Towards a Venous Malformation Mouse Model

Uebelhoer, Mélanie [UCL] Limaye, Nisha [UCL] Brouillard, Pascal [UCL] Achouri, Younes [UCL] Vikkula, Miikka [UCL]

Substitutions in the endothelial cell tyrosine kinase receptor TIE2/TEK cause both inherited and sporadic forms of venous anomalies, Mucocutanous Venous Malformation (VMCM) and Venous Malformation (VM). The identification of the etiopathogenic cause provides us with a means by which to generate an in vivo mouse model of the disease. “Knock-in” mouse lines carrying the most frequent VM-causative Tie2 mutations, inherited R849W and somatic L914F, are being created. The targeting constructs replace wild-type exon 15 (R849) or 17 (L914) with cDNA starting at exon 15 or 17 respectively, followed by the remaining 3’ coding region flanked by loxP sites, and then the mutant exon. Upon Cre-expression, the cDNA containing the wild-type exon will be floxed out, leaving only the mutant exon and the endogenous 3’ exons to be expressed. After electroporation, five homologously recombined murine ES cell-clones have been identified for the L914F-construct. Two selected clones have been injected into blastocysts to generate targeted mice and 8 chimeras have been born. Wild-type Tie2 excision will be induced ubiquitously by crossing these lines with PGK-Cre transgenic mice. Replacement specifically in endothelial cells will be obtained by crossing them with VECad-Cre-ERT2 transgenics expressing Cre recombinase in a tamoxifen-dependent, EC specific manner. The in vivo model of VMs will allow us to further study these mutations and understand their etiopathogenic mechanisms.