Mesenchymal Igf2 is a major regulator of pancreatic growth and function

The genetic mechanisms that determine the size of the adult pancreas are not fully understood. Here we address the importance of the imprinted Igf2 gene for growth and function of the mouse pancreas. We used reporter lines to monitor Igf2 levels during late fetal and postnatal pancreatic development and demonstrate that Igf2 is mostly expressed within the mesenchyme. We manipulated Igf2 levels in vivo in the major pancreas cell types using Cre lines and found that loss of Igf2 from the developing mesenchyme results in pancreatic hypoplasia, associated with loss of acinar and beta-cell mass, postnatal whole-body growth restriction and maternal glucose intolerance during pregnancy. Overexpression of Igf2 directed to the mesenchyme results in pancreatic overgrowth. Importantly, deletion of Igf2 from the developing epithelium has no growth effects. Our findings demonstrate that a major role for Igf2 is the regulation of pancreas size, and reveal an unforeseen key function for mesenchymal IGF signalling in pancreatic growth. We generated mRNA profiles of mesenchymal and non-mesenchymal cells isolated by FACS from P2 pancreata of mice with mesenchymal specific deletion or overexpression of Igf2 and littermate controls