PROKR2 missense mutations associated with Kallmann syndrome impair receptor signalling activity

Intracerebroventricular PROK2 infusion could increase the secretion of male reproductive hormones by stimulating the HPG axis

BACKGROUND

Prokineticin 2 (PROK2), an important neuropeptide that plays a key role in the neuronal migration of gonadotropin-releasing hormone (GnRH) in the hypothalamus, is known to have regulatory effects on the gonads. In the present study, the impact of intracerebroventricular (icv) PROK2 infusion on hypothalamic-pituitary-gonadal axis (HPG) hormones, testicular tissues, and sperm concentration was investigated.

METHODS AND RESULTS

Rats were randomly divided into four groups: control, sham, PROK2 1.5 and PROK2 4.5. Rats in the PROK2 1.5 and PROK2 4.5 groups were administered 1.5 nmol and 4.5 nmol PROK2 intracerebroventricularly for 7 days via an osmotic mini pump (1 µl/h), respectively. Rat blood serum follicle stimulating hormone (FSH), luteinizing hormone (LH) and testosterone hormone levels were determined with the ELISA method in the blood samples after 7 days of infusion. GnRH mRNA expression was determined with the RT-PCR in hypothalamus tissues. analyze Sperm concentration was determined, and testicular tissue was examined histologically with the hematoxylin-eosin staining method. It was observed that GnRH mRNA expression increased in both PROK2 infusion groups. Serum FSH, LH and testosterone hormone levels also increased in these groups. Although sperm concentration increased in PROK2 infusion groups when compared to the control and sham, the differences were not statistically significant. Testicular tissue seminiferous epithelial thickness was higher in the PROK2 groups when compared to the control and sham groups.

CONCLUSION

The present study findings demonstrated that icv PROK2 infusion induced the HPG axis. It could be suggested that PROK2 could be a potential agent in the treatment of male infertility induced by endocrinological defects.

G protein-coupled receptor (GPCR) gene variants and human genetic disease

Genetic variations in the genes encoding G protein-coupled receptors (GPCRs) can disrupt receptor structure and function, which can result in human genetic diseases. Disease-causing mutations have been reported in at least 55 GPCRs for more than 66 monogenic diseases in humans. The spectrum of pathogenic and likely pathogenic variants includes loss of function variants that decrease receptor signaling on one extreme and gain of function that may result in biased signaling or constitutive activity, originally modeled on prototypical rhodopsin GPCR variants identified in retinitis pigmentosa, on the other. GPCR variants disrupt ligand binding, G protein coupling, accessory protein function, receptor desensitization and receptor recycling. Next generation sequencing has made it possible to identify variants of uncertain significance (VUS). We discuss variants in receptors known to result in disease and in silico strategies for disambiguation of VUS such as sorting intolerant from tolerant and polymorphism phenotyping. Modeling of variants has contributed to drug development and precision medicine, including drugs that target the melanocortin receptor in obesity and interventions that reverse loss of gonadotropin-releasing hormone receptor from the cell surface in idiopathic hypogonadotropic hypogonadism. Activating and inactivating variants of the calcium sensing receptor (CaSR) gene that are pathogenic in familial hypocalciuric hypercalcemia and autosomal dominant hypocalcemia have enabled the development of calcimimetics and calcilytics. Next generation sequencing has continued to identify variants in GPCR genes, including orphan receptors, that contribute to human phenotypes and may have therapeutic potential. Variants of the CaSR gene, some encoding an arginine-rich region that promotes receptor phosphorylation and intracellular retention, have been linked to an idiopathic epilepsy syndrome. Agnostic strategies have identified variants of the pyroglutamylated RF amide peptide receptor gene in intellectual disability and G protein-coupled receptor 39 identified in psoriatic arthropathy. Coding variants of the G protein-coupled receptor L1 (GPR37L1) orphan receptor gene have been identified in a rare familial progressive myoclonus epilepsy. The study of the role of GPCR variants in monogenic, Mendelian phenotypes has provided the basis of modeling the significance of more common variants of pharmacogenetic significance.

Additional mutation in PROKR2 and phenotypic differences in a Kallmann syndrome/normosmic congenital hypogonadotropic hypogonadism family carrying FGFR1 missense mutation

Congenital hypogonadotropic hypogonadism (CHH) is a genetically and clinically diverse disorder encompassing Kallmann syndrome (KS) and normosmic CHH (nCHH). Although mutations in numerous genes account for nearly 50% of CHH cases, a significant portion remains genetically uncharacterized. While most mutations follow the traditional Mendelian inheritance patterns, evidence suggests oligogenic interactions between CHH genes, acting as modifier genes to explain variable expressivity and incomplete penetrance associated with certain mutations.In this study, the proband presented with nCHH, while his son exhibited KS. We employed whole-exome sequencing (WES) to investigate the genetic differences between the two, and Sanger sequencing was used to validate the results obtained from WES.Genetic analysis revealed that both the proband and his son harboured a mutation in FGFR1 gene. Notably, an additional rare mutation in PROKR2 gene was exclusively identified in the son, which suggests the cause of the phenotypic difference between KS and nCHH.

PROKR2 Mutations in Patients with Short Stature Who Have Isolated Growth Hormone Deficiency and Multiple Pituitary Hormone Deficiency

Objective

Recent reports have indicated the role of the prokineticin receptor 2 gene (PROKR2) in the etiology of pituitary hormone deficiencies, suggesting a potential role for the PROK2 pathway in pituitary development, in addition to its role in gonadotropin releasing hormone-expressing neuron development. Here, we present the clinical and molecular findings of four patients with PROKR2 mutations.

Methods

Next-generation targeted sequencing was used to screen 25 genes in 59 unrelated patients with multiple pituitary hormone deficiency (MPHD), isolated growth hormone (GH) deficiency, or idiopathic short stature.

Results

Two different, very rare PROKR2 missense alterations classified as pathogenic (NM_144773.4:c.518T>G; NP_658986.1:p. (Leu173Arg)) and likely pathogenic (NM_144773.4:c.254G>A; NP_658986.1:p.(Arg85His)) were identified in four patients in heterozygous form. Patient 1 and Patient 2 presented with short stature and were diagnosed as GH deficiency. Patient 3 and Patient 4 presented with central hypothyroidism and cryptorchidism and were diagnosed as MPHD. No other pathogenic alterations were detected in the remaining 24 genes related to short stature, MPHD, and hypogonadotropic hypogonadism. Segregation analysis revealed asymptomatic or mildly affected carriers in the families.

Conclusion

PROKR2 dominance should be kept in mind as a very rare cause of GH deficiency and MPHD. Expressional variation or lack of penetrance may imply oligogenic inheritance or other environmental modifiers in individuals who are heterozygous carriers.

Clinical Manifestations, Genetic Variants and Therapeutic Evaluation in Sporadic Chinese Patients with Idiopathic Hypogonadotropic Hypogonadism

Purpose

Genetic factors account for a large proportion of idiopathic hypogonadotropic hypogonadism (IHH) etiologies, although not necessarily a complete genetic basis. This study aimed to characterize the clinical presentations, genetic variants, and therapeutic outcomes of patients with sporadic IHH, which may be helpful for genetic counseling and treatment decisions.

Patients and Methods

Eleven Chinese patients with IHH were retrospectively analyzed. Rare genetic variants were evaluated using whole-exome sequencing and bioinformatics analysis and were further classified according to the ACMG-AMP guidelines. The therapeutic responses of patients were further evaluated.

Results

Six heterozygous variants of SOX10, WDR11, PROKR2, CHD7 and FGF17 were detected in five Kallmann syndrome (KS) patients, whereas two heterozygous variants of CHD7 and PROKR2 were detected in two normosmic IHH (nIHH) patients. Among these variants, a novel likely pathogenic variant in the SOX10 (c.429-1G>C) was considered to cause the KS phenotype in patient 02, and two potential variants of uncertain significance (VUS) in CHD7 (c.3344G>A and c.7391A>G) possibly contributed to the KS phenotype in patient 05 and the nIHH phenotype in patient 07, which need to be confirmed by further evidence. Additionally, long-term testosterone or estradiol replacement treatment effectively improved the development of sexual characteristics in patients with IHH.

Conclusion

Next-generation sequencing is a powerful tool for identifying the molecular etiology and early diagnosis of IHH. Efficient therapeutic outcomes strongly indicate a need for timely treatment.

A functional spectrum of PROKR2 mutations identified in isolated hypogonadotropic hypogonadism

Isolated hypogonadotropic hypogonadism (IHH) is a rare disease with hypogonadism and infertility caused by the defects in embryonic migration of hypothalamic gonadotropin-releasing hormone (GnRH) neurons, hypothalamic GnRH secretion or GnRH signal transduction. PROKR2 gene, encoding a G-protein coupled receptor PROKR2, is one of the most frequently mutated genes identified in IHH patients. However, the functional consequences of several PROKR2 mutants remain elusive. In this study, we systematically analyzed the Gαq, Gαs and ERK1/2 signaling of 23 IHH-associated PROKR2 mutations which are yet to be functionally characterized. We demonstrate that blockage of Gαq, instead of MAPK/ERK pathway, inhibited PROK2-induced migration of PROKR2-expressing cells, implying that PROKR2-related IHH results primarily due to Gαq signaling pathway disruption. Combined with previous reports, we categorized a total of 63 IHH-associated PROKR2 mutations into four distinct groups according Gαq pathway functionality: (i) neutral (N, >80% activity); (ii) low pathogenicity (L, 50-80% activity); (iii) medium pathogenicity (M, 20-50% activity) and (iv) high pathogenicity (H, <20% activity). We further compared the cell-based functional results with in silico mutational prediction programs. Our results indicated that while Sorting Intolerant from Tolerant predictions were accurate for transmembrane region mutations, mutations localized in the intracellular and extracellular domains were accurately predicted by the Combined Annotation Dependent Depletion prediction tool. Our results thus provide a functional database that can be used to guide diagnosis and appropriate genetic counseling in IHH patients with PROKR2 mutations.

Genetic Analysis of Patients with Congenital Hypogonadotropic Hypogonadism: A Case Series

Congenital hypogonadotropic hypogonadism (cHH)/Kallmann syndrome (KS) is a rare genetic disorder with variable penetrance and a complex inheritance pattern. Consequently, it does not always follow Mendelian laws. More recently, digenic and oligogenic transmission has been recognized in 1.5-15% of cases. We report the results of a clinical and genetic investigation of five unrelated patients with cHH/KS analyzed using a customized gene panel. Patients were diagnosed according to the clinical, hormonal, and radiological criteria of the European Consensus Statement. DNA was analyzed using next-generation sequencing with a customized panel that included 31 genes. When available, first-degree relatives of the probands were also analyzed to assess genotype-phenotype segregation. The consequences of the identified variants on gene function were evaluated by analyzing the conservation of amino acids across species and by using molecular modeling. We found one new pathogenic variant of the CHD7 gene (c.576T>A, p.Tyr1928) and three new variants of unknown significance (VUSs) in IL17RD (c.960G>A, p.Met320Ile), FGF17 (c.208G>A, p.Gly70Arg), and DUSP6 (c.434T>G, p.Leu145Arg). All were present in the heterozygous state. Previously reported heterozygous variants were also found in the PROK2 (c.163del, p.Ile55*), CHD7 (c.c.2750C>T, p.Thr917Met and c.7891C>T, p.Arg2631*), FLRT3 (c.1106C>T, p.Ala369Val), and CCDC103 (c.461A>C, p.His154Pro) genes. Molecular modeling, molecular dynamics, and conservation analyses were performed on three out of the nine variants identified in our patients, namely, FGF17 (p.Gly70Arg), DUSP6 (p.Leu145Arg), and CHD7 p.(Thr917Met). Except for DUSP6, where the L145R variant was shown to disrupt the interaction between β6 and β3, needed for extracellular signal-regulated kinase 2 (ERK2) binding and recognition, no significant changes were identified between the wild-types and mutants of the other proteins. We found a new pathogenic variant of the CHD7 gene. The molecular modeling results suggest that the VUS of the DUSP6 (c.434T>G, p.Leu145Arg) gene may play a role in the pathogenesis of cHH. However, our analysis indicates that it is unlikely that the VUSs for the IL17RD (c.960G>A, p.Met320Ile) and FGF17 (c.208G>A, p.Gly70Arg) genes are involved in the pathogenesis of cHH. Functional studies are needed to confirm this hypothesis.

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.

Non-Peptide Agonists and Antagonists of the Prokineticin Receptors

The prokineticin family comprises a group of secreted peptides that can be classified as chemokines based on their structural features and chemotactic and immunomodulatory functions. Prokineticins (PKs) bind with high affinity to two G protein-coupled receptors (GPCRs). Prokineticin receptor 1 (PKR1) and prokineticin receptor 2 (PKR2) are involved in a variety of physiological functions such as angiogenesis and neurogenesis, hematopoiesis, the control of hypothalamic hormone secretion, the regulation of circadian rhythm and the modulation of complex behaviors such as feeding and drinking. Dysregulation of the system leads to an inflammatory process that is the substrate for many pathological conditions such as cancer, pain, neuroinflammation and neurodegenerative diseases such as Alzheimer's and Parkinson's disease. The use of PKR's antagonists reduces PK2/PKRs upregulation triggered by various inflammatory processes, suggesting that a pharmacological blockade of PKRs may be a successful strategy to treat inflammatory/neuroinflammatory diseases, at least in rodents. Under certain circumstances, the PK system exhibits protective/neuroprotective effects, so PKR agonists have also been developed to modulate the prokineticin system.

Quantification of changes in human islet G protein-coupled receptor mRNA expression in obesity

BACKGROUND

G protein-coupled receptors (GPCRs) play crucial roles in regulating islet function, with Gαs- and Gαq-coupled receptors being linked to the stimulation of insulin secretion. We have quantified the mRNA expression of 384 non-olfactory GPCRs in islets isolated from lean and obese organ donors to determine alterations in islet GPCR mRNA expression in obesity.

METHODS

RT-qPCR was used to quantify GPCR mRNAs relative to five reference genes (ACTB, GAPDH, PPIA, TBP, and TFRC) in human islets isolated from lean (BMI = 22.6 ± 0.5) and obese (BMI = 32.0 ± 0.8) donors.

RESULTS

Overall, 197 and 256 GPCR mRNAs were detected above trace level in islets from lean and obese donors, respectively, with 191 GPCR mRNAs being common to the lean and obese groups. 40.9% (n = 157) and 27.1% (n = 104) of the mRNAs were expressed at trace level whilst 7.8% and 6.3% were absent in islets from lean and obese donors, respectively. Hundred and seventeen GPCR mRNAs were upregulated at least twofold in islets from obese donors, and there was >twofold downregulation of 21 GPCR mRNAs. Of particular interest, several receptors signalling via Gαs or Gαq showed significant mRNA upregulation in islets from obese donors (fold increase: PTH2R: 54.0 ± 14.6; MC2R: 34.3 ± 11.5; RXFP1: 8.5 ± 2.1; HTR2B: 6.0 ± 2.0; GPR110: 3.9 ± 1.2; PROKR2: 3.9 ± 0.7).

CONCLUSIONS

Under conditions of obesity, human islets showed significant alterations in mRNAs encoding numerous GPCRs. The increased expression of Gαs- and Gαq-coupled receptors that have not previously been investigated in β-cells opens up possibilities of novel therapeutic candidates that may lead to the potentiation of insulin secretion and/or β-cell mass to regulate glucose homeostasis.

The Clinical and Genetic Characteristics in Children with Idiopathic Hypogonadotropin Hypogonadism

Background. Idiopathic hypogonadotropin hypogonadism (IHH) is caused by hypothalamic-pituitary-gonadal axis dysfunction. This is divided into Kallmann syndrome which has an impaired sense of smell and hypogonadotropin hypogonadism with normal olfactory (nIHH sense. Approximately 60% of patients are associated with Kallmann syndrome, whereas there are approximately 40% with hypogonadotropin hypogonadism (nIHH). This disease is associated with various variants in genes along with different phenotypic characteristics, and even those gene variations could also lead to the cancer formation in patients. So, current study has been designed to investigate and to better understand the characteristics of various IHH-associated genes and the correlation between IHH genes and phenotype. Methods. The cohort included 14 children with IHH (6 patients of KS and 8 patients of IHH), including 13 boys and 1 girl. Exclusion criteria are as follows: diagnosis of secondary hypogonadotropin hypogonadism due to tumor, trauma, drugs, or other systemic diseases. Clinical data and genetic results were analyzed. Results. Almost all male patients showed micropenis (12/13, 92.3%), and few of them had cryptorchidism (5/13, 41.7%). A total of 6 genes, CHD7, PROKR2, ANOS1, FGFR1, SEMA3A, and NDNF, were detected. CHD7 was the most common (11/17, 64.7%), and the main mutation type was missense mutation (14/16, 87.5%). Six reported variants and 10 new variants (5 genes, including entire ANSO1 duplicates) were found. Neonatal variation was detected in 3 patients with IHH. Eight patients inherited the variation from their father, while five patients inherited it from their mother. One patient had both FGFR1 and SEMA3A gene variants, while the other had two different CHD7 gene variants and entire ANSO1 repeats. According to ACMG criteria, 4 variants were pathogenic (P), 2 were possibly pathogenic (LP), and 8 had uncertain significance (US). In patients with P or LP (5/6, 83.3%), we found that extragonadal symptoms were more common. Conclusions. It was concluded that variations in the studied genes could lead to the IHH. Ten new variants have been reported which may lead to different symptoms of IHH. For CHD7 variants, the rare sequencing variants (RSVs) of P or LP showed commonly associated with CHARGE syndrome. Findings of the current study may help for the better diagnosis and treatment of IHH.

Biallelic PROKR2 variants and congenital hypogonadotropic hypogonadism: a case report and a literature review

Congenital hypogonadotropic hypogonadism (CHH) is a rare disorder that causes gonadotropin-releasing hormone (GnRH) deficiency and sexual immaturity. CHH may accompany an abnormal sense of smell (Kallmann syndrome, KS) or no such manifestation (normosmic-CHH). This unusual combination of manifestations is explained by the fact that GnRH neurons originate in the olfactory placode and migrate to the forebrain during embryogenesis. We describe the case of a 31-year-old man with normosmic-CHH, who also had obesity, type 2 diabetes and intellectual disability. He was noticed to have sexual immaturity (small testes with no pubic hair) at age 20 years, when diabetic ketoacidosis developed. Basal and GnRH-stimulated levels of LH (1.0→12.0 IU/L) and FSH (1.9→6.1 IU/L) were detectable but low. The results of the T&T olfactometer and the Alinamin test were definitely normal, with an anatomically normal olfactory system on MRI. Sequencing of 22 CHH-related genes was performed, and compound heterozygous PROKR2 variants were identified: one was a previously known loss-of-function variant (p.Trp178Ser) and the other was a nonsense variant (p.Trp212*). Through a literature review, we found 22 patients (including our patient) with CHH due to biallelic PROKR2 variants, which led us to recognize that most of the patients (86%) were diagnosed with KS. Clinical observations in this study indicate that, even though they have CHH, biallelic PROKR2 variant carriers may have a normal olfactory system as well as presumably normal migration of GnRH neurons. This suggests that the PROK2-PROKR2 pathway affects the function of GnRH neurons after their migration.

Anosmin 1 N-terminal domains modulate prokineticin receptor 2 activation by prokineticin 2

The X-linked form of Kallmann syndrome (KS), characterized by hypogonadotropic hypogonadism and anosmia, is due to mutations in the ANOS1 gene that encodes for the extracellular matrix (ECM) protein anosmin 1. Prokineticins (PKs) exert their biological functions through the activation of the G protein-coupled receptors (GPCRs) prokineticin receptor 1 and 2 (PKR1, 2), and mutations in the PK2 and PKR2 genes are involved in the pathogenesis of KS. We have previously shown interaction between PKR2 and anosmin 1 in vitro. In the current report we present evidence of the modulation of PK2/PKR2 activity by anosmin 1, since this protein is able to enhance the activation of the ERK1/2 (extracellular signal-regulated kinase 1/2) pathway elicited by PK2 through PKR2. We also show that the N-terminal region of anosmin 1, capable of binding to the PK2-binding domain of PKR2, seems to be responsible for this effect. The whey acidic protein domain (WAP) is necessary for this modulatory activity, although data from GST pull-down (glutathione-S-transferase) and analysis of the N267K mutation in the fibronectin type III domain 1 (FnIII.1) suggest the cysteine-rich (CR) and the FnIII.1 domains could assist the WAP domain both in the binding to PKR2 and in the modulation of the activation of the receptor by PK2. Our data support the idea of a modulatory role of anosmin 1 in the biological effects controlled by the PK2/PKR2 system.

Next-generation sequencing-based mutational analysis of idiopathic short stature and isolated growth hormone deficiency in Korean pediatric patients

We investigated the distribution of short stature-associated mutations in Korean pediatric patients with idiopathic short stature (ISS) and isolated growth hormone deficiency (IGHD) via targeted next-generation sequencing (TNGS). We employed a 96-gene TNGS panel for short stature in a total of 144 patients (5-19 years-old) previously diagnosed with ISS or IGHD and identified heterozygous pathogenic or likely pathogenic genetic variants in 14 (10%) patients. Of the mutated genes, PROKR2 (n = 3) is associated with gonadotropin-releasing hormone deficiency or hypopituitarism, while FGFR1 (n = 1) and NPR2 (n = 3) encode growth plate paracrine factors. FBN1 (n = 1), COL9A1 (n = 1), MATN3 (n = 1), and ACAN (n = 3) regulate the cartilage extracellular matrix, while PTPN11 (n = 1) controls intracellular pathways. Six patients had IGHD, and eight patients had ISS. The current findings highlight the utility of TNGS for determining the genetic etiology in these patients.

Trafficking-defective mutant PROKR2 cycles between endoplasmic reticulum and Golgi to attenuate endoplasmic reticulum stress

The endoplasmic reticulum (ER) possesses a quality control system that prevents misfolded proteins from leaving the ER for routing to the ER-associated degradation pathway. Some misfolded proteins can escape the ER to reach the Golgi, where they are then retrieved from the Golgi back to the ER for degradation, but why this occurs needs to be clarified. Studying a mutant prokineticin receptor 2 identified in patients with hypogonadotropic hypogonadism as a model, we find that the post-ER retrieval system provides another layer of quality control and also lowers the load of misfolded proteins in the ER to reduce ER stress. Our findings reveal the importance of a post-ER quality control mechanism in contributing to cellular homeostasis.

G protein–coupled receptors (GPCRs) play crucial roles in numerous physiological and pathological processes. Mutations in GPCRs that result in loss of function or alterations in signaling can lead to inherited or acquired diseases. Herein, studying prokineticin receptor 2 (PROKR2), we initially identify distinct interactomes for wild-type (WT) versus a mutant (P290S) PROKR2 that causes hypogonadotropic hypogonadism. We then find that both the WT and mutant PROKR2 are targeted for endoplasmic reticulum (ER)-associated degradation, but the mutant is degraded to a greater extent. Further analysis revealed that both forms can also leave the ER to reach the Golgi. However, whereas most of the WT is further transported to the cell surface, most of the mutant is retrieved to the ER. Thus, the post-ER itinerary plays an important role in distinguishing the ultimate fate of the WT versus the mutant. We have further discovered that this post-ER itinerary reduces ER stress induced by the mutant PROKR2. Moreover, we extend the core findings to another model GPCR. Our findings advance the understanding of disease pathogenesis induced by a mutation at a key residue that is conserved across many GPCRs and thus contributes to a fundamental understanding of the diverse mechanisms used by cellular quality control to accommodate misfolded proteins.

Clinical, hormonal, and genetic characteristics of 25 Chinese patients with idiopathic hypogonadotropic hypogonadism

BACKGROUND

Idiopathic hypogonadotropic hypogonadism (IHH) is a type of congenital disease caused by a variety of gene variants leading to dysfunction in the secretion of hypothalamic gonadotropin-releasing hormones (GnRHs). Clinically, IHH can be divided into Kallmann syndrome (KS) with dysosmia and normosmic idiopathic hypogonadotropic hypogonadism (nIHH) according to the presence or absence of an olfactory disorder.

METHODS

We retrospectively evaluated 25 IHH patients (8 KS and 17 nIHH) who were diagnosed at the Department of Endocrinology of Shanghai Children's Hospital from 2015 to 2021. We analysed the patients' clinical data, including their hormone levels and gene sequences.

RESULTS

All male patients exhibited small phalli, and 35% of them exhibited cryptorchidism. A significant difference was observed in the levels of dihydrotestosterone (DHT) after human chorionic gonadotropin (HCG) stimulation (P = 0.028) between the KS group and the nIHH group. Missense variants were the major cause of IHH, and the main pathogenic genes were FGFR1, PROKR2/PROK2, and KAl1. Nine reported and 13 novel variants of six genes were identified. De novo variants were detected in 16 IHH patients; eight patients inherited the variants from their mothers, while only three patients inherited variants from their fathers. One patient had both KAl1 and PROKR2 gene variants, and another patient had two different PROKR2 gene variants. These two patients both had the hot spot variant c.533G > C (p. Trp178Ser) of the PROKR2 gene.

CONCLUSION

IHH should be highly suspected in patients with a small phallus and cryptorchidism. Compared with nIHH patients, KS patients exhibited a higher level of DHT after HCG stimulation. Missense variants were the major cause of IHH, and most of the inherited variants were from their mothers who exhibited no obvious clinical symptoms. We identified 9 reported variants and 13 novel variants that led to IHH. A small proportion of patients were at risk of inheriting either the oligogenic variant or the compound heterozygous variant. The hot spot variant c.533G > C (p. Trp178Ser) of PROKR2 might be involved in oligogenic inheritance and compound heterozygous inheritance. These findings provide deeper insight into the diagnosis and classification of IHH and will contribute to its clinical assessment.

Prokineticin-Receptor Network: Mechanisms of Regulation

Prokineticins are a new class of chemokine-like peptides that bind their G protein-coupled receptors, PKR1 and PKR2, and promote chemotaxis and the production of pro-inflammatory cytokines following tissue injury or infection. This review summarizes the major cellular and biochemical mechanisms of prokineticins pathway regulation that, like other chemokines, include: genetic polymorphisms; mRNA splice modulation; expression regulation at transcriptional and post-transcriptional levels; prokineticins interactions with cell-surface glycosaminoglycans; PKRs degradation, localization, post-translational modifications and oligomerization; alternative signaling responses; binding to pharmacological inhibitors. Understanding these mechanisms, which together exert substantial biochemical control and greatly enhance the complexity of the prokineticin-receptor network, leads to novel opportunities for therapeutic intervention. In this way, besides targeting prokineticins or their receptors directly, it could be possible to indirectly influence their activity by modulating their expression and localization or blocking the downstream signaling pathways.

Current concepts surrounding neonatal hormone therapy for boys with congenital hypogonadotropic hypogonadism

INTRODUCTION

Congenital hypogonadotropic hypogonadism (CHH) is a genetic disorder of reproduction and development, characterized by deficient gonadotropin-releasing hormone (GnRH) secretion or action, affecting 1-in-4,000-15,000 males. Micropenis and undescended testes are cardinal features of antenatal GnRH deficiency and could indicate absent minipuberty in the first postnatal months. In this review, we outline the pathophysiology and clinical consequences of absent minipuberty and its implications for optimal approaches to the endocrine management of affected boys.

AREAS COVERED

Deficient GnRH activity during fetal development and neonatal-infancy phase of minipuberty accounts for the diminished mass of Sertoli cells and seminiferous tubules among CHH males, enduring impairment of reproductive function even during gonadotropin replacement in adult life. In overcoming this obstacle, several clinical studies of neonatal gonadotropin replacement have consistently shown positive results in inducing testicular development and correcting cryptorchidism.

EXPERT OPINION

A high index of clinical suspicion, combined with hormonal testing undertaken in the postnatal period of 1-4 months, can reliably confirm or refute the diagnosis of CHH. Timely identification of CHH in affected male infants (having characteristic "red flag' developmental anomalies) opens up the possibility for gonadotropin replacement as a targeted therapy to restore the normal hormonal milieu of minipuberty. Further work is necessary in formulating optimal gonadotropin treatment regimens to be more widely adopted in clinical practice.

Targeting trafficking as a therapeutic avenue for misfolded GPCRs leading to endocrine diseases

G protein-coupled receptors (GPCRs) are plasma membrane proteins associated with an array of functions. Mutations in these receptors lead to a number of genetic diseases, including diseases involving the endocrine system. A particular subset of loss-of-function mutant GPCRs are misfolded receptors unable to traffic to their site of function (i.e. the cell surface plasma membrane). Endocrine disorders in humans caused by GPCR misfolding include, among others, hypo- and hyper-gonadotropic hypogonadism, morbid obesity, familial hypocalciuric hypercalcemia and neonatal severe hyperparathyroidism, X-linked nephrogenic diabetes insipidus, congenital hypothyroidism, and familial glucocorticoid resistance. Several in vitro and in vivo experimental approaches have been employed to restore function of some misfolded GPCRs linked to endocrine disfunction. The most promising approach is by employing pharmacological chaperones or pharmacoperones, which assist abnormally and incompletely folded proteins to refold correctly and adopt a more stable configuration to pass the scrutiny of the cell's quality control system, thereby correcting misrouting. This review covers the most important aspects that regulate folding and traffic of newly synthesized proteins, as well as the experimental approaches targeted to overcome protein misfolding, with special focus on GPCRs involved in endocrine diseases.

L1 Syndrome Prenatal Diagnosis Supplemented by Functional Analysis of One L1CAM Gene Missense Variant

L1 syndrome, a complex X-linked neurological disorder, is caused by mutations in the L1 cell adhesion molecule (L1CAM) gene. L1CAM molecule is a member of immunoglobulin (Ig) superfamily of neural cell adhesion molecules (CAMs), which plays a pivotal role in the developing nervous system. In this study, a L1CAM gene exonic missense variant (c.1108G > A, p.G370R) was identified in two induced fetuses (abnormal fetuses), who presented corpus callosum agenesis accompanied with hydrocephalus. Clinical data, published literature, online database, and bioinformatic analysis suggest that the single-nucleotide variant of L1CAM gene is a likely pathogenic mutation. In vitro assays were performed to evaluate the effects of this variant. Based on NSC-34/COS-7 cells transfected with wild-type (L1-WT) and mutated (L1-G370R) plasmids, the L1CAM gene exonic missense variant (c.1108G > A, p.G370R) reduced cell surface expression, induced partial endoplasmic reticulum retention, affected posttranslational modification, and reduced protein’s homophilic adhesive ability, but did not induce endoplasmic reticulum stress, which might probably associate with L1 syndrome. Finally, 35 isolated fetuses were screened for L1CAM gene variants by Sanger sequencing. These cases all prenatally suspected of corpus callosum agenesis accompanied with hydrocephalus, which may relate to L1 syndrome. Consequently, one L1CAM gene single missense variant (c.550C > T, p.R184W) was detected in one fetus. Our results provided evidence that the L1CAM gene missense variant (c.1108G > A, p.G370R) may relate to L1 syndrome. The findings of this study suggest a potential possibility of L1CAM gene screening for prenatal diagnoses for fetuses presented corpus callosum agenesis accompanied with hydrocephalus.

Misfolded G Protein-Coupled Receptors and Endocrine Disease. Molecular Mechanisms and Therapeutic Prospects

Misfolding of G protein-coupled receptors (GPCRs) caused by mutations frequently leads to disease due to intracellular trapping of the conformationally abnormal receptor. Several endocrine diseases due to inactivating mutations in GPCRs have been described, including X-linked nephrogenic diabetes insipidus, thyroid disorders, familial hypocalciuric hypercalcemia, obesity, familial glucocorticoid deficiency [melanocortin-2 receptor, MC2R (also known as adrenocorticotropin receptor, ACTHR), and reproductive disorders. In these mutant receptors, misfolding leads to endoplasmic reticulum retention, increased intracellular degradation, and deficient trafficking of the abnormal receptor to the cell surface plasma membrane, causing inability of the receptor to interact with agonists and trigger intracellular signaling. In this review, we discuss the mechanisms whereby mutations in GPCRs involved in endocrine function in humans lead to misfolding, decreased plasma membrane expression of the receptor protein, and loss-of-function diseases, and also describe several experimental approaches employed to rescue trafficking and function of the misfolded receptors. Special attention is given to misfolded GPCRs that regulate reproductive function, given the key role played by these particular membrane receptors in sexual development and fertility, and recent reports on promising therapeutic interventions targeting trafficking of these defective proteins to rescue completely or partially their normal function.

Oligogenic Inheritance Underlying Incomplete Penetrance of PROKR2 Mutations in Hypogonadotropic Hypogonadism

The role of the prokineticin 2 pathway in human reproduction, olfactory bulb morphogenesis, and gonadotropin-releasing hormone secretion is well established. Recent studies have highlighted the implication of di/oligogenic inheritance in this disorder. In the present study, we aimed to identify the genetic mechanisms that could explain incomplete penetrance in hypogonadotropic hypogonadism (HH). This study involved two unrelated Tunisian patients with HH, which was triggered by identifying a homozygous p.(Pro290Ser) mutation in the PROKR2 gene in a girl (HH1) with Kallmann syndrome (KS). The functional effect of this variant has previously been well demonstrated. Unexpectedly, her unaffected father (HH1P) and brother (HH1F) also carried this genetic variation at a homozygous state. In the second family, we identified a heterozygous p.(Lys205del) mutation in PROKR2, both in a male patient with normosmic idiopathic IHH (HH12) and his asymptomatic mother. Whole-exome sequencing in the three HH1 family members allowed the identification of additional variants in the prioritized genes. We then carried out digenic combination predictions using the oligogenic resource for variant analysis (ORVAL) software. For HH1, we found the highest number of disease-causing variant pairs. Notably, a CCDC141 variant (c.2803C > T) was involved in 18 pathogenic digenic combinations. The CCDC141 variant acts in an autosomal recessive inheritance mode, based on the digenic effect prediction data. For the second patient (HH12), prediction by ORVAL allowed the identification of an interesting pathogenic digenic combination between DUSP6 and SEMA7A genes, predicted as “dual molecular diagnosis.” The SEMA7A variant p.(Glu436Lys) is novel and predicted as a VUS by Varsome. Sanger validation revealed the absence of this variant in the healthy mother. We hypothesize that disease expression in HH12 could be induced by the digenic transmission of the SEMA7A and DUSP6 variants or a monogenic inheritance involving only the SEMA7A VUS if further functional assays allow its reclassification into pathogenic. Our findings confirm that homozygous loss-of-function genetic variations are insufficient to cause KS, and that oligogenism is most likely the main transmission mode involved in Congenital Hypogonadotropic Hypogonadism.

Genetic Profiles and Three-year Follow-up Study of Chinese Males With Congenital Hypogonadotropic Hypogonadism

BACKGROUND

The correlation between long-term treatment outcomes with genotypes in congenital hypogonadotropic hypogonadism (CHH) males is rarely reported.

AIM

To investigate the correlations among genotypes, phenotypes, and treatment outcomes for CHH male patients.

METHODS

Whole exome sequencing was performed for 73 Chinese CHH males from one academic center. Patients self-selected one of the 4 treatments: pulsatile Gonadorelin pump (PGP), cyclical gonadotropins therapy (CGT), human menopausal gonadotropin monotherapy, or testosterone replacement treatment. Clinical assessments were performed every 3 months for 3 years.

OUTCOMES

The pathogenicity of variants was determined. Baseline clinical features, spermatogenesis outcomes were analysed.

RESULTS

62 variants were identified in 51 patients (69.9%), 17 of which were novel. Among these mutations, variants on FGFR1, PROKR2, CHD7, ANOS1 and NSMF gene were 16.1%, 16.1%, 11.3%, 8.1% and 8.1% respectively. 11 patients followed the oligogenic pattern (21.6%). All CHD7 patients had hearing impairment, or structural deformities of external/ inner ear and were diagnosed as CHARGE syndrome. 24.7% of CHH patients manifested with ear/hearing anomalies. KS patients had higher rates of cryptorchidism history and ear/hearing anomalies than normosmic CHH subjects. Male patients with PROKR2 mutations showed relatively better testicular development, less dental deformity when compared with FGFR1 mutations. About 30% normosmic patients defined by simple olfactory assessment showed olfactory nerve center (ONC) dysplasia under nasal sinus MRI examination. Among the CHH males treated with CGT or PGP, 70.2% reached spermatogenesis within 3 years of treatment.

CLINICAL IMPLICATIONS

No direct correlation was observed between certain responsible genes and spermatogenic outcomes. When CHH patients were identified with CHD7 variants, ear/hearing evaluation should be carefully performed. The precise assessment of ONC development was advised for normosmic CHH subjects.

STRENGTHS & LIMITATIONS

This study provided informative long-term treatment data of CHH male patients screened with whole exome sequencing. The limitations included small number of subgroups with multifaceted gene variants, clinical heterogeneity, uncontrolled sperm-inducing treatment method. The seventeen novel mutations worth experimental validation in the future.

CONCLUSION

The clinical severity is partially related with specific gene variants, and detailed individualized data and outcomes were provided. Ear/hearing anomalies were closely connected with CHD7 variants, and were common problems for CHH patients. Simple olfactory assessment underestimated the true olfactory deficit. L. Zhang, Y. Gao, Q. Du, et al. Genetic Profiles and Three-year Follow-up Study of Chinese Males With Congenital Hypogonadotropic Hypogonadism. J Sex Med 2021;XX:XXX-XXX.

Defects in GnRH Neuron Migration/Development and Hypothalamic-Pituitary Signaling Impact Clinical Variability of Kallmann Syndrome

Kallmann syndrome (KS) is a combination of isolated hypogonadotropic hypogonadism (IHH) with olfactory dysfunction, representing a heterogeneous disorder with a broad phenotypic spectrum. The genetic background of KS has not yet been fully established. This study was conducted on 46 Polish KS subjects (41 males, 5 females; average age: 29 years old). The studied KS patients were screened for defects in a 38-gene panel with next-generation sequencing (NGS) technology. The analysis revealed 27 pathogenic and likely pathogenic (P/LP) variants, and 21 variants of uncertain significance (VUS). The P/LP variants were detected in 20 patients (43.5%). The prevalence of oligogenic P/LP defects in selected genes among KS patients was 26% (12/46), whereas the co-occurrence of other variants was detected in 43% (20 probands). The examined KS patients showed substantial genotypic and phenotypic variability. A marked difference in non-reproductive phenotypes, involving defects in genes responsible for GnRH neuron development/migration and genes contributing to pituitary development and signaling, was observed. A comprehensive gene panel for IHH testing enabled the detection of clinically relevant variants in the majority of KS patients, which makes targeted NGS an effective molecular tool. The significance of oligogenicity and the high incidence of alterations in selected genes should be further elucidated.

A partial loss-of-function variant in GNRNR gene in a Chinese cohort with idiopathic hypogonadotropic hypogonadism

BACKGROUND

Idiopathic hypogonadotropic hypogonadism (IHH) is a rare genetic disease attributed to the disorder of hypothalamic-pituitary-gonadal axis. Mutations in the GNRHR gene are one of the most common genetic causes of IHH. Herein, we aimed to investigate GNRHR variants in a Chinese cohort with IHH, and to characterize them at the molecular level.

METHODS

A total of 153 IHH patients were recruited, and variants were detected using a tailored next-generation sequencing panel. GNRHR rare sequencing variant (RSV) was verified using Sanger sequencing. Phenotypic features and therapeutic outcomes of patients were followed up. In order to examine the pathogenicity of the GNRHR RSV, we performed conservative analysis, crystal structure prediction, expression analysis as well as the assessment of ERK1/2 activation and IP3/Ca²⁺ response.

RESULTS

The same heterozygous RSV (p.R240Q) in GNRHR was identified in four sporadic IHH patients. These patients exhibited different severity of testicular development and hormone profile. hCG treatment was effective in improving gonadal development, serum testosterone, and semen quality. The GNRHR RSV has no effect on the expression of mRNA and protein, whereas damaged ERK1/2 activation and inositol triphosphate/calcium signaling.

CONCLUSIONS

The study expands GNRHR mutation spectrum in IHH patients, and reveals that the GNRHR RSV is a partial loss-of-function mutation. Although this heterozygous RSV may not have a significant influence on the pathogenesis of IHH, but its homozygous/ compound status should be paid attention in this research field.

Clinical and molecular features of idiopathic hypogonadotropic hypogonadism in Taiwan: A single center experience

BACKGROUND

Idiopathic (isolated) hypogonadotropic hypogonadism (IHH) is a rare disease that can be classified as Kallmann syndrome (KS) or normosmic IHH (nIHH). This study investigated the phenotype and genotype of IHH in Taiwanese patients.

METHODS

Twenty-six unrelated IHH patients were included in this study and their clinical, hormonal, and radiological findings were analyzed retrospectively. Whole exome sequencing (WES) was performed to identify the etiology.

RESULTS

The 26 patients (M:F = 19:7) were divided into a KS group (n = 11) and a nIHH group (n = 15). The diagnosis was earlier in boys than in girls. Fifteen patients were found to have pathogenic/likely pathogenic (P/LP) variants of IHH-associated genes, and the mutation detection rate was 58%. CHD7, FGFR1, and ANOS1 were the most common genetic etiologies identified in this group. Two patients with nIHH were found to have de novo SOX11 mutations and Coffin-Siris syndrome features. After treatment, the height outcomes and secondary sexual characteristics were significantly improved. There were no obvious differences between the genetically resolved (GR), variants of uncertain significance (VUS) and genetically unresolved groups (GUR).

CONCLUSION

Whole exome sequencing is useful in patients with IHH, and we identified the SOX11 gene as a causal factor in this study. We described the clinical, hormonal, and molecular characteristics, and the treatment outcomes, of Taiwanese patients with IHH, which should aid therapeutic planning and further research.

Analysis of role of aromatic residues in extracellular loop 2 of Prokineticin receptor 2 in ligand binding probed with genetically encoded photo-crosslinkers

Prokineticin 2 (PK2) and Prokineticin 2 beta (PK2β), products of alternative splicing of pk2 gene, are chemokine-like proteins. While PK2 mediates its biological activities by signaling with the same efficiency through two homologous G protein coupled receptors, prokineticin receptor 1 (PKR1) and prokineticin receptor 2 (PKR2), PK2β is able to bind specifically PKR1. Extracellular loop 2 (ECL2) of chemokine receptors is a part of a transmembrane (TM) ligand binding site. In the ECL2 of PKR2 is present, as well as in all chemokine receptors, an aromatic residue cluster, involving tryptophan 212 localized four residues after an ECL2 conserved cysteine, and Phenylalanine 198 located in the top of TM 4. In this work, the photoactivatable unnatural amino acid p-benzoyl-L-phenylalanine is incorporated by amber codon suppression technology into PKR2 in position 212. Experiments of photoactivatable cross-linking demonstrated the role of tryptophan in position 212 for binding the ligand contacting Tryptophan in position 24. We also analyzed the role of Phenylalanine 198 in the specificity of PKRs binding. The comparison of TM-bundle binding sites between PKR1 and PKR2 revealed that they are completely conserved except for one residue: valine 207 in human PKR1, which is phenylalanine 198 in human PKR2. The F198V mutation in PKR2 permits to obtain a receptor able to bind more efficiently PK2β, a ligand highly specific for PKR1.

One4Two®: An Integrated Molecular Approach to Optimize Infertile Couples' Journey

The current diagnostic path of infertile couples is long lasting and often ineffective. Genetic tests, in particular, appear as a limiting step due to their jeopardized use on one side, and to the limited number of genes evaluated on the other. In this context, the development and diffusion, also in routine diagnostic settings, of next generation sequencing (NGS)-based methods for the analyses of several genes in multiple subjects at a time is improving the diagnostic sensitivity of molecular analyses. Thus, we developed One4Two^®, a custom NGS panel to optimize the diagnostic journey of infertile couples. The panel validation was carried out in three steps analyzing a total of 83 subjects. Interestingly, all the previously identified variants were confirmed, assessing the analytic sensitivity of the method. Moreover, additional pathogenic variants have been identified underlying the diagnostic efficacy of the proposed method. One4Two^® allows the simultaneous analysis of infertility-related genes, disease-genes of common inherited diseases, and of polymorphisms related to therapy outcome. Thus, One4Two^® is able to improve the diagnostic journey of infertile couples by simplifying the whole process not only for patients, but also for laboratories and reproduction specialists moving toward an even more personalized medicine.

Molecular chaperones and G protein-coupled receptor maturation and pharmacology

G protein-coupled receptors (GPCRs) are highly conserved versatile signaling molecules located at the plasma membrane that respond to diverse extracellular signals. They regulate almost all physiological processes in the vertebrates. About 35% of current drugs target these receptors. Mutations in these genes have been identified as causes of numerous diseases. The seven transmembrane domain structure of GPCRs implies that the folding of these transmembrane proteins is extremely complicated and difficult. Indeed, many wild type GPCRs are not folded optimally. The most common defect in genetic diseases caused by GPCR mutations is misfolding and failure to reach the plasma membrane where it functions. General molecular chaperones aid the folding of all proteins, including GPCRs, by preventing aggregation, promoting folding and disaggregating small aggregates. Some GPCRs need additional receptor-specific chaperones to assist their folding. Many of these receptor-specific chaperones interact with additional receptors and alter receptor pharmacology, expanding the understanding of these chaperone proteins.

Molecular genetic diagnostics of hypogonadotropic hypogonadism: from panel design towards result interpretation in clinical practice

Congenital hypogonadotropic hypogonadism (CHH) is a clinically and genetically heterogeneous congenital disease. Symptoms cover a wide spectrum from mild forms to complex phenotypes due to gonadotropin-releasing hormone (GnRH) deficiency. To date, more than 40 genes have been identified as pathogenic cause of CHH. These genes could be grouped into two major categories: genes controlling development and GnRH neuron migration and genes being responsible for neuroendocrine regulation and GnRH neuron function. High-throughput, next-generation sequencing (NGS) allows to analyze numerous gene sequences at the same time. Nowadays, whole exome or whole genome datasets could be investigated in clinical genetic diagnostics due to their favorable cost-benefit. The increasing genetic data generated by NGS reveal novel candidate genes and gene variants with unknown significance (VUSs). To provide clinically valuable genetic results, complex clinical and bioinformatics work are needed. The multifaceted genetics of CHH, the variable mode of inheritance, the incomplete penetrance, variable expressivity and oligogenic characteristics further complicate the interpretation of the genetic variants detected. The objective of this work, apart from reviewing the currently known genes associated with CHH, was to summarize the advantages and disadvantages of the NGS-based platforms and through the authors' own practice to guide through the whole workflow starting from gene panel design, performance analysis and result interpretation. Based on our results, a genetic diagnosis was clearly identified in 21% of cases tested (8/38).

Genetics of congenital hypogonadotropic hypogonadism: peculiarities and phenotype of an oligogenic disease

A genetic basis of congenital isolated hypogonadotropic hypogonadism (CHH) can be defined in almost 50% of cases, albeit not necessarily the complete genetic basis. Next-generation sequencing (NGS) techniques have led to the discovery of a great number of loci, each of which has illuminated our understanding of human gonadotropin-releasing hormone (GnRH) neurons, either in respect of their embryonic development or their neuroendocrine regulation as the "pilot light" of human reproduction. However, because each new gene linked to CHH only seems to underpin another small percentage of total patient cases, we are still far from achieving a comprehensive understanding of the genetic basis of CHH. Patients have generally not benefited from advances in genetics in respect of novel therapies. In most cases, even genetic counselling is limited by issues of apparent variability in expressivity and penetrance that are likely underpinned by oligogenicity in respect of known and unknown genes. Robust genotype-phenotype relationships can generally only be established for individuals who are homozygous, hemizygous or compound heterozygotes for the same gene of variant alleles that are predicted to be deleterious. While certain genes are purely associated with normosmic CHH (nCHH) some purely with the anosmic form (Kallmann syndrome-KS), other genes can be associated with both nCHH and KS-sometimes even within the same kindred. Even though the anticipated genetic overlap between CHH and constitutional delay in growth and puberty (CDGP) has not materialised, previously unanticipated genetic relationships have emerged, comprising conditions of combined (or multiple) pituitary hormone deficiency (CPHD), hypothalamic amenorrhea (HA) and CHARGE syndrome. In this review, we report the current evidence in relation to phenotype and genetic peculiarities regarding 60 genes whose loss-of-function variants can disrupt the central regulation of reproduction at many levels: impairing GnRH neurons migration, differentiation or activation; disrupting neuroendocrine control of GnRH secretion; preventing GnRH neuron migration or function and/or gonadotropin secretion and action.

Genetic analysis of adult Slovenian patients with combined pituitary hormone deficiency

PURPOSE

Among genetic causes of combined pituitary hormone deficiency (CPHD), mutations of genes coding for transcription factors involved in pituitary development have been implicated. Congenital CPHD is a rare disease; therefore, it is important to expand the knowledge about incidence and regional distribution of specific mutations. The aim of this paper is to report results of genetic analyses of adult Slovenian patients with CPHD.

METHODS

Twenty-three adult Slovenian patients with early childhood onset CPHD were included in the study. Blood samples were collected through the GENHYPOPIT network to assess possible mutations of six genes (PROP1/HESX1/LHX4/LHX3/POU1F1) involved in the pituitary development following an established algorithm.

RESULTS

In seven out of 23 patients (30%) a specific mutation in genes encoding pituitary transcription factors was discovered. In five patients, two different mutations of the PROP1 gene (c.150delA and c.301-302delAG) were identified. One patient was heterozygous for a missense variant in the LHX4 gene. Additionally, one patient was positive for a mutation in the gene coding for prokineticin receptor-2.

CONCLUSIONS

Our study confirms that the two most common mutations of the PROP1 gene globally are also the most frequent mutations in the cohort of adult Slovenian patients with CHPD. Other mutations of pituitary transcription factor genes are extremely rare.

Identification of gene variants in 130 Han Chinese patients with hypospadias by targeted next-generation sequencing

Background

Hypospadias is a common congenital malformation of male external genitalia, which mainly manifests as an abnormal urethral opening on the ventral side of the penis. The etiology and clinical phenotype of hypospadias is highly heterogeneous, and its clinical diagnosis is challenging. Currently, over 70% of patients have an unknown etiology. Here, we performed a targeted analysis of gene mutations in 130 patients with hypospadias of unknown etiology to find the precise genetic cause.

Methods

We developed a targeted next‐generation sequencing (NGS) panel, encompassing the exon coding regions of 105 genes involved in external genitalia and urogenital tract development and performed sequencing analysis on 130 children with hypospadias of unknown etiology.

Results

In total, 25 patients with hypospadias (19.2%) were found to have 20 mutations among the nine genes involved in external genitalia and urogenital tract development, including 16 reported and four novel mutation sites. Twenty‐two patients (16.9%) had diagnostic variants. Multiple genetic mutations were identified in three of the 25 patients. Hypospadias combined with micropenis was the most common phenotype (68%) in 25 patients.

Conclusions

Higher frequency mutations were identified in SRD5A2 (52%) and AR (24%) in our patient cohort. Middle or posterior hypospadias with micropenis may be significant indicators of genetic variations. Polygenic inheritance may be a rare genetic cause of hypospadias.

Translating genomics to the clinical diagnosis of disorders/differences of sex development

The medical and psychosocial challenges faced by patients living with Disorders/Differences of Sex Development (DSD) and their families can be alleviated by a rapid and accurate diagnostic process. Clinical diagnosis of DSD is limited by a lack of standardization of anatomical and endocrine phenotyping and genetic testing, as well as poor genotype/phenotype correlation. Historically, DSD genes have been identified through positional cloning of disease-associated variants segregating in families and validation of candidates in animal and in vitro modeling of variant pathogenicity. Owing to the complexity of conditions grouped under DSD, genome-wide scanning methods are better suited for identifying disease causing gene variant(s) and providing a clinical diagnosis. Here, we review a number of established genomic tools (karyotyping, chromosomal microarrays and exome sequencing) used in clinic for DSD diagnosis, as well as emerging genomic technologies such as whole-genome (short-read) sequencing, long-read sequencing, and optical mapping used for novel DSD gene discovery. These, together with gene expression and epigenetic studies can potentiate the clinical diagnosis of DSD diagnostic rates and enhance the outcomes for patients and families.

Evidence for a Common Genetic Origin of Classic and Milder Adult-Onset Forms of Isolated Hypogonadotropic Hypogonadism

Multiple metabolic and inflammatory mechanisms are considered the determinants of acquired functional isolated hypogonadotropic hypogonadism (IHH) in males, whereas classic IHH is a rare congenital condition with a strong genetic background. Since we recently uncovered a frequent familiarity for classic IHH among patients with mild adult-onset hypogonadism (AO-IHH), here we performed a genetic characterization by next generation sequencing of 160 males with classic or “functional” forms. The prevalence of rare variants in 28 candidate genes was significantly higher than in controls in all IHH patients, independently of the age of IHH onset, degree of hypogonadism or presence of obesity. In fact, it did not differ among patients with classic or milder forms of IHH, however particular genes appear to be more specifically associated with one or the other category of IHH. ROC curves showed that Total Testosterone <6.05 nmol/L and an age of onset <41 years are sensitive cutoffs to identify patients with significantly higher chances of harboring rare IHH gene variants. In conclusion, rare IHH genes variants can frequently predispose to AO-IHH with acquired mild hormonal deficiencies. The identification of a genetic predisposition can improve the familial and individual management of AO-IHH and explain the heritability of congenital IHH.

Modeling mutant/wild-type interactions to ascertain pathogenicity of PROKR2 missense variants in patients with isolated GnRH deficiency

A major challenge in human genetics is the validation of pathogenicity of heterozygous missense variants. This problem is well-illustrated by PROKR2 variants associated with Isolated GnRH Deficiency (IGD). Homozygous, loss of function variants in PROKR2 was initially implicated in autosomal recessive IGD; however, most IGD-associated PROKR2 variants are heterozygous. Moreover, while IGD patient cohorts are enriched for PROKR2 missense variants similar rare variants are also found in normal individuals. To elucidate the pathogenic mechanisms distinguishing IGD-associated PROKR2 variants from rare variants in controls, we assessed 59 variants using three approaches: (i) in silico prediction, (ii) traditional in vitro functional assays across three signaling pathways with mutant-alone transfections, and (iii) modified in vitro assays with mutant and wild-type expression constructs co-transfected to model in vivo heterozygosity. We found that neither in silico analyses nor traditional in vitro assessments of mutants transfected alone could distinguish IGD variants from control variants. However, in vitro co-transfections revealed that 15/34 IGD variants caused loss-of-function (LoF), including 3 novel dominant-negatives, while only 4/25 control variants caused LoF. Surprisingly, 19 IGD-associated variants were benign or exhibited LoF that could be rescued by WT co-transfection. Overall, variants that were LoF in ≥ 2 signaling assays under co-transfection conditions were more likely to be disease-associated than benign or 'rescuable' variants. Our findings suggest that in vitro modeling of WT/Mutant interactions increases the resolution for identifying causal variants, uncovers novel dominant negative mutations, and provides new insights into the pathogenic mechanisms underlying heterozygous PROKR2 variants.

PROKR2 mutations in idiopathic hypogonadotropic hypogonadism: selective disruption of the binding to a Gα-protein leads to biased signaling

Idiopathic hypogonadotropic hypogonadism (IHH) is a rare disorder caused by the deficient production, secretion, or action of gonadotropin-releasing hormone. Prokineticin (PROK) receptor 2 ( PROKR2), a causative gene for IHH, encodes a GPCR PROKR2. When PROKR2 binds to its ligands PROKs, it may activate several signaling pathways, including IP3/Ca²⁺, MAPK, and cAMP pathways. However, the mutational spectrum of PROKR2 in Chinese patients with IHH has not been established. In the present study, we found that up to 13.3% (18/135) of patients with IHH in China carried mutations in PROKR2. Most of the variants in this study were private; however, a PROKR2 (c.533G > C; p.W178S) mutation was identified in 10 independent patients, implying a possible founder mutation. Functional studies indicated that 6 novel PROKR2 mutations led to decreased signaling to various extents. Two IHH-associated mutations (L218P and R270H) disrupted Gαq-dependent signaling but maintained normal Gαs and ERK1/2 signaling. A glutathione S-transferase pull-down experiment demonstrated that R270H mutation disrupted the interaction of intracellular loop 3 of PROKR2 to Gαq protein but not Gαs protein. Our results indicated that selective disruption of the interaction with a specific Gα-protein might underlie the biased signaling for certain IHH-associated PROKR2 mutations.-Zhao, Y., Wu, J., Jia, H., Wang, X., Zheng, R., Jiang, F., Chen, D.-N., Chen, Z., Li, J.-D. PROKR2 mutations in idiopathic hypogonadotropic hypogonadism: selective disruption of the binding to a Gα-protein leads to biased signaling.

The Prokineticins: Neuromodulators and Mediators of Inflammation and Myeloid Cell-Dependent Angiogenesis

The mammalian prokineticins family comprises two conserved proteins, EG-VEGF/PROK1 and Bv8/PROK2, and their two highly related G protein-coupled receptors, PKR1 and PKR2. This signaling system has been linked to several important biological functions, including gastrointestinal tract motility, regulation of circadian rhythms, neurogenesis, angiogenesis and cancer progression, hematopoiesis, and nociception. Mutations in PKR2 or Bv8/PROK2 have been associated with Kallmann syndrome, a developmental disorder characterized by defective olfactory bulb neurogenesis, impaired development of gonadotropin-releasing hormone neurons, and infertility. Also, Bv8/PROK2 is strongly upregulated in neutrophils and other inflammatory cells in response to granulocyte-colony stimulating factor or other myeloid growth factors and functions as a pronociceptive mediator in inflamed tissues as well as a regulator of myeloid cell-dependent tumor angiogenesis. Bv8/PROK2 has been also implicated in neuropathic pain. Anti-Bv8/PROK2 antibodies or small molecule PKR inhibitors ameliorate pain arising from tissue injury and inhibit angiogenesis and inflammation associated with tumors or some autoimmune disorders.

Prokineticins and their G protein-coupled receptors in health and disease

Prokineticins are two conserved small proteins (~8kDa), prokineticin 1 (PROK1; also called EG-VEGF) and prokineticin 2 (PROK2; also called Bv8), with an N-terminal AVITGA sequence and 10 cysteines forming 5 disulfide bridges. PROK1 and PROK2 bind to two highly related G protein-coupled receptors (GPCRs), prokineticin receptor 1 (PROKR1) and prokineticin receptor 2 (PROKR2). Prokineticins and their receptors are widely expressed. PROK1 is predominantly expressed in peripheral tissues, especially steroidogenic organs, whereas PROK2 is mainly expressed in the central nervous system and nonsteroidogenic cells of the testes. Prokineticins signaling has been implicated in several important physiological functions, including gastrointestinal smooth muscle contraction, circadian rhythm regulation, neurogenesis, angiogenesis, pain perception, mood regulation, and reproduction. Dysregulation of prokineticins signaling has been observed in a variety of diseases, such as cancer, ischemia, and neurodegeneration, in which prokineticins signaling seems to be a promising therapeutic target. Based on the phenotypes of knockout mice, PROKR2 and PROK2 have recently been identified as causative genes for idiopathic hypogonadotropic hypogonadism, a developmental disorder characterized by impaired development of gonadotropin-releasing hormone neurons and infertility. In vitro functional studies with these disease-associated PROKR2 mutations uncovered some novel features for this receptor, such as biased signaling, which may be used to understand GPCR signaling regulation in general.

GENETICS IN ENDOCRINOLOGY: Genetic counseling for congenital hypogonadotropic hypogonadism and Kallmann syndrome: new challenges in the era of oligogenism and next-generation sequencing

Congenital hypogonadotropic hypogonadism (CHH) and Kallmann syndrome (KS) are rare, related diseases that prevent normal pubertal development and cause infertility in affected men and women. However, the infertility carries a good prognosis as increasing numbers of patients with CHH/KS are now able to have children through medically assisted procreation. These are genetic diseases that can be transmitted to patients' offspring. Importantly, patients and their families should be informed of this risk and given genetic counseling. CHH and KS are phenotypically and genetically heterogeneous diseases in which the risk of transmission largely depends on the gene(s) responsible(s). Inheritance may be classically Mendelian yet more complex; oligogenic modes of transmission have also been described. The prevalence of oligogenicity has risen dramatically since the advent of massively parallel next-generation sequencing (NGS) in which tens, hundreds or thousands of genes are sequenced at the same time. NGS is medically and economically more efficient and more rapid than traditional Sanger sequencing and is increasingly being used in medical practice. Thus, it seems plausible that oligogenic forms of CHH/KS will be increasingly identified making genetic counseling even more complex. In this context, the main challenge will be to differentiate true oligogenism from situations when several rare variants that do not have a clear phenotypic effect are identified by chance. This review aims to summarize the genetics of CHH/KS and to discuss the challenges of oligogenic transmission and also its role in incomplete penetrance and variable expressivity in a perspective of genetic counseling.

Intracellular Trafficking of Gonadotropin Receptors in Health and Disease

Gonadotropin receptors belong to the highly conserved subfamily of the G protein-coupled receptor (GPCR) superfamily, the so-called Rhodopsin-like family (class A), which is the largest class of GPCRs and currently a major drug target. Both the follicle-stimulating hormone receptor (FSHR) and the luteinizing hormone/chorionic gonadotropin hormone receptor (LHCGR) are mainly located in the gonads where they play key functions associated to essential reproductive functions. As any other protein, gonadotropin receptors must be properly folded into a mature tertiary conformation compatible with quaternary assembly and endoplasmic reticulum export to the cell surface plasma membrane. Several primary and secondary structural features, including presence of particular amino acid residues and short motifs and in addition, posttranslational modifications, regulate intracellular trafficking of gonadotropin receptors to the plasma membrane as well as internalization and recycling of the receptor back to the cell surface after activation by agonist. Inactivating mutations of gonadotropin receptors may derive from receptor misfolding and lead to absent or reduced plasma membrane expression of the altered receptor, thereby manifesting an array of phenotypical abnormalities mostly characterized by reproductive failure and/or abnormal or absence of development of secondary sex characteristics. In this chapter we review the structural requirements necessary for intracellular trafficking of the gonadotropin receptors, and describe how mutations in these receptors may lead to receptor misfolding and disease in humans.

Molecular genetic and clinical delineation of 22 patients with congenital hypogonadotropic hypogonadism

BACKGROUND

Congenital hypogonadotropic hypogonadism (CHH) is classified as Kallmann syndrome (KS) with anosmia/hyposmia or normosmic (n)CHH. Here, we investigated the genetic causes and phenotype-genotype correlations in Japanese patients with CHH.

METHODS

We enrolled 22 Japanese patients with CHH from 21 families (18 patients with KS and 4 with nCHH) and analyzed 27 genes implicated in CHH by next-generation and Sanger sequencing.

RESULTS

We detected 12 potentially pathogenic mutations in 11 families, with three having a mutation in ANOS1 (X-linked recessive); three and four having a mutation in FGFR1 and CHD7, respectively (autosomal dominant); and one having two TACR3 mutations (autosomal recessive). Among four patients with KS carrying a CHD7 mutation, one had perceptive deafness and two had a cleft lip/palate.

CONCLUSIONS

The frequency of CHH genes in the Japanese was compatible with previous reports, except that CHD7 mutations might be more common. Furthermore, partial phenotype-genotype correlations were demonstrated in our cohort.

Digenic Inheritance of PROKR2 and WDR11 Mutations in Pituitary Stalk Interruption Syndrome

CONTEXT

Pituitary stalk interruption syndrome (PSIS, ORPHA95496) is a congenital defect of the pituitary gland characterized by the triad of a very thin/interrupted pituitary stalk, an ectopic (or absent) posterior pituitary gland, and hypoplasia or aplasia of the anterior pituitary gland. Complex genetic patterns of inheritance of this disorder are increasingly recognized.

OBJECTIVE

The objective of this study was to identify a genetic cause of PSIS in an affected child.

METHODS

Whole exome sequencing (WES) was performed by using standard techniques, with prioritized genetic variants confirmed via Sanger sequencing. To investigate the effects of one candidate variant on mutant WDR11 function, Western blotting and coimmunofluorescence were used to assess binding capacity, and leptomycin B exposure along with immunofluorescence was used to assess nuclear localization.

RESULTS

We describe a child who presented in infancy with combined pituitary hormone deficiencies and whose brain imaging demonstrated a small anterior pituitary, ectopic posterior pituitary, and a thin, interrupted stalk. WES demonstrated heterozygous missense mutations in two genes required for pituitary development, a known loss-of-function mutation in PROKR2 (c.253C>T;p.R85C) inherited from an unaffected mother, and a WDR11 (c.1306A>G;p.I436V) mutation inherited from an unaffected father. Mutant WDR11 loses its capacity to bind to its functional partner, EMX1, and to localize to the nucleus.

CONCLUSIONS

WES in a child with PSIS and his unaffected family implicates a digenic mechanism of inheritance. In cases of hypopituitarism in which there is incomplete segregation of a monogenic genotype with the phenotype, the possibility that a second genetic locus is involved should be considered.

Sexually dimorphic distribution of Prokr2 neurons revealed by the Prokr2-Cre mouse model

Prokineticin receptor 2 (PROKR2) is predominantly expressed in the mammalian central nervous system. Loss-of-function mutations of PROKR2 in humans are associated with Kallmann syndrome due to the disruption of gonadotropin releasing hormone neuronal migration and deficient olfactory bulb morphogenesis. PROKR2 has been also implicated in the neuroendocrine control of GnRH neurons post-migration and other physiological systems. However, the brain circuitry and mechanisms associated with these actions have been difficult to investigate mainly due to the widespread distribution of Prokr2-expressing cells, and the lack of animal models and molecular tools. Here, we describe the generation, validation and characterization of a new mouse model that expresses Cre recombinase driven by the Prokr2 promoter, using CRISPR-Cas9 technology. Cre expression was visualized using reporter genes, tdTomato and GFP, in males and females. Expression of Cre-induced reporter genes was found in brain sites previously described to express Prokr2, e.g., the paraventricular and the suprachiasmatic nuclei, and the area postrema. The Prokr2-Cre mouse model was further validated by colocalization of Cre-induced GFP and Prokr2 mRNA. No disruption of Prokr2 expression, GnRH neuronal migration or fertility was observed. Comparative analysis of Prokr2-Cre expression in male and female brains revealed a sexually dimorphic distribution confirmed by in situ hybridization. In females, higher Cre activity was found in the medial preoptic area, ventromedial nucleus of the hypothalamus, arcuate nucleus, medial amygdala and lateral parabrachial nucleus. In males, Cre was higher in the amygdalo-hippocampal area. The sexually dimorphic pattern of Prokr2 expression indicates differential roles in reproductive function and, potentially, in other physiological systems.

Variants in congenital hypogonadotrophic hypogonadism genes identified in an Indonesian cohort of 46,XY under-virilised boys

Background

Congenital hypogonadotrophic hypogonadism (CHH) and Kallmann syndrome (KS) are caused by disruption to the hypothalamic-pituitary-gonadal (H-P-G) axis. In particular, reduced production, secretion or action of gonadotrophin-releasing hormone (GnRH) is often responsible. Various genes, many of which play a role in the development and function of the GnRH neurons, have been implicated in these disorders. Clinically, CHH and KS are heterogeneous; however, in 46,XY patients, they can be characterised by under-virilisation phenotypes such as cryptorchidism and micropenis or delayed puberty. In rare cases, hypospadias may also be present.

Results

Here, we describe genetic mutational analysis of CHH genes in Indonesian 46,XY disorder of sex development patients with under-virilisation. We present 11 male patients with varying degrees of under-virilisation who have rare variants in known CHH genes. Interestingly, many of these patients had hypospadias.

Conclusions

We postulate that variants in CHH genes, in particular PROKR2, PROK2, WDR11 and FGFR1 with CHD7, may contribute to under-virilisation phenotypes including hypospadias in Indonesia.

A Novel Drug-Mouse Phenotypic Similarity Method Detects Molecular Determinants of Drug Effects

The molecular mechanisms that translate drug treatment into beneficial and unwanted effects are largely unknown. We present here a novel approach to detect gene-drug and gene-side effect associations based on the phenotypic similarity of drugs and single gene perturbations in mice that account for the polypharmacological property of drugs. We scored the phenotypic similarity of human side effect profiles of 1,667 small molecules and biologicals to profiles of phenotypic traits of 5,384 mouse genes. The benchmarking with known relationships revealed a strong enrichment of physical and indirect drug-target connections, causative drug target-side effect links as well as gene-drug links involved in pharmacogenetic associations among phenotypically similar gene-drug pairs. The validation by in vitro assays and the experimental verification of an unknown connection between oxandrolone and prokineticin receptor 2 reinforces the ability of this method to provide new molecular insights underlying drug treatment. Thus, this approach may aid in the proposal of novel and personalized treatments.

In order to avoid unwanted effects of current drug interventions, it is necessary to expand the knowledge of the molecular mechanisms related to drug action. Side effects offer insight into drug action, as for example similar side effects of unrelated drugs can be caused by their common off-targets. Moreover, the phenotypes of systematic single gene perturbation screenings in mice strongly contribute to the comprehension of gene function. Here, we present a novel approach that detects molecular interactions of drugs based on the phenotypic similarity of drugs and mouse models. The method is benchmarked with diverse data sets including drug-target interactions as well as gene-drug links of pharmacogenetic associations and validated by in vitro assays.

Association between polymorphisms of prokineticin receptor (PKR1 rs4627609 and PKR2 rs6053283) and recurrent pregnancy loss

Recurrent pregnancy loss (RPL) is a condition with complex etiologies, to which both genetic and environmental factors may contribute. During the last decade, studies indicated that the expression patterns of the prokineticin receptor (PKR1 and PKR2) are closely related to early pregnancy. However, there are few studies on the role of PKR1 and PKR2 in RPL. In this study, we purpose to investigate the association between polymorphisms of the prokineticin receptor (PKR1 rs4627609 and PKR2 rs6053283) and RPL on a group of 93 RPL cases and 169 healthy controls. Genotyping of the single nucleotide polymorphisms (SNPs) was performed using a Sequenom MassARRAY iPLEX system. The results revealed a significant association between PKR2 rs6053283 polymorphism and RPL (P=0.003), whereas no association was observed between PKR1 rs4627609 polymorphism and RPL (P=0.929) in the Chinese Han population.

Computational Analysis of Missense Variants of G Protein-Coupled Receptors Involved in the Neuroendocrine Regulation of Reproduction

INTRODUCTION

Many missense variants in G protein-coupled receptors (GPCRs) involved in the neuroendocrine regulation of reproduction have been identified by phenotype-driven or large-scale exome sequencing. Computational functional prediction analysis is commonly performed to evaluate their impact on receptor function.

METHODS

To assess the performance and outcome of functional prediction analyses for these GPCRs, we performed a statistical analysis of the prediction performance of SIFT and PolyPhen-2 for variants with documented biological function as well as variants retrieved from Ensembl. We obtained missense variants with documented biological function testing from patients with reproductive disorders from a comprehensive literature search. Missense variants from individuals with known reproductive disorders were retrieved from the Human Gene Mutation Database. Missense variants from the general population were retrieved from the Ensembl genome database.

RESULTS

The accuracies of SIFT and PolyPhen-2 were 83 and 85%, respectively. The performance of both prediction tools was greater in predicting loss-of-function variants (SIFT: 92%; PolyPhen-2: 95%) than in predicting variants that did not affect function (SIFT: 54%; PolyPhen-2: 57%). Concordance between SIFT and PolyPhen-2 did not improve accuracy. Surprisingly, approximately half of the variants retrieved from Ensembl were predicted as loss-of-function variants by SIFT (47%) and PolyPhen-2 (54%).

CONCLUSION

Our findings provide new guidance for interpreting the results and limitations of computational functional prediction analyses for GPCRs and will help to determine which variants require biological function testing. In addition, our findings raise important questions regarding the link between genotype and phenotype in the general population.