Inactivating NHLH2 Variants Cause Idiopathic Hypogonadotropic Hypogonadism and Obesity in Humans

Metabolism has a role in determining the time of pubertal development and fertility. Nonetheless, molecular/cellular pathways linking metabolism/body weight to puberty/reproduction are unknown. The KNDy (Kisspeptin/Neurokinin B/Dynorphin) neurons in the arcuate (ARC) nucleus of the hypothalamus constitute the GnRH (Gonadotrophin-releasing hormone) pulse generator. We previously created a mouse model with a whole-body targeted deletion of nescient helix-loop-helix 2 (Nhlh2; N2KO), a class II member of the basic helix-loop-helix (bHLH) family of transcription factors. As this mouse model features pubertal failure and late-onset obesity, we wanted to study whether NHLH2 represents a candidate molecule to link metabolism and puberty in the hypothalamus. Exome sequencing of a large Idiopathic Hypogonadotropic Hypogonadism (IHH) cohort revealed obese patients with rare sequence variants in NHLH2, which were characterized by in silico protein analysis, chromatin immunoprecipitation, and luciferase reporter assays. In vitro heterologous expression studies demonstrated that the variant p.R79C impairs Nhlh2 binding to the Mc4r promoter. Furthermore, p.R79C and other variants show impaired transactivation of the human KISS1 promoter. These are the first inactivating human variants that support NHLH2’s critical role in human puberty and body weight control. Failure to carry out this function results in the absence of pubertal development and late-onset obesity in humans.

Temperature is not a major factor in the differentiation of gonocytes into ad spermatogonia and fertility outcome in congenitally cryptorchid boys

Spermatogenesis in mammals is a heat-sensitive developmental pathway incompatible with the typical mammalian body temperature of 37 °C. It is thought that this is the reason why the testicles of most mammalian males are outside of the body cavity, in the scrotum, where they function at approximately 33 °C. It has been suggested that the abnormally high temperature environment of cryptorchid testes may lead to impaired testicular development and adult infertility. Here, I summarize the clinical, genetic, and histological evidence that argues against temperature stress and in favor of hypogonadotropic hypogonadism as the underlying cause of adult infertility in cryptorchidism.Patient summary: Infertility and an increased risk of testicular cancer in patients diagnosed with undescended testes are the consequence of a hormonal deficiency rather than temperature-induced cellular damage. Cryptorchidism therefore requires both surgical and hormonal treatment.

Multifaceted and Age-Dependent Phenotypes Associated With Biallelic PNPLA6 Gene Variants: Eight Novel Cases and Review of the Literature

A wide spectrum of neurodegenerative diseases has been associated with pathogenic variants in the PNPLA6 (patatin-like phospholipase domain-containing protein 6) gene, including spastic paraplegia type 39, Gordon—Holmes, Boucher—Neuhauser, Oliver—Mc Farlane, and Laurence—Moon syndromes. These syndromes present variable and overlapping clinical symptoms, encompassing cerebellar ataxia, hypogonadotropic hypogonadism, chorioretinal dystrophy, spastic paraplegia, muscle wasting, peripheral neuropathy, and cognitive impairment. In the present study, we performed a wide genetic screening in 292 patients presenting with ataxia or spastic paraplegia using a probe-based customized gene panel, covering >200 genes associated with spinocerebellar diseases. We identified six novel and four recurrent PNPLA6 gene variants in eight patients (2.7%). Six patients presented an infantile or juvenile onset (age <18), and two patients had an adult onset. Cerebellar ataxia was observed in seven patients and spastic paraplegia in one patient. Progression of cerebellar symptoms was slow in all patients, who retained ambulation even after a mean disease duration of 15 years. Brain MRI showed cerebellar atrophy in 6/8 patients, more pronounced in superior and dorsal vermis lobules (I to VII). Additional clinical features included hypogonadotropic hypogonadism (5/8), growth hormone deficiency (2/8), peripheral axonal neuropathy (4/8), cognitive impairment (3/8), chorioretinal dystrophy (2/8), and bilateral vestibular areflexia with a reduced visual vestibule-ocular reflex (1/8). In accordance with previous studies, chorioretinal dystrophy was the most frequent presenting symptom in early onset patients, hypogonadotropic hypogonadism in juvenile onset cases, and cerebellar ataxia in adult patients. One patient had an initial clinical presentation compatible with Cerebellar Ataxia with Neuropathy and Vestibular Areflexia Syndrome (CANVAS), but no pathological expansions in the RFC1 gene. In conclusion, patients with PNPLA6 variants present a variable age of onset spanning from infancy to adulthood, and each clinical symptom has an age-dependent manifestation thus requiring a multi-systemic diagnostic approach. The description of patients presenting very late-onset cerebellar ataxia suggests that PNPLA6 genetic screening should also be considered in the diagnostic workout of adult cerebellar ataxia.

Novel Splice-Site and Missense Variant of PNPLA6 in an Austrian Family Causing Spastic Paraplegia-39 with Cerebellar Oculomotor Disorder

Background The term hereditary spastic paraplegia comprises an ever-expanding array of neurological disorders with distinct aetiologies. Spastic paraplegia 39 is one of the many variants with additional features of other organs and neurological systems. We describe a large kindred with two hitherto undescribed mutations of PNPLA6 and a novel clinical phenotype as, in addition to spastic paraplegia, affected subjects suffered from a prominent cerebellar oculomotor dysfunction. Methods Three of five genetically tested family members of a large kindred were affected by spastic gait and cerebellar oculomotor dysfunction. Clinical, imaging, laboratory and electrophysiological data were analyzed. Genetic analysis was done using next-generation sequencing. Segregation analyses were performed by Sanger sequencing. To assess the pathogenicity of genetic variants on the encoded protein, in silico assessments were carried out. Results Two hitherto unknown sequence variants in the PNPLA6 gene, a splice-site variant c.1635+3G>T and a missense variant c.3401A>T, p.(Asp1134Val), were detected. Compound-heterozygous siblings presented with lower limb spasticity and a marked cerebellar oculomotor disorder accompanied by moderate hypogonadotropic hypogonadism in the female. A paternal uncle being homozygous for the splice-site variant of PNPLA6 presented with increased lower limb reflexes, an unstable gait and cerebellar oculomotor dysfunction. Treatment with 4-aminopyridin, a potassium channel blocker, lead to meaningful improvement of clinical symptoms. Conclusion PNPLA6 gene variants are associated with a broad phenotypic spectrum to which we add cerebellar oculomotor dysfunction. In our kindred, the full clinical manifestation only occurred in compound-heterozygous subjects indicating that biallelic pathogenic variants lead to more serious and earlier onset of symptoms. Our findings emphasize the role of PNPLA6 in different neurodegenerative disorders.

Classification of CHD7 Rare Variants in Chinese Congenital Hypogonadotropic Hypogonadism Patients and Analysis of Their Clinical Characteristics

Purpose:CHD7 rare variants can cause congenital hypogonadotropic hypogonadism (CHH) and CHARGE syndrome. We aimed to summarize the genotype and phenotype characteristics of CHH patients with CHD7 rare variants.Methods: Rare sequencing variants (RSVs) were detected by Sanger sequencing in a series of 327 CHH patients and were interpreted and grouped according to the American College of Medical Genetics and Genomics (ACMG) guideline. Detailed phenotyping and genotype-phenotype correlation were analyzed.Results: The RSV detection rate was 11.01% (36/327) in the CHH patients. We identified 30 RSVs and 19 of them were novel. Following ACMG criteria, three variants were pathogenic (P), 4 were likely pathogenic (LP), 3 were of uncertain significance with paradoxical evidence (US1), and 20 were of uncertain significance without enough evidence (US2). All patients (4/4, 100%) with P or LP variants manifested extragonadal symptoms.Conclusion: Addition of 19 novel CHD7 variants expanded the spectrum of variants, and pathogenic or likely pathogenic RSVs were more likely to cause syndromic CHH. For CHH patients carrying CHD7 RSVs, detailed genotyping and phenotyping can facilitate clinical diagnosis and therapy.

Phenotypic spectrum of patients with mutations in CHD7: clinical implications of endocrinological findings

Objective: Heterozygous CHD7 mutations cause a broad spectrum of clinical phenotypes ranging from typical CHARGE syndrome to self-limited delayed puberty. This study aimed to investigate the clinical characteristics of endocrine dysfunction in patients with CHD7 mutations. Methods: The clinical features and endocrine findings from 30 patients with CHD7 variants were retrospectively reviewed. A diagnosis of CHARGE syndrome was based on the Verloes diagnostic criteria. Results: Seventeen patients fulfilled the criteria for typical CHARGE syndrome, one patient for partial/incomplete CHARGE, and the remaining 11 patients had atypical CHARGE syndrome. One patient was diagnosed with Kallmann syndrome and unilateral deafness. The most frequently observed features were inner ear anomalies (80.0%), intellectual disability (76.7%), and external ear anomalies (73.3%). The mean height and weight SDSs at diagnosis were -2.6 ± 1.3 and -2.2 ± 1.8, respectively. Short stature was apparent in 18 patients (60%), and one patient was diagnosed with growth hormone deficiency. Seventeen males showed genital hypoplasia, including micropenis, cryptorchidism, or both. Seven patients after pubertal age had hypogonadotropic hypogonadism with hyposmia/anosmia and olfactory bulb hypoplasia. Truncating CHD7 mutations were the most common (n = 22), followed by missense variants (n = 3), splice-site variants (n = 2), and large deletion (n = 2). Conclusions: A diverse phenotypic spectrum was observed in patients with CHD7 variants, and endocrine defects such as short stature and delayed puberty occurred in most patients. Endocrine evaluation, especially for growth and pubertal impairment, should be performed during diagnosis and follow-up to improve the patient’s quality of life.