A, the ASPM gene codes for a 3477 aa protein with four protein domains: microtubule binding domain (light grey), CH domain (grey), calmodulin-binding IQ domains (dark grey) and the Armadillo-like domain (brown); B, the nonsense mutation p.S1601* in patients of family A and B lead to a truncated protein, which is missing the Armadillo-like domain and part of the calmodulin-binding IQ domain.