RIP-Cre Revisited, Evidence for Impairments of Pancreatic β-Cell Function

Abstract

The Cre/loxP recombinase system for performing conditional gene targeting experiments has been very useful in exploring genetic pathways that control both the development and function of pancreatic ␤-cells. One particular line of transgenic mice (B6.CgTg(Ins2-cre)25Mgn/J), commonly called RIP-Cre, in which expression of Cre recombinase is controlled by a short fragment of the rat insulin II gene promoter has been used in at least 21 studies on at least 17 genes. In most of these studies inactivation of the gene of interest was associated with either glucose intolerance or frank diabetes. Experimental evidence has been gradually emerging to suggest that RIP-Cre mice alone display glucose intolerance. In this study experiments from three laboratories demonstrate that RIPCre mice, in the absence of genes targeted by loxP sites, are glucose intolerant, possibly due to impaired insulin secretion. In addition, we review the use of RIP-Cre mice and discuss possible molecular underpinnings and ramifications of our findings.

Pancreatic deletion of insulin receptor substrate 2 reduces beta and alpha cell mass and impairs glucose homeostasis in mice

“…Studies with our colony of RIPCre (B6.Cg-tg(Ins2-cre) 25Mgn/J) transgenic mice failed to detect glucose intolerance in this strain in either sex up to 24 weeks of age, in contrast to a recent report [12]. While we originally obtained RIPCre mice from the Jackson Laboratory, these animals were intercrossed for several generations with either 129Sv/C57Bl/6 or 129Sv/C57Bl/6/BALB/c hybrids used to generate floxed alleles and these latter strains were not obtained from the same source.…”

“…Normal glucose tolerance in RIPCre mice maintained on two genetic backgrounds As discussed above, it has been suggested that RIPCre (B6.Cg-tg(Ins2-cre)25Mgn/J) transgenic mice develop glucose intolerance in the absence of any gene deletion [12]. This was particularly apparent in mice obtained from the Jackson Laboratory maintained on a C57Bl/6 background.…”

“…First, in this animal there was extensive expression in hypothalamic neurons, which resulted in obesity, hyperleptinaemia and hyperinsulinaemia when either Irs2 or indeed Insr was deleted in these cells [8][9][10]20]. Second, it has been suggested that the RIPCre mouse is intrinsically glucose intolerant [12]. Our current studies have utilised a Pdx1-cre mouse to delete Irs2 only in the pancreas, thus generating PIrs2KO mice.…”

“…First, significant Cre recombinase expression in the hypothalamus resulted in the development of obesity, hyperleptinaemia and insulin resistance, which together per se will alter beta cell function [8][9][10]. Second, RIPCre mice themselves have been reported to display mild glucose intolerance, although it was unclear whether this was due to the influence of genetic background or the effects of Cre recombinase expression in beta cells [12]. To attempt to circumvent these problems, we have generated mice lacking Irs2 in the pancreas using a mouse in which Cre recombinase expression is driven by the promoter of the pancreatic and duodenal homeobox factor 1 (Pdx1, also known as Ipf1) gene, one of the earliest and most specific endoderm markers of the developing pancreas [13].…”

Autophagy deficiency in beta cells leads to compromised unfolded protein response and progression from obesity to diabetes in mice

“…5c). To examine the possible deleterious effect of RIP-Cre transgene expression itself [23] on diabetes in Atg7 Δβ-cell -ob/ob mice, we studied the glucose profile of our Rip-Cre + mice. Fasting blood glucose level and glucose tolerance after i.p.…”