Site Specific Recombinases (SSRs): Dre & Rox-stop-Rox Reporters

While I was a postdoc in Benoit Bruneau's laboratory I was interested in dual-lineage mapping the first and second heart fields in the same developing embryo. While there existed a myriad of tools for Cre-mediated lineage analysis, fewer options existed for other site-specific recombinases (SSRs).

However, a publication dealing with a novel SSR, Dre, from Dr. Francis Stewart's laboratory (TU-Dresden) was particularly encouraging. Dre recognizes rox sites (like Cre recognizes lox sites) and they demonstrated that Dre does not act on loxP sites in vivo (and vice versa). 

In Benoit's lab I engineered a novel Second Heart Field Dre line using the Mef2c-AHF enhancer identified by Brian Black. We determined that, using the Stewart Lab's Rosa-rox-stop-rox-lacZ line, the Mef2c-AHF::Dre line was equally as effective as Mef2c-AHF::Cre.

Another fellow in the Bruneau Lab, Patrick Devine MD., Ph.D. pushed the system forward by creating a fluorescent reporter line analogous to the Rosa-mTmG line, Rosa-nKmB. Furthermore, in a gigantic leap forward he fused the mutant Estrogen Receptor (ERT2) to Dre, and demonstrated that the activity of Dre could be regulated not only in a spatial, but also a temporal, manner. See Devine WP et al., Elife, 2014 for details.

But what about labeling two lineages simultaneously, using two different SSRs in the same embryo?