Endocrine Abstracts

Azoospermia is a common condition of about 10% of all infertile men and this most severe clinical phenotype of male infertility can – in an otherwise healthy man – regularly be considered to have a genetic basis. An association of chromosomal aberrations and Y-chromosomal AZF-deletions with spermatogenic failure is well-established. However, since the latter were described over 10 years ago, basically no genetic causes have been found although many re-sequencing studies of candidate genes were performed. However, with the advent of new whole-genome analytic methods, there is hope to further elucidate the complex genetic origin of azoospermia. To-date, only one recent study analysed a relatively low number of 40 men with non-obstructive azoospermia (histology not mentioned) using whole genome single nucleotide polymorphism (SNP) arrays. Some SNPs were found significantly associated with the phenotype, but essentially none could be unequivocally replicated in a larger follow-up study. Two studies using array comparative genomic hybridisation (CGH) to identify chromosomal gains and losses (copy number variants, CNVs) not detectable by routine chromosome analysis are currently underway: a study of 9 patients with meiotic arrest and 20 controls yielded six ‘interesting regions’ not further described. The second study analysed larger numbers of azoospermic (N=54) men with customised array-CGH specific for the X-chromosome. However, only one CNV was found significantly more frequently in patients after several CNVs had also been analysed in 150 controls. In our own experience of array-CGH in well-characterised and highly-selected patient groups with azoospermia due to mixed atrophy, meiotic arrest or Sertoli-cell-only syndrome, we could identify a number of putatively causal recurring, patient-specific and private, sex-chromosomal CNVs/genes. The novel method of genome analysis by next-generation sequencing may hold the potential to identify additional causative genes for azoospermia.