Targeted disruption of the Reg protein receptor gene : The relationship of the Reg-Reg receptor system with pancreatic 13-cell replication.

Reg（Regenerating gene，再生基因）基因编码一种分泌蛋白，其通过Reg受体（RegR）作为自分泌/旁分泌生长因子诱导胰腺13细胞增殖。积累的体外和体内证据-包括使用Reg转基因和Reg+小鼠的证据</->表明，Reg蛋白还参与多种组织如胃肠、神经和心血管细胞中的再生细胞增殖。在这里，我们产生了RegR靶向破坏的小鼠，以研究Reg-Reg受体系统在组织再生和发育中的影响。杂合突变小鼠（RegR^&lt;+/-&gt;）具有正常的生育力和寿命，并保持与其野生型组相似的体重和血糖水平。此外，在RegR^&lt;+/-&gt;小鼠和野生型之间胰腺β细胞质量没有差异，而RegR^&lt;+/-&gt;小鼠的组织中RegR的mRNA和蛋白质水平约为野生型的一半。然后，我们将RegR^&lt;+/-&gt;小鼠杂交，发现完全没有RegR^（+/-）幼崽，表明这种基因型是胚胎致死的。对杂合子的定时妊娠显示，RegR^（+/-）在妊娠后8.5至9.5天死亡。由于Reg^（+/-）小鼠显示出降低的β细胞再生活性，我们通过在Reg ^（+/-）小鼠中进行部分胰腺切除术来诱导胰腺β细胞复制。术后RegR^（+/-）小鼠胰腺β细胞BrdU掺入和PCNA阳性细胞数均较RegR ^（+/+）小鼠减少。这些结果表明，Reg-Reg受体系统对于正常小鼠发育以及胰腺β细胞的复制是必需的。

Reg (Regenerating gene) gene encodes a secretory protein that induces pancreatic 13-cell proliferation as an autocrine/paracrine growth factor via Reg receptor (RegR). Accumulating in vitro and in vivo evidence- including that using Reg transgenic and Reg^</-> mice suggest that Reg protein is also involved in regenerative cell proliferation in a variety of tissues such as gastrointestinal, neural and cardiovascular cells. Here, we produced mice with a targeted disruption of RegR to investigate the impact of the Reg-Reg receptor system in tissue regeneration and development. The heterozygous mutant mice (RegR^<+/-> had normal fertility and lifespans and maintained similar body weight and blood glucose level to those of their wild-type cohorts. In addition, there was no difference in pancreatic β-cell mass between RegR^<+/-> mice and the wild type whereas the mRNA and protein levels of RegR in the tissues of RegR^<+/-> mice were about half of the wild type. We then intercrossed RegR^<+/-> mice and found the total absence of RegR^(+/-) pups, indicating that this genotype is embryonic lethal. Timed pregnancies of heterozygotes revealed that RegR^(+/-) die between 8.5 and 9.5 days post coitum. As Reg^(+/-) mice showed the decreased β-cell regenerating activity, we induced pancreatic β-cell replication by partial pancreatectomy in RegR^<+/-> mice. Both the BrdU incorporation and the PCNA positive cells in pancreatic β-cells of RegR^(+/-) mice were decreased compared to those of RegR^(+/+) mice after surgery. These results indicate that the Reg-Reg receptor system is essential for normal mouse development as well as for replication of pancreatic β-cells.