TBX1 and cleft palate: Because pharyngeal arch development depends on a precise balance between Tbx1 and RA, we suspect that the cause of cleft palate in 22q11.2 deletion syndrome might be related to pharyngeal patterning defects similar to those we observe in the retinoid-deficient Rdh10flox/delta mutant embryos, which have excess Tbx1. Perhaps correlation of cleft palate and pharyngeal arch defects in other models like 22q11.2 deletion syndrome can be understood through evaluating the presence of spontaneous mouth movement in utero.