Infertility is a relatively common health condition, affecting nearly 7% of all couples. Clinically, it
is a highly heterogeneous pathology with a complex etiology that includes environmental and
genetic factors. It has been estimated that nearly 50% of infertility cases are due to genetic defects.
Hundreds of studies with animal knockout models convincingly showed infertility to be caused by
gene defects, single or multiple. However, despite enormous efforts, progress in translating basic
research findings into clinical studies has been challenging. The genetic causes remain
unexplained for the vast majority of male or female infertility patients. A particular difficulty is
the huge number of candidate genes to be studied; there are more than 2,300 genes expressed in
the testis alone, and hundreds of those genes influence reproductive function in humans and could
contribute to male infertility. At present, there are only a handful of genes or genetic defects that
have been shown to cause, or to be strongly associated with, primary infertility. Yet, with
completion of the human genome and progress in personalized medicine, the situation is rapidly
changing. Indeed, there are 10-15 new gene tests, on average, being added to the clinical genetic
testing list annually.