Previous studies have shown no detectable levels of MDM2 in retinoblastoma cells; however, our single cell RNA-Seq studies indicate low MDM2 and high MDM4 expression in all the Rb cone clusters, corroborating previously published data32 indicating overexpression of MDM4 in some of the Rb tumors at both mRNA and protein level. This evidence concerns the gene MDM4 and retinoblastoma.