GCNA and osteocraniostenosis: Human diseases have been associated with defective DNA–protein cross-link proteases (6), e.g., gracile bone dysplasia (GCLEB) and Kenny–Caffey syndrome type 2 are linked to mutations in FAM111A (65, 66), pediatric germ cell tumors have been associated with mutations in GCNA (60), and Ruijs–Aalfs syndrome has been linked to mutations in SPRTN (67, 68).