About 1% of all men are affected by azoospermia, i.e. their ejaculate does not contain any sperm cells. Either sperm are produced normally in the testis, but due to a blockage they are not released into the ejaculate (obstructive azoospermia, OA), or no or very few sperm are produced (non-obstructive azoospermia, NOA). The causes for both forms are manifold, and natural conception is not possible.

In non-obstructive azoospermia, genetic causes play the largest role, but the majority currently remains elusive. Hence, more than 70% of azoospermic men are not given a causal diagnosis and, in turn, cannot receive individual counselling and treatment. For this very reason, all patients are offered a testicular biopsy to obtain sperm - but this proves successful in only about 50% of attempts.

Accordingly, our objective is to understand the genetic causes of azoospermia and to derive clinically relevant diagnostics and counselling. To this end, we launched the 'Male Reproductive Genomics' (MERGE) study in 2017. Since then, we have been sequencing the exome/genome of infertile men to identify new candidate genes, followed by segregation and functional analyses of testicular tissue, cellular systems or by use of the fruit fly (Drosophila).