Background

Transgenic mouse lines expressing Cre recombinase under the control of endothelial specific gene promoters (such as VEcadherin-cre or Tie2-cre) allow selective targeting of the vasculature. However, currently available models target both blood and lymphatic endothelia, and therefore do not allow addressing the specific roles of genes in lymphangiogenesis, due to potential overlapping functions of genes in the blood vasculature.

Method

By utilising Cre-loxP technology and BAC (Bacterial Artificial Chromosome) transgenesis we have generated a novel genetic model that enables temporally controlled, highly efficient and specific gene (in)activation in lymphatic endothelia, in mice of all developmental stages and in adults.

Results

A transgenic line was obtained that expresses tamoxifen inducible Cre recombinase under the control of the homeobox transcription factor Prox1 gene promoter, which is a specific and the first known marker of differentiated lymphatic endothelial cells. Crossing Prox1-creERT2 line with transgenic mice, in which a gene of interest has been flanked by loxP sites, provides a spatial and temporal control over the deletion of a selected gene. In addition, we have utilised the Prox1-creERT2 mice to generate a fluorescent reporter line expressing membrane-bound GFP in lymphatic endothelia. This will enable lineage-tracing analyses of lymphatic endothelial cells and live imaging studies of developing lymphatic vessels in vivo.

Conclusion

In summary, these mouse lines provide valuable tools for functional studies targeting specifically lymphatic endothelium, which will enable detailed characterisation of the molecular mechanisms regulating lymphatic vessel formation.