These authors have equally contribute to the work. AbstractNeuronal survival and morphological maturation depends on the action of the transcription factor calcium responsive element binding protein (CREB), which regulates expression of several target genes in an activity-dependent manner. However, it remains largely unknown whether CREB-mediated transcription could play a role at early stages of neuronal differentiation, prior to the establishment of functional synaptic contacts. Here, we show that CREB is phosphorylated at very early stages of neuronal differentiation in vivo and in vitro, even in the absence of depolarizing agents. Using genetic tools, we also show that inhibition of CREB-signaling affects neuronal growth and survival in vitro without affecting cell proliferation and neurogenesis. Expression of A-CREB or M-CREB, 2 dominant-negative inhibitors of CREB, decreases cell survival and the complexity of neuronal arborization. Similar changes are observed in neurons treated with protein kinase A (PKA) and Ca 2+ /calmodulin-dependent protein kinase II (CaMKII) inhibitors, which also show decreased levels of pCREBSer133. Notably, expression of CREB-FY, a Tyr134Phe CREB mutant with a lower Km for phosphorylation, partly rescues the effects of PKA and CaMKII inhibition. Our data indicate that CREB-mediated signaling play important roles at early stages of cortical neuron differentiation, prior to the establishment of fully functional synaptic contacts.

Hitherto, the known mechanisms underpinning cell-fate specification act on neural progenitors, affecting their commitment to generate neuron or glial cells. Here, we show that particular phospholipids supplemented in the culture media modify the commitment of post-mitotic neural cells in vitro. Phosphatidylcholine (PtdCho)-enriched media enhances neuronal differentiation at the expense of astroglial and unspecified cells. Conversely, phosphatidylethanolamine (PtdEtn) enhances astroglial differentiation and accelerates astrocyte maturation. The ability of phospholipids to modify the fate of post-mitotic cells depends on its presence during a narrow time-window during cell differentiation and it is mediated by the selective activation of particular signaling pathways. While PtdCho-mediated effect on neuronal differentiation depends on cAMP-dependent kinase (PKA)/calcium responsive element binding protein (CREB), PtdEtn stimulates astrogliogenesis through the activation of the MEK/ERK signaling pathway. Collectively, our results provide an additional degree of plasticity in neural cell specification and further support the notion that cell differentiation is a reversible phenomenon. They also contribute to our understanding of neuronal and glial lineage specification in the central nervous system, opening up new avenues to retrieve neurogenic capacity in the brain.

The original version of this Article contained a typographical error in the spelling of the author Marcelo Einicker-Lamas, which was incorrectly given as Marcelo Einiker-Lamas. This has now been corrected in the PDF and HTML versions of the Article, and in the accompanying Supplementary Information file.