TBX1 and 22q11.2 deletion syndrome: Tbx1 was detected only at an early embryonic stage (E10) in the rhombic lip, a unique progenitor zone that gives rise to excitatory neurons in the cerebellum130 Given that only the PF/F but no other cerebellar lobules (Crus I, Crus II, Vermis) is affected in 22q11DS and Tbx1+/– mice, we deduce that Tbx1 haploinsufficiency may not directly affect PF development.