Mouse lines and treatments

TgCreER^T2 mice with inducible Cre under control of the Tg promoter (Undeutsch et al., 2014) were crossed with Braf^CA mice (Dankort et al., 2007) to generate TgCreER^T2;Braf^CA/+ mice. Both Cre lines were crossed with Rosa26R and mTmG reporter mice for lineage tracing, as described (Muzumdar et al., 2007; Soriano, 1999). Strains were backcrossed with C57BL/6J mice at least ten generations before recombination. Tail tips were sampled for genotyping with PCR. Tamoxifen dissolved in sunflower oil (10 mg/ml) was injected intraperitoneally (50 µl) once daily for a total of 3 days to induce expression of CreER^T2. PLX4720 (417 ppm), the precursor compound of vemurafenib (PLX4032), and control dietary pellets (both provided by Plexxikon) were continuously supplied during the treatment period. Animal experiments were approved by the regional ethic committee (Dnr 26-2013 and Dnr 5.8.18-03925/2018) according to European standards and national regulations provided by the Swedish Agriculture Agency.