Normosmic idiopathic hypogonadotrophic hypogonadism due to a rare KISS1R gene mutation

Etiology of Male Infertility: an Update

Spermatogenesis is a complex process of germ cell division and differentiation that involves extensive cross-talk between the developing germ cells and the somatic testicular cells. Defective endocrine signaling and/or intrinsic defects within the testes can adversely affect spermatogenic progression, leading to subfertility/infertility. In recent years, male infertility has been recognized as a global public health concern, and research over the last few decades has elucidated the complex etiology of male infertility. Congenital reproductive abnormalities, genetic mutations, and endocrine/metabolic dysfunction have been demonstrated to be involved in infertility/subfertility in males. Furthermore, acquired factors like exposure to environmental toxicants and lifestyle-related disorders such as illicit use of psychoactive drugs have been shown to adversely affect spermatogenesis. Despite the large body of available scientific literature on the etiology of male infertility, a substantial proportion of infertility cases are idiopathic in nature, with no known cause. The inability to treat such idiopathic cases stems from poor knowledge about the complex regulation of spermatogenesis. Emerging scientific evidence indicates that defective functioning of testicular Sertoli cells (Sc) may be an underlying cause of infertility/subfertility in males. Sc plays an indispensable role in regulating spermatogenesis, and impaired functional maturation of Sc has been shown to affect fertility in animal models as well as humans, suggesting abnormal Sc as a potential underlying cause of reproductive insufficiency/failure in such cases of unexplained infertility. This review summarizes the major causes of infertility/subfertility in males, with an emphasis on infertility due to dysregulated Sc function.

Normosmic idiopathic hypogonadotropic hypogonadism due to a novel GNRH1 variant in two siblings

SUMMARY

Hypogonadotropic hypogonadism is characterised by insufficient secretion of pituitary gonadotropins resulting in delayed puberty, anovulation and azoospermia. When hypogonadotropic hypogonadism occurs in the absence of structural or functional lesions of the hypothalamic or pituitary gland, the hypogonadism is defined as idiopathic hypogonadotropic hypogonadism (IHH). This is a rare genetic disorder caused by a defect in the secretion of gonadotropin releasing hormone (GNRH) by the hypothalamus or a defect in the action of GNRH on the pituitary gland. Up to 50% of IHH cases have identifiable pathogenic variants in the currently known genes. Pathogenic variants in the GNRHR gene encoding the GNRH receptor are a relatively common cause of normosmic IHH, but reports of pathogenic variants in GNRH1 encoding GNRH are exceedingly rare. We present a case of two siblings born to consanguineous parents who were found to have normosmic idiopathic hypogonadotropic hypogonadism due to homozygosity of a novel loss-of function variant in GNRH1. Case 1 is a male who presented at the age of 17 years with delayed puberty and under-virilised genitalia. Case 2 is a female who presented at the age of 16 years with delayed puberty and primary amenorrhea.

LEARNING POINTS

IHH is a genetically heterogeneous disorder which can be caused by pathogenic variants affecting proteins involved in the pulsatile gonadotropin-releasing hormone release, action, or both. Currently known genetic defects account for up to 50% of all IHH cases. GNRH1 pathogenic variants are a rare cause of normosmic IHH. IHH is associated with a wide spectrum of clinical manifestations. IHH can be challenging to diagnose, particularly when attempting to differentiate it from constitutional delay of puberty. Early diagnosis and gonadotrophin therapy can prevent negative physical sequelae and mitigate psychological distress with the restoration of puberty and fertility in affected individuals.

An Isolated Hypogonadotropic Hypogonadism due to a L102P Inactivating Mutation of KISS1R/GPR54 in a Large Family

KISS1R (GPR54) mutations have been reported in several patients with congenital normosmic idiopathic hypogonadotropic hypogonadism (nIHH). We aim to describe in detail nIHH patients with KISS1R (GPR54) mutations belonging to one related extended family and to review the literature. A homozygous mutation (T305C) leading to a leucine substitution with proline (L102P) was found in three affected kindred (2 males and 1 female) from a consanguineous Saudi Arabian family. This residue is localized within the first exoloop of the receptor, affects a highly conserved amino acid, perturbs the conformation of the transmembrane segment, and impairs its function. In the affected female, a combined gonadotropin administration restored regular period and ovulation and she conceived with a healthy baby boy after 4 years of marriage. We showed that a loss-of-function mutation (p.Tyr305C) in the KISS1R gene can cause (L102P) KISS1 receptor dysfunction and familial nIHH, revealing the crucial role of this amino acid in KISS1R function. The observed restoration of periods and later on pregnancy by an exogenous gonadotropin administration further support, in humans, that the KISS1R mutation has no other harmful effects on the patients apart from the gonadotropin secretion impairment.

Identification of KISS1R gene mutations in disorders of non-obstructive azoospermia in the northeast population of China

Background

Non‐obstructive azoospermia (NOA), a serious phenotype of male spermatogenesis failure, is a multifactorial disease which is regulated by genetic, epigenetic, and environmental factors. Some gene structural variants have been demonstrated to be related to NOA. Loss‐of‐function mutations of KISS1R cause normosmic idiopathic hypogonadotropic hypogonadism (IHH) which result in azoospermia at the pre‐testicular level. The objective of this research was to investigate genetic variants of KISS1R in NOA patients.

Methods

The entire coding region of 52 spermatogenesis‐associated genes (KISS1R included) was sequenced from 200 NOA patients. Mutation screening was performed to identify genetic variations of these genes by targeted exome sequencing. Sequencing data analysis was carried out by a series of bioinformatics tools. Candidate variants confirmation was performed by Sanger sequencing. Functional analysis of candidate variants was evaluated using SIFT and PolyPhen‐2.

Results

Three heterozygous missense variants in KISS1R were identified in three patients, respectively. No deleterious variations in other candidate genes were found in the three patients. Two of these three variants, p.A211T and p.G186E, had been reported in the ExAC and dbSNP database, respectively, while the other variant p.A301D was novel. These variants were all predicted to be likely pathogenic by in silico analysis.

Conclusion

Our study revealed three heterozygous missense variants in KISS1R which expanded the mutation spectrum of KISS1R in infertile men with NOA in the northeast of China.

Three Siblings with Idiopathic Hypogonadotropic Hypogonadism in a Nonconsanguineous Family: A Novel KISS1R/GPR54 Loss-of-Function Mutation

Idiopathic hypogonadotropic hypogonadism (IHH) is a rare disease caused by defects in the secretion of gonadotropin releasing hormone (GnRH) or the action of GnRH on the pituitary gonadotrophes. KISS1R is one of the genes which, when mutated, cause IHH and mutations of this gene are responsible for about 2-5% of patients with normosmic IHH (NIHH). In this report, we present three siblings with NIHH due to a compound heterozygous KISS1R mutation. Genetic studies were carried out in the 14 year old index case with IHH and three siblings, two of whom were prepubertal. Genomic DNA was extracted from peripheral leukocytes and KISS1R gene was sequenced by using standard polymerase chain reaction amplification procedures. In molecular analysis of the index case, a compound heterozygous mutation was determined in KISS1R gene c.969C>A (p.Y323X) (known pathogenic) and c.170T>C (p.L57P) (novel). Mutation c.170T>C (p.L57P) was inherited from the mother while c.969C>A (p.Y323X) was inherited from the father. The same genotype was also found in two of the three siblings. A compound heterozygous mutation of the KISS1 gene, including one novel mutation, was found to cause NIHH and also incomplete puberty in a non-consanguineous family.

Understanding the functions of kisspeptin and kisspeptin receptor (Kiss1R) from clinical case studies

It is widely acknowledged that kisspeptin and its receptor Kiss1R play central regulatory roles in the hypothalamus-pituitary-gonad (HPG) axis and reproduction. Mutations of KISS1 and KISS1R lead to disorders associated with pubertal development, such as central precocious puberty (CPP) and idiopathic hypogonadotropic hypogonadism (IHH). This review focuses on KISS1 and KISS1R mutations found in CPP and IHH and its purposes are twofold: Firstly, based on the mutations found in KISS1 and KISS1R, this review provides insights into the precise mechanism of kisspeptin and the kisspeptin/Kiss1R pathway in the reproductive axis and in puberty. Secondly, G protein-coupled receptors (GPCRs) are known to share highly conserved structural motifs; therefore, knowledge of mutations found at different structural domains of Kiss1R in the diseased state, and how they affect Kiss1R function can be used to decipher GPCR domain function.