Hypogonadotropic Hypogonadism due to Novel FGFR1 Mutations

Clinical Characterization and Underlying Genetic Findings in Brazilian Patients with Syndromic Microcephaly Associated with Neurodevelopmental Disorders

Microcephaly is characterized by an occipitofrontal circumference at least two standard deviations below the mean for age and sex. Neurodevelopmental disorders (NDD) are commonly associated with microcephaly, due to perturbations in brain development and functioning. Given the extensive genetic heterogeneity of microcephaly, managing patients is hindered by the broad spectrum of diagnostic possibilities that exist before conducting molecular testing. We investigated the genetic basis of syndromic microcephaly accompanied by NDD in a Brazilian cohort of 45 individuals and characterized associated clinical features, as well as evaluated the effectiveness of whole-exome sequencing (WES) as a diagnostic tool for this condition. Patients previously negative for pathogenic copy number variants underwent WES, which was performed using a trio approach for isolated index cases (n = 31), only the index in isolated cases with parental consanguinity (n = 8) or affected siblings in familial cases (n = 3). Pathogenic/likely pathogenic variants were identified in 19 families (18 genes) with a diagnostic yield of approximately 45%. Nearly 86% of the individuals had global developmental delay/intellectual disability and 51% presented with behavioral disturbances. Additional frequent clinical features included facial dysmorphisms (80%), brain malformations (67%), musculoskeletal (71%) or cardiovascular (47%) defects, and short stature (54%). Our findings unraveled the underlying genetic basis of microcephaly in half of the patients, demonstrating a high diagnostic yield of WES for microcephaly and reinforcing its genetic heterogeneity. We expanded the phenotypic spectrum associated with the condition and identified a potentially novel gene (CCDC17) for congenital microcephaly.

Clinical manifestations and spermatogenesis outcomes in Chinese patients with congenital hypogonadotropic hypogonadism caused by inherited or de novo FGFR1 mutations

Fibroblast growth factor receptor 1 ( FGFR1 ) mutations are associated with congenital hypogonadotropic hypogonadism (CHH) through inheritance or spontaneous occurrence. We detected FGFR1 mutations in a Chinese cohort of 210 CHH patients at Peking Union Medical College Hospital (Beijing, China) using next-generation and Sanger sequencing. We assessed missense variant pathogenicity using six bioinformatics tools and compared clinical features and treatment outcomes between inherited and de novo mutation groups. Among 19 patients with FGFR1 mutations, three were recurrent, and 16 were novel variants. Sixteen of the novel mutations were likely pathogenic according to the American College of Medical Genetics and Genomics (ACMG) guidelines, with the prevalent P366L variant. The majority of FGFR1 mutations was inherited (57.9%), with frameshift mutations exclusive to the de novo mutation group. The inherited mutation group had a lower incidence of cryptorchidism, short stature, and skeletal deformities. In the inherited mutation group, luteinizing hormone (LH) levels were 0.5 IU l -1 , follicle-stimulating hormone (FSH) levels were 1.0 IU l -1 , and testosterone levels were 1.3 nmol l -1 . In contrast, the de novo group had LH levels of 0.2 IU l -1 , FSH levels of 0.5 IU l -1 , and testosterone levels of 0.9 nmol l -1 , indicating milder hypothalamus-pituitary-gonadal axis (HPGA) functional deficiency in the inherited group. The inherited mutation group showed a tendency toward higher spermatogenesis rates. In conclusion, this study underscores the predominance of inherited FGFR1 mutations and their association with milder HPGA dysfunction compared to de novo mutations, contributing to our understanding of the genetic and clinical aspects of FGFR1 mutations.

Multi-ancestry genome-wide association analyses improve resolution of genes and pathways influencing lung function and chronic obstructive pulmonary disease risk

Lung-function impairment underlies chronic obstructive pulmonary disease (COPD) and predicts mortality. In the largest multi-ancestry genome-wide association meta-analysis of lung function to date, comprising 580,869 participants, we identified 1,020 independent association signals implicating 559 genes supported by ≥2 criteria from a systematic variant-to-gene mapping framework. These genes were enriched in 29 pathways. Individual variants showed heterogeneity across ancestries, age and smoking groups, and collectively as a genetic risk score showed strong association with COPD across ancestry groups. We undertook phenome-wide association studies for selected associated variants as well as trait and pathway-specific genetic risk scores to infer possible consequences of intervening in pathways underlying lung function. We highlight new putative causal variants, genes, proteins and pathways, including those targeted by existing drugs. These findings bring us closer to understanding the mechanisms underlying lung function and COPD, and should inform functional genomics experiments and potentially future COPD therapies.

New developments in the biology of fibroblast growth factors

The fibroblast growth factor (FGF) family is composed of 18 secreted signaling proteins consisting of canonical FGFs and endocrine FGFs that activate four receptor tyrosine kinases (FGFRs 1-4) and four intracellular proteins (intracellular FGFs or iFGFs) that primarily function to regulate the activity of voltage-gated sodium channels and other molecules. The canonical FGFs, endocrine FGFs, and iFGFs have been reviewed extensively by us and others. In this review, we briefly summarize past reviews and then focus on new developments in the FGF field since our last review in 2015. Some of the highlights in the past 6 years include the use of optogenetic tools, viral vectors, and inducible transgenes to experimentally modulate FGF signaling, the clinical use of small molecule FGFR inhibitors, an expanded understanding of endocrine FGF signaling, functions for FGF signaling in stem cell pluripotency and differentiation, roles for FGF signaling in tissue homeostasis and regeneration, a continuing elaboration of mechanisms of FGF signaling in development, and an expanding appreciation of roles for FGF signaling in neuropsychiatric diseases. This article is categorized under: Cardiovascular Diseases > Molecular and Cellular Physiology Neurological Diseases > Molecular and Cellular Physiology Congenital Diseases > Stem Cells and Development Cancer > Stem Cells and Development.

A simultaneous next-generation sequencing approach to the diagnosis of couple infertility

BACKGROUND

Infertility is a disorder of the male and/or female reproductive system, characterized by failure to establish a clinical pregnancy after 12 months of regular unprotected sexual intercourse. On a world basis, about one in six couplesare affected by infertility during their reproductive lifespan. Despite a comprehensive diagnostic work-up, infertility in about 50% of couples remains idiopathic. In this context, a next-generation sequencing (NGS) approach has been suggested to increase diagnostic yield. Accordingly, this study aimed to evaluate the effectiveness of a custom-made NGS gene panel for the simultaneous genetic diagnosis of both partners of a large population of infertile couples.

METHODS

We developed a custom-made NGS panel for 229 genes associated with male and female infertility. The panel targeted exons and their flanking regions and was used to screen 99 couples with idiopathic infertility.

RESULTS

NGS sequencing revealed five pathogenic variants in six couples and 17 likely pathogenic variants or variants with uncertain significance (VUS). The pathogenic variants were identified in the following genes: GNRHR, CCDC39, DNAH5, and CCDC103; likely pathogenic variants were identified in TAC3, PROKR2, and CFTR; VUS were identified in CATSPER2, FGFR1, LRRC6, DNAH5, DNAH11, TGFBR3, and DNAI1.

CONCLUSIONS

The panel of genes designed for this study allowed the identification of pathogenetic gene mutations and the presence of VUS in 6.1% and 17.2%, respectively, of couples with idiopathic infertility. This is the first study to successfully apply an NGS-based genetic screening including 229 genes known to play a role in both male and female infertility.

Combined in vitro and in silico analyses of FGFR1 variants: genotype-phenotype study in idiopathic hypogonadotropic hypogonadism

Fibroblast growth factor receptor 1 (FGFR1) is an idiopathic hypogonadotropic hypogonadism (IHH)-associated gene, mutated in approximately 10% of the patients with this condition. Through targeted gene sequencing of 153 males with IHH and 100 healthy controls, we identified 10 mutations in FGFR1 from IHH patients with a frequency of 5.9% in the Chinese population of central China. These included nine missense mutations(NM_023110.2, p.Gly687Arg, p.Ala608Asp, p.Gly348Glu, p.Asn296Ser, p.Gly226Asp, p.Arg209Cys, p.Gly97Arg, p.Val71Met, p.Gly70Arg) and a splicing mutation c.1430 + 1G > T. in vitro and in silico analyses of FGFR1 variants were conducted to study the impact of the identified mutations. Our findings indicated that the splicing mutation dramatically affected premRNA processing, causing exon 10 and 6 nucleotides in the 3' end of exon 9 to be completely skipped. Two variants (p.Gly687Arg and p.Ala608Asp) markedly impaired tyrosine kinase activity, while the other variants had limited impact on the mitogen-activated protein kinase (MAPK) signaling pathway. However, the functional impairment of the mutant receptors was not always consistent with the phenotypes, indicating that FGFR1 mutations might cause IHH in conjunction with other mutant genes. In this study, we expanded the knowledge on the mutation spectrum of FGFR1 in IHH patients and explored the genotype-phenotype relationship.

Molecular cytogenetic characterization of mosaicism for a small supernumerary marker chromosome derived from chromosome 8 associated with congenital hypoplasia of the tongue and review of the literature

OBJECTIVE

To present molecular cytogenetic characterization of mosaic supernumerary ring chromosome 8 which has trisomy of a region of chromosome 8p12-q21.13 associated with congenital hypoplasia of the tongue and review of the literature.

CASE REPORT

A 27 year-old woman presented with congenital hypoplasia of the tongue. The chromosome karyotype of peripheral blood lymphocytes was detected by conventional cytogenetic analysis. The genome copy number variations were detected by SNP array. Conventional cytogenetic analysis of the peripheral blood revealed a karyotype of 47,XX,+mar[60]/46,XX[40]. SNP array revealed that there was a duplication of 45.2 Mb at arr[hg19] 8p12q21.13(36,013,636-81,263,140) × 2-3.

CONCLUSION

With this study a patient involving mosaic trisomy 8p12-q21.13 along with clinical properties, is described and compared to previously reported cases involving a small supernumerary marker chromosome (sSMC) derived from chromosome 8.