Fig. 5: Stabilizing β-CATENIN selectively in the specified ChPe using FoxJ1Cre causes loss of ChPe fate but not transformation to a neuronal fate.

a A cartoon illustrating the hem (cyan asterisks), choroid plaque (white asterisks), and choroid plexus at E10.5 and E12.5. b Foxj1Cre::Ai9 marks differentiated choroid plexus at E12.5 but not the choroid plaque at E10.5 or the hem at either stage. Lmx1aCre::Ai9 marks both hem and choroid plexus/plaque starting from E10.5. Boxed regions (b) are shown at high magnification in the adjacent panels. Representative images are shown of sections taken from N = 3 brains (biologically independent replicates) examined over 2 independent experiments. c–e In E16.5 Foxj1Cre::β-cat GOF embryos, LEF1 levels increase (color key: dark blue indicates grey value =0, white indicates grey value =255), while bonafide ChPe markers AQP1(Boxed regions (c) are shown as high magnification insets), TTR, and OTX2 decrease compared with controls, as seen using (c) immunofluorescence and (d) quantification of the number cells positive for each ChPe marker as a fraction of the Ai9-positive cells. A scatter plot shows that in the E16.5 control ChPe, 100% of 500 Ai9+ cells are also OTX2 + , 98.25% of 942 Ai9+ cells are also AQP1 + , and 98.47% of 1168 Ai9+ cells are also TTR + . In Foxj1Cre::β-cat GOF ChP, 91.6% of 731 Ai9+ cells are also OTX2 + , 33.3% of 781 Ai9+ cells are also AQP1 + , and 47% of 1097 Ai9+ cells are also TTR + . (c, d) N = 5 (OTX2) and N = 6 (AQP1 and TTR) brains (biologically independent replicates) for each genotype examined over 3 independent experiments. Bars represent mean ± SEM; p = 0.088919 (OTX2), p = 0.000129 (AQP1), p = 0.000783 (TTR). (e) A violin plot reveals that the nuclear intensity of OTX2 labeling decreases significantly in Foxj1Cre::β-cat GOF ChPe cells compared with controls. n = 536 nuclei from control and 590 nuclei from Foxj1Cre::β-cat GOF ChPe; N = 5 brains (biologically independent replicates) examined over 3 independent experiments; solid black line represents median and dotted lines represents quartiles; statistical test: two-tailed unpaired multiple Student’s t test with unequal variance; p < 0.0001; *p < 0.05; **p < 0.01; ***p < 0.001; ns if p value > 0.05. f In control and Foxj1Cre::β-cat GOF brains, PROX1 immunostaining is seen in the dentate gyrus, PAX6 and TBR2 appear in the telencephalic ventricular and sub-ventricular zones, respectively, and βIII-TUBULIN is present in postmitotic neurons in the dorsal telencephalon. None of these markers appear in the ChPe of either genotype (solid lines), except for a few βIII-TUBULIN positive neurons that normally populate the ChPe. Boxed regions (f) are shown at high magnification in the adjacent panels. Representative images are shown of sections taken from N = 3 brains (biologically independent replicates) examined over 2 independent experiments. Scale bars: 100 μm (all panels in b, c, and f); 10 μm (all panel in c inset). Source data are provided as a Source Data file.