Fig. 1. lacZ expression correctly reflects the activity of the endogenous Pax6 promoter in the proliferative neuroepithelium in the Pax6^-/- mice. (A,B) Whole-mount in situ hybridization analysis for Pax6 (A) and ß-gal (B) staining of E12.5 wild-type (+/+) and heterozygous (+/-) transgenic embryos show similar distribution of the signal in the developing CNS and eye. (C-E) The in situ hybridization analysis with probes for Pax6 (C) or lacZ (D,E) genes in wild-type (C) and heterozygous (D) and homozygous (E) transgenic forebrains, reveals similar expression pattern confined to the proliferative neuroepithelium of the dorsal telencephalon. (F-H) At stage E15.5, similar expression is seen for Pax6 in differentiating nuclei of ventral thalamus by the in situ probes for Pax6 (F) or lacZ (G) in the wild-type and heterozygous embryos, respectively. (H) In homozygous embryos, the differentiation of the ventral thalamic nuclei as revealed by the lacZ expression pattern fails. dt, dorsal thalamus; vt, ventral thalamus; ctx, cortex; ge, ganglionic eminence; nc, nasal cavity; e, eye; T, telencephalon; M, mesencephalon; sc, spinal cord. Scale bars: 1 mm in A,B; 200 µm in C-E; 500 µm in F-H.