It is of interest to note, that a very recent single-cell RNA-Seq study of human Rb tumors and those arising from intravitreal injections of patient-specific RB1 organoids revealed a bias toward retinal progenitor cells and rods.43 The prevalence of progenitor cells following pRb inactivation both in vitro as shown in our study and in vivo suggest a role for pRb in retinal cell differentiation; however, lineage tracing studies are needed to fully address this important notion. The gene discussed is RB1; the disease is retinoblastoma.