GSE173447
RB1 depleted pluripotent stem cell retinal organoids recapitulate state cell transitions of retinoblastoma development
Retinoblastoma (Rb) is a childhood cancer of the developing retina that begins in utero in response to bi-allelic inactivation of RB1 or MYCN amplification, accounting for up to 1% of all tumours in infancy. To gain insights into the transcriptional events of each state cell transition during Rb development, we developed two Rb models via retinal organoid differentiation of RB1 depleted human embryonic stem cell line (RB1-null hESCs) and RB1patient-specific induced pluripotent (iPSC) line harbouring RB1 biallelic mutation (c.2082delC). Both models were characterised by RB1 depletion and a significant increase in the fraction of proliferating cone precursors (RXR?+Ki67+), which were defined as cell of origin for Rb by the single cell RNA-Seq analysis. The RB1 depleted retinal organoids displayed similar features to Rb tumours including mitochondrial cristae aberration and rosette-like structures and were able to undergo cell growth in an anchorage-independent manner, indicative of cell transformation in vitro. The patient-specific iPSC model displayed an enhanced reduction of amacrine, horizontal and retinal ganglion cells and an accelerated loss of cone photoreceptor markers during transition towards retinoma and Rb, compared to RB1-null hESC. In both models, the Rb cells of origin, intermediate retinoma and/or Rb cells expressed retinal ganglion and horizontal cell in addition to cone markers, a novel finding, which should help to better identify and eradicate these cells within the tumour mass. Application of Melphalan, Topotecan and TW-37 led to a significant reduction in the fraction of proliferating cone precursors, validating the suitability of these in vitro models for testing novel therapeutics for Rb. Overall design: Study of two Rb models developed via retinal organoid differentiation of RB1 depleted human embryonic stem cell line (RB1-null hESCs) and RB1patient-specific induced pluripotent (iPSC) line harbouring RB1 biallelic mutation (c.2082delC)