Background: To date at least 30 genes are known to be associated with idiopathic hypogonadotropic hypogonadism (IHH). Analysis of all these gene candidates by Sanger sequencing would be expensive, labour-intensive and time-consuming. Recent introduction of next-generation sequencing (NGS) enables simultaneous analysis of multiple gene targets making it an attractive approach in such conditions as IHH
Objective and hypotheses: To study the spectrum of molecular defects in IHH using a targeted NGS approach.
Method: 25 patients with IHH (males, n=23; females, n=2) were studied. five subjects showed features of Kallmann syndrome (KS), 20 were normosmic. Hypogonadotropic hypogonadism panel genes were sequenced using a custom Ion Ampliseq gene panel and PGM semiconductor sequencer (Ion Torrent). Bioinformatic analysis was performed using Torrent Suite (Ion Torrent) and ANNOVAR (annovar.openbioinformatics.org) software packages. Non-synonymous sequence variants were rated as probably pathogenic if they had allele frequency less than 1% and pathogenic ljb database scores.
Results: 21 heterozygous pathogenic or probably pathogenic mutations were found in 13 of 25 patients (52%). Distribution of mutations was as follows: CHD7, n=4; GNRHR, n=3; POLR3A, n=3; POLR3B, n=2; KAL1, n=2; PROKR2, n=2; FGFR1, n=1; HS6ST1, n=1; WDR11, n=1; FGF8, n=1; SPRY4, n=1. Mutations were identified in four of five KS cases, and in nine of 20 subjects with normosmic IHH. nine of 21 mutations were novel. In two patients mutations were found in more than two genes.
Conclusion: The results confirm predominance of mutations associated with defects of development and migration of GnRH neurons. The targeted NGS method can be successfully used for differential diagnosis of IHH.
Funding: Alfa-Endo Program of Charities Aid Foundation (CAF) Russia.
01 Oct 2015 - 03 Oct 2015