Mutation spectrum and frequency of copy number variations of the ANOS1 gene in patients with Kallmann syndrome or normosmic isolated hypogonadotropic hypogonadism

Objective: This study was performed to investigate the molecular characteristics and frequency of copy number variations (CNVs) of ANOS1 in patients with Kallmann syndrome (KS) or normosmic isolated hypogonadotropic hypogonadism (nIHH) using multiplex ligation-dependent probe amplification (MLPA) analysis and sequencing.

Methods: Among 45 patients from 43 independent families, Sanger sequencing, next-generation sequencing (NGS), or microarray was performed in 24 patients from 23 families, and MLPA was performed in 19 patients who did not show rare sequence variants (n = 18) or ANOS1 amplification by PCR (n = 1).

Results: Seven patients (four patients with KS, one patient with nIHH, one prepubertal boy with anosmia, and one newborn patient) from six families (6/43, 14%) harbored molecular defects in ANOS1 including a nonsense mutation (c.1140G>A (p.W380*)), a frameshift mutation (c.1260del (p.Q421Kfs*61)), a splice site mutation (c.1449+1G>A), an exon 7 deletion, a complete deletion, and 7.9 Mb-sized inversion encompassing ANOS1. The complete deletion of ANOS1 was identified in a neonate with a micropenis and cryptorchidism. Unilateral renal agenesis was found in three patients, whereas only one patient displayed both synkinesia and sensorineural hearing loss. There was no reversal of hypogonadotropic hypogonadism in any patient during 9.1 ± 2.9 years of treatment with testosterone enanthate.

Conclusions: Molecular defects in the ANOS1 gene could be identified in 14% of probands including various types of CNVs (3/43, 7.0%). Comprehensive analysis using sequencing and analysis for CNVs is required to detect molecular defects in ANOS1.