AP4B1 and hereditary spastic paraplegia: hiPSCs from patients with AP-4-HSP due to bi-allelic loss-of-function variants in AP4M1 (NM_004722.4: c.916C>T (p.Arg306Ter) / c.694dupG (p.Glu232GlyfsTer21)) and AP4B1 (NM_001253852.3: c.1160_1161del (p.Thr387ArgfsTer30) / c.1345A>T (p.Arg449Ter)) were generated35,36 and differentiated into glutamatergic cortical neurons using established protocols15,37,38.