PDX1 and keratoconus: Mice with an activating mutation in Kras (lox-STOP-lox KrasG12D) [15] that is specifically targeted to the pancreas by a Pdx1-Cre driver (abbreviated KC mice) were crossed with a mouse line in which the exon 4 of Sirt1 is flanked by loxP sites to obtain homozygous Sirt1-deficient KC mice (KC;Sirt1-lox) [14, 16].