In addition, expression of neuronal nitric oxygen synthase (NOS) was lower in embryos from diabetic pregnancies than in those from non-diabetic pregnancies, but in each of these conditions we found no significant differences between wild type and Alx3-deficient embryos (Fig. 3C). In contrast, maternal diabetes increased the expression of inducible NOS, but this effect was higher in Alx3-deficient than in wild type embryos (Fig. 3C). Consistent with these data, we detected increased nitrotyrosine staining in the head mesenchyme of Alx3-null embryos from diabetic pregnancies as compared to wild type embryos (Fig. 3D–F). These results suggest that the defence response against oxidative stress in the presence of high glucose levels is impaired in Alx3-deficient embryos.