β-catenin expression and activity in the developing thalamocortical tract at E15.5. (A) In situ hybridisation for β-catenin mRNA on coronal section of E15.5 mouse embryo (black signal). (B-E) DAB immunohistochemistry for β-catenin protein. (B) Diagram indicating boxed areas shown at high magnification in (C-E) and illustrating a thalamic cell body in the thalamus (T) with its axon growing through the prethalamus (pT) and into the internal capsule (ic) and towards the cerebral cortex (cc). Higher magnification of (C) thalamus, (D) prethalamus, and (E) internal capsule, insets show a blown-up cell body. Note that although axonal staining is strong in all areas cell body staining is relatively much stronger in the thalamus. (F) β-catenin/neurofilament double immunofluorescence on a cultured thalamic neuron with arrow indicating a growth cone. (G) LacZ histochemistry on a BAT-gal reporter embryo. Scale bars: A&G, 500 μm; C-E, 100 μm; F, 10 μm.