1. Figure 4. Compensatory upregulation of Ldb1 in Ldb2-deficient layer 5 neurons. (A–D) Immunocytochemical analysis of Ldb1 expression at P4 reveals striking upregulation of Ldb1 in layer 5 of Ldb2-KO neocortex (arrow in B) compared with control (A). Neocortex-specific loss of Ldb1 protein in pyramidal neurons of Ldb1-KO (C) and Ldb1/2-DKO (D). Remaining striatal expression of Ldb1 (arrows in C,D) confirms the specificity of the Emx1-Cre-dependent recombination. (E–H) In situ hybridization for Ldb2 confirms loss of Ldb2 mRNA in Ldb2-KO (F) and Ldb1/2-DKO (H), but no change in Ldb2 expression in Ldb1-KO (G) compared with control (E). (I–J′) High-power confocal analysis of layer 5 (boxed areas in A,B) confirms compensatory upregulation of Ldb1 (green in I–J′) in Ldb2-deficient Ctip2⁺ layer 5 neurons (red in J): In controls, Ctip2⁺ layer 5 neurons do not express Ldb1 (I,I′). Strikingly, in Ldb2-KO, almost all Ctip2⁺ neurons are coexpressing Ldb1 (yellow cells in J), including the large nucleated CSMN neurons (arrows in J,J′). A few Ctip2⁺ neurons are detected that do not express Ldb1 (arrows in J; appearing red in J); however, all of them appear to have small nuclei. (K) Quantification of the absolute number of Ctip2⁺ neurons across genotypes at P4. A statistically significant decrease in the number of Ctip2⁺ neurons was found in Ldb1-KO and Ldb1/2-DKO compared with controls; however, Ldb1/2-DKO do not show any further reduction from Ldb1-KO. *P ≤ Scale bars: 500 µm in (H) for (A–H); 50 µm in (J′) for (I–J′).
From: Compensatory Actions of Ldb Adaptor Proteins During Corticospinal Motor Neuron Differentiation
Cereb Cortex. 2016;27(2): doi: /cercor/bhw003
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