GnRH Neuronal Migration Research Articles

7640 The first description of an MC4R variant in a patient with Kallmann syndrome and obesity

Abstract Disclosure: A.A. Aslam: None. S. Lim: None. R. Willemsen: None. K. Koysombat: None. M. Young: None. W.S. Dhillo: None. A. Abbara: None. S. Howard: None. E.F. Gevers: None. Introduction: Pathogenic MC4R gene variants result in hyperphagia and early onset obesity but puberty is not usually affected. We describe an MC4R variant in a patient with Kallmann syndrome and obesity. A 16 year old male with repaired Tetralogy of Fallot, anosmia, autism and anxiety, was referred with obesity and delayed puberty. His birth weight was 3360 g (-0.26 SDS). Height was -1.31 SDS, BMI 30.7 kg/m2. He had high arched palate, normal skin and hair colour, mild hypertelorism and upward slanting palpebral fissures. Pubertal staging was A2P1G1 5ml testes bilaterally. Results: LHRH test showed borderline low peaks (LH 5.0 U/L, FSH 2.6 U/L) and inhibin B 108 pg/mL (25-325 pg/mL). MRI brain showed hypoplastic olfactory bulbs, absent olfactory sulci and normal pituitary anatomy. CGH microarray, karyotype and the UK hypogonadism gene panel were normal. He underwent whole genome sequencing in the Genetic Factors Affecting the Timing of Puberty Study; no abnormalities in 52 known genes associated with GnRH deficiency were found but a previously described heterozygous variant was detected, MC4R c.542G>A, p.Gly181Asp, classified pathogenic and absent in control databases. Management: He was commenced on Testosterone but showed progression of testicular size to 10 mL and testosterone was stopped but required restarting. Repeat investigations off treatment, aged 22 years (height 178 cm, BMI 42 kg/m2, testes 15 mL): inhibin B 66 pg/mL, testosterone 2 nmol/L, baseline LH 2.4 U/L, stimulated peak 24.9 U/L, baseline FSH 1.2 U/L, stimulated peak 4.2 U/L. Cortisol and IGF1 were in the normal range. He also developed autoimmune hypothyroidism with raised TPO antibodies (TSH 24.7 mU/L, FT4 5.6 pmol/L). Discussion: Previous in vitro work has shown complete loss of function of MC4R p.Gly181Asp due to reduced cell surface expression and reduced binding to a-MSH. Heterozygous p.Gly181Asp variants have been described in several children/adults with obesity; but hypogonadism in heterozygous carriers has not. Homozygous MC4R p.Gly181Asp was found in a male with obesity and partial HH thought to be due to abnormal GnRH production but with normal olfactory bulbs. We are the first to describe a heterozygous MC4R p.Gly181Asp variant in a patient with partial hypogonadism and anosmia with hypoplastic bulbs in addition to obesity. Interaction between POMC-MC-leptin circuits and Kisspeptin-GnRH circuits is recognised although not completely understood. Previous work has shown that a subset of kisspeptin neurons express MC4R and that KNDy neurones receive synaptic input from POMC neurons. In addition, inhibition of MC4R/MC3R results in delayed onset of puberty in rats. Our results support a role for MC4R in GnRH secretion and potentially olfactory /GnRH neuronal migration. Assessment of spontaneous gonadotrophin production and response of gonadotrophin production to kisspeptin stimulation is currently in progress. Presentation: 6/1/2024

Kallmann Syndrome - causes, symptoms, treatment - review of literature

Background: Kallmann syndrome is a rare congenital disorder characterized by hypogonadotropic hypogonadism and anosmia or hyposmia. KS results from abnormalities in the migration of GnRH neurons from the nasal placode to the hypothalamus. The prevalence of KS is estimated to be approximately 1:30,000 in males and 1:125,000 in females. KS manifests at various stages of life, ranging from the neonatal period through adolescence to adulthood. In the neonatal period, boys may present with cryptorchidism and micropenis, while symptoms in girls may be less apparent. During adolescence, patients often experience the absence or incomplete development of secondary sexual characteristics. In adulthood, KS often leads to infertility, cardiovascular issues, and neurological symptoms. Diagnostic methods include olfactory tests and hormonal analysis, assessing levels of gonadotropins, testosterone, LH and FSH. MRI can reveal structural abnormalities in the olfactory system. Aim of study: The goal of this article was to gather information about the Kallmann syndrome, focusing on its epidemiology, etiology, characteristic features, and treatment strategies. Materials and Methods: A review of the literature available in the “PubMed”, Google Scholar and Medline databases. The search was performed by using following keywords: “kallmann syndrome”, “anosmia”, hypogonadotropic hypogonadism”. Results and conclusions: Kallmann syndrome is a complex condition that necessitates a multifaceted approach to diagnosis and treatment. Early identification of the disorder is crucial, allowing for the timely initiation of appropriate hormonal therapy and psychological support, which significantly improves the quality of life for patients. Further research into the genetic and neurobiological mechanisms of KS is essential for the development of more effective therapeutic and diagnostic methods.

Methylome analysis in girls with idiopathic central precocious puberty

BackgroundGenetic and environmental factors are implicated in many developmental processes. Recent evidence, however, has suggested that epigenetic changes may also influence the onset of puberty or the susceptibility to a wide range of diseases later in life. The present study aims to investigate changes in genomic DNA methylation profiles associated with pubertal onset analyzing human peripheral blood leukocytes from three different groups of subjects: 19 girls with central precocious puberty (CPP), 14 healthy prepubertal girls matched by age and 13 healthy pubertal girls matched by pubertal stage. For this purpose, the comparisons were performed between pre- and pubertal controls to identify changes in normal pubertal transition and CPP versus pre- and pubertal controls.ResultsAnalysis of methylation changes associated with normal pubertal transition identified 1006 differentially methylated CpG sites, 86% of them were found to be hypermethylated in prepubertal controls. Some of these CpG sites reside in genes associated with the age of menarche or transcription factors involved in the process of pubertal development. Analysis of methylome profiles in CPP patients showed 65% and 55% hypomethylated CpG sites compared with prepubertal and pubertal controls, respectively. In addition, interestingly, our results revealed the presence of 43 differentially methylated genes coding for zinc finger (ZNF) proteins. Gene ontology and IPA analysis performed in the three groups studied revealed significant enrichment of them in some pathways related to neuronal communication (semaphorin and gustation pathways), estrogens action, some cancers (particularly breast and ovarian) or metabolism (particularly sirtuin).ConclusionsThe different methylation profiles of girls with normal and precocious puberty indicate that regulation of the pubertal process in humans is associated with specific epigenetic changes. Differentially methylated genes include ZNF genes that may play a role in developmental control. In addition, our data highlight changes in the methylation status of genes involved in signaling pathways that determine the migration and function of GnRH neurons and the onset of metabolic and neoplastic diseases that may be associated with CPP in later life.

Archetypal clustering reveals physiological mechanisms linking milk yield and fertility in dairy cattle

Fertility in dairy cattle has declined as an unintended consequence of single trait selection for high milk yield. The unfavorable genetic correlation between milk yield and fertility is now well-documented, however, the underlying physiological mechanisms are still uncertain. To understand the relationship between these traits, we developed a method that clusters variants with similar patterns of effects and, after the integration of gene expression data, identifies the genes through which they are likely to act. Biological processes that are enriched in the genes of each cluster were then identified. We identified several clusters with unique patterns of effects. One of the clusters included variants associated with increased milk yield and decreased fertility, where the 'archetypal' variant (i.e., the one with the largest effect) was associated with the gene GC, while others were associated with TRIM32, LRRK2, and U6. These genes have been linked to transcription and alternative splicing, suggesting that these processes are likely contributors to the unfavorable relationship between the 2 traits. Another cluster, with archetypal variant near DGAT1 and including variants associated with CDH2, BTRC, SFRP2, ZFHX3, and SLITRK5, appeared to affect milk yield but have little effect on fertility. These genes have been linked to insulin, adipose tissue, and energy metabolism. A third cluster with archetypal variant near ZNF613 and including variants associated with ROBO1, EFNA5, PALLD, GPC6, and PTPRT were associated with fertility but not milk yield. These genes have been linked to GnRH neuronal migration, embryonic development, and/or ovarian function. The use of archetypal clustering to group variants with similar patterns of effects may assist in identifying the biological processes underlying correlated traits. The method is hypothesis-generating and requires experimental confirmation. However, we have uncovered several novel mechanisms potentially affecting milk production and fertility such as GnRH neuronal migration. We anticipate our method to be a starting point for experimental research into novel pathways which have been previously unexplored within the context of dairy production.

FRI272 Sex-Specific Role Of ProkR2 Neurons Of The Posterior Amygdala In The Integration Of Odors And Neuroendocrine Responses

Abstract Disclosure: B. Cisneros-Larios: None. C.F. Elias: None. Kallmann Syndrome (KS) is characterized by abnormal development of the reproductive axis and olfactory bulb dysgenesis. Genetic studies have revealed that Kallmann Syndrome is caused by loss-of-function mutations in several genes including the prokineticin receptor 2 (PROKR2) gene. Prokr2 null mice exhibit the same phenotype of KS patients. While the role of PROKR2 during development has been linked with GnRH neuron migration, limited data exists on PROKR2 neurons in adult reproduction. PROKR2 mRNA are highly expressed in reproductive control sites. Furthermore, our lab previously found sexually dimorphic expression of PROKR2 mRNA and Prokr2-Cre GFP+ cells in several reproductive control sites. The posterior amygdala had higher PROKR2 expression in males compared to female mice. More recently, we identified expression of sex steroid receptors in PROKR2 expressing cells of the PA. The amygdala is an important site of socio-sexual inputs and reproductive neuroendocrine responses in rodents and primates, including humans. We hypothesize Prokr2-Cre neurons in the PA have a role in male reproductive function. Using genetic tracing techniques, we mapped PA Prokr2-Cre neuronal projections in male mice and found dense innervation to reproductive control sites such as the medial preoptic area and the ventral premammillary nucleus. We found activation of these neurons, via fos expression, after opposite sex soiled bedding exposure (olfactory cues). Lastly, selective activation, using chemogenetic technology DREADDs, of PA Prokr2-Cre cells in males can induce a rise in circulating luteinizing hormone. These data suggest PA Prokr2-Cre cells have a role in pathways integrating olfactory cues and reproductive endocrine responses (e.g., aggression, mating behavior). We expect our studies will contribute to the understanding of the role of PROKR2 neurons in adult reproduction and reproductive deficits associated with PROKR2 mutations. Presentation: Friday, June 16, 2023

SAT591 Abnormal Levels Of Thyroid Hormones During Development Alters The Migration And Activity Of GnRH Reproductive Neurons

Abstract Disclosure: C. Quignon: None. A. Backer: None. S. Wray: None. Clinical studies have shown that thyroid hormones disorders and alteration of thyroid hormone production by environmental endocrine disruptors, have deleterious effects on reproduction. By acting in the brain on the hypothalamic component of the reproductive axis, abnormal levels of thyroid hormones can disturb sex hormones production, oestrus cycles or puberty onset, possibly leading to subfertility. Moreover, in animal models, endocrine disruptors and thyroid hormones have been shown to have long-lasting transgenerational effects with the maternal hormones influencing the development of foetal reproductive functions. Despite clear evidence of an interaction between the thyroid and reproductive systems, the effect of T3, the active form of thyroid hormones, on the GnRH neurons controlling reproduction, have been poorly studied. In this work we investigated how T3 functionally interacts with GnRH neurons and how abnormal concentration of T3 alters the migration of these neurons during development. Calcium imaging was used to study the direct effect of T3 on GnRH neuronal activity in an ex vivo nasal explants model. Acute administration of T3 (30nM) was found to stimulate the activity of GnRH cells. Dual labelling of GnRH and thyroid hormone receptors (TR) showed that the GnRH neurons express both nuclear and membrane receptors. However, the use of an antagonist that specifically blocks the TR nuclear receptors (1-850), didn’t inhibit the T3 stimulatory effect. In contrast, blockage of integrin αV/β3 membrane receptors (with cilengitide), which have been shown to be activated by T3, prevented the T3-induced increase in GnRH neuronal activity. During development GnRH neurons migrate from the nasal placodes into the brain. Acute administration of T3 for 1hr significatively decreased the migration rate of the GnRH neurons in our ex vivo model. To assess the effect of thyroid disruption during pregnancy on the development of reproductive axis in utero, pregnant females mice have been treated with methimazole to induce hypothyroidism from gestational day 6 to 13. E13 embryos have been collected from treated and control dams and the distribution of migrating GnRH neurons will be compared between both groups. Together these studies are the first to report a direct effect of thyroid hormones on GnRH neuronal activity, through the integrin αV/β3 membrane receptors and show that T3 can modulate the migration of GnRH neurons during development. These results will bring new insights on how thyroid disruption by endocrine disruptor chemicals or thyroid diseases, especially during foetal development, can lead to long term reproductive defects. Presentation: Saturday, June 17, 2023

Phenotypic and genotypic landscape of PROKR2 in neuroendocrine disorders.

Prokineticin receptor 2 (PROKR2) encodes for a G-protein-coupled receptor that can bind PROK1 and PROK2. Mice lacking Prokr2 have been shown to present abnormal olfactory bulb formation as well as defects in GnRH neuron migration. Patients carrying mutations in PROKR2 typically present hypogonadotropic hypogonadism, anosmia/hyposmia or Kallmann Syndrome. More recently variants in PROKR2 have been linked to several other endocrine disorders. In particular, several patients with pituitary disorders have been reported, ranging from mild phenotypes, such as isolated growth hormone deficiency, to more severe ones, such as septo-optic dysplasia. Here we summarize the changing landscape of PROKR2-related disease, the variants reported to date, and discuss their origin, classification and functional assessment.

Serine Proteases and Their Inhibitors Affect the Rate of GnRH Neuronal Migration in the Embryonic Chick Model: A Thesis Proposal

Development in an organism is a highly complex task that requires a specific sequence for proper function. One of these tasks is neuronal migration and the extracellular cues that help to guide neurons to their appropriate locations. If neurons do not migrate to their appropriate locations, then there are abnormal neural connections, which can result in neuronal migration disorders (NMD). It has been shown that the inhibition and stimulation of migration may be balanced due to effects of serine protease inhibitors and serine proteases. Serine proteases and their inhibitors can alter the various chemoattraction-signaling cues and thereby modulate neuronal migratory processes. Furthermore, there exists a delicate balance between serine proteases and their inhibitors to modulate migration of neurons within development. Thus, by understanding how the balance of serine protease and serine protease inhibitor activity works, one can further understand how these changes affect neuronal migration in development. Experiments to test in vivo neuronal migration of chick GnRH neurons during embryogenesis were investigated to elucidate the role these proteins play in migration. Protein coated beads were inserted and GnRH levels measured to control. Such experimentation is crucial, as these studies are the first to explore the role of proteases in neural migration in an in vivo model. These findings indicate that the ability to initiate migration lies inherently within the neuron itself such that changes of the extracellular matrix composition are irrelevant in the initial timing. Neurons entering the CNS earlier in trypsin-treated embryos indicates continuous movement may be a cell autonomous event with trypsin-induced proteolysis. In other words, the ability of GnRH neurons to migrate across glial boundaries and through the brain to its target site is independent of further maturation of the neuron or the brain. Taken together, this study can provide knowledge regarding these proteins and their relation to development. This knowledge can potentially lead to therapies that can provide ameliorative care for patients suffering with NMD.

Multiple gonadotropin-releasing hormone systems in non-mammalian vertebrates: Ontogeny, anatomy, and physiology.

Three paralogous genes for gonadotropin-releasing hormone (GnRH; gnrh1, gnrh2, and gnrh3) and GnRH receptors exist in non-mammalian vertebrates. However, there are some vertebrate species in which one or two of these paralogous genes have become non-functional during evolution. The developmental migration of GnRH neurons in the brain is evolutionarily conserved in mammals, reptiles, birds, amphibians, and jawed teleost fish. The three GnRH paralogs have specific expression patterns in the brain and originate from multiple sites. In acanthopterygian teleosts (medaka, cichlid, etc.), the preoptic area (POA)-GnRH1 and terminal nerve (TN)-GnRH3 neuronal types originate from the olfactory regions. In other fish species (zebrafish, goldfish and salmon) with only two GnRH paralogs (GnRH2 and GnRH3), the TN- and POA-GnRH3 neuronal types share the same olfactory origin. However, the developmental origin of midbrain (MB)-GnRH2 neurons is debatable between mesencephalic or neural crest site. Each GnRH system has distinctive anatomical and physiological characteristics, and functions differently. The POA-GnRH1 neurons are hypophysiotropic in nature and function in the neuroendocrine control of reproduction. The non-hypophysiotropic GnRH2/GnRH3 neurons probably play neuromodulatory roles in metabolism (MB-GnRH2) and the control of motivational state for sexual behavior (TN-GnRH3).

Discovery of a Novel Variant of SEMA3A in a Chinese Patient with Isolated Hypogonadotropic Hypogonadism.

Semaphorin (SEMA) has an important role in nerve development, organ formation, immune response, angiogenesis, and tumor growth. SEMA can regulate the growth and branching of axons, the morphology of dendrites, and the migration of neurons. The loss-of-function in SEMA and its receptors PLXNs and NRP affect the migration of GnRH neurons, leading to idiopathic hypogonadotropic hypogonadism (IHH). As a member of the SEMA family, SEMA3A has an important role in axonal rejection, dendritic branching, synaptic formation, and neuronal migration. There are more and more SEMA3A variants identified in IHH patients. In this study, we identified a novel SEMA3A variant (c.1369A > G (p.T457A)) in a male nIHH patient. Functional studies indicated that the T457A SEMA3A variant led to the defect of FAK phosphorylation and GN11 cell migration, which strongly argued in favor of its pathogenic effect in the nIHH patient. Our findings substantiated that the 435–457 position of SEMA3A might be very important for the secretion of SEMA3A. Haploin-sufficiency of SEMA3A in humans was sufficient to cause the IHH phenotype. SEMA3A variants might have a role in modifying the IHH phenotype, according to the variants at different positions of SEMA3A. SEMAs and its receptors formed a complex network, and other members of the SEMA-signaling pathway might also be involved in the pathogenesis of IHH.

Hypogonadotropic-hypogonadism (Kallman Syndrome) in Young Adult

Background: Kallmann syndrome (KS) is a rare disorder first described in 1856 and later studied by Kallmann in 1944. It is now designated as olfactogenital dysplasia with an association between agenesis of the olfactory bulbs and hypogonadism. The prevalence of KS is still unknown. The reported incidence is 1 in 8000 to 1 in 10 000 in men and rare in women. More than 24 genes are underlying KS that have been identified. Mutations in these genes are thought to interfere with the expression of cell markers that guide migrating neurons, leading to failed migration of GnRH neurons and olfactory neurons to the forebrain during fetal development. The main clinical characteristics of KS include hypogonadotropic hypogonadism and anosmia or hyposmia. Less common phenotypes include cardiovascular anomalies, unilateral renal agenesis, cleft palate and cleft lip, cryptorchidism and osteoporosis. Magnetic resonance imaging (MRI) can show abnormalities of the olfactory system and other forebrain structures. Other exceptions may be discovered using MRI because of its high resolution and multiplanar capabilities, such as pituitary abnormalities.

Screening of interacting proteins of idiopathic gonadotropin-releasing hormone deficiency pathogenic gene RNF216

To screen proteins interacting with ring finger protein 216(RNF216) through yeast two hybrid experiment, and further clarify the role of RNF216 in the pathogenesis of gonadotropin-releasing hormone deficiency. A recombinant expression vector pGBKT7-RNF216 was constructed and transformed into yeast Y2HGold, which was hybridized with a human cDNA library in order to screen proteins interacting with RNF216. The interaction was verified in yeast Y2HGold. A recombinant expression vector pGBKT7-RNF216 was successfully constructed and expressed in yeast Y2HGold. Filamin B (FLNB) was identified by yeast two hybrid experiment, and their interaction was verified in yeast Y2HGold. An interaction between FLNB and RNF216 was identified through yeast two hybrid experiment. RNF216 may affect the proliferation and migration of GnRH neurons by regulating FLNB or FLNB/FLNA heterodimers.

Defects in the GnRH Neuronal Migration factor, CCDC141, Lead to Self-Limited Delayed Puberty

GnRH neuronal biology has been identified as a critical element in the pathogenesis of self-limited DP, previously implicated exclusively in the pathophysiology of idiopathic hypogonadotropic hypogonadism (IHH). We hypothesise that this condition may be inherited via genetic variants discoverable through whole-exome sequencing (WES), by focusing on genes involved in GnRH neuron development and function, and genes reported in IHH. We analysed WES data from large Finnish cohort with familial self-limited DP, focusing on genes recently reported in IHH. WES data of 100 DP families have been analysed with a total of 193 individuals: 100 probands, 158 affected and 35 unaffected family members. Potentially pathogenic rare variants segregating within cohort families were identified using a virtual panel of recently reported IHH genes (n=13). This analysis identified 6 rare potentially pathogenic variants in CCDC141 in 25 individuals of 8 families which account for almost 10% of self-limited DP cases in this cohort, without variants identified in cohort control cases. Previous studies reported that homozygous or compound heterozygous mutations of CCDC141 cause Kallmann syndrome and IHH, due to impaired GnRH neuronal migration. In this study, all 6 CCDC141 variants were heterozygous missense variants predicted to be deleterious by in silico prediction tools. Most probands were male (n=7) with typical features of self-limited DP, with absence of secondary sexual characteristics, delayed bone age, and low gonadotropins and sex steroids at first presentation and spontaneous entry into puberty later than age of 14 years without treatment. The majority of pedigrees displayed good segregation of variants with the DP trait, following an autosomal dominant inheritance pattern. However, in two families, there was a complex inheritance pattern with compound heterozygosity (p.Ser55Cys and p.Asp767Asn) and possible incomplete penetrance. In vitro study showed that the overexpression of four key CCDC141 variants in HEK293 cells delayed cell migration, 72% in p.Ser55Cys (p=0.04), 66% in p.Gln507His (p=0.04), 65% in p.Asp767Asn (p=0.02), and 83% in p.Ala1073Thr (p=0.01), when compared to WT (100%). Moreover, WT-overexpressed cells increased the rate of cell migration when compared to non-transfected cells (100% vs 65%, p=0.005), reaffirming that CCDC141 has a role in cell migration. In conclusion, heterozygous deficiency of CCDC141, previously reported to cause IHH, can cause self-limited DP due to abnormal GnRH migration during foetal development.

Adult Onset Isolated Hypogonadotropic Hypogonadism- a Cause of Secondary Amenorrhea

A 23-year-old African American female was referred for secondary amenorrhea evaluation. She attained menarche at 12 years and had regular menses. At 18 years, she used OCPs for few months, and used plan B, after which her menses stopped. She had hot flashes and sweating. She was placed on progesterone, but never had withdrawal bleeding. Review of systems was positive for intentional weight loss after her menses stopped, hair loss and nipple discharge. She denied any loss of sensation of smell. She has a PMH of asthma, anxiety and OSA. Family history was not significant for any fertility issues. She smoked cannabis after menses stopped. On physical examination, vitals were stable, BMI of 35 kg/meter2, well-developed secondary sexual characteristics, no thyromegaly, acne or hirsutism. Upon work up, CBC, CMP were normal, Urine pregnancy test was negative, gonadotropins were undetectable (FSH- <0.7mIU/ml, LH- <0.2mIU/ml), anti-mullerian hormone was 3.82ng/ml (WNL), Estradiol was also absent (<15pg/ml), with a low Total testosterone (11ng/dl), TSH was 1.17uIU/ml, Free T4 was 1.1ng/dl, ACTH was 9.58pg/ml, Cortisol was 14.8mcg/dl, and Prolactin was 1.5ng/ml. MRI brain was normal with normal pituitary gland, no focal lesion visualized. Pelvic ultrasound showed ovaries 5.9mL and 4.6mL with multiple follicles present bilaterally. Diagnosis of adult-onset isolated hypogonadotropic hypogonadism (IHH) was made. Patient was started on estradiol patches and progesterone. IHH is a genetic disorder of defective production or action of GnRH. IHH when associated with anosmia is called Kallmann syndrome. It was first described by German American geneticist Joseph Kallmann in 1944. GnRH is a decapeptide, produced in arcuate nucleus and pre-optic nucleus of hypothalamus. GnRH stimulates anterior pituitary to secrete FSH and LH. IHH is caused due to impaired migration of GnRH neurons to brain during embryogenesis. It is inherited as autosomal or X-linked dominant or recessive. Gene mutations associated are ANOS-1, FGFR, PROK-2. It is rare in females. IHH has a broad spectrum of clinical presentation from complete absence of sexual development to partial completion of puberty. It presents with microphallus, cryptorchidism, cleft lip/palate, syndactyly, renal aplasia. In childhood presents with anosmia, hearing deficits, dental agenesis, mirror movements, short stature. During puberty, absent pubertal growth spurt, amenorrhea, lack of virilization, no secondary sexual characteristics, infertility. In partial forms, known as Adult onset or acquired form of IHH, patients have slight testicular growth, thelarche, menarche. Goals of treatment are- pubertal induction, maintenance of sexual maturation and restoration of fertility. In females, pre-puberty only estrogen is given, after puberty both estrogen and progesterone are used, for fertility, pulsatile gonadotropins or GnRH analogues are used.

Synaptic communication mediates the assembly of a self-organizing circuit that controls reproduction.

Migration of gonadotropin-releasing hormone (GnRH) neurons from their birthplace in the nasal placode to their hypothalamic destination is critical for vertebrate reproduction and species persistence. While their migration mode as individual GnRH neurons has been extensively studied, the role of GnRH-GnRH cell communication during migration remains largely unexplored. Here, we show in awake zebrafish larvae that migrating GnRH neurons pause at the nasal-forebrain junction and form clusters that act as interhemisphere neuronal ensembles. Within the ensembles, GnRH neurons create an isolated, spontaneously active circuit that is internally wired through monosynaptic glutamatergic synapses into which newborn GnRH neurons integrate before entering the brain. This initial phase of integration drives a phenotypic switch, which is essential for GnRH neurons to properly migrate toward their hypothalamic destination. Together, these experiments reveal a critical step for reproduction, which depends on synaptic communication between migrating GnRH neurons.

7. Puberty

Preface: In the puberty field this year, several high impact basic studies highlighted the role of neurotrophic factors and microRNA in GnRH neuron migration and activation around puberty. Fascinating discoveries were made regarding the transcriptome of developing GnRH neurons and testicular cells.

Prokineticin receptor 2 affects GnRH3 neuron ontogeny but not fertility in zebrafish

Prokineticin receptors (PROKR1 and PROKR2) are G protein-coupled receptors which control human central and peripheral reproductive processes. Importantly, allelic variants of PROKR2 in humans are associated with altered migration of GnRH neurons, resulting in congenital hypogonadotropic hypogonadism (CHH), a heterogeneous disease characterized by delayed/absent puberty and/or infertility. Although this association is established in humans, murine models failed to fully recapitulate the reproductive and olfactory phenotypes observed in patients harboring PROKR2 mutations. Here, taking advantage of zebrafish model we investigated the role of prokr1b (ortholog of human PROKR2) during early stages of GnRH neuronal migration. Real-Time PCR and whole mount in situ hybridization assays indicate that prokr1b spatial-temporal expression is consistent with gnrh3. Moreover, knockdown and knockout of prokr1b altered the correct development of GnRH3 fibers, a phenotype that is rescued by injection of prokr1b mRNA. These results suggest that prokr1b regulates the development of the GnRH3 system in zebrafish. Analysis of gonads development and mating experiments indicate that prokr1b is not required for fertility in zebrafish, although its loss determine changes also at the testis level. Altogether, our results support the thesis of a divergent evolution in the control of vertebrate reproduction and provide a useful in vivo model for deciphering the mechanisms underlying the effect of PROKR2 allelic variants on CHH.

PLXNA1 and PLXNA3 cooperate to pattern the nasal axons that guide gonadotropin-releasing hormone neurons.

Gonadotropin-releasing hormone (GnRH) neurons regulate puberty onset and sexual reproduction by secreting GnRH to activate and maintain the hypothalamic-pituitary-gonadal axis. During embryonic development, GnRH neurons migrate along olfactory and vomeronasal axons through the nose into the brain, where they project to the median eminence to release GnRH. The secreted glycoprotein SEMA3A binds its receptors neuropilin (NRP) 1 or NRP2 to position these axons for correct GnRH neuron migration, with an additional role for the NRP co-receptor PLXNA1. Accordingly, mutations in SEMA3A, NRP1, NRP2 and PLXNA1 have been linked to defective GnRH neuron development in mice and inherited GnRH deficiency in humans. Here, we show that only the combined loss of PLXNA1 and PLXNA3 phenocopied the full spectrum of nasal axon and GnRH neuron defects of SEMA3A knockout mice. Together with Plxna1, the human orthologue of Plxna3 should therefore be investigated as a candidate gene for inherited GnRH deficiency.

The Genetic Basis of Delayed Puberty.

Delayed pubertal onset has many etiologies, but on average two-thirds of patients presenting with late puberty have self-limited (or constitutional) delayed puberty. Self-limited delayed puberty often has a strong familial basis. Segregation analyses from previous studies show complex models of inheritance, most commonly autosomal dominant, but also including autosomal recessive, bilineal, and X-linked. Sporadic cases are also observed. Despite this, the neuroendocrine mechanisms and genetic regulation remain unclear in the majority of patients with self-limited delayed puberty. Only rarely have mutations in genes known to cause aberrations of the hypothalamic-pituitary-gonadal axis been identified in cases of delayed puberty, and the majority of these are in relatives of patients with congenital hypogonadotropic hypogonadism (CHH), for example in the FGFR1 and GNRHR genes. Using next generation sequencing in a large family with isolated self-limited delayed puberty, a pathogenic mutation in the CHH gene HS6ST1 was found as the likely cause for this phenotype. Additionally, a study comparing the frequency of mutations in genes that cause GnRH deficiency between probands with CHH and probands with isolated self-limited delayed puberty identified that a significantly higher proportion of mutations with a greater degree of oligogenicity were seen in the CHH group. Mutations in the gene IGSF10 have been implicated in the pathogenesis of familial late puberty in a large Finnish cohort. IGSF10 disruption represents a fetal origin of delayed puberty, with dysregulation of GnRH neuronal migration during embryonic development presenting for the first time in adolescence as late puberty. Some patients with self-limited delayed puberty have distinct constitutional features of growth and puberty. Deleterious variants in FTO have been found in families with delayed puberty with extremely low BMI and maturational delay in growth in early childhood. Recent exciting evidence highlights the importance of epigenetic up-regulation of GnRH transcription by a network of miRNAs and transcription factors, including EAP1, during puberty. Whilst a fascinating heterogeneity of genetic defects have been shown to result in delayed and disordered puberty, and many are yet to be discovered, genetic testing may become a realistic diagnostic tool for the differentiation of conditions of delayed puberty.

OR32-3 Kisspeptin- a Novel Clinical Test of Hypothalamic Function in Men with Hypogonadotrophic Hypogonadism

Background: Hypogonadotrophic Hypogonadism is characterised by hypogonadism in the context of low / inappropriately normal gonadotrophin levels. Congenital HH (CHH) occurs due to defective hypothalamic GnRH neuronal migration (e.g. Kallman’s syndrome), or secretion. However, no direct test of hypothalamic GnRH neuronal function currently exists. Kisspeptin is a neuropeptide that stimulates endogenous hypothalamic GnRH release. Thus, we investigated whether kisspeptin could be used to interrogate hypothalamic function in men with CHH. Methods: Men with CHH (low testosterone, low LH/FSH, normal MRI pituitary / baseline pituitary function, absent puberty, unprimed by pulsatile GnRH; n=4) and healthy eugonadal men (n=20) received an intravenous bolus of GnRH (100mcg), or kisspeptin-54 (6.4nmol/kg), on two study visits ≥1 week apart. Serum gonadotrophins were measured every 15mins for 6hrs following injection. Increases in serum gonadotrophins from baseline following GnRH / kisspeptin in eugonadal men and CHH were compared by unpaired t test. Results: Mean increase in serum LH from baseline was 8.2±3.8iU/L in eugonadal men and 0.12±0.13iU/L in CHH (P=0.0003) following kisspeptin administration. All eugonadal men had an LH increase >1.5iU/L, whereas all men with CHH had an LH increase <1.5iU/L following kisspeptin. In contrast, mean increase in serum LH from baseline following GnRH was 6.2±3.2iU/L in eugonadal men and 2.2±3.8iU/L in CHH (P=0.062). Therefore, whilst the kisspeptin-induced LH increase effectively discriminated men with HH from eugonadal men (area under ROC 1.0), GnRH-induced LH increase was less discriminatory (area under ROC 0.82). In eugonadal men, the maximal increase in LH following kisspeptin significantly predicted the maximal increase in LH following GnRH (univariate linear regression, r2=0.45; P=0.0013), however this relationship was lost in men with HH (r2=0.03; P=0.83). Conclusion: Collectively, these data confirm that a novel kisspeptin test of hypothalamic GnRH function can better discriminate men with CHH from eugonadal men than currently available investigations (such as GnRH test). Therefore, a kisspeptin test could offer significant clinical benefit for the accurate diagnosis and management of patients with hypogonadism.