Abstract P469: CRISPR-Cas9 Gene Editing Yields Genetic Regulation of Obesity and Metabolism in Female LH-derived Rats

Abstract

Despite strong evidence that the Metabolic Syndrome (MetS) and its defining features (central obesity, dyslipidemia, hypertension, hyperglycemia) are highly heritable, the genetic etiology is complex and relatively few causative genes are known. For this reason, we employ the Lyon Hypertensive (LH) rat, a well-characterized genetic model of MetS. Previously, we identified a novel gene ( RGD1562963 ) on LH rat chromosome 17 (RNO17) that affects components of MetS, using a combination of genetic mapping and gene network analyses. In this study, frameshift mutations (by CRISPR-Cas9) in exon 2 of RGD1562963 is shown to change resting metabolic rate (RMR) and body composition in LH-derived female rats, measured at 8 and 11 weeks of age, despite no differences in either total body weight or food consumption. RGD1562963 -/- ( RGD -/- ) females have significantly more body fat mass than their wild-type control at 8 weeks of age, measured by nuclear magnetic resonance (NMR) as a percentage of total body weight ( # 8 weeks: WT = 5.08±0.099, n=5; RGD -/- = 6.52±0.260, n=8; *p<.001), and this difference increases by 11 weeks of age (WT = 5.39±0.140, n=5; RGD -/- = 7.81±0.293, n=8, *p<.0001). RMR measurements at 8 weeks showed that both genotypes had identical resting energy expenditure (WT: 0.721±0.033 kcal/hr, n=5; RGD -/- : 0.721±0.021 kcal/hr, n=6) and body weights (WT = 160.5g±6.884, n=5; RGD -/- = 160.7g±4.246, n=8). Though no body weight differences appear by 11 weeks (WT: 196.5g±7.226, n=5; RGD -/- : 196.1g±3.765, n=8), the wild-type females have an unexpected decrease in RMR, while the RMR of RGD -/- females remains high (WT: 0.654±0.005 kcal/hr, n=4; RGD -/- : 0.759±0.014 kcal/hr, n=7, *p<.01). Our studies suggest RGD1562963 is an obesity susceptibility gene. Furthermore, inhibition of this gene at the whole body level is tolerated, and unexpectedly induced increased resting metabolic rate despite increased adiposity, possibly as a protective mechanism. The continued study of this rat model of Metabolic Syndrome has the potential to functionally validate an uncharacterized regulatory gene, and provide novel targets for pharmacological intervention in the treatment of obesity. # all measures are presented as mean±SEM, * RM 2-WAY ANOVA, Sidak’s correction