Neurog2 simultaneously activates and represses alternative gene expression programs in the developing neocortex.
Progenitor cells undergo a series of stable identity transitions on their way to becoming fully differentiated cells with unique identities. Each cellular transition requires that new sets of genes are expressed, while alternative genetic programs are concurrently repressed. Here, we investigated how the proneural gene Neurog2 simultaneously activates and represses alternative gene expression programs in the developing neocortex. By comparing the activities of transcriptional activator (Neurog2-VP16) and repressor (Neurog2-EnR) fusions to wild-type Neurog2, we first demonstrate that Neurog2 functions as an activator to both extinguish Pax6 expression in radial glial cells and initiate Tbr2 expression in intermediate neuronal progenitors. Similarly, we show that Neurog2 functions as an activator to promote the differentiation of neurons with a dorsal telencephalic (i.e., neocortical) identity and to block a ventral fate, identifying 2 Neurog2-regulated transcriptional programs involved in the latter. First, we show that the Neurog2-transcriptional target Tbr2 is a direct transcriptional repressor of the ventral gene Ebf1. Secondly, we demonstrate that Neurog2 indirectly turns off Etv1 expression, which in turn indirectly regulates the expression of the ventral proneural gene Ascl1. Neurog2 thus activates several genetic off-switches, each with distinct transcriptional targets, revealing an unappreciated level of specificity for how Neurog2 prevents inappropriate gene expression during neocortical development.
University of Calgary, Hotchkiss Brain Institute, Alberta Children's Hospital Research Institute, Health Sciences Centre, Calgary, Alberta, Canada.
Christopher
C
Kovach
Rajiv
R
Dixit
Saiqun
S
Li
Pierre
P
Mattar
Grey
G
Wilkinson
Gina E
GE
Elsen
Deborah M
DM
Kurrasch
Robert F
RF
Hevner
Carol
C
Schuurmans
D000818:Animals; D051792:Basic Helix-Loop-Helix Proteins / Q000235:genetics / Q000378:metabolism*; D004247:DNA / Q000378:metabolism; D018507:Gene Expression Regulation, Developmental; D051379:Mice; D019579:Neocortex / Q000196:embryology* / Q000378:metabolism; D009419:Nerve Tissue Proteins / Q000235:genetics / Q000378:metabolism*; D058953:Neural Stem Cells / Q000166:cytology / Q000378:metabolism*; D012097:Repressor Proteins / Q000235:genetics / Q000378:metabolism*; D015533:Transcriptional Activation
D051792:Basic Helix-Loop-Helix Proteins; D004247:DNA; D009419:Nerve Tissue Proteins; D012097:Repressor Proteins; C102938:Neurog2 protein, mouse