PTF1A and keratoconus: We then sought to evaluate the effect of Pikfyve loss on PDAC development by crossing Pikfyve+/+, Pikfyvef/+, or Pikfyvef/f with the KC model (Ptf1a-Cre ; LSL-KrasG12D/+ ) to assess pancreatic tumorigenesis (Fig. 1H).