Correspondence Between Mouse and Human Pancreatic Development

Despite the seemingly perfect conservation across species of most transcription factors already discussed, even a superficial analysis of human pancreatic development reveals striking differences with that of the mouse. The following are just a few examples: the relative speed of the transition between the initiation of pancreatic development and the emergence of the first hormone-positive cells in the epithelium is remarkably faster in the mouse. According to the relative timeframe observed in the latter, the detection of the first endocrine cells in humans would take place no later than 4.5/5 weeks postconception (w.p.c.). However, extensive immunohistochemical analyses of the developing human pancreas show that the first endocrine cells are not detectable prior to 7 w.p.c., more than 3 weeks after pancreatic specification. 216 The biological significance of this relative delay is not fully understood yet. The first endocrine cells to appear during human pancreatic development are beta cells (7 w.p.c.). In contrast with the mouse, a cells do not appear until later, at around 8.5 w.p.c. Islets assemble just prior to term in mouse, whereas human islets are fully formed from 12 to 13 w.p.c. Read the rest of this entry »