Mutations in SEC23B have been reported in congenital dyserythropoietic anemia type II (CDAII) [129,130], and mice deficient for Sec23b (Sec23bgt/gt mice) display developmental defects in pancreatic acinar cells such as degeneration of acinar cells, absence of zymogene granules, accumulation of exocrine proteins in the ER, and dilated ER since the contents of the zymogen granules cannot exit from the ER via COPII vesicles [27]. The gene discussed is SEC23B; the disease is congenital dyserythropoietic anemia type 2.