Redundancy in the central tachykinin systems safeguards puberty onset and fertility
The tachykinin neurokinin B (NKB, Tac2) is critical for GnRH release. NKB signaling deficiency leads to infertility in humans. However, some patients reverse this hypogonadism resembling the fertile phenotype of Tac2KO and Tacr3KO (encoding NKB receptor, NK3R) mice despite the absence of NKB signaling. Here, we demonstrate that in the absence of NKB signaling, other tachykinins (substance P and neurokinin A [NKA], encoded by Tac1) may take over to preserve fertility. The complete absence of tachykinins in Tac1/Tac2KO mice leads to delayed puberty onset in both sexes and infertility in 80% of females (but not males), in contrast to the 100% fertile phenotype of Tac1KO and Tac2KO mice separately. Furthermore, we demonstrate that NKA controls puberty onset and LH release through NKB-independent mechanisms in the presence of sex steroids and NKB-dependent mechanisms in their absence. In summary, tachykinins interact in a coordinated manner to ensure reproductive success in female mice.