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David R Powell,1 Jean-Pierre Revelli,1 Deon D Doree,1 Christopher M DaCosta,1 Urvi Desai,1 Melanie K Shadoan,1 Lawrence Rodriguez,2 Michael Mullens,2 Qi M Yang,1 Zhi-Ming Ding,1 Laura L Kirkpatrick,3 Peter Vogel,1 Brian Zambrowicz,1– 3 Arthur T Sands,1– 3 Kenneth A Platt,3 Gwenn M Hansen,3 Robert Brommage1 1Department of Pharmaceutical Biology, Lexicon Pharmaceuticals, Inc, The Woodlands, TX, USA; 2Department of Information Technology, Lexicon Pharmaceuticals, Inc, The Woodlands, Tx, USA; 3Department of Molecular Biology, Lexicon Pharmaceuticals, Inc, The Woodlands, Tx, USACorrespondence: David R PowellDepartment of Pharmaceutical Biology, Lexicon Pharmaceuticals, Inc, 2445 Technology Forest Boulevard, The Woodlands, Tx, 77381, USATel +1 713 249 3972Fax +1 281 863 8115Email dpowell@lexpharma.comPurpose: Obesity is a major public health problem. Understanding which genes contribute to obesity may better predict individual risk and allow development of new therapies. Because obesity of a mouse gene knockout (KO) line predicts an association of the orthologous human gene with obesity, we reviewed data from the Lexicon Genome5000TM high throughput phenotypic screen (HTS) of mouse gene KOs to identify KO lines with high body fat.Materials and Methods: KO lines were generated using homologous recombination or gene trapping technologies. HTS body composition analyses were performed on adult wild-type and homozygous KO littermate mice from 3758 druggable mouse genes having a human ortholog. Body composition was measured by either DXA or QMR on chow-fed cohorts from all 3758 KO lines and was measured by QMR on independent high fat diet-fed cohorts from 2488 of these KO lines. Where possible, comparisons were made to HTS data from the International Mouse Phenotyping Consortium (IMPC).Results: Body fat data are presented for 75 KO lines. Of 46 KO lines where independent external published and/or IMPC KO lines are reported as obese, 43 had increased body fat. For the remaining 29 novel high body fat KO lines, Ksr2 and G2e3 are supported by data from additional independent KO cohorts, 6 (Asnsd1, Srpk2, Dpp8, Cxxc4, Tenm3 and Kiss1) are supported by data from additional internal cohorts, and the remaining 21 including Tle4, Ak5, Ntm, Tusc3, Ankk1, Mfap3l, Prok2 and Prokr2 were studied with HTS cohorts only.Conclusion: These data support the finding of high body fat in 43 independent external published and/or IMPC KO lines. A novel obese phenotype was identified in 29 additional KO lines, with 27 still lacking the external confirmation now provided for Ksr2 and G2e3 KO mice. Undoubtedly, many mammalian obesity genes remain to be identified and characterized.Keywords: obesity, druggable, homologous recombination, gene trapping

David R Powell, Jason P Gay, Melinda Smith, Nathaniel Wilganowski, Angela Harris, Autumn Holland, Maricela Reyes, Laura Kirkham, Laura L Kirkpatrick, Brian Zambrowicz, Gwenn Hansen, Kenneth A Platt, Isaac van Sligtenhorst, Zhi-Ming Ding, Urvi Desai Metabolism Research, Lexicon Pharmaceuticals, Inc., The Woodlands, TX, USA Abstract: Delta-5 desaturase (D5D) and delta-6 desaturase (D6D), encoded by fatty acid desaturase 1 (FADS1) and FADS2 genes, respectively, are enzymes in the synthetic pathways for w3, w6, and w9 polyunsaturated fatty acids (PUFAs). Although PUFAs appear to be involved in mammalian metabolic pathways, the physiologic effect of isolated D5D deficiency on these pathways is unclear. After generating >4,650 knockouts (KOs) of independent mouse genes and analyzing them in our high-throughput phenotypic screen, we found that Fads1 KO mice were among the leanest of 3,651 chow-fed KO lines analyzed for body composition and were among the most glucose tolerant of 2,489 high-fat-diet-fed KO lines analyzed by oral glucose tolerance test. In confirmatory studies, chow- or high-fat-diet-fed Fads1 KO mice were leaner than wild-type (WT) littermates; when data from multiple cohorts of adult mice were combined, body fat was 38% and 31% lower in Fads1 male and female KO mice, respectively. Fads1 KO mice also had lower glucose and insulin excursions during oral glucose tolerance tests along with lower fasting glucose, insulin, triglyceride, and total cholesterol levels. In additional studies using a vascular injury model, Fads1 KO mice had significantly decreased femoral artery intima/media ratios consistent with a decreased inflammatory response in their arterial wall. Based on this result, we bred Fads1 KO and WT mice onto an ApoE KO background and fed them a Western diet for 14 weeks; in this atherogenic environment, aortic trees of Fads1 KO mice had 40% less atheromatous plaque compared to WT littermates. Importantly, PUFA levels measured in brain and liver phospholipid fractions of Fads1 KO mice were consistent with decreased D5D activity and normal D6D activity. The beneficial metabolic phenotype demonstrated in Fads1 KO mice suggests that selective D5D inhibitors may be useful in the treatment of human obesity, diabetes, and atherosclerotic cardiovascular disease. Keywords: delta-5 desaturase, delta-6 desaturase, obesity, diabetes, atherosclerosis