Commentary What Signals Testis Descent?

Proper migration of the testes, from their original position adjacent to the kidneys to their final location within the scrotum, constitutes a normal and obligatory step of the male sex differentiation process. In humans and other mammals, the developing testis is connected to the abdominal wall by the cranial suspensory ligament and the gubernaculum. A peptide hormone called insulin-like 3 (INSL3) was found to be a master regulator of gonadal positioning in mammals by controlling gubernacular growth [1], but key questions remained. How does INSL3 do it? What pathways are activated by this hormone? In this issue of Biology of Reproduction, Johnson et al. [2] have achieved an important advance in our understandings of testis descent by identifying several pathways activated by INSL3 in the gubernaculum. Theories Behind Testis Descen