Estrogen Receptor α Inactivation in 2 Sisters: Different Phenotypic Severities for the Same Pathogenic Variant.

CONTEXT: Estrogens play an essential role in reproduction. Their action is mediated by nuclear α and ß receptors (ER) and by membrane receptors. Only 3 females and 2 males, from 3 families, with a loss of ERα function have been reported to date. OBJECTIVE: We describe here a new family, in which 2 sisters display endocrine and ovarian defects of different severities despite carrying the same homozygous rare variant of ESR1. METHODS: A 36-year-old woman from a consanguineous Jordanian family presented with primary amenorrhea and no breast development, with high plasma levels of 17ß-estradiol (E2), follicle-stimulating hormone and luteinizing hormone, and enlarged multifollicular ovaries, strongly suggesting estrogen resistance. Her 18-year-old sister did not enter puberty and had moderately high levels of E2, high plasma gonadotropin levels, and normal ovaries. RESULTS: Genetic analysis identified a homozygous variant of ESR1 leading to the replacement of a highly conserved glutamic acid with a valine (ERα-E385V). The transient expression of ERα-E385V in HEK293A and MDA-MB231 cells revealed highly impaired ERE-dependent transcriptional activation by E2. The analysis of the KISS1 promoter activity revealed that the E385V substitution induced a ligand independent activation of ERα. Immunofluorescence analysis showed that less ERα-E385V than ERα-WT was translocated into the nucleus in the presence of E2. CONCLUSION: These 2 new cases are remarkable given the difference in the severity of their ovarian and hormonal phenotypes. This phenotypic discrepancy may be due to a mechanism partially compensating for the ERα loss of function.

Prevalence and clinical characteristics of isolated forms of central precocious puberty: a cohort study at a single academic center.

OBJECTIVE: Isolated central precocious puberty (CPP) includes sporadic, familial and adoption-related forms, and the characterization of its etiology is challenging. This study investigated the prevalence and clinical characteristics of isolated CPP. DESIGN AND METHODS: This observational cohort study included all patients (n = 395) with CPP included in the database of a single academic pediatric care center over a period of 11.5 years. RESULTS: In total, 332 of the 395 patients (84%) had isolated forms of CPP; the proportion of male patients was lower in this group than for non-isolated CPP (4 vs 33%, P < 0.0001). These patients had sporadic (n = 228, 68.5%), familial (n = 82, 25%) or adoption-related (n = 22, 6.5%) forms. Clinical characteristics at diagnosis were similar between groups, but girls with sporadic CPP were older at referral than those with familial or adoption-related CPP (P < 0.02), and birth weight SDS was lower in adopted patients than in those from the sporadic and familial groups (P < 0.01). In the 72 families containing patients with familial forms, both recessive and dominant transmissions were observed between first-degree relatives. Potential maternal or paternal transmission was identified in two-thirds of the studied families, in similar proportions. An autosomal dominant mode of transmission with low penetrance was suggested by the high proportion of affected parents (33 of the 72 families, 46%). Clinical presentation was similar whatever the mode of inheritance. CONCLUSION: These findings highlight the need for careful monitoring of the various forms of CPP. Future studies should explore pathophysiological mechanisms, particularly for familial forms.

High prevalence of syndromic disorders in patients with non-isolated central precocious puberty.

Objective Non-idiopathic CPP is caused by acquired or congenital hypothalamic lesions visible on MRI or is associated with various complex genetic and/or syndromic disorders. This study investigated the different types and prevalence of non-isolated CPP phenotypes. Design and Methods This observational cohort study included all patients identified as having non-idiopathic CPP in the database of a single academic pediatric care center over a period of 11.5 years. Patients were classified on the basis of MRI findings for the CNS as having either hypothalamic lesions or complex syndromic phenotypes without structural lesions of the hypothalamus. Results In total, 63 consecutive children (42 girls and 21 boys) with non-isolated CPP were identified. Diverse diseases were detected, and the hypothalamic lesions visible on MRI (n = 28, 45% of cases) included hamartomas (n = 17; either isolated or with an associated syndromic phenotype), optic gliomas (n = 8; with or without neurofibromatosis type 1), malformations (n = 3) with interhypothalamic adhesions (n = 2; isolated or associated with syndromic CNS midline abnormalities, such as optic nerve hypoplasia, ectopic posterior pituitary) or arachnoid cysts (n = 1). The patients with non-structural hypothalamic lesions (n = 35, 55% of cases) had narcolepsy (n = 9), RASopathies (n = 4), encephalopathy or autism spectrum disorders with or without chromosomal abnormalities (n = 15) and other complex syndromic disorders (n = 7). Conclusion Our findings suggest that a large proportion (55%) of patients with non-isolated probable non-idiopathic CPP may have complex disorders without structural hypothalamic lesions on MRI. Future studies should explore the pathophysiological relevance of the mechanisms underlying CPP in these disorders.

Complete Kisspeptin Receptor Inactivation Does Not Impede Exogenous GnRH-Induced LH Surge in Humans.

Context: Mutations in the kisspeptin receptor (KISS1R) gene have been reported in a few patients with normosmic congenital hypogonadotropic hypogonadism (nCHH) (OMIM #146110). Objectives: To describe a female patient with nCHH and a novel homozygous KISS1R mutation and to assess the role of kisspeptin pathway to induce an ovulation by GnRH pulse therapy. Design, Setting, and Intervention: Observational study of a patient including genetic and kisspeptin receptor functions and treatment efficiency using a GnRH pump. Main Outcome Measure: Response to pulsatile GnRH therapy. Results: A partial isolated gonadotropic deficiency was diagnosed in a 28-year-old woman with primary amenorrhea and no breast development. A novel homozygous c.953T>C variant was identified in KISS1R. This mutation led to substitution of leucine 318 for proline (p.Leu318Pro) in the seventh transmembrane domain of KISS1R. Signaling via the mutated receptor was profoundly impaired in HEK293-transfected cells. The mutated receptor was not detected on the membrane of HEK293-transfected cells. After several pulsatile GnRH therapy cycles, an LH surge with ovulation and pregnancy was obtained. Conclusion: GnRH pulsatile therapy can induce an LH surge in a woman with a mutated KISS1R, which was previously thought to be completely inactivated in vivo.

Rabconnectin-3α is required for the morphological maturation of GnRH neurons and kisspeptin responsiveness.

A few hundred hypothalamic neurons form a complex network that controls reproduction in mammals by secreting gonadotropin-releasing hormone (GnRH). Timely postnatal changes in GnRH secretion are essential for pubertal onset. During the juvenile period, GnRH neurons undergo morphological remodeling, concomitantly achieving an increased responsiveness to kisspeptin, the main secretagogue of GnRH. However, the link between GnRH neuron activity and their morphology remains unknown. Here, we show that brain expression levels of Dmxl2, which encodes the vesicular protein rabconnectin-3α, determine the capacity of GnRH neurons to be activated by kisspeptin and estradiol. We also demonstrate that Dmxl2 expression levels control the pruning of GnRH dendrites, highlighting an unexpected role for a vesicular protein in the maturation of GnRH neuronal network. This effect is mediated by rabconnectin-3α in neurons or glial cells afferent to GnRH neurons. The widespread expression of Dmxl2 in several brain areas raises the intriguing hypothesis that rabconnectin-3α could be involved in the maturation of other neuronal populations.

Genotype-Phenotype Relationship in Patients and Relatives with SHOX Region Anomalies in the French Population.

BACKGROUND: The aim of our study was to describe a large population with anomalies involving the SHOX region, responsible for idiopathic short stature and Léri-Weill dyschondrosteosis (LWD), and to identify a possible genotype/phenotype correlation. METHODS: We performed a retrospective multicenter study on French subjects with a SHOX region anomaly diagnosed by multiplex ligation-dependent probe amplification or Sanger sequencing. Phenotypes were collected in each of the 7 genetic laboratories practicing this technique for SHOX analysis. RESULTS: Among 205 index cases and 100 related cases, 91.3% had LWD. For index cases, median age at evaluation was 11.7 (9.0; 15.9) years and mean height standard deviation score was -2.3 ± 1.1. A deletion of either SHOX or PAR1 or both was found in 74% of patients. Duplications and point mutations/indels affected 8 and 18% of the population, respectively. Genotype-phenotype correlation showed that deletions were more frequently associated with Madelung deformity and mesomelic shortening in girls, as well as with presence of radiologic anomalies, than duplications. CONCLUSIONS: Our results highlight genotype-phenotype relationships in the French population with a SHOX defect and provide new information showing that clinical expression is milder in cases of duplication compared to deletions.

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‡.

Expert consensus document: European Consensus Statement on congenital hypogonadotropic hypogonadism--pathogenesis, diagnosis and treatment.

Congenital hypogonadotropic hypogonadism (CHH) is a rare disorder caused by the deficient production, secretion or action of gonadotropin-releasing hormone (GnRH), which is the master hormone regulating the reproductive axis. CHH is clinically and genetically heterogeneous, with >25 different causal genes identified to date. Clinically, the disorder is characterized by an absence of puberty and infertility. The association of CHH with a defective sense of smell (anosmia or hyposmia), which is found in ∼50% of patients with CHH is termed Kallmann syndrome and results from incomplete embryonic migration of GnRH-synthesizing neurons. CHH can be challenging to diagnose, particularly when attempting to differentiate it from constitutional delay of puberty. A timely diagnosis and treatment to induce puberty can be beneficial for sexual, bone and metabolic health, and might help minimize some of the psychological effects of CHH. In most cases, fertility can be induced using specialized treatment regimens and several predictors of outcome have been identified. Patients typically require lifelong treatment, yet ∼10-20% of patients exhibit a spontaneous recovery of reproductive function. This Consensus Statement summarizes approaches for the diagnosis and treatment of CHH and discusses important unanswered questions in the field.

Rational design of triazololipopeptides analogs of kisspeptin inducing a long-lasting increase of gonadotropins.

New potent and selective KISS1R agonists were designed using a combination of rational chemical modifications of the endogenous neuropeptide kisspeptin 10 (KP10). Improved resistance to degradation and presumably reduced renal clearance were obtained by introducing a 1,4-disubstituted 1,2,3-triazole as a proteolysis-resistant amide mimic and a serum albumin-binding motif, respectively. These triazololipopeptides are highly potent full agonists of KISS1R and are >100 selective over the closely related NPFF1R. When injected in ewes with a quiescent reproductive system, the best compound of our series induced a much prolonged increase of luteinizing hormone release compared to KP10 and increased follicle-stimulating hormone plasma concentration. Hence, this KISS1R agonist is a new valuable pharmacological tool to explore the potential of KP system in reproduction control. Furthermore, it represents the first step to develop drugs treating reproductive system disorders due to a reduced activity of the hypothalamo-pituitary-gonadal axis such as delayed puberty, hypothalamic amenorrhea, and hypogonadotropic hypogonadism.

Haploinsufficiency of Dmxl2, encoding a synaptic protein, causes infertility associated with a loss of GnRH neurons in mouse.

Characterization of the genetic defects causing gonadotropic deficiency has made a major contribution to elucidation of the fundamental role of Kisspeptins and Neurokinin B in puberty onset and reproduction. The absence of puberty may also reveal neurodevelopmental disorders caused by molecular defects in various cellular pathways. Investigations of these neurodevelopmental disorders may provide information about the neuronal processes controlling puberty onset and reproductive capacity. We describe here a new syndrome observed in three brothers, which involves gonadotropic axis deficiency, central hypothyroidism, peripheral demyelinating sensorimotor polyneuropathy, mental retardation, and profound hypoglycemia, progressing to nonautoimmune insulin-dependent diabetes mellitus. High-throughput sequencing revealed a homozygous in-frame deletion of 15 nucleotides in DMXL2 in all three affected patients. This homozygous deletion was associated with lower DMXL2 mRNA levels in the blood lymphocytes of the patients. DMXL2 encodes the synaptic protein rabconnectin-3α, which has been identified as a putative scaffold protein for Rab3-GAP and Rab3-GEP, two regulators of the GTPase Rab3a. We found that rabconnectin-3α was expressed in exocytosis vesicles in gonadotropin-releasing hormone (GnRH) axonal extremities in the median eminence of the hypothalamus. It was also specifically expressed in cells expressing luteinizing hormone (LH) and follicle-stimulating hormone (FSH) within the pituitary. The conditional heterozygous deletion of Dmxl2 from mouse neurons delayed puberty and resulted in very low fertility. This reproductive phenotype was associated with a lower number of GnRH neurons in the hypothalamus of adult mice. Finally, Dmxl2 knockdown in an insulin-secreting cell line showed that rabconnectin-3α controlled the constitutive and glucose-induced secretion of insulin. In conclusion, this study shows that low levels of DMXL2 expression cause a complex neurological phenotype, with abnormal glucose metabolism and gonadotropic axis deficiency due to a loss of GnRH neurons. Our findings identify rabconectin-3α as a key controller of neuronal and endocrine homeostatic processes.

Somatostatin receptors type 2 and 5 expression and localization during human pituitary development.

Somatostatin (SRIF), by acting mainly through sst2 and sst5 receptors, is a potent inhibitor of hormonal secretion by the human anterior pituitary gland. However, the pattern of protein expression of these SRIF receptors remains unknown during pituitary development. To get further insights into the physiological role of SRIF receptors in human development and pituitary function, the present study examined the developmental expression of the sst2 and sst5 receptors in the individual cell types of the anterior human pituitary. Thirteen fetal human pituitaries were investigated between 13 to 38 weeks of gestation (WG) by double-labeling immunofluorescence with antibodies raised against sst2 or sst5 receptors and GH, LH, FSH, TSH, or pro-opiomelanocortin proteins. SRIF immunoreactivity in the hypothalamus and median eminence was investigated at the same developmental ages. Immunoreactivity for the sst2 receptor was evident as early as 13 to 15 WG and onward mainly in TSH-, LH-, and FSH-expressing cells, whereas sst5 immunoreactivity was apparent at the late development stages (35-38 WG). GH-expressing cells mainly expressed sst5 immunoreactivity. SRIF-positive fibers and cells were detected as soon as 13 to 16 WG in the hypothalamus and median eminence and their densities increased with gestational age. The early appearance of hypothalamic SRIF cells and fibers suggests a physiological link between SRIF and its receptors during pituitary development. Whereas sst2 receptors might play a primary role in the differentiation and regulation of TSH, LH, and FSH cells, sst5 receptors appear to be mainly involved in GH regulation from birth onward.

PRR repeats in the intracellular domain of KISS1R are important for its export to cell membrane.

Inactivating mutations of KISS-1 receptor (KISS1R) have been recently described as a rare cause of isolated hypogonadotropic hypogonadism transmitted as a recessive trait. Few mutations have been described, and the structure-function relationship of KISS1R remains poorly understood. Here, we have taken advantage of the discovery of a novel mutation of KISS1R to characterize the structure and function of an uncommon protein motif composed of 3 proline-arginine-arginine (PRR) repeats located within the intracellular domain. A heterozygous insertion of 1 PRR repeat in-frame with 3 PRR repeats leading to synthesis of a receptor bearing 4 PRR repeats (PRR-KISS1R) was found in the index case. Functional analysis of PRR-KISS1R showed a decrease of the maximal response to kisspeptin stimulation, associated to a lower cell surface expression without modification of total expression. PRR-KISS1R exerts a dominant negative effect on the synthesis of the wild-type (WT)-KISS1R. This effect was due to the nature of inserted residues but also to the difference of the length of the intracellular domain between PRR-KISS1R and WT-KISS1R. A molecular dynamic analysis showed that the additional PRR constrained this arginine-rich region into a polyproline type II helix. Altogether, this study shows that a heterozygous insertion in KISS1R may lead to hypogonadotropic hypogonadism by a dominant negative effect on the WT receptor. An additional PRR repeat into a proline-arginine-rich motif can dramatically changed the conformation of the intracellular domain of KISS1R and its probable interaction with partner proteins.

PROKR2 and PROK2 mutations cause isolated congenital anosmia without gonadotropic deficiency.

OBJECTIVE: Isolated congenital anosmia (ICA) is a rare phenotype defined as absent recall of any olfactory sensations since birth and the absence of any disease known to cause anosmia. Although most cases of ICA are sporadic, reports of familial cases suggest a genetic cause. ICA due to olfactory bulb agenesis and associated to hypogonadotropic hypogonadism defines Kallmann syndrome (KS), in which several gene defects have been described. In KS families, the phenotype may be restricted to ICA. We therefore hypothesized that mutations in KS genes cause ICA in patients, even in the absence of family history of reproduction disorders. DESIGN AND METHODS: In 25 patients with ICA and olfactory bulb agenesis, a detailed phenotype analysis was conducted and the coding sequences of KAL1, FGFR1, FGF8, PROKR2, and PROK2 were sequenced. RESULTS: Three PROKR2 mutations previously described in KS and one new PROK2 mutation were found. Investigation of the families showed incomplete penetrance of these mutations. CONCLUSIONS: This study is the first to report genetic causes of ICA and indicates that KS genes must be screened in patients with ICA. It also confirms the considerable complexity of GNRH neuron development in humans.

Negative fetal FSH/LH regulation in late pregnancy is associated with declined kisspeptin/KISS1R expression in the tuberal hypothalamus.

OBJECTIVE: Kisspeptins were recently identified as hypothalamic neuropeptides that control GnRH release at pubertal onset and in adults via the activation of KISS-1 receptor (KISS1R). Here, we have tested whether the fetal activation of the gonadotropic axis is related to the hypothalamic expression of kisspeptins and KISS1R. DESIGN AND METHODS: LH and FSH levels were measured in fetal blood from the 15th week of gestation (WG) to birth. Immunohistochemistry was performed on the hypothalamus and pituitary at different developmental stages. RESULTS: Immunostaining for kisspeptins and KISS1R appeared for both proteins in the hypothalamus as early as 15 WG and subsequently increased until 30-31 WG. In the meantime, serum LH and FSH levels decreased from postmenopausal levels in females or adult levels in males to very low levels. At full term, kisspeptin and KISS1R staining was still observed in the paraventricular, supraoptic, and ventromedial hypothalamic nuclei but not in the arcuate nucleus or median eminence. Hypothalamic GnRH staining was observed at 15 WG and did not vary after the first trimester. In an arhinencephalic fetus of 23 WG, very few GnRH neurons were observed in the hypothalamus, but serum FSH and LH levels were postmenopausal. CONCLUSION: Serum LH and FSH levels are independent from GnRH and kisspeptins at midgestation, and then GnRH progressively controls LH and FSH release. A shift from kisspeptin-independent to kisspeptin-dependent GnRH-induced LH and FSH release seems to occur after 30-31 WG. In addition to their function in adults, kisspeptins are also the master regulators of the gonadotropic axis activation in the fetus.

DNA polymorphisms of the KiSS1 3' untranslated region interfere with the folding of a G-rich sequence into G-quadruplex.

KISS1R and its ligand, the kisspeptins, are key hypothalamic factors that regulate GnRH hypothalamic secretion and therefore the pubertal timing. During studies analysing KiSS1 as a candidate gene in pubertal onset disorders, two SNP and one nucleotide insertion were observed in a 23 nucleotides G-rich sequence located 65 nucleotides downstream of the stop codon. The polymorphisms formed four haplotypes. Biophysical experiments revealed the ability of this G-rich sequence to fold into G-quadruplex structures and demonstrated that the three DNA polymorphisms did not perturb the folding into G-quadruplex but affected G-quadruplex conformation. A functional luciferase reporter-based assay revealed functional differences between 3'UTR haplotypes. These data show that polymorphisms in a G-rich sequence of the 3'UTR of KISS1, able to fold into G-quadruplex structures, can modulate gene expression. They highlight the potential role of this G-quadruplex in the regulation of KISS1 expression and in the timing of pubertal onset.

[The genetic control of puberty onset]. / Le contrôle génétique de l'initiation de la puberté.

Puberty is triggered by a complex neuroendocrine mechanism that leads to an increase in GnRH release at the end of the childhood and, hence, to reactivation of the gonadotropic axis. Recent human genetic studies have led to major breakthroughs in our understanding of puberty onset. A network of hypothalamic neurons controlling GnRH release has just been characterized. It appears that the timing of puberty onset is under the control of the heterochronic gene Lin28, which encodes a protein regulating microRNA maturation. Characterization of additional gene defects associated with abnormal puberty onset is needed to further characterize this neuroendocrine network and to identify new therapeutic targets for reproductive disorders.

Dental agenesis in Kallmann syndrome individuals with FGFR1 mutations.

BACKGROUND: Kallmann syndrome (KS) is a rare genetic disorder characterised by central hypogonadism with a lack of sense of smell and in some cases renal aplasia, deafness, syndactyly, cleft lip/palate, and dental agenesis. To date, five genes for KS have been identified: KAL1, located on the X chromosome, and FGFR1, PROKR2, PROK2 and FGF8, which are involved in autosomally transmitted forms of KS. AIM: The study characterised the dental ageneses of individuals with KS associated with mutations in the FGFR1 gene. DESIGN: Six individuals displaying dental agenesis were included. Clinical and radiological dental evaluations as well as medical anamneses were carried out. RESULTS: Microdontia, screwdriver-shaped mandibular incisors, thin molar roots, and patterns of dental agenesis in both dentitions were observed. One to nine teeth were missing, most frequently, in descending order, lateral mandibular incisors, second premolars of upper and lower jaws, and lateral maxillary incisors. The pattern of dental agenesis is associated with four new mutations in the FGFR1 gene. CONCLUSION: Dental agenesis may be a clinical feature of Kallmann syndrome caused by a mutation in the FGFR1 gene. These findings highlight the role that odontologists can play in the early diagnosis and treatment of gonadotropic deficiency.

KISS1 is down-regulated by 17beta-estradiol in MDA-MB-231 cells through a nonclassical mechanism and loss of ribonucleic acid polymerase II binding at the proximal promoter.

Kisspeptins are hypothalamic neuropeptides encoded by KISS1 and recently described as major regulators of GnRH release from hypothalamic neurons. Although 17beta-estradiol (E2)-induced up-regulation of KISS1 expression has been documented in anteroventral periventricular nucleus neurons, E2 down-regulates KISS1 expression in arcuate nucleus neurons via the estrogen receptor alpha by unknown molecular mechanisms. Because KISS1 was initially described as a metastasis inhibitor, notably in breast tumors, we used the MDA-MB-231 breast cancer cell line, which expresses high levels of KISS1, to characterize the molecular mechanism underlying KISS1 regulation by E2. E2 rapidly down-regulated endogenous KISS1 in a stable ERalpha-expressing MDA-MB-231 cell line. Promoter analysis revealed that E2 down-regulation was determined by a short 93-bp sequence devoid of estrogen response element and Sp1 sites. E2 down-regulation persisted with an ERalpha that was unable to bind DNA and in the presence of histone deacetylase inhibitor. In the absence of E2, unliganded ERalpha and RNA polymerase II (RNAPII) were present on the proximal promoter. E2 stimulation induced recruitment of ERalpha and loss of RNAPII at the proximal promoter. Along the gene body, total RNAPII amounts were similar in E2-treated and untreated cells, whereas the active form was significantly less abundant in E2-treated cells. Thus, E2-induced down-regulation of KISS1 is mediated by a pathway combining RNAPII loss at the proximal promoter and modulation of active RNAPII along the gene body, which is a novel mechanism in the complex process of E2-induced repression of gene expression.

[Biological mechanisms and genes involved in puberty]. / Mécanismes biologiques et gènes impliqués dans le développement de la puberté.

Puberty is an important step in human development. Onset of puberty, including neurobiological mechanisms important for the increase of hypothalamic GnRH pulses remains a mystery. After birth, GnRH secretion remains elevated and then decreases during childhood regardless of any steroid gonadal feedback. This period of quiescence of the gonadotropic axis during childhood is linked to a central inhibition of GnRH secretion which is replaced by an activator tone at puberty. The study of the pathology of the pubertal timing, including delayed puberty led to the discovery of new genes involved in the migration of GnRH neurons and genes involved in the neuroendocrine regulation of the gonadotropic axis. Recently, the emphasis on the importance of the kiss/GPR54 system in modulating control of the gonadotropic axis at puberty has recently emerged from Human genetics studies.

High tumoral levels of Kiss1 and G-protein-coupled receptor 54 expression are correlated with poor prognosis of estrogen receptor-positive breast tumors.

KiSS1 is a putative metastasis suppressor gene in melanoma and breast cancer-encoding kisspeptins, which are also described as neuroendocrine regulators of the gonadotropic axis. Negative as well as positive regulation of KiSS1 gene expression by estradiol (E(2)) has been reported in the hypothalamus. Estrogen receptor alpha (ERalpha level is recognized as a marker of breast cancer, raising the question of whether expression of KiSS1 and its G-protein-coupled receptor (GPR54) is down- or upregulated by estrogens in breast cancer cells. KiSS1 was found to be expressed in MDA-MB-231, MCF7, and T47D cell lines, but not in ZR75-1, L56Br, and MDA-MB-435 cells. KiSS1 mRNA levels decreased significantly in ERalpha-negative MDA-MB-231 cells expressing recombinant ERalpha. In contrast, tamoxifen (TAM) treatment of ERalpha-positive MCF7 and T47D cells increased KiSS1 and GPR54 levels. The clinical relevance of this negative regulation of KiSS1 and GPR54 by E(2) was then studied in postmenopausal breast cancers. KiSS1 mRNA increased with the grade of the breast tumors. ERalpha-positive invasive primary tumors expressed sevenfold lower KiSS1 levels than ERalpha-negative tumors. Among ERalpha-positive breast tumors from postmenopausal women treated with TAM, high KiSS1 combined with high GPR54 mRNA tumoral levels was unexpectedly associated with shorter relapse-free survival (RFS) relative to tumors expressing low tumoral mRNA levels of both genes. The contradictory observation of putative metastasis inhibitor role of kisspeptins and RFS to TAM treatment suggests that evaluation of KiSS1 and its receptor tumoral mRNA levels could be new interesting markers of the tumoral resistance to anti-estrogen treatment.