UC San Diego

Cerberus1 is a secreted protein that has emerged as a critical regulator of embryogenesis in mouse, frog, and more recently human embryos. Despite the wealth of information about its roles in embryogenesis, there has yet to be a complete understanding of its role in human embryonic stem cell (hESC) pluripotency and differentiation into cells of the Definitive Endoderm (DE) and eventually insulin-producing, glucose responsive cells. These insulin-producing, glucose responsive cells regulate blood glucose levels and are the focus of regenerative therapies for the treatment of Type 1 Diabetes. Understanding how biochemistry and signal transduction regulate this transition out of pluripotency is not only critical to understand how cells communicate with the extracellular environment but also to develop safe and effective protocols to generate tissues from select cell lines. In this report, we created a model system to modulate DE formation and look at the role of secreted proteins on differentiation. We show that changes in the media from directed differentiation protocols signal the cells, which then actively respond by upregulating secreted proteins such as Cer1. We used conditioned media, Cer1 antibodies, and exogenous Cer1 to show that Cer1 modulates cell fate when it’s secreted by hESCs. Taken together, these results show that Cer1 is not simply a marker of DE but it also plays an active role in regulating differentiation by signaling to the cells that DE formation is complete and therefore halting differentiation. These findings provide insight into how cells communicate with the extracellular aid in enhancement of the production of insulin-secreting, glucose responsive cells across different hESC lines.