Prevalence and Phenotypic Effects of Copy Number Variants in Isolated Hypogonadotropic Hypogonadism

Applications of genomic research in pediatric endocrine diseases

Recent advances in molecular genetics have advanced our understanding of the molecular mechanisms involved in pediatric endocrine disorders and now play a major role in mainstream medical practice. The spectrum of endocrine genetic disorders has 2 extremes: Mendelian and polygenic. Mendelian or monogenic diseases are caused by rare variants of a single gene, each of which exerts a strong effect on disease risk. Polygenic diseases or common traits are caused by the combined effects of multiple genetic variants in conjunction with environmental and lifestyle factors. Testing for a single gene is preferable if the disease is phenotypically and/or geneically homogeneous. Next-generation sequencing (NGS) can be applied to phenotypically and genetically heterogeneous conditions. Genome-wide association studies (GWASs) have examined genetic variants across the entire genome in a large number of individuals who have been matched for population ancestry and assessed for a disease or trait of interest. Common endocrine diseases or traits, such as type 2 diabetes mellitus, obesity, height, and pubertal timing, result from the combined effects of multiple variants in various genes that are frequently found in the general population, each of which contributes a small individual effect. Isolated founder mutations can result from a true founder effect or an extreme reduction in population size. Studies of founder mutations offer powerful advantages for efficiently localizing the genes that underlie Mendelian disorders. The Korean population has settled in the Korean peninsula for thousands of years, and several recurrent mutations have been identified as founder mutations. The application of molecular technology has increased our understanding of endocrine diseases, which have impacted on the practice of pediatric endocrinology related to diagnosis and genetic counseling. This review focuses on the application of genomic research to pediatric endocrine diseases using GWASs and NGS technology for diagnosis and treatment.

Understanding the genetics of human infertility

Reproduction involves a wide range of biological processes, including organ formation and development, neuroendocrine regulation, hormone production, and meiosis and mitosis. Infertility, the failure of reproduction, has become a major issue for human reproductive health and affects up to one in seven couples worldwide. Here, we review various aspects of human infertility, including etiology, mechanisms, and treatments, with a particular emphasis on genetics. We focus on gamete production and gamete quality, which is the core of successful reproduction. We also discuss future research opportunities and challenges to further expand our understanding of human infertility and improve patient care by providing precision diagnosis and personalized treatments.

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.

Genetic architecture of self-limited delayed puberty and congenital hypogonadotropic hypogonadism

Distinguishing between self limited delayed puberty (SLDP) and congenital hypogonadotropic hypogonadism (CHH) may be tricky as they share clinical and biochemical characteristics. and appear to lie within the same clinical spectrum. However, one is classically transient (SDLP) while the second is typically a lifetime condition (CHH). The natural history and long-term outcomes of these two conditions differ significantly and thus command distinctive approaches and management. Because the first presentation of SDLP and CHH is very similar (delayed puberty with low LH and FSH and low sex hormones), the scientific community is scrambling to identify diagnostic tests that can allow a correct differential diagnosis among these two conditions, without having to rely on the presence or absence of phenotypic red flags for CHH that clinicians anyway seem to find hard to process. Despite the heterogeneity of genetic defects so far reported in DP, genetic analysis through next-generation sequencing technology (NGS) had the potential to contribute to the differential diagnostic process between SLDP and CHH. In this review we will provide an up-to-date overview of the genetic architecture of these two conditions and debate the benefits and the bias of performing genetic analysis seeking to effectively differentiate between these two conditions.

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.