Molecular pathogenesis of Kallmann's syndrome

Retroviral lineage analysis reveals dual contribution from ectodermal placodes and neural crest cells to avian olfactory sensory and GnRH neurons

The origin of the neurons and glia in the olfactory system of vertebrates has been controversial, with different cell types attributed to being of ectodermal placode versus neural crest lineage, depending upon the species. Here, we use replication incompetent avian (RIA) retroviruses to perform prospective cell lineage analysis of either presumptive olfactory placode or neural crest cells during early development of the chick embryo. Surprisingly, the results reveal a dual contribution from both the olfactory placode and neural crest cells to sensory neurons in the nose and Gonadotropin Releasing Hormone (GnRH) neurons migrating to the olfactory bulb. We also confirm that olfactory ensheathing glia are solely derived from the neural crest. Finally, our results show that neural crest cells and olfactory placode cells contribute to p63 positive cells, likely to be basal stem cells of the olfactory epithelium. Taken together, these finding provide evidence for previously unknown contributions of neural crest cells to some cell types in the chick olfactory system and help resolve previous discrepancies in the literature.

Successful pregnancy and delivery after a vitrified-warmed embryo transfer in a woman with Kallmann syndrome: A case report and literature review

Kallmann syndrome, a congenital disorder of idiopathic hypogonadotropic hypogonadism associated with anosmia, results in infertility because of anovulation. Assisted reproductive technology (ART) is considered when optimal ovulation induction therapy is difficult or when several cycles of ovulation induction therapy do not result in pregnancy. However, evidence is lacking regarding the optimal ART treatment for Kallmann syndrome. We report the case of a 33-year-old woman who successfully achieved pregnancy and delivery after ART treatment. At 29 years old, she was diagnosed with Kallmann syndrome due to hypothalamic amenorrhea and anosmia. At 33 years old, she revisited the hospital, desiring a child after one year of infertility. Due to anovulation, she was treated with gonadotropin therapy, but controlling follicular development was difficult, and thus ART treatment was initiated. The controlled ovarian stimulation (COS) protocol for ART treatment employed gonadotropins, recombinant follicular stimulating hormone/human menopausal gonadotropin plus human chorionic gonadotropin, to promote follicular growth. Four oocytes were retrieved, and two cleaved embryos were vitrified and cryopreserved. After vitrified-warmed embryo transfer of a morula stage embryo in a hormone replacement cycle, pregnancy was achieved but resulted in a miscarriage. A second oocyte retrieval was performed under the same COS; four oocytes were retrieved, and two cleaved embryos were vitrified and cryopreserved. Further, a pregnancy was achieved through the vitrified warmed embryo transfer. At 40 weeks and 6 days of gestation, a baby boy weighing 3,344 g with an Apgar score of 7/8 was delivered vaginally. The mother’s postpartum course and neonate were free from adverse events. For women with Kallmann syndrome, ART treatment and selective embryo cryopreservation may be a reasonable and safe option.

Mechanisms of Reciprocal Regulation of Gonadotropin-Releasing Hormone (GnRH)-Producing and Immune Systems: The Role of GnRH, Cytokines and Their Receptors in Early Ontogenesis in Normal and Pathological Conditions

Different aspects of the reciprocal regulatory influence on the development of gonadotropin-releasing hormone (GnRH)-producing- and immune systems in the perinatal ontogenesis and their functioning in adults in normal and pathological conditions are discussed. The influence of GnRH on the development of the immune system, on the one hand, and the influence of proinflammatory cytokines on the development of the hypothalamic-pituitary-gonadal system, on the other hand, and their functioning in adult offspring are analyzed. We have focused on the effects of GnRH on the formation and functional activity of the thymus, as the central organ of the immune system, in the perinatal period. The main mechanisms of reciprocal regulation of these systems are discussed. The reproductive health of an individual is programmed by the establishment and development of physiological systems during critical periods. Regulatory epigenetic mechanisms of development are not strictly genetically controlled. These processes are characterized by a high sensitivity to various regulatory factors, which provides possible corrections for disorders.

Genome-Wide Association Studies of Schizophrenia and Bipolar Disorder in a Diverse Cohort of US Veterans

BACKGROUND

Schizophrenia (SCZ) and bipolar disorder (BIP) are debilitating neuropsychiatric disorders, collectively affecting 2% of the world's population. Recognizing the major impact of these psychiatric disorders on the psychosocial function of more than 200 000 US Veterans, the Department of Veterans Affairs (VA) recently completed genotyping of more than 8000 veterans with SCZ and BIP in the Cooperative Studies Program (CSP) #572.

METHODS

We performed genome-wide association studies (GWAS) in CSP #572 and benchmarked the predictive value of polygenic risk scores (PRS) constructed from published findings. We combined our results with available summary statistics from several recent GWAS, realizing the largest and most diverse studies of these disorders to date.

RESULTS

Our primary GWAS uncovered new associations between CHD7 variants and SCZ, and novel BIP associations with variants in Sortilin Related VPS10 Domain Containing Receptor 3 (SORCS3) and downstream of PCDH11X. Combining our results with published summary statistics for SCZ yielded 39 novel susceptibility loci including CRHR1, and we identified 10 additional findings for BIP (28 326 cases and 90 570 controls). PRS trained on published GWAS were significantly associated with case-control status among European American (P < 10-30) and African American (P < .0005) participants in CSP #572.

CONCLUSIONS

We have demonstrated that published findings for SCZ and BIP are robustly generalizable to a diverse cohort of US veterans. Leveraging available summary statistics from GWAS of global populations, we report 52 new susceptibility loci and improved fine-mapping resolution for dozens of previously reported associations.

Delayed Puberty-Phenotypic Diversity, Molecular Genetic Mechanisms, and Recent Discoveries

This review presents a comprehensive discussion of the clinical condition of delayed puberty, a common presentation to the pediatric endocrinologist, which may present both diagnostic and prognostic challenges. Our understanding of the genetic control of pubertal timing has advanced thanks to active investigation in this field over the last two decades, but it remains in large part a fascinating and mysterious conundrum. The phenotype of delayed puberty is associated with adult health risks and common etiologies, and there is evidence for polygenic control of pubertal timing in the general population, sex-specificity, and epigenetic modulation. Moreover, much has been learned from comprehension of monogenic and digenic etiologies of pubertal delay and associated disorders and, in recent years, knowledge of oligogenic inheritance in conditions of GnRH deficiency. Recently there have been several novel discoveries in the field of self-limited delayed puberty, encompassing exciting developments linking this condition to both GnRH neuronal biology and metabolism and body mass. These data together highlight the fascinating heterogeneity of disorders underlying this phenotype and point to areas of future research where impactful developments can be made.

Deletion of the Homeodomain Protein Six6 From GnRH Neurons Decreases GnRH Gene Expression, Resulting in Infertility

Hypothalamic GnRH (luteinizing hormone-releasing hormone) neurons are crucial for the hypothalamic-pituitary-gonadal (HPG) axis, which regulates mammalian fertility. Insufficient GnRH disrupts the HPG axis and is often associated with the genetic condition idiopathic hypogonadotropic hypogonadism (IHH). The homeodomain protein sine oculis-related homeobox 6 (Six6) is required for the development of GnRH neurons. Although it is known that Six6 is specifically expressed within a more mature GnRH neuronal cell line and that overexpression of Six6 induces GnRH transcription in these cells, the direct role of Six6 within the GnRH neuron in vivo is unknown. Here we find that global Six6 knockout (KO) embryos show apoptosis of GnRH neurons beginning at embryonic day 14.5 with 90% loss of GnRH neurons by postnatal day 1. We sought to determine whether the hypogonadism and infertility reported in the Six6KO mice are generated via actions within the GnRH neuron in vivo by creating a Six6-flox mouse and crossing it with the LHRHcre mouse. Loss of Six6 specifically within the GnRH neuron abolished GnRH expression in ∼0% of GnRH neurons. We further demonstrated that deletion of Six6 only within the GnRH neuron leads to infertility, hypogonadism, hypogonadotropism, and delayed puberty. We conclude that Six6 plays distinct roles in maintaining fertility in the GnRH neuron vs in the migratory environment of the GnRH neuron by maintaining expression of GnRH and survival of GnRH neurons, respectively. These results increase knowledge of the role of Six6 in the brain and may offer insight into the mechanism of IHH.

Haploinsufficiency of SIX3 Abolishes Male Reproductive Behavior Through Disrupted Olfactory Development, and Impairs Female Fertility Through Disrupted GnRH Neuron Migration

Mating behavior in males and females is dependent on olfactory cues processed through both the main olfactory epithelium (MOE) and the vomeronasal organ (VNO). Signaling through the MOE is critical for the initiation of male mating behavior, and the loss of MOE signaling severely compromises this comportment. Here, we demonstrate that dosage of the homeodomain gene Six3 affects the degree of development of MOE but not the VNO. Anomalous MOE development in Six3 heterozygote mice leads to hyposmia, specifically disrupting male mounting behavior by impairing detection of volatile female estrus pheromones. Six3 is highly expressed in the MOE, main olfactory bulb (MOB), and hypothalamus; all regions essential in the proper migration of the gonadotropin-releasing hormone (GnRH) neurons, a key reproductive neuronal population that migrates along olfactory axons from the developing nose into the brain. Interestingly, we find that the reduction in Six3 expression in Six3 heterozygote mice compromises development of the MOE and MOB, resulting in mis-migration of GnRH neurons due to improper olfactory axon targeting. This reduction in the hypothalamic GnRH neuron population, by 45% in adulthood, leads to female subfertility, but does not impact male hormone levels, suggesting that male infertility is not related to GnRH neuron numbers, but exclusively linked to abnormal olfaction. We here determine that Six3 is haploinsufficient for MOE development, GnRH neuron migration, and fertility, and represents a novel candidate gene for Kallmann syndrome, a form of inherited infertility.

HS6ST1 Insufficiency Causes Self-Limited Delayed Puberty in Contrast With Other GnRH Deficiency Genes

CONTEXT

Self-limited delayed puberty (DP) segregates in an autosomal-dominant pattern, but the genetic basis is largely unknown. Although DP is sometimes seen in relatives of patients with hypogonadotropic hypogonadism (HH), mutations in genes known to cause HH that segregate with the trait of familial self-limited DP have not yet been identified.

OBJECTIVE

To assess the contribution of mutations in genes known to cause HH to the phenotype of self-limited DP.

DESIGN, PATIENTS, AND SETTING

We performed whole-exome sequencing in 67 probands and 93 relatives from a large cohort of familial self-limited DP, validated the pathogenicity of the identified gene variant in vitro, and examined the tissue expression and functional requirement of the mouse homolog in vivo.

RESULTS

A potentially pathogenic gene variant segregating with DP was identified in 1 of 28 known HH genes examined. This pathogenic variant occurred in HS6ST1 in one pedigree and segregated with the trait in the six affected members with heterozygous transmission (P = 3.01 × 10-5). Biochemical analysis showed that this mutation reduced sulfotransferase activity in vitro. Hs6st1 mRNA was expressed in peripubertal wild-type mouse hypothalamus. GnRH neuron counts were similar in Hs6st1+/- and Hs6st1+/+ mice, but vaginal opening was delayed in Hs6st1+/- mice despite normal postnatal growth.

CONCLUSIONS

We have linked a deleterious mutation in HS6ST1 to familial self-limited DP and show that heterozygous Hs6st1 loss causes DP in mice. In this study, the observed overlap in potentially pathogenic mutations contributing to the phenotypes of self-limited DP and HH was limited to this one gene.

Neuroanatomical and molecular correlates of cognitive and behavioural outcomes in hypogonadal males

Robust epidemiological, clinical and laboratory evidence supports emerging roles for the sex steroids in such domains as neurodevelopment, behaviour, learning and cognition. Regions of the mammalian brain that are involved in cognitive development and memory do not only express the classical nuclear androgen receptor, but also the non-genomic membrane receptor, which is a G protein-coupled receptor that mediates some rapid effects of the androgens on neurogenesis and synaptic plasticity. Under physiological conditions, hippocampal neurons do express the enzyme aromatase, and therefore actively aromatize testosterone to oestradiol. Although glial expression of the aromatase enzyme is minimal, increased expression following injury suggests a role for sex steroids in neuroprotection. It is therefore plausible to deduce that low levels of circulating androgens in males would perturb neuronal functions in relation to cognition and memory, as well as neural repair following injury. The present review is an overview of some roles of the sex steroids on cognitive function in males, and the neuroanatomical and molecular underpinnings of some behavioural and cognitive deficits characteristic of such genetic disorders noted for low androgen levels, including Klinefelter syndrome, Bardet-Biedl syndrome, Kallman syndrome and Prader-Willi syndrome. Recent literature in relation to some behavioural and cognitive changes secondary to surgical and pharmacological castration are also appraised.

Cell adhesion to anosmin via α5β1, α4β1, and α9β1 integrins

Anosmin is an extracellular matrix protein, and genetic defects in anosmin result in human Kallmann syndrome. It functions in neural crest formation, cell adhesion, and neuronal migration. Anosmin consists of multiple domains, and it has been reported to bind heparan sulfate, FGF receptor, and UPA. In this study, we establish cell adhesion/spreading assays for anosmin and use them for antibody inhibition analyses to search for an integrin adhesion receptor. We find that α5β1, α4β1, and α9β1 integrins are needed for effective adhesive receptor function in cell adhesion and cell spreading on anosmin; adhesion is inhibited by both RGD and α4β1 CS1-based peptides. This identification of anosmin-integrin adhesion receptors should facilitate studies of anosmin function in cell and developmental biology.

Chd7 is indispensable for mammalian brain development through activation of a neuronal differentiation programme

Mutations in chromatin modifier genes are frequently associated with neurodevelopmental diseases. We herein demonstrate that the chromodomain helicase DNA-binding protein 7 (Chd7), frequently associated with CHARGE syndrome, is indispensable for normal cerebellar development. Genetic inactivation of Chd7 in cerebellar granule neuron progenitors leads to cerebellar hypoplasia in mice, due to the impairment of granule neuron differentiation, induction of apoptosis and abnormal localization of Purkinje cells, which closely recapitulates known clinical features in the cerebella of CHARGE patients. Combinatory molecular analyses reveal that Chd7 is required for the maintenance of open chromatin and thus activation of genes essential for granule neuron differentiation. We further demonstrate that both Chd7 and Top2b are necessary for the transcription of a set of long neuronal genes in cerebellar granule neurons. Altogether, our comprehensive analyses reveal a mechanism with chromatin remodellers governing brain development via controlling a core transcriptional programme for cell-specific differentiation.

Arachnoid cyst: a further anomaly associated with Kallmann syndrome?

BACKGROUND

Kallmann syndrome (KS) is defined by the association of hypogonadotropic hypogonadism and anosmia. It is characterized by a significant clinical and genetic heterogeneity; actually, it may present several non-reproductive non-olfactory anomalies, and all the ways of genetic transmission can be involved in the inheritance of the disease. Although six pathogenesis-related genes have been identified so far, KS remains sporadic in 70 % of the cases, and the genetic diagnosis is not available for all of them. The purpose of this paper is to present a further disease that can enrich the wide spectrum of KS variability, that is cerebral arachnoid cyst.

CASE DESCRIPTION

This 11-year-old boy presented with the typical characteristics of KS together with those related to a sylvian arachnoid cyst. He was admitted because of worsening headache. At the admission, the physical examination revealed eunuchoid aspect, micropenis, previous cryptorchidism, and anosmia. MRI pointed out a large, left sylvian arachnoid cyst, agenesia of the olfactory bulbs/tracts complex, and hypoplasia of the left olfactory sulcus. The child was operated on by endoscopic fenestration of the cyst, followed by transient external drainage for subdural hygroma and microscopic fenestration for recurrence of the cyst. His statural growth is normal but the sexual development still delayed in spite of hormone replacement therapy.

CONCLUSION

According to the present and the other four cases in the literature, arachnoid cyst should be included among the anomalies possibly accompanying KS date although this association seems to be occasional as far as embryogenesis and physiopathology are concerned.

Pubertal development and regulation

Puberty marks the end of childhood and is a period when individuals undergo physiological and psychological changes to achieve sexual maturation and fertility. The hypothalamic-pituitary-gonadal axis controls puberty and reproduction and is tightly regulated by a complex network of excitatory and inhibitory factors. This axis is active in the embryonic and early postnatal stages of life and is subsequently restrained during childhood, and its reactivation culminates in puberty initiation. The mechanisms underlying this reactivation are not completely known. The age of puberty onset varies between individuals and the timing of puberty initiation is associated with several health outcomes in adult life. In this Series paper, we discuss pubertal markers, epidemiological trends of puberty initiation over time, and the mechanisms whereby genetic, metabolic, and other factors control secretion of gonadotropin-releasing hormone to determine initiation of puberty.

Enabling research with human embryonic and fetal tissue resources

Congenital anomalies are a significant burden on human health. Understanding the developmental origins of such anomalies is key to developing potential therapies. The Human Developmental Biology Resource (HDBR), based in London and Newcastle, UK, was established to provide embryonic and fetal material for a variety of human studies ranging from single gene expression analysis to large-scale genomic/transcriptomic studies. Increasingly, HDBR material is enabling the derivation of stem cell lines and contributing towards developments in tissue engineering. Use of the HDBR and other fetal tissue resources discussed here will contribute to the long-term aims of understanding the causation and pathogenesis of congenital anomalies, and developing new methods for their treatment and prevention.

Mutation analyses in pedigrees and sporadic cases of ethnic Han Chinese Kallmann syndrome patients

Kallmann syndrome, a form of idiopathic hypogonadotropic hypogonadism, is characterized by developmental abnormalities of the reproductive system and abnormal olfaction. Despite association of certain genes with idiopathic hypogonadotropic hypogonadism, the genetic inheritance and expression are complex and incompletely known. In the present study, seven Kallmann syndrome pedigrees in an ethnic Han Chinese population were screened for genetic mutations. The exons and intron-exon boundaries of 19 idiopathic hypogonadotropic hypogonadism (idiopathic hypogonadotropic hypogonadism)-related genes in seven Chinese Kallmann syndrome pedigrees were sequenced. Detected mutations were also tested in 70 sporadic Kallmann syndrome cases and 200 Chinese healthy controls. In pedigrees 1, 2, and 7, the secondary sex characteristics were poorly developed and the patients' sense of smell was severely or completely lost. We detected a genetic mutation in five of the seven pedigrees: homozygous KAL1 p.R191ter (pedigree 1); homozygous KAL1 p.C13ter (pedigree 2; a novel mutation); heterozygous FGFR1 p.R250W (pedigree 3); and homozygous PROKR2 p.Y113H (pedigrees 4 and 5). No genetic change of the assayed genes was detected in pedigrees 6 and 7. Among the 70 sporadic cases, we detected one homozygous and one heterozygous PROKR2 p.Y113H mutation. This mutation was also detected heterozygously in 2/200 normal controls and its pathogenicity is likely questionable. The genetics and genotype-phenotype relationships in Kallmann syndrome are complicated. Classical monogenic inheritance does not explain the full range of genetic inheritance of Kallmann syndrome patients. Because of stochastic nature of genetic mutations, exome analyses of Kallmann syndrome patients may provide novel insights.

The Dlx5 and Foxg1 transcription factors, linked via miRNA-9 and -200, are required for the development of the olfactory and GnRH system

During neuronal development and maturation, microRNAs (miRs) play diverse functions ranging from early patterning, proliferation and commitment to differentiation, survival, homeostasis, activity and plasticity of more mature and adult neurons. The role of miRs in the differentiation of olfactory receptor neurons (ORNs) is emerging from the conditional inactivation of Dicer in immature ORN, and the depletion of all mature miRs in this system. Here, we identify specific miRs involved in olfactory development, by focusing on mice null for Dlx5, a homeogene essential for both ORN differentiation and axon guidance and connectivity. Analysis of miR expression in Dlx5^−/− olfactory epithelium pointed to reduced levels of miR-9, miR-376a and four miRs of the -200 class in the absence of Dlx5. To functionally examine the role of these miRs, we depleted miR-9 and miR-200 class in reporter zebrafish embryos and observed delayed ORN differentiation, altered axonal trajectory/targeting, and altered genesis and position of olfactory-associated GnRH neurons, i.e. a phenotype known as Kallmann syndrome in humans. miR-9 and miR-200-class negatively control Foxg1 mRNA, a fork-head transcription factor essential for development of the olfactory epithelium and of the forebrain, known to maintain progenitors in a stem state. Increased levels of z-foxg1 mRNA resulted in delayed ORN differentiation and altered axon trajectory, in zebrafish embryos. This work describes for the first time the role of specific miR (-9 and -200) in olfactory/GnRH development, and uncovers a Dlx5–Foxg1 regulation whose alteration affects receptor neuron differentiation, axonal targeting, GnRH neuron development, the hallmarks of the Kallmann syndrome.

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Dlx5 controls the expressions of miR9 and miR-200, which target the Foxg1 mRNA

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miR-9 and -200 are needed for olfactory neurons differentiation and axon extension

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miR-9 and -200 are required for the genesis and position of GnRH neurons.

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Altered expression of miR-9 and -200 might contribute to the Kallmann disease.

Clinical, endocrinological, and molecular characterization of Kallmann syndrome and normosmic idiopathic hypogonadotropic hypogonadism: a single center experience

PURPOSE

Isolated gonadotropin-releasing hormone (GnRH) deficiency (IGD) is classified as Kallmann syndrome (KS) with anosmia and normosmic idiopathic hypogonadotropic hypogonadism (nIHH). This study was undertaken to investigate the clinical, endocrinological, and molecular characteristics in Korean patients with KS and nIHH.

METHODS

Twenty-six patients from 25 unrelated families were included. Their clinical, endocrinological, and radiological findings were analyzed retrospectively. Mutation analysis of the GNRH1, GNRHR, KISS1, KISS1R, PROK2, PROKR2, TAC3, TACR3, FGF8, FGFR1, and KAL1 genes was performed in all patients. CHD7 and SOX10 were analyzed in patients with CHARGE (Coloboma, Heart defects, choanae Atresia, Growth retardation, Genitourinary abnormality, Ear abnormality) features or deafness.

RESULTS

Of the 26 patients, 16 had KS and 10 had nIHH. At diagnosis, mean chronologic age was 18.1 years in males and 18.0 years in females; height SDS were -0.67±1.35 in males, -1.12±1.86 in females; testis volume was 2.0±1.3 mL; and Tanner stage was 1.5. There were associated anomalies in some of the KS patients: hearing loss (n=6) and congenital heart disease (n=4). Absence or hypoplasia of the olfactory bulb/sulci was found in 84.62% of patients with KS. Molecular defects in KAL1, SOX10, and CHD7 were identified in 5 patients from 4 families (16.0%, 4/25 pedigrees). After sex hormone replacement therapy, there were improvement in sexual characteristics and the sexual function.

CONCLUSION

This study described the clinical, endocrinological, and molecular genetic features in IGD patients in Korea. Although the mutation screening was performed in 10 genes that cause IGD, molecular defects were identified in relatively small proportions of the cohort.

Radial glia phagocytose axonal debris from degenerating overextending axons in the developing olfactory bulb

Axon targeting during the development of the olfactory system is not always accurate, and numerous axons overextend past the target layer into the deeper layers of the olfactory bulb. To date, the fate of the mis-targeted axons has not been determined. We hypothesized that following overextension, the axons degenerate, and cells within the deeper layers of the olfactory bulb phagocytose the axonal debris. We utilized a line of transgenic mice that expresses ZsGreen fluorescent protein in primary olfactory axons. We found that overextending axons closely followed the filaments of radial glia present in the olfactory bulb during embryonic development. Following overextension into deeper layers of the olfactory bulb, axons degenerated and radial glia responded by phagocytosing the resulting debris. We used in vitro analysis to confirm that the radial glia had phagocytosed debris from olfactory axons. We also investigated whether the fate of overextending axons was altered when the development of the olfactory bulb was perturbed. In mice that lacked Sox10, a transcription factor essential for normal olfactory bulb development, we observed a disruption to the morphology and positioning of radial glia and an accumulation of olfactory axon debris within the bulb. Our results demonstrate that during early development of the olfactory system, radial glia play an important role in removing overextended axons from the deeper layers of the olfactory bulb.

Heparan Sulfate Proteoglycans Regulate Fgf Signaling and Cell Polarity during Collective Cell Migration

Collective cell migration is a highly regulated morphogenetic movement during embryonic development and cancer invasion that involves the precise orchestration and integration of cell-autonomous mechanisms and environmental signals. Coordinated lateral line primordium migration is controlled by the regulation of chemokine receptors via compartmentalized Wnt/β-catenin and fibroblast growth factor (Fgf) signaling. Analysis of mutations in two exostosin glycosyltransferase genes (extl3 and ext2) revealed that loss of heparan sulfate (HS) chains results in a failure of collective cell migration due to enhanced Fgf ligand diffusion and loss of Fgf signal transduction. Consequently, Wnt/β-catenin signaling is activated ectopically, resulting in the subsequent loss of the chemokine receptor cxcr7b. Disruption of HS proteoglycan (HSPG) function induces extensive, random filopodia formation, demonstrating that HSPGs are involved in maintaining cell polarity in collectively migrating cells. The HSPGs themselves are regulated by the Wnt/β-catenin and Fgf pathways and thus are integral components of the regulatory network that coordinates collective cell migration with organ specification and morphogenesis.

A novel nonsense mutation of the KAL1 gene (p.Trp204*) in Kallmann syndrome

Objective

To describe a novel KAL1 mutation in patients affected by Kallmann syndrome.

Setting

Endocrinology Clinic of the João de Barros Barreto University Hospital – Federal University of Pará, Brazil.

Methods

Clinical examination, hormone assays and sequencing of exons 5, 6 and 9 of the KAL1 gene in four Brazilian brothers with Kallmann syndrome.

Results

Detected a novel KAL1 mutation, c.612G.A/p.Trp204*, in four hemizygous brothers with Kallmann syndrome, and five heterozygous female family members.

Conclusion

The novel p.Trp204* mutation of the KAL1 gene results in the production of a truncated anosmin-1 enzyme in patients with Kallmann syndrome. This finding broadens the spectrum of pathogenic mutations for this disease.

The optimal evaluation and management of patients with a gradual onset of olfactory loss

PURPOSE OF REVIEW

The aim of this review is to provide an overview of the causes of olfactory dysfunction, their evaluation and management, with a main focus on the gradual/progressive loss of smell.

RECENT FINDINGS

As the sense of smell gives us essential information about our environment, its loss can cause nutritional and social problems while threatening an individual's safety. Recent surveys have shown quite a substantial prevalence of hyposmia (one out of four people) and anosmia (one out of 200 people) in a variety of populations.

SUMMARY

Nasal inflammatory diseases such as allergic rhinitis and predominantly chronic rhinosinusitis account for the major and common causes of gradual/progressive loss of smell. However, they are also among the most successfully treated forms of olfactory dysfunction. The management of gradual/progressive smell deficit must always address its etiological causes. In most cases, a detailed medical history and nasal examination, smell testing, and imaging will help to establish an appropriate diagnosis. In addition to anti-inflammatory therapy, mainly nasal and systemic corticosteroids, recent investigations on smell training suggest that the controlled exposure to selected odors may increase olfactory performance.

VIDEO ABSTRACT AVAILABLE

See the Video Supplementary Digital Content 1 (http://links.lww.com/COOH/A8).

Renal agenesis in Kallmann syndrome: a network approach

Kallmann syndrome (KS) is defined by the combination of isolated hypogonadotrophic hypogonadism (IHH) and anosmia, with renal agenesis occurring in 30% of KS cases with KAL1 gene mutations. Unlike other KS-related disorders, renal agenesis cannot be directly associated with mutations in the KAL1 gene. We hypothesized that protein interaction networks may suggest a link between genes currently known to be associated with KS on the one hand and those associated with renal agenesis on the other hand. We created a STRING protein interaction network from KS-related genes and renal-agenesis-associated genes and analyzed it with Cytoscape 3.0.1 network software. The STRING protein interaction network provided a conceptual framework for current knowledge on the subject of renal morphogenesis in Kallmann syndrome. In addition, STRING and Cytoscape 3.0.1 software identified new potential KS renal-aplasia-associated genes (PAX2, BMP4, and SOX10). The use of protein-protein interaction networks and network analysis tools provided interesting insights and possible directions for future studies on the subject of renal aplasia in Kallmann syndrome.

The development of lateral line placodes: taking a broader view

The lateral line system of anamniote vertebrates enables the detection of local water movement and weak bioelectric fields. Ancestrally, it comprises neuromasts - small sense organs containing mechanosensory hair cells - distributed in characteristic lines over the head and trunk, flanked on the head by fields of electroreceptive ampullary organs, innervated by afferent neurons projecting respectively to the medial and dorsal octavolateral nuclei in the hindbrain. Given the independent loss of the electrosensory system in multiple lineages, the development and evolution of the mechanosensory and electrosensory components of the lateral line must be dissociable. Nevertheless, the entire system arises from a series of cranial lateral line placodes, which exhibit two modes of sensory organ formation: elongation to form sensory ridges that fragment (with neuromasts differentiating in the center of the ridge, and ampullary organs on the flanks), or migration as collectives of cells, depositing sense organs in their wake. Intensive study of the migrating posterior lateral line placode in zebrafish has yielded a wealth of information concerning the molecular control of migration and neuromast formation in this migrating placode, in this cypriniform teleost species. However, our mechanistic understanding of neuromast and ampullary organ formation by elongating lateral line placodes, and even of other zebrafish lateral line placodes, is sparse or non-existent. Here, we attempt to highlight the diversity of lateral line development and the limits of the current research focus on the zebrafish posterior lateral line placode. We hope this will stimulate a broader approach to this fascinating sensory system.

Genetics of the first seven proprotein convertase enzymes in health and disease

Members of the substilisin/kexin like proprotein convertase (PCSK) protease family cleave and convert immature pro-proteins into their biologically active forms. By cleaving for example prohormones, cytokines and cell membrane proteins, PCSKs participate in maintaining the homeostasis in a healthy human body. Conversely, erratic enzymatic function is thought to contribute to the pathogenesis of a wide variety of diseases, including obesity and hypercholestrolemia. The first characterized seven PCSK enzymes (PCSK1-2, FURIN, PCSK4-7) process their substrates at a motif made up of paired basic amino acid residues. This feature results in a variable degree of biochemical redundancy in vitro, and consequently, shared substrate molecules between the different PCSK enzymes. This redundancy has confounded our understanding of the specific biological functions of PCSKs. The physiological roles of these enzymes have been best illustrated by the phenotypes of genetically engineered mice and patients that carry mutations in the PCSK genes. Recent developments in genome-wide methodology have generated a large amount of novel information on the genetics of the first seven proprotein convertases. In this review we summarize the reported genetic alterations and their associated phenotypes.

Current issues in medically assisted reproduction and genetics in Europe: research, clinical practice, ethics, legal issues and policy. European Society of Human Genetics and European Society of Human Reproduction and Embryology

In March 2005, a group of experts from the European Society of Human Genetics and European Society of Human Reproduction and Embryology met to discuss the interface between genetics and assisted reproductive technology (ART), and published an extended background paper, recommendations and two Editorials. Seven years later, in March 2012, a follow-up interdisciplinary workshop was held, involving representatives of both professional societies, including experts from the European Union Eurogentest2 Coordination Action Project. The main goal of this meeting was to discuss developments at the interface between clinical genetics and ARTs. As more genetic causes of reproductive failure are now recognised and an increasing number of patients undergo testing of their genome before conception, either in regular health care or in the context of direct-to-consumer testing, the need for genetic counselling and preimplantation genetic diagnosis (PGD) may increase. Preimplantation genetic screening (PGS) thus far does not have evidence from randomised clinical trials to substantiate that the technique is both effective and efficient. Whole-genome sequencing may create greater challenges both in the technological and interpretational domains, and requires further reflection about the ethics of genetic testing in ART and PGD/PGS. Diagnostic laboratories should be reporting their results according to internationally accepted accreditation standards (International Standards Organisation - ISO 15189). Further studies are needed in order to address issues related to the impact of ART on epigenetic reprogramming of the early embryo. The legal landscape regarding assisted reproduction is evolving but still remains very heterogeneous and often contradictory. The lack of legal harmonisation and uneven access to infertility treatment and PGD/PGS fosters considerable cross-border reproductive care in Europe and beyond. The aim of this paper is to complement previous publications and provide an update of selected topics that have evolved since 2005.

Invertebrate models of kallmann syndrome: molecular pathogenesis and new disease genes

Kallmann Syndrome is a heritable disorder characterized by congenital anosmia, hypogonadotropic hypogonadism and, less frequently, by other symptoms. The X-linked form of this syndrome is caused by mutations affecting the KAL1 gene that codes for the extracellular protein anosmin-1. Investigation of KAL1 function in mice has been hampered by the fact that the murine ortholog has not been identified. Thus studies performed in other animal models have contributed significantly to an understanding of the function of KAL1. In this review, the main results obtained using the two invertebrate models, the nematode worm Caenorhabditis elegans and the fruit fly Drosophila melanogaster, are illustrated and the contribution provided by them to the elucidation of the molecular pathogenesis of Kallmann Syndrome is discussed in detail. Structure-function dissection studies performed in these two animal models have shown how the different domains of anosmin-1 carry out specific functions, also suggesting a novel intramolecular regulation mechanism among the different domains of the protein. The model that emerges is one in which anosmin-1 plays different roles in different tissues, interacting with different components of the extracellular matrix. We also describe how the genetic approach in C. elegans has allowed the discovery of the genes involved in KAL1-heparan sulfate proteoglycans interactions and the identification of HS6ST1 as a new disease gene.

Olfactory ensheathing glia are required for embryonic olfactory axon targeting and the migration of gonadotropin-releasing hormone neurons

Kallmann's syndrome is caused by the failure of olfactory axons and gonadotropin-releasing hormone (GnRH) neurons to enter the embryonic forebrain, resulting in anosmia and sterility. Sox10 mutations have been associated with Kallmann's syndrome phenotypes, but their effect on olfactory system development is unknown. We recently showed that Sox10 is expressed by neural crest-derived olfactory ensheathing cells (OECs). Here, we demonstrate that in homozygous Sox10(lacZ/lacZ) mouse embryos, OEC differentiation is disrupted; olfactory axons accumulate in the ventromedial olfactory nerve layer and fewer olfactory receptor neurons express the maturation marker OMP (most likely owing to the failure of axonal targeting). Furthermore, GnRH neurons clump together in the periphery and a smaller proportion enters the forebrain. Our data suggest that human Sox10 mutations cause Kallmann's syndrome by disrupting the differentiation of OECs, which promote embryonic olfactory axon targeting and hence olfactory receptor neuron maturation, and GnRH neuron migration to the forebrain.

Cognitive, behavioural and psychiatric phenotypes associated with steroid sulfatase deficiency

The enzyme steroid sulfatase (STS) desulfates a variety of steroid compounds thereby altering their activity. STS is expressed in the skin, and its deficiency in this tissue has been linked to the dermatological condition X-linked ichthyosis. STS is also highly expressed in the developing and adult human brain, and in a variety of steroidogenic organs (including the placenta and gonads); therefore it has the potential to influence brain development and function directly and/or indirectly (through influencing the hormonal milieu). In this review, we first discuss evidence from human and animal model studies suggesting that STS deficiency might predispose to neurobehavioural abnormalities and certain psychiatric disorders. We subsequently discuss potential mechanisms that may underlie these vulnerabilities. The data described herein have potential implications for understanding the complete spectrum of clinical phenotypes associated with X-linked ichthyosis, and may indicate novel pathogenic mechanisms underlying psychological dysfunction in developmental disorders such as attention deficit hyperactivity disorder and Turner syndrome.

Molecular biology of the kisspeptin receptor: signaling, function, and mutations

Kisspeptin receptor (KISS1R) signaling is essential for the hallmark increase in pulsatile GnRH secretion characteristic of the onset of puberty in humans and experimental animals. Loss-of-function mutations in KISS1R are associated with idiopathic hypogonadotropic hypogonadism in humans. Also, mutations with confirmed association with idiopathic central precocious puberty were identified in kisspeptin and KISS1R. These observations underscore the role of KISS1R signaling for normal pubertal development. Moreover, investigation of the mechanisms underlying the gain-of-function mutation in KISS1R indicates that the duration of KISS1R signaling is critical for the role of this receptor in timing the onset of puberty in humans. These findings further endorse the need to uncover the mechanisms, as well as yet-unknown proteins, involved in each step of KISS1R signaling. This knowledge is expected to advance our understanding of normal and abnormal pubertal development, as well as to help uncover the role of KISS1R signaling in non-hypothalamic tissues such as the placenta. This chapter discusses recent advances in the investigation of KISS1R signaling and function, as well as potential pathophysiological implications of naturally occurring mutations in this receptor identified in humans with reproductive disorders.

Profiling, Bioinformatic, and Functional Data on the Developing Olfactory/GnRH System Reveal Cellular and Molecular Pathways Essential for This Process and Potentially Relevant for the Kallmann Syndrome

During embryonic development, immature neurons in the olfactory epithelium (OE) extend axons through the nasal mesenchyme, to contact projection neurons in the olfactory bulb. Axon navigation is accompanied by migration of the GnRH+ neurons, which enter the anterior forebrain and home in the septo-hypothalamic area. This process can be interrupted at various points and lead to the onset of the Kallmann syndrome (KS), a disorder characterized by anosmia and central hypogonadotropic hypogonadism. Several genes has been identified in human and mice that cause KS or a KS-like phenotype. In mice a set of transcription factors appears to be required for olfactory connectivity and GnRH neuron migration; thus we explored the transcriptional network underlying this developmental process by profiling the OE and the adjacent mesenchyme at three embryonic ages. We also profiled the OE from embryos null for Dlx5, a homeogene that causes a KS-like phenotype when deleted. We identified 20 interesting genes belonging to the following categories: (1) transmembrane adhesion/receptor, (2) axon-glia interaction, (3) scaffold/adapter for signaling, (4) synaptic proteins. We tested some of them in zebrafish embryos: the depletion of five (of six) Dlx5 targets affected axonal extension and targeting, while three (of three) affected GnRH neuron position and neurite organization. Thus, we confirmed the importance of cell-cell and cell-matrix interactions and identified new molecules needed for olfactory connection and GnRH neuron migration. Using available and newly generated data, we predicted/prioritized putative KS-disease genes, by building conserved co-expression networks with all known disease genes in human and mouse. The results show the overall validity of approaches based on high-throughput data and predictive bioinformatics to identify genes potentially relevant for the molecular pathogenesis of KS. A number of candidate will be discussed, that should be tested in future mutation screens.

Molecular basis for the Kallmann syndrome-linked fibroblast growth factor receptor mutation

Kallmann syndrome (KS) is a developmental disease that expresses in patients as hypogonadotropic hypogonadism and anosmia. KS is commonly associated with mutations in the extracellular D2 domain of the fibroblast growth factor receptor (FGFR). In this study, for the first time, the molecular basis for the FGFR associated KS mutation (A168S) is elucidated using a variety of biophysical experiments, including multidimensional NMR spectroscopy. Secondary and tertiary structural analysis using far UV circular dichroism, fluorescence and limited trypsin digestion assays suggest that the KS mutation induces subtle tertiary structure change in the D2 domain of FGFR. Results of isothermal titration calorimetry experiments show the KS mutation causes a 10-fold decrease in heparin binding affinity and also a complete loss in ligand (FGF-1) binding. (1)H-(15)N chemical perturbation data suggest that complete loss in the ligand (FGF) binding affinity is triggered by a subtle conformational change that disrupts crucial structural interactions in both the heparin and the FGF binding sites in the D2 domain of FGFR. The novel findings reported in this study are expected to provide valuable clues toward a complete understanding of the other genetic diseases linked to mutations in the FGFR.

Kallmann syndrome in a female adolescent: a new mutation in the FGFR1 gene

The Kallmann syndrome is characterised by the association of hypogonadotropic hypogonadism and hypo/anosmia. It represents a phenotypically and genotypically heterogeneous clinical entity, with six genes identified so far in the literature-KAL1, FGFR1, PROKR2, PROK2, CHD7 and FGF8. Mutations in the FGFR1 gene can be found in approximately 10% of the patients. The authors present the case of a female adolescent with hypogonadotropic hypogonadism and impaired olfactory acuity in the presence of hypoplasia of the nasal sulcus and agenesis of the olfactory bulbs. The molecular analysis of the fibroblast growth factor receptor 1 identified a heterozygous mutation c.1377_78insA (p.V460SfsX3) in exon 10 of FGFR1 gene. This mutation has not yet been reported in the literature. A theoretical review of clinical features and therapeutic approach of this syndrome is also presented.

New understandings of the genetic basis of isolated idiopathic central hypogonadism

Idiopathic hypogonadotropic hypogonadism is a rare disease that is characterized by delayed/absent puberty and/or infertility due to an insufficient stimulation of an otherwise normal pituitary-gonadal axis by gonadotrophin-releasing hormone (GnRH) action. Because reduced or normal luteinizing hormone (LH)/follicle-stimulating hormone (FSH) levels may be observed in the affected patients, the term idiopathic central hypogonadism (ICH) appears to be more appropriate. This disease should be distinguished from central hypogonadism that is combined with other pituitary deficiencies. Isolated ICH has a complex pathogenesis and is fivefold more prevalent in males. ICH frequently appears in a sporadic form, but several familial cases have also been reported. This finding, in conjunction with the description of numerous pathogenetic gene variants and the generation of several knockout models, supports the existence of a strong genetic component. ICH may be associated with several morphogenetic abnormalities, which include osmic defects that, with ICH, constitute the cardinal manifestations of Kallmann syndrome (KS). KS accounts for approximately 40% of the total ICH cases and has been generally considered to be a distinct subgroup. However, the description of several pedigrees, which include relatives who are affected either with isolated osmic defects, KS, or normo-osmic ICH (nICH), justifies the emerging idea that ICH is a complex genetic disease that is characterized by variable expressivity and penetrance. In this context, either multiple gene variants or environmental factors and epigenetic modifications may contribute to the variable disease manifestations. We review the genetic mechanisms that are presently known to be involved in ICH pathogenesis and provide a clinical overview of the 227 cases that have been collected by the collaborating centres of the Italian ICH Network.

Expression patterns of the STAG gene in intact and regenerating planarians (Dugesia japonica)

We examined the spatial and temporal expression of the planarian Dugesia japonica STAG-related gene (DjStag), in both intact and regenerating planarians, by whole-mount in situ hybridization and relative quantitative real-time PCR. The first localized transcripts of DjStag were detected in the blastemas three days after amputation, in all regenerates including those from head, tail and trunk pieces. The maximum level of expression of DjStag transcripts occurred at five days after cutting. After regeneration for seven days, DjStag was weakly expressed. A similar decrease occurs regardless of the orientation of the cut. The expression pattern did not differ significantly in the different types of regeneration. Relative quantitative real-time PCR analysis of DjStag mRNA indicated that the expression of DjStag mRNA was increased after amputation compared to that in normal intact planarians, and the maximum level of expression of DjStag transcripts occurred at five days after amputation. All results suggest that DjStag, implicated in planarian regeneration, plays a role in maintaining the ability of pluripotent stem cells to regenerate lost tissue in planarians.

Cxcl12a-Cxcr4b signaling is important for proper development of the forebrain GnRH system in zebrafish

Hypothalamic gonadotropin-releasing hormone (GnRH) neurons control pituitary gonadotropin secretion and gametogenesis. In the course of development, these neurons migrate from the olfactory placode to the hypothalamus. The precise molecular mechanism of this neuronal migration is unclear. Here, we investigated whether the chemokine receptor, Cxcr4b, and its cognate ligand, Cxcl12a, are required for proper migration of GnRH3 neurons in zebrafish. Deviated GnRH3 axonal projections and neuronal migration were detected in larvae that carry a homozygote cxcr4b mutation. Similarly, knockdown of Cxcr4b or Cxcl12a led to the appearance of abnormal GnRH3 axonal projections and cell migration, including absence of the characteristic lateral crossing of GnRH3 axons at the anterior commissure and optic chiasm. Double-labeling analysis has shown that cxcr4b and cxcl12a are expressed along the GnRH3 migration pathway (i.e. olfactory placode, terminal nerve and the optic chiasm). The results of this study suggest that the Cxcl12a-Cxcr4b ligand-receptor pair are involved in the migration of GnRH3 neurons in zebrafish, and are therefore crucial for the development of this system.

Human GnRH deficiency: a unique disease model to unravel the ontogeny of GnRH neurons

Evolutionary survival of a species is largely a function of its reproductive fitness. In mammals, a sparsely populated and widely dispersed network of hypothalamic neurons, the gonadotropin-releasing hormone (GnRH) neurons, serve as the pilot light of reproduction via coordinated secretion of GnRH. Since it first description, human GnRH deficiency has been recognized both clinically and genetically as a heterogeneous disease. A spectrum of different reproductive phenotypes comprised of congenital GnRH deficiency with anosmia (Kallmann syndrome), congenital GnRH deficiency with normal olfaction (normosmic idiopathic hypogonadotropic hypogonadism), and adult-onset hypogonadotropic hypogonadism has been described. In the last two decades, several genes and pathways which govern GnRH ontogeny have been discovered by studying humans with GnRH deficiency. More importantly, detailed study of these patients has highlighted the emerging theme of oligogenicity and genotypic synergism, and also expanded the phenotypic diversity with the documentation of reversal of GnRH deficiency later in adulthood in some patients. The underlying genetic defect has also helped understand the associated nonreproductive phenotypes seen in some of these patients. These insights now provide practicing clinicians with targeted genetic diagnostic strategies and also impact on clinical management.

The PAPS transporter PST-1 is required for heparan sulfation and is essential for viability and neural development in C. elegans

Sulfations of sugars, such as heparan sulfates (HS), or tyrosines require the universal sulfate donor 3'-phospho-adenosine-5'-phosphosulfate (PAPS) to be transported from the cytosol into the Golgi. Metazoan genomes encode two putative PAPS transporters (PAPST1 and PAPST2), which have been shown in vitro to preferentially transport PAPS across membranes. We have identified the C. elegans orthologs of PAPST1 and PAPST2 and named them pst-1 and pst-2, respectively. We show that pst-1 is essential for viability in C. elegans, functions non-redundantly with pst-2, and can act non-autonomously to mediate essential functions. Additionally, pst-1 is required for specific aspects of nervous system development rather than for formation of the major neuronal ganglia or fascicles. Neuronal defects correlate with reduced complexity of HS modification patterns, as measured by direct biochemical analysis. Our results suggest that pst-1 functions in metazoans to establish the complex HS modification patterns that are required for the development of neuronal connectivity.

The genetic and molecular basis of idiopathic hypogonadotropic hypogonadism

Idiopathic hypogonadotropic hypogonadism (IHH) has an incidence of 1-10 cases per 100,000 births. About 60% of patients with IHH present with associated anosmia, also known as Kallmann syndrome, characterized by total or partial loss of olfaction. Many of the gene mutations associated with Kallmann syndrome have been mapped to KAL1 or FGFR1. However, together, these mutations account for only about 15% of Kallmann syndrome cases. More recently, mutations in PROK2 and PROKR2 have been linked to the syndrome and may account for an additional 5-10% of cases. The remaining 40% of patients with IHH have a normal sense of smell. Prior to 2003, the only gene linked to normosmic IHH was the gonadotropin-releasing hormone receptor gene. However, mutations in this receptor are believed to account for only 10% of cases. Subsequently, mutations in KISS1R, TAC3 and TACR3 were identified as causes of normosmic IHH. Certain genes, including PROK2 and FGFR1, are associated with both anosmic and normosmic IHH. Despite recent advances in the field, the genetic causes of the majority of cases of IHH remain unknown. This Review discusses genes associated with hypogonadotropic disorders and the molecular mechanisms by which mutations in these genes may result in IHH.

Extracellular interactome of the FGF receptor-ligand system: complexities and the relative simplicity of the worm

Fibroblast growth factors (FGFs) and their receptors (FGFRs) regulate a multitude of biological functions in embryonic development and in adult. A major question is how does one family of growth factors and their receptors control such a variety of functions? Classically, specificity was thought to be imparted by alternative splicing of the FGFRs, resulting in isoforms that bind specifically to a subset of the FGFs, and by different saccharide sequences in the heparan sulfate proteoglycan (HSPG) co-receptor. A growing number of noncanonical co-receptors such as integrins and neural cell adhesion molecule (NCAM) are now recognized as imparting additional complexity to classic FGFR signaling. This review will discuss the noncanonical FGFR ligands and speculate on the possibility that they provide additional and alternative means to determining the functional specificity of FGFR signaling. We will also discuss how invertebrate models such as C. elegans may advance our understanding of noncanonical FGFR signaling.

Anosmin-1 stimulates outgrowth and branching of developing Purkinje axons

During development, Purkinje axons elongate along precise trajectories and acquire stereotypic branching patterns to innervate targets in the deep nuclei and cerebellar cortex. These processes are accomplished through cell-intrinsic mechanisms, whose operation is regulated by environmental signaling cues. Here, we show that Anosmin-1, the protein defective in the X-linked form of Kallmann syndrome, is one among such cues. Anosmin-1, that stimulates axon elongation and branching in the olfactory system, is expressed by Purkinje cells and deep nuclear neurons of the rat cerebellum during the ontogenetic period when Purkinje axons acquire their mature pattern. These neurons also express the putative Anosmin-1 receptor, fibroblast growth factor receptor 1. Application of Anosmin-1 to dissociated cultures of embryonic (embryonic day 17, E17) or postnatal (postnatal day 0, P0) rat cerebellar cells enhances neuritic elongation and exerts a strong promoting action on the budding of collateral branches and on the extension of terminal arbors. Opposite effects are observed when neutralizing anti-Anosmin-1 antibodies are applied to the same cultures. Comparable results are obtained by administering the protein or the blocking antibodies to organotypic cultures of postnatal (P0) rat cerebellum. In P10 cerebellar slices, Anosmin-1 does not enhance the spontaneous regenerative capabilities of severed Purkinje axons, but promotes the terminal outgrowth of injured neurites into embryonic neocortical explants apposed to the axotomy site. Although Anosmin-1 is unable to change the overall intrinsic growth competence of Purkinje cells, it exerts a powerful stimulatory action on the budding and extension of collateral branches and terminal plexus, contributing to the patterning of Purkinje axons.

Axl and Tyro3 modulate female reproduction by influencing gonadotropin-releasing hormone neuron survival and migration

GnRH neurons must undergo a complex and precise pattern of neuronal migration to appropriately target their projections to the median eminence to trigger gonadotropin secretion and thereby control reproduction. Using NLT GnRH cells as a model of early GnRH neuronal development, we identified the potential importance of Axl and Tyro3, members of the TAM (Tyro3, Axl, and Mer) family of receptor tyrosine kinases in GnRH neuronal cell survival and migration. Silencing studies evaluated the role of Tyro3 and Axl in NLT GnRH neuronal cells and suggest that both play a role in Gas6 stimulation of GnRH neuronal survival and migration. Analysis of mice null for both Axl and Tyro3 showed normal onset of vaginal opening but delayed first estrus and persistently abnormal estrous cyclicity compared with wild-type controls. Analysis of GnRH neuronal numbers and positioning in the adult revealed a total loss of 24% of the neuronal network that was more striking (34%) when considered within specific anatomical compartments, with the largest deficit surrounding the organum vasculosum of the lamina terminalis. Analysis of GnRH neurons during embryogenesis identified a striking loss of immunoreactive cells within the context of the ventral forebrain compartment (36%) and not more rostrally. Studies using caspase 3 cleavage as a marker of apoptosis showed that Axl(-/-), Tyro3(-/-) double-knockout mice had increased cell death in the nose and dorsal forebrain, supporting the underlying mechanism of cell loss. Together these data suggest that Axl and Tyro3 mediate the survival and appropriate targeting of GnRH neurons to the ventral forebrain, thereby contributing to normal reproductive function and cyclicity in the female.

Novel innate immune functions of the whey acidic protein family

Studies on the interaction of HIV with host factors have recently highlighted a potential role in the pathogenesis of AIDS for three distinct members of the whey acidic protein (WAP) family, secretory leukocyte protease inhibitor, Elafin, and ps20. Identified by an evolutionarily conserved canonical four-disulphide structural domain [whey four disulphide core domain (WFDC)], WAP proteins are increasingly being shown to display functions beyond both protease inhibition and anti-infective activity, to which they were originally ascribed. We propose novel mechanisms on why this might be the case based on an analysis of the structure-function of its human members. Our analysis suggests that the interaction of HIV with WAP proteins might unravel unknown functions of the ancient WFDC and inform novel immunotherapies for the treatment of HIV and broader virus infections.

Endocrine manipulation in male infertility

Endocrine therapy for male infertility is broadly categorized as specific or nonspecific therapy. Although uncommon, primary endocrine diagnoses in infertile men are amenable to targeted therapy. The efficacy of empiric endocrine therapy for idiopathic male infertility, however, has not been demonstrated conclusively by clinical trials. With better understanding of the underlying pathophysiology of idiopathic male infertility, careful evaluation of endocrine therapy in well-selected treatment groups and well-designed randomized, controlled trials is warranted. Although empiric endocrine therapy for idiopathic male infertility has been largely replaced by assisted reproductive techniques, both treatment modalities could play a role, perhaps as combination therapy.

Cellular signaling by fibroblast growth factors (FGFs) and their receptors (FGFRs) in male reproduction

The major function of the reproductive system is to ensure the survival of the species by passing on hereditary traits from one generation to the next. This is accomplished through the production of gametes and the generation of hormones that function in the maturation and regulation of the reproductive system. It is well established that normal development and function of the male reproductive system is mediated by endocrine and paracrine signaling pathways. Fibroblast growth factors (FGFs), their receptors (FGFRs), and signaling cascades have been implicated in a diverse range of cellular processes including: proliferation, apoptosis, cell survival, chemotaxis, cell adhesion, motility, and differentiation. The maintenance and regulation of correct FGF signaling is evident from human and mouse genetic studies which demonstrate that mutations leading to disruption of FGF signaling cause a variety of developmental disorders including dominant skeletal diseases, infertility, and cancer. Over the course of this review, we will provide evidence for differential expression of FGFs/FGFRs in the testis, male germ cells, the epididymis, the seminal vesicle, and the prostate. We will show that this signaling cascade has an important role in sperm development and maturation. Furthermore, we will demonstrate that FGF/FGFR signaling is essential for normal epididymal function and prostate development. To this end, we will provide evidence for the involvement of the FGF signaling system in the regulation and maintenance of the male reproductive system.

New frontiers in kisspeptin/GPR54 physiology as fundamental gatekeepers of reproductive function

Identification, in late 2003, of inactivating mutations of the G protein-coupled receptor GPR54 as causative factor for absence of puberty and hypogonadotropic hypogonadism in humans and mice was a major breakthrough in modern Neuroendocrinology, and drew considerable interest on the characterization of the roles of this receptor and its ligands (kisspeptins, encoded by the KiSS-1 gene) in the physiological control of essential facets of reproduction. After 3 years of intense research activity, kisspeptins are universally recognized as essential activators of the gonadotropic axis, with key roles in puberty onset and the control of gonadotropin secretion. While these fundamental functions are now well settled, novel aspects of kisspeptin/GPR54 physiology have emerged, including their involvement in the neuroendocrine control of ovulation and the metabolic gating of reproductive function. In addition, the 'comparative endocrinology' of this system has begun to be explored recently. These facets of kisspeptin/GPR54 function, as fundamental gatekeepers of reproduction, will be comprehensively reviewed herein.

Genetics of puberty

BACKGROUND

Puberty is controlled by genetic and environmental factors. This review examines the genetic basis for puberty by evaluating known gene mutations associated with disordered puberty in humans. At present, at least 17 different single-gene mutations are recognized as being associated with delayed or absent puberty in humans. Several of these genes are involved in the development of the olfactory nervous system, with mutations typically resulting in anosmia/hyposmia and hypogonadotropic hypogonadism, otherwise known as Kallmann syndrome. The biological basis for the association between smell and fertility is strong as development of the gonadotropin-releasing hormone (GnRH) neurons, responsible for regulating fertility, is intricately associated with development of the olfactory system. Other gene mutations, including the recently discovered kisspeptin-GPR54 signalling system, affect puberty by directly or indirectly modulating the functioning of the GnRH neurons and pituitary gonadotrophs. Together, these single-gene mutations are presently estimated to account for approximately 30% of individuals with disorders of puberty.

CONCLUSIONS

A large number of different genes are involved in the complex process of bringing about reproductive competency. In addition to the genetic mutations associated with precocious and delayed puberty, the oligogenic aetiology of these conditions is being increasingly appreciated.

From nose to fertility: the long migratory journey of gonadotropin-releasing hormone neurons

Gonadotropin-releasing hormone (GnRH) neurons, a small number of cells dispersed in the hypothalamic region of the basal forebrain, play an important role in reproductive function. These neurons originate in the nasal placode and migrate, first in the nasal compartment, then through the cribriform plate and finally through the basal forebrain, before they attain their positions in the hypothalamus. Their movement through changing molecular environments suggests that numerous factors are involved in different phases of their migration. In humans, failure of GnRH neurons to migrate normally results in delayed or absent pubertal maturation and infertility. Advances in genetic and molecular biologic techniques in this decade have allowed us to gain insights into several molecules that affect the migration of GnRH neurons and, consequently, play a role in the establishment and maintenance of reproductive function.