The successful generation of expandable CXCR4+ NPCs lines from the parental control iPSCs and one iPSC from each of the BD-affected sons within the Family-811 quartet afforded the opportunity, for the first time, to characterize the molecular and cellular phenotypes in a defined CNS progenitor cell (i.e. CXCR4+) and post-mitotic neurons derived from them upon neural differentiation. Initially, using bromo-deoxyuridine (BrdU) incorporation into DNA to measure cell proliferation, we observed a proliferation deficit in both of the BD patient NPCs compared to the unaffected parental NPCs (Fig. 3A, B) (t-test, p=0.001). In addition to this proliferation defect, both BD-patient NPCs produced qualitatively fewer βIII-tubulin (Tuj1+) neurons than the unaffected NPCs over a six week differentiation time course (Fig. 3C). Taken together, these observations, and the difficulty encountered in generating CXCR4+ NPCs from neural rosettes by FACS, collectively provided initial evidence for a neural differentiation deficit phenotype in both BD-patient NPCs from the Family-811 quartet that ultimately negatively impacts ex vivo neurogenesis.
