Figure 3

Impaired regional restriction of gene expression in huntingtin deficient embryos. X-gal staining of Nodal-LacZ embryos shows staining in endoderm near the node of normal embryos (A,C) but broad staining in mutant embryos (B, D), although expression is higher in the posterior. The tight node expression of Nodal in normal embryos (C) is lost in mutant embryos (D), consistent with the loss of a morphological node in the absence of huntingtin. Whole mount and in situ hybridization of E7.5 day embryos reveals that Fgf8 is detected in the proximal streak and is downregulated in cells migrating out of the streak in normal embryos (E,G). In contrast, Fgf8 remains highly expressed in mutant embryos (F,H). Transient expression of Gsc in the definitive endoderm overlying the prospective head region in normal embryos (I,K) is distinguished in other cell layers in normal embryos but remains unrestricted in mutant embryos (J,L). Earlier posterior expression of Gsc is also maintained in mutant embryos (J) while it is down-regulated in normal embryos (I). Embryos (A,B,E,F,G,H,I,K,L) are shown in a lateral view with anterior oriented to the left. Embryos (C,D) are in a posterior view.