What controls the timing of puberty? An update on progress from genetic investigation

A comprehensive meta-analysis to identify susceptibility genetic variants for precocious puberty

PURPOSE

Currently, several genetic variants in ERα gene (rs2234693 and rs9340799), ERβ gene (rs1256049 and rs4986938), KISS1 gene (rs4889, rs1132506 and rs5780218), LIN28B gene (rs314263, rs314276 and rs314280), and MKRN3 gene (rs2239669) have been repeatedly explored for their contribution to precocious puberty (PP) susceptibility. However, the results remain conflicting rather than conclusive. We here performed a meta-analysis to identify the real susceptibility genetic variants for PP.

METHODS

After screening by inclusion criteria, 20 related studies were finally included in this meta-analysis. The odds ratios and 95% confidence intervals were calculated to assess the strength of association. Sensitive analysis, publication bias, and trial sequential analysis (TSA) were performed to evaluate the stability and reliability of results.

RESULTS

Rs2234693, rs9340799, and rs1256049 were significantly associated with PP susceptibility (p < 0.0084). Stratified analysis according to ethnicity showed that rs2234693 and rs9340799 were significantly associated with PP susceptibility in Asian and Chinese populations. Stratified analysis according to PP subtype showed that rs2234693 and rs9340799 were significantly associated with idiopathic central PP susceptibility in Asian and Chinese populations (p < 0.0084). The results of publication bias, sensitivity analysis, and TSA provided solid evidence for the association between these three variants and PP susceptibility.

CONCLUSIONS

Rs2234693 and rs9340799 in ERα gene and rs1256049 in ERβ gene may serve as susceptive factors for PP development. The present finding should be confirmed in replication studies and reinforced in functional studies, which will ultimately improve the feasibility of the application of these three PP-susceptible loci in clinical practice.

Impact of Spirometry Race-Correction on Preadolescent Black and White Children

BACKGROUND

Race-correction for Black patients is standard practice in spirometry testing. History suggests that these corrections are at least partially a result of racist assumptions regarding lung anatomy among Black individuals, which can potentially lead to less frequent diagnoses of pulmonary diseases in this population.

OBJECTIVE

To evaluate the impact of race-correction in spirometry testing among Black and White preadolescents, and examine the frequency of current asthma symptoms in Black children who were differentially classified depending on whether race-corrected or race-uncorrected reference equations were deployed.

METHODS

Data from Black and White children who completed a clinical examination at age 10 years from a Detroit-based unselected birth cohort were analyzed. Global Lung Initiative 2012 reference equations were applied to spirometry data using both race-corrected and race-uncorrected (ie, population-average) equations. Abnormal results were defined as values less than the fifth percentile. Asthma symptoms were assessed concurrently using the International Study of Asthma and Allergies in Childhood questionnaire, while asthma control was assessed using the Asthma Control Test.

RESULTS

The impact of race-correction on forced expiratory volume in 1 second (FEV1)/forced vital capacity ratio was minimal, but abnormal classification of FEV1 results more than doubled among Black children when race-uncorrected equations were used (7% vs 18.1%) and were almost 8 times greater based on forced vital capacity classification (1.5% vs 11.4%). More than half of Black children differentially classified on FEV1 (whose FEV1 was classified as normal with race-corrected equations but abnormal with race-uncorrected equations) experienced asthma symptoms in the past 12 months (52.6%), which was significantly higher than the percentage of Black children consistently classified as normal (35.5%, P = .049), but similar to that of Black children consistently classified as abnormal using both race-corrected and race-uncorrected equations (62.5%, P = .60). Asthma Control Test scores were not different based on classification.

CONCLUSIONS

Race-correction had an extensive impact on spirometry classification in Black children, and differentially classified children had a higher rate of asthma symptoms than children consistently classified as normal. Spirometry reference equations should be reevaluated to be aligned with current scientific perspectives on the use of race in medicine.

Genome-wide association study of age at menarche in the Taiwan Biobank suggests NOL4 as a novel associated gene

Sexual maturation is a complex physiological process that involves multiple variables, such as genetic and environmental factors. Among females, age at menarche (AM) is a critical milestone for sexual maturation. This study aimed to identify genetic markers of AM using nationwide population cohort data in Taiwan. Females with self-reported AM between 10 and 16 years (N = 39,827) were eligible for the final analysis. To identify genetic signals related to AM, we conducted a genome-wide association study using a linear regression model and split-half meta-analysis method to verify our findings. The Functional Mapping and Annotation web-based platform was used for positional mapping and gene-based and gene-set analyses. The meta-analysis identified four significant loci, i.e., LIN28B (pooled P = 1.39 × 10^-21), NOL4 (pooled P = 8.94 × 10^-9), GPR45 (pooled P = 4.19 × 10^-11), and LOC105373831 (pooled P = 4.37 × 10^-8), that were associated with AM. MAGMA gene-based analysis revealed that LIN28B (P = 1.13 × 10^-8), NOL4 (P = 2.27 × 10^-7), RXRG (P = 4.34 × 10-⁷), ETV5 (P = 1.75 × 10^-6), and HACE1 (P = 1.82 × 10^-6) were significantly associated with AM, while the gene-set analysis identified a significantly enriched pathway involving mTOR signaling complex (FDR corrected P = 1.28 × 10^-2). The results replicated evidence for several genetic markers associated with AM in the Taiwanese female population. Our analysis identified a novel locus (rs7239368) in NOL4 associated with AM (β = 0.051 ± 0.009 years, pooled P = 8.94 × 10^-9), whereas additional research is needed to validate its molecular role in sexual maturation.

A new DLK1 defect in a family with idiopathic central precocious puberty: elucidation of the male phenotype

PURPOSE

We aimed to investigate a cohort of female and male patients with idiopathic central precocious puberty (CPP), negative for Makorin Ring Finger Protein 3 (MKRN3) defect, by molecular screening for Delta-like 1 homolog (DLK1) defects. DLK1 is an imprinted gene, whose mutations have been described as a rare cause of CPP in girls and adult women with precocious menarche, obesity and metabolic derangement.

METHODS

We enrolled 14 girls with familial CPP and 13 boys with familial or sporadic CPP from multiple academic hospital centers. Gene sequencing of DLK1 gene was performed. Circulating levels of DLK1 were measured and clinical and biochemical characteristics were described in those with DLK1 defects.

RESULTS

A novel heterozygous mutation in DLK1, c.288_289insC (p.Cys97Leufs*16), was identified in a male proband, his sister and their father. Age at onset of puberty was in line with previous reports in the girl and 8 years in the boy. The father with untreated CPP showed short stature. No metabolic derangement was present in the father except hypercholesterolemia. Undetectable Dlk1 serum levels indicated the complete lack of protein production in the three affected patients.

CONCLUSION

A DLK1 defect has been identified for the first time in a boy, underscoring the importance of genetic testing in males with idiopathic or sporadic CPP. The short stature reported by his untreated father suggests the need for timely diagnosis and treatment of subjects with DLK1 defects.

Hypogonadism in male and female: which is the best treatment?

BACKGROUND

Subjects with hypo-or hypergonadotropic hypogonadism need hormone replacement therapy (HRT) to initiate puberty and maintain it with a normal hormonal status. While general recommendations for the management of HRT in adults have been published, no systematic suggestions focused on adolescents and young adults. The focus of this review is the HRT in males and females with hypogonadism, from puberty to late reproductive age, covering the different management options, encompassing sex steroid or gonadotropin therapy, with discussion of benefits, limitations and specific considerations of the different treatments.

METHODS

We conducted an extensive search in the 3 major scientific databases (PubMed, EMBASE and Google Scholar) using the keywords "hormonal replacement therapy", "hypogonadism", "bone mineral density", "estradiol/testosterone", "puberty induction", "delayed puberty". Case-control studies, case series, reviews and meta-analysis published in English from 1990 to date were included.

RESULTS

By considering the available opportunities for fertility induction and preservation, we hereby present the proposals of practical schemes to induce puberty, and a decisional algorithm to approach HRT in post-pubertal adolescents.

CONCLUSIONS

A condition of hypogonadism can underlie different etiologies involving the hypothalamic-pituitary-gonadal axis at different levels. Since the long-terms effects of hypogonadism may vary and include not only physical outcomes related to sex hormone deficiencies, but also psychological problems and implications on fertility, the initiation, maintenance and consolidation of puberty with different pharmaceutical options is of utmost importance and beside pubertal development, optimal uterine and testicular growth and adequate bone health should consider also the psychosocial wellbeing and the potential fertility.

[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.

Delayed and Precocious Puberty: Genetic Underpinnings and Treatments

Delayed puberty may signify a common variation of normal development, or indicate the presence of a pathologic process. Constitutional delay of growth and puberty is a strongly familial type of developmental pattern and accounts for the vast majority of children who are "late bloomers." Individuals with sex chromosomal abnormalities frequently have hypergonadotropic hypogonadism. There are currently 4 known monogenic causes of central precocious puberty. The primary treatment goal in children with hypogonadism is to mimic normal pubertal progression, while the primary aims for the management of precocious puberty are preservation of height potential and prevention of further pubertal development.

MKRN3 inhibits the reproductive axis through actions in kisspeptin-expressing neurons

The identification of loss-of-function mutations in MKRN3 in patients with central precocious puberty in association with the decrease in MKRN3 expression in the medial basal hypothalamus of mice before the initiation of reproductive maturation suggests that MKRN3 is acting as a brake on gonadotropin-releasing hormone (GnRH) secretion during childhood. In the current study, we investigated the mechanism by which MKRN3 prevents premature manifestation of the pubertal process. We showed that, as in mice, MKRN3 expression is high in the hypothalamus of rats and nonhuman primates early in life, decreases as puberty approaches, and is independent of sex steroid hormones. We demonstrated that Mkrn3 is expressed in Kiss1 neurons of the mouse hypothalamic arcuate nucleus and that MKRN3 repressed promoter activity of human KISS1 and TAC3, 2 key stimulators of GnRH secretion. We further showed that MKRN3 has ubiquitinase activity, that this activity is reduced by MKRN3 mutations affecting the RING finger domain, and that these mutations compromised the ability of MKRN3 to repress KISS1 and TAC3 promoter activity. These results indicate that MKRN3 acts to prevent puberty initiation, at least in part, by repressing KISS1 and TAC3 transcription and that this action may involve an MKRN3-directed ubiquitination-mediated mechanism.

MKRN3 regulates the epigenetic switch of mammalian puberty via ubiquitination of MBD3

Central precocious puberty (CPP) refers to a human syndrome of early puberty initiation with characteristic increase in hypothalamic production and release of gonadotropin-releasing hormone (GnRH). Previously, loss-of-function mutations in human MKRN3, encoding a putative E3 ubiquitin ligase, were found to contribute to about 30% of cases of familial CPP. MKRN3 was thereby suggested to serve as a ‘brake’ of mammalian puberty onset, but the underlying mechanisms remain as yet unknown. Here, we report that genetic ablation of Mkrn3 did accelerate mouse puberty onset with increased production of hypothalamic GnRH1. MKRN3 interacts with and ubiquitinates MBD3, which epigenetically silences GNRH1 through disrupting the MBD3 binding to the GNRH1 promoter and recruitment of DNA demethylase TET2. Our findings have thus delineated a molecular mechanism through which the MKRN3–MBD3 axis controls the epigenetic switch in the onset of mammalian puberty.

Neuroendocrine mechanisms of reproduction

The neuroendocrinology of reproduction focuses on the neuromodulation of gonadotropin-releasing hormone (GnRH), the ontogeny of the hypothalamic-pituitary-gonadal axis, and common reproductive events and conditions, namely, puberty, the menstrual cycle, and disorders of reproductive function. The core concept underpinning the neuroendocrinology of reproduction is neuroregulation of hypothalamic GnRH drive. In both men and women, reproductive function requires that GnRH input elicit appropriate secretion of follicle-stimulating hormone and luteinizing hormone from the anterior pituitary and that the gonads respond to such input appropriately. Moreover, insufficient GnRH drive causes hypothalamic hypogonadism and secondary insufficiency of gonadal sex steroid hormone synthesis and release in both sexes. Alterations in GnRH drive also reflect gonadal conditions such as dysgenesis, hyperandrogenism, gonadotropin mutations, and aging and loss or absence of oocytes or Sertoli cells. The most common cause of insufficient GnRH drive is functional, that is, due to the endocrine effects of psychologic or behavioral variables. Rarely does reduced GnRH drive reflect organic or congenital causes such as developmental defects, brain tumors, or celiac disease. Despite a common neuropathogenesis the heterogeneity of behavioral variables associated with reduced GnRH drive has resulted in a variety of names, including functional hypothalamic amenorrhea, stress-induced anovulation, and psychogenic amenorrhea.

p53 Mediates GnRH Secretion via Lin28/let-7 System in GT1-7 Cells

STUDY OBJECTIVE

The well-known tumor suppressor transcriptional factor p53 has been proposed to be one of the central hubs of a functionally related and hierarchically arranged gene network coordinating pubertal timing. Our previous studies revealed that p53 is involved in the metabolic control of puberty. The current study aimed to investigate the underlying signaling pathway, through which p53 mediated the metabolic control of puberty.

DESIGN SETTING PARTICIPANTS INTERVENTIONS AND MAIN OUTCOME MEASURES

We engineered the expression of p53 and/or Lin28a in GT1-7 cells to investigate the interaction between p53 and Lin28/let-7 system, and their impact on GnRH secretion.

RESULTS

Overexpression of p53 stimulated, while inhibition of p53 by pifithrin-α significantly suppressed the GnRH secretion and GPR54 expression levels in response to kisspeptin stimulation in GT1-7 cells. Furthermore, overexpressed p53 suppressed Lin28a and c-Myc expression levels and increased let-7 expression levels in GT1-7 cell lines. On the other hand, inhibition of p53 by pifithrin-α upregulated Lin28a and c-Myc levels and downregulated let-7 expression levels. Moreover, Lin28a overexpression counteracted the effect of p53 overexpression in p53 and Lin28a co-overexpression cells, whose GnRH secretion and GPR54 expression levels were not different from controls. Meanwhile, Lin28a suppression counteracted the effect of pifithrin-α, and the GnRH secretion and GPR54 expression levels are not different from controls in p53 and Lin28a co-suppression cells.

CONCLUSION

These data suggest that p53 is a central mediator of GnRH secretion in hypothalamus, and this effect is at least partly through the Lin28/let-7 pathway.

LIN28B affects gene expression at the hypothalamic-pituitary axis and serum testosterone levels

Genome-wide association studies (GWAS) have recurrently associated sequence variation nearby LIN28B with pubertal timing, growth and disease. However, the biology linking LIN28B with these traits is still poorly understood. With our study, we sought to elucidate the mechanisms behind the LIN28B associations, with a special focus on studying LIN28B function at the hypothalamic-pituitary (HP) axis that is ultimately responsible for pubertal onset. Using CRISPR-Cas9 technology, we first generated lin28b knockout (KO) zebrafish. Compared to controls, the lin28b KO fish showed both accelerated growth tempo, reduced adult size and increased expression of mitochondrial genes during larval development. Importantly, data from the knockout zebrafish models and adult humans imply that LIN28B expression has potential to affect gene expression in the HP axis. Specifically, our results suggest that LIN28B expression correlates positively with the expression of ESR1 in the hypothalamus and POMC in the pituitary. Moreover, we show how the pubertal timing advancing allele (T) for rs7759938 at the LIN28B locus associates with higher testosterone levels in the UK Biobank data. Overall, we provide novel evidence that LIN28B contributes to the regulation of sex hormone pathways, which might help explain why the gene associates with several distinct traits.

Secular trends in weight, stature, and body mass index in Nova Scotia, Canada

OBJECTIVES

The present study aims to investigate the secular trends of weight, stature, and BMI values in a Nova Scotian sample from 1946 to 1999, with particular focus on how these trends may relate to nutrition and the evolving obesity epidemic.

METHODS

Data were collected from investigative (autopsy) records of 1645 individuals (1287 males, 358 females) of European descent at the Nova Scotia Medical Examiner Service. Secular trends were evaluated by linear regression of weight, stature, and BMI with respect to the year of birth. Further analysis of this sample was based on five time periods (birth cohorts), in order to determine whether dramatic shifts in diet and nutrition affected weight, stature, and BMI.

RESULTS

Overall, the results of this study demonstrate positive secular trends in weight, stature, and BMI from 1946 to 1999 in the Nova Scotian sample. Subsequent analysis among different time periods shows a secular increase in the weight of Nova Scotian males from 1946 to 1979, and a subsequent decrease in weight in after 1980. For Nova Scotian females, the results show a secular increase in weight from 1946 to 1989, and a subsequent decrease in weight after 1990. Such secular increases in weight coincide with the global nutrition transition, while recent decreasing median weight values may reflect economic growth and urbanization in Nova Scotia.

CONCLUSIONS

Overall, the results of the present study indicate that temporal trends in nutrition may have contributed to positive secular changes in weight, stature, and BMI in Nova Scotia, Canada between 1946 and 1999.

Genome-wide DNA methylation analysis of pituitaries during the initiation of puberty in gilts

It has been widely recognized that the early or delayed puberty appears to display harmful effects on adult health outcomes. During the timing of puberty, pituitaries responds to the hypothalamus and then introduce the following response of ovaries in hypothalamic-pituitary-gonadal axis. DNA methylation has been recently suggested to regulate the onset of puberty in female mammals. However, to date, the changes of DNA methylation in pituitaries have not been investigated during pubertal transition. In this study, using gilts as the pubertal model, the genome-scale DNA methylation of pituitaries was profiled and compared across Pre-, In- and Post-puberty by using the reduced representation bisulfite sequencing. We found that average methylation levels of each genomic feature in Post- were lower than Pre- and In-pubertal stage in CpG context, but they were higher in In- than that in Pre- and Post-pubertal stage in CpH (where H = A, T, or C) context. The methylation patterns of CpHs were more dynamic than that of CpGs at the location of high CpG content, low CpG content promoter genes, and differently genomic CGIs. Furthermore, the differently genomic CGIs were likely to show in a similar manner in CpG context but display in a stage-specific manner in the CpH context across the Pre-, In- and Post-pubertal stage. Among these pubertal stages, 5 kb upstream regions of the transcription start sites were protected from both CpG and CpH methylation changes. 12.65% of detected CpGs were identified as the differentially methylated CpGs, regarding 4301 genes which were involved in the fundamental functions of pituitaries. 0.35% of detected CpHs were identified as differentially methylated CpHs, regarding 3691 genes which were involved in the biological functions of releasing gonadotropin hormones. These observations and analyses would provide valuable insights into epigenetic mechanism of the initiation of puberty in pituitary level.

Morning basal luteinizing hormone, a good screening tool for diagnosing central precocious puberty

PURPOSE

The standard method used to diagnose central precocious puberty (CPP) is the gonadotropin releasing hormone stimulation test (GnRHST). However, this test is inconvenient for children because it is time-consuming and requires multiple samples. This study aimed to determine the reliability of morning unstimulated luteinizing hormone (mLH) level when screening for CPP, with an emphasis on the influence of diurnal variation.

METHODS

This study included 160 girls with signs of early puberty (SMR 2) under 8 years of age. They were classified as CPP or non-CPP based on their standard GnRHST. The auxological, biochemical, and hormonal characteristics of subjects were retrospectively evaluated. The prognostic value of single morning unstimulated gonadotropin level was examined for use in CPP screening.

RESULTS

Of 160 patients, 121 (75.6%) presented with CPP, and 39 (24.4%) were determined to be prepubertal. The mLH/mFSH (morning unstimulated follicular stimulating hormone) ratio showed significant differences between the 2 groups (P&lt;0.001). The mLH was correlated with GnRHST variables (r=0.532, P&lt;0.001). The mLH cutoff point when screening for CPP was 0.22 IU/L, which had sensitivity and specificity of 69.4% and 82.1%, respectively. In regression analysis, bone age (BA) (odds ratio [OR], 1.018; 95% confidence interval [CI], 0.967-1.071; P=0.506) and body mass index (BMI) (OR, 0.874; 95% CI, 0.583-1.310; P=0.515) were not significant predictors. The mLH≥0.22 IU/L group (OR, 9.596; 95% CI, 3.853-23.900; P&lt;0.001) was highly suggestive of CPP.

CONCLUSION

In this study, single morning unstimulated luteinizing hormone had clinical efficacy for CPP screening, but BA advanced over chronological age and BMI was not useful for CPP screening.

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.

Precocious and Early Central Puberty in Children With Pre-existing Medical Conditions: A Single Center Study

Background: Precocious and early puberty are reported findings in children with pre-existing medical conditions including certain syndromes. Series pertaining to such situations are limited. Methods: A retrospective, single-center study was conducted on children with central precocious puberty (onset before the age of 8 years in girls and 9 years in boys) or early puberty (onset between 8 and 9 years in girls and between 9 and 10.5 years in boys) diagnosed on the background of a known pre-existing chronic significant medical condition. Patients with a CNS tumor and those exposed to cranial irradiation were excluded. Results: Precocious puberty was diagnosed in 13 patients and early puberty in 12. Mean age at onset of puberty was 6.65 ± 2.3 years in girls (n = 15) and 9.4 ± 0.84 years in boys (n = 10). The most common disorders were psychomotor delay (n = 12), psychiatric disorders (n = 7) and/or epilepsy (n = 5). Precocious or early puberty was among the symptoms experienced by patients with a variety of syndromes including lipofuscinosis (2 siblings), Dravet syndrome and Silver-Russel syndrome. Pituitary stalk interruption with agenesis of olfactory bulbs and optic nerve atrophy was found on imaging in one patient who presented with blindness, epilepsy, and autism spectrum disorder. The other diseases associated with precocious or early puberty are adrenocorticotropic deficiency, dyspraxia and bone abnormalities, glomerulopathy with complete renal failure, and repeated intra-fetal deaths in the mother. Karyotype analysis revealed chromosomal duplication (chromosome 15 in 2 cases; chromosomes 17 and 11 in one case each) in 4 of 8 patients evaluated. Conclusions: Data from patients with complex disease who experience precocious or early puberty may provide clues regarding the genetic determinants of pubertal development.

Makorin 1 Regulates Developmental Timing in Drosophila

The central mechanisms coordinating growth and sexual maturation are well conserved across invertebrates and vertebrates. Although mutations in the gene encoding makorin RING finger protein 3 (mkrn3 ) are associated with central precocious puberty in humans, a causal relationship has not been elucidated. Here, we examined the role of mkrn1, a Drosophila ortholog of mammalian makorin genes, in the regulation of developmental timing. Loss of MKRN1 in mkrn1 exS prolonged the 3rd instar stage and delayed the onset of pupariation, resulting in bigger size pupae. MKRN1 was expressed in the prothoracic gland, where the steroid hormone ecdysone is produced. Furthermore, mkrn1 exS larvae exhibited reduced mRNA levels of phantom, which encodes ecdysone-synthesizing enzyme and E74, which is a downstream target of ecdysone. Collectively, these results indicate that MKRN1 fine-tunes developmental timing and sexual maturation by affecting ecdysone synthesis in Drosophila. Moreover, our study supports the notion that malfunction of makorin gene family member, mkrn3 dysregulates the timing of puberty in mammals.

Genes underlying delayed puberty

The genetic control of pubertal timing has been a field of active investigation for the last decade, but remains a fascinating and mysterious conundrum. Self-limited delayed puberty (DP), also known as constitutional delay of growth and puberty, represents the extreme end of normal pubertal timing, and is the commonest cause of DP in both boys and girls. Familial self-limited DP has a clear genetic basis. It is a highly heritable condition, which often segregates in an autosomal dominant pattern (with or without complete penetrance) in the majority of families. However, the underlying neuroendocrine pathophysiology and genetic regulation has been largely unknown. Very recently novel gene discoveries from next generation sequencing studies have provided insights into the genetic mutations that lead to familial DP. Further understanding has come from sequencing genes known to cause GnRH deficiency, next generation sequencing studies in patients with early puberty, and from large-scale genome wide association studies in the general population. Results of these studies suggest that the genetic basis of DP is likely to be highly heterogeneous. Abnormalities of GnRH neuronal development, function, and its downstream pathways, metabolic and energy homeostatic derangements, and transcriptional regulation of the hypothalamic-pituitary-gonadal axis may all lead to DP. This variety of different pathogenic mechanisms affecting the release of the puberty 'brake' may take place in several age windows between fetal life and puberty.

Management of hypogonadism from birth to adolescence

Management of patients with hypogonadism is dependent on the underlying cause. Whilst functional hypogonadism presenting as delayed puberty in adolescence is relatively common, permanent hypogonadism presenting in infancy or adolescence is unusual. The main differential diagnoses of delayed puberty include self-limited delayed puberty (DP), idiopathic hypogonadotropic hypogonadism (IHH) and hypergonadotropic hypogonadism. Treatment of self-limited DP involves expectant observation or short courses of low dose sex steroid supplementation. More complex and involved management is required in permanent hypogonadism to achieve both development of secondary sexual characteristics and to maximize the potential for fertility. This review will cover the options for management involving sex steroid or gonadotropin therapy, with discussion of benefits, limitations and specific considerations of the different treatment options.

Two Frameshift Mutations in MKRN3 in Turkish Patients with Familial Central Precocious Puberty

BACKGROUND

Little is known about the genetic causes responsible for idiopathic central precocious puberty (iCPP). More recently, described loss-of-function mutations in the makorin ring finger protein 3 (MKRN3) gene have been demonstrated to be involved in the pathogenesis of familial iCPP.

AIM

The objective of this study was to investigate the potential role of MKRN3 in patients with familial iCPP.

METHODS

We investigated potential sequence variations in the maternal imprinted MKRN3 gene using Next Generation Sequencing (NGS) analysis in 31 participants from 2 families (6 participants were diagnosed with familial iCPP on the basis of clinical and hormonal findings). Six patients diagnosed with familial iCPP and their unaffected first- and second-degree relatives, including their grandparents, were screened for MKRN3 gene variants.

RESULTS

Two heterozygous frameshift mutations (c.441_441delG, p.H148Tfs*23 and c803_803delAT, p.M268Vfs*23) were described in the MKRN3 gene in 2 probands with familial iCPP and in some of their family members. These frameshift mutations create a premature stop codon and result in a truncated protein.

CONCLUSIONS

Our report further expands the MKRN3 gene mutation spectrum in patients with familial iCPP. Screening for potential MKRN3 variants should be performed in patients with familial iCPP as well as in patients with sporadic iCPP.

Congenital hypogonadotropic hypogonadism and constitutional delay of growth and puberty have distinct genetic architectures

OBJECTIVE

Congenital hypogonadotropic hypogonadism (CHH) and constitutional delay of growth and puberty (CDGP) represent rare and common forms of GnRH deficiency, respectively. Both CDGP and CHH present with delayed puberty, and the distinction between these two entities during early adolescence is challenging. More than 30 genes have been implicated in CHH, while the genetic basis of CDGP is poorly understood.

DESIGN

We characterized and compared the genetic architectures of CHH and CDGP, to test the hypothesis of a shared genetic basis between these disorders.

METHODS

Exome sequencing data were used to identify rare variants in known genes in CHH (n = 116), CDGP (n = 72) and control cohorts (n = 36 874 ExAC and n = 405 CoLaus).

RESULTS

Mutations in at least one CHH gene were found in 51% of CHH probands, which is significantly higher than in CDGP (7%, P = 7.6 × 10^-11) or controls (18%, P = 5.5 × 10^-12). Similarly, oligogenicity (defined as mutations in more than one gene) was common in CHH patients (15%) relative to CDGP (1.4%, P = 0.002) and controls (2%, P = 6.4 × 10^-7).

CONCLUSIONS

Our data suggest that CDGP and CHH have distinct genetic profiles, and this finding may facilitate the differential diagnosis in patients presenting with delayed puberty.

Contributions of Function-Altering Variants in Genes Implicated in Pubertal Timing and Body Mass for Self-Limited Delayed Puberty

CONTEXT

Self-limited delayed puberty (DP) is often associated with a delay in physical maturation, but although highly heritable the causal genetic factors remain elusive. Genome-wide association studies of the timing of puberty have identified multiple loci for age at menarche in females and voice break in males, particularly in pathways controlling energy balance.

OBJECTIVE/MAIN OUTCOME MEASURES

We sought to assess the contribution of rare variants in such genes to the phenotype of familial DP.

DESIGN/PATIENTS

We performed whole-exome sequencing in 67 pedigrees (125 individuals with DP and 35 unaffected controls) from our unique cohort of familial self-limited DP. Using a whole-exome sequencing filtering pipeline one candidate gene [fat mass and obesity-associated gene (FTO)] was identified. In silico, in vitro, and mouse model studies were performed to investigate the pathogenicity of FTO variants and timing of puberty in FTO+/- mice.

RESULTS

We identified potentially pathogenic, rare variants in genes in linkage disequilibrium with genome-wide association studies of age at menarche loci in 283 genes. Of these, five genes were implicated in the control of body mass. After filtering for segregation with trait, one candidate, FTO, was retained. Two FTO variants, found in 14 affected individuals from three families, were also associated with leanness in these patients with DP. One variant (p.Leu44Val) demonstrated altered demethylation activity of the mutant protein in vitro. Fto+/- mice displayed a significantly delayed timing of pubertal onset (P < 0.05).

CONCLUSIONS

Mutations in genes implicated in body mass and timing of puberty in the general population may contribute to the pathogenesis of self-limited DP.

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.

Makorin ring finger 3 gene analysis in Koreans with familial precocious puberty

BACKGROUND

Precocious puberty is known as an idiopathic, sporadic disease. Recently, specific mutations have been shown to cause familial central precocious puberty (CPP). The makorin ring finger 3 (MKRN3) gene plays a key role in puberty; loss-of-function mutations in the gene trigger familial CPP. To date, most described patients have been Western; few Asians with CPP have been documented.

OBJECTIVE

To identify MKRN3 gene mutations or polymorphisms in Korean patients with familial CPP.

METHODS

26 patients with CPP and their parents (total 13 families) were recruited. We measured endocrine and auxological parameters, and sequenced all MKRN3 exons.

RESULTS

We found no MKRN3 mutations. Two MKRN3 exon polymorphisms were identified. The g.23566445 C/T polymorphism was found in eight families; a novel single nucleotide polymorphism (SNP) g.23567001 A/C was found in one family. These variants are synonymous SNPs; their functional roles remain unknown.

CONCLUSIONS

MKRN3 mutation is uncommon in Korean patients with familial CPP. Ethnic variation in the MKRN3 mutational status is thus evident.

IGSF10 mutations dysregulate gonadotropin-releasing hormone neuronal migration resulting in delayed puberty

Early or late pubertal onset affects up to 5% of adolescents and is associated with adverse health and psychosocial outcomes. Self‐limited delayed puberty (DP) segregates predominantly in an autosomal dominant pattern, but the underlying genetic background is unknown. Using exome and candidate gene sequencing, we have identified rare mutations in IGSF10 in 6 unrelated families, which resulted in intracellular retention with failure in the secretion of mutant proteins. IGSF10 mRNA was strongly expressed in embryonic nasal mesenchyme, during gonadotropin‐releasing hormone (GnRH) neuronal migration to the hypothalamus. IGSF10 knockdown caused a reduced migration of immature GnRH neurons in vitro, and perturbed migration and extension of GnRH neurons in a gnrh3:EGFP zebrafish model. Additionally, loss‐of‐function mutations in IGSF10 were identified in hypothalamic amenorrhea patients. Our evidence strongly suggests that mutations in IGSF10 cause DP in humans, and points to a common genetic basis for conditions of functional hypogonadotropic hypogonadism (HH). While dysregulation of GnRH neuronal migration is known to cause permanent HH, this is the first time that this has been demonstrated as a causal mechanism in DP.‡

An update on the genetic causes of central precocious puberty

Central precocious puberty (CPP) is caused by the premature reactivation of the hypothalamic-pituitary-gonadal axis. Genetic, nutritional, and environmental factors play a crucial role in determining pubertal timing. Recently mutations in kisspeptin (KISS1), kisspeptin receptor (KISS1R), and makorin RING finger protein 3 (MKRN3) genes have been identified as genetic causes of CPP. In particular, the MKRN3 gene is known to affect pubertal initiation. The MKRN3 gene is located on chromosome 15q11-q13 in the Prader-Willi syndrome (PWS) critical region. MKRN3 deficiency, due to a loss of function mutation, leads to the withdrawal of hypothalamic inhibition and prompts pulsatile gonadotropin-releasing hormone secretion, resulting in precocious puberty. The exact functions of these genes associated with CPP are still not well understood. Larger studies are required to discover the mechanisms involved in pubertal development.

In silico analysis of a novel MKRN3 missense mutation in familial central precocious puberty

BACKGROUND

The onset of puberty is influenced by the interplay of stimulating and restraining factors, many of which have a genetic origin. Premature activation of the GnRH secretion in central precocious puberty (CPP) may arise either from gain-of-function mutations of the KISS1 and KISS1R genes or from loss-of-function manner mutations of the MKRN3 gene leading to MKRN3 deficiency.

OBJECTIVE

To explore the genetic causes responsible for CPP and the potential role of the RING finger protein 3 (MKRN3) gene.

DESIGN AND PATIENTS

We investigated potential sequence variations in the intronless MKRN3 gene by Sanger sequencing of the entire 507 amino acid coding region of exon 1 in a family with two affected girls presented with CPP at the age of 6 and 5·7 years, respectively.

RESULTS

A novel heterozygous g.Gly312Asp missense mutation in the MKRN3 gene was identified in these siblings. The imprinted MKRN3 missense mutation was also identified as expected in the unaffected father and followed as expected an imprinted mode of inheritance. In silico analysis of the altered missense variant using the computational algorithms Polyphen2, SIFT and Mutation Taster predicted a damage and pathogenic alteration causing CPP. The pathogenicity of the alteration at the protein level via an in silico structural model is also explored.

CONCLUSION

A novel mutation in the MKRN3 gene in two sisters with CPP was identified, supporting the fundamental role of this gene in the suppression of the hypothalamic GnRH neurons.

A case of familial central precocious puberty caused by a novel mutation in the makorin RING finger protein 3 gene

BACKGROUND

Central precocious puberty (CPP) is often familial but its genetic cause is largely unknown. Very recently, the makorin RING finger protein 3 (MKRN3) gene, located on chromosome 15 in the Prader-Willi syndrome (PWS)-associated region (15q11-q13), has been found mutated in 5 families with familial precocious puberty. The MKRN3 is a maternal imprinted gene and the phenotype is expressed only when the MKRN3 mutations are localized on the allele inherited from the father. The function of this gene is not completely known and the phenotype caused by its defect is not yet fully elucidated. We report a new MKRN3 mutation (Pro160Cysfs*14) causing familial CPP.

CASE PRESENTATION

The index case is a 7 years old girl showing Tanner stage 3 and pubic hair stage 1. Her bone age evaluated by TW2 method was 10.3 years. Her hormonal data confirmed the diagnosis of central precocious puberty. Familial medical history revealed precocious puberty in a cousin on paternal side. Paternal grandmother had menarche at the age of 9 years and 6 months and premature menopause when she was 36 years old. Genetic analysis revealed a new mutation (c477_485del; Pro160Cysfs*14) in the maternally imprinted MKRN3. Puberty onset was at 5 years in the other affected female family member. Precocious puberty was well controlled by pharmacological therapy.

CONCLUSION

We expand the number of the MKRN3 mutations associated with CPP and highlight the importance of an accurate family medical history to disclose the peculiar pattern of inheritance of this gene.

Mutation of kisspeptin 1 gene in children with precocious puberty in isfahan city

BACKGROUND

Considering the role of kisspeptin (KISS) in the process of puberty, this study aimed to determine the mutation of KISS1 gene among a group of patients with idiopathic central precocious puberty (ICPP).

METHODS

In this case control study, a group of children with diagnosed ICPP and a group of healthy children were selected. Genomic DNA was extracted from peripheral blood of selected population. After proving the quality and quantity of extracted DNA samples by nano-drop instrument, PCR was performed using 3 set of primers to amplify all coding exons and flanking intron region of Kiss1 gene.

RESULTS

In this study, 33 patients with idiopathic PP and 30 control age and sex matched children were studied. Genetic analysis indicated that there was not any polymorphism or mutation in studied participants of the control group. Among patients with ICPP, 4 single nucleotide polymorphisms within the promoter and coding regions of KISS1 gene were determined in 9 patients (5 boys and 4 girls). Among them, the c.-148 T > A was novel variant.

CONCLUSIONS

The results of the current study identified one novel polymorphism and three reported polymorphism in KISS gene among patients with ICPP. It is recommended to design further studies for analysis other genes related to ICPP in accordance with more complementary biochemical evaluations is recommended also.

Timing and tempo: Exploring the complex association between pubertal development and depression in African American and European American girls

The relative contribution of pubertal timing and tempo to the development of depression has not been tested in a large, representative sample, nor has the interface among pubertal maturation, depression, and race been tested. Participants were a community-based sample of 2,450 girls from the Pittsburgh Girls Study who were interviewed annually from ages 9 to 17 years. Pubertal timing and tempo were characterized as a unitary construct and also separately for pubic hair and breast development using child and maternal report. Depression symptoms were assessed annually. African American girls had higher depression symptoms and progressed through puberty earlier, but at a slower tempo than European American girls. Girls with earlier timing had higher levels of depression symptoms at age 10 years. Slower tempo was associated with higher depression symptoms at age 10, and faster tempo was associated with increases in depression from ages 10 to 13. As well, race moderated the associations among timing, tempo, and depression symptoms, and the association between race and depression was partially mediated by pubertal timing and tempo. Pubertal timing and tempo and race contribute to the developmental course of depression from early to late adolescence. The pattern of association varies as a function of the developmental window within which depression is assessed. Thus, repeated measures of depression symptoms and puberty across the span of pubertal development are necessary for exploring the relative importance of dimensions of pubertal development to depression etiology.

New causes of central precocious puberty: the role of genetic factors

A pivotal event in the onset of puberty in humans is the reemergence of the pulsatile release of the gonadotropin-releasing hormone (GnRH) from hypothalamic neurons. Pathways governing GnRH ontogeny and physiology have been discovered by studying animal models and humans with reproductive disorders. Recent human studies implicated the activation of kisspeptin and its cognate receptor (KISS1/KISS1R) and the inactivation of MKRN3 in the premature reactivation of GnRH secretion, causing central precocious puberty (CPP). MKRN3, an imprinted gene located on the long arm of chromosome 15, encodes makorin ring finger protein 3, which is involved in ubiquitination and cell signaling. The MKRN3 protein is derived only from RNA transcribed from the paternally inherited copy of the gene due to maternal imprinting. Currently, MKRN3 defects represent the most frequent known genetic cause of familial CPP. In this review, we explored the clinical, hormonal and genetic aspects of children with sporadic or familial CPP caused by mutations in the kisspeptin and MKRN3 systems, essential genetic factors for pubertal timing.

Mutational analysis of TAC3 and TACR3 genes in patients with idiopathic central pubertal disorders

OBJECTIVE

To investigate the presence of variants in the TAC3 and TACR3 genes, which encode NKB and its receptor (NK3R), respectively, in a large cohort of patients with idiopathic central pubertal disorders.

SUBJECTS AND METHODS

Two hundred and thirty seven patients were studied: 114 with central precocious puberty (CPP), 73 with normosmic isolated hypogonadotropic hypogonadism (IHH), and 50 with constitutional delay of growth and puberty (CDGP). The control group consisted of 150 Brazilian individuals with normal pubertal development. Genomic DNA was extracted from peripheral blood and the entire coding region of both TAC3 and TACR3 genes were amplified and automatically sequenced.

RESULTS

We identified one variant (p.A63P) in NKB and four variants, p.G18D, p.L58L (c.172C>T), p.W275* and p.A449S in NK3R, which were absent in the control group. The p.A63P variant was identified in a girl with CPP, and p.A449S in a girl with CDGP. The known p.G18D, p.L58L, and p.W275* variants were identified in three unrelated males with normosmic IHH.

CONCLUSION

Rare variants in the TAC3 and TACR3 genes were identified in patients with central pubertal disorders. Loss-of-function variants of TACR3 were associated with the normosmic IHH phenotype.

Central precocious puberty caused by mutations in the imprinted gene MKRN3

BACKGROUND

The onset of puberty is first detected as an increase in pulsatile secretion of gonadotropin-releasing hormone (GnRH). Early activation of the hypothalamic-pituitary-gonadal axis results in central precocious puberty. The timing of pubertal development is driven in part by genetic factors, but only a few, rare molecular defects associated with central precocious puberty have been identified.

METHODS

We performed whole-exome sequencing in 40 members of 15 families with central precocious puberty. Candidate variants were confirmed with Sanger sequencing. We also performed quantitative real-time polymerase-chain-reaction assays to determine levels of messenger RNA (mRNA) in the hypothalami of mice at different ages.

RESULTS

We identified four novel heterozygous mutations in MKRN3, the gene encoding makorin RING-finger protein 3, in 5 of the 15 families; both sexes were affected. The mutations included three frameshift mutations, predicted to encode truncated proteins, and one missense mutation, predicted to disrupt protein function. MKRN3 is a paternally expressed, imprinted gene located in the Prader-Willi syndrome critical region (chromosome 15q11-q13). All affected persons inherited the mutations from their fathers, a finding that indicates perfect segregation with the mode of inheritance expected for an imprinted gene. Levels of Mkrn3 mRNA were high in the arcuate nucleus of prepubertal mice, decreased immediately before puberty, and remained low after puberty.

CONCLUSIONS

Deficiency of MKRN3 causes central precocious puberty in humans. (Funded by the National Institutes of Health and others.).

Estrogen receptor α polymorphism in boys with constitutional delay of growth and puberty

PURPOSE

There were a lot of reports regarding associations of polymorphisms in the estrogen receptor α (ESR1). with many disorders. But, those with constitutional delay of growth and puberty (CDGP) are not known. Our aim is to find out any association between CDGP and ESR1.

METHODS

In a total of 27 subjects, we compared 7 CDGP patients with 20 healthy controls with their heights and sexual maturity rates were within normal range. We selected three single nucleotide polymorphisms from intron 1 of ESR1 (rs3778609, rs12665044, and rs827421) as candidates, respectively.

RESULTS

In genotype analyses, the frequency of G/G genotype at rs827421 in intron 1 of ESR1 was increased in CDGP boys (P=0.03).

CONCLUSION

The genetic variation of ESR1 can be a contributing factor of tempo of growth and puberty.

Elements of morphology: standard terminology for the external genitalia

An international group of clinicians working in the field of dysmorphology has initiated the standardization of terms used to describe human morphology. The goals are to standardize these terms and reach consensus regarding their definitions. In this way, we will increase the utility of descriptions of the human phenotype and facilitate reliable comparisons of findings among patients. Discussions with other workers in dysmorphology and related fields, such as developmental biology and molecular genetics, will become more precise. Here we introduce the anatomy of the male and female genitalia, and define and illustrate the terms that describe the major characteristics of these body regions. Published 2013. This article is a U.S. Government work and is in the public domain in the USA.

Peripubertal vitamin D(3) deficiency delays puberty and disrupts the estrous cycle in adult female mice

The mechanism(s) by which vitamin D(3) regulates female reproduction is minimally understood. We tested the hypothesis that peripubertal vitamin D(3) deficiency disrupts hypothalamic-pituitary-ovarian physiology. To test this hypothesis, we used wild-type mice and Cyp27b1 (the rate-limiting enzyme in the synthesis of 1,25-dihydroxyvitamin D(3)) null mice to study the effect of vitamin D(3) deficiency on puberty and reproductive physiology. At the time of weaning, mice were randomized to a vitamin D(3)-replete or -deficient diet supplemented with calcium. We assessed the age of vaginal opening and first estrus (puberty markers), gonadotropin levels, ovarian histology, ovarian responsiveness to exogenous gonadotropins, and estrous cyclicity. Peripubertal vitamin D(3) deficiency significantly delayed vaginal opening without affecting the number of GnRH-immunopositive neurons or estradiol-negative feedback on gonadotropin levels during diestrus. Young adult females maintained on a vitamin D(3)-deficient diet after puberty had arrested follicular development and prolonged estrous cycles characterized by extended periods of diestrus. Ovaries of vitamin D(3)-deficient Cyp27b1 null mice responded to exogenous gonadotropins and deposited significantly more oocytes into the oviducts than mice maintained on a vitamin D(3)-replete diet. Estrous cycles were restored when vitamin D(3)-deficient Cyp27b1 null young adult females were transferred to a vitamin D(3)-replete diet. This study is the first to demonstrate that peripubertal vitamin D(3) sufficiency is important for an appropriately timed pubertal transition and maintenance of normal female reproductive physiology. These data suggest vitamin D(3) is a key regulator of neuroendocrine and ovarian physiology.

Replication of loci influencing ages at menarche and menopause in Hispanic women: the Women's Health Initiative SHARe Study

Several genome-wide studies have identified loci associated with reproductive traits, such as ages of menarche and menopause, in women of European ancestry. In this study, we investigated the relevance of these loci in minority US Hispanic women. We utilized data from 3468 women who were genotyped as a part of the Women's Health Initiative SNP Health Association Resource. We replicated associations of eight loci (LRP18, LIN28B, CENPW, INHBA, TMEM38B, ZNF483, NFAT5 and OLFM2) with age at menarche, and of two loci (MCM8 and BRSK1/TMEM150B) with age at menopause. The MCM8 locus was also associated with early menopause risk. Three loci (CENPW, MCM8 and BRSK1/TMEM150B) were associated with the length of reproductive lifespan. We provide evidence that genetic variants influencing reproductive traits identified in European populations are also important in minority US Hispanic women.

The genes associated with gonadotropin-releasing hormone-dependent precocious puberty

Human puberty is a complex, coordinated biological process with multiple levels of regulations. The timing of puberty varies greatly in children and is influenced by both environmental and genetic factors. The key genes of pubertal onset, KISS1, GPR54, GNRH1 and GNRHR, may be major causal factors underlying gonadotropin-releasing hormone-dependent precocious puberty (GDPP). Two gain-of-function mutations in KISS1 and GPR54 have been identified recently as genetic causes of GDPP. GNRH1 and GNRHR are also gene candidates for GDPP; however no mutations have been identified in these genes. Presently potential genetic causes like LIN28B continues to appear; many areas of research await exploration in this context. In this review, I focus primarily on the genetic causes of GDPP.

New genetic factors implicated in human GnRH-dependent precocious puberty: the role of kisspeptin system

Human puberty is triggered by the reemergence of GnRH pulsatile secretion with progressive activation of the gonadal function. A number of genes have been identified in the complex regulatory neuroendocrine network that controls puberty initiation. KISS1 and KISS1R genes, which encode kisspeptin and its cognate receptor, respectively, are considered crucial factors for acquisition of normal reproductive function. Recently, rare missense mutations and single nucleotide polymorphisms (SNPs) of the kisspeptin system were associated with puberty onset. Two gain-of-function mutations of the KISS1 and KISS1R genes were implicated in the pathogenesis of GnRH-dependent precocious puberty, previously considered idiopathic. These discoveries have yielded significant insights into the physiology and pathophysiology of this important life transition time. Here, we review the current molecular defects that are implicated in human GnRH-dependent precocious puberty.

Genetic determinants of pubertal timing in the general population

Puberty is an important developmental stage during which reproductive capacity is attained. The timing of puberty varies greatly among healthy individuals in the general population and is influenced by both genetic and environmental factors. Although genetic variation is known to influence the normal spectrum of pubertal timing, the specific genes involved remain largely unknown. Genetic analyses have identified a number of genes responsible for rare disorders of pubertal timing such as hypogonadotropic hypogonadism and Kallmann syndrome. Recently, the first loci with common variation reproducibly associated with population variation in the timing of puberty were identified at 6q21 in or near LIN28B and at 9q31.2. However, these two loci explain only a small fraction of the genetic contribution to population variation in pubertal timing, suggesting the need to continue to consider other loci and other types of variants. Here we provide an update of the genes implicated in disorders of puberty, discuss genes and pathways that may be involved in the timing of normal puberty, and suggest additional avenues of investigation to identify genetic regulators of puberty in the general population.

GNRH1 mutations in patients with idiopathic hypogonadotropic hypogonadism

Idiopathic hypogonadotropic hypogonadism (IHH) is a condition characterized by failure to undergo puberty in the setting of low sex steroids and low gonadotropins. IHH is due to abnormal secretion or action of the master reproductive hormone gonadotropin-releasing hormone (GnRH). Several genes have been found to be mutated in patients with IHH, yet to date no mutations have been identified in the most obvious candidate gene, GNRH1 itself, which encodes the preprohormone that is ultimately processed to produce GnRH. We screened DNA from 310 patients with normosmic IHH (nIHH) and 192 healthy control subjects for sequence changes in GNRH1. In 1 patient with severe congenital nIHH (with micropenis, bilateral cryptorchidism, and absent puberty), a homozygous frameshift mutation that is predicted to disrupt the 3 C-terminal amino acids of the GnRH decapeptide and to produce a premature stop codon was identified. Heterozygous variants not seen in controls were identified in 4 patients with nIHH: 1 nonsynonymous missense mutation in the eighth amino acid of the GnRH decapeptide, 1 nonsense mutation that causes premature termination within the GnRH-associated peptide (GAP), which lies C-terminal to the GnRH decapeptide within the GnRH precursor, and 2 sequence variants that cause nonsynonymous amino-acid substitutions in the signal peptide and in GnRH-associated peptide. Our results establish mutations in GNRH1 as a genetic cause of nIHH.

Genetic variation in LIN28B is associated with the timing of puberty

The timing of puberty is highly variable. We carried out a genome-wide association study for age at menarche in 4,714 women and report an association in LIN28B on chromosome 6 (rs314276, minor allele frequency (MAF) = 0.33, P = 1.5 × 10(-8)). In independent replication studies in 16,373 women, each major allele was associated with 0.12 years earlier menarche (95% CI = 0.08-0.16; P = 2.8 × 10(-10); combined P = 3.6 × 10(-16)). This allele was also associated with earlier breast development in girls (P = 0.001; N = 4,271); earlier voice breaking (P = 0.006, N = 1,026) and more advanced pubic hair development in boys (P = 0.01; N = 4,588); a faster tempo of height growth in girls (P = 0.00008; N = 4,271) and boys (P = 0.03; N = 4,588); and shorter adult height in women (P = 3.6 × 10(-7); N = 17,274) and men (P = 0.006; N = 9,840) in keeping with earlier growth cessation. These studies identify variation in LIN28B, a potent and specific regulator of microRNA processing, as the first genetic determinant regulating the timing of human pubertal growth and development.

Androgen therapy for delayed male puberty

PURPOSE OF REVIEW

Delayed puberty in men is a commonly presenting problem to paediatricians and an understanding of the available evidence on cause, treatments and outcomes is important to guide practice.

RECENT FINDINGS

Understanding of the regulation of the onset of puberty is gradually unfolding, although the genetic factors that dictate the timing of puberty in individuals and families remain poorly elucidated. Mutations and polymorphisms in candidate genes are being actively studied and it is likely that there is significant overlap between traditional diagnostic categories. Also, environmental endocrine disruptors may interact with the genetic regulation of puberty. Delayed puberty may not always be a benign condition, with increased risks of failing to achieve target height, adverse psychological and educational consequences, delayed sexual and psychosocial integration into society and effects on skeletal proportions and bone mass reported. Appropriate evaluation and follow-up is needed to guide clinical practice, particularly to distinguish constitutional delay in growth and puberty from that associated with other medical disease or permanent disorders.

SUMMARY

In milder cases of delayed puberty, treatment is often not required; however, considerable evidence exists for the efficacy and safety of short courses of low-dose testosterone therapy for appropriately selected individuals. This treatment is associated with high levels of patient satisfaction. There is not yet sufficient evidence for the routine use of other therapies (e.g. growth hormone, aromatase inhibitors) for constitutional delay in growth and puberty and better characterization of cause may lead to more targeted individual therapy.