Partial rescue of TOPGAL reporter expression by GSK inhibitors in Tenm4m1/m1mutants. Shown are E7.5 embryos removed from the maternal environment, then cultured for 24 hours without addition of BIO or MeBIO (w/o), with 2, 5 or 10 μM 6-bromoindirubin-3′-oxime (BIO), or 10 μM 1-methyl-6-bromoindirubin-3′-oxime (MeBIO). The TOPGAL reporter transgene was used to assess WNT signaling by staining for β-galactosidase activity. Wildtype embryos obtained at E7.5 (A) and cultured for 24 hours (B and C) had β-galactosidase expression without or with the addition of BIO. Tenm4m1/m1 mutant embryos had no β-galactosidase expression when obtained at E7.5 (D) but expressed β-galactosidase after 24 hours in 2 μM (E) or 5 μM BIO (F). A Tenm4m1/m1 mutant embryo cultured 24 hours in 5 μM BIO, not stained for β-galactosidase to show morphological features is shown in G alongside a histological section (H) from the area in the blue box showing migrating mesodermal cells (arrowheads). A Tenm4m1/m1 mutant embryo cultured 24 hours with 10 μM BIO shows fusion of the chorion (ch) with the allantois (al) (I), also not stained with β-galactosidase. No embryos cultured with MeBIO showed evidence of mesoderm or TOPGAL activity, a representative one cultured in 10uM MeBIO is shown in (J). Bar 100 μm.