We employed two distinct, patient-derived, CSB-deficient iPSC lines, one generated from a donor with the most severe form of CS, cerebro-oculo-fascio-skeletal syndrome (COFS), and one generated from a donor with classical CS type I and differentiated them into neural progenitor cells (NPCs), in the form of neurospheres (NS) and COs. Here, ERCC6 is linked to COFS syndrome.