Experiment
130 polymorphic markers at an average spacing of 10.4 cM were screened in a population of obese (C57BL/6J-Lepob/Lepob x BALB/cJ)F2 male and female animals to identify loci modifying obesity related sterility. C57BL/6J-Lepob/Lepob animals are obese and infertile whereas BALB/cJ animals are lean and fertile. Continuous treatment with leptin is able to alleviate infertility in C57BL/6J-Lepob/Lepob animals. (C57BL/6J-Lepob/Lepob x BALB/cJ)F2 animals were assessed for fertility in the absence of leptin treatment and subjected to full genome scan analysis. Loci on mouse chromosome 1, 3, and 14 were shown to be associated with fertility in obese F2 male mice. Mors1 (modifier of obesity related sterility) mapped to mouse chromosome 1 from 101.5 cM - 106.3 cM in association with fertility (ability to induce pregnancy in lean C57BL/6J females). Mors1 gave a LOD = 5.6 at D1Mit459 and exhibits an additive mode of inheritance. Suggestive loci for fertility mapped to mouse chromosome 3 (LOD = 2.4 at D3Mit316) and mouse chromosome 9 (LOD = 2.7 at D9Mit297). Mors2, a locus associated with testes weight/body weight (TW/BW) ratio mapped to mouse chromosome 3 from 52.5 cM - 71.8 cM with a LOD = 3.4 at D3Mit316. It was observed that fertile obese F2 male animals inherit a greater proportion of BALB/cJ-derived alleles at Mors1 and Mors2 compared to nonfertile obese F2 male animals. Loci associated with absolute testosterone levels, Mors3 and Mors4, mapped to mouse chromosome 14 from 27.5 cM - 30.0 cM and 15.0cM - 27.5 cM, respectively, and exhibit recessive inheritance. Mors3 gives a peak LOD = 3.8 at D14Mit113, and Mors4 gives a peak LOD = 3.4 at D14Mit203. A locus associated with body weight in obese males, Bwob, mapped to mouse chromosome 5 from 34 cM - 68cM with a peak LOD = 5 at D5Mit271 and exhibits recessive inheritance.
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