We analyzed the expression of genes encoding beta cell specific transcription factors such as Pdx1, MafA, Nkx6.1, Insulin (Ins1 and Ins2), proteins implicated in insulin processing and secretion such as Pcsk1, Slc2a2, Ucn3, Chga, protein targets of autoantibodies found in the blood of T1D patients, such as Slc30a8, Ptprn, Gad1 and Cfap126, a recently described beta cell heterogeneity marker [50]. The gene discussed is PCSK1; the disease is type 1 diabetes mellitus.