Role for Runx1 in the Proliferation and Neuronal Differentiation of Selected Progenitor Cells in the Mammalian Nervous System

Abstract

Neurogenesis requires factors that regulate the decision of dividing progenitors to leave the cell cycle and activate the neuronal differentiation program. It is shown here that the murine runt-related gene Runx1 is expressed in proliferating cells on the basal side of the olfactory epithelium. These include both Mash1ϩ olfactory receptor neuron (ORN) progenitors and NeuroDϩ ORN precursors. Disruption of Runx1 function in vivo does not cause a change in Mash1 expression but leads to a decrease in the number of NeuroDϩ neuronal precursors and an increase in differentiated ORNs. These effects result in premature and ectopic ORN differentiation. It is shown further that exogenous Runx1 expression in cultured olfactory neural progenitors causes an expansion of the mitotic cell population. In agreement with these findings, exogenous Runx1 expression also promotes cortical neural progenitor cell proliferation without inhibiting neuronal differentiation. These effects are phenocopied by a chimeric protein containing ETO, the eight twenty one transcriptional repressor, fused to the Runx1 DNA-binding domain, which suggests the involvement of transcription repression mechanisms. Consistent with this possibility, Runx1 represses transcription driven by the promoter of the cell cycle inhibitor p21Cip 1 in cortical progenitors. Together, these findings suggest a previously unrecognized role for Runx1 in coordinating the proliferation and neuronal differentiation of selected populations of neural progenitors.

Regulation of Postnatal Forebrain Amoeboid Microglial Cell Proliferation and Development by the Transcription Factor Runx1

“…Conversely, Runx1 overexpression leads to decreased numbers of mitotic microglia in vitro. Runx1 regulates cell proliferation in a variety of contexts (Theriault et al, 2005;Hoi et al, 2010;Link et al, 2010). Moreover, Runx1, as well as other Runx proteins, can coordinate cell cycle exit with the progression to a more developmentally mature state in a number of cell lineages (Kagoshima et al, 2007;Appleford and Woollard, 2009).…”

“…Purity of these cultures was confirmed by immunocytochemistry using antibodies against F4/80, Iba1, and CD11b to visualize microglia and against glial fibrillary acidic protein (GFAP) (1:1000; Sigma) to visualize astrocytes. In gain-of-function studies, adherent microglial cells were transduced with recombinant adenovirus expressing enhanced green fluorescent protein (GFP) alone or in combination with either Runx1 or Runx1(1-250), generated as previously described (Theriault et al, 2005), at the multiplicity of infection (MOI) of 50. Two days after infection, cells were fixed (2% PFA for 15 min at room temperature) and subjected to double-label immunocytochemical analysis with the following antibodies: rabbit anti-GFP (1:5000; Invitrogen), mouse anti-GFP (1:300; Novus Biologicals), mouse anti-Ki67, rabbit antiphosphorylated-histone H3 (PH3; 1:200; Millipore), or mouse antip21 Cip1 (1:200; BD Pharmingen).…”

“…HEK293 cells were transfected with the pwwp21-luc reporter plasmid (Theriault et al, 2005) and subjected to quantification of luciferase activity in the absence or presence of plasmids pCMV2-FLAG-Runx1 or pCMV2-FLAG-Runx1(1-250) (500 ng/ transfection) as described previously (Theriault et al, 2005).…”

“…Compared with the expression of GFP alone, exogenous Runx1 caused a decrease in the number of cells expressing two mitotic cell markers, Ki67 and PH3. This effect was specific because it was not observed when we used a transcriptionally incompetent form of Runx1 containing only the first 250 aa, termed Runx1(1-250) (Theriault et al, 2005) (Fig. 6Q-X ).…”

Epigenetic regulation of sensory neurogenesis in the dorsal root ganglion cell line ND7 by folic acid

“…Hes1 and other Hes genes are important for neural stem cell maintenance. 31,32 Inactivation of Hes1 accelerates early neurogenesis and decreases the number of late-born neurons. 33 Neurog2 plays a role in the acquisition levels associated with the Neurog2 promoter increased (p < 0.0001), whereas KDM6B levels decreased (p < 0.05), in the presence of FA ( Fig.…”