Fig. 1. Expression pattern of the Hoxa7-Gcm1 transgene. (A) A diagrammatic representation of the two transgenes used in this work (see Materials and Methods for details). A cDNA fragment containing the entire coding sequence of Gcm1 (1.6 kb) is under the control of the 470-bp enhancer element of the mouse Hoxa7 gene and thymidine kinase minimal promoter (TK). SV40 polyadenylation signal sequences terminate the transgene transcript. In a separate transgene, the E. coli lacZ gene replaces the Gcm1 gene. (B) Northern blot of poly(A)-selected RNA from E9.5 wild-type and double transgenic embryos were probed for Gcm1. Expression of the Gcm1 transgene was confirmed by the detection of 1.8 kb band corresponding to the predicted size of the transgene transcript. (C-E) Lateral views of a E9.5 wild-type embryo (C), a E9.5 transgenic embryo (D) and a E10.5 transgenic embryo (E) stained for ß-galactosidase activity. The expression domain of the transgene is restricted to the caudal part of the embryo with an anterior boundary at the level of somite 18-20. At E9.5, note the enlargement of the posterior neuropore in the transgenic embryo as compared to the small oval shape of the posterior neuropore in wild type (arrow in C,D).

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