Notably, while heterozygous mice develop endocrine tumors of the pancreatic islets and pituitary similar to those observed in patients, no gastrinomas were reported in this model.135 Subsequent mouse models generated by our group addressed the absence of any apparent gastric phenotype by conditionally deleting Men1 from the GI tract epithelium. Here, MEN1 is linked to gastrin-producing neuroendocrine tumor.