 boy) with idiopathic gonadotropin-dependent precocious puberty. The median of patients age at the time of the examination was 7,2 years [6,5; 7,7]. Positive family history presented in all cases: in 40% of patients on father's side, in 37% - on mother's side, in 23% of patients PP was diagnosed in siblings. The fullexome sequencing was conducted to 21 patients: in 61,9% of cases (95% CI [40;79]) nucleotide variants were identified   in genes, associated with gonadotropin-dependent precocious puberty. MKRN3 gene defect was detected in most cases (77% cases (95% CI [49; 92]), which consistent with international data on its highest prevalence in the monogenic forms of PP. In 23% of cases (95% CI [7; 50]) nucleotide variants were identified in other candidate genes associated with neuroontogenesis and neuroendocrine regulation mechanisms of hypothalamic-pituitary axis.

CONCLUSION

Our study confirms that detailed family history data in children with PP provides a rational approach to molecular-genetic testing. Data of inheritance pattern and clinical manifestations will simplify the diagnosis of hereditary forms of disease and enhance genetic counselling of families, followed by timely examination and administration of pathogenetic therapy.

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.

Applying precision medicine to the diagnosis and management of endocrine disorders

Precision medicine employs digital tools and knowledge of a patient's genetic makeup, environment and lifestyle to improve diagnostic accuracy and to develop individualised treatment and prevention strategies. Precision medicine has improved management in a number of disease areas, most notably in oncology, and it has the potential to positively impact others, including endocrine disorders. The accuracy of diagnosis in young patients with growth disorders can be improved by using biomarkers. Insulin-like growth factor I (IGF-I) is the most widely accepted biomarker of growth hormone secretion, but its predictive value for recombinant human growth hormone treatment response is modest and various factors can affect the accuracy of IGF-I measurements. These factors need to be taken into account when considering IGF-I as a component of precision medicine in the management of growth hormone deficiency. The use of genetic analyses can assist with diagnosis by confirming the aetiology, facilitate treatment decisions, guide counselling and allow prompt intervention in children with pubertal disorders, such as central precocious puberty and testotoxicosis. Precision medicine has also proven useful during the transition of young people with endocrine disorders from paediatric to adult services when patients are at heightened risk of dropping out from medical care. An understanding of the likelihood of ongoing GH deficiency, using tools such as MRI, detailed patient history and IGF-I levels, can assist in determining the need for continued recombinant human growth hormone treatment during the process of transitional care.

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.

Genetics of pubertal timing

Puberty marks the end of childhood and is a period when individuals undergo physiological and psychological changes to achieve sexual maturation and fertility. The onset of puberty is first detected as an increase in pulsatile secretion of gonadotropin-releasing hormone (GnRH). Pubertal onset is regulated by genetic, nutritional, environmental, and socio-economic factors. Disturbances affecting pubertal timing result in adverse health conditions later in life. Human genetic studies show that around 50-80% of the variation in pubertal onset is genetically determined. The genetic control of pubertal timing has been a field of active investigation in attempt to better understand the neuroendocrine control of this relevant period of life. Large populational studies and patient cohort-based studies have provided insights into the genetic regulation of pubertal onset. In this review, we discuss these discoveries and discuss potential mechanisms for how implicated genes may affect pubertal timing.

An Approach to the Evaluation and Management of the Obese Child With Early Puberty

With the declining age at onset of puberty and increasing prevalence of childhood obesity, early breast development in young obese girls has become a more frequent occurrence. Here, we examine available literature to answer a series of questions regarding how obesity impacts the evaluation and management of precocious puberty. We focus on girls as the literature is more robust, but include boys where literature permits. Suggestions include: (1) Age cutoffs for evaluation of precocious puberty should not differ substantially from those used for nonobese children. Obese girls with confirmed thelarche should be evaluated for gonadotropin-dependent, central precocious puberty (CPP) to determine if further investigation or treatment is warranted. (2) Basal luteinizing hormone (LH) levels remain a recommended first-line test. However, if stimulation testing is utilized, there is a theoretical possibility that the lower peak LH responses seen in obesity could lead to a false negative result. (3) Advanced bone age (BA) is common among obese girls even without early puberty; hence its diagnostic utility is limited. (4) Obesity does not eliminate the need for magnetic resonance imaging in girls with true CPP. Age and clinical features should determine who warrants neuroimaging. (5) BA can be used to predict adult height in obese girls with CPP to inform counseling around treatment. (6) Use of gonadotropin-releasing hormone analogues (GnRHa) leads to increased adult height in obese girls. (7) Obesity should not limit GnRHa use as these agents do not worsen weight status in obese girls with CPP.

Rare mutation in MKRN3 in two twin sisters with central precocious puberty: Two case reports

BACKGROUND

Caused by premature activation of the hypothalamic-pituitary-gonadal axis, there is increasing incidence of central precocious puberty (CPP), especially in girls. Makorin ring finger protein 3 (MKRN3), a maternal imprinted gene with a highly conserved sequence, is the most common genetic etiology associated with CPP. Approximately 50 different mutations in MKRN3 have been found in CPP.

CASE SUMMARY

This case report involves identical twin sisters presenting with premature thelarche at the age of 6 years. The left hand bone age of both patients revealed advanced age (9 years). Pelvic B ultrasound indicated enlargement of the ovaries. Luteinizing hormone (LH) releasing hormone testing confirmed CPP. Whole-exome sequencing detected the c.841C>T mutation in MKRN3, leading to a single base substitution, in the twins. This mutation was inherited from the father and paternal grandmother. After 3 mo of treatment with a gonadotropin-releasing hormone analog, levels of LH, follicle-stimulating hormone, and estradiol in the proband’s sister returned to normal levels.

CONCLUSION

Here, we report a rare mutation (c.841C>T) in MKRN3 in identical twin sisters with CPP.

Use of gonadotropin-releasing hormone analogs in children

PURPOSE OF REVIEW

In this review, we outline the usage and formulations of gonadotropin-releasing hormone analogs (GnRHas) in central precocious puberty (CPP), short stature, and gender diverse individuals, as well as adverse effects, long-term outcomes, and monitoring of therapy. There is a particular focus on citing references published within the last 24 months.

RECENT FINDINGS

Long-acting formulations of GnRHa now include Federal Drug Administration approval for subcutaneous injections. Significant adverse events continue to be rarely reported; extremely rare events include arterial hypertension and pseudotumor cerebri. There continue to be no significant long-term consequences including the impact upon body mass index and bone mineral density, which appear to be transient. GnRHas have been used in differences of sexual development (DSD) and increasingly in the treatment of adolescent transgender individuals.

SUMMARY

GnRHas remain as the only fully efficacious therapy for CPP and effectively suppress pubertal hormones in other situations. The use of GnRHa therapy in gender incongruent individuals has proven beneficial and has become a standard of care, whereas use in those with DSDs should still be considered experimental.

VIDEO ABSTRACT

http://links.lww.com/MOP/A62.

Familial central precocious puberty: two novel MKRN3 mutations

BACKGROUND

Paternally inherited loss-of-function mutations in MKRN3 underlie central precocious puberty (CPP). We describe clinical and genetic features of CPP patients with paternally inherited MKRN3 mutations in two independent families.

METHODS

The single coding exon of MKRN3 was analyzed in three patients with CPP and their family members, followed by segregation analyses. Additionally, we report the patients' responses to GnRH analog treatment.

RESULTS

A paternally inherited novel heterozygous c.939C>G, p.(Ile313Met) missense mutation affecting the RING finger domain of MKRN3 was found in a Finnish girl with CPP (age at presentation 6 years). Two Polish siblings (a girl presenting with B2 at the age of 4 years and a boy with adult size testes at the age of 9 years) had inherited a novel heterozygous MKRN3 mutation c.1237_1252delGGAGACACATGCTTTT p.(Gly413Thrfs*63) from their father. The girls were treated with GnRH analogs, which exhibited suppression of the hypothalamic-pituitary-gonadal axis. In contrast, the male patient was not treated, yet he reached his target height.

CONCLUSIONS

We describe two novel MKRN3 mutations in three CPP patients. The first long-term data on a boy with CPP due to an MKRN3 mutation questions the role of GnRH analog treatment in augmenting adult height in males with this condition.

IMPACT

We describe the genetic cause for central precocious puberty (CPP) in two families. This report adds two novel MKRN3 mutations to the existing literature. One of the mutations, p.(Ile313Met) affects the RING finger domain of MKRN3, which has been shown to be important for repressing the promoter activity of KISS1 and TAC3. We describe the first long-term observation of a male patient with CPP due to a paternally inherited MKRN3 loss-of-function mutation. Without GnRH analog treatment, he achieved an adult height that was in accordance with his mid-parental target height.

[Clinical and molecular genetic features of 3 family cases of the central precocious puberty, due to MKRN3 gene defects]

Gonadotropin-dependent precocious puberty (central) is a condition resulting from the early (up to 8 years in girls and 9 years in boys) reactivation of the hypothalamic-pituitary-gonadal axis. An increase in the secretion of sex steroids by the gonads in this form is a consequence of the stimulation of the sex glands by gonadotropic hormones of the pituitary gland. In the absence of central nervous system abnormalities, CPP is classified as idiopathic and as familial in some cases, emphasizing the genetic origin of this disorder. Loss-of-function mutations in Makorin Ring Finger Protein 3 (MKRN3) are the most common identified genetic cause of central precocious puberty compared to sporadic cases. In the present study we performed the first descrition of 3 family cases of central precocious puberty duo to novel MKRN3 gene mutation detected by NGS in the Russian Federation.

Genotype-Phenotype Correlations in Central Precocious Puberty Caused by MKRN3 Mutations

CONTEXT

Loss-of-function mutations of makorin RING finger protein 3 (MKRN3) are the most common monogenic cause of familial central precocious puberty (CPP).

OBJECTIVE

To describe the clinical and hormonal features of a large cohort of patients with CPP due to MKRN3 mutations and compare the characteristics of different types of genetic defects.

METHODS

Multiethnic cohort of 716 patients with familial or idiopathic CPP screened for MKRN3 mutations using Sanger sequencing. A group of 156 Brazilian girls with idiopathic CPP (ICPP) was used as control group.

RESULTS

Seventy-one patients (45 girls and 26 boys from 36 families) had 18 different loss-of-function MKRN3 mutations. Eight mutations were classified as severe (70% of patients). Among the 71 patients, first pubertal signs occurred at 6.2 ± 1.2 years in girls and 7.1 ± 1.5 years in boys. Girls with MKRN3 mutations had a shorter delay between puberty onset and first evaluation and higher follicle-stimulating hormone levels than ICPP. Patients with severe MKRN3 mutations had a greater bone age advancement than patients with missense mutations (2.3 ± 1.6 vs 1.6 ± 1.4 years, P = .048), and had higher basal luteinizing hormone levels (2.2 ± 1.8 vs 1.1 ± 1.1 UI/L, P = .018) at the time of presentation. Computational protein modeling revealed that 60% of the missense mutations were predicted to cause protein destabilization.

CONCLUSION

Inherited premature activation of the reproductive axis caused by loss-of-function mutations of MKRN3 is clinically indistinct from ICPP. However, the type of genetic defect may affect bone age maturation and gonadotropin levels.

Programmed death protein 1 is essential for maintaining the anti-inflammatory function of infiltrating regulatory T cells in a murine spinal cord injury model

Excessive neuroinflammation exacerbates neuronal impairment after spinal cord injury (SCI). Thymic regulatory T cells (Tregs), macrophages, and microglia play significant roles in the process of post-SCI neuroinflammation. However, the mechanisms by which these cells were modulated in the injured spinal cord remain unclear. In the current research, we applied a murine SCI model to demonstrate the upregulation of programmed death protein 1(PD-1) in infiltrating Tregs and significant expression of programmed death-ligand 1 (PD-L1) on post-SCI macrophages/microglia. Furthermore, through using an inducible shRNA lentivirus system, we showed that Treg-specific PD-1 knockdown impairs the anti-inflammatory function of infiltrating Tregs. PD-1 is crucial for the maintenance of Treg identity and function under the influence of pro-inflammatory macrophages/microglia, and PD-1-deficient Tregs are less competent to inhibit pro-inflammatory macrophages/microglia. Besides, in a murine SCI model using T-and-B-cell-deficient Rag1^-/- mice, Treg-specific PD-1 knockdown impairs Treg-mediated neuroprotection in vivo, as evidenced by enlarged lesion area. Taken together, our study revealed that PD-1, which is upregulated on infiltrating Tregs in the subacute phase of SCI, is essential for Tregs to maintain Foxp3 expression and anti-inflammatory activity to counteract the effect of pro-inflammatory macrophages and microglia. Novel therapies targeting Treg PD-1 might benefit SCI treatment.

Makorin RING finger protein 3 and central precocious puberty

Makorin RING finger protein 3 (MKRN3) is a key inhibitor of the hypothalamic-pituitary-gonadal axis. Loss-of-function mutations in MKRN3 cause familial and sporadic central precocious puberty (CPP), while polymorphisms are associated with age at menarche. To date, 115 patients with CPP carrying MKRN3 mutations have been described, harboring 48 different genetic variants. The prevalence of MKRN3 mutations in genetically screened populations with CPP is estimated at 9.0%. Girls are more commonly and more seriously affected than boys. MKRN3 is expressed in humans and rodents in the central nervous system. Circulating levels in humans and hypothalamic expression in rodents decrease during pubertal progression. Although some MKRN3 regulators have been identified, the precise mechanism by which MKRN3 inhibits the hypothalamic-pituitary-gonadal axis remains elusive. The role of makorins in developmental physiology and organ differentiation and the role of maternal imprinting are discussed herein.