Targeting vectors for making Scfgfp and Scffl mice were constructed by recombineering34 (link). The Frt flanked Neo cassette was removed by mating with Flpe mice35 (link). Scfgfp and Scffl mice were backcrossed onto a C57BL background before analysis. Mice used in this study included Ubc-CreER36 (link), CMV-Cre37 (link), Vav1-Cre28 (link), Nestin-Cre38 (link), Tie2-Cre31 (link), Lepr-Cre39 (link), and LoxpEYFP29 (link) (all from the Jackson Laboratory), Col2.3-Cre30 (link), Nestin-CreER40 (link) and Nestin-GFP41 (link). All were maintained on a C57BL background. Unless otherwise indicated, data always reflect mean±s.d. and two-tailed student’s t-tests were used to assess statistical significance (*p<0.05, **p<0.01, ***p<0.001). Detailed methods are available online.