Figure 2.

Characterization of SOX9+/PTF1A+ cells. SOX9+/PTF1A+ cells do not express markers of endocrine differentiation as shown by co‐staining with SOX9 (red), PTF1A (green), and either INSULIN (light blue) (A) or GLUCAGON (light blue) (B). Scale bar: 25 μm. Magnification of the quadrants indicated in the merged left panels clearly shows that INSULIN and GLUCAGON do not co‐localize with either SOX9 or PTF1A (arrowheads); SOX9 and PTF1A co‐expressing cells are in yellow (asterisks). hFP: 14WGA. (C): AMYLASE (green) expression was not detected at 14WGA (left panel). Human adult pancreas (right panel) was used as a positive control to confirm specificity of the AMYLASE antibody. Nuclei are in DAPI. Scale bar: 50 μm. (D): Detection of CPA1 expression at 13.5 and 17WGA. CPA1 staining (magenta, cytoplasmic staining) is coupled with SOX9 staining (green, nuclear staining). CPA1 is detected at 13.5WGA, and its expression is noticeably increased by 17WGA. Although all CPA1+ cells also express SOX9 (arrowheads) at 13.5WGA, by 17WGA some CPA1+ cells have lost SOX9 expression (asterisks), suggesting the presence of more committed cells (CPA1+/SOX9−, asterisks) within the tip population at this later stage. However, CPA1+/SOX9+ cells are still detectable at this later stage. Scale bar: 100 μm. (E): Co‐staining for SOX9 (magenta), PTF1A (green), and proliferative cell nuclear antigen (PCNA, yellow) shows that SOX9+/PTF1A+ cells are proliferative. Given that a combination of magenta and green results in white and all markers are nuclear, cells positive for SOX9, PTF1A, and PCNA are visible in yellow. Scale bar: 50 μm, hFP: 13.5WGA.