Long Interspersed Element 1 (LINE-1 or L1) is the only autonomously mobile retrotransposon active in modern human genomes, and an important source of inter-individual genetic variation as well as somatic genetic mosaicism within individuals. L1 retrotransposition can be studied in cultured cells and in transgenic animals using engineered constructs wherein L1 retrotransposition delivers an enhanced green fluorescent protein (EGFP) reporter into genomic DNA.
This system has enabled numerous insights into the mechanism, regulation, and consequences of L1 retrotransposition. However, previous work demonstrated that engineered L1-EGFP reporter insertions are subject to rapid epigenetic silencing in vitro. Furthermore, epigenetic silencing of L1-EGFP transgene-derived insertions in vivo may result in an underestimation of L1-driven genetic mosaicism in animal models. Here, we are developing a new reporter system wherein engineered L1 retrotransposition delivers a Cre recombinase reporter gene.
Cre recombinase may then act upon a floxed EGFP gene inserted in a safe-harbour genomic locus, ensuring constitutive EGFP expression in the cell harbouring the nascent L1 insertion as well as its mitotic descendants. The goal of this system is to enable comprehensive fluorometric analysis of L1-mediated genetic mosaicism in vivo.