Embryonic gonadotropin-releasing hormone signaling is necessary for maturation of the male reproductive axis

In the two following studies from the same group, the authors used an interesting and sophisticated design of genetically modified mice that express diphtheria toxin upon Cre recombination, the expression of which itself is driven by the endogenous regulatory sequences of a target gene. This strategy thereby results in specific ablation of an entire cellular population, like kisspeptin or KISS1R neurons. What is intriguing, and certainly more unexpected, is that instead of observing at least similar or even worse effects than in single gene knockout mice, the authors observed a much milder phenotype, suggesting a greater physiologic plasticity when a cell population is theoretically missing rather than a gene. Overall, these two studies bring very challenging results, which have to be cautiously interpreted and will need further confirmations.