We next searched the Human Phenotype Ontology website for genes associated with microcephaly or cerebellar hypoplasia (ontology terms HP:0000252 and HP:0007360) and found that, out of a list of 1430 genes, 474 candidates were downregulated at least 1.5 times upon murine BMC differentiation, including 404 reported to be downregulated upon p53 activation (Fig. S6, Table S23). Here, TP53 is linked to microcephaly.