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.

Mutation profiles and clinical characteristics of Chinese males with isolated hypogonadotropic hypogonadism

OBJECTIVE

To investigate the mutation profiles and clinical characteristics of Chinese males with isolated hypogonadotropic hypogonadism (IHH) and discover new pathogenic genes that cause IHH.

DESIGN

A gene panel, including 31 known IHH genes and 52 candidate genes, was used to perform semiconductor next-generation sequencing.

SETTING

University hospital.

PATIENTS

One hundred thirty-eight sporadic male IHH patients and 10 IHH families; 100 healthy men with normal fertility served as control subjects.

INTERVENTIONS(S)

None.

MAIN OUTCOME MEASURE(S)

Targeted next-generation sequencing, polymerase chain reaction and sequencing, pedigree analysis, and bioinformatics analysis.

RESULT(S)

Variants were distributed uniformly throughout 52 genes (52/83, 62.65%), including 16 (16/31, 51.61%) causal genes and 36 (36/52, 69.23%) candidate genes. Six new pathogenic variants and 52 likely pathogenic variants were identified in 16 genes known to cause nIHH/KS (normosmic IHH/Kallmann syndrome). In the 148 probands, PROKR2 (22/148, 14.86%), CHD7, FGFR1, and KAL1 had high mutation rates, and 8.78% (13/148) of the patients carried at least two variants in known genes. In addition, variants were identified in 36 candidate genes, and EGFR, ERBB4, PAX6, IGF1, SEMA4D, and SEMA7A should be prioritized for further research and genetic testing in IHH.

CONCLUSION(S)

The mutation frequency of IHH-causal genes in Chinese HAN males was different from the data reported in white populations. Oligogenic inheritance was a common phenomenon in IHH. Our study expands the mutation profile for IHH, and the new likely pathogenic genes identified in our study warrant further research in GnRH neuronal networks.