Single-Cell RNA Sequencing Reveals Metallothionein Heterogeneity during hESC Differentiation to Definitive Endoderm [scRNA-Seq]

Differentiation of human pluripotent stem cells toward definitive endoderm (DE) is the critical first step for generating cells comprising organs such as the gut, liver, pancreas and lung. This in-vitro differentiation process generates a heterogeneous population with a proportion of cells failing to differentiate properly and maintaining expression of pluripotency factors such as Oct4. RNA-sequencing of single cells collected at four time points during a 4-day DE differentiation identified high expression of metallothionein genes in the residual Oct4-positive cells that failed to differentiate to DE. Using X-ray fluorescence microscopy and multi-isotope mass spectrometry, we discovered that high intracellular zinc level corresponds with persistent Oct4 expression and failure to differentiate. We further show that differentiation-arrested phenotype is inversely correlated with zinc concentration in the differentiation media. This study improves our understanding of in-vitro DE differentiation and provides actionable options to improve DE differentiation efficiency.