Tamoxifen-inducible Cre-mediated calreticulin excision to study mouse embryonic stem cell differentiation.

Embryonic stem cells are useful to study the functional aspects of lineage commitment. In this study, we report that using the Cre/loxP system provides a useful tool for studying multifunctional proteins that are involved in stem cell differentiation, such as calreticulin. Calreticulin is a chaperone and a major calcium buffer of the endoplasmic reticulum and it functions during both adipogenesis and cardiomyogenesis. We used both a tamoxifen-inducible and cardiomyocyte-specific alpha-myosin heavy chain promoter-driven Cre/loxP system to study cardiomyogenesis, and a tamoxifen-inducible ubiquitously expressed cytomegalovirus promoter-driven Cre/loxP system to study adipogenesis. Both Cre/loxP systems mimicked the results previously observed using the calreticulin-null stem cell systems. Our results indicate that the tamoxifen-inducible Cre/loxP system is an effective and reliable tool to use for gene ablation in studies on functional aspects of stem cell biology.