[1] Stowers Inst Med Res, Kansas City, MO 64110 USA
[2] Brigham Young Univ Idaho, Dept Biol, Rexburg, ID USA
[3] Imperial Coll London, Dept Life Sci, London, England
[4] Univ Oxford, Math Inst, Wolfson Ctr Math Biol, Oxford, England
[5] Univ Kansas, Sch Med, Dept Anat & Cell Biol, Kansas City, KS 66160 USA