Microglia are involved in a widespread set of physiological and pathological processes and further
play important roles during neurodevelopmental events. Postnatal maturation of microglia has
been associated with the establishment of microglia-specific gene expression patterns. The mechanisms
governing microglia maturation are only partially understood but Tgfb1 has been suggested
to be one important mediator. In the present study, we demonstrate that early postnatal microglia
maturation is associated with alternative microglia activation, increased engulfment of apoptotic
cells as well as activated microglial Tgfb signaling. Interestingly, microglial Tgfb signaling preceded the induction of the microglia-specific gene expression indicating the importance of Tgfb1 for postnatal microglia maturation. Moreover, we provide evidence that Tgfb1 is expressed by
neurons in postnatal and adult brains defining neuron-microglia communication via Tgfb1 as an
important event. Finally, we introduce the recently identified microglia marker Tmem119 as a
direct Tgfb1-Smad2 target gene. Taken together, the data presented here further increase the
understanding of Tgfb1-mediated effects in microglia and place emphasis on the importance of
Tgfb1 for microglia maturation and maintenance