Gene Editing Rat Resource Center (GERRC): Designer rats for heart, lung and blood studies
Authors: Schilling Rebecca , Gryzbowski Michael , Pietrzak Stefan , Temple Anne , Zappa Allison , Lazcares Lynn , Niebuhr Jessica , Kalloway Shawn , Foeckler Jamie , Takizawa Akiko , Geurts Aron M , Dwinell Melinda R. 
Published: November 2023

The age of rat genome editing through the use of Zinc‐Finger Nucleases (ZFNs), TAL Effector Nucleases (TALENs) and Clustered Regularly Interspaced Short Palindromic Repeats‐Cas9 (CRISPR/Cas9) nuclease systems has made available to all investigators thousands of gene‐modified strains which can be used to validate a gene underlying a quantitative trait locus, to test a nominated human gene or to design follow up studies to define function of predicted genes or sequence variants. We are currently in the fourth year of developing rat models for investigators to validate human variation and study function and mechanism for genes implicated in heart, lung and blood disorders. The Gene Editing Rat Resource Center (GERRC) is an R24 grant funded by NHLBI that enables us to utilize an already existing infrastructure of personnel, expertise in gene editing, embryo microinjection, high‐throughput genotyping, sequencing, cryopreservation and rat distribution channels to generate and provide novel and important rat models to many of these investigators. An established External Advisory Board (EAB) assesses our progress and, moreover, conducts a scientific merit review of all applications to select the genes and effectively use the resources of the R24 nominated by the scientific community. Primarily through the use of the CRISPR/Cas9 nuclease system, we are producing custom knockout, knockin and transgenic rat models by applying pronuclear microinjection of in vivo‐transcribed mRNAs encoding them into rat embryos. The resulting offspring are screened for mutations using a Cel‐I assay, and the resulting mutants TOPO cloned and validated by sequencing. To date, we have transferred over 14,359 microinjected embryos into the oviducts of pseudo‐pregnant Sprague‐Dawley recipient females resulting in 3050+ live‐born pups of which 2300+ have been screened for mutagenesis of the target locus. Of these, we have successfully generated ~550 pups containing mutations in 112 genes in 14 inbred, outbred, consomic and congenic rat strains (Dark Agouti [DA/MolTac], Dahl Salt‐Sensitive [SS/JrHsd/Jr/Mcwi and SS/JrHsdMcwiCrl], Wistar Kyoto [WKY/NCrl], Lewis [LEW/Crl], T2DN/Mcwi, Spontaneously Hypertensive Stroke Prone [SHRSP/A3NCrl], SS.BN‐(D13Rat124‐Scor13_3694), SS‐Chr 13BN/McwiCrl, LH‐17LN, Fawn‐hooded Hypertensive [FHH/EurMcwi] and FHH‐Chr 3BN/Mcwi, Crl:SD, FHH.PCK‐(D9Rat35‐D9Rat70)/Mcwi). Heterozygous pups are distributed to the requesting investigator and then, eventually, made available to the rat research community prior to sperm cryopreservation. Currently, 45 mutant strains have been transferred out and 25 in various stages of breeding prior to distribution. Investigators are welcome to nominate their gene of choice by filling out an application.http://rgd.mcw.edu/wg/custom_rats/gerrc.Support or Funding InformationThe National Heart, Lung, and Blood Institute of the National Institutes of Health, R24HL114474