The Expression Of AFP During Rat Pancreas Development And Its Significance

To identify proteins involved in pancreatic development, we used adifferential proteomics approach by comparing pancreatic extracts fromfour biologically significant stages of its development: embryonic day (E)15.5, E18.5, newborn and adult. By two-dimensional gel electrophoresis(2D-E) and MALDI-TOF MS following database searching and proteinannotation, several protein spots that changed significantly in thepancreas between the four phases were identified, among which 8 spotswere identified as Alpha-fetoprotein (AFP). This result was correlatedwith their gene expression demonstrated by high-density microarray inour previous work.To investigate the potential role of the alpha-fetoprotein (AFP) inpancreatic development and function, the expression profile of AFPisoforms intrinsic to the normal developing rat pancreas was furtherstudied. The localization and the expression pattern of AFP in ratpancreas from seven biologically significant stages (E15.5,E18.5,P0,P7,P14,P21 and adult) was determined by immunohistochemistry andWestern blotting respectively. Four isoforms of AFP (72 kDa, 60 kDa, 48kDa and 37 kDa) were found by Western blotting in the pancreas tested, most of them showed a stronger signal in E18.5 followed by a slightlydecrease to a moderate levels. Only 60kDa isoform was detected in theadult pancreas. Immunolocalisation for AFP revealed that a positivereactivity was detectable at E15.5 pancreas, became stronger incytoplasm of mesenchyme cells at E18.5 and newborn rat pancreas, andwas nearly undetectable in adult. The expression pattern of K-ras p21 inrat pancreas from seven biologically significant stages (E15.5, E18.5, P0,P7, P14, P21 and adult) was also determined by Western blotting and theresults indicated that K-ras p21 has a very similar expression profile toAFP but with lower levels detected during development.Our present studies for the first time demonstrated that AFP waslocalized to mesenchyme in rat pancreas from E15.5 to neonatal andpresented 4 isoforms in fetal and neonatal rat pancreas and remained oneisoform in adult rat pancreas. The differential expression of four AFPisoforms in the various developmental stage of pancreas indicates thatAFP might be involved in some aspects of pancreas development. Theeffect of AFP on the organic development may be achieved by alteringthe expression of K-ras p21 gene.