Optogenetic control of early embryos labeling using photoactivatable Cre recombinase 3.0

Establishing a highly efficient photoactivatable Cre recombinase PA‐Cre3.0 can allow spatiotemporal control of Cre recombinase activity. This technique may help to elucidate cell lineages, as well as facilitate gene and cell function analysis during development. This study examined the blue light‐mediated optical regulation of Cre‐ loxP recombination using PA‐Cre3.0 transgenic early mouse pre‐implantation embryos. We found that inducing PA‐Cre3.0 expression in the heterozygous state did not show detectable recombination activation with blue light. Conversely, in homozygous embryos, DNA recombination by PA‐Cre3.0 was successfully induced by blue light and resulted in the activation of the red fluorescent protein reporter gene, while almost no leaks of Cre recombination activity were detected in embryos without light illumination. Thus, we characterize the conditions under which the PA‐Cre3.0 system functions efficiently in early mouse embryos. These results are expected to provide a new optogenetic tool for certain biological studies, such as developmental process analysis and lineage tracing in early mouse embryos.