Uncovering the molecular mechanisms of TGFβ-signalling-mediated regulation of postnatal microglia maturation and activation

• Applicant: Professor Dr. Björn Spittau
• Subject Area: Molecular Biology and Physiology of Neurons and Glial Cells
• Term: since 2015
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 278546913

The aim of the current project proposal is to decipher the molecular mechanisms underlying the TGFβ-signalling-mediated regulation of postnatal microglia maturation and activation in vivo. During the recent funding period, we have successfully generated microglia-specific mutant mouse lines to target Tgfbr2, Smad4, as well as Tgfβ1 and have clearly demonstrated that Tgfbr2 is essential to inhibit microglial activation but seems to be dispensable for microglia survival and maintenance in adult mice. We further described postnatal day 7 (P7) as the time point for the onset of TGFβ-signalling activated by neuron-derived TGFβ1 during induction of the microglia-specific gene expression signature involving genes such as Lrrc3, Tmem119, Tgfbr1, Olfml3, Hexb, Fcrls, Mafb, Gpr34, and SiglecH. In the current proposal, we aim to address how early postnatal silencing of microglial TGFβ signalling affects microglia maturation and the subsequent maturation-dependent establishment of the microglia-specific gene expression signature in vivo. Moreover, the effects of impaired microglia maturation on postnatal development and maturation of functional CNS systems will be analysed. Special attention will be given on the establishment of neuronal networks, postnatal myelination and the development and maintenance of synaptic connections in mice with silenced microglial TGFβ-signalling. Furthermore, the effects of lack of TGFβ1-mediated regulation of microglia activation will be characterised under physiological aging conditions. Based on the previous validation of Olfml3 and Tmem119 as TGFβ1-induced Smad2 target genes in microglia, additional identification and validation of Smad2/Smad4 target genes in premature and adult microglia using ChIP-seq as well as the chromatin accessibility of microglia-specific genes employing ATAC-seq will be performed. Moreover, Smad2/Smad4 interactions and subcellular localisations during TGFβ-signalling transduction will be evaluated in order to demonstrate whether Smad4 is necessary for TGFβ1-mediated effects in microglia. Taken together, the current project will elucidate the molecular mechanisms of TGFβ1-induced microglia maturation and regulation of microglia activation.

• DFG Programme: Research Grants