The genetic causes of male infertility are highly heterogeneous, and a large portion of these causes remains unexplained. More than 2300 testes-specific genes may contribute to male infertility [1]. Primary testicular disorders affecting spermatogenesis are commonly associated with abnormal semen parameters, including sperm concentration (oligozoospermia or azoospermia), morphology, motility, and vitality. Studies in infertile men have demonstrated that up to 20% carry constitutional chromosome aberrations [2–5]. Genomic aberrations found in these patients include numerical abnormalities, such as Klinefelter syndrome and its variants; XYY karyotype; testicular disorders of sex development, such as XX males; structural chromosome rearrangements, including Robertsonian translocations, balanced reciprocal translocations and inversions; as well as submicroscopic DNA copy number alterations (microdeletions and microduplications) encompassing genes associated with spermatogenesis or gonadal development.

Infertility is a genetically heterogeneous condition affecting about 10% of women of reproductive age. Genetic studies on animal models have identified thousands of candidate genes that are essential for gonadal development, germline cell differentiation, complex oocyte–granulosa intercellular signaling, gametogenesis, fertilization, and fetal development. A subset of these candidate genes derived from animal models has been found to cause ovarian dysfunction and infertility in humans.