Fig. 7. Hoxa2^-/- phenotypic rescue in Hoxa2^-/-;Ptx1^-/- mutants. (A-C) Skeletal preparations of E16.5 wild-type (A), Hoxa2^-/- (B) and Hoxa2^-/-;Ptx1^-/- (C) embryos to show the tympanic ring (TR), which is duplicated (TR*) in Hoxa2^-/- and Hoxa2^-/-;Ptx1^-/- mutant embryos. (D-I) Histological analysis of the ear region of wild-type (D,G), Hoxa2^-/-(E,H) and Hoxa2^-/-;Ptx1^-/- (F,I) newborns. Wild-type and Hoxa2^-/-;Ptx1^-/- double mutants have only one EAM (arrow) reaching to the tympanic ring (TR). Hoxa2^-/- mutants have an additional EAM (arrowhead) associated with the duplicated ring (TR*). The insets in D and F show a small blind extension (arrowhead) close to the EAM. (G) The tympanic membrane is build up from the EAM (arrow), and epithelium of the middle ear cavity, which entrap the manubrium of the malleus (MM). (H) In Hoxa2^-/- embryos, the tympanic membrane is distorted by the presence of the two EAMs (arrow and arrowhead). (I) The appearance of the tympanic membrane is quite normal in Hoxa2^-/-;Ptx1^-/- mutants. (J-L) Tongue phenotype of wild-type (J), Hoxa2^-/- (K) and Hoxa2^-/-;Ptx1^-/- (L) newborns. In Hoxa2^-/- mutants, there is a medial cleft (asterisk), which is lost in the double mutant. Note that the sections are at slightly different levels with respect to the hyoid bone (Hy) to show equivalent areas of the tongue. All sections are frontal. In D-H, lateral is towards the left. (D,E) More posterior areas than G,H. At least three embryos corresponding to each genotype have been analyzed and showed similar phenotypes.