Fig. 1. dtr^–/–, yot^–/–and dtr^–/+;yot^–/+embryos have defects in body axis formation and expression of Hh target genes in the brain. (A-D) Examination of live 36-hour embryos reveals curled body axes in dtr^–/–, yot^–/–and dtr^–/+;yot^–/+mutant embryos. U-shaped somites, indicative of defects in slow muscle cell differentiation, are seen only in yot^–/–and dtr^–/+;yot^–/+embryos, dtr^–/–embryos have wild-type somites (insets). (E-H) patched 1 (ptc1) expression is generally reduced in all three genotypes. In situ labeling was performed simultaneously and embryos were developed for the same amount of time in E, F and G. Inset in H shows wild-type sibling developed in same tube as this transheterozygote. (I-L) In all gli mutant embryos, nk2.2 expression is reduced or absent from the anterior pituitary anlage (arrowheads), as well as from different regions of the ventral midbrain and ventral hindbrain. (M-P) Expression of pax6, a gene known to be repressed by Hh signaling, is variably expanded in the MDB (arrowhead) and hindbrain (arrows). Expression of pax6 is expanded across the MDB expression domain of shh (not shown), ptc (E), and nk2.2 (I). All panels show lateral views, anterior to the left. Eyes were removed in E-P. Gene expression is indicated on the left. Di, diencephalon; HB, hindbrain; MB, midbrain; MDB, mid-diencephalon boundary; MHB, midbrain-hindbrain boundary; te, telencephalon.

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