Oligodendrocytes Provide Antioxidant Defense Function for Neurons by Secreting Ferritin Heavy Chain.

An evolutionarily conserved function of glia is to provide metabolic and structural support for neurons. To identify molecules generated by glia and with vital functions for neurons, we used Drosophila melanogaster as a screening tool, and subsequently translated the findings to mice. We found that a cargo receptor operating in the secretory pathway of glia was essential to maintain axonal integrity by regulating iron buffering. Ferritin heavy chain was identified as the critical secretory cargo, required for the protection against iron-mediated ferroptotic axonal damage. In mice, ferritin heavy chain is highly expressed by oligodendrocytes and secreted by employing an unconventional secretion pathway involving extracellular vesicles. Disrupting the release of extracellular vesicles or the expression of ferritin heavy chain in oligodendrocytes causes neuronal loss and oxidative damage in mice. Our data point to a role of oligodendrocytes in providing an antioxidant defense system to support neurons against iron-mediated cytotoxicity.

Calcium activation of the LMO4 transcription complex and its role in the patterning of thalamocortical connections.

Lasting changes in neuronal connectivity require calcium-dependent gene expression. Here we report the identification of LIM domain-only 4 (LMO4) as a mediator of calcium-dependent transcription in cortical neurons. Calcium influx via voltage-sensitive calcium channels and NMDA receptors contributes to synaptically induced LMO4-mediated transactivation. LMO4-mediated transcription is dependent on signaling via calcium/calmodulin-dependent protein (CaM) kinase IV and microtubule-associated protein (MAP) kinase downstream of synaptic stimulation. Coimmunoprecipitation experiments indicate that LMO4 can form a complex with cAMP response element-binding protein (CREB) and can interact with cofactor of LIM homeodomain protein 1 (CLIM1) and CLIM2. To evaluate the role of LMO4 in vivo, we examined the consequences of conditional loss of lmo4 in the forebrain, using the Cre-Lox gene-targeting strategy. The organization of the barrel field in somatosensory cortex is disrupted in mice in which lmo4 is deleted conditionally in the cortex. Specifically, in contrast to controls, thalamocortical afferents in conditional lmo4 null mice fail to segregate into distinct barrel-specific domains. These observations identify LMO4 as a calcium-dependent transactivator that plays a key role in patterning thalamocortical connections during development.