Emx2 expression levels in NSCs modulate astrogenesis rates by regulating EgfR and Fgf9.

Generation of astrocytes within the developing cerebral cortex is a tightly regulated process, initiating at low level in the middle of neuronogenesis and peaking up after its completion. Astrocytic outputs depend on two primary factors: progression of multipotent precursors toward the astroglial lineage and sizing of the astrogenic proliferating pool. The aim of this study was to investigate the role of the Emx2 homeobox gene in the latter process. We addressed this issue by combined gain- and loss-of-function methods, in vivo as well as in primary cultures of cortico-cerebral precursors. We found that Emx2 overexpression in cortico-cerebral stem cells shrinked the proliferating astrogenic pool, resulting in a severe reduction of the astroglial outcome. We showed that this was caused by EgfR and Fgf9 downregulation and that both phenomena originated from exaggerated Bmp signaling and Sox2 repression. Finally, we provided evidence that in vivo temporal progression of Emx2 levels in cortico-cerebral multipotent precursors contributes to confine the bulk of astrogenesis to postnatal life. Emx2 regulation of astrogenesis adds to a number of earlier developmental processes mastered by this gene. It points to Emx2 as a new promising tool for controlling reactive astrogliosis and optimizing cell-based designs for brain repair.

The doublesex homolog Dmrt5 is required for the development of the caudomedial cerebral cortex in mammals.

Regional patterning of the cerebral cortex is initiated by morphogens secreted by patterning centers that establish graded expression of transcription factors within cortical progenitors. Here, we show that Dmrt5 is expressed in cortical progenitors in a high-caudomedial to low-rostrolateral gradient. In its absence, the cortex is strongly reduced and exhibits severe abnormalities, including agenesis of the hippocampus and choroid plexus and defects in commissural and thalamocortical tracts. Loss of Dmrt5 results in decreased Wnt and Bmp in one of the major telencephalic patterning centers, the dorsomedial telencephalon, and in a reduction of Cajal-Retzius cells. Expression of the dorsal midline signaling center-dependent transcription factors is downregulated, including Emx2, which promotes caudomedial fates, while the rostral determinant Pax6, which is inhibited by midline signals, is upregulated. Consistently, Dmrt5(-/-) brains exhibit patterning defects with a dramatic reduction of the caudomedial cortex. Dmrt5 is increased upon the activation of Wnt signaling and downregulated in Gli3(xt/xt) mutants. We conclude that Dmrt5 is a novel Wnt-dependent transcription factor required for early cortical development and that it may regulate initial cortical patterning by promoting dorsal midline signaling center formation and thereby helping to establish the graded expression of the other transcription regulators of cortical identity.

Emx2 and Foxg1 inhibit gliogenesis and promote neuronogenesis.

Neural stem cells (NSCs) give rise to all cell types forming the cortex: neurons, astrocytes, and oligodendrocytes. The transition from the former to the latter ones takes place via lineage-restricted progenitors in a highly regulated way. This process is mastered by large sets of genes, among which some implicated in central nervous system pattern formation. The aim of this study was to disentangle the kinetic and histogenetic roles exerted by two of these genes, Emx2 and Foxg1, in cortico-cerebral precursors. For this purpose, we set up a new integrated in vitro assay design. Embryonic cortical progenitors were transduced with lentiviral vectors driving overexpression of Emx2 and Foxg1 in NSCs and neuronal progenitors. Cells belonging to different neuronogenic and gliogenic compartments were labeled by spectrally distinguishable fluoroproteins driven by cell type-specific promoters and by cell type-specific antibodies and were scored via multiplex cytofluorometry and immunocytofluorescence. A detailed picture of Emx2 and Foxg1 activities in cortico-cerebral histogenesis resulted from this study. Unexpectedly, we found that both genes inhibit gliogenesis and promote neuronogenesis, through distinct mechanisms, and Foxg1 also dramatically stimulates neurite outgrowth. Remarkably, such activities, alone or combined, may be exploited to ameliorate the neuronal output obtainable from neural cultures, for purposes of cell-based brain repair.

Modulation of Circulating MicroRNAs Levels during the Switch from Clopidogrel to Ticagrelor.

Background. Circulating microRNAs are appealing biomarkers to monitor several processes underlying cardiovascular diseases. Platelets are a major source for circulating microRNAs. Interestingly, the levels of specific microRNAs were reported to correlate with the level of platelet activation. The aim of the present study was to test whether the treatment with the novel antiplatelet agent, ticagrelor, is associated with modulation in the levels of key platelet-derived microRNAs. Methods and Results. Patients were randomly selected from those participating in the SHIFT-OVER study, in which we had previously evaluated the effect of the therapeutic switch from clopidogrel to ticagrelor on platelet aggregation. Circulating levels of selected microRNAs were measured before and after the therapeutic switch from a dual antiplatelet therapy including acetylsalicylic acid (ASA) and clopidogrel to the more potent ticagrelor. Interestingly, the circulating levels of miR-126 (p = 0.030), miR-223 (p = 0.044), and miR-150 (p = 0.048) were significantly reduced, while the levels of miR-96 were increased (p = 0.038). No substantial differences were observed for the remaining microRNAs. Conclusions. Switching from a dual antiplatelet treatment with clopidogrel to ticagrelor is associated with significant modulation in the circulating levels of specific microRNAs. If confirmed in larger, independent cohorts, our results pave the way for the use of circulating microRNAs as biomarkers of platelets activity in response to specific pharmacological treatments.