Our analysis of the single-cell RNA-seq data from the human cortex indicates that excitatory neurons from layers 3 and 5 express PSG more than expected, including BRCA1 and several of its binding partners associated with DNA damage response and microcephaly, such as TOP3A, RNF168, and NHEJ1. Further analyses on the role of these genes, which are currently known for their DNA damage response, might shed some light on primate brain evolution. The gene discussed is TOP3A; the disease is microcephaly.