Classes and predictors of reversal in male patients with congenital hypogonadotropic hypogonadism: a cross-sectional study of six international referral centres

BACKGROUND

Although some male patients with congenital hypogonadotropic hypogonadism (CHH) undergo spontaneous reversal following treatment, predictors of reversal remain elusive. We aimed to assemble the largest cohort of male patients with CHH reversal to date and identify distinct classes of reversal.

METHODS

This multicentre cross-sectional study was conducted in six international CHH referral centres in Brazil, Finland, France, Italy, the UK, and the USA. Adult men with CHH (ie, absent or incomplete spontaneous puberty by age 18 years, low serum testosterone concentrations, and no identifiable cause of hypothalamic-pituitary-gonadal [HPG] axis dysfunction) were eligible for inclusion. CHH reversal was defined as spontaneous recovery of HPG axis function off treatment. Centres provided common data elements on patient phenotype, clinical assessment, and genetics using a structured, harmonised data collection form developed by COST Action BM1105. Latent class mixture modelling (LCMM) was applied to establish whether at least two distinct classes of reversal could be identified and differentially predicted, and results were compared with a cohort of patients without CHH reversal to identify potential predictors of reversal. The primary outcome was the presence of at least two distinct classes of reversal.

FINDINGS

A total of 87 male patients with CHH reversal and 108 without CHH reversal were included in the analyses. LCMM identified two distinct reversal classes (75 [86%] in class 1 and 12 [14%] in class 2) on the basis of mean testicular volume, micropenis, and serum follicle-stimulating hormone (FSH) concentration. Classification probabilities were robust (0·998 for class 1 and 0·838 for class 2) and modelling uncertainty was low (entropy 0·90). Compared with class 1, patients in class 2 had significantly larger testicular volume (p<0·0001), no micropenis, and higher serum FSH concentrations (p=0·041), consistent with the Pasqualini syndrome (fertile eunuch) subtype of CHH. Patients without CHH reversal were more likely to have anosmia (p=0·016), cryptorchidism (p=0·0012), complete absence of puberty (testicular volume <4 cm³; p=0·0016), and two or more rare genetic variants (ie, oligogenicity; p=0·0001). Among patients who underwent genetic testing, no patients (of 75) with CHH reversal had a rare pathogenic ANOS1 variant compared with ten (11%) of 95 patients without CHH reversal. Individuals with CHH reversal had a significantly higher rate of rare variants in GNRHR than did those without reversal (nine [12%] of 75 vs three [3%] of 95; p=0·025).

INTERPRETATION

Applying LCMM to a large cohort of male patients with CHH reversal uncovered two distinct classes of reversal. Genetic investigation combined with careful clinical phenotyping could help surveillance of reversal after withdrawing treatment, representing the first tailored management approach for male patients with this rare endocrine disorder.

FUNDING

National Institutes of Health National Center for Advancing Translational Sciences; Ministry of Health, Rome, Italy; Ministry of University, Rome, Italy; National Institutes of Health Eunice Kennedy Shriver National Institute of Child Health and Human Development; and the Josiah Macy Jr Foundation.

TRANSLATION

For the Italian translation of the abstract see Supplementary Materials section.

Genome-wide analyses identify 21 infertility loci and over 400 reproductive hormone loci across the allele frequency spectrum

Genome-wide association studies (GWASs) may help inform treatments for infertility, whose causes remain unknown in many cases. Here we present GWAS meta-analyses across six cohorts for male and female infertility in up to 41,200 cases and 687,005 controls. We identified 21 genetic risk loci for infertility (P≤5E-08), of which 12 have not been reported for any reproductive condition. We found positive genetic correlations between endometriosis and all-cause female infertility (rg=0.585, P=8.98E-14), and between polycystic ovary syndrome and anovulatory infertility (rg=0.403, P=2.16E-03). The evolutionary persistence of female infertility-risk alleles in EBAG9 may be explained by recent directional selection. We additionally identified up to 269 genetic loci associated with follicle-stimulating hormone (FSH), luteinising hormone, oestradiol, and testosterone through sex-specific GWAS meta-analyses (N=6,095-246,862). While hormone-associated variants near FSHB and ARL14EP colocalised with signals for anovulatory infertility, we found no rg between female infertility and reproductive hormones (P>0.05). Exome sequencing analyses in the UK Biobank (N=197,340) revealed that women carrying testosterone-lowering rare variants in GPC2 were at higher risk of infertility (OR=2.63, P=1.25E-03). Taken together, our results suggest that while individual genes associated with hormone regulation may be relevant for fertility, there is limited genetic evidence for correlation between reproductive hormones and infertility at the population level. We provide the first comprehensive view of the genetic architecture of infertility across multiple diagnostic criteria in men and women, and characterise its relationship to other health conditions.

Contributions of common genetic variants to constitutional delay of puberty and idiopathic hypogonadotropic hypogonadism

CONTEXT

Constitutional delay of puberty (CDP) is highly heritable, but the genetic basis for CDP is largely unknown. Idiopathic hypogonadotropic hypogonadism (IHH) can be caused by rare genetic variants, but in about half of cases, no rare-variant cause is found.

OBJECTIVE

To determine whether common genetic variants that influence pubertal timing contribute to CDP and IHH.

DESIGN

Case-control study.

PARTICIPANTS

80 individuals with CDP; 301 with normosmic IHH, and 348 with Kallmann syndrome; control genotyping data from unrelated studies.

MAIN OUTCOME MEASURES

Polygenic scores (PGS) based on genome-wide association studies for timing of male pubertal hallmarks and age at menarche (AAM).

RESULTS

The CDP cohort had higher PGS for male pubertal hallmarks and for AAM compared to controls (for male hallmarks, Cohen's d = 0.85, p = 1 × 10-16; for AAM, d = 0.67, p = 1 × 10-10). The normosmic IHH cohort also had higher PGS for male hallmarks compared to controls, but the difference was smaller (male hallmarks d = 0.20, p = 0.003; AAM d = 0.10, p = 0.055). No differences were seen for the KS cohort compared to controls (male hallmarks d = 0.04, p = 0.45; AAM d = -0.03, p = 0.86).

CONCLUSIONS

Common genetic variants that influence pubertal timing in the general population contribute strongly to the genetics of CDP, weakly to normosmic IHH, and potentially not at all to KS. These findings demonstrate that the common-variant genetics of CDP and normosmic IHH are largely but not entirely distinct.

Prevalence of Deleterious Variants in MC3R in Patients With Constitutional Delay of Growth and Puberty

CONTEXT

The melanocortin 3 receptor (MC3R) has recently emerged as a critical regulator of pubertal timing, linear growth, and the acquisition of lean mass in humans and mice. In population-based studies, heterozygous carriers of deleterious variants in MC3R report a later onset of puberty than noncarriers. However, the frequency of such variants in patients who present with clinical disorders of pubertal development is currently unknown.

OBJECTIVE

This work aimed to determine whether deleterious MC3R variants are more frequently found in patients clinically presenting with constitutional delay of growth and puberty (CDGP) or normosmic idiopathic hypogonadotropic hypogonadism (nIHH).

METHODS

We examined the sequence of MC3R in 362 adolescents with a clinical diagnosis of CDGP and 657 patients with nIHH, experimentally characterized the signaling properties of all nonsynonymous variants found and compared their frequency to that in 5774 controls from a population-based cohort. Additionally, we established the relative frequency of predicted deleterious variants in individuals with self-reported delayed vs normally timed menarche/voice-breaking in the UK Biobank cohort.

RESULTS

MC3R loss-of-function variants were infrequent but overrepresented in patients with CDGP (8/362 [2.2%]; OR = 4.17; P = .001). There was no strong evidence of overrepresentation in patients with nIHH (4/657 [0.6%]; OR = 1.15; P = .779). In 246 328 women from the UK Biobank, predicted deleterious variants were more frequently found in those self-reporting delayed (aged ≥16 years) vs normal age at menarche (OR = 1.66; P = 3.90E-07).

CONCLUSION

We have found evidence that functionally damaging variants in MC3R are overrepresented in individuals with CDGP but are not a common cause of this phenotype.

How human genetic context can inform pathogenicity classification: FGFR1 variation in idiopathic hypogonadotropic hypogonadism

Precision medicine requires precise genetic variant interpretation, yet many disease-associated genes have unresolved variants of unknown significance (VUS). We analyzed variants in a well-studied gene, FGFR1, a common cause of Idiopathic Hypogonadotropic Hypogonadism (IHH) and examined whether regional genetic enrichment of missense variants could improve variant classification. FGFR1 rare sequence variants (RSVs) were examined in a large cohort to (i) define regional genetic enrichment, (ii) determine pathogenicity based on the American College of Medical Genetics/Association for Molecular Pathology (ACMG/AMP) variant classification framework, and (iii) characterize the phenotype of FGFR1 variant carriers by variant classification. A total of 143 FGFR1 RSVs were identified in 175 IHH probands (n = 95 missense, n = 48 protein-truncating variants). FGFR1 missense RSVs showed regional enrichment across biologically well-defined domains: D1, D2, D3, and TK domains and linker regions (D2-D3, TM-TK). Using these defined regions of enrichment to augment the ACMG/AMP classification reclassifies 37% (20/54) of FGFR1 missense VUS as pathogenic or likely pathogenic (PLP). Non-proband carriers of FGFR1 missense VUS variants that were reclassified as PLP were more likely to express IHH or IHH-associated phenotypes [anosmia or delayed puberty] than non-proband carriers of FGFR1 missense variants that remained as VUS (76.9% vs 34.7%, p = 0.035). Using the largest cohort of FGFR1 variant carriers, we show that integration of regional genetic enrichment as moderate evidence for pathogenicity improves the classification of VUS and that reclassified variants correlated with phenotypic expressivity. The addition of regional genetic enrichment to the ACMG/AMP guidelines may improve clinical variant interpretation.

POU6F2 mutation in humans with pubertal failure alters GnRH transcript expression

Idiopathic hypogonadotropic hypogonadism (IHH) is characterized by the absence of pubertal development and subsequent impaired fertility often due to gonadotropin-releasing hormone (GnRH) deficits. Exome sequencing of two independent cohorts of IHH patients identified 12 rare missense variants in POU6F2 in 15 patients. POU6F2 encodes two distinct isoforms. In the adult mouse, expression of both isoform1 and isoform2 was detected in the brain, pituitary, and gonads. However, only isoform1 was detected in mouse primary GnRH cells and three immortalized GnRH cell lines, two mouse and one human. To date, the function of isoform2 has been verified as a transcription factor, while the function of isoform1 has been unknown. In the present report, bioinformatics and cell assays on a human-derived GnRH cell line reveal a novel function for isoform1, demonstrating it can act as a transcriptional regulator, decreasing GNRH1 expression. In addition, the impact of the two most prevalent POU6F2 variants, identified in five IHH patients, that were located at/or close to the DNA-binding domain was examined. Notably, one of these mutations prevented the repression of GnRH transcripts by isoform1. Normally, GnRH transcription increases as GnRH cells mature as they near migrate into the brain. Augmentation earlier during development can disrupt normal GnRH cell migration, consistent with some POU6F2 variants contributing to the IHH pathogenesis.

Reproductive Phenotypes and Genotypes in Men With IHH

CONTEXT

Isolated hypogonadotropic hypogonadism (IHH) is phenotypically and genetically heterogeneous.

OBJECTIVE

This work aimed to determine the correlation between genotypic severity with pubertal and neuroendocrine phenotypes in IHH men.

METHODS

A retrospective study was conducted (1980-2020) examining olfaction (Kallmann syndrome [KS] vs normosmic IHH [nHH]), baseline testicular volume (absent vs partial puberty), neuroendocrine profiling (pulsatile vs apulsatile luteinizing hormone [LH] secretion), and genetic variants in 62 IHH-associated genes through exome sequencing (ES).

RESULTS

In total, 242 men (KS: n = 131 [54%], nHH: n = 111 [46%]) were included. Men with absent puberty had significantly lower gonadotropin levels (P < .001) and were more likely to have undetectable LH (P < .001). Logistic regression showed partial puberty as a statistically significant predictor of pulsatile LH secretion (R2 = 0.71, P < .001, OR: 10.8; 95% CI, 3.6-38.6). Serum LH of 2.10 IU/L had a 95% true positive rate for predicting LH pulsatility. Genetic analyses in 204 of 242 IHH men with ES data available revealed 36 of 204 (18%) men carried protein-truncating variants (PTVs) in 12 IHH genes. Men with absent puberty and apulsatile LH were enriched for oligogenic PTVs (P < .001), with variants in ANOS1 being the predominant PTV in this genotype-phenotype association. Men with absent puberty were enriched for ANOS1 PTVs compared to partial puberty counterparts (P = .002). PTVs in other IHH genes imparted more variable reproductive phenotypic severity.

CONCLUSION

Partial puberty and LH greater than or equal to 2.10 IU/L are proxies for pulsatile LH secretion. ANOS1 PTVs confer severe reproductive phenotypes. Variable phenotypic severity in the face of severe genetic variants in other IHH genes point to significant neuroendocrine plasticity of the HPG axis in IHH men.

Heterozygous mutations in SOX2 may cause idiopathic hypogonadotropic hypogonadism via dominant-negative mechanisms

Pathogenic SRY-box transcription factor 2 (SOX2) variants typically cause severe ocular defects within a SOX2 disorder spectrum that includes hypogonadotropic hypogonadism. We examined exome-sequencing data from a large, well-phenotyped cohort of patients with idiopathic hypogonadotropic hypogonadism (IHH) for pathogenic SOX2 variants to investigate the underlying pathogenic SOX2 spectrum and its associated phenotypes. We identified 8 IHH individuals harboring heterozygous pathogenic SOX2 variants with variable ocular phenotypes. These variant proteins were tested in vitro to determine whether a causal relationship between IHH and SOX2 exists. We found that Sox2 was highly expressed in the hypothalamus of adult mice and colocalized with kisspeptin 1 (KISS1) expression in the anteroventral periventricular nucleus of adult female mice. In vitro, shRNA suppression of mouse SOX2 protein in Kiss-expressing cell lines increased the levels of human kisspeptin luciferase (hKiss-luc) transcription, while SOX2 overexpression repressed hKiss-luc transcription. Further, 4 of the identified SOX2 variants prevented this SOX2-mediated repression of hKiss-luc. Together, these data suggest that pathogenic SOX2 variants contribute to both anosmic and normosmic forms of IHH, attesting to hypothalamic defects in the SOX2 disorder spectrum. Our study describes potentially novel mechanisms contributing to SOX2-related disease and highlights the necessity of SOX2 screening in IHH genetic evaluation irrespective of associated ocular defects.

The p190 RhoGAPs, ARHGAP35, and ARHGAP5 are implicated in GnRH neuronal development: Evidence from patients with idiopathic hypogonadotropic hypogonadism, zebrafish, and in vitro GAP activity assay

PURPOSE

The study aimed to identify novel genes for idiopathic hypogonadotropic hypogonadism (IHH).

METHODS

A cohort of 1387 probands with IHH underwent exome sequencing and de novo, familial, and cohort-wide investigations. Functional studies were performed on 2 p190 Rho GTPase-activating proteins (p190 RhoGAP), ARHGAP35 and ARHGAP5, which involved in vivo modeling in larval zebrafish and an in vitro p190A-GAP activity assay.

RESULTS

Rare protein-truncating variants (PTVs; n = 5) and missense variants in the RhoGAP domain (n = 7) in ARHGAP35 were identified in IHH cases (rare variant enrichment: PTV [unadjusted P = 3.1E-06] and missense [adjusted P = 4.9E-03] vs controls). Zebrafish modeling using gnrh3:egfp phenotype assessment showed that mutant larvae with deficient arhgap35a, the predominant ARHGAP35 paralog in the zebrafish brain, display decreased GnRH3-GFP+ neuronal area, a readout for IHH. In vitro GAP activity studies showed that 1 rare missense variant [ARHGAP35 p.(Arg1284Trp)] had decreased GAP activity. Rare PTVs (n = 2) also were discovered in ARHGAP5, a paralog of ARHGAP35; however, arhgap5 zebrafish mutants did not display significant GnRH3-GFP+ abnormalities.

CONCLUSION

This study identified ARHGAP35 as a new autosomal dominant genetic driver for IHH and ARHGAP5 as a candidate gene for IHH. These observations suggest a novel role for the p190 RhoGAP proteins in GnRH neuronal development and integrity.

Reversible hypogonadotropic hypogonadism in men with the fertile eunuch/Pasqualini syndrome: A single-center natural history study

Congenital hypogonadotropic hypogonadism (HH) is a heterogeneous genetic disorder characterized by disrupted puberty and infertility. In most cases, HH is abiding yet 10-15% undergo reversal. Men with HH and absent and partial puberty (i.e., testicular volume <4mL and >4mL respectively) have been well-studied, but the rare fertile eunuch (FE) variant remains poorly characterized. This natural history study of 240 men with HH delineates the clinical presentation, neuroendocrine profile, rate of reversal and genetics of the FE variant. We compared three HH groups: FE (n=38), absent puberty (n=139), and partial puberty (n=63). The FE group had no history of micropenis and 2/38 (5%) had cryptorchidism (p<0.0001 vs. other groups). The FE group exhibited higher rates of detectable gonadotropins, higher mean LH/FSH levels, and higher serum inhibin B levels (all p<0.0001). Neuroendocrine profiling showed pulsatile LH secretion in 30/38 (79%) of FE men (p<0.0001) and 16/36 (44%) FE men underwent spontaneous reversal of HH (p<0.001). The FE group was enriched for protein-truncating variants (PTVs) in GNRHR and FGFR1 and 4/30 (13%) exhibited oligogenic PTVs. Findings suggest men with the FE variant exhibit the mildest neuroendocrine defects of HH men and the FE sub-type represents the first identified phenotypic predictor for reversible HH.

LBMON114 Enrichment Of Rare Sequence Variants In Genes That Communicate Metabolic Signals To The GnRH System In Hypothalamic Amenorrhea

Introduction

Functional hypothalamic amenorrhea (HA) is commonly associated with increased exercise or decreased caloric intake and often with stress. We have previously demonstrated an increased burden of rare sequence variants (RSVs) in genes involved in GnRH ontogeny and upstream regulation in women with HA, but the role of metabolic and stress signaling to the GnRH neuronal system is poorly defined in this population.

Methods

The study included 100 women with a confirmed diagnosis of HA. The control cohort consisted of 468 women (aged 45­­-65 years) drawn from the NIH ClinSeq® Project. Exome sequencing was performed on peripheral blood genomic DNA. A subset of 72 genes was analyzed that have been shown to: 1) link metabolic or stress with reproductive phenotypes or 2) integrate metabolic and stress pathways with control of GnRH secretion. Joint genotyping of case and control samples was performed using the GATK GenotypeGVCFs function, locus-filtering using the VariantRecalibrator function, and genotype refinement using CalculateGenotypePosteriors with computation of median depths. Median depth positions <10, positions failing GATK VQSR or GATK genotype quality scores <20 were excluded. RSVs were identified by < 1% frequency in any subpopulation in gnomeAD for all-subjects (AS) and < 1% frequency in non-Finnish Europeans for Caucasians (CS). Data were analyzed for AS and for CS using a one-sided Fisher exact test for metabolism genes and stress genes. An additional regression analysis was conducted on the number of RSVs in a given gene as a predictor of HA vs. control. Comparisons with a p-value of < 0.1 are reported.

Results

HA patients exhibited an increased burden of RSVs in metabolism genes vs. controls (AS p=0. 043; CS p=0.105). The total number of RSVs per gene highlighted differences between HA and controls for the following genes: ADAMTSL1, GRINA, GRIN1, HCRTR1, TENM3, and NOS1 (AS p<0. 001, p=0. 032, p=0. 057, p=0. 082, p=0. 091, p=0. 095; CS p=0. 024, p=0. 044, p=0. 044, p NS, p=0. 086, p NS). Interestingly, RSVs in NOS1 and TENM3 appeared to be protective for HA (odds ratio <1 for both). In contrast, candidate stress genes were not significant in either the AS or CS (p=0.788, p=0.910).

Conclusions

These data suggest that RSVs in genes involved in phenotypes or signaling pathways that link metabolism to GnRH secretion may predispose to development of HA in the setting of decreased energy balance, but not for stress-related genes. GRINA and GRIN1 are important components of glutamate signaling that facilitate both appetite and GnRH secretion either directly or through kisspeptin. HCRTR1 plays a similar role in linking appetite and GnRH secretion while NOS1, which facilitates kisspeptin signaling, may be protective. This work highlights the need for further studies to understand the potential roles of ADAMTSL1 and TENM3 as risk factors for HA.

Presentation: Monday, June 13, 2022 12:30 p.m. - 2:30 p.m.

Kisspeptin Overcomes GnRH Neuronal Suppression Secondary to Hyperprolactinemia in Humans

CONTEXT

Hyperprolactinemia suppresses gonadotropin-releasing hormone (GnRH)-induced luteinizing hormone (LH) pulses. The hypothalamic neuropeptide kisspeptin potently stimulates the secretion of GnRH. The effects of exogenous kisspeptin administration on GnRH pulse generation in the setting of hyperprolactinemia have not previously been explored.

OBJECTIVE

This work aimed to examine the effects of kisspeptin on GnRH secretion, as reflected by LH secretion, in women with hyperprolactinemia.

METHODS

Women with hyperprolactinemia (n = 11) participated in two 12-hour visits. Before study visits, participants underwent washout of dopamine agonist and/or combined oral contraceptive. Frequent blood sampling was performed (1 sample was collected every 10 minutes). Visit 1 involved no intervention, to examine baseline LH pulsatility. During visit 2, kisspeptin 112-121 (0.24 nmol/kg) was administered every 1 hour, for 10 hours. At hour 11, one intravenous bolus of GnRH (75 ng/kg) was administered.

RESULTS

Repetitive intravenous bolus kisspeptin administration increased the total number of LH pulses in the setting of hyperprolactinemia. The interpulse interval declined during the same time frames. LH pulse amplitude did not change, but the mean LH rose. In 6 participants with progesterone levels suggestive of an anovulatory state, mean LH and estradiol levels increased significantly at visit 2. In the entire cohort, follicle-stimulating hormone and prolactin levels did not change significantly across the 2 visits. A total of 73% of subjects exhibited an LH pulse within 30 minutes of first kisspeptin dose.

CONCLUSION

Kisspeptin is capable of stimulating hypothalamic GnRH-induced LH pulses in the setting of hyperprolactinemia.

Review of human genetic and clinical studies directly relevant to GnRH signalling

GnRH is the pivotal hormone in controlling the hypothalamic-pituitary gonadal (HPG) axis in humans and other mammalian species. GnRH function is influenced by a multitude of known and still unknown environmental and genetic factors. Molecular genetic studies on human families with hypogonadotropic hypogonadism over the past two decades have been instrumental in delineating the kisspeptin and neurokinin B signalling, which integrally modulates GnRH release from the hypothalamus. The identification of kisspeptin and neurokinin B ligand-receptor gene pair mutations in patients with absent puberty have paved the way to a greater understanding of the central regulation of the HPG cascade. In this article, we aim to review the literature on the genetic and clinical aspects of GnRH and its receptor, as well as the two ligand-receptor sets directly pertinent to the function of GnRH hormone signalling, kisspeptin/ kisspeptin receptor and NKB/NK3R.

Kisspeptin deficiency leads to abnormal adrenal glands and excess steroid hormone secretion

Knockout mice for the kisspeptin receptor, Kiss1r (Kiss1r-/-) and its ligand kisspeptin, Kiss1 (Kiss1-/-) replicate the phenotype of isolated hypogonadotropic hypogonadism (IHH) associated with variants of these genes in humans. A recent report suggests that kisspeptin may be involved in human fetal adrenocortical development and function. Herein, we characterized the adrenal function and morphology in Kiss1-/- mice that do not go through normal puberty. Two fetal markers were expressed in eosinophilic cells potentially derived from the X-zone that should disappear at puberty in male mice and during the first pregnancy in female animals. Although the hypercorticosteronism observed in Kiss1-/- females corrected overtime, hyperaldosteronism persisted at 14 months and correlated with the overexpression of Star. To determine if KISS1 and KISS1R genes are involved in the development of primary aldosteronism (PA) and hypercortisolism [Cushing's syndrome (CS)] in humans, we sequenced these 2 genes in 65 patients with PA and/or CS. Interestingly, a patient with CS presented with a germline KISS1 variant (p.H90D, rs201073751). We also found three rare variants in the KISS1R gene in three patients with PA: p.C95W (rs141767649), p.A189T (rs73507527) and p.R229R (rs115335009). The two missense variants have been previously associated with IHH. Our findings suggest that KISS1 may play a role in adrenal function in mice and possibly adrenocortical steroid hormone secretion in humans, beyond its recently described role in human fetal adrenocortical development.

Safety Evaluation of KP-10 (Metastin 45-54) Following once Daily Intravenous Administration for 14 Days in Dog

Kisspeptin-10 (previously referred as metastin 45-54), an active fragment of the endogenous full-length kisspeptin-145, is a potential therapeutic agent for reproductive disorders such as infertility, amenorrhea, and pubertal delay. A safety evaluation of KP-10 was conducted in dogs at the doses of 30, 100, and 1,000 μg/kg, given once daily intravenously for 14 days with a 14-day recovery period. There were no overt signs of drug-related toxicity observed in clinical signs, body weights, food consumption, clinical pathology, histopathology, urinalysis, electrocardiogram, or respiratory rate. Due to very rapid clearance of the peptide, luteinizing hormone (LH) levels were measured as a surrogate marker to demonstrate KP-10 exposure. The LH response reached a maximum concentration at 5 minutes post-dose and remained relatively unchanged for at least 30 minutes after dosing with no gender effect. LH concentrations on Day 1 were generally greater than on day 14. Vaginal cytology results indicated all dogs were in anestrous throughout the dosing period. There were also no KP-10-related findings observed in recovery animals on Day 29. In conclusion, KP-10 demonstrated favorable safety profile in dog where 1,000 μg/kg dose was considered as a no-observed-adverse-effect level dose when administered IV once daily for 14 days.

Phenotypic continuum between Waardenburg syndrome and idiopathic hypogonadotropic hypogonadism in humans with SOX10 variants

PURPOSE

SOX10 variants previously implicated in Waardenburg syndrome (WS) have now been linked to Kallmann syndrome (KS), the anosmic form of idiopathic hypogonadotropic hypogonadism (IHH). We investigated whether SOX10-associated WS and IHH represent elements of a phenotypic continuum within a unifying disorder or if they represent phenotypically distinct allelic disorders.

METHODS

Exome sequencing from 1,309 IHH subjects (KS: 632; normosmic idiopathic hypogonadotropic hypogonadism [nIIHH]: 677) were reviewed for SOX10 rare sequence variants (RSVs). The genotypic and phenotypic spectrum of SOX10-related IHH (this study and literature) and SOX10-related WS cases (literature) were reviewed and compared with SOX10-RSV spectrum in gnomAD population.

RESULTS

Thirty-seven SOX10-associated IHH cases were identified as follows: current study: 16 KS; 4 nIHH; literature: 16 KS; 1 nIHH. Twenty-three IHH cases (62%; all KS), had ≥1 known WS-associated feature(s). Moreover, five previously reported SOX10-associated WS cases showed IHH-related features. Four SOX10 missense RSVs showed allelic overlap between IHH-ascertained and WS-ascertained cases. The SOX10-HMG domain showed an enrichment of RSVs in disease states versus gnomAD.

CONCLUSION

SOX10 variants contribute to both anosmic (KS) and normosmic (nIHH) forms of IHH. IHH and WS represent SOX10-associated developmental defects that lie along a unifying phenotypic continuum. The SOX10-HMG domain is critical for the pathogenesis of SOX10-related human disorders.

Increased Burden of Rare Sequence Variants in GnRH-Associated Genes in Women With Hypothalamic Amenorrhea

CONTEXT

Functional hypothalamic amenorrhea (HA) is a common, acquired form of hypogonadotropic hypogonadism that occurs in the setting of energy deficits and/or stress. Variability in individual susceptibility to these stressors, HA heritability, and previous identification of several rare sequence variants (RSVs) in genes associated with the rare disorder, isolated hypogonadotropic hypogonadism (IHH), in individuals with HA suggest a possible genetic contribution to HA susceptibility.

OBJECTIVE

We sought to determine whether the burden of RSVs in IHH-related genes is greater in women with HA than controls.

DESIGN

We compared patients with HA to control women.

SETTING

The study was conducted at secondary referral centers.

PATIENTS AND OTHER PARTICIPANTS

Women with HA (n = 106) and control women (ClinSeq study; n = 468).

INTERVENTIONS

We performed exome sequencing in all patients and controls.

MAIN OUTCOME MEASURE(S)

The frequency of RSVs in 53 IHH-associated genes was determined using rare variant burden and association tests.

RESULTS

RSVs were overrepresented in women with HA compared with controls (P = .007). Seventy-eight heterozygous RSVs in 33 genes were identified in 58 women with HA (36.8% of alleles) compared to 255 RSVs in 41 genes among 200 control women (27.2%).

CONCLUSIONS

Women with HA are enriched for RSVs in genes that cause IHH, suggesting that variation in genes associated with gonadotropin-releasing hormone neuronal ontogeny and function may be a major determinant of individual susceptibility to developing HA in the face of diet, exercise, and/or stress.

Tachykinin Signaling Is Required for Induction of the Preovulatory Luteinizing Hormone Surge and Normal Luteinizing Hormone Pulses

Tachykinins (neurokinin A [NKA], neurokinin B [NKB], and substance P [SP]) are important components of the neuroendocrine control of reproduction by direct stimulation of Kiss1 neurons to control GnRH pulsatility, which is essential for reproduction. Despite this role of tachykinins in successful reproduction, knockout (KO) mice for Tac1 (NKA/SP) and Tac2 (NKB) genes are fertile, resembling the phenotype of human patients bearing NKB signaling mutations, who often reverse their hypogonadal phenotype. This suggests the existence of compensatory mechanisms among the different tachykinin ligand-receptor systems to maintain reproduction in the absence of one of them. In order to test this hypothesis, we generated complete tachykinin-deficient mice (Tac1/Tac2KO). Male mice displayed delayed puberty onset and decreased luteinizing hormone (LH) pulsatility (frequency and amplitude of LH pulses) but preserved fertility. However, females did not show signs of puberty onset (first estrus) within 45 days after vaginal opening, they displayed a low frequency (but normal amplitude) of LH pulses, and 80% of them remained infertile. Further evaluation identified a complete absence of the preovulatory LH surge in Tac1/Tac2KO females as well as in wild-type females treated with NKB or SP receptor antagonists. These data confirmed a fundamental role of tachykinins in the timing of puberty onset and LH pulsatility and uncovered a role of tachykinin signaling in facilitation of the preovulatory LH surge. Overall, these findings indicate that tachykinin signaling plays a dominant role in the control of ovulation, with potential implications as a pathogenic mechanism and a therapeutic target to improve reproductive outcomes in women with ovulation impairments.

Evaluating co-created patient-facing materials to increase understanding of genetic test results

Patients often have difficulty understanding genetic test reports. Technical language and jargon can impede comprehension and limit patients using results to act on findings. One potential way to improve patient understanding of genetic test reports is to provide patient-facing materials. This study aimed to examine understandability and actionability of co-created patient-facing materials for genetic test results in a research context. We combined interprofessional perspectives and patient engagement to co-create patient-facing materials for patients undergoing research genetic testing for congenital hypogonadotropic hypogonadism (Kallmann syndrome). The iterative development process was guided by principles of health literacy and human-centered design (i.e., design thinking). Readability was assessed using eight validated algorithms. Patients and parents evaluated materials using a web-based survey. The gold standard Patient Education Materials Assessment Tool for print materials (PEMAT-P) was employed to measure understandability (content, style, use of numbers, organization, design, use of visual aids) and actionability. PEMAT-P scores >80% were considered high quality. Results were analyzed descriptively and correlations performed to identify relationships between education/health literacy and PEMAT-P ratings. A consensus score of eight algorithms indicated the materials were an 8^th -9th grade reading level. Our findings are consistent with the U.S. Department of Health and Human Services 'average difficulty' classification (i.e., 7th-9th grade). In total, 61 patients/parents evaluated the materials. 'Visual Aids' received the lowest mean PEMAT-P rating (89%). All other parameters scored 90%-97%. PEMAT-P scores did not differ according to educational attainment (less than college vs. college or more, p = 0.28). Participants with adequate health literacy were more likely to approve of the 'organization' of information (p < 0.05). Respondents with low health literacy had more favorable views of 'visual aids' (p < 0.01). Involving patients in a co-creation process can produce high-quality patient-facing materials that are easier to understand.

Using Kisspeptin to Predict Pubertal Outcomes for Youth With Pubertal Delay

CONTEXT

The management of youth with delayed puberty is hampered by difficulty in predicting who will eventually progress through puberty and who will fail to attain adult reproductive endocrine function. The neuropeptide kisspeptin, which stimulates gonadotropin-releasing hormone (GnRH) release, can be used to probe the integrity of the reproductive endocrine axis.

OBJECTIVE

We sought to determine whether responses to kisspeptin can predict outcomes for individuals with pubertal delay.

DESIGN, SETTING, AND PARTICIPANTS

We conducted a longitudinal cohort study in an academic medical center of 16 children (3 girls and 13 boys) with delayed or stalled puberty.

INTERVENTION AND OUTCOME MEASURES

Children who had undergone kisspeptin- and GnRH-stimulation tests were followed every 6 months for clinical evidence of progression through puberty. Inhibin B was measured in boys. A subset of participants underwent exome sequencing.

RESULTS

All participants who had responded to kisspeptin with a rise in luteinizing hormone (LH) of 0.8 mIU/mL or greater subsequently progressed through puberty (n = 8). In contrast, all participants who had exhibited LH responses to kisspeptin ≤ 0.4 mIU/mL reached age 18 years without developing physical signs of puberty (n = 8). Thus, responses to kisspeptin accurately predicted later pubertal outcomes (P = .0002). Moreover, the kisspeptin-stimulation test outperformed GnRH-stimulated LH, inhibin B, and genetic testing in predicting pubertal outcomes.

CONCLUSION

The kisspeptin-stimulation can assess future reproductive endocrine potential in prepubertal children and is a promising novel tool for predicting pubertal outcomes for children with delayed puberty.

Hypogonadotropic hypogonadism due to variants in RAB3GAP2: expanding the phenotypic and genotypic spectrum of Martsolf syndrome

Biallelic pathogenic variants in RAB3GAP2 cause Warburg Micro syndrome (WARBM) and Martsolf syndrome (MS), two rare, phenotypically overlapping disorders characterized by congenital cataracts, intellectual disability, and hypogonadism. Although the initial report documented hypergonadotropic hypogonadism (implying a gonadal defect), an adolescent girl with WARBM/MS was subsequently reported to have hypogonadotropic hypogonadism (implying a central defect in either the hypothalamus or anterior pituitary). However, in adult MS, hypogonadotropism has not been convincingly demonstrated. Additionally, the correlation between the pathogenic severity of variants in RAB3GAP2 and the phenotypic severity also remains unclear. Here we present a clinical report of a woman with congenital cataracts, apparent intellectual disability, and pubertal failure who underwent exome sequencing (ES) to determine a precise molecular diagnosis. Reproductive phenotypes reported previously in individuals with MS and the genotypic spectrum of previous RAB3GAP2 variants were also reviewed. The ES identified pathogenic compound heterozygous RAB3GAP2 variants (c.387-2A > G; p.(Arg428Glu)) combined with her phenotypic features, which enabled a unifying molecular diagnosis of MS. Reproductive evaluation confirmed a normosmic idiopathic hypogonadotropic hypogonadism. Review of the RAB3GAP2 allelic spectrum in WARBM/MS suggests that although variants resulting in complete abrogation of RAB3GAP2 protein function cause severe WARBM, variants associated with partially preserved RAB3GAP2 function cause milder MS. This report expands the genotypic and phenotypic spectrum of MS and demonstrates hypogonadotropic hypogonadism as a key pathophysiologic abnormality in MS. Genotype-phenotype associations of previously reported RAB3GAP2 variants indicate that variants that fully abolish RAB3GAP2 function result in WARBM, whereas MS is associated with variants of lesser severity with residual RAB3GAP2 function.

Insight Into the Ontogeny of GnRH Neurons From Patients Born Without a Nose

CONTEXT

The reproductive axis is controlled by a network of gonadotropin-releasing hormone (GnRH) neurons born in the primitive nose that migrate to the hypothalamus alongside axons of the olfactory system. The observation that congenital anosmia (inability to smell) is often associated with GnRH deficiency in humans led to the prevailing view that GnRH neurons depend on olfactory structures to reach the brain, but this hypothesis has not been confirmed.

OBJECTIVE

The objective of this work is to determine the potential for normal reproductive function in the setting of completely absent internal and external olfactory structures.

METHODS

We conducted comprehensive phenotyping studies in 11 patients with congenital arhinia. These studies were augmented by review of medical records and study questionnaires in another 40 international patients.

RESULTS

All male patients demonstrated clinical and/or biochemical signs of GnRH deficiency, and the 5 men studied in person had no luteinizing hormone (LH) pulses, suggesting absent GnRH activity. The 6 women studied in person also had apulsatile LH profiles, yet 3 had spontaneous breast development and 2 women (studied from afar) had normal breast development and menstrual cycles, suggesting a fully intact reproductive axis. Administration of pulsatile GnRH to 2 GnRH-deficient patients revealed normal pituitary responsiveness but gonadal failure in the male patient.

CONCLUSIONS

Patients with arhinia teach us that the GnRH neuron, a key gatekeeper of the reproductive axis, is associated with but may not depend on olfactory structures for normal migration and function, and more broadly, illustrate the power of extreme human phenotypes in answering fundamental questions about human embryology.

DLG2 variants in patients with pubertal disorders

PURPOSE

Impaired function of gonadotropin-releasing hormone (GnRH) neurons can cause a phenotypic spectrum ranging from delayed puberty to isolated hypogonadotropic hypogonadism (IHH). We sought to identify a new genetic etiology for these conditions.

METHODS

Exome sequencing was performed in an extended family with autosomal dominant, markedly delayed puberty. The effects of the variant were studied in a GnRH neuronal cell line. Variants in the same gene were sought in a large cohort of individuals with IHH.

RESULTS

We identified a rare missense variant (F900V) in DLG2 (which encodes PSD-93) that cosegregated with the delayed puberty. The variant decreased GnRH expression in vitro. PSD-93 is an anchoring protein of NMDA receptors, a type of glutamate receptor that has been implicated in the control of puberty in laboratory animals. The F900V variant impaired the interaction between PSD-93 and a known binding partner, Fyn, which phosphorylates NMDA receptors. Variants in DLG2 that also decreased GnRH expression were identified in three unrelated families with IHH.

CONCLUSION

The findings indicate that variants in DLG2/PSD-93 cause autosomal dominant delayed puberty and may also contribute to IHH. The findings also suggest that the pathogenesis involves impaired NMDA receptor signaling and consequently decreased GnRH secretion.

Role of Kisspeptin and NKB in Puberty in Nonhuman Primates: Sex Differences

To understand the roles of kisspeptin and neurokinin B (NKB) in puberty and sex differences in their involvement, we conducted a series of experiments measuring the release of gonadotropin-releasing hormone (GnRH) and kisspeptin in the median eminence of the hypothalamus in male and female monkeys throughout sexual development. Results indicate that kisspeptin-10 and the NKB agonist, senktide, stimulated GnRH release in males and females at the prepubertal and pubertal stages, but females are much more sensitive to kisspeptin signaling than males. Moreover, throughout the progress of puberty, major remodeling of kisspeptin and NKB signaling pathways for the regulation of GnRH release takes place. In females during puberty, reciprocal pathways (i.e., kisspeptin signaling mediated through NKB neurons and NKB signaling mediated through kisspeptin neurons) are established, to provide powerful and flexible mechanisms for GnRH neurosecretory activity necessary for complex female reproductive function in adulthood. By contrast, during puberty in males, reciprocal pathways are consolidated to a simpler kisspeptin-dominant signaling pathway. Nevertheless, in primates, both kisspeptin and NKB signaling are contributing factors for the pubertal increase in GnRH release, rather than initiating puberty.

Functional Hypogonadotropic Hypogonadism in Men: Underlying Neuroendocrine Mechanisms and Natural History

CONTEXT

After completion of puberty a subset of men experience functional hypogonadotropic hypogonadism (FHH) secondary to excessive exercise or weight loss. This phenomenon is akin to hypothalamic amenorrhea (HA) in women, yet little is known about FHH in men.

OBJECTIVE

To investigate the neuroendocrine mechanisms, genetics, and natural history underlying FHH.

DESIGN

Retrospective study in an academic medical center.

PARTICIPANTS

Healthy postpubertal men presenting with symptoms of hypogonadism in the setting of excessive exercise (>10 hours/week) or weight loss (>10% of body weight). Healthy age-matched men served as controls.

INTERVENTIONS

Clinical assessment, biochemical and neuroendocrine profiling, body composition, semen analysis, and genetic evaluation of genes known to cause isolated GnRH deficiency.

MAIN OUTCOME MEASURES

Reproductive hormone levels, endogenous GnRH-induced LH pulse patterns, and rare genetic variants.

RESULTS

Ten men with FHH were compared with 18 age-matched controls. Patients had significantly lower body mass index, testosterone, LH, and mean LH pulse amplitudes yet normal LH pulse frequency, serum FSH, and sperm counts. Some patients exhibited nocturnal, sleep-entrained LH pulses characteristic of early puberty, and one FHH subject showed a completely apulsatile LH secretion. After decreased exercise and weight gain, five men with men had normalized serum testosterone levels, and symptoms resolved. Rare missense variants in NSMF (n = 1) and CHD7 (n = 1) were identified in two men with FHH.

CONCLUSIONS

FHH is a rare, reversible form of male GnRH deficiency. LH pulse patterns in male FHH are similar to those observed in women with HA. This study expands the spectrum of GnRH deficiency disorders in men.

Different Cerebellar Ataxia Phenotypes Associated with Mutations of the PNPLA6 Gene in Brazilian Patients with Recessive Ataxias

Autosomal recessive cerebellar ataxias (ARCAs) represent a heterogeneous group of inherited disorders. The association of early-onset cerebellar ataxia with hypogonadotropic hypogonadism is related to two syndromes, known as Gordon Holmes syndrome (GHS-ataxia and pyramidal signs with hypogonadotropic hypogonadism) and Boucher-Neuhäuser syndrome (BNS-ataxia with chorioretinal dystrophy). Mutations in the PNPLA6 gene have been identified as the cause of hereditary spastic paraplegia and complex forms of ataxia associated with retinal and endocrine manifestations. We reported two Brazilian patients with sporadic, progressive cerebellar ataxia, associated with hypogonadotropic hypogonadism, in whom the GHS and BNS were confirmed by the demonstration of compound heterozygote mutations in the PNPLA6 gene. Genetic analysis of the patient 1 revealed compound heterozygous mutations, one allele in exon 34 and the other allele in exon 29. Genetic exam of the patient 2 also demonstrated compound heterozygous mutations. Three were novel mutations. The missense mutation c.3373G> A, found in the BNS patient, was previously related to Oliver-McFarlane syndrome. These different mutations in this gene suggest a complex phenotype associated disease spectrum.

Paediatric and adult-onset male hypogonadism

The hypothalamic-pituitary-gonadal axis is of relevance in many processes related to the development, maturation and ageing of the male. Through this axis, a cascade of coordinated activities is carried out leading to sustained testicular endocrine function, with gonadal testosterone production, as well as exocrine function, with spermatogenesis. Conditions impairing the hypothalamic-pituitary-gonadal axis during paediatric or pubertal life may result in delayed puberty. Late-onset hypogonadism is a clinical condition in the ageing male combining low concentrations of circulating testosterone and specific symptoms associated with impaired hormone production. Testosterone therapy for congenital forms of hypogonadism must be lifelong, whereas testosterone treatment of late-onset hypogonadism remains a matter of debate because of unclear indications for replacement, uncertain efficacy and potential risks. This Primer focuses on a reappraisal of the physiological role of testosterone, with emphasis on the critical interpretation of the hypogonadal conditions throughout the lifespan of the male individual, with the exception of hypogonadal states resulting from congenital disorders of sex development.

Role of Kisspeptin and Neurokinin B Signaling in Male Rhesus Monkey Puberty

Despite the well-established concept that an increase in pulsatile GnRH release triggers puberty, the precise signaling mechanism responsible for the pubertal increase in GnRH release remains unclear. A recent study indicates that developmental changes in the network formation between kisspeptin and neurokinin B (NKB) signaling greatly contribute to the pubertal increase in GnRH release in female monkeys. It is, however, unknown whether similar developmental changes in the kisspeptin and NKB network are involved in male puberty. In the current study, we first characterized the pubertal stages in male rhesus monkeys by assessing physiological and hormonal changes during sexual development. Subsequently, we examined the role of the kisspeptin and NKB signaling network in the pubertal increase in GnRH release. Results suggest that while collaborative kisspeptin and NKB signaling to GnRH neurons was active before puberty onset, after initiation of puberty the role of NKB signaling in GnRH neurons diminished and kisspeptin signaling assumed the primary stimulatory role in the regulation of GnRH release in male monkeys. These findings in males differ from those seen in females.

Divergent responses to kisspeptin in children with delayed puberty

BACKGROUND

The neuropeptide kisspeptin stimulates luteinizing hormone (LH) secretion in healthy adults but not in adults with idiopathic hypogonadotropic hypogonadism. We hypothesized that, in children presenting with delayed or stalled puberty, kisspeptin would elicit LH secretion in those children found on detailed nighttime neuroendocrine profiling to have evidence of emerging reproductive endocrine function.

METHODS

Eleven boys and four girls were admitted overnight to assess LH secretion at baseline, after a single intravenous bolus of kisspeptin, and after a single intravenous bolus of gonadotropin-releasing hormone (GnRH). Subjects then received exogenous pulsatile GnRH for 6 days and returned for a second visit to measure responses to kisspeptin and GnRH after this pituitary "priming." Responses to kisspeptin and GnRH were also measured in 5 healthy men.

RESULTS

Of the 15 children with delayed/stalled puberty, 6 exhibited at least one spontaneous LH pulse overnight; all of these subjects had clear responses to kisspeptin, as did one additional subject. Seven subjects had no response to kisspeptin, and one subject exhibited an intermediate response. In the children who responded to kisspeptin, the responses had features comparable to those of adult men.

CONCLUSION

In this first report of kisspeptin administration to pediatric subjects to our knowledge, children with delayed/stalled puberty showed a wide range of responses, with some showing a robust response and others showing little to no response. Further follow-up will determine whether responses to kisspeptin predict future pubertal entry for children with delayed puberty.

TRIAL REGISTRATION

ClinicalTrials.gov NCT01438034 and NCT01952782.

FUNDING

NIH Eunice Kennedy Shriver National Institute of Child Health and Human Development (R01 HD043341, R01 HD090071, P50 HD028138), NIH National Center for Advancing Translational (UL1 TR001102), NIH National Institute of Diabetes and Digestive and Kidney Diseases (T32 DK007028), the Massachusetts General Hospital Executive Committee on Research Fund for Medical Discovery, Harvard Catalyst, Doris Duke Charitable Foundation (award 2013110), Charles H. Hood Foundation, Robert and Laura Reynolds MGH Research Scholar Program, and Harvard University. These funding sources had no role in the design of this study and did not have any role in conducting the study, analyses, interpretation of the data, or the decision to submit results.

Role of Kisspeptin and Neurokinin B in Puberty in Female Non-Human Primates

In human patients, loss-of-function mutations in the genes encoding kisspeptin (KISS1) and neurokinin B (NKB) and their receptors (KISS1R and NK3R, respectively) result in an abnormal timing of puberty or the absence of puberty. To understand the neuroendocrine mechanism of puberty, we investigated the contribution of kisspeptin and NKB signaling to the pubertal increase in GnRH release using rhesus monkeys as a model. Direct measurements of GnRH and kisspeptin in the median eminence of the hypothalamus with infusion of agonists and antagonists for kisspeptin and NKB reveal that kisspeptin and NKB signaling stimulate GnRH release independently or collaboratively by forming kisspeptin and NKB neuronal networks depending on the developmental age. For example, while in prepubertal females, kisspeptin and NKB signaling independently stimulate GnRH release, in pubertal females, the formation of a collaborative kisspeptin and NKB network further accelerates the pubertal increase in GnRH release. It is speculated that the collaborative mechanism between kisspeptin and NKB signaling to GnRH neurons is necessary for the complex reproductive function in females.

Kisspeptin and Neurokinin B Signaling Network Underlies the Pubertal Increase in GnRH Release in Female Rhesus Monkeys

Loss-of-function or inactivating mutations in the genes coding for kisspeptin and its receptor (KISS1R) or neurokinin B (NKB) and the NKB receptor (NK3R) in humans result in a delay in or the absence of puberty. However, precise mechanisms of kisspeptin and NKB signaling in the regulation of the pubertal increase in gonadotropin-releasing hormone (GnRH) release in primates are unknown. In this study, we conducted a series of experiments infusing agonists and antagonists of kisspeptin and NKB into the stalk-median eminence, where GnRH, kisspeptin, and NKB neuroterminal fibers are concentrated, and measuring GnRH release in prepubertal and pubertal female rhesus monkeys. Results indicate that (1) similar to those previously reported for GnRH stimulation by the KISS1R agonist (i.e., human kisspeptin-10), the NK3R agonist senktide stimulated GnRH release in a dose-responsive manner in both prepubertal and pubertal monkeys; (2) the senktide-induced GnRH release was blocked in the presence of the KISS1R antagonist peptide 234 in pubertal but not prepubertal monkeys; and (3) the kisspeptin-induced GnRH release was blocked in the presence of the NK3R antagonist SB222200 in the pubertal but not prepubertal monkeys. These results are interpreted to mean that although, in prepubertal female monkeys, kisspeptin and NKB signaling to GnRH release is independent, in pubertal female monkeys, a reciprocal signaling mechanism between kisspeptin and NKB neurons is established. We speculate that this cooperative mechanism by the kisspeptin and NKB network underlies the pubertal increase in GnRH release in female monkeys.

Continuous Kisspeptin Administration in Postmenopausal Women: Impact of Estradiol on Luteinizing Hormone Secretion

CONTEXT

Kisspeptin stimulates the reproductive endocrine cascade in both men and women. Circulating sex steroids are thought to modulate the ability of kisspeptin to stimulate gonadotropin-releasing hormone (GnRH)-induced luteinizing hormone (LH) release.

OBJECTIVE

To probe the effects of sex steroids on kisspeptin-stimulated GnRH-induced LH pulses.

PARTICIPANTS

Eight healthy postmenopausal women.

INTERVENTION

Subjects underwent every-10-minute blood sampling to measure GnRH-induced LH secretion at baseline and in response to a continuous kisspeptin infusion (12.5 µg/kg/h) over 24 hours. A subset of the participants also received kisspeptin (0.313 µg/kg) and GnRH (75 ng/kg) intravenous boluses.

RESULTS

Postmenopausal women are resistant to the stimulatory effect of continuous kisspeptin on LH secretion. Postmenopausal women receiving estradiol replacement therapy are also resistant to kisspeptin initially, but they demonstrate a significant increase in LH pulse amplitude in direct proportion to the circulating estradiol concentration and duration of kisspeptin administration.

CONCLUSIONS

Kisspeptin administration has complex effects on GnRH, and by extension, on LH secretion. The ability of kisspeptin to affect LH secretion can be modulated by the ambient sex-steroid milieu in a time- and dose-dependent manner.

SMCHD1 mutations associated with a rare muscular dystrophy can also cause isolated arhinia and Bosma arhinia microphthalmia syndrome

Arhinia, or absence of the nose, is a rare malformation of unknown etiology that is often accompanied by ocular and reproductive defects. Sequencing of 40 people with arhinia revealed that 84% of probands harbor a missense mutation localized to a constrained region of SMCHD1 encompassing the ATPase domain. SMCHD1 mutations cause facioscapulohumeral muscular dystrophy type 2 (FSHD2) via a trans-acting loss-of-function epigenetic mechanism. We discovered shared mutations and comparable DNA hypomethylation patterning between these distinct disorders. CRISPR/Cas9-mediated alteration of smchd1 in zebrafish yielded arhinia-relevant phenotypes. Transcriptome and protein analyses in arhinia probands and controls showed no differences in SMCHD1 mRNA or protein abundance but revealed regulatory changes in genes and pathways associated with craniofacial patterning. Mutations in SMCHD1 thus contribute to distinct phenotypic spectra, from craniofacial malformation and reproductive disorders to muscular dystrophy, which we speculate to be consistent with oligogenic mechanisms resulting in pleiotropic outcomes.

Phenotypic spectrum of POLR3B mutations: isolated hypogonadotropic hypogonadism without neurological or dental anomalies

BACKGROUND

A constellation of neurodegenerative disorders exists (Gordon Holmes syndrome, 4H leucodystrophy, Boucher-Neuhauser syndrome) in which patients suffer from both neurological disease (typically manifested by ataxia) and reproductive failure (idiopathic hypogonadotropic hypogonadism (IHH)). POLR3B, which encodes the second largest subunit of RNA polymerase III (pol III), and POLR3A, which forms the pol III catalytic centre, are associated with 4H leucodystrophy.

METHODS

Whole exome sequencing was performed on a large cohort of subjects with IHH (n=565). Detailed neuroendocrine studies were performed in some individuals within this cohort.

RESULTS

Four individuals (two of them siblings) were identified with two rare nucleotide variants in POLR3B. On initial evaluation, all subjects were free of neurological disease. One patient underwent treatment with exogenous pulsatile gonadotropin-releasing hormone for 8 weeks which failed to result in normalisation of his sex steroid milieu due to pituitary resistance.

CONCLUSIONS

These findings suggest that the spectrum of phenotypes resulting from POLR3B mutations is wider than previously believed and that POLR3B can be associated exclusively with disorders characterised by abnormal gonadotropin secretion.

Kisspeptin Responsiveness Signals Emergence of Reproductive Endocrine Activity: Implications for Human Puberty

CONTEXT

Some patients with idiopathic hypogonadotropic hypogonadism (IHH) undergo spontaneous activation of their hypothalamic-pituitary-gonadal axis resulting in normalization of steroidogenesis and/or gametogenesis, a phenomenon termed reversal.

OBJECTIVE

To assess the responsiveness of the GnRH neuronal network to exogenous kisspeptin administration in IHH patients who have undergone reversal.

PARTICIPANTS

Six men with congenital IHH and evidence for reversal.

INTERVENTION

Subjects underwent q10 min blood sampling to measure GnRH-induced LH secretion at baseline and in response to iv boluses of kisspeptin (0.24-2.4 nmol/kg) and GnRH (75 ng/kg).

RESULTS

Individuals with sustained reversal of their hypogonadotropism (spontaneous LH pulses) responded to exogenous kisspeptin with a GnRH-induced LH pulse. Individuals who had reversal but then subsequently suffered relapse of their IHH (loss of spontaneous LH pulsatility) did not respond to kisspeptin.

CONCLUSIONS

The ability of kisspeptin to stimulate a GnRH-induced LH pulse correlates with the presence of endogenous LH pulses. These data suggest that reversal of hypogonadotropism, and by extension sexual maturation, may be due to the acquisition of kisspeptin responsiveness.

Neurokinin B is critical for normal timing of sexual maturation but dispensable for adult reproductive function in female mice

Humans carrying mutations in neurokinin B (NKB) or the NKB receptor fail to undergo puberty due to decreased secretion of GnRH. Despite this pubertal delay, many of these patients go on to achieve activation of their hypothalamic-pituitary-gonadal axis in adulthood, a phenomenon termed reversal, indicating that NKB signaling may play a more critical role for the timing of pubertal development than adult reproductive function. NKB receptor-deficient mice are hypogonadotropic but have no defects in the timing of sexual maturation. The current study has performed the first phenotypic evaluation of mice bearing mutations in Tac2, the gene encoding the NKB ligand, to determine whether they have impaired sexual development similar to their human counterparts. Male Tac2-/- mice showed no difference in the timing of sexual maturation or fertility compared with wild-type littermates and were fertile. In contrast, Tac2-/- females had profound delays in sexual maturation, with time to vaginal opening and first estrus occurring significantly later than controls, and initial abnormalities in estrous cycles. However, cycling recovered in adulthood and Tac2-/- females were fertile, although they produced fewer pups per litter. Thus, female Tac2-/- mice parallel humans harboring NKB pathway mutations, with delayed sexual maturation and activation of the reproductive cascade later in life. Moreover, direct comparison of NKB ligand and receptor-deficient females confirmed that only NKB ligand-deficient animals have delayed sexual maturation, suggesting that in the absence of the NKB receptor, NKB may regulate the timing of sexual maturation through other tachykinin receptors.

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

CONTEXT

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

OBJECTIVE

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

SUBJECTS AND OUTCOME MEASURES

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

RESULTS

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

CONCLUSIONS

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

The integrated hypothalamic tachykinin-kisspeptin system as a central coordinator for reproduction

Tachykinins are comprised of the family of related peptides, substance P (SP), neurokinin A (NKA), and neurokinin B (NKB). NKB has emerged as regulator of kisspeptin release in the arcuate nucleus (ARC), whereas the roles of SP and NKA in reproduction remain unknown. This work explores the roles of SP and NKA in the central regulation of GnRH release. First, central infusion of specific agonists for the receptors of SP (neurokinin receptor 1, NK1R), NKA (NK2R) and NKB (NK3R) each induced gonadotropin release in adult male and ovariectomized, estradiol-replaced female mice, which was absent in Kiss1r(-/-) mice, indicating a kisspeptin-dependent action. The NK2R agonist, however, decreased LH release in ovariectomized-sham replaced females, as documented for NK3R agonists but in contrast to the NK1R agonist, which further increased LH release. Second, Tac1 (encoding SP and NKA) expression in the ARC and ventromedial nucleus was inhibited by circulating estradiol but did not colocalize with Kiss1 mRNA. Third, about half of isolated ARC Kiss1 neurons expressed Tacr1 (NK1R) and 100% Tacr3 (NK3R); for anteroventral-periventricular Kiss1 neurons and GnRH neurons, approximately one-fourth expressed Tacr1 and one-tenth Tacr3; Tacr2 (NK2R) expression was absent in all cases. Overall, these results identify a potent regulation of gonadotropin release by the SP/NK1R and NKA/NK2R systems in the presence of kisspeptin-Kiss1r signaling, indicating that they may, along with NKB/NK3R, control GnRH release, at least in part through actions on Kiss1 neurons.

Exogenous kisspeptin administration as a probe of GnRH neuronal function in patients with idiopathic hypogonadotropic hypogonadism

CONTEXT

Idiopathic hypogonadotropic hypogonadism (IHH) results from defective synthesis, secretion, or action of GnRH. Kisspeptin is a potent stimulus for GnRH secretion.

OBJECTIVE

We probed the functional capacity of the GnRH neuronal network in patients with IHH.

PARTICIPANTS

Eleven subjects with congenital IHH (9 men and 2 women) and one male subject who underwent reversal of IHH were studied. Six of the twelve subjects had an identified genetic cause of their IHH: KAL1 (n = 1), FGFR1 (n = 3), PROKR2 (n = 1), GNRHR (n = 1).

INTERVENTION

Subjects underwent q10 min blood sampling to measure GnRH-induced LH secretion at baseline and in response to intravenous boluses of kisspeptin (0.24 nmol/kg) and GnRH (75 ng/kg) both pre- and post-six days of treatment with exogenous GnRH (25 ng/kg sc every 2 h).

RESULTS

All subjects with abiding IHH failed to demonstrate a GnRH-induced LH response to exogenous kisspeptin. In contrast, the subject who achieved reversal of his hypogonadotropism demonstrated a robust response to kisspeptin.

CONCLUSIONS

The functional capacity of the GnRH neuronal network in IHH patients is impaired, as evidenced by their inability to respond to the same dose of kisspeptin that effects a robust GnRH-induced LH response in healthy men and luteal-phase women. This impairment is observed across a range of genotypes, suggesting that it reflects a fundamental property of GnRH neuronal networks that have not been properly engaged during pubertal development. In contrast, a patient who had experienced reversal of his hypogonadotropism responded to exogenous kisspeptin.

Implantation failure in female Kiss1-/- mice is independent of their hypogonadic state and can be partially rescued by leukemia inhibitory factor

The hypothalamic kisspeptin signaling system is a major positive regulator of the reproductive neuroendocrine axis, and loss of Kiss1 in the mouse results in infertility, a condition generally attributed to its hypogonadotropic hypogonadism. We demonstrate that in Kiss1(-/-) female mice, acute replacement of gonadotropins and estradiol restores ovulation, mating, and fertilization; however, these mice are still unable to achieve pregnancy because embryos fail to implant. Progesterone treatment did not overcome this defect. Kiss1(+/-) embryos transferred to a wild-type female mouse can successfully implant, demonstrating the defect is due to maternal factors. Kisspeptin and its receptor are expressed in the mouse uterus, and we suggest that it is the absence of uterine kisspeptin signaling that underlies the implantation failure. This absence, however, does not prevent the closure of the uterine implantation chamber, proper alignment of the embryo, and the ability of the uterus to undergo decidualization. Instead, the loss of Kiss1 expression specifically disrupts embryo attachment to the uterus. We observed that on the day of implantation, leukemia inhibitory factor (Lif), a cytokine that is absolutely required for implantation in mice, is weakly expressed in Kiss1(-/-) uterine glands and that the administration of exogenous Lif to hormone-primed Kiss1(-/-) female mice is sufficient to partially rescue implantation. Taken together, our study reveals that uterine kisspeptin signaling regulates glandular Lif levels, thereby identifying a novel and critical role for kisspeptin in regulating embryo implantation in the mouse. This study provides compelling reasons to explore this role in other species, particularly livestock and humans.

Fatness and fertility: which direction?

Metabolic status has long been thought to determine reproductive status, with abnormal metabolic phenotypes altering reproductive cascades, such as the onset of puberty. In this issue of the JCI, Tolson and colleagues provide evidence that kisspeptin, a hormone that promotes sexual maturation, regulates metabolism. Female mice lacking the kisspeptin receptor (KISS1R) gained more weight than control animals, and this weight gain was caused not by increased food consumption, but by an overall decrease in energy and metabolism. While this study provides a direct link between the kisspeptin pathway and metabolic output, more work will need to be done to determine whether alterations in this pathway contribute to human obesity.

Reversal and relapse of hypogonadotropic hypogonadism: resilience and fragility of the reproductive neuroendocrine system

CONTEXT

A subset of patients diagnosed with idiopathic hypogonadotropic hypogonadism (IHH) later achieves activation of their hypothalamic-pituitary-gonadal axis with normalization of steroidogenesis and/or gametogenesis, a phenomenon termed reversal.

OBJECTIVE

The objective of this study was to determine the natural history of reversal and to identify associated phenotypes and genotypes.

DESIGN, SETTING, AND SUBJECTS

This was a retrospective review of clinical, biochemical, and genetic features of patients with IHH evaluated at an academic medical center.

MAIN OUTCOME MEASURES

History of spontaneous fertility, regular menses, testicular growth, or normalization of serum sex steroids, LH secretory profiles, brain imaging findings, and sequences of 14 genes associated with IHH were reviewed.

RESULTS

Of 308 patients with IHH, 44 underwent reversal. Time-to-event analysis estimated a lifetime incidence of reversal of 22%. There were no differences in the rates of cryptorchidism, micropenis, or partial pubertal development in patients with reversal vs IHH patients without reversal. Fifteen patients with reversal (30%) had Kallmann syndrome (IHH and anosmia); one had undetectable olfactory bulbs on a brain magnetic resonance imaging scan. Subjects with reversal were enriched for mutations affecting neurokinin B signaling compared with a cohort of IHH patients without reversal (10% vs 3%, P = .044), had comparable frequencies of mutations in FGFR1, PROKR2, and GNRHR, and had no mutations in KAL1. Five men did not sustain their reversal and again developed hypogonadotropism.

CONCLUSIONS

Reversal of IHH may be more widespread than previously appreciated and occurs across a broad range of genotypes and phenotypes. Enrichment for mutations that disrupt neurokinin B signaling in patients who reversed indicates that, despite the importance of this signaling pathway for normal pubertal timing, its function is dispensable later in life. The occurrence of reversal in a patient with no olfactory bulbs demonstrates that these structures are not essential for normal reproductive function. Patients with IHH require lifelong monitoring for reversal and, if reversal occurs, subsequent relapse also may occur.

TACR3 mutations disrupt NK3R function through distinct mechanisms in GnRH-deficient patients

Neurokinin B (NKB) and its G-protein-coupled receptor, NK3R, have been implicated in the neuroendocrine control of GnRH release; however, little is known about the structure-function relationship of this ligand-receptor pair. Moreover, loss-of-function NK3R mutations cause GnRH deficiency in humans. Using missense mutations in NK3R we previously identified in patients with GnRH deficiency, we demonstrate that Y256H and Y315C NK3R mutations in the fifth and sixth transmembrane domains (TM5 and TM6), resulted in reduced whole-cell (79.3±7.2%) or plasma membrane (67.3±7.3%) levels, respectively, compared with wild-type (WT) NK3R, with near complete loss of inositol phosphate (IP) signaling, implicating these domains in receptor trafficking, processing, and/or stability. We further demonstrate in a FRET-based assay that R295S NK3R, in the third intracellular loop (IL3), bound NKB but impaired dissociation of Gq-protein subunits from the receptor compared with WT NK3R, which showed a 10.0 ± 1.3% reduction in FRET ratios following ligand binding, indicating activation of Gq-protein signaling. Interestingly, R295S NK3R, identified in the heterozygous state in a GnRH-deficient patient, also interfered with dissociation of G proteins and IP signaling from wild-type NK3R, indicative of dominant-negative effects. Collectively, our data illustrate roles for TM5 and TM6 in NK3R trafficking and ligand binding and for IL3 in NK3R signaling.

Ataxia and hypogonadism caused by the loss of ubiquitin ligase activity of the U box protein CHIP

Gordon Holmes syndrome (GHS) is a rare Mendelian neurodegenerative disorder characterized by ataxia and hypogonadism. Recently, it was suggested that disordered ubiquitination underlies GHS though the discovery of exome mutations in the E3 ligase RNF216 and deubiquitinase OTUD4. We performed exome sequencing in a family with two of three siblings afflicted with ataxia and hypogonadism and identified a homozygous mutation in STUB1 (NM_005861) c.737C→T, p.Thr246Met, a gene that encodes the protein CHIP (C-terminus of HSC70-interacting protein). CHIP plays a central role in regulating protein quality control, in part through its ability to function as an E3 ligase. Loss of CHIP function has long been associated with protein misfolding and aggregation in several genetic mouse models of neurodegenerative disorders; however, a role for CHIP in human neurological disease has yet to be identified. Introduction of the Thr246Met mutation into CHIP results in a loss of ubiquitin ligase activity measured directly using recombinant proteins as well as in cell culture models. Loss of CHIP function in mice resulted in behavioral and reproductive impairments that mimic human ataxia and hypogonadism. We conclude that GHS can be caused by a loss-of-function mutation in CHIP. Our findings further highlight the role of disordered ubiquitination and protein quality control in the pathogenesis of neurodegenerative disease and demonstrate the utility of combining whole-exome sequencing with molecular analyses and animal models to define causal disease polymorphisms.

Mutational analysis of TAC3 and TACR3 genes in patients with idiopathic central pubertal disorders

OBJECTIVE

To investigate the presence of variants in the TAC3 and TACR3 genes, which encode NKB and its receptor (NK3R), respectively, in a large cohort of patients with idiopathic central pubertal disorders.

SUBJECTS AND METHODS

Two hundred and thirty seven patients were studied: 114 with central precocious puberty (CPP), 73 with normosmic isolated hypogonadotropic hypogonadism (IHH), and 50 with constitutional delay of growth and puberty (CDGP). The control group consisted of 150 Brazilian individuals with normal pubertal development. Genomic DNA was extracted from peripheral blood and the entire coding region of both TAC3 and TACR3 genes were amplified and automatically sequenced.

RESULTS

We identified one variant (p.A63P) in NKB and four variants, p.G18D, p.L58L (c.172C>T), p.W275* and p.A449S in NK3R, which were absent in the control group. The p.A63P variant was identified in a girl with CPP, and p.A449S in a girl with CDGP. The known p.G18D, p.L58L, and p.W275* variants were identified in three unrelated males with normosmic IHH.

CONCLUSION

Rare variants in the TAC3 and TACR3 genes were identified in patients with central pubertal disorders. Loss-of-function variants of TACR3 were associated with the normosmic IHH phenotype.

Use of genetic models of idiopathic hypogonadotrophic hypogonadism in mice and men to understand the mechanisms of disease

Mutations in the genes encoding the neuropeptides kisspeptin and neurokinin B, as well as their receptors, are associated with gonadotrophin-releasing hormone (GnRH) deficiency and a failure to initiate and/or progress through puberty. Although the total number of patients studied to date is small, mutations in the kisspeptin pathway appear to result in lifelong GnRH deficiency. Mice with mutations in kisspeptin and the kisspeptin receptor, Kiss1(-/-) and Kiss1r(-/-), respectively, appear to be phenocopies of the human with abnormal sexual maturation and infertility. In contrast, mutations in the neurokinin B pathway lead to a more variable adult reproductive phenotype, with a subset of hypogonadotrophic individuals demonstrating paradoxical recovery of reproductive function later in life. While 'reversal' remains poorly understood, the ability to recover reproductive function indicates that neurokinin B may play different roles in the initiation of sexual maturation compared with the maintenance of adult reproductive function. Mice with mutations in the gene encoding the neurokinin B receptor, Tacr3, have abnormal oestrous cycles and subfertility but, similar to their human counterparts, appear less severely affected than mice with kisspeptin deficiency. Further investigations into the interaction between the kisspeptin and neurokinin B pathways will reveal key insights into how GnRH neuronal modulation occurs at puberty and throughout reproductive life.

Redundancy in Kiss1 expression safeguards reproduction in the mouse

Kisspeptin (Kiss1) signaling to GnRH neurons is widely acknowledged to be a prerequisite for puberty and reproduction. Animals lacking functional genes for either kisspeptin or its receptor exhibit low gonadotropin secretion and infertility. Paradoxically, a recent study reported that genetic ablation of nearly all Kiss1-expressing neurons (Kiss1 neurons) does not impair reproduction, arguing that neither Kiss1 neurons nor their products are essential for sexual maturation. We posited that only minute quantities of kisspeptin are sufficient to support reproduction. If this were the case, animals having dramatically reduced Kiss1 expression might retain fertility, testifying to the redundancy of Kiss1 neurons and their products. To test this hypothesis and to determine whether males and females differ in the required amount of kisspeptin needed for reproduction, we used a mouse (Kiss1-CreGFP) that has a severe reduction in Kiss1 expression. Mice that are heterozygous and homozygous for this allele (Kiss1(Cre/+) and Kiss1(Cre/Cre)) have ∼50% and 95% reductions in Kiss1 transcript, respectively. We found that although male Kiss1(Cre/Cre) mice sire normal-sized litters, female Kiss1(Cre/Cre) mice exhibit significantly impaired fertility and ovulation. These observations suggest that males require only 5% of normal Kiss1 expression to be reproductively competent, whereas females require higher levels for reproductive success.

Ataxia, dementia, and hypogonadotropism caused by disordered ubiquitination

BACKGROUND

The combination of ataxia and hypogonadism was first described more than a century ago, but its genetic basis has remained elusive.

METHODS

We performed whole-exome sequencing in a patient with ataxia and hypogonadotropic hypogonadism, followed by targeted sequencing of candidate genes in similarly affected patients. Neurologic and reproductive endocrine phenotypes were characterized in detail. The effects of sequence variants and the presence of an epistatic interaction were tested in a zebrafish model.

RESULTS

Digenic homozygous mutations in RNF216 and OTUD4, which encode a ubiquitin E3 ligase and a deubiquitinase, respectively, were found in three affected siblings in a consanguineous family. Additional screening identified compound heterozygous truncating mutations in RNF216 in an unrelated patient and single heterozygous deleterious mutations in four other patients. Knockdown of rnf216 or otud4 in zebrafish embryos induced defects in the eye, optic tectum, and cerebellum; combinatorial suppression of both genes exacerbated these phenotypes, which were rescued by nonmutant, but not mutant, human RNF216 or OTUD4 messenger RNA. All patients had progressive ataxia and dementia. Neuronal loss was observed in cerebellar pathways and the hippocampus; surviving hippocampal neurons contained ubiquitin-immunoreactive intranuclear inclusions. Defects were detected at the hypothalamic and pituitary levels of the reproductive endocrine axis.

CONCLUSIONS

The syndrome of hypogonadotropic hypogonadism, ataxia, and dementia can be caused by inactivating mutations in RNF216 or by the combination of mutations in RNF216 and OTUD4. These findings link disordered ubiquitination to neurodegeneration and reproductive dysfunction and highlight the power of whole-exome sequencing in combination with functional studies to unveil genetic interactions that cause disease. (Funded by the National Institutes of Health and others.).