In diabetic gestations, a proportion of wild type embryos exhibited caudal malformations consisting of tail flexion defects (Table 2 and Fig. 2A,B), but no cranial malformations were observed. In the case of Alx3 +/− embryos, maternal diabetes increased the number of embryos with craniofacial malformations (Table 2, superscript a; and Fig. 2D and E). We also found caudal malformations affecting the tail in a similar proportion to those found in wild type embryos from diabetic mothers (Table 2). The incidence of craniofacial malformations found in Alx3+/− embryos was not significantly affected by the genotype of the dams: 6.77% (n = 59) from crossings between wild type females and Alx3−/− males, and 8.03% (n = 112) from crossings between Alx3−/− females and wild type males.Figure 2Malformations observed in embryos from diabetic pregnancies after 10.5 days of gestation. (A,B) Examples of caudal malformations observed in wild type embryos from diabetic pregnancies. Tail flexion defects are indicated by arrowheads. (D,E) Examples of cranial malformations observed in heterozygote Alx3-deficient embryos from diabetic pregnancies. These include defects of the rostral mesenchyme affecting midline closure at the level of the forehead (D, arrowheads), defects at the level of the mesencephalic vesicles (D, arrows) and defects of facial mesenchyme expansion (E, arrowheads) affecting the development of the telencephalic vesicles (E, arrows). (G,H) Examples of severe malformations found in Alx3-null embryos developing in diabetic mothers. Malformations affected several embryonic regions including the forehead mesenchyme, the branchial arches and the cranial neural tube (G), or were restricted to severe craniofacial and cranial neural tube closure defects (H, arrows). Arrowheads indicate open neural folds. (C,F and I) depict normal wild type embryos for comparisons. Scale bars represent 1 mm in all cases except in G (1.5 mm). Abbreviations: ba, Branchial arches; FLB, Forelimb bud; HLB, Hind limb bud; m, Mesencephalon; r, Rhombencephalon; t, Telencephalic vesicles.