Determination of sequence variation and haplotype structure for the gonadotropin-releasing hormone (GnRH) and GnRH receptor genes: investigation of role in pubertal timing

Evaluation of the MC3R gene pertaining to body weight and height regulation and puberty development

Recent studies reported an impact of the melanocortin 3 receptor (MC3R) on the regulation of body weight, linear growth and puberty timing. Previously, allele p.44Ile of a frequent non-synonymous variant (NSV) p.Val44Ile was reported to be associated with decreased lean body mass (LBM) and later puberty in both sexes. We Sanger sequenced the coding region of MC3R in 185 children or adolescents with short normal stature (SNS) or 258 individuals with severe obesity, and 192 healthy-lean individuals. Eleven variants (six NSVs) were identified. In-silico analyses ensued. Three rare loss-of-function (LoF) variants (p.Phe45Ser, p.Arg220Ser and p.Ile298Ser) were only found in severely obese individuals. One novel highly conserved NSV (p.Ala214Val), predicted to increase protein stability, was detected in a single lean female. In the individuals with SNS, we observed deviation from Hardy-Weinberg Equilibrium (HWE) (p = 0.012) for p.Val44Ile (MAF = 11.62%). Homozygous p.44Ile carriers with SNS had an increased BMI, but this effect did not remain significant after Bonferroni correction. In line with previous findings, the detected LoF NSVs may suggest that dysfunction in MC3R is associated with decreased body height, obesity and delayed puberty.

Is age of menarche related to urinary symptoms in young Jordanian girls? A prospective cross-sectional study

Objectives

Methods

Results

Conclusion

Genetic Determinants of Prepubertal and Pubertal Growth and Development

This article surveys the current general understanding of genetic influences on within- and between-population variation in growth and development in the context of establishing an International Growth Standard for Preadolescent and Adolescent Children. Traditional genetic epidemiologic analysis methods are reviewed, and evidence from family studies for genetic effects on different measures of growth and development is then presented. Findings from linkage and association studies seeking to identify specific genomic locations and allelic variants of genes influencing variation in growth and maturation are then summarized. Special mention is made of the need to study the interactions between genes and environments. At present, specific genes and polymorphisms contributing to variation in growth and maturation are only beginning to be identified. Larger genetic epidemiologic studies are needed in different parts of the world to better explore population differences in gene frequencies and gene—environment interactions. As advances continue to be made in molecular and statistical genetic methods, the genetic architecture of complex processes, including those of growth and development, will become better elucidated. For now, it can only be concluded that although the fundamental genetic underpinnings of the growth and development of children worldwide are likely to be essentially the same, there are also likely to be differences between populations in the frequencies of allelic gene variants that influence growth and maturation and in the nature of gene–environment interactions. This does not necessarily preclude an international growth reference, but it does have important implications for the form that such a reference might ultimately take.

A shared genetic basis for self-limited delayed puberty and idiopathic hypogonadotropic hypogonadism

CONTEXT

Delayed puberty (DP) is a common issue and, in the absence of an underlying condition, is typically self limited. Alhough DP seems to be heritable, no specific genetic cause for DP has yet been reported. In contrast, many genetic causes have been found for idiopathic hypogonadotropic hypogonadism (IHH), a rare disorder characterized by absent or stalled pubertal development.

OBJECTIVE

The objective of this retrospective study, conducted at academic medical centers, was to determine whether variants in IHH genes contribute to the pathogenesis of DP.

SUBJECTS AND OUTCOME MEASURES

Potentially pathogenic variants in IHH genes were identified in two cohorts: 1) DP family members of an IHH proband previously found to have a variant in an IHH gene, with unaffected family members serving as controls, and 2) DP individuals with no family history of IHH, with ethnically matched control subjects drawn from the Exome Aggregation Consortium.

RESULTS

In pedigrees with an IHH proband, the proband's variant was shared by 53% (10/19) of DP family members vs 12% (4/33) of unaffected family members (P = .003). In DP subjects with no family history of IHH, 14% (8/56) had potentially pathogenic variants in IHH genes vs 5.6% (1 907/33 855) of controls (P = .01). Potentially pathogenic variants were found in multiple DP subjects for the genes IL17RD and TAC3.

CONCLUSIONS

These findings suggest that variants in IHH genes can contribute to the pathogenesis of self-limited DP. Thus, at least in some cases, self-limited DP shares an underlying pathophysiology with IHH.

Role of gonadotropin-releasing hormone receptor mutations in patients with a wide spectrum of pubertal delay

OBJECTIVE

To analyze the GNRHR in patients with normosmic isolated hypogonadotropic hypogonadism (IHH) and constitutional delay of growth and puberty (CDGP).

DESIGN

Molecular analysis and in vitro experiments correlated with phenotype.

SETTING

Academic medical center.

PATIENT(S)

A total of 110 individuals with normosmic IHH (74 male patients) and 50 with CDGP.

INTERVENTION(S)

GNRHR coding region was amplified and sequenced.

MAIN OUTCOME MEASURE(S)

Novel variants were submitted to in vitro analysis. Frequency of mutations and genotype-phenotype correlation were analyzed. Microsatellite markers flanking GNRHR were examined in patients carrying the same mutation to investigate a possible founder effect.

RESULT(S)

Eleven IHH patients (10%) carried biallelic GNRHR mutations. In vitro analysis of novel variants (p.Y283H and p.V134G) demonstrated complete inactivation. The founder effect study revealed that Brazilian patients carrying the p.R139H mutation shared the same haplotype. Phenotypic spectrum in patients with GNRHR mutations varied from complete GnRH deficiency to partial and reversible IHH, with a relatively good genotype-phenotype correlation. One boy with CDGP was heterozygous for the p.Q106R variant, which was not considered to be pathogenic.

CONCLUSION(S)

GNRHR mutations are a frequent cause of congenital normosmic IHH and should be the first candidate gene for genetic screening in this condition, especially in autosomal recessive familial cases. The founder effect study suggested that the p.R139H mutation arises from a common ancestor in the Brazilian population. Finally, mutations in GNRHR do not appear to be involved in the pathogenesis of CDGP.

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.

GnRH receptor mutations in isolated gonadotropic deficiency

GnRH and its receptor GnRHR are key regulators of the hypothalamo-pituitary axis. They modulate the secretion of LH and FSH gonadotropins and therefore, the development and maturation of gonads in fetal life as well as after birth. Congenital functional defect of this axis results in isolated hypogonadotropic hypogonadism (IHH). Several natural mutations causing IHH without anosmia have now been identified in GnRHR or GnRH genes. These mutations inactivate GnRHR or its ligand function and cause highly variable phenotypes, ranging from partial to complete gonadotropic deficiencies. The present review describes the published natural GnRHR mutations and tries to correlate them with the corresponding phenotypes according to the different steps of the GnRH system development.

A needle in a haystack: mutations in GNRH1 as a rare cause of isolated GnRH deficiency

GNRH1, the human gene that gives rise to GnRH, has long been an obvious candidate gene for idiopathic hypogonadotropic hypogonadism, particularly because the hpg mouse, a mouse model of isolated hypogonadotropic hypogonadism, carries a deletion that disrupts Gnrh1. In 2009, 25 years after the sequence of human GNRH1 was initially determined, two groups independently reported homozygous frameshift mutations in GNRH1 in patients with idiopathic hypogonadotropic hypogonadism. In two additional families, heterozygous GNRH1 mutations segregated with reproductive disorders. In the first family, the mutation occurred alone in five female subjects with idiopathic hypogonadotropic hypogonadism, whereas in the second it co-existed with a mutation in NR0B1/DAX1 in two female subjects with delayed puberty. While hemizygous mutations the X-linked NR0B1 are a well-known cause of hypogonadotropic hypogonadism and adrenal hypoplasia in male patients, heterozygous female carriers are generally asymptomatic. Thus, mutations in GNRH1 have been associated with both mild and severe forms of GnRH deficiency, and may work in combination with other gene mutations to produce GnRH-deficient phenotypes.

Novel inactivating mutations in the GH secretagogue receptor gene in patients with constitutional delay of growth and puberty

BACKGROUND

A limited number of mutations in the GH secretagogue receptor gene (GHSR) have been described in patients with short stature. Objective To analyze GHSR in idiopathic short stature (ISS) children including a subgroup of constitutional delay of growth and puberty (CDGP) patients.

SUBJECTS AND METHODS

The GHSR coding region was directly sequenced in 96 independent patients with ISS, 31 of them with CDGP, in 150 adults, and in 197 children with normal stature. The pharmacological consequences of GHSR non-synonymous variations were established using in vitro cell-based assays.

RESULTS

Five different heterozygous point variations in GHSR were identified (c.-6 G>C, c.251G>T (p.Ser84Ile), c.505G>A (p.Ala169Thr), c.545 T>C (p.Val182Ala), and c.1072G>A (p.Ala358Thr)), all in patients with CDGP. Neither these allelic variants nor any other mutations were found in 694 alleles from controls. Functional studies revealed that two of these variations (p.Ser84Ile and p.Val182Ala) result in a decrease in basal activity that was in part explained by a reduction in cell surface expression. The p.Ser84Ile mutation was also associated with a defect in ghrelin potency. These mutations were identified in two female patients with CDGP (at the age of 13 years, their height SDS were -2.4 and -2.3). Both patients had normal progression of puberty and reached normal adult height (height SDS of -0.7 and -1.4) without treatment.

CONCLUSION

This is the first report of GHSR mutations in patients with CDGP. Our data raise the intriguing possibility that abnormalities in ghrelin receptor function may influence the phenotype of individuals with CDGP.

An association study between the genetic polymorphisms within GnRHI, LHβ and FSHβ genes and central precocious puberty in Chinese girls

OBJECTIVES

Gonadotropin-releasing hormone (GnRH), luteinizing hormone (LH) and follicle-stimulating hormone (FSH) are three hypothalamic-pituitary-gonadal axis expressing hormones. They play critical roles in the onset of puberty. Here we report the relationship between the three hormones and Central Precocious Puberty (CPP) in Chinese Han girls.

METHODS

We analyzed the single nucleotide polymorphisms (SNPs) of 5'-flanking regions of these genes by DNA sequencing in 27 CPP samples. Then the SNPs sites were genotyped by ligase detection reaction in a total of 283 Chinese Han CPP cases and 284 matched controls. Distributions of the polymorphisms and haplotypes were calculated for statistical evaluation.

RESULTS

Nine SNPs (One in GnRHI gene: -2003 C/T; Five in LHβ gene: -1456 C/G, -1424 C/G, -238 G/A, -164 G/A and -34 T/A; Three in FSHβ gene: -1825 T/C, -261 G/T and -132 T/A.) were found. A quantitative genetic association study was made. -1825 T/C in FSHβ gene was related with CPP with a weak effect (P=0.025). A haplotype in the 5'-flanking region of LHβ gene was significantly associated with CPP in Chinese Han girls (P=8.25×10(-09)). However, analysis software showed that none of SNP was found in the regulating control element of these genes.

CONCLUSIONS

Our finding implies that the polymorphisms in the 5'-flanking regions of FSHβ gene and LHβ gene probably were related to the puberty onset time of these girls. Further studies on the polymorphisms are needed for the exact mechanism.

Determinants of menarche

Menarche is a milestone in a woman's life as it denotes the start of reproductive capacity. Aim of this report is to review the recent developments and the current knowledge in the neuroendocrinology of pubertal onset and the factors, genetic and environmental, that influence menarcheal age. We also review the implications of early or late menarcheal age on a young woman's life.

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.

Genetic polymorphisms of the GNRH1 and GNRHR genes and risk of breast cancer in the National Cancer Institute Breast and Prostate Cancer Cohort Consortium (BPC3)

Background

Gonadotropin releasing hormone (GNRH1) triggers the release of follicle stimulating hormone and luteinizing hormone from the pituitary. Genetic variants in the gene encoding GNRH1 or its receptor may influence breast cancer risk by modulating production of ovarian steroid hormones. We studied the association between breast cancer risk and polymorphisms in genes that code for GNRH1 and its receptor (GNRHR) in the large National Cancer Institute Breast and Prostate Cancer Cohort Consortium (NCI-BPC3).

Methods

We sequenced exons of GNRH1 and GNRHR in 95 invasive breast cancer cases. Resulting single nucleotide polymorphisms (SNPs) were genotyped and used to identify haplotype-tagging SNPs (htSNPS) in a panel of 349 healthy women. The htSNPs were genotyped in 5,603 invasive breast cancer cases and 7,480 controls from the Cancer Prevention Study-II (CPS-II), European Prospective Investigation on Cancer and Nutrition (EPIC), Multiethnic Cohort (MEC), Nurses' Health Study (NHS), and Women's Health Study (WHS). Circulating levels of sex steroids (androstenedione, estradiol, estrone and testosterone) were also measured in 4713 study subjects.

Results

Breast cancer risk was not associated with any polymorphism or haplotype in the GNRH1 and GNRHR genes, nor were there any statistically significant interactions with known breast cancer risk factors. Polymorphisms in these two genes were not strongly associated with circulating hormone levels.

Conclusion

Common variants of the GNRH1 and GNRHR genes are not associated with risk of invasive breast cancer in Caucasians.

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.

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

PURPOSE OF REVIEW

Puberty is an important developmental stage during which reproductive capacity is attained. Genetic and environmental factors both influence the timing of puberty, which varies greatly among individuals. However, although genetic variation is known to influence the normal spectrum of pubertal timing, the specific genes involved remain unknown.

RECENT FINDINGS

Recent genetic analyses have identified a number of genes responsible for rare disorders of pubertal timing such as hypogonadotropic hypogonadism and Kallmann syndrome. However, although the genetic basis of population variation in the timing of puberty is an active area of investigation, no genetic loci have been reproducibly associated with pubertal timing thus far.

SUMMARY

This review provides an update of the genes implicated in disorders of puberty, discusses genes and pathways that may be involved in the timing of normal puberty, and suggests additional avenues of investigation to identify genetic regulators of puberty in the general population.

Association studies of common variants in 10 hypogonadotropic hypogonadism genes with age at menarche

CONTEXT

Although the timing of puberty is a highly heritable trait, little is known about the genes that regulate pubertal timing in the general population. Several genes have been identified that, when mutated, cause disorders of delayed or absent puberty such as hypogonadotropic hypogonadism (HH).

OBJECTIVE

Because severe variants in HH-related genes cause a severe puberty phenotype, we hypothesized that common subtle variation in these genes could contribute to the population variation in pubertal timing.

DESIGN

We assessed common genetic variation in 10 HH-related genes in 1801 women from the Hawaii and Los Angeles Multiethnic Cohort with either early (age<11 yr) or late (age>14 yr) menarche and in other replication samples. In addition to these common variants, we also studied the most frequently reported HH mutations to assess their role in the population variation in pubertal timing. SETTING AND PATIENTS/OTHER PARTICIPANTS: Within the general community, 1801 women from the Hawaii and Los Angeles Multiethnic Cohort participated.

MAIN OUTCOME MEASURES

We assessed the association of genetic variation with age at menarche.

RESULTS

We found no significant association between any of the variants tested and age at menarche, although we cannot rule out modest effects of these variants or of other variants at long distances from the coding region. In several self-reported racial/ethnic groups represented in our study, we observed an association between estimated genetic ancestry and age at menarche.

CONCLUSIONS

Our results suggest that common variants near 10 HH-related loci do not play a substantial role in the regulation of age at menarche in the general population.

Pubertal development and menarche

Puberty is the developmental process that culminates in reproductive capability and is the result of a complex series of molecular and physiological events. The release of gonadotropin-releasing hormone from specialized neurons of the hypothalamus begins the hormonal cascade that causes gonadal activation and the physical changes of puberty. Several factors have been proposed to influence the activation of the hypothalamus to trigger puberty, but the involved pathways have not been fully elucidated. The recent observations that the age of pubertal onset may be lowering in American girls calls attention to the lack of knowledge of modulating factors that affect the pubertal process. Genes necessary for puberty have been found by studying persons who do not achieve puberty; such studies have provided insights into the pathways necessary for pubertal development. A multidisciplinary focus is required to elucidate the complex mechanisms involved in the initiation and progression of puberty.

Genetic control of pubertal timing

PURPOSE OF REVIEW

Puberty is an important developmental and life stage that leads to sexual maturation and reproductive capability. Although the physiology of puberty is similar among individuals, the timing of puberty is quite variable and affected by environmental and genetic influences. Identification of the responsible genetic factors will greatly enhance the understanding of the key components and the modulation of the hypothalamic-pituitary-gonadal axis.

RECENT FINDINGS

Genetic analyses are increasingly elucidating the genetic basis of pathological abnormalities in pubertal timing, including causes of idiopathic hypogonadotropic hypogonadism and Kallmann syndrome. Ongoing studies are also investigating the genetic control of puberty in the general population, although no definitive association between genetic variants and variations in pubertal timing has been discovered so far.

SUMMARY

This review summarizes recent advances regarding the genetic control of pubertal timing and presents areas for future investigation.

Constitutional delay of growth and puberty is not commonly associated with mutations in the acid labile subunit gene

OBJECTIVES

Constitutional delay of growth and puberty (CDGP) is a common clinical condition that may be inherited as an autosomal dominant, recessive or X-linked trait. However, single-gene defects underlying CDGP have not yet been identified. A small number of children (to date 10) with modest growth failure and in the majority delayed puberty, a phenotype similar to that of CDGP, have been reported to carry mutations in the IGF acid labile subunit (IGFALS) gene which encodes the ALS, a part of the ternary complex carrying IGF-I in the circulation. The aim of our study was to screen a well-characterised CDGP cohort exhibiting a range of growth retardation and pubertal delay for pathogenic sequence variants in IGFALS.

DESIGN AND METHODS

We used denaturing high performance liquid chromatography (dHPLC) to screen for IGFALS mutations in DNA samples from 90 children (80 males) with CDGP of predominantly White European origin. DNA fragments generating abnormal waveforms were directly sequenced.

RESULTS

No IGFALS mutation was identified in the coding sequences or exon-intron boundaries in our CDGP cohort. One abnormal waveform pattern in dHPLC in 15 children with CDGP was found to represent a recognised synonymous single-nucleotide polymorphism of the coding transcript in the second exon in residue 210 of IGFALS.

CONCLUSIONS

IGFALS sequence variants are unlikely to be a common association with pubertal delay in children with CDGP.

Gene-environment interactions, not neonatal growth hormone deficiency, time puberty in female rhesus monkeys

The factors that influence the timing of puberty and the onset of adult fertility are poorly understood. While focus on the juvenile period has provided insights into how growth-related cues affect pubertal timing, growth velocity during infancy that is sustained into the juvenile period may be important. On the other hand, social factors, specifically exposure to psychosocial stressors, can delay sexual maturation, possibly by altering growth velocities during development. Using female rhesus monkeys, the present study used a prospective analysis to determine how neonatal growth hormone (GH) inhibition with a sandostatin analog or suppression of the pituitary-gonadal axis with a GnRH analog affected growth and sexual maturation. A separate retrospective analysis was done assessing the effects of social dominance status during development on pubertal timing. Because a specific polymorphism in the gene encoding the serotonin (5HT) reuptake transporter increases vulnerability to psychosocial stressors, females were also genotyped and were then classified as socially dominant, having both alleles for the long promoter variant or having at least one allele for the short promoter variant, or as socially subordinate, having the long variant or having the short variant. Neonatal treatments were not balanced for social status or genotype, so analyses were performed separately. Although the neonatal treatments reduced GH secretion postnatally and through the juvenile period, neither growth nor sexual maturation was affected. In contrast, the retrospective analysis showed sexual maturation was delayed significantly in subordinate females carrying at least one allele of the short promoter variant in the gene encoding the 5HT reuptake transporter, and this delay was associated with reduced GH and leptin secretion during the juvenile phase but not with differences in growth velocities from birth. These data suggest that decreased neonatal GH secretion does not adversely affect sexual maturation, but that polymorphisms in the gene encoding the 5HT transporter modulate the adverse consequences of social subordination on the timing of puberty in female rhesus monkeys.

The genetic basis for the timing of human puberty

Puberty is a complex, coordinated biological process with multiple levels of regulation. Epidemiological observations suggest that the timing of pubertal events is a heritable trait, although environmental factors can modulate such genetic influence. The study of pathological states of early and late puberty has provided valuable insight into those genes that regulate gonadotrophin-releasing hormone (GnRH) activity. The development of pulsatile release of GnRH secretion mediated through kisspeptin-1 activation of G-protein coupled receptor-54 appears to be a central event at the onset and during progression of puberty. Stimulating and restraining influences (e.g. in the form of glutamatergic and GABAergic neuronal inputs) are likely to influence the timing of this process. The study of extreme variants of 'normality', such as constitutional delay of growth and puberty and early puberty, may lead to the recognition of additional genes and pathways that can modulate both the timing of pubertal onset and its tempo.

GnRH receptor and GPR54 inactivation in isolated gonadotropic deficiency

Isolated hypogonadotropic hypogonadism (IHH) is defined by a complete or partial impaired secretion of luteinizing hormone (LH) and follicle-stimulating hormone (FSH). In the regulation of the gonadotropic axis, the gonadotropin-releasing hormone (GnRH) and its receptor have evolved as a central element in fetal life, at puberty, and for reproduction in adulthood. GnRH resistance due to GnRH receptor (GnRHR) germ-line mutations was the first genetic alteration identified in patients with IHH. GnRHR mutated receptors are associated with impaired GnRH binding, intracellular trafficking or ligand-induced signal transduction, leading to various degrees of LH and FSH deficiency. Loss-of-function mutations of the GnRH receptor account for 50% of familial cases of IHH without anosmia. In 2003, mutations of GPR54 were identified in patients with IHH, opening a new pathway in the physiological regulation of puberty and reproduction. Kisspeptins, which are the natural ligands of GPR54, are potent stimulators of the LH and FSH secretion via the control of GnRH secretion or modulation of the pituitary response to GnRH stimulation. Genotype-phenotype correlations in IHH due to GnRHR and GPR54 mutations indicate that similar mutations may lead to a variable phenotype and suggest that the pituitary might have its own pubertal maturation independent from GnRH. These two causes of IHH result in a more quantitative than qualitative defect of the gonadotropic axis activation. Molecular genetics of IHH has led to a major breakthrough in the neuroendocrine regulation of the gonadotropic axis. New insights into the understanding of the initiation of puberty and in the therapeutic management of defects of the gonadotropic axis have emerged from these studies.

Evidence for involvement of the vitamin D receptor gene in idiopathic short stature via a genome-wide linkage study and subsequent association studies

Stature is a highly heritable trait under both polygenic and major gene control. We aimed to identify genetic regions linked to idiopathic short stature (ISS) in childhood, through a whole genome scan in 92 families each with two affected children with ISS, including constitutional delay of growth and puberty and familial short stature. Linkage analysis was performed for ISS, height and bone age retardation. Chromosome 12q11 showed significant evidence of linkage to ISS and height (maximum non-parametric multipoint LOD scores 3.18 and 2.31 at 55-58 cM, between D12S1301 and D12S1048), especially in sister-sister pairs (LOD score of 1.9 for ISS in 22 pairs). These traits were also linked to chromosomes 1q12 and 2q36. The region on chromosome 12q11 had previously shown significant linkage to adult stature in several genome scans and harbors the vitamin D receptor gene, which has been associated with variation in height. A single nucleotide polymorphism (SNP) (rs10735810, FokI), which leads to a functionally relevant alteration at the protein level, showed preferential transmission of the transcriptionally more active G-allele to affected children (P=0.04) and seems to be responsible for the observed linkage (P=0.05, GIST test). Bone age retardation showed moderate linkage to chromosomes 19p11-q11 and 7p14 (LOD scores 1.69 at 57 cM and 1.42 at 50 cM), but there was no clear overlap with linkage regions for stature. In conclusion, we identified significant linkage, which might be due to a functional SNP in the vitamin D receptor (VDR) gene and could be responsible for up to 34% of ISS cases in the population.

Impact of body mass index on growth in boys with delayed puberty

It is unclear whether overweight but otherwise healthy boys with delayed puberty have a variation of constitutional delay of growth and maturation (CDGM) or a different etiology for their pubertal delay. To characterize better this group of boys and investigate whether their growth pattern distinguishes them from boys with typical CDGM, growth data were analyzed in eight overweight (BMI SDS > or = 85th percentile) and 37 non-overweight (BMI SDS <85th percentile) boys with delayed puberty. Primary outcome measures included predicted height (PH) and adult height (AH). At diagnosis of delayed puberty, the overweight boys had less delayed bone ages (chronological age [CA] - bone age [BA] = 1.2 +/- 1.0 vs 2.5 +/- 1.1 years, p <0.01), greater height SDS for CA (-0.5 +/- 0.7 vs -2.4 +/- 0.8, p <0.001), and greater height SDS for BA (0.6 +/- 0.9 vs -0.4 +/- 1.1, p <0.05). PH for the overweight boys exceeded their mid-parental height (MPH) by 5.0 +/- 7.2 cm while non-overweight boys were predicted to fall below their MPH by 2.8 +/- 6.3 cm (p <0.01). Available AH data corroborated the differences in PH, with a trend for overweight boys to have greater height relative to their MPH than the non-overweight boys. These observations suggest that in the context of delayed puberty, being overweight may modulate adult height and/or that the etiology of delayed puberty in overweight boys may differ from typical CDGM.

The use of mouse chromosome substitution strains to investigate the genetic regulation of pubertal timing

Identification of genes underlying complex traits such as pubertal timing, is vital to our understanding of fundamental human developmental processes. Animal models can provide an important adjunct to more traditional human investigations. Within this review, we discuss the use and advantages of chromosome substitution strains in the investigation of factors that regulate the timing of the onset of puberty.