Maternal Brain TNF-α Programs Innate Fear in the Offspring

Tumor necrosis factor alpha (TNF-α) is a cytokine that not only coordinates local and systemic immune responses [1, 2] but also regulates neuronal functions. Most prominently, glia-derived TNF-α has been shown to regulate homeostatic synaptic scaling [3-6], but TNF-α-null mice exhibited no apparent cognitive or emotional abnormalities. Instead, we found a TNF-α-dependent intergenerational effect, as mothers with a deficit in TNF-α programmed their offspring to exhibit low innate fear. Cross-fostering and conditional knockout experiments indicated that a TNF-α deficit in the maternal brain, rather than in the hematopoietic system, and during gestation was responsible for the low-fear offspring phenotype. The level of innate fear governs the balance between exploration/foraging and avoidance of predators and is thus fundamentally important in adaptation, fitness, and survival [7]. Because maternal exercise and activity are known to reduce both brain TNF-α [8] and offspring innate fear [9], whereas maternal stress has been reported to increase brain TNF-α [10] and offspring fear and anxiety [11, 12], maternal brain TNF-α may report environmental conditions to promote offspring behavioral adaptation to their anticipated postnatal environment.