Shuhui Lima,b, Akshay Bhingec, Sara Bragado Alonsod, Irene Aksoyc,
Julieta Apread, Chit Fang Cheoke,f, Federico Calegarid, Lawrence W. Stantonc,
a Institute of Molecular and Cell Biology (IMCB), A*STAR (Agency for Science, Technology and Research),
Singapore, Republic of Singapore
b Lee Kong Chian School of Medicine, Nanyang Technological
University, Singapore, Republic of Singapore
c Stem Cell and Developmental Biology, Genome Institute of Singapore, Singapore, Republic of Singapore
d Republic of Singaporec; DFG-Research Center for Regenerative Therapies, Cluster of Excellence,
TU-Dresden, Dresden, Germany
e IFOM-p53 Joint Research Laboratory, Singapore,
Republic of Singapore
f National University of Singapore, Department of Biochemistry, Singapore
Published in Molecular and Cellular Biology Vol.37 in August 2017.
Sox2 is known to be important for neuron formation but the precise mechanism through which it activates a neurogenic program and how this differs from its well-established function in self-renewal of stem cells remain elusive. Here, we identify a highly conserved Cdk phosphorylation site on serine 39 (S39) in Sox2. In neural stem cells (NSCs), phosphorylation of S39 enhances the ability of Sox2 to negatively regulate neuronal differentiation, while loss of phosphorylation is necessary for chromatin retention of a truncated form of Sox2 generated during neurogenesis. We further demonstrate that non-phosphorylated cleaved Sox2 specifically induces the expression of proneural genes and promotes neurogenic commitment in vivo. Our present study sheds light on how the level of Cdk kinase activity directly regulates Sox2 to tip the balance between self-renewal and differentiation in NSCs.
Figure legend: (G-I) Representative fluorescent images from in vivo mouse brain electroporation of control (G, RFP), Sox21-113-S39A (H), and Sox21-113-WT (I) expression vectors. An RFP construct (RFPnls) was co-injected to identify cells that have taken up the plasmids (red). Tbr2 staining (white) was included so that boundaries can be drawn between the ventricular zone (VZ), subventricular zone (SVZ), intermediate zone (IZ), and cortical plate (CP). Nuclei were counterstained with DAPI (blue) in the merged image. Scale bar represents 25 μm in all panels.
(J) Quantification of RFPnls+ Tbr2– cells in the VZ (AP), RFPnls+ Tbr2+ cells in the VZ or SVZ (BP), and RFPnls+ Tbr2– cells in the SVZ, IZ or CP (N), as in (G-I). Full circles denote control (RFPnls), red squares Sox21-113-WT, and green triangles denote the fragment Sox21-113-S39A (n = 3 – 4). AP, apical progenitors; BP, basal progenitors; N, neurons.
For more information on Philipp Kaldis's lab, please click here.