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Fig. 3. Isolation of regulatory sequences controlling Shh reporter
activity in the forebrain. Schematic of Bac clones 447L17 and 265M1.
Whole-genome alignments were performed using the ECR Browser with human
sequence (hg17-May'04, chr7:155395662-155783102) as the base. ECRs (>75%
similarity over a minimum of 350 bp) shared between human and mouse (pink) or
between human, mouse and chicken (green) are represented by vertical bars.
ECRs in the overlap between 447L17 and 265M1 are numbered ECR1 to ECR7.
(A) Shh mRNA expression in the head of a 10.5 dpc embryo with
accompanying transverse sections through the forebrain at the level of the (G)
hypothalamus, (M) optic vesicles and (S) telencephalon. (B-X) X-gal
staining in the forebrain of transgenic embryos carrying (B,H,N,T)
447L17ßlacZ; (C,I,O,U) 265M1ßlacZ; (D,J,P,V) ECR1/SBE2; (E,K,Q,W)
ECR3/SBE3; and (F,L,R,X) SBE4 reporter constructs at 10.5 dpc. Shh
forebrain reporter activity is divided into ventral diencephalic (SBE2, SBE4)
and ventral telencephalic (SBE3, SBE4) regulatory elements. Unlike
Shh and 447L17ßlacZ, 265M1ßlacZ transgene was not expressed
in ventricular zone (vz) of the medial ganglionic eminence (mge) (compare U
with S,T). SBE3 activity is restricted to the subventricular zone (svz) of the
mge (W). The asterisk in E indicates ectopic X-gal staining in the hindbrain.
ht, hypothalamus; ov, optic vesicle; poa, preoptic area; vz, ventricular zone;
svz, subventricular zone. The ratio of embryos exhibiting reproducible
Shh-like reporter activity over the total number of transgenic
embryos is indicated for each construct (D-F).
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