PDX1 and diabetes mellitus: SOX9+ precursor-like cells rapidly respond to a diabetic environment in the first 2 weeks post-Tx as the percentage of PDX1+ progenitor-like cells remained steady in both NDM and DM mice within the first month post-Tx; as only slightly more PDX1+ insulin− precursor-like cells participated in generation of new β cells in DM mice at 60-day post-Tx.