High-Throughput Screening of Mouse Gene Knockouts Identifies Established and Novel High Body Fat Phenotypes

Abstract

Purpose: 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 Genome5000^TM 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: druggable; gene trapping; homologous recombination; obesity.

Figure 1

High-throughput screen (HTS) normalized %body fat (n%BF) values for individual well-studied KO lines within the distribution of HTS n%BF values for all 3650 individual KO lines maintained on chow diet from weaning. Body composition analyses performed by DXA on 14-week-old mice were used to calculate n%BF for the cohort from each individual KO line. Solid points indicate actual numbers of KO lines within that mean ± 2.5% value of n%BF. Curved line shows the calculated curve. The range for 1 and 2 SD from the population mean is indicated by lines located below the curve, and the mean n%BF value for the HTS cohort from each individual well-studied KO line is indicated by arrows above the curve. Some of these KO lines also had HTS data generated on an independent HFD-fed cohort; these KO lines and their n%BF data from the HFD-fed HTS cohort were: Pyy (101%), Sprk2 (106%), Dkk4 (107%), Htr2c (108%), Tenm3 (110%), Prlhr (111%), Oprm1 (123%), Hdac5 (132%), Dpp8 (134%), Mc4r (159%), Kiss1 (161%), G2e3 (164%), Asnsd1 (167%) and Ksr2 (189%).