Fig. 3: Overexpression of septa-related gene, Smad7, recapitulates gene expression and morphology changes seen in Celsr3 cKO barrel cortex.

TGF-β family members display specific expression of receptors (a) and ligands (b) within the barrel thalamocortical pathway. c Inhibitor of TGF-β signaling, Smad7, is expressed in barrel cortex in a septa-related pattern. d Smad7 is upregulated in L4 of Celsr3cKO S1 cortex. e Smad7/EYFP overexpression (Smad7^OE) leads to downregulation of hollow-related genes (Btbd3), and upregulation of septa-related genes (Nrxn2 and Sorl1). Images are from a representative electroporated brain (P7) with RNA ISH for the indicated genes performed on serial sections. The extent of transfection is indicated by red arrowheads. Gene expression within electroporated areas (IUE) are outlined in green, while the un-electroporated barrel cortex (cont) is outlined in orange. f Quantification of expression changes in Smad7^OE brains. Log₂FoldChange was calculated for L4 expression intensity of indicated genes in the IUE vs Cont hemisphere. Displayed are group means ± SEM. Astn2: n = 3; Btbd3: n = 16; Cadps2: n = 4; Cdh8; n = 3; Nrxn2: n = 3; Sorl1: n = 3 brains. g Morphology of L4 Smad7^OE neurons which were sparsely transfected with Cre-dependent Smad7/EYFP (LSL=LoxP-STOP-LoxP). A prominent apical dendrite (asterisk) was found on most Smad7^OE neurons (arrowheads). In some images, arrows indicate the path of the apical dendrite. h Quantification of spiny stellate versus pyramidal neuron morphology in sparsely labeled Smad7^OE neurons in L4, compared to control overexpression. Asterisks indicate ***p = 0.0002, generalized linear mixed-effects model with parametric bootstrap test (n = 158 neurons from 19 control brains, n = 62 neurons from 5 Smad7^OE brains). Scale bars, 1 mm (yellow) and 100 µm (white). Source data are provided as a Source data file.