PTPA and Greig cephalopolysyndactyly syndrome: Interestingly, some GCPS point mutations and a mutation in a patient with acrocallosal syndrome are located in the identified MID1-α4-PP2A complex-dependent regulation domain of GLI3 [A943P (as found in one patient with acrocallosal syndrome [15]), I808M [11] and P707S [17] (as found in GCPS patients)].