Fig. 2. Characterisation of the Emx2 enhancer activity in the forebrain. (A) In situ hybridisation analysis of Emx2 expression in the telencephalon of E10.5 wild-type mice. (B) lacZ staining of a transgenic embryo carrying the mouse Emx2 enhancer (construct 2). (C) Emx2 enhancer activity in the forebrain of an homozygous Xt^J embryo. lacZ expression in the dorsomedial telencephalon (t) is abolished (arrow), while expression in the cortical neuroepithelium occurs at lower levels than in wild-type embryos. lacZ expression in the diencephalon (d) remains unaffected. (D-F) Time course analysis of enhancer activity in the forebrain at (D) the 12-somite stage, (E) E10.5 and (F) E11.5. (D) Start of lacZ expression in the dorsal forebrain. (E) Expression of the reporter gene is observed in the dorsal part of the telencephalic vesicles with highest expression levels in the caudal telencephalon. (F) At E11.5, the reporter gene is expressed in a gradient with highest expression levels in the medial-caudal telencephalon (arrows). lacZ expression in the developing heart as seen in B-F is specific for the transgenic line shown.