Figure 1. OL differentiation defects in the brain of Tcf7l2ΔHMG mice lacking the DNA-binding HMG domain.

(a) Schematic diagram shows domains in Tcf7l2 (upper) and Cre-mediated excision (lower) of the floxed exon 11, which encodes the DNA-binding HMG domain. NLS: Nuclear localization sequence. (b) Upper panel, expression of Tcf7l2 exon 11 in the mRNAs of OPCs isolated from control (Ctrl) and Tcf7l2ΔHMG brains at P2 was assayed by qRT–PCR (n=3 animals per genotype). Lower panel: western blot analysis of the spinal cords from control and Tcf7l2ΔHMG mice at P10 with anti-Tcf7l2 (amino-terminal epitope) and glyceraldehydes 3-phosphate dehydrogenase (GAPDH; loading control). (c) Expression of Mbp and Plp1 in cortices from control and Tcf7l2ΔHMG mice by in situ hybridization. Arrows indicate the cerebral white matter in coronal sections, except P60 Mbp in sagittal sections. (d) MBP immunostaining in the cortices from control and Tcf7l2ΔHMG mice at P14 assayed by immunohistochemistry. (e) Expression of membrane-anchored enhanced GFP (EGFP) driven by a CNP promoter in the cortices from control and Tcf7l2ΔHMG mice carrying the CNP-mGFP transgene at P14. (f) Quantification of Plp1⁺ OLs (per mm²) in the cortex of control and Tcf7l2ΔHMG at P60; n=3 animals per genotype. (g) The cortices of Ctrl and Tcf7l2ΔHMG mice at P14 were immunostained with anti-PDGFRα antibody. (h) PDGFRα⁺ OPC numbers were quantified per mm²; n=3 animals per genotype. (i) BrdU incorporation in the cortex of control and Tcf7l2ΔHMG mice carrying PDGFRα-GFP reporter and pulse labelled with BrdU for 2 h at P14. (j) BrdU⁺/PDGFRα⁺ OPC cell numbers were quantified per mm²; n=3 animals per genotype. (k,l) Electron microscopy of the optic nerves (OP) and corpus callosum (CC) of control and Tcf7l2ΔHMG mice at P14 and P60. (m) The percentages of myelinated axons in the OP and CC at P14 and P60; n=3 animals per genotype. Data are presented as mean±s.e.m. ***P<0.001; Student's t-test. Scale bars, 100 μm (c,d), 50 μm (e,g–j) and 2 μm (k,l).