Rabbit Anti-Mouse MAFA Polyclonal Antibody

Adenoviral gene transfer of key beta cell developmental regulators including Pdx1, Neurod1, and Mafa (PDA) has been reported to generate insulin-producing cells in the liver. However, PDA insulin secretion is transient and glucose unresponsive. Here, we report that an additional beta cell developmental regulator, insulin gene enhancer binding protein splicing variant (Isl1 beta), improved insulin production and glucose-responsive secretion in PDA mice. Microarray gene expression analysis suggested that adenoviral PDA transfer required an additional element for mature beta cell generation, such as Isl1 and Elf3 in the liver. In vitro promoter analysis indicated that splicing variant Isl1, or Isl1 beta, is an important factor for transcriptional activity of the insulin gene. In vivo bioluminescence monitoring using insulin promoter-luciferase transgenic mice verified that adenoviral PDA + Isl1 beta transfer produced highly intense luminescence from the liver, which peaked at day 7 and persisted for more than 10 days. Using insulin promoter-GFP transgenic mice, we further confirmed that Isl1b supplementation to PDA augmented insulin-producing cells in the liver, insulin production and secretion, and b cell. related genes. Finally, the PDA + Isl1 beta combination ameliorated hyperglycemia in diabetic mice for 28 days and enhanced glucose tolerance and responsiveness. Thus, our results suggest that Isl1 beta is a key additional transcriptional factor for advancing the generation of insulin-producing cells in the liver in combination with PDA.

Early in pancreatic development, epithelial cells of pancreatic buds function as primary multipotent progenitor cells (1 degrees MPC) that specify all three pancreatic cell lineages, i.e., endocrine, acinar and duct. Bipotent "Trunk" progenitors derived from 1 degrees MPC are implicated in directly regulating the specification of endocrine progenitors. It is unclear if this specification process is initiated in the 1 degrees MPC where some 1 degrees MPC become competent for later specification of endocrine progenitors. Previously we reported that in Pdx1(tTA/+); tetO(MafA) (bigenic) mice inducing expression of transcription factor MafA in Pdx1-expressing (Pdx1(+)) cells throughout embryonic development inhibited the proliferation and differentiation of 1 degrees MPC cells, resulting in reduced pancreatic mass and endocrine cells by embryonic day (E) 17.5. Induction of the transgene only until E12.5 in Pdx1(+) 1 degrees MPC was sufficient for this inhibition of endocrine cells and pancreatic mass at E17.5. However, by birth (P0), as we now report, such bigenic pups had significantly increased pancreatic and endocrine volumes with endocrine clusters containing all pancreatic endocrine cell types. The increase in endocrine cells resulted from a higher proliferation of tubular epithelial cells expressing the progenitor marker Glut2 in E17.5 bigenic embryos and increased number of Neurog3-expressing cells at E19.5. A BrdU-labeling study demonstrated that inhibiting proliferation of 1 degrees MPC by forced MafA-expression did not lead to retention of those progenitors in E17.5 tubular epithelium. Our data suggest that the forced MafA expression in the 1 degrees MPC inhibits their competency to specify endocrine progenitors only until E17.5, and after that compensatory proliferation of tubular epithelium gives rise to a distinct pool of endocrine progenitors. Thus, these bigenic mice provide a novel way to characterize the competency of 1 degrees MPC for their ability to specify endocrine progenitors, a critical limitation in our understanding of endocrine differentiation.