FIG. 4.

Deletional analysis of the HRC upstream region identified a conserved region required for expression in vivo. Schematic representations of the various deletion constructs of the HRC upstream region analyzed in these studies are shown in the center. Red arrow, HRC transcriptional start site; green arrow, transcriptional start site directed by the heterologous HSP68 promoter; blue arrow, lacZ translational start site; B, BamHI; N, NcoI; Bg, BglII; P, Psp1406I. Construct number and nucleotides, relative to the HRC transcriptional start site at +1, are indicated on the left. Expression of lacZ in somites, limbs, heart, and arteries is noted in the columns to the right. +++, very robust, easily detectable expression; +, very weak expression; −, a complete lack of detectable expression. The column on the far right indicates the number of independent transgenic lines or F₀ transgenic embryos that expressed lacZ in the indicated pattern as a fraction of the total number of transgene-positive F₀ embryos or lines examined. For HSP68/510-770 (construct 5), three of the five lines examined expressed lacZ in the indicated pattern. The other two F₀ transgenic embryos showed no expression of lacZ.