Fig. 5. Downregulation of transgene expression in later development. (A-C) At 11.0 dpc, the anterior boundaries and overall expression patterns of constructs CHZ (A), Cb4Z (B) and CBb4Z (C) were identical to those seen at earlier stages of development. (D-F) By 11.5 dpc, downregulation of expression had commenced in the posterior mesoderm with all three constructs (white brackets). (G-I) Downregulation was complete by 12.5 dpc. Mesodermal expression was absent from embryos carrying construct CHZ (G) and was restricted to cervical regions for constructs Cb4Z (H) and CBb4Z (I). (J-L) At 13.5 dpc, neural expression of CHZ was also downregulated (J), whereas neural and mesodermal expression was maintained by constructs Cb4Z (K) and CBb4Z (L). White arrowheads indicate drg2. Black arrowheads and arrows indicate the anterior and posterior boundaries of mesodermal expression, respectively.