To determine when and how the ∼50% reduction in Sox17 expression in Sox17Δ50/Δ50 mice impairs GB and CD development, we performed immuno-labeling studies of the HPB buds at E9.5 and E11.5, two representative timepoints in the segregation and outgrowth of hepatic, pancreatic and biliary cell fates. Here, SOX17 is linked to Cowden disease.