Expanding the genetic spectrum of ANOS1 mutations in patients with congenital hypogonadotropic hypogonadism.
STUDY QUESTION
What is the prevalence and functional consequence of ANOS1 (KAL1) mutations in a group of men with congenital hypogonadotropic hypogonadism (CHH)?


SUMMARY ANSWER
Three of forty-two (7.1%) patients presented ANOS1 mutations, including a novel splice site mutation leading to exon skipping and a novel contiguous gene deletion associated with ichthyosis.


WHAT IS KNOWN ALREADY
CHH is characterized by lack of pubertal development and infertility, due to deficient production, secretion or action of GnRH, and can be associated with anosmia/hyposmia (Kallmann syndrome, KS) or with a normal sense of smell (normosmic CHH). Mutations in the anosmin-1 (ANOS1) gene are responsible for the X-linked recessive form of KS.


STUDY DESIGN, SIZE, DURATION
This cross-sectional study included 42 unrelated men with CHH (20 with KS and 22 with normosmic CHH).


PARTICIPANTS/MATERIALS, SETTING, METHODS
Patients were screened for mutations in the ANOS1 gene by DNA sequencing. Identified mutations were further investigated by RT-PCR analysis and multiplex ligation-dependent probe amplification (MLPA) analysis.


MAIN RESULTS AND THE ROLE OF CHANCE
Hemizygous mutations were identified in three (7.1%) KS cases: a novel splice acceptor site mutation (c.542-1G>C), leading to skipping of exon 5 in the ANOS1 transcript in a patient with self-reported normosmia (but hyposmic upon testing); a recurrent nonsense mutation (c.571C>T, p.Arg191*); and a novel 4.8 Mb deletion involving ANOS1 and eight other genes (VCX3B, VCX2, PNPLA4, VCX, STS, HDHD1, VCX3A and NLGN4X) in KS associated with ichthyosis.


LIMITATIONS, REASONS FOR CAUTION
Objective olfactory testing was not performed in all cases of self-reported normosmia and this may have underestimated the olfactory deficits.


WIDER IMPLICATIONS OF THE FINDINGS
This study further expands the spectrum of known genetic defects associated with CHH and suggests that patients with self-reported normal olfactory function should not be excluded from ANOS1 genetic testing.


STUDY FUNDING/COMPETING INTEREST(S)
This study was funded by the Portuguese Foundation for Science and Technology. The authors have no conflicts of interest.


TRIAL REGISTRATION NUMBER
N/A.
['Gonçalves|C I|CI|', 'Fonseca|F|F|', 'Borges|T|T|', 'Cunha|F|F|', 'Lemos|M C|MC|']
D000483:Alleles D003430:Cross-Sectional Studies D004252:DNA Mutational Analysis D005091:Exons D016326:Extracellular Matrix Proteins D005260:Female D005787:Gene Frequency D006801:Humans D007006:Hypogonadism D017436:Kallmann Syndrome D008297:Male D009154:Mutation D009419:Nerve Tissue Proteins D010375:Pedigree
ANOS1 mutation hypogonadotropic hypogonadism KAL1 Kallmann syndrome