The toolbox of rat genetics currently lacks the ability to introduce site-directed, heritable mutations into the genome to create knockout animals. Using engineered zinc-finger nucleases (ZFNs) designed to target an integrated reporter and two endogenous rat genes, Immunoglobulin M (IgM) and Rab38, we demonstrate that a single injection of DNA or mRNA encoding ZFNs into the one-cell rat embryo leads to a high frequency of animals carrying 25-100% disruption at the target locus. These mutations are faithfully and efficiently transmitted through the germline. Our data demonstrate the feasibility of targeted gene disruption in multiple rat strains within four months time, paving the way to a humanized monoclonal antibody platform and additional human disease models.The laboratory rat is a well-established model for the genetic dissection of human diseaserelated traits (1) despite the fact that targeted modification of its genome is largely intractable. We investigated the application of engineered zinc-finger nucleases (ZFNs;(2)) for the elimination of specific rat gene function and generation of "knockout" rats. ZFNs induce sitespecific, double-strand DNA breaks that can be repaired by the error-prone non-homologous end joining DNA repair pathway to result in a targeted mutation (Fig. 1A). In the fruit fly and zebrafish, direct embryo injection of ZFN-encoding mRNA has been used to generate heritable knockout mutations at specific loci (2).The design and validation of ZFN reagents to target a single-copy Green Fluorescent Protein (GFP) transgene inserted in a rat chromosome and two endogenous rat genes, IgM and

In this study, we have identified a novel member of the AMPK family, namely Sucrose non-fermenting related kinase (Snrk), that is responsible for maintaining cardiac metabolism in mammals. SNRK is expressed in the heart, and brain, and in cell types such as endothelial cells, smooth muscle cells and cardiomyocytes (CMs). Snrk knockout (KO) mice display enlarged hearts, and die at postnatal day 0. Microarray analysis of embryonic day 17.5 Snrk hearts, and blood profile of neonates display defect in lipid metabolic pathways. SNRK knockdown CMs showed altered phospho-acetyl-coA carboxylase and phospho-AMPK levels similar to global and endothelial conditional KO mouse. Finally, adult cardiac conditional KO mouse displays severe cardiac functional defects and lethality. Our results suggest that Snrk is essential for maintaining cardiac metabolic homeostasis, and shows an autonomous role for SNRK during mammalian development.

Nogo-B receptor (NgBR) was identified as a specific receptor for binding Nogo-B, and is essential for the stability of Niemann-Pick type C2 protein (NPC2) and NPC2-dependent cholesterol trafficking. Here, we report that NgBR expression levels decrease in the fatty liver and that NgBR plays previously unrecognized roles in regulating hepatic lipogenesis via NPC2-independent pathways. To further elucidate the pathophysiological role of NgBR in mammals, we generated NgBR liver-specific knockout mice and investigated the roles of NgBR in hepatic lipid homeostasis. Our results showed that NgBR knockout in mouse liver did not decrease either NPC2 levels or increase NPC2-dependent intracellular cholesterol levels. However, NgBR deficiency still resulted in remarkable cellular lipid accumulation that was associated with increased free fatty acids (FFA) and triglycerides (TG) in hepatocytes in vitro and in mouse livers in vivo. Mechanistically, NgBR deficiency specifically promotes the nuclear translocation of the liver X receptor alpha (LXRα) and increases the expression of LXRα-targeted lipogenic genes. LXRα knockout attenuates the accumulation of FFA and TG caused by NgBR deficiency. In addition, we elucidated the mechanisms by which NgBR bridges the AMP-activated protein kinase α (AMPKα) signaling pathway with LXRα nuclear translocation and LXRα-mediated lipogenesis. Our study demonstrates that NgBR is a specific negative regulator for LXRα–dependent hepatic lipogenesis and suggests that loss of NgBR is a potential trigger for inducing hepatic steatosis.

Nogo-B receptor (NgBR) was identified as a receptor specific for Nogo-B. Our previous work has shown that Nogo-B and its receptor (NgBR) are essential for chemotaxis and morphogenesis of endothelial cells in vitro and intersomitic vessel formation via Akt pathway in zebrafish. Here, we further demonstrated the roles of NgBR in regulating vasculature development in mouse embryo and primitive blood vessel formation in embryoid body culture systems, respectively. Our results showed that NgBR homozygous knockout mice are embryonically lethal at E7.5 or earlier, and Tie2Cre-mediated endothelial cell-specific NgBR knockout (NgBR ecKO) mice die at E11.5 and have severe blood vessel assembly defects in embryo. In addition, mutant embryos exhibit dilation of cerebral blood vessel, resulting in thin-walled endothelial caverns. The similar vascular defects also were detected in Cdh5(PAC)-CreERT2 NgBR inducible ecKO mice. Murine NgBR gene-targeting embryonic stem cells (ESC) were generated by homologous recombination approaches. Homozygous knockout of NgBR in ESC results in cell apoptosis. Heterozygous knockout of NgBR does not affect ESC cell survival, but reduces the formation and branching of primitive blood vessels in embryoid body culture systems. Mechanistically, NgBR knockdown not only decreases both Nogo-B and VEGF-stimulated endothelial cell migration by abolishing Akt phosphorylation, but also decreases the expression of CCM1 and CCM2 proteins. Furthermore, we performed immunofluorescence (IF) staining of NgBR in human cerebral cavernous malformation patient tissue sections. The quantitative analysis results showed that NgBR expression levels in CD31 positive endothelial cells is significantly decreased in patient tissue sections. These results suggest that NgBR may be one of important genes coordinating the cerebral vasculature development.