(A, B) Immunofluorescence on coronal E10.5 embryo sections for the endothelial marker, Endomucin (Endo). Endo staining is present in wild type (A) and Hes1−/− embryos with aplastic/non-patent 4th PAAs (arrow in B). (C, D) Immunofluorescence on coronal E11.5 embryo sections for α-SMA. Strong α-SMA expression surrounding the 3 rd, 4th and 6th PAA in wild types (C) is lost in the hypo/aplastic left 3 rd and 4th PAA (red and white arrows in D, respectively) of Hes1−/− mutant embryos. Hes1 expression is reduced in Tbx1 cells and is required for the development of structures affected in 22q11 deletion syndrome: van Bueren KL, Papangeli I, Rochais F, Pearce K, Roberts C, Calmont A, Szumska D, Kelly RG, Bhattacharya S, Scambler PJ - Developmental biology (2010). Not altered. CC.