To further characterize the observed microcephaly-associated phenotypes NF stage 42 drug treated X. laevis embryos were analyzed for the number of phosphohistone 3 (PH3) positive cells, a marker for actively dividing cells (Elmaci et al., 2018), in the brain as a decrease in active divisions of cells in the brain throughout development is a hallmark of microcephaly. The gene discussed is PHC3; the disease is microcephaly.